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Document and Entity Information	9 Months Ended
Document and Entity Information	Sep. 30, 2013
Document and Entity Information
Entity Registrant Name	PTC THERAPEUTICS, INC.
Entity Central Index Key	0001070081
Document Type	S-1/A
Document Period End Date	Sep. 30, 2013
Amendment Flag	true
Amendment Description	Amendment number 1
Pre-Effective Amendment Number	1
Entity Filer Category	Non-accelerated Filer

Balance sheets - USD ($)	Dec. 31, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 2,725,702	$ 28,431,410
Prepaid expenses and other current assets	855,750	3,379,199
Grant and collaboration receivables, net	1,013,813	1,244,128
Total current assets	4,595,265	33,054,737
Fixed assets, net	8,280,037	10,795,507
Deposits and other assets	197,050	297,916
Total assets	13,072,352	44,148,160
Current liabilities:
Accounts payable and accrued expenses	7,023,971	13,049,454
Current portion of long-term debt	4,444,171	7,139,975
Deferred revenue	16,690,747	22,955,901
Total current liabilities	28,158,889	43,145,330
Deferred revenue, less current portion	741,667	16,448,656
Long-term debt, less current portion	438,810	4,549,332
Other long-term liabilities	2,549,719	4,229,617
Total liabilities	31,889,085	68,372,935
Commitments and contingencies (Note 12)
Stockholders' deficit:
Common stock, $0.001 par value. Authorized 216,666 shares; issued and outstanding 1,083 shares at December 31, 2011 and 4,526 shares at December 31, 2012	545	133
Additional paid-in capital	177,583,672	12,007,007
Accumulated deficit	(277,224,718)	(250,611,829)
Total stockholders' (deficit) equity	(99,640,501)	(238,604,689)
Total liabilities, convertible preferred stocks and stockholders' (deficit) equity	13,072,352	44,148,160
Series One convertible preferred stock
Current liabilities:
Preferred stock	62,263,852
Series Two convertible preferred stock
Current liabilities:
Preferred stock	18,182,129
Series Three convertible preferred stock
Current liabilities:
Preferred stock	377,787
Series A-G convertible preferred stock
Current liabilities:
Preferred stock		214,379,914
Series A convertible preferred stock
Current liabilities:
Preferred stock	0	750,000
Series B convertible preferred stock
Current liabilities:
Preferred stock	0	364,524
Series C convertible preferred stock
Current liabilities:
Preferred stock	0	14,117,089
Series D convertible preferred stock
Current liabilities:
Preferred stock	0	39,282,460
Series E convertible preferred stock
Current liabilities:
Preferred stock	0	49,048,047
Series E-2 convertible preferred stock
Current liabilities:
Preferred stock	0	26,509,451
Series F convertible preferred stock
Current liabilities:
Preferred stock	0	10,000,000
Series F-2 convertible preferred stock
Current liabilities:
Preferred stock	0	24,114,456
Series G convertible preferred stock
Current liabilities:
Preferred stock	$ 0	$ 50,193,887

Balance sheets (Parenthetical)	Dec. 31, 2011 USD ($) $ / shares shares
Common stock, par value (in dollars per share) \| $ / shares	$ 0.001
Common stock, Authorized shares	216,666
Common stock, issued shares	1,083
Common stock, outstanding shares	1,083
Preferred stock
Preferred stock, par value (in dollars per share) \| $ / shares	$ 0.001
Preferred stock, designated shares	156,995,095
Series A-G convertible preferred stock
Preferred stock, issued shares	154,728,267
Series A convertible preferred stock
Preferred stock, designated shares	750,000
Preferred stock, issued shares	750,000
Preferred stock, outstanding shares	750,000
Preferred stock, liquidation preference \| $	$ 750,000
Series B convertible preferred stock
Preferred stock, designated shares	187,500
Preferred stock, issued shares	187,500
Preferred stock, outstanding shares	187,500
Preferred stock, liquidation preference \| $	$ 375,000
Series C convertible preferred stock
Preferred stock, designated shares	6,295,000
Preferred stock, issued shares	6,000,000
Preferred stock, outstanding shares	6,000,000
Preferred stock, liquidation preference \| $	$ 15,000,000
Series D convertible preferred stock
Preferred stock, designated shares	13,769,935
Preferred stock, issued shares	13,095,769
Preferred stock, outstanding shares	13,095,769
Preferred stock, liquidation preference \| $	$ 42,561,249
Series E convertible preferred stock
Preferred stock, designated shares	126,735,022
Preferred stock, issued shares	125,740,607
Preferred stock, outstanding shares	125,740,607
Preferred stock, liquidation preference \| $	$ 49,999,998
Series E-2 convertible preferred stock
Preferred stock, designated shares	3,670,138
Preferred stock, issued shares	3,670,138
Preferred stock, outstanding shares	3,670,138
Preferred stock, liquidation preference \| $	$ 26,645,187
Series F convertible preferred stock
Preferred stock, designated shares	675,000
Preferred stock, issued shares	625,000
Preferred stock, outstanding shares	625,000
Preferred stock, liquidation preference \| $	$ 10,000,000
Series F-2 convertible preferred stock
Preferred stock, designated shares	1,612,500
Preferred stock, issued shares	1,515,503
Preferred stock, outstanding shares	1,515,503
Preferred stock, liquidation preference \| $	$ 24,248,048
Series G convertible preferred stock
Preferred stock, designated shares	3,300,000
Preferred stock, issued shares	3,143,750
Preferred stock, outstanding shares	3,143,750
Preferred stock, liquidation preference \| $	$ 50,300,000

Statements of operations - USD ($)	12 Months Ended
Statements of operations - USD ($)	Dec. 31, 2012	Dec. 31, 2011
Revenues:
Collaboration revenue	$ 28,779,078	$ 98,960,851
Grant revenue	5,166,985	6,451,296
Total revenues and non-cash cancellation revenue	33,946,063	105,412,147
Operating expenses:
Research and development	46,138,868	58,677,081
General and administrative	14,615,376	16,153,069
Total operating expenses	60,754,244	74,830,150
Loss from operations	(26,808,181)	30,581,997
Interest expense, net	(1,209,577)	(2,444,417)
Other income, net	1,782,656	461,358
Income (loss) from operations before tax benefit	(26,235,102)	28,598,938
Tax benefit		2,305,576
Net loss	(26,235,102)	30,904,514
Gain on exchange of convertible preferred stock in connection with recapitalization	159,954,069
Less beneficial conversion charge	(377,787)
Net (loss) income attributable to common stockholders	$ 133,341,180	$ 30,904,514
Net income attributable to common stockholders per share:
Basic (in dollars per share)	$ 219.76	$ 23.95
Diluted (in dollars per share)	$ 42.50	$ 4.55
Weighted-average shares outstanding:
Basic (in shares)	3,328	1,089
Diluted (in shares)	17,205	5,729
Pro forma net income per share applicable to common stockholders-(unaudited) (in dollars per share)	$ 9.40
Pro forma weighted-average number of shares outstanding (unaudited)	14,188,161

Statements of comprehensive income (loss) - USD ($)	3 Months Ended											9 Months Ended		12 Months Ended
Statements of comprehensive income (loss) - USD ($)	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Statements of comprehensive loss
Net income (loss)	$ (4,416,499)	$ (14,586,578)	$ (14,684,535)	$ (6,272,044)	$ (7,297,125)	$ (6,068,072)	$ (6,597,861)	$ (5,764,646)	$ 67,608,165	$ (15,388,398)	$ (15,550,607)	$ (33,687,612)	$ (19,963,058)	$ (26,235,102)	$ 30,904,514
Other comprehensive income (loss):
Unrealized loss on investments												(40,467)			(3,606)
Comprehensive loss												$ (33,728,079)	$ (19,963,058)	$ (26,235,102)	$ 30,900,908

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Net Income
-URI http://asc.fasb.org/extlink&oid=6518256

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.19)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.18)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.22)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Other Comprehensive Income
-URI http://asc.fasb.org/extlink&oid=6519514

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e565-108580

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 19
-Article 5

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Paragraph 20
-Article 9

+ Details

Statements of convertible preferred stock and changes in stockholders' deficit - USD ($)	Total	Common stock	Additional paid-in capital	Accumulated other comprehensive income	Accumulated deficit	Series A-G convertible preferred stock	Series one-three convertible preferred stock
Balance, beginning of period at Dec. 31, 2010						$ 214,379,914
Balance, beginning of period (in shares) at Dec. 31, 2010						154,728,267
Balance, end of period at Dec. 31, 2011						$ 214,379,914
Balance, end of period (in shares) at Dec. 31, 2011						154,728,267
Balance at Dec. 31, 2010	$ (272,328,123)	$ 131	$ 9,184,483	$ 3,606	$ (281,516,343)
Balance (in shares) at Dec. 31, 2010		130,586
Increase (Decrease) in Stockholders' Equity
Exercise of stock options	5,889	$ 2	5,887
Exercise of stock options (in shares)		1,536
Share-based compensation expense	2,816,637		2,816,637
Net loss	30,904,514				30,904,514
Unrealized loss on investments	(3,606)			$ (3,606)
Balance at Dec. 31, 2011	(238,604,689)	$ 133	12,007,007		(250,611,829)
Balance (in shares) at Dec. 31, 2011		132,122
Increase (decrease) in temporary equity
Conversion of Series E and E-2 convertible preferred stock to common stock						$ (2,956,829)
Conversion of Series E and E-2 convertible preferred stock to common stock (in shares)						(5,167,365)
Issuance of Series One convertible preferred stock, exchange of Series A-G convertible preferred stock for Series Two and Series Three convertible preferred stock						$ (211,423,085)	$ 80,823,768
Issuance of Series One convertible preferred stock, exchange of Series A-G convertible preferred stock for Series Two and Series Three convertible preferred stock (in shares)						(149,560,902)	15,038,259
Balance, end of period at Dec. 31, 2012							$ 80,823,768
Balance, end of period (in shares) at Dec. 31, 2012							15,038,259
Increase (Decrease) in Stockholders' Equity
Conversion of Series E and E-2 convertible preferred stock to common stock	2,956,829	$ 412	2,956,417
Conversion of Series E and E-2 convertible preferred stock to common stock (in shares)		413,223
Issuance of Series One convertible preferred stock, exchange of Series A-G convertible preferred stock for Series Two and Series Three convertible preferred stock	159,954,069		159,954,069
Beneficial conversion charge			377,787		(377,787)
Share-based compensation expense	2,288,392		2,288,392
Net loss	(26,235,102)				(26,235,102)
Balance at Dec. 31, 2012	(99,640,501)	$ 545	$ 177,583,672		$ (277,224,718)
Balance (in shares) at Dec. 31, 2012		545,345
Increase (Decrease) in Stockholders' Equity
Net loss	(33,687,612)
Unrealized loss on investments	(40,467)
Balance at Sep. 30, 2013	$ 151,032,513

Statements of cash flows	12 Months Ended
Statements of cash flows	Dec. 31, 2011 USD ($)
Cash flows from operating activities
Net income (loss)	$ 30,904,514
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation	2,871,200
Change in valuation of warrant liability	(461,947)
Noncash interest expense	416,612
Share-based compensation expense	2,816,637
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(1,355,123)
Grant and collaboration receivables	2,052,550
Deposits and other assets	214,345
Accounts payable and accrued expenses	(3,159,711)
Other long-term liabilities	(67,151)
Deferred revenue	(54,998,713)
Net cash used in operating activities	(20,766,787)
Cash flows from investing activities
Purchases of fixed assets	(165,116)
Purchases of investments	(2,019,163)
Maturities of investments	29,887,327
Net cash used in investing activities	27,703,048
Cash flows from financing activities
Payments on long-term debt	(7,185,610)
Proceeds from issuance of common stock	5,889
Net cash provided by financing activities	(7,179,721)
Net (decrease) increase in cash and cash equivalents	(243,460)
Cash and cash equivalents, beginning of period	28,674,870
Cash and cash equivalents, end of period	28,431,410
Supplemental disclosure of cash information
Cash paid for interest	2,486,682
Supplemental disclosures of noncash information related to investing and financing activities
Change in unrealized loss on investments	$ (3,606)

The Company	9 Months Ended	12 Months Ended
The Company	Sep. 30, 2013	Dec. 31, 2012
The Company
The Company	1. The Company PTC Therapeutics, Inc. (the Company or PTC) was incorporated as a Delaware corporation on March 31, 1998. The Company is a biopharmaceutical company focused on the discovery and development of orally administered, proprietary small-molecule drugs that target post-transcriptional control processes. The Company has devoted substantially all of its efforts to research and development, including clinical trials. The Company has not completed development of any drugs. The Company has not generated product revenue to date and is subject to a number of risks similar to those of other early stage companies, including dependence on key individuals, the difficulties inherent in the development of commercially usable products, the potential need to obtain additional capital necessary to fund the development of its products, and competition from other companies. As of September 30, 2013, the Company had an accumulated deficit of approximately $310.9 million. The Company has financed its operations to date primarily through the issuance and sale of its common stock in its initial public offering (see note 7 below), private placements of its convertible preferred stock, collaborations, bank debt, convertible debt financings, grant funding and clinical trial support from governmental and philanthropic organizations and patient advocacy groups in the disease areas addressed by the Company's product candidates. The Company believes that its existing cash, cash equivalents, including the Company's net proceeds from its initial public offering of common stock, and marketable securities provide for sufficient resources to fund its currently planned operations through the fourth quarter of 2015.	1. The Company PTC Therapeutics, Inc. (the Company or PTC) was incorporated as a Delaware corporation on March 31, 1998. The Company is a biopharmaceutical company focused on the discovery and development of orally administered, proprietary small-molecule drugs that target post-transcriptional control processes. The Company has devoted substantially all of its efforts to research and development, including clinical trials. The Company has not completed development of any drugs. The Company has not generated product revenue to date and is subject to a number of risks similar to those of other early stage companies, including dependence on key individuals, the difficulties inherent in the development of commercially usable products, the potential need to obtain additional capital necessary to fund the development of its products, and competition from other companies. As of December 31, 2012, the Company had an accumulated deficit of approximately $277.2 million. The Company has financed its operations to date primarily through private placements of its convertible preferred stock, collaborations, bank debt, convertible debt financings, grant funding and clinical trial support. The Company will need to obtain additional funding in connection with its ongoing operations. Additional financing may not be available to the Company. If the Company is unable to raise capital when needed or on attractive terms, the Company could be forced to delay, reduce or eliminate its research and development programs or any future commercialization efforts. As more fully described in Note 7, the Company completed a recapitalization of its outstanding convertible preferred stock in 2012 to enable the Company to raise additional capital. Use of estimates The preparation of financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Summary of significant accounting policies

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Summary of significant accounting policies

Summary of significant accounting policies

2. Summary of significant accounting policies

The Company's complete listing of significant accounting policies are described in note 2 of the notes to the Company's audited financial statements as of December 31, 2012 included in the final prospectus dated June 19, 2013 related to the Company's initial public offering.

Unaudited pro forma presentation

Unaudited pro forma net loss per share is computed using the weighted-average number of common shares outstanding after giving effect to the pro forma effect of the conversion of all convertible preferred stock during the period ended September 30, 2013 into shares of the Company's common stock as if such conversion had occurred at the beginning of the period presented.

Basis of presentation

The accompanying financial information as of September 30, 2013 and for the nine months ended September 30, 2012 and 2013 has been prepared by the Company, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). Certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles in the United States (GAAP) have been condensed or omitted pursuant to such rules and regulations. These interim financial statements should be read in conjunction with the Company's audited financial statements as of December 31, 2012 and notes thereto included in the final prospectus related to the Company's initial public offering.

In the opinion of management, the unaudited financial information as of September 30, 2013 and the nine months ended September 30, 2012 and 2013 reflects all adjustments, which are normal recurring adjustments, necessary to present a fair statement of financial position, results of operations and cash flows. The results of operations for the nine month period ended September 30, 2013 is not necessarily indicative of the results to be expected for the year ended December 31, 2013 or for any other interim period or for any other future year.

Use of estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Reverse stock split

On March 7, 2013, the Company effected a one-for-120 reverse stock split of its common stock, pursuant to which each 120 shares of the Company's outstanding common stock were reclassified and combined into one share of common stock. All common stock share and per share references in the financial statements and notes thereto have been restated to reflect the reverse stock split on a retroactive basis.

Marketable securities

Management determines the classification of marketable securities at the time of purchase and reevaluates such designation as of each balance sheet date. Marketable securities are classified as available-for-sale and carried at fair value, with any unrealized gain or loss recorded as a separate component of stockholders' (deficit) equity.

Revenue recognition

The Company recognizes revenue when amounts are realized or realizable and earned. Revenue is considered realizable and earned when the following criteria are met: (1) persuasive evidence of an arrangement exists; (2) delivery has occurred or services have been rendered; (3) the price is fixed or determinable; and (4) collection of the amounts due are reasonably assured.

The Company's revenue is generated primarily through collaborative research and development and licensing agreements and grants.

The terms of these agreements typically include payments to the Company of one or more of the following: nonrefundable, upfront license fees; milestone payments; research funding and royalties on future product sales. In addition, the Company generates service revenue through agreements that generally provide for fees for research and development services and may include additional payments upon achievement of specified events.

For existing collaborations entered into prior to the adoption in 2011 of the revised multiple element revenue recognition guidance described below, the Company recognized revenue consistent with the approach established at the inception of each arrangement. For these existing collaborations, where the Company has continuing involvement, the Company recorded nonrefundable, upfront fees as deferred revenue and recognizes revenue on a straight-line basis as collaboration revenue over the expected performance period.

For new collaborations or for material modifications made to existing collaborations, in 2011 and thereafter, the Company adopted the updated multiple element revenue recognition guidance. Under this guidance, all non-contingent arrangement consideration is allocated to the identified units of accounting based on their relative selling price at inception of the collaboration arrangement. The Company derives the selling price using a combination of internal subjective and available external objective information, such as comparable transactions. The Company recognizes revenue commensurate with delivery, such as in the case with delivery of a license, or ratably over the course of a service period, as appropriate, such as in the case of ongoing research and development activities.

The Company evaluates all contingent consideration earned, such as a milestone payment, using the criteria as provided by the Financial Accounting Standards Board (FASB) guidance on the milestone method of revenue recognition. At the inception of a collaboration arrangement, the Company evaluates if milestone payments are substantive. The criteria requires that (1) the Company determines if the milestone is commensurate with either its performance to achieve the milestone or the enhancement of value resulting from its activities to achieve the milestone; (2) the milestone be related to past performance; and (3) the milestone be reasonable relative to all deliverable and payment terms of the collaboration arrangement. If these criteria are met then the contingent milestones can be considered as substantive milestones and will be recognized as revenue in the period that the milestone is achieved.

The Company recognizes royalties as earned in accordance with the terms of various research and collaboration agreements. If not substantive, the contingent consideration is allocated to the existing units of accounting based on relative selling price and recognized following the same basis previously established for the associated unit of accounting. The Company recognizes revenue for reimbursements of research and development costs under collaboration agreements as the services are performed. The Company records these reimbursements as revenue and not as a reduction of research and development expenses as the Company has the risks and rewards as the principal in the research and development activities.

Fair value of financial instruments

The Company follows the fair value measurement rules, which provides guidance on the use of fair value in accounting and disclosure for assets and liabilities when such accounting and disclosure is called for by other accounting literature. These rules establish a fair value hierarchy for inputs to be used to measure fair value of financial assets and liabilities. This hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three levels: Level 1 (highest priority), Level 2, and Level 3 (lowest priority).

•: Level 1—Unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the balance sheet date.
•: Level 2—Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability

(i.e., interest rates, yield curves, etc.), and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs).

•: Level 3—Inputs are unobservable and reflect the Company's assumptions as to what market participants would use in pricing the asset or liability. The Company develops these inputs based on the best information available.

Cash equivalents are reflected in the accompanying financial statements at fair value. The carrying amount of grant and collaboration receivables, accounts payable and accrued expenses, and debt approximates fair value due to the short-term nature of those instruments.

Warrant liability

Warrants to purchase the Company's common stock with nonstandard antidilution provisions and preferred stock that include a put feature, regardless of the probability or likelihood that may conditionally obligate the issuer to ultimately transfer assets, are classified as liabilities and are recorded at their estimated fair value at each reporting period. Any change in fair value of these warrants is recorded as gain (loss) on warrant valuation each reporting period in Other income (expense), net on the Company's statement of operations.

Share-based compensation

The Company measures the cost of employee services received in exchange for an award of equity instruments based on the grant date fair value of the award. For service type awards, share-based compensation expense is recognized on a straight-line basis over the period during which the employee is required to provide service in exchange for the entire award. For awards that vest or begin vesting upon achievement of a performance condition, the Company estimates the likelihood of satisfaction of the performance condition and recognizes compensation expense when achievement of the performance condition is deemed probable using an accelerated attribution model.

The fair value of options is calculated using the Black-Scholes option pricing model to determine the fair value of stock options on the date of grant based on key assumptions, such as expected volatility and expected term. As a new public company, the Company does not have sufficient history to estimate the volatility of its common stock price or the expected life of the options. The Company calculates expected volatility based on reported data for similar publicly traded companies for which historical information is available and will continue to do so until the historical volatility of its common stock is sufficient to measure expected volatility for future option grants.

2. Summary of significant accounting policies

Unaudited pro forma presentation

Unaudited pro forma net income per share is computed using the weighted-average number of common shares outstanding after giving effect to the pro forma effect of the conversion of all convertible preferred stock during the year ended December 31, 2012 into shares of the Company's common stock as if such conversion had occurred at the beginning of the period presented.

Segment and geographic information

Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision making group, in deciding how to allocate resources and in assessing performance. The Company views its operations and manages its business in one operating segment.

Accounting changes

Effective January 1, 2012, an update to an accounting standard was issued that requires that all nonowner changes in stockholders' equity be presented either in a single continuous statement of comprehensive income or in two separate but consecutive statements. This update was applied retrospectively. The Company adopted this pronouncement and elected to present a separate statement of comprehensive income. The updated standard does not change the items that must be reported in comprehensive income, how such items are measure, or when they must be reclassified to net income.

Cash equivalents

The Company considers all highly liquid investments with a maturity of 90 days or less at the time of purchase to be cash equivalents. Cash equivalents are carried at cost which approximates fair value due to their short-term nature.

Fixed assets

Fixed assets are stated at cost. Depreciation is computed starting when the asset is placed into service on a straight-line basis over the estimated useful life of the related asset as follows:



Leasehold improvements		Lesser of useful life or lease term
Computer equipment and software		3 years
Furniture, fixtures, and lab equipment		3 to 7 years

Grant and collaboration receivables

The Company records receivables in conjunction with grant and collaboration agreements when the services have been performed. The Company will record an allowance for bad debt if receivables are anticipated to be uncollectible. There is no indication that any receivables are uncollectible as of December 31, 2011 and 2012. Write-offs of receivables have historically been insignificant.

Concentration of risks

The Company has no significant off-balance-sheet risk or credit risk concentrations. The Company maintains its cash and cash equivalents with various financial institutions. The Company maintains cash accounts that may at times exceed the federally insured limit; however, it has not experienced and does not anticipate experiencing any credit losses from maintaining cash accounts in excess of such limits.

The Company's revenues from its two largest collaboration partners and its largest grant as a percentage of total revenues were 85%, 8%, and 3%, respectively, for 2011 and were 67%, 11%, and 9%, respectively, for 2012.

Reverse stock split

As a result of the one-for-120 reverse stock split that was effected on March 7, 2013, each 120 shares of the Company's outstanding common stock were reclassified and combined into one share of common stock. All references to common stock have been restated to reflect the reverse stock split on a retroactive basis.

Deferred rent

The Company has an operating lease for office space. Rent expense is recorded on a straight-line basis over the initial lease term. The difference between the actual cash paid and the straight-line rent expense is recorded as deferred rent. Leasehold improvements made related to this lease, subsequent to its inception, are amortized over the remaining lease term.

Revenue recognition

The Company's revenue is generated primarily through collaborative research and development and licensing agreements and grants.

For new collaborations or for material modifications made to existing collaborations, in 2011 and thereafter, the Company adopted the updated multiple element revenue recognition guidance. Under this new guidance, all non-contingent arrangement consideration is allocated to the identified units of accounting based on their relative selling price at inception of the collaboration arrangement. The Company derives the selling price using a combination of internal subjective and available external objective information, such as comparable transactions. The Company recognizes revenue commensurate with delivery, such as in the case with delivery of a license, or ratably over the course of a service period, as appropriate, such as in the case of ongoing research and development activities.

The Company evaluates all contingent consideration earned, such as a milestone payment, using the criteria as provided by the Financial Accounting Standards Board (FASB), guidance on the milestone method of revenue recognition. At the inception of a collaboration arrangement, the Company evaluates if milestone payments are substantive. The criteria requires that (1) the Company determines if the milestone is commensurate with either its performance to achieve the milestone or the enhancement of value resulting from our activities to achieve the milestone; (2) the milestone be related to past performance; and (3) the milestone be reasonable relative to all deliverable and payment terms of the collaboration arrangement. If these criteria are met then the contingent milestones can be considered as substantive milestones and will be recognized as revenue in the period that the milestone is achieved. The Company recognizes royalties as earned in accordance with the terms of various research and collaboration agreements. If not substantive, the contingent consideration is allocated to the existing units of accounting based on relative selling price and recognized following the same basis previously established for the associated unit of accounting.

The Company recognizes revenue for reimbursements of research and development costs under collaboration agreements as the services are performed. The Company records these reimbursements as revenue and not as a reduction of research and development expenses as the Company has the risks and rewards as the principal in the research and development activities.

Research and development costs

Research and development expenses include the clinical development costs associated with the Company's product development programs and research and development costs associated with the Company's discovery programs. These expenses include internal research and development costs and the costs of research and development conducted on behalf of the Company by third parties, including sponsored university-based research agreements and clinical study vendors. All research and development costs are expensed as incurred. Costs incurred in obtaining technology licenses are charged immediately to research and development expense if the technology licensed has not reached technological feasibility and has no alternative future uses.

Nonrefundable advance payments made for goods and services that will be used in future research and development activities are deferred if the contracted party has not yet performed the related activities. The amount deferred is then recognized as expense when the research and development activities are performed. The Company has deferred research and development advance payments of approximately $245,000 and $228,000 as of December 31, 2011 and 2012, respectively.

Fair value of financial instruments

The Company follows the fair value measurement rules, which provides guidance on the use of fair value in accounting and disclosure for assets and liabilities when such accounting and disclosure is called for by other accounting literature. These rules establishes a fair value hierarchy for inputs to be used to measure fair value of financial assets and liabilities. This hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three levels: Level 1 (highest priority), Level 2, and Level 3 (lowest priority).

•: Level 1—Unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the balance sheet date.
•: Level 2—Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (i.e., interest rates, yield curves, etc.), and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs).
•: Level 3—Inputs are unobservable and reflect the Company's assumptions as to what market participants would use in pricing the asset or liability. The Company develops these inputs based on the best information available.

Cash equivalents and investments are reflected in the accompanying financial statements at fair value. The carrying amount of grant and collaboration receivables and accounts payable and accrued expenses approximates fair value due to the short-term nature of those instruments.

Beneficial conversion

When the Company issues a debt or an equity security that is convertible into common stock at a discount from the fair value of the common stock at the date the debt or equity security counterparty is legally committed to purchase such a security (Commitment Date), a beneficial conversion charge is measured and recorded on the Commitment Date for the difference between the fair value of the Company's common stock and the effective conversion price of the convertible debt or equity security. If the intrinsic value of the beneficial conversion feature is greater than the proceeds allocated to the convertible debt or equity security, the amount of the discount assigned to the beneficial conversion feature is limited to the amount of the proceeds allocated to the convertible debt or equity security.

The amount allocated to the beneficial conversion feature is presented as a discount or reduction to the related debt security or as an immediate charge to earnings available to common shareholders for convertible preferred stock instruments that are convertible by the shareholders at any time. In connection with the Company's recapitalization of its outstanding convertible preferred stock in 2012, the Company recorded a beneficial conversion charge representing the difference between the effective conversion price and the fair value of the Company's common stock as of the Commitment Date. Because the intrinsic value was in excess of the proceeds allocated to the Company's new Series Three convertible preferred stock; the beneficial conversion charge was limited to the allocated proceeds of approximately $377,000.

Warrant liability

Warrants to purchase the Company's common stock with nonstandard antidilution provisions and preferred stock that include a put feature, regardless of the probability or likelihood that may conditionally obligate the issuer to ultimately transfer assets, are classified as liabilities and are recorded at their estimated fair value at each reporting period. Any change in fair value of these warrants is recorded as gain/(loss) on warrant valuation each reporting period in Other income on the Company's statement of operations.

Impairment of long-lived assets

The Company monitors its long-lived assets for indicators of impairment. If such indicators are present, the Company assesses the recoverability of affected assets by determining whether the carrying value of such assets is less than the sum of the undiscounted future cash flows of the assets. If such assets are found not to be recoverable, the Company measures the amount of such impairment by comparing the carrying value of the assets to the fair value of the assets, with the fair value generally determined based on the present value of the expected future cash flows associated with the assets. Although current and historical negative cash flows are indicators of impairment, management believes the future cash flows to be received from the long-lived assets and the potential success of the Company's research programs will exceed the assets' carrying value, and accordingly, the Company believes that no impairment of long-lived assets exists as of December 31, 2012.

Share-based compensation

The Company measures the cost of employee services received in exchange for an award of equity instruments based on the grant date fair value of the award. That cost is recognized on a straight-line basis over the period during which the employee is required to provide service in exchange for the entire award.

The fair value of options is calculated using the Black-Scholes option pricing model to determine the fair value of stock options on the date of grant based on key assumptions such as stock price, expected volatility and expected term. The Company's estimates of these assumptions are primarily based on third-party valuations, historical data, peer company data and judgment regarding future trends and factors.

The Company utilized various valuation methodologies in accordance with the framework of the 2004 American Institute of Certified Public Accountants Technical Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation, to estimate the fair value of its stock. The methodologies included an option pricing method to estimate the Company's underlying equity value, and a methodology that determined an estimated value under an initial public offering (IPO) scenario and a sale scenario based upon an assessment of the probability of occurrence of each scenario. Each valuation methodology includes estimates and assumptions that require the Company's judgment. These estimates include assumptions regarding future performance, including the completion of clinical trials and the time to complete an IPO or sale of the Company. As with any valuation, significant changes to the key assumptions used in the valuations could result in different fair values of common stock at each valuation date.

Income taxes

Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and net operating loss and credit carryforwards. Deferred tax assets and liabilities are measured at rates expected to apply to taxable income in the years in which those temporary differences and carryforwards are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the statement of operations in the period that includes the enactment date. A valuation allowance is recorded when it is not more likely than not that all or a portion of the net deferred tax assets will be realized.

Net income per share

Basic net income per share is calculated by dividing the net income attributable to common stockholders by the weighted average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted net income per share is calculated by dividing the net income attributable to common stockholders by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method and the if-converted method. Dilutive common stock equivalents are comprised of convertible preferred stock and options outstanding under the Company's stock option plans.

Fair value of financial instruments and investments

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Fair value of financial instruments and marketable securities

Fair value of financial instruments and investments

3. Fair value of financial instruments and marketable securities

Fair value of certain marketable securities is based upon market prices using quoted prices in active markets for identical assets quoted on the last day of the period. In establishing the estimated fair value of the remaining investments, the Company used the fair value as determined by its investment advisors using observable inputs other than quoted prices.

The Company reviews its investments on a periodic basis for other-than-temporary impairments. This review is subjective, as it requires management to evaluate whether an event or change in circumstances has occurred in that period that may have a significant adverse effect on the fair value of the investment.

The following represents the fair value using the hierarchy described in Note 2 for the Company's financial assets that are required to be measured at fair value on a recurring basis as of December 31, 2012 and September 30, 2013:

	December 31, 2012


	Total		Quoted prices in active markets for identical assets (level 1)		Significant other observable inputs (level 2)		Significant unobservable inputs (level 3)

Warrant liability	$	95,661	$	—	$	—	$	95,661

	September 30, 2013


	Total		Quoted prices in active markets for identical assets (level 1)		Significant other observable inputs (level 2)		Significant unobservable inputs (level 3)

Marketable securities	$	133,182,565	$	—	$	133,182,565	$	—
Warrant liability		98,819		—		—		98,819

The following is a summary of marketable securities accounted for as available-for-sale securities at September 30, 2013:

	September 30, 2013


			Gross Unrealized
	Amortized Cost		Gross Unrealized					Fair Value
	Amortized Cost		Gains		Losses			Fair Value

Commercial paper	$	24,978,703	$	20,527	$	—		$	24,999,230
U.S. corporate debt securities		108,244,329		19,642		(80,636	)		108,183,335

	$	133,223,032	$	40,169	$	(80,636	)	$	133,182,565

At September 30, 2013, the Company held securities with an unrealized loss position that were not considered to be other-than-temporarily impaired as the Company has the ability to hold such investments until recovery of their fair value.

Marketable securities on the balance sheet at September 30, 2013 mature as follows:

	September 30, 2013


	Less than 12 Months		More than 12 Months

Commercial paper	$	24,999,230	$	—
U.S. corporate debt securities		57,824,657		50,358,678

Total Marketable securities	$	82,823,887	$	50,358,678

There were no marketable securities as of December 31, 2012.

Level 3 valuation

The warrant liability is classified in Other long-term liabilities on the Company's balance sheet. The warrant liability is marked-to-market each reporting period with the change in fair value recorded as a gain or loss within Other income (expense), net on the Company's statement of operations until the warrants are exercised, expire or other facts and circumstances lead the warrant liability to be reclassified as an equity instrument. The fair value of the warrant liability is determined at each reporting period by utilizing the Black-Scholes option pricing model.

The table presented below is a summary of changes in the fair value of the Company's Level 3 valuation for warrant liability for the period ended September 30, 2013:

	Level 3 assets



Beginning balance as of December 31, 2012	$	95,661
Warrants issued in connection with convertible promissory notes		6,000,000
Deemed dividend		18,248,768
Exercise of warrants issued in connection with convertible promissory notes		(24,248,765	)
Change in fair value of warrant liability		3,155

Ending balance as of September 30, 2013	$	98,819

Fair value of the warrant liability is estimated using an option-pricing model, which includes variables such as the expected volatility based on guideline public companies, the stock fair value, and the estimated time to a liquidity event. The significant assumptions used in preparing the option pricing model for valuing the Company's warrants as of December 31, 2012 include (i) volatility (87%), (ii) risk free interest rate (0.16%-1.18%), (iii) strike price ($16), (iv) fair value of preferred shares ($2.35), and (v) expected life (1-7 years). The significant assumptions used in preparing the option pricing model for valuing the Company's warrants as of September 30, 2013 include (i) volatility (69-87%), (ii) risk free interest rate (0.02%-1.705%), (iii) strike price ($128), (iv) fair value of common shares ($21.46), and (v) expected life (.22-5.98 years). See Note 7 for a description of the warrants issued in connection with the convertible notes.

3. Fair value of financial instruments and investments

Fair value of certain investments is based upon market prices using quoted prices in active markets for identical assets quoted on the last day of the year. In establishing the estimated fair value of the remaining investments, the Company used the fair value as determined by its investment advisors using observable inputs other than quoted prices.

	December 31, 2011


	Total		Quoted prices in active markets for identical assets (level 1)	Significant other observable inputs (level 2)	Significant unobservable inputs (level 3)

Warrant liability	$	1,878,316	$—	$—	$1,878,316

	December 31, 2012


	Total		Quoted prices in active markets for identical assets (level 1)	Significant other observable inputs (level 2)	Significant unobservable inputs (level 3)

Warrant liability	$	95,661	$—	$—	$95,661

Level 3 valuation

The warrant liability is classified in Other long-term liabilities on the Company's balance sheet. The warrant liability is marked-to-market each reporting period with the change in fair value recorded as a gain or loss within Other income on the Company's statement of operations until the warrants are exercised, expire or other facts and circumstances lead the warrant liability to be reclassified as an equity instrument. The fair value of the warrant liability is determined at each reporting period by utilizing the Black-Scholes option pricing model.

The table presented below is a summary of changes in the fair value of the Company's Level 3 valuation for warrant liability for the years ended December 31, 2011 and 2012:

	Level 3 assets



Beginning balance January 1, 2011	$	2,340,263
Change in fair value of warrant liability		(461,947	)

Ending balance as of December 31, 2011		1,878,316
Change in fair value of warrant liability		(1,782,655	)

Ending balance as of December 31, 2012	$	95,661

Fair value of the warrant liability is estimated using an option-pricing model, which includes variables such as the expected volatility based on guideline public companies, the preferred stock value, and the estimated time to a liquidity event. The significant assumptions used in preparing the option pricing model for valuing the Company's warrants as of December 31, 2011 include (i) volatility (88%), (ii) risk free interest rate (0.25%-1.62%), (iii) strike price ($7.26-$16.00), (iv) fair value of preferred shares ($16) and (v) expected life (2-8 years). The significant assumptions used in preparing the option pricing model for valuing the Company's warrants as of December 31, 2012 include (i) volatility (87%), (ii) risk free interest rate (0.16%-1.18%), (iii) strike price ($16), (iv) fair value of preferred shares ($2.35) and (v) expected life (1-7 years). The fair value of the preferred shares declined significantly due to the recapitalization of the Company's outstanding convertible preferred stock in June 2012 as described in Note 7.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Fixed assets

12 Months Ended

Dec. 31, 2012

Fixed assets

Fixed assets

4. Fixed assets

Fixed assets, net were as follows at December 31, 2011 and 2012:

	December 31,


	2011			2012

Leasehold improvements	$	12,473,836		$	12,473,836
Computer equipment and software		2,082,638			2,118,713
Furniture, fixtures, and lab equipment		13,781,118			13,969,758
Assets not yet placed in service		40,186			4,152

		28,377,778			28,566,459
Less accumulated depreciation and amortization		(17,582,271	)		(20,286,422	)

	$	10,795,507		$	8,280,037

Depreciation expense was approximately $2,871,000 and $2,704,000 for the years ended December 31, 2011 and 2012, respectively.

Accounts payable and accrued expenses

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Accounts payable and accrued expenses

Accounts payable and accrued expenses

5. Accounts payable and accrued expenses

Accounts payable and accrued expenses at December 31, 2012 and September 30, 2013 consist of the following:

	December 31, 2012		September 30, 2013



Employee compensation, benefits, and related accruals	$	3,096,475	$	3,659,084
Consulting and contracted research		2,515,678		3,556,350
Professional fees		559,228		1,532,458
Accounts payable		621,591		1,017,122
Other		230,999		440,479

	$	7,023,971	$	10,205,493

5. Accounts payable and accrued expenses

Accounts payable and accrued expenses at December 31, 2011 and 2012 consist of the following:

	December 31,


	2011		2012

Employee compensation, benefits, and related accruals	$	3,492,170	$	3,096,475
Consulting and contracted research		6,749,272		2,515,678
Professional fees		492,811		559,228
Accounts payable		1,878,109		621,591
Other		437,092		230,999

	$	13,049,454	$	7,023,971

Long-term debt

12 Months Ended

Dec. 31, 2012

Debt

Long-term debt

6. Long-term debt

In May 2009, the Company entered into a capital lease for a laboratory instrument. This lease carries an implied interest rate of 8.2% and is payable in fixed monthly installments. As of December 31, 2011 and 2012, the Company had approximately $314,000 and $187,000 of remaining principal, respectively, which approximates the fair value.

In September 2009, the Company entered into a $25,000,000 secured debt facility with a syndicate of two lenders. In conjunction with entering into the debt facility, the Company issued warrants to purchase 62,500 shares of Series F-2 convertible preferred stock at an exercise price of $16.00 per share to the lenders. The warrants became exercisable in proportion to the amount of the facility borrowed. The fair value of the warrants was reflected as a discount to debt, and this discount is accreted to interest expense over the term of the debt facility.

The Company borrowed $12,500,000 under the facility in September 2009 and an additional $10,000,000 under the facility in December 2010 and issued the lenders promissory notes. The notes are secured by substantially all of the Company's assets except for intellectual property. The notes carry a fixed interest rate of 13.65% and required interest-only payments for the first five months, with principal repayment beginning in month six and continuing for 30 months. As of December 31, 2011 warrants to acquire 56,250 shares of Series F-2 were exercisable. In connection with the recapitalization of the Company's outstanding convertible preferred stock in 2012, these warrants were amended to be warrants to purchase Series Two convertible preferred stock. As of December 31, 2011 and 2012, the outstanding balance on the notes was $11,569,000 and $4,752,000, respectively. The carrying amount of the notes approximates their fair values based on the short maturity of the notes.

The debt facility has certain representations, warranties and affirmative covenants, as well as certain negative covenants restricting our activities, including limitations on dispositions, mergers or acquisitions, incurring indebtedness or liens, paying dividends or making investments and certain other business transactions. There are no financial covenants associated with the debt facility.

The debt facility contains certain events of default. The obligations under the debt facility and the other loan documents may at the lenders' option be accelerated upon the occurrence of certain events of default, and are automatically accelerated upon certain bankruptcy and insolvency related events of default. As of December 31, 2012, there were no events of default under the debt facility.

As of December 31, 2012, aggregate debt maturities are as follows:



2013	$	4,499,442
2014		439,487

Total debt at maturity value		4,938,929
Less unamortized discount		(55,948	)

Total carrying value of debt	$	4,882,981

Capital structure

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Capital structure

Capital structure

7. Capital structure

2013 Recapitalization

During January and February of 2013, the Company entered into a "bridge" financing arrangement with certain existing investors providing for the issuance by the Company of an aggregate of $6 million of convertible promissory notes and warrants to purchase 2,527,675 shares of Series One convertible preferred stock (Series One) and Series Two convertible preferred stock (Series Two). The warrants have a per share exercise price of $0.01, and as such, they are referred to as "penny warrants". This bridge financing was closed in anticipation of the March 2013 Series Four financing event, which the Company refers to as the "2013 recapitalization".

The Company allocated the proceeds of the convertible promissory notes between debt and warrant liability. Since the value of the warrants exceeded the proceeds from the convertible notes issued to existing investors, the value of the warrant in excess of the proceeds is considered a deemed dividend and reflected as an equity transaction in the financial statements. The Company recorded $6 million to interest expense related to the debt discount associated with the convertible debt during the quarter ended March 31, 2013.

On March 7, 2013, the Company closed a private placement of a new series of convertible preferred stock that resulted in the 2013 recapitalization. In this private placement, the Company issued and sold an aggregate of 4,497,035 shares of its Series Four senior preferred stock (Series Four) for an aggregate purchase price of approximately $54 million. Including the $6 million raised with the bridge financing, total gross proceeds raised during the quarter ended March 31, 2013 was approximately $60 million. In addition, the Company issued an aggregate of 502,919 shares of Series Four upon the share settlement of the convertible promissory notes described above that were issued in January and February 2013.

In connection with this private placement, the Company effected a one-for-120 reverse stock split of its common stock and an exchange of outstanding shares of Series One, Series Two and Series Three convertible preferred stock (Series Three) into an aggregate of 6,700,487 shares of a new series of Series Five junior preferred stock (Series Five). In addition, the Company issued an aggregate of 2,527,675 shares of Series One and Series Two upon the exercise of the warrants issued in connection with the bridge loan that were immediately exchanged for 2,095,515 shares of Series Five during the 2013 recapitalization.

The Company accounted for the 2013 recapitalization as an extinguishment of its Series One, Series Two and Series Three convertible preferred stock and recorded the Series Five shares at their fair value as of the recapitalization date. In accordance with authoritative accounting guidance, the Company recorded a gain attributable to the common stockholders on the extinguishment of the Series One, Series Two and Series Three. The gain of approximately $3.4 million represents the excess of the Series One, Series Two and Series Three over the fair value of the shares Series Five issued in connection with the recapitalization.

Valuation—The value of the Company was estimated using the PWERM. The PWERM considered the most significant near-term driver of value for the Company as the Company's ability to complete a Phase 3 clinical trial of ataluren for the treatment of Duchenne muscular dystrophy caused by nonsense mutations (nmDMD). The remaining scenarios in the PWERM related to funding the completion of the Phase 3 clinical trial for nmDMD. The path to raising this money made up the remaining nodes in the PWERM.

After identifying the various potential liquidity scenarios and their likely timing, a pre-money enterprise value was assigned to each scenario based on a combination of management's guidance and recent trends in the capital markets. The resulting enterprise value for each liquidity event was divided by the total shares that would be outstanding under each scenario to arrive at a price per share for the common and preferred classes of stock. Each scenario was then assigned an outcome probability based on management's estimates. The resulting probability weighted share values were then discounted to present value at a rate that reflects general industry risks (but not Company specific risks).

The rights and preferences of the shares of Series Four and Series Five are as follows:

Dividends—The holders of Series Four and Series Five, in preference to the holders of common stock, are entitled to noncumulative dividends when and if declared by the Board of Directors.

Liquidation—Upon the liquidation, dissolution, reorganization or winding-up of the Company, the holders of Series Four will be entitled to receive, before any distribution or payment is made to any other class of security, an amount equal to the original issuance price, plus all declared, but unpaid, dividends. To the extent there are excess assets to distribute, the holders of Series Five will be entitled to receive, before any distribution or payment is made to the holders of the common stock, an amount equal to the stated liquidation preference, plus all declared, but unpaid, dividends. To the extent there are remaining assets to distribute, the holders of common stock will be entitled to receive such remaining assets.

Voting—Each holder of Series Four and Series Five are entitled to cast the number of votes into which such holder's shares would convert. Except as required by law, holders of common stock have limited voting rights. Additionally, except as required by law, and except in certain enumerated circumstances, holders of Series Four and Series Five shall vote together with the holders of common stock as a single class.

Conversion—Each share of Series Four and Series Five is convertible at any time at the option of the holder into one share of common stock. These conversion ratios are subject to adjustment for certain dilutive events, including certain types of stock splits or stock dividends or future recapitalizations.

In May 2013, the Company issued and sold an additional 375,000 shares of Series Four, at a price per share of $12.00, for an aggregate purchase price of $4.5 million.

Common stock

In May 2013, the Company's Board of Directors and stockholders approved an amendment to the Company's certificate of incorporation increasing the number of authorized shares of common stock to 125,000,000.

Initial public offering

In June 2013, the Company closed the initial public offering of its common stock pursuant to a registration statement on Form S-1, as amended. The Company issued and sold an aggregate of 9,627,800 shares of common stock under the registration statement at a public offering price of $15.00 per share, including 1,255,800 shares pursuant to the exercise by the underwriters of an over-allotment option. The Company received net proceeds from the initial public offering of approximately $131.6 million, after deducting underwriting discounts and commissions and other offering expenses payable by the Company.

Upon closing the initial public offering, all outstanding shares of the Series Four and Series Five were converted into 14,170,956 shares of common stock.

Warrants

All of the Company's outstanding warrants were classified as liabilities as of December 31, 2012 because they contained either non-standard antidilution provisions or they were exercisable into preferred shares that included a put feature.

The following is a summary of the Company's outstanding warrants as of December 31, 2012:

		Exercise price



Series Two	24,712	$	16.00	2014
Series Two	50,000	$	16.00	2017
Series Two	56,250	$	16.00	2019 and 2020
Common stock	645	$	2,520	2013 and 2014

In connection with the 2013 recapitalization, all of the Series Two outstanding warrants became warrants to purchase Series Five. In connection with the Company's initial public offering all of the Series Five outstanding warrants became warrants to purchase common stock.

The following is a summary of the Company's outstanding warrants as of September 30, 2013:

	Warrant shares	Exercise price		Expiration



Common stock	3,088	$	128.00	2014
Common stock	6,250	$	128.00	2017
Common stock	7,030	$	128.00	2019 and 2020
Common stock	645	$	2,520	2013 and 2014

7. Capital structure

Convertible preferred stock prior to 2012 recapitalization

As of December 31, 2011, the Company had authorized for issuance up to 156,995,095 shares of preferred stock, $0.001 par value. The authorized shares as of December 31, 2011 were designated as follows: 750,000 shares of Series A convertible preferred stock (Series A), 187,500 shares of Series B convertible preferred stock (Series B), 6,295,000 shares of Series C convertible preferred stock (Series C), 13,769,935 shares of Series D convertible preferred stock (Series D), 126,735,022 shares of Series E convertible preferred stock (Series E), 3,670,138 shares of Series E-2 convertible preferred stock (Series E-2), 675,000 shares of Series F convertible preferred stock (Series F), 1,612,500 shares of Series F-2 convertible preferred stock (Series F-2) and 3,300,000 shares of Series G convertible preferred stock (Series G).

The rights and preferences of the shares of Series A, Series B, Series C, Series D, Series E, Series E-2, Series F, Series F-2 and Series G were as follows:

Conversion—Each share of Series A, Series B, Series C, Series D, Series E, Series E-2, Series F, Series F-2 and Series G was convertible at any time at the option of the holder into such number of shares of common stock as determined by applying a conversion factor to the outstanding shares of approximately 0.0833, 0.1333, 0.1389, 0.1548, 0.0548, 1.0000, 1.0000, 1.0000 and 1.0000 for the Series A, Series B, Series C, Series D, Series E, Series E-2, Series F, Series F-2, and Series G respectively. These conversion factors were calculated based on the then-applicable conversion price with respect to each respective series of preferred stock. These conversion factors were subject to adjustment in the event the Company issued additional equity securities at prices below the then-applicable conversion price, or if the Company engaged in specified changes to its capitalization, such as stock splits or stock dividends. The conversion of each series of preferred stock would be automatic upon the closing of a qualified initial public offering or any other public offering upon the written election of the Company and holders of both (1) at least two thirds of the outstanding preferred shares on an as-converted to common stock basis and (2) at least two thirds of the Series F, F-2 and G shares voting together as a single class on an as-converted to common stock basis.

Voting—Each preferred shareholder was entitled to the number of votes per share as if the preferred shares were converted to common stock. Additionally, the holders of the preferred stock, voting as a single class, were entitled to elect six members of the Board of Directors.

Liquidation—Upon the liquidation, dissolution, reorganization or winding-up of the Company, holders of preferred stock were entitled to receive, before any distribution or payment on the common stock, an amount equal to $1.00 per share for Series A, $2.00 per share for Series B, $2.50 per share for Series C, $3.25 per share for Series D, $0.397644 per share for Series E, $7.26 per share for Series E-2, $16.00 per share for Series F, $16.00 per share for Series F-2, and $16.00 per share for Series G, plus all declared, but unpaid, dividends. As of December 31, 2011, the aggregate liquidation preference was $750,000, $375,000, $15,000,000, $42,561,249, $49,999,998, $26,645,187, $10,000,000, $24,248,048, and $50,300,000 for the Series A, Series B, Series C, Series D, Series E, Series E-2, Series F, Series F-2, and Series G, respectively. In cases where the liquidation preference applied, if there were insufficient funds to pay the full preference value to all holders, then, as a group, the holders of the Series E, Series E-2, Series F, Series F-2, and Series G would have been paid together first, ratably, in proportion to their respective liquidation preferences. To the extent there were excess assets to distribute, the holders of the Series D would have been paid second. Finally, as a group, the holders of the Series A, Series B, and Series C would have been paid last, ratably, in proportion to their respective liquidation preferences. Dividends were payable only if and when declared. The Company has not declared any dividends through December 31, 2012.

Recapitalization

In July 2012, the Company completed a recapitalization pursuant to which all outstanding shares of Series A, B, C, D, E, E-2, F, F-2, and G convertible preferred stock (Prior Series Preferred) were exchanged into Series Three convertible preferred stock (Series Three). Warrants to acquire Prior Series Preferred became warrants to acquire Series Two convertible preferred stock (Series Two). In addition, those investors that elected to participate in the sale of Series One convertible preferred stock (Series One) were entitled to exchange their Series Three shares for Series Two shares.

In connection with the recapitalization, the Company sold 1,483,337 shares of Series One for aggregate gross proceeds of approximately $29.7 million.

The Company accounted for the recapitalization as an extinguishment of its Prior Series Preferred and recorded the Series One, Series Two and Series Three shares at their fair value as of the recapitalization date. In accordance with authoritative accounting guidance, the Company recorded a gain attributable to the common stockholders on the extinguishment of the Prior Series Preferred. The gain of approximately $160 million represents the excess of the carrying amount of Prior Series Preferred stock immediately prior to the recapitalization over the fair value of the Series One, Two and Three stock issued in connection with the recapitalization.

Valuation—The value of the Company was estimated using the probability weighted expected return method (PWERM). The PWERM considered the most significant near-term driver of value for the Company as the ability to file a marketing authorization application (MAA) with The European Medicines Agency (EMA) for conditional approval of ataluren. The Company has initiated a confirmatory Phase 3 clinical trial of ataluren for the treatment of nmDMD. If favorable, the results of the confirmatory Phase 3 clinical trial could serve as the basis for full approval by the EMA and the FDA of ataluren for the treatment of nmDMD in the European Union and the United States. The remaining scenarios in the PWERM related to funding the completion of the confirmatory Phase 3 clinical trial of ataluren for the treatment of nmDMD.

The rights and preferences of the shares of Series One, Two and Three are as follows:

Dividends—The holders of Series One and Series Two, in preference to the holders of common stock, are entitled to noncumulative dividends when and if declared by the Board of Directors. The holders of Series Three are not entitled to dividends. The Company has not declared any dividends through December 31, 2012.

Liquidation—Upon the liquidation, dissolution, reorganization or winding-up of the Company, the holders of Series One will be entitled to receive, before any distribution or payment is made to any other class of security, an amount equal to two times the original issuance price, plus all declared, but unpaid, dividends. To the extent there are excess assets to distribute, the holders of Series Two will be entitled to receive 76.47% of such excess assets, and the holders of Series One will be entitled to receive 23.53% of such excess assets, until the holders of Series Two receive an amount equal to one times the stated liquidation preference amount for the Series Two, plus all declared, but unpaid, dividends. In the event there are remaining assets after Series Two distributions, the holders of Series Three are entitled to receive 8.82% of such remaining assets, and the holders of Series One and Series Two will be entitled to receive 23.53% and 67.65%, respectively, of such remaining assets, until the holders of Series Three receive an amount equal to one times the stated liquidation preference amount for the Series Three, plus all declared, but unpaid, dividends. To the extent there are remaining assets to distribute, the holders of Series One, Series Two, and Series Three will be entitled to receive 20%, 55%, and 25% of such remaining assets, respectively.

Voting—Each holder of Series One is entitled to cast the number of votes equal to five times the number of common shares into which such holder's shares of Series One would convert. Except as required by law, holders of Series Two and Series Three have limited voting rights. Additionally, the holders of Series One, voting as a single class, are entitled to elect twelve members of the Board of Directors.

Conversion—Each share of Series One is convertible at any time at the option of the holder into two shares of common stock. Each share of Series Two and Series Three is convertible at any time at the option of the holder into one share of common stock. These conversion ratios are subject to adjustment for certain dilutive events, including certain types of stock splits or stock dividends or future recapitalizations.

Warrants

All of the Company's outstanding warrants are classified as liabilities as of December 31, 2011 and 2012 because they contain either non-standard antidilution provisions or they are exercisable into preferred shares that include a put feature.

The following is a summary of the Company's outstanding warrants as of December 31, 2011:

		Exercise price



Series E convertible preferred stock	54,465	$	7.26	2014
Series F convertible preferred stock	50,000	$	16.00	2017
Series F-2 convertible preferred stock	56,250	$	16.00	2019 and 2020
Common stock	645	$	2,520	2013 and 2014

In connection with the recapitalization, all of the Series E, F, and F-2 outstanding warrants became warrants to purchase Series Two.

The following is a summary of the Company's outstanding warrants as of December 31, 2012:

		Exercise price



Series 2 convertible preferred stock	24,712	$	16.00	2014
Series 2 convertible preferred stock	50,000	$	16.00	2017
Series 2 convertible preferred stock	56,250	$	16.00	2019 and 2020
Common stock	645	$	2,520	2013 and 2014

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d),(e))
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
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Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
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-Paragraph d
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Reference 15: http://www.xbrl.org/2003/role/presentationRef
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-Name Regulation S-X (SX)
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Reference 16: http://www.xbrl.org/2003/role/presentationRef
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Reference 17: http://www.xbrl.org/2003/role/presentationRef
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Reference 18: http://www.xbrl.org/2003/role/presentationRef
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Reference 19: http://www.xbrl.org/2003/role/presentationRef
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+ Details

Earnings per share

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Net income (loss) per share

Earnings per share

8. Net income (loss) per share

Basic earnings per share is computed by dividing net income (loss) available to common stockholders by the weighted-average number of common shares outstanding. Diluted earnings per share is computed by dividing net income (loss) available to common stockholders by the weighted-average number of common shares plus the effect of dilutive potential common shares outstanding during the period.

The Series One, Series Two and Series Three outstanding during 2012 (subsequent to the recapitalization) participated in the earnings of the Company through dividend rights. Accordingly, the Company measured earnings per share based upon the two-class method prior to the Company's initial public offering in June 2013.

The following tables set forth the computation of basic and diluted net income (loss) per share for common stockholders:

	Nine months ended September 30,


	2012			2013

Numerator
Net loss	$	(19,963,058	)	$	(33,687,612	)
Deemed dividend		—			(18,248,768	)
Gain on exchange of convertible preferred stock in connection with recapitalization		159,954,069			3,390,750
Less beneficial conversion charge		(377,787	)		—
Less net income attributable to participating securities		(139,077,495	)		—

Net income (loss) attributable to common stockholders	$	535,729		$	(48,545,630	)

Denominator
Denominator for basic net income (loss) per share		2,937			8,995,167
Effect of dilutive securities
Series Three convertible preferred stock		10,656			—

Denominator for diluted net income (loss) per share		13,593			8,995,167

Net income (loss) per share:
Basic	$	182.41		$	(5.40	)*

Diluted	$	39.41		$	(5.40	)*

* In the nine months ended September 30, 2013, the Company experienced a net loss and therefore did not report any dilutive share impact.

The following table shows historical dilutive common share equivalents outstanding, which are not included in the above historical calculation, as the effect of their inclusion is anti-dilutive during each period.

	As of September 30,


	2012		2013

Stock Options		44,218		1,987,860
Unvested restricted stock		—		1,113,807

Total		44,218		3,101,667

8. Earnings per share

Basic earnings per share is computed by dividing net income available to common stockholders by the weighted-average number of common shares outstanding. Diluted earnings per share is computed by dividing net income available to common stockholders by the weighted-average number of common shares plus the effect of dilutive potential common shares outstanding during the period.

The Prior Series Preferred outstanding in 2011 and 2012 (through the date of the recapitalization) as well as Series One and Series Two outstanding during 2012 (subsequent to the recapitalization) participate in earnings of the Company through dividend rights. Accordingly, the Company measures earnings per share based upon the two-class method. Net income attributable to common stockholders excludes $30,878,445 and $132,609,918 for the years ended 2011 and 2012, respectively, for net income attributable to participating securities.

The diluted earnings per share for the years ended December 31, 2011 and 2012 exclude the impact of approximately 1.3 million and 0.6 million common stock equivalents, respectively, since the effect of including these securities would be anti-dilutive.

The following table sets forth the computation of basic and diluted earnings per share for common stockholders:

Net income per share

	Year ended December 31


	2011			2012

Numerator
Net income (loss)	$	30,904,514		$	(26,235,102	)
Gain on exchange of convertible preferred stock in connection with recapitalization		—			159,954,069
Less beneficial conversion charge		—			(377,787	)
Less net income attributable to participating preferred stock		(30,878,445	)		(132,609,918	)

Net income attributable to common stockholders	$	26,069		$	731,262

Denominator
Denominator for basic earnings per share		1,089			3,328
Effect of dilutive securities:
Employee stock options		4,640			—
Series 3 convertible preferred stock		—			13,877

Denominator for diluted earnings per share		5,729			17,205

Net income per share:
Basic		23.95			219.76

Diluted		4.55			42.50

Stock option plan

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Stock option plan

Stock option plan

9. Stock option plan

On March 5, 2013, the Company's Board of Directors approved the 2013 Stock Incentive Plan, which provides for the granting of stock option awards, stock appreciation rights, restricted stock, restricted stock units and other stock-based awards in the aggregate of 739,937 shares of common stock. On March 5, 2013, the Board approved a grant of 735,324 shares of restricted stock and 4,613 stock options. There are no additional shares available for issuance under this plan.

In May 2013, the Company's Board of Directors and stockholders increased by 2,500,000 the number of shares authorized under the 2009 Stock Incentive Plan, which provides for the granting of stock option awards, restricted stock awards, and other stock-based and cash-based awards.

In May 2013, the Company's Board of Directors and stockholders approved the 2013 Long Term Incentive Plan, which became effective upon the closing of the Company's IPO. The 2013 Long Term Incentive Plan provides for the grant of incentive stock options, nonstatutory stock options, restricted stock awards and other stock-based awards. The number of shares of common stock reserved for issuance under the 2013 Long Term Incentive Plan is the sum of (1) 122,296 shares of common stock available for issuance under the Company's 2009 Equity and Long Term Incentive Plan and 2013 Stock Incentive Plan, (2) the number of shares (up to 3,040,444 shares) equal to the sum of the number of shares of common stock subject to outstanding awards under the Company's 1998 Employee, Director and Consultant Stock Option Plan and 2013 Stock Incentive Plan that expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right plus (3) an annual increase, to be added on the first day of each fiscal year until the expiration of the 2013 Long Term Incentive Plan, equal to the lowest of 2,500,000 shares of common stock, 4% of the number of shares of common stock outstanding on the first day of the fiscal year and an amount determined by the Company's Board of Directors.

A summary of stock option activity is as follows:

(in thousands)			Exercise price	Weighted- average exercise price		Weighted- average remaining contractual term	Aggregate intrinsic value




Outstanding at December 31, 2012	42,394		$218.40-$1,149.60	$	469.48
Granted	2,007,713		$10.59-$10.85	$	10.85
Exercised	—		—		—
Forfeited	(62,247	)	$10.85-$1,149.60	$	17.10

Outstanding at September 30, 2013	1,987,860		$10.59-$1,149.60	$	20.44	9.51 years	$	20,652

Exercisable at September 30, 2013	61,834		$10.59-$1,149.60	$	290.39	6.06 years	$	265

The fair value of grants made in the period ended September 30, 2013 was contemporaneously estimated on the date of grant using the following assumptions:

		Nine months ended September 30, 2013



Risk-free interest rate		0.85%-1.69%
Expected volatility		87%-88%
Expected term		5.00 to 6.00 years
Expected dividend yield		0.0%

The Company assumed no expected dividends for all grants. The weighted average grant date fair value of options granted during the nine month period ended September 30, 2013 was $7.86 per share.

The Company uses the "simplified method" to determine the expected term of options. Under this method, the expected term represents the average of the vesting period and the contractual term. The expected volatility of share options was estimated based on a historical volatility analysis of peers that were similar to the Company with respect to industry, stage of life cycle, size, and financial leverage. The risk-free rate of the option is based on U.S. Government Securities Treasury Constant Maturities yields at the date of grant for a term similar to the expected term of the option.

Restricted stock awards—Restricted stock awards are granted subject to certain restrictions, including in some cases service conditions (restricted stock). The grant-date fair value of restricted stock awards, which has been determined based upon the market value of the Company's shares on the grant date, is expensed over the vesting period.

The following table summarizes information on the Company's restricted stock:

	Restricted stock


	Number of shares			Weighted average grant date fair value

January 1, 2013		—			—
Granted		1,131,524		$	10.68
Vested		—		$	—
Forfeited		(17,717	)	$	10.63

Unvested at September 30, 2013		1,113,807		$	10.68

The Company recorded share-based compensation expense in the statement of operations as follows:

	Nine months ended September 30,


	2012		2013

Research and development	$	653,462	$	1,377,640
General and administrative		1,162,260		3,764,547

Total	$	1,815,722	$	5,142,187

As of December 31, 2012 and September 30, 2013, there was approximately $2.2 million and $21.0 million, respectively of total unrecognized compensation cost related to unvested share-based compensation arrangements granted under the 1998, 2009 and 2013 Plans. This cost is expected to be recognized as share-based compensation expense over the weighted average remaining service period of approximately 2.28 years.

9. Stock option plan

In 2009, the Company's shareholders approved the 2009 Equity and Long-Term Incentive Plan, which provides for the granting of stock option awards, restricted stock awards, and other stock-based and cash-based awards, subject to certain adjustments and annual increases. As of December 31, 2012, awards for 14,271 shares of common stock are available for issuance.

The Board of Directors has the authority to select the individuals to whom options are granted and determine the terms of each option, including (i) the number of shares of common stock subject to the option; (ii) the date on which the option becomes exercisable; (iii) the option exercise price, which, in the case of incentive stock options, must be at least 100% (110% in the case of incentive stock options granted to a stockholder owning in excess of 10% of the Company's stock) of the fair market value of the common stock as of the date of grant; and (iv) the duration of the option (which, in the case of incentive stock options, may not exceed ten years). Options typically vest over a three- or four-year period.

A summary of stock option activity is as follows:

	Number of options		Exercise price	Weighted- average exercise price		Weighted- average remaining contractual term



Outstanding at December 31, 2010	39,557		$226.80-$1,149.60	$	547.20
Granted	8,123		$490.80	$	490.80
Exercised	(11	)	$451.20-$508.80	$	459.60
Forfeited	(875	)	$226.80-$1,149.60	$	757.20

Outstanding at December 31, 2011	46,794		$226.80-$1,149.60	$	532.80	5.74 years
Granted	5,715		$218.40	$	218.40
Exercised	—
Forfeited	(10,115	)	$218.40-$1,149.60	$	604.80

Outstanding at December 31, 2012	42,394		$218.40-$1,149.60	$	474.00	5.02 years	—

Exercisable at December 31, 2012	33,414		$218.40-$1,149.60	$	482.40	4.14 years	—

Exercisable and expected to vest at December 31, 2012	42,184		$218.40-$1,149.60	$	476.40	4.97 years	—

The fair value of grants made in the years ended December 31, 2011 and 2012 was contemporaneously estimated on the date of grant using the following assumptions:





Risk-free interest rate	2.40%	1.135%
Expected volatility	87%	87%
Expected term	6.00-6.25 years	6.00-6.25 years

The Company assumed no expected dividends for all grants. The weighted average grant date fair value of options granted during the years ended December 31, 2011 and 2012 was $364.80 and $160.65, respectively.

The Company recognized approximately $2,817,000 and $2,288,000 of share-based compensation expense, during the years ended December 31, 2011 and 2012, respectively. The Company utilizes newly issued shares to satisfy stock option exercises.

As of December 31, 2011 and 2012, there was approximately $4,005,000 and $2,213,000, respectively of total unrecognized compensation cost related to unvested share-based compensation arrangements granted under the 1998 and 2009 Plan. This cost is expected to be recognized as compensation expense over the weighted average remaining service period of approximately 2.14 years.

Collaborations and grants	12 Months Ended
Collaborations and grants	Dec. 31, 2012
Collaborations and grants
Collaborations and grants	10. Collaborations and grants The Company has ongoing collaborations with the Spinal Muscular Atrophy Foundation (SMA Foundation) and F. Hoffman-La Roche Ltd and Hoffman-La Roche Inc. (collectively, Roche) and early stage discovery arrangements with other institutions. During 2011, the Genzyme collaboration was modified and later terminated. The following are the key terms to the Company's (i) terminated collaboration with Genzyme, (ii) ongoing collaborations and (iii) early stage discovery and development arrangements. Terminated collaboration *Genzyme* In July 2008, Genzyme Corporation (now a Sanofi company) and the Company entered into an exclusive global collaboration to develop and commercialize ataluren, the Company's novel oral therapy in late-stage development for the treatment of genetic disorders due to nonsense mutations. Under the terms of this agreement, the Company granted Genzyme rights to commercialize ataluren in all countries except the United States and Canada, which rights the Company retained. Genzyme made a nonrefundable upfront payment to the Company of $100,000,000 in July 2008, which was being recognized over the Company's estimated period of performance under the arrangement. In August 2011, the Company and Genzyme announced a restructuring of the agreement. Under the terms of the restructuring, the Company regained worldwide rights to ataluren and Genzyme made an additional payment of $7.5 million to the Company in exchange for an option to commercialize ataluren in indications other than nonsense mutation Duchenne muscular dystrophy (nmDMD) outside the United States and Canada. On March 27, 2012, the Company received notification that Genzyme declined to exercise the option, at which time the option expired. As a result, the collaboration was terminated. The Company evaluated the August 2011 restructuring of the Genzyme collaboration agreement and determined it to be a material modification to the original agreement for financial reporting purposes pursuant to the revised multiple element revenue recognition guidance. The Company determined that given the significance of the changes in relation to the initial arrangement, including the decrease in the total consideration that could be paid to the Company, the significant removal of existing deliverables, the significant changes in the intellectual property rights and the significant change in the performance period, the initial arrangement had been effectively terminated. The Company elected to reevaluate the amended agreement and performed an analysis to calculate the estimated selling price of the undelivered elements of the arrangement. Based on this analysis, the Company determined that the undelivered element had an estimated selling price of $8.8 million, and as such, adjusted the Company's deferred revenue balance to reflect this amount as of the contract amendment date. The Company amortized the balance through the option period. The effect of this reevaluation was to recognize approximately $79 million as of the restructuring date. For the years ended December 31, 2011 and 2012, the Company recognized approximately $90,012,000 and $3,756,000, respectively, in collaboration revenue from Genzyme. Current collaboration *Roche and SMA Foundation* In November 2011, the Company and the SMA Foundation entered into a licensing and collaboration agreement with Roche for a spinal muscular atrophy program. Under the terms of the agreement, Roche acquired an exclusive worldwide license to the Company's spinal muscular atrophy program, which includes three compounds currently in preclinical development, as well as potential back-up compounds. The Company received a nonrefundable upfront cash payment of $30,000,000 and Roche agreed to provide funding for research activities performed on its behalf. The Company applied the revised multiple element revenue recognition guidance in evaluating the accounting treatment of this collaboration agreement. The Company identified two possible significant deliverables in the collaboration agreement, the license and the research activities. The Company evaluated whether these significant deliverables have stand alone value and determined that the license does not have standalone value without the ongoing research and development services given the unique nature of the technology. As such, both of these elements were combined as a single unit for accounting purposes. As a result, the Company deferred the $30,000,000 upfront payment which is being recognized over the estimated performance period of two years, which is the contracted research period. For the year ended December 31, 2011 and 2012, the Company recognized approximately $2,072,000 and $18,405,000, respectively, in collaboration revenue. The balance of the remaining deferred upfront payment was approximately $13,417,000 at December 31, 2012. Under the agreement, the Company is eligible to receive additional payments from Roche if specified events are achieved with respect to each licensed product, including up to $135 million in research and development event milestones, up to $325 million in sales milestones upon achievement of sales events, and up to double digit royalties on worldwide annual net sales of a commercial product. The Company considers that each of the potential milestone events under the agreement would be substantive because the applicable criteria of its revenue recognition policy (see Note 2) would be satisfied. Early stage collaboration and discovery agreements The Company has arrangements with several organizations pursuant to which the Company uses its discovery technologies to help identify potential drug candidates. The Company does not take ownership of the potential compounds, but rather provides research services to the collaborator using its specialized technology platform. Generally, these arrangements are structured such that the collaborator and the Company work together to jointly select targets from which to apply its discovery technologies. The research period for the Company to apply its technology is generally three to four years. The Company will typically receive a nonrefundable, upfront cash payment and the collaborator agrees to provide funding for research activities performed on its behalf. For those arrangements entered into or significantly modified after January 1, 2011, the Company applies the revised multiple element revenue recognition guidance in evaluating the accounting treatment for these arrangements. Generally, the two significant deliverables in these arrangements are the license and the research activities. The Company evaluates whether the deliverables have standalone value. However, since the Company's discovery technologies are highly specialized, the Company has determined that the license does not have standalone value without the ongoing research and development services and accounts for these arrangements as a single unit of accounting. As a result, the Company has deferred revenue of $7,232,000 and $3,032,000 as of December 31, 2011 and 2012, respectively, related to these arrangements. For the years ended December 31, 2011 and 2012, the Company recognized approximately $6,878,000 and $6,618,000 in collaboration revenue, respectively. The Company is eligible to receive additional payments from its early stage discovery research arrangements if the discovery compounds are ultimately developed and commercialized. The aggregate potential payments the Company is eligible for if all products are developed is $143 million and up to $252 million in sales milestones upon achievement of specified sales events and up to double digit royalties on worldwide annual net sales of the licensed product. The Company considers that each of the potential milestone events under the agreement would be substantive because the applicable criteria of its revenue recognition policy (see Note 2) would be satisfied. Grant revenue The company receives grant funding from various institutions and governmental bodies. The grants are typically for early discovery research, and typically the grant program lasts from two to five years. The Company records revenue as the research activities are performed. If the granting agency provides for an upfront payment, the amount is deferred and recognized as revenue as the expenditures are incurred.

Income taxes

12 Months Ended

Dec. 31, 2012

Income taxes

Income taxes

11. Income taxes

A reconciliation of the U.S. statutory income tax rate to the Company's effective tax rate is as follows:

	December 31


	2011			2012

Federal income tax (benefit) at statutory rate		34.00%			34.00%
State income tax benefit, net of federal benefit		4.20			3.80
Other		(1.60	)		(2.00	)
Increase to valuation allowance		(45.90	)		(35.80	)

Effective income tax rate		(9.3	)		0.00%

The Company recognized a tax benefit of $2.3 million in connection with the sale of net operating losses and research and development credits in the New Jersey Transfer Program for the year ended December 31, 2011. The significant components of the Company's deferred tax assets and liabilities at December 31, 2011 and 2012 are as follows:

	2011			2012



Deferred tax assets:
Amortization	$	103,355		$	91,871
Depreciation		1,196,569			1,535,952
Accrued expense		321,925			1,208,846
Deferred revenue		15,738,180			6,962,506
Federal tax credits		5,734,074			5,383,092
State tax credits		1,495,773			1,094,833
Federal net operating losses		56,074,019			71,752,278
State net operating losses		5,024,189			7,619,606
Capitalized research and development costs		11,184,849			10,479,055
Other		600,059			742,341

Total gross deferred tax assets		97,472,992			106,870,380
Less valuation allowance		(97,472,992	)		(106,870,380	)

Net deferred tax assets	$	—		$	—

At December 31, 2011 and 2012, the Company recorded a full valuation allowance against its net deferred tax assets of approximately $97,473,000 and $106,870,000, respectively. The change in the valuation allowance during the years ended December 31, 2011 and 2012 was approximately $12,909,000 and $9,397,000, respectively. A full valuation allowance has been recorded since, in the judgment of management, these assets are not more likely than not to be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during periods in which those temporary differences and carryforwards become deductible or are utilized.

As of December 31, 2012, the Company has approximately $211,036,000 and $128,276,000 of federal and state net operating loss carryforwards, respectively. As of December 31, 2012, credit carryforwards for federal and state purposes are approximately $5,383,000 and $1,546,000, respectively. The federal net operating loss carryforwards begin to expire in 2021, while the federal credit carryforwards begin to expire in 2013. State net operating loss carryforwards begin to expire in 2029, and the state credit carryforwards begin to expire in 2022. Sections 382 and 383 of the Internal Revenue Code of 1986 subject the future utilization of net operating losses and certain other tax attributes, such as research and experimental tax credits, to an annual limitation in the event of certain ownership changes, as defined. The Company has had a number of equity transactions since inception, and several of these have created ownership changes that could create such a limitation. The Company has not recently performed an analysis to determine the Company's ability to utilize such carryforwards prior to expiration. An analysis will be performed in the future, as necessary.

The State of New Jersey provides the Technology Business Tax Certificate Transfer Program enabling approved unprofitable biotechnology businesses to sell their unused net operating loss carryforwards to unaffiliated, profitable corporate taxpayers in the State of New Jersey for cash. The Company has participated in this program and sold state net operating losses totaling $28,463,900 during 2011. The New Jersey net operating losses sold during 2011 were generated during 2009. For 2011, the Company established a receivable for the $2,305,576, which was received in 2012.

The income tax benefit for the years ended December 31, 2011 and 2012 differed from the amounts computed by applying the U.S. federal income tax rate of 34% to loss before tax benefit as a result of non-deductible expenses, tax credits generated, utilization of net operating loss carryforwards and increases in the Company's valuation allowance. At December 31, 2012 the Company had no unrecognized income tax benefits. The Company applies the accounting guidance for uncertain income tax provisions. This guidance clarifies the accounting for uncertainty in income taxes recognized in financial statements and requires the impact of a tax position to be recognized in the financial statements if that position is more likely than not of being sustained by the taxing authority. As of December 31, 2012, the Company did not have any unrecognized tax benefits and has not accrued any interest or penalties through 2012. The Company does not expect to have any unrecognized tax benefits within the next twelve months. The Company's policy is to recognize interest and penalties related to tax matters within the income tax provision. Tax years beginning in 2009 are generally subject to examination by taxing authorities, although net operating losses from all years are subject to examinations and adjustments for at least three years following the year in which the attributes are used.

Commitments and contingencies

12 Months Ended

Dec. 31, 2012

Commitments and contingencies

Commitments and contingencies

12. Commitments and contingencies

Operating leases

The Company leases office space under a noncancelable operating lease through February 2019. Rent expense was approximately $735,000 and $739,000 for the years ended December 31, 2011 and 2012, respectively. The Company also leases certain office equipment under operating leases. Future minimum lease payments as of December 31, 2012 are as follows:



2013	$	879,000
2014		849,000
2015		849,000
2016		849,000
2017		849,000
Thereafter		1,113,000

	$	5,388,000

Other contingencies

Under various agreements, the Company will be required to pay royalties and milestone payments upon the successful development and commercialization of products. The Company has entered into funding agreements with The Wellcome Trust Limited (Wellcome Trust) for the research and development of small molecule compounds. To the extent that the Company develops and commercializes program intellectual property on a for-profit basis, it may become obligated to pay to Wellcome Trust development and regulatory milestone payments of up to an aggregate of $68.9 million and single-digit royalties on sales of any research program product. The Company's obligation to pay such royalties would continue on a country-by-country basis until the longer of the expiration of the last patent in the program intellectual property in such country covering the research program product and the expiration of market exclusivity of such product in such country.

The Company has also entered into a collaboration agreement with the SMA Foundation. The Company may become obligated to pay the SMA Foundation single-digit royalties on worldwide net product sales of any collaboration product that we successfully develop and subsequently commercialize or, if we outlicense rights to a collaboration product, a specified percentage of certain payments we receive from our licensee. The Company is not obligated to make such payments unless and until annual sales of a collaboration product exceed a designated threshold. The Company's obligation to make such payments would end upon our payment to the SMA Foundation of a specified amount.

The Company has employment agreements with certain employees which require the funding of a specific level of payments, if certain events, such as a change in control or termination without cause, occur.

401(k) plan	12 Months Ended
401(k) plan	Dec. 31, 2012
401(k) plan
401(k) plan	13. 401(k) plan The Company maintains a 401(k) plan for its employees. Employee contributions are voluntary. The Company may match employee contributions in amounts to be determined at the Company's sole discretion. The Company provides a 20% matching contribution for up to the first 5% of each contributing employee's base salary contributions. For the years ended December 31, 2011 and 2012, the Company made matching contributions to the 401(k) plan and recorded expense of approximately $177,000 and $154,000, respectively.

Subsequent events	9 Months Ended	12 Months Ended
Subsequent events	Sep. 30, 2013	Dec. 31, 2012
Subsequent events
Subsequent events	12. Subsequent events The Company continues to advance the development of its spinal muscular atrophy (SMA) collaboration with Roche and the SMA Foundation. The collaboration was initially funded in part by the SMA Foundation. In December 2011, the Company announced a partnership with Roche in the collaboration which provided an upfront payment of $30 million, up to $460 million in milestone payments and royalties on future sales. In August 2013, a development candidate for the program was announced which triggered a $10 million milestone payment from Roche. In January 2014, a Phase 1 clinical program was initiated which triggered a $7.5 million milestone payment from Roche. Roche is responsible for pursuing clinical development of compounds from the program consistent with a governance structure that includes representation from the Company and the SMA Foundation and then commercialization of these compounds. On December 13, 2013, the Compensation Committee of the Company's Board of Directors approved the waiver of the remaining performance vesting triggers with respect to performance-based stock options granted to the Company's executive officers during 2013, such that 25% of the shares underlying such stock options vested on December 31, 2013, and an additional 2.0833% of the shares underlying such stock options will vest at the end of each successive month following December 31, 2013 until December 31, 2016. Approximately $0.6 million is expected to be recorded as share-based compensation in the fourth quarter of 2013 as a result of the modification of these stock options, which represents the incremental fair value of such modified stock options computed in accordance with ASC Topic 718 as of the date of modification.	14. Subsequent events On January 29, 2013, the Company entered into a financing arrangement with certain existing investors providing for the issuance by the Company of convertible promissory notes and warrants to purchase shares of Series One and Series Two. The Company issued convertible promissory notes in January and February 2013 in an aggregate principal amount of $6 million under this financing arrangement. This financing was closed in anticipation of an additional financing event, which is described in the next paragraph below. On March 7, 2013, the Company closed a private placement of a new series of convertible preferred stock that resulted in another recapitalization event. In this private placement, the Company issued and sold an aggregate of 4,497,035 shares of Series Four senior preferred stock (Series Four) for an aggregate purchase price of approximately $54 million. In addition, the Company issued an aggregate of 502,919 shares of Series Four upon conversion of the convertible promissory notes described above that it originally issued in January and February 2013. In connection with this private placement, the Company effected a one-for-120 reverse stock split of its common stock and an exchange of outstanding shares of Series One, Series Two and Series Three into an aggregate of 6,700,487 shares of a new series of Series Five junior preferred stock (Series Five). In addition, the Company issued an aggregate of 2,095,515 shares Series Five upon the automatic exercise of the Series One and Series Two warrants described above that it originally issued in January 2013. The Company expects to account for the March 2013 Series Four financing and recapitalization as an extinguishment of its Series One, Series Two and Series Three stock and will record a gain or loss for the difference between the fair value of the new Series Four and Series Five shares over the carrying value of the Series One, Two and Three shares extinguished. The warrants to purchase shares of Series One, Two and Three issued in connection with the January 2013 convertible note financing will be recorded as a liability and remeasured each reporting period. The Company expects to record a debt discount resulting from the allocation of proceeds to the fair value of the warrants and reflect the discount as interest expense during the quarter ended March 31, 2013. Valuation—The value of the Company was estimated using the PWERM. The PWERM considered the most significant near-term driver of value for the Company as the ability to file a MAA with the EMA for conditional approval of ataluren for the treatment of nmDMD. The Company has initiated a confirmatory Phase 3 clinical trial of ataluren for the treatment of nmDMD. If favorable, the results of the confirmatory Phase 3 clinical trial could serve as the basis for full approval by the EMA and the FDA of ataluren for the treatment of nmDMD in the European Union and the United States. The remaining scenarios in the PWERM related to funding the completion of the confirmatory Phase 3 clinical trial of ataluren for the treatment of nmDMD. After identifying the various potential liquidity scenarios and their likely timing, a pre-money enterprise value was assigned to each scenario based on a combination of management's guidance and recent trends in the capital markets. The resulting enterprise value for each liquidity event was divided by the total shares that would be outstanding under each scenario to arrive at a price per share for the common and preferred classes of stock. Each scenario was then assigned an outcome probability based on management's estimates. The resulting probability weighted share values were then discounted to present value at a rate that reflects general industry risks (but not Company specific risks). The rights and preferences of the shares of Series Four and Five are as follows: Dividends—The holders of Series Four and Series Five, in preference to the holders of common stock, are entitled to noncumulative dividends when and if declared by the Board of Directors. Liquidation—Upon the liquidation, dissolution, reorganization or winding-up of the Company, the holders of Series Four will be entitled to receive, before any distribution or payment is made to any other class of security, an amount equal to the original issuance price, plus all declared, but unpaid, dividends. To the extent there are excess assets to distribute, the holders of Series Five will be entitled to receive, before any distribution or payment is made to the holders of the common stock, an amount equal to the stated liquidation preference, plus all declared, but unpaid, dividends. To the extent there are remaining assets to distribute, the holders of common stock will be entitled to receive such remaining assets. Voting—Each holder of Series Four and Series Five are entitled to cast the number of votes into which such holder's shares would convert. Except as required by law, holders of common stock have limited voting rights. Additionally, except as required by law, and except in certain enumerated circumstances, holders of Series Four and Series Five shall vote together with the holders of common stock as a single class. Conversion—Each share of Series Four and Series Five is convertible at any time at the option of the holder into one share of common stock. These conversion ratios are subject to adjustment for certain dilutive events, including certain types of stock splits or stock dividends or future recapitalizations. On March 5, 2013, the Company's Board of Directors approved the 2013 Stock Incentive Plan, which provides for the granting of stock option awards, stock appreciation rights, restricted stock, restricted stock units and other stock-based in the aggregate of 739,937 shares of Common Stock (calculated after the one-for-120 reverse stock split of its common stock). On March 5, 2013, the Board approved a grant of 735,324 shares of restricted stock and 4,613 stock options. There are no additional shares available for issuance under this plan.

Selected quarterly financial data (unaudited)

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Selected quarterly financial data

Selected quarterly financial data (unaudited)

11. Selected quarterly financial data

	For the quarters ending


	March 31			June 30			September 30

2012:
Collaboration and grant revenue	$	12,525,720		$	7,585,177		$	7,195,076
Operating expenses		18,745,957			15,083,384			14,250,383
Income (loss) from operations		(6,220,237	)		(7,498,207	)		(7,055,307	)
Net income (loss)		(6,597,861	)		(6,068,072	)		(7,297,125	)
Gain on exchange of convertible preferred stock in connection with recapitalization		—			159,954,069			—
Less beneficial conversion charge		—			(377,787	)		—
Net income (loss) attributable to common stockholders		(6,597,861	)		153,508,210			(7,297,125	)
Basic net income (loss) per common share(1)	$	(5,992.61	)	$	168.00		$	(1,605.53	)
Diluted net income (loss) per common share(1)	$	(5,992.61	)	$	48.29		$	(1,605.53	)
2013:
Collaboration and grant revenue	$	7,141,664		$	6,854,212		$	16,289,573
Operating expenses		15,718,073			21,307,148			20,565,188
Income (loss) from operations		(8,576,409	)		(14,452,936	)		(4,275,615	)
Net income (loss)		(14,684,535	)		(14,586,578	)		(4,416,499	)
Deemed dividend		(18,248,768	)		—			—
Gain on exchange of convertible preferred stock in connection with recapitalization		3,390,750			—			—
Net income (loss) attributable to common stockholders		(29,542,553	)		(14,586,578	)		(4,416,499	)
Basic net income (loss) per common share(1)	$	(6,527.30	)	$	(5.51	)	$	(0.19	)
Diluted net income (loss) per common share(1)	$	(6,527.30	)	$	(5.51	)	$	(0.19	)

(1) The amounts were computed independently for each quarter and the sum of the quarters may not total the annual amounts.

15. Selected quarterly financial data (unaudited)

The following financial information reflects all normal recurring adjustments, which are, in the opinion of management, necessary for a fair statement of the results of the interim periods. Net income (loss) per share for all periods presented have been retroactively adjusted to reflect the 1-for-120 reverse stock split effected on March 7, 2013. Summarized quarterly data for 2011 and 2012 are as follows (in thousands, except per share data):

	For the quarters ending


	March 31			June 30			September 30			December 31

2011:
Collaboration and grant revenue	$	4,853,008		$	4,772,720		$	86,423,733		$	9,362,686
Operating expenses		19,848,797			19,682,313			18,315,064			16,983,976
Income (loss) from operations		(14,995,789	)		(14,909,593	)		68,108,669			(7,621,290	)
Net income (loss)		(15,550,607	)		(15,388,398	)		67,608,165			(5,764,646	)
Basic net income (loss) per common share(1)	$	(14,289.99	)	$	(14,140.93	)	$	52.39		$	(5,290.57	)
Diluted net income (loss) per common share(1)	$	(14,289.99	)	$	(14,140.93	)	$	9.95		$	(5,290.57	)
2012:
Collaboration and grant revenue	$	12,525,720		$	7,585,177		$	7,195,076		$	6,640,090
Operating expenses		18,745,957			15,083,384			14,250,383			12,674,520
Income (loss) from operations		(6,220,237	)		(7,498,207	)		(7,055,307	)		(6,034,430	)
Net income (loss)		(6,597,861	)		(6,068,072	)		(7,297,125	)		(6,272,044	)
Gain on exchange of convertible preferred stock in connection with recapitalization		—			159,954,069			—			—
Less beneficial conversion charge		—			(377,787	)		—			—
Net income (loss) attributable to common stockholders		(6,597,861	)		153,508,210			(7,297,125	)		(6,372,044	)
Basic net income (loss) attributable to common stockholders per share	$	(5,992.61	)	$	168.00		$	(1,605.53	)	$	(1,380.13	)
Diluted net income (loss) attributable to common stockholders per share(1)	$	(5,992.61	)	$	48.29		$	(1,605.53	)	$	(1,380.13	)

(1) The amounts were computed independently for each quarter and the sum of the quarters may not total the annual amounts.

Summary of significant accounting policies (Policies)

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Summary of significant accounting policies

Unaudited pro forma presentation

Unaudited pro forma presentation

Unaudited pro forma net loss per share is computed using the weighted-average number of common shares outstanding after giving effect to the pro forma effect of the conversion of all convertible preferred stock during the year ended December 31, 2012 into shares of the Company's common stock as if such conversion had occurred at the beginning of the period presented.

Segment and geographic information

Segment and geographic information

Accounting changes

Accounting changes

Cash equivalents

Cash equivalents

Fixed assets

Fixed assets

Fixed assets are stated at cost. Depreciation is computed starting when the asset is placed into service on a straight-line basis over the estimated useful life of the related asset as follows:



Leasehold improvements		Lesser of useful life or lease term
Computer equipment and software		3 years
Furniture, fixtures, and lab equipment		3 to 7 years

Grant and collaboration receivables

Grant and collaboration receivables

Concentration of risks

Concentration of risks

Reverse stock split

Reverse stock split

Deferred rent

Deferred rent

Revenue recognition

Revenue recognition

The Company's revenue is generated primarily through collaborative research and development and licensing agreements and grants.

Revenue recognition

The Company's revenue is generated primarily through collaborative research and development and licensing agreements and grants.

For new collaborations or for material modifications made to existing collaborations, in 2011 and thereafter, the Company adopted the updated multiple element revenue recognition guidance. Under this new guidance, all non-contingent arrangement consideration is allocated to the identified units of accounting based on their relative selling price at inception of the collaboration arrangement. The Company derives the selling price using a combination of internal subjective and available external objective information, such as comparable transactions. The Company recognizes revenue commensurate with delivery, such as in the case with delivery of a license, or ratably over the course of a service period, as appropriate, such as in the case of ongoing research and development activities.

Research and development costs

Research and development costs

Fair value of financial instruments

Fair value of financial instruments

•: Level 1—Unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the balance sheet date.
•: Level 2—Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability

(i.e., interest rates, yield curves, etc.), and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs).

•: Level 3—Inputs are unobservable and reflect the Company's assumptions as to what market participants would use in pricing the asset or liability. The Company develops these inputs based on the best information available.

Fair value of financial instruments

The Company follows the fair value measurement rules, which provides guidance on the use of fair value in accounting and disclosure for assets and liabilities when such accounting and disclosure is called for by other accounting literature. These rules establishes a fair value hierarchy for inputs to be used to measure fair value of financial assets and liabilities. This hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three levels: Level 1 (highest priority), Level 2, and Level 3 (lowest priority).

•: Level 1—Unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the balance sheet date.
•: Level 2—Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (i.e., interest rates, yield curves, etc.), and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs).
•: Level 3—Inputs are unobservable and reflect the Company's assumptions as to what market participants would use in pricing the asset or liability. The Company develops these inputs based on the best information available.

Beneficial conversion

Beneficial conversion

Warrant liability

Warrant liability

Warrants to purchase the Company's common stock with nonstandard antidilution provisions and preferred stock that include a put feature, regardless of the probability or likelihood that may conditionally obligate the issuer to ultimately transfer assets, are classified as liabilities and are recorded at their estimated fair value at each reporting period. Any change in fair value of these warrants is recorded as gain/(loss) on warrant valuation each reporting period in Other income on the Company's statement of operations.

Impairment of long-lived assets

Impairment of long-lived assets

Share-based compensation

Share-based compensation

Income taxes

Income taxes

Net income per share

Net income per share

Summary of significant accounting policies (Tables)

12 Months Ended

Dec. 31, 2012

Summary of significant accounting policies

Schedule of estimated useful life of related assets



Leasehold improvements		Lesser of useful life or lease term
Computer equipment and software		3 years
Furniture, fixtures, and lab equipment		3 to 7 years

Fair value of financial instruments and investments (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Fair value of financial instruments and marketable securities

Schedule of financial assets that are required to be measured at fair value on a recurring basis

	December 31, 2012


	Total		Quoted prices in active markets for identical assets (level 1)		Significant other observable inputs (level 2)		Significant unobservable inputs (level 3)

Warrant liability	$	95,661	$	—	$	—	$	95,661

	September 30, 2013


	Total		Quoted prices in active markets for identical assets (level 1)		Significant other observable inputs (level 2)		Significant unobservable inputs (level 3)

Marketable securities	$	133,182,565	$	—	$	133,182,565	$	—
Warrant liability		98,819		—		—		98,819

	December 31, 2011


	Total		Quoted prices in active markets for identical assets (level 1)	Significant other observable inputs (level 2)	Significant unobservable inputs (level 3)

Warrant liability	$	1,878,316	$—	$—	$1,878,316

	December 31, 2012


	Total		Quoted prices in active markets for identical assets (level 1)	Significant other observable inputs (level 2)	Significant unobservable inputs (level 3)

Warrant liability	$	95,661	$—	$—	$95,661

Summary of changes in the fair value of the Company's Level 3 valuation for warrant liability

	Level 3 assets



Beginning balance as of December 31, 2012	$	95,661
Warrants issued in connection with convertible promissory notes		6,000,000
Deemed dividend		18,248,768
Exercise of warrants issued in connection with convertible promissory notes		(24,248,765	)
Change in fair value of warrant liability		3,155

Ending balance as of September 30, 2013	$	98,819

	Level 3 assets



Beginning balance January 1, 2011	$	2,340,263
Change in fair value of warrant liability		(461,947	)

Ending balance as of December 31, 2011		1,878,316
Change in fair value of warrant liability		(1,782,655	)

Ending balance as of December 31, 2012	$	95,661

Fixed assets (Tables)

12 Months Ended

Dec. 31, 2012

Fixed assets

Schedule of fixed assets, net

	December 31,


	2011			2012

Leasehold improvements	$	12,473,836		$	12,473,836
Computer equipment and software		2,082,638			2,118,713
Furniture, fixtures, and lab equipment		13,781,118			13,969,758
Assets not yet placed in service		40,186			4,152

		28,377,778			28,566,459
Less accumulated depreciation and amortization		(17,582,271	)		(20,286,422	)

	$	10,795,507		$	8,280,037

Accounts payable and accrued expenses (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Accounts payable and accrued expenses

Schedule of components of accounts payable and accrued expenses

	December 31, 2012		September 30, 2013



Employee compensation, benefits, and related accruals	$	3,096,475	$	3,659,084
Consulting and contracted research		2,515,678		3,556,350
Professional fees		559,228		1,532,458
Accounts payable		621,591		1,017,122
Other		230,999		440,479

	$	7,023,971	$	10,205,493

	December 31,


	2011		2012

Employee compensation, benefits, and related accruals	$	3,492,170	$	3,096,475
Consulting and contracted research		6,749,272		2,515,678
Professional fees		492,811		559,228
Accounts payable		1,878,109		621,591
Other		437,092		230,999

	$	13,049,454	$	7,023,971

Long-term debt (Tables)

12 Months Ended

Dec. 31, 2012

Debt

Schedule of aggregate debt maturities

As of December 31, 2012, aggregate debt maturities are as follows:



2013	$	4,499,442
2014		439,487

Total debt at maturity value		4,938,929
Less unamortized discount		(55,948	)

Total carrying value of debt	$	4,882,981

Capital structure (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Capital structure

Summary of the Company's outstanding warrants

The following is a summary of the Company's outstanding warrants as of December 31, 2012:

		Exercise price



Series Two	24,712	$	16.00	2014
Series Two	50,000	$	16.00	2017
Series Two	56,250	$	16.00	2019 and 2020
Common stock	645	$	2,520	2013 and 2014

The following is a summary of the Company's outstanding warrants as of September 30, 2013:

	Warrant shares	Exercise price		Expiration



Common stock	3,088	$	128.00	2014
Common stock	6,250	$	128.00	2017
Common stock	7,030	$	128.00	2019 and 2020
Common stock	645	$	2,520	2013 and 2014

The following is a summary of the Company's outstanding warrants as of December 31, 2011:

		Exercise price



Series E convertible preferred stock	54,465	$	7.26	2014
Series F convertible preferred stock	50,000	$	16.00	2017
Series F-2 convertible preferred stock	56,250	$	16.00	2019 and 2020
Common stock	645	$	2,520	2013 and 2014

The following is a summary of the Company's outstanding warrants as of December 31, 2012:

		Exercise price



Series 2 convertible preferred stock	24,712	$	16.00	2014
Series 2 convertible preferred stock	50,000	$	16.00	2017
Series 2 convertible preferred stock	56,250	$	16.00	2019 and 2020
Common stock	645	$	2,520	2013 and 2014

- Definition

Tabular disclosure of warrants or rights issued. Warrants and rights outstanding are derivative securities that give the holder the right to purchase securities (usually equity) from the issuer at a specific price within a certain time frame. Warrants are often included in a new debt issue to entice investors by a higher return potential. The main difference between warrants and call options is that warrants are issued and guaranteed by the company, whereas options are exchange instruments and are not issued by the company. Also, the lifetime of a warrant is often measured in years, while the lifetime of a typical option is measured in months. Disclose the title of issue of securities called for by warrants and rights outstanding, the aggregate amount of securities called for by warrants and rights outstanding, the date from which the warrants or rights are exercisable, and the price at which the warrant or right is exercisable.

+ References + Details

Earnings per share (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Net income (loss) per share

Schedule of computation of basic and diluted earnings per share for common stockholders

	Nine months ended September 30,


	2012			2013

Numerator
Net loss	$	(19,963,058	)	$	(33,687,612	)
Deemed dividend		—			(18,248,768	)
Gain on exchange of convertible preferred stock in connection with recapitalization		159,954,069			3,390,750
Less beneficial conversion charge		(377,787	)		—
Less net income attributable to participating securities		(139,077,495	)		—

Net income (loss) attributable to common stockholders	$	535,729		$	(48,545,630	)

Denominator
Denominator for basic net income (loss) per share		2,937			8,995,167
Effect of dilutive securities
Series Three convertible preferred stock		10,656			—

Denominator for diluted net income (loss) per share		13,593			8,995,167

Net income (loss) per share:
Basic	$	182.41		$	(5.40	)*

Diluted	$	39.41		$	(5.40	)*

* In the nine months ended September 30, 2013, the Company experienced a net loss and therefore did not report any dilutive share impact.

	Year ended December 31


	2011			2012

Numerator
Net income (loss)	$	30,904,514		$	(26,235,102	)
Gain on exchange of convertible preferred stock in connection with recapitalization		—			159,954,069
Less beneficial conversion charge		—			(377,787	)
Less net income attributable to participating preferred stock		(30,878,445	)		(132,609,918	)

Net income attributable to common stockholders	$	26,069		$	731,262

Denominator
Denominator for basic earnings per share		1,089			3,328
Effect of dilutive securities:
Employee stock options		4,640			—
Series 3 convertible preferred stock		—			13,877

Denominator for diluted earnings per share		5,729			17,205

Net income per share:
Basic		23.95			219.76

Diluted		4.55			42.50

Stock option plan (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Stock option plan

Summary of stock option activity

(in thousands)			Exercise price	Weighted- average exercise price		Weighted- average remaining contractual term	Aggregate intrinsic value




Outstanding at December 31, 2012	42,394		$218.40-$1,149.60	$	469.48
Granted	2,007,713		$10.59-$10.85	$	10.85
Exercised	—		—		—
Forfeited	(62,247	)	$10.85-$1,149.60	$	17.10

Outstanding at September 30, 2013	1,987,860		$10.59-$1,149.60	$	20.44	9.51 years	$	20,652

Exercisable at September 30, 2013	61,834		$10.59-$1,149.60	$	290.39	6.06 years	$	265

	Number of options		Exercise price	Weighted- average exercise price		Weighted- average remaining contractual term



Outstanding at December 31, 2010	39,557		$226.80-$1,149.60	$	547.20
Granted	8,123		$490.80	$	490.80
Exercised	(11	)	$451.20-$508.80	$	459.60
Forfeited	(875	)	$226.80-$1,149.60	$	757.20

Outstanding at December 31, 2011	46,794		$226.80-$1,149.60	$	532.80	5.74 years
Granted	5,715		$218.40	$	218.40
Exercised	—
Forfeited	(10,115	)	$218.40-$1,149.60	$	604.80

Outstanding at December 31, 2012	42,394		$218.40-$1,149.60	$	474.00	5.02 years	—

Exercisable at December 31, 2012	33,414		$218.40-$1,149.60	$	482.40	4.14 years	—

Exercisable and expected to vest at December 31, 2012	42,184		$218.40-$1,149.60	$	476.40	4.97 years	—

Schedule of assumptions used to estimate fair value of grants made on the date of grant

		Nine months ended September 30, 2013



Risk-free interest rate		0.85%-1.69%
Expected volatility		87%-88%
Expected term		5.00 to 6.00 years
Expected dividend yield		0.0%





Risk-free interest rate	2.40%	1.135%
Expected volatility	87%	87%
Expected term	6.00-6.25 years	6.00-6.25 years

Income taxes (Tables)

12 Months Ended

Dec. 31, 2012

Income taxes

Schedule of reconciliation of the U.S. statutory income tax rate to the Company's effective tax rate

	December 31


	2011			2012

Federal income tax (benefit) at statutory rate		34.00%			34.00%
State income tax benefit, net of federal benefit		4.20			3.80
Other		(1.60	)		(2.00	)
Increase to valuation allowance		(45.90	)		(35.80	)

Effective income tax rate		(9.3	)		0.00%

Schedule of significant components of the Company's deferred tax assets and liabilities

	2011			2012



Deferred tax assets:
Amortization	$	103,355		$	91,871
Depreciation		1,196,569			1,535,952
Accrued expense		321,925			1,208,846
Deferred revenue		15,738,180			6,962,506
Federal tax credits		5,734,074			5,383,092
State tax credits		1,495,773			1,094,833
Federal net operating losses		56,074,019			71,752,278
State net operating losses		5,024,189			7,619,606
Capitalized research and development costs		11,184,849			10,479,055
Other		600,059			742,341

Total gross deferred tax assets		97,472,992			106,870,380
Less valuation allowance		(97,472,992	)		(106,870,380	)

Net deferred tax assets	$	—		$	—

Commitments and contingencies (Tables)

12 Months Ended

Dec. 31, 2012

Commitments and contingencies

Schedule of future minimum lease payments

Future minimum lease payments as of December 31, 2012 are as follows:



2013	$	879,000
2014		849,000
2015		849,000
2016		849,000
2017		849,000
Thereafter		1,113,000

	$	5,388,000

Selected quarterly financial data (unaudited) (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Selected quarterly financial data

Summary of quarterly data

Summarized quarterly data for 2012 and 2013 are as follows (in thousands, except per share data):

	For the quarters ending


	March 31			June 30			September 30

2012:
Collaboration and grant revenue	$	12,525,720		$	7,585,177		$	7,195,076
Operating expenses		18,745,957			15,083,384			14,250,383
Income (loss) from operations		(6,220,237	)		(7,498,207	)		(7,055,307	)
Net income (loss)		(6,597,861	)		(6,068,072	)		(7,297,125	)
Gain on exchange of convertible preferred stock in connection with recapitalization		—			159,954,069			—
Less beneficial conversion charge		—			(377,787	)		—
Net income (loss) attributable to common stockholders		(6,597,861	)		153,508,210			(7,297,125	)
Basic net income (loss) per common share(1)	$	(5,992.61	)	$	168.00		$	(1,605.53	)
Diluted net income (loss) per common share(1)	$	(5,992.61	)	$	48.29		$	(1,605.53	)
2013:
Collaboration and grant revenue	$	7,141,664		$	6,854,212		$	16,289,573
Operating expenses		15,718,073			21,307,148			20,565,188
Income (loss) from operations		(8,576,409	)		(14,452,936	)		(4,275,615	)
Net income (loss)		(14,684,535	)		(14,586,578	)		(4,416,499	)
Deemed dividend		(18,248,768	)		—			—
Gain on exchange of convertible preferred stock in connection with recapitalization		3,390,750			—			—
Net income (loss) attributable to common stockholders		(29,542,553	)		(14,586,578	)		(4,416,499	)
Basic net income (loss) per common share(1)	$	(6,527.30	)	$	(5.51	)	$	(0.19	)
Diluted net income (loss) per common share(1)	$	(6,527.30	)	$	(5.51	)	$	(0.19	)

(1) The amounts were computed independently for each quarter and the sum of the quarters may not total the annual amounts.

	For the quarters ending


	March 31			June 30			September 30			December 31

2011:
Collaboration and grant revenue	$	4,853,008		$	4,772,720		$	86,423,733		$	9,362,686
Operating expenses		19,848,797			19,682,313			18,315,064			16,983,976
Income (loss) from operations		(14,995,789	)		(14,909,593	)		68,108,669			(7,621,290	)
Net income (loss)		(15,550,607	)		(15,388,398	)		67,608,165			(5,764,646	)
Basic net income (loss) per common share(1)	$	(14,289.99	)	$	(14,140.93	)	$	52.39		$	(5,290.57	)
Diluted net income (loss) per common share(1)	$	(14,289.99	)	$	(14,140.93	)	$	9.95		$	(5,290.57	)
2012:
Collaboration and grant revenue	$	12,525,720		$	7,585,177		$	7,195,076		$	6,640,090
Operating expenses		18,745,957			15,083,384			14,250,383			12,674,520
Income (loss) from operations		(6,220,237	)		(7,498,207	)		(7,055,307	)		(6,034,430	)
Net income (loss)		(6,597,861	)		(6,068,072	)		(7,297,125	)		(6,272,044	)
Gain on exchange of convertible preferred stock in connection with recapitalization		—			159,954,069			—			—
Less beneficial conversion charge		—			(377,787	)		—			—
Net income (loss) attributable to common stockholders		(6,597,861	)		153,508,210			(7,297,125	)		(6,372,044	)
Basic net income (loss) attributable to common stockholders per share	$	(5,992.61	)	$	168.00		$	(1,605.53	)	$	(1,380.13	)
Diluted net income (loss) attributable to common stockholders per share(1)	$	(5,992.61	)	$	48.29		$	(1,605.53	)	$	(1,380.13	)

(1) The amounts were computed independently for each quarter and the sum of the quarters may not total the annual amounts.

The Company (Details) - USD ($)	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
The Company
Accumulated deficit	$ 310,912,330	$ 277,224,718	$ 250,611,829

Summary of significant accounting policies (Details)	12 Months Ended
Summary of significant accounting policies (Details)	Dec. 31, 2012 item
Segment and geographic information
Number of operating segments	1
Computer equipment and software
Fixed assets
Estimated useful life	3 years
Furniture, fixtures, and lab equipment \| Minimum
Fixed assets
Estimated useful life	3 years
Furniture, fixtures, and lab equipment \| Maximum
Fixed assets
Estimated useful life	7 years

Summary of significant accounting policies (Details 2) - item	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Concentration of risks
Number of largest collaboration partners	2
Revenue \| Customer concentration risk \| Collaboration partner one
Concentration of risks
Concentration risk (as a percent)	67.00%	85.00%
Revenue \| Customer concentration risk \| Collaboration partner two
Concentration of risks
Concentration risk (as a percent)	11.00%	8.00%
Revenue \| Customer concentration risk \| Granting agency
Concentration of risks
Concentration risk (as a percent)	9.00%	3.00%

Summary of significant accounting policies (Details 3)		3 Months Ended	9 Months Ended	12 Months Ended
Summary of significant accounting policies (Details 3)	Mar. 07, 2013	Jun. 30, 2012 USD ($)	Sep. 30, 2012 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)
Research and development costs
Deferred research and development advance payments				$ 228,000	$ 245,000
Beneficial conversion
Beneficial conversion charge		$ 377,787	$ 377,787	377,787
Impairment of long-lived assets
Impairment of long-lived assets				$ 0
Common stock
Reverse stock split
Reverse stock split ratio	0.0083
Common stock \| Subsequent event
Reverse stock split
Reverse stock split ratio	0.0083

Fair value of financial instruments and investments (Details) - Recurring basis - USD ($)	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Total
Financial assets measured at fair value on recurring basis
Warrant liability	$ 98,819	$ 95,661	$ 1,878,316
Significant unobservable inputs (level 3)
Financial assets measured at fair value on recurring basis
Warrant liability	$ 98,819	$ 95,661	$ 1,878,316

Fair value of financial instruments and investments (Details 2) - Warrant - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Changes in the fair value of warrant liability
Beginning balance	$ 95,661	$ 1,878,316	$ 2,340,263
Change in fair value of warrant liability	3,155	(1,782,655)	(461,947)
Ending balance	$ 98,819	$ 95,661	$ 1,878,316
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model
Volatility (as a percent)		87.00%	88.00%
Strike price (in dollars per share)	$ 128	$ 16
Minimum
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model
Volatility (as a percent)	69.00%
Risk-free interest rate (as a percent)	0.02%	0.16%	0.25%
Strike price (in dollars per share)			$ 7.26
Expected life	2 months 19 days	1 year	2 years
Maximum
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model
Volatility (as a percent)	87.00%
Risk-free interest rate (as a percent)	1.705%	1.18%	1.62%
Strike price (in dollars per share)			$ 16.00
Expected life	5 years 11 months 23 days	7 years	8 years
Preferred shares
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model
Fair value of common shares (in dollars per share)	$ 21.46	$ 2.35	$ 16.00

Fixed assets (Details) - USD ($)	9 Months Ended		12 Months Ended
Fixed assets (Details) - USD ($)	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Fixed assets
Gross fixed assets			$ 28,566,459	$ 28,377,778
Less accumulated depreciation and amortization			(20,286,422)	(17,582,271)
Net fixed assets	$ 6,942,956		8,280,037	10,795,507
Depreciation expense	$ 1,810,850	$ 2,048,682	2,704,151	2,871,200
Leasehold improvements
Fixed assets
Gross fixed assets			12,473,836	12,473,836
Computer equipment and software
Fixed assets
Gross fixed assets			2,118,713	2,082,638
Furniture, fixtures, and lab equipment
Fixed assets
Gross fixed assets			13,969,758	13,781,118
Assets not yet placed in service
Fixed assets
Gross fixed assets			$ 4,152	$ 40,186

Accounts payable and accrued expenses (Details) - USD ($)	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Accounts payable and accrued expenses
Employee compensation, benefits, and related accruals	$ 3,659,084	$ 3,096,475	$ 3,492,170
Consulting and contracted research	3,556,350	2,515,678	6,749,272
Professional fees	1,532,458	559,228	492,811
Accounts payable	1,017,122	621,591	1,878,109
Other	440,479	230,999	437,092
Accounts payable and accrued expenses	$ 10,205,493	$ 7,023,971	$ 13,049,454

Long-term debt (Details) - Laboratory instrument - USD ($)	Dec. 31, 2012	Dec. 31, 2011	May 31, 2009
Capital lease information
Implied interest rate (as a percent)			8.20%
Remaining principal	$ 187,000	$ 314,000

Long-term debt (Details 2) - Secured debt facility	1 Months Ended
Long-term debt (Details 2) - Secured debt facility	Jul. 31, 2013 USD ($) item	Sep. 30, 2009 USD ($) item
Debt
Maximum borrowing capacity \| $	$ 25,000,000	$ 25,000,000
Number of lenders \| item	2	2

Long-term debt (Details 3)	1 Months Ended		12 Months Ended
Long-term debt (Details 3)	Dec. 31, 2010 USD ($)	Sep. 30, 2009 USD ($) $ / shares shares	Dec. 31, 2012 USD ($) item	Jul. 31, 2013	Dec. 31, 2011 USD ($) shares
Series F-2 convertible preferred stock \| Warrants
Long-term debt
Number of shares that can be acquired from warrants exercisable \| shares					56,250
Secured debt facility
Long-term debt
Amount borrowed	$ 10,000,000	$ 12,500,000
Fixed interest rate of notes (as a percent)			13.65%	13.65%
Period of interest-only payments			5 months
Period for principal repayment			30 months
Outstanding balance of the notes			$ 4,752,000		$ 11,569,000
Number of financial covenants associated with the debt facility \| item			0
Number of events of default \| item			0
Aggregate debt maturities
2013			$ 4,499,442
2014			439,487
Total debt at maturity value			4,938,929
Less unamortized discount			(55,948)
Total carrying value of debt			$ 4,882,981
Secured debt facility \| Series F-2 convertible preferred stock \| Warrants
Long-term debt
Number of shares purchased through warrants \| shares		62,500
Exercise price (in dollars per share) \| $ / shares		16.00

Capital structure (Details)	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
Capital structure (Details)	Jul. 31, 2012 USD ($) shares	Mar. 31, 2013 USD ($)	Jun. 30, 2012 USD ($)	Sep. 30, 2013 USD ($)	Sep. 30, 2012 USD ($)	Dec. 31, 2012 USD ($) item shares	Dec. 31, 2011 USD ($) item $ / shares shares
Capital structure
Par value (in dollars per share) \| $ / shares							$ 0.001
Number of members of board of directors who can be elected by holders of the preferred stock, voting as a single class \| item							6
Aggregate gross proceeds \| $					$ 29,354,752	$ 29,354,752
Gain on exchange of convertible preferred stock in connection with recapitalization \| $	$ 160,000,000	$ 3,390,750	$ 159,954,069	$ 3,390,750	$ 159,954,069	$ 159,954,069
Maximum
Capital structure
Shares authorized							156,995,095
Minimum
Capital structure
Percentage of the outstanding preferred shares on an as-converted to common stock basis							66.67%
Series A
Capital structure
Shares authorized							750,000
Conversion factor							0.0833
Liquidation preference (in dollars per share) \| $ / shares							$ 1.00
Aggregate liquidation preference \| $							$ 750,000
Series B
Capital structure
Shares authorized							187,500
Conversion factor							0.1333
Liquidation preference (in dollars per share) \| $ / shares							$ 2.00
Aggregate liquidation preference \| $							$ 375,000
Series C
Capital structure
Shares authorized							6,295,000
Conversion factor							0.1389
Liquidation preference (in dollars per share) \| $ / shares							$ 2.50
Aggregate liquidation preference \| $							$ 15,000,000
Series D
Capital structure
Shares authorized							13,769,935
Conversion factor							0.1548
Liquidation preference (in dollars per share) \| $ / shares							$ 3.25
Aggregate liquidation preference \| $							$ 42,561,249
Series E
Capital structure
Shares authorized							126,735,022
Conversion factor							0.0548
Liquidation preference (in dollars per share) \| $ / shares							$ 0.397644
Aggregate liquidation preference \| $							$ 49,999,998
Series E-2
Capital structure
Shares authorized							3,670,138
Conversion factor							1.0000
Liquidation preference (in dollars per share) \| $ / shares							$ 7.26
Aggregate liquidation preference \| $							$ 26,645,187
Series F
Capital structure
Shares authorized							675,000
Conversion factor							1.0000
Liquidation preference (in dollars per share) \| $ / shares							$ 16.00
Aggregate liquidation preference \| $							$ 10,000,000
Series F-2
Capital structure
Shares authorized							1,612,500
Conversion factor							1.0000
Liquidation preference (in dollars per share) \| $ / shares							$ 16.00
Aggregate liquidation preference \| $							$ 24,248,048
Series G
Capital structure
Shares authorized							3,300,000
Conversion factor							1.0000
Liquidation preference (in dollars per share) \| $ / shares							$ 16.00
Aggregate liquidation preference \| $							$ 50,300,000
Series F, F-2 and G \| Minimum
Capital structure
Percentage of the outstanding preferred shares on an as-converted to common stock basis							66.67%
Series One
Capital structure
Shares authorized						2,000,000
Number of members of board of directors who can be elected by holders of the preferred stock, voting as a single class \| item						12
Shares sold	1,483,337
Aggregate gross proceeds \| $	$ 29,700,000
Original issuance price multiplier \| item						2
Assets available for distribution to series two convertible preferred stock, distribution percentage						23.53%
Assets available for distribution to series three convertible preferred stock, distribution percentage						23.53%
Remaining assets distribution percentage						20.00%
Shares issued upon conversion of preferred stock multiplier \| item						5
Number of shares issued for each share of convertible preferred stock upon conversion						2
Series Two
Capital structure
Shares authorized						13,750,000
Assets available for distribution to series two convertible preferred stock, distribution percentage						76.47%
Stated liquidation preference amount multiplier \| item						1
Assets available for distribution to series three convertible preferred stock, distribution percentage						67.65%
Remaining assets distribution percentage						55.00%
Number of shares issued for each share of convertible preferred stock upon conversion						1
Series Three
Capital structure
Shares authorized						13,750,000
Stated liquidation preference amount multiplier \| item						1
Assets available for distribution to series three convertible preferred stock, distribution percentage						8.82%
Remaining assets distribution percentage						25.00%
Number of shares issued for each share of convertible preferred stock upon conversion						1

Capital structure (Details 2) - Warrants	Sep. 30, 2013 $ / shares shares	Dec. 31, 2012 $ / shares shares	Dec. 31, 2011 $ / shares shares
Series E convertible preferred stock \| 2014
Warrants
Warrant shares \| shares			54,465
Exercise price (in dollars per share) \| $ / shares			7.26
Series F convertible preferred stock \| 2017
Warrants
Warrant shares \| shares			50,000
Exercise price (in dollars per share) \| $ / shares			16.00
Series F-2 convertible preferred stock \| 2019 and 2020
Warrants
Warrant shares \| shares			56,250
Exercise price (in dollars per share) \| $ / shares			16.00
Series 2 convertible preferred stock \| 2014
Warrants
Warrant shares \| shares		24,712
Exercise price (in dollars per share) \| $ / shares		16.00
Series 2 convertible preferred stock \| 2017
Warrants
Warrant shares \| shares		50,000
Exercise price (in dollars per share) \| $ / shares		16.00
Series 2 convertible preferred stock \| 2019 and 2020
Warrants
Warrant shares \| shares		56,250
Exercise price (in dollars per share) \| $ / shares		16.00
Common stock \| 2014
Warrants
Warrant shares \| shares	3,088
Exercise price (in dollars per share) \| $ / shares	128.00
Common stock \| 2017
Warrants
Warrant shares \| shares	6,250
Exercise price (in dollars per share) \| $ / shares	128.00
Common stock \| 2019 and 2020
Warrants
Warrant shares \| shares	7,030
Exercise price (in dollars per share) \| $ / shares	128.00
Common stock \| 2013 and 2014
Warrants
Warrant shares \| shares	645	645	645
Exercise price (in dollars per share) \| $ / shares	2,520	2,520	2,520

Earnings per share (Details) - USD ($)	1 Months Ended	3 Months Ended											9 Months Ended		12 Months Ended
Earnings per share (Details) - USD ($)	Jul. 31, 2012	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Net income per share
Common stock equivalents excluded from calculation of diluted earnings per share since the effect would be anti-dilutive													3,101,667	44,218	600,000	1,300,000
Numerator
Net income (loss)		$ (4,416,499)	$ (14,586,578)	$ (14,684,535)	$ (6,272,044)	$ (7,297,125)	$ (6,068,072)	$ (6,597,861)	$ (5,764,646)	$ 67,608,165	$ (15,388,398)	$ (15,550,607)	$ (33,687,612)	$ (19,963,058)	$ (26,235,102)	$ 30,904,514
Gain on exchange of convertible preferred stock in connection with recapitalization	$ 160,000,000			$ 3,390,750			159,954,069						3,390,750	159,954,069	159,954,069
Less beneficial conversion charge							$ (377,787)							(377,787)	(377,787)
Less net income attributable to participating preferred stock														(139,077,495)	(132,609,918)	(30,878,445)
Net loss attributable to common stockholders													$ (48,545,630)	$ 535,729	$ 731,262	$ 26,069
Denominator
Denominator for basic net income (loss) per share (in shares)													8,995,167	2,937	3,328	1,089
Effect of dilutive securities:
Employee stock options (in shares)																4,640
Series 3 convertible preferred stock (in shares)														10,656	13,877
Denominator for diluted net income (loss) per share (in shares)													8,995,167	13,593	17,205	5,729
Net income per share:
Basic (in dollars per share)		$ (0.19)	$ (5.51)	$ (6,527.30)	$ 1,380.13	$ (1,605.53)	$ 168.00	$ (5,992.61)	$ (5,290.57)	$ 52.39	$ (14,140.93)	$ (14,289.99)	$ (5.40)	$ 182.41	$ 219.76	$ 23.95
Diluted (in dollars per share)		$ (0.19)	$ (5.51)	$ (6,527.30)	$ 1,380.13	$ (1,605.53)	$ 48.29	$ (5,992.61)	$ (5,290.57)	$ 9.95	$ (14,140.93)	$ (14,289.99)	$ (5.40)	$ 39.41	$ 42.50	$ 4.55

Stock option plan (Details) - USD ($)	9 Months Ended		12 Months Ended
Stock option plan (Details) - USD ($)	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Valuation assumptions
Share-based compensation expense	$ 5,142,187	$ 1,815,722	$ 2,288,000	$ 2,817,000
Stock options
Number of options
Outstanding at the beginning of the period (in shares)	42,394	46,794	46,794	39,557
Granted (in shares)	2,007,713		5,715	8,123
Exercised (in shares)				(11)
Forfeited (in shares)	(62,247)		(10,115)	(875)
Outstanding at the end of the period (in shares)	1,987,860		42,394	46,794
Exercisable at the end of the period (in shares)	61,834		33,414
Exercisable and expected to vest at the end of the period (in shares)			42,184
Exercise price
Granted (in dollars per share)			$ 218.40	$ 490.80
Weighted-average exercise price
Outstanding at the beginning of the period (in dollars per share)	$ 469.48	$ 532.80	532.80	547.20
Granted (in dollars per share)	10.85		218.40	490.80
Exercised (in dollars per share)				459.60
Forfeited (in dollars per share)	17.10		604.80	757.20
Outstanding at the end of the period (in dollars per share)	20.44		469.48	$ 532.80
Exercisable at the end of the period (in dollars per share)	$ 290.39		482.40
Exercisable and expected to vest at the end of the period (in dollars per share)			$ 476.40
Weighted-average remaining contractual term
Outstanding at the end of the period	9 years 6 months 4 days		5 years 7 days	5 years 8 months 26 days
Exercisable at the end of the period	6 years 22 days		4 years 1 month 20 days
Exercisable and expected to vest at the end of the period			4 years 11 months 19 days
Valuation assumptions
Risk-free interest rate (as a percent)			1.135%	2.40%
Expected volatility (as a percent)			87.00%	87.00%
Expected dividend yield (as a percent)	0.00%		0.00%	0.00%
Weighted average grant date fair value (in dollars per share)	$ 7.86		$ 160.65	$ 364.80
Stock options \| Minimum
Stock option plan
Vesting period			3 years
Exercise price
Outstanding at the beginning of the period (in dollars per share)	218.40	226.80	$ 226.80	226.80
Granted (in dollars per share)	10.59
Exercised (in dollars per share)				451.20
Forfeited (in dollars per share)	10.85		218.40	226.80
Outstanding at the end of the period (in dollars per share)	10.59		218.40	$ 226.80
Exercisable at the end of the period (in dollars per share)	$ 10.59		218.40
Exercisable and expected to vest at the end of the period (in dollars per share)			$ 218.40
Valuation assumptions
Risk-free interest rate (as a percent)	0.85%
Expected volatility (as a percent)	87.00%
Expected term	5 years		6 years	6 years
Stock options \| Maximum
Stock option plan
Vesting period			4 years
Exercise price
Outstanding at the beginning of the period (in dollars per share)	$ 1,149.60	$ 1,149.60	$ 1,149.60	$ 1,149.60
Granted (in dollars per share)	10.85
Exercised (in dollars per share)				508.80
Forfeited (in dollars per share)	1,149.60		1,149.60	1,149.60
Outstanding at the end of the period (in dollars per share)	1,149.60		1,149.60	$ 1,149.60
Exercisable at the end of the period (in dollars per share)	$ 1,149.60		1,149.60
Exercisable and expected to vest at the end of the period (in dollars per share)			$ 1,149.60
Valuation assumptions
Risk-free interest rate (as a percent)	1.69%
Expected volatility (as a percent)	88.00%
Expected term	6 years		6 years 3 months	6 years 3 months
2009 Stock Incentive Plan \| Stock options \| Minimum
Stock option plan
Stock options granted, exercise price as percentage of the fair market value of common stock at grant date			100.00%
Stock options granted to stockholder with specified ownership percentage, exercise price as percentage of the fair market value of common stock at grant date			110.00%
Stockholder's specified ownership percentage			10.00%
2009 Stock Incentive Plan \| Stock options \| Maximum
Stock option plan
Expiration period			10 years
2009 Stock Incentive Plan \| Common stock
Stock option plan
Number of shares available for issuance			14,271

Stock option plan (Details 2) - 1998 and 2009 Plans - USD ($)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Additional disclosures
Unrecognized compensation cost	$ 2,213,000	$ 4,005,000
Weighted average remaining service period for recognition of unrecognized compensation cost	2 years 1 month 20 days

Collaborations and grants (Details)		1 Months Ended		12 Months Ended
Collaborations and grants (Details)	Jan. 02, 2011 item	Nov. 30, 2011 USD ($) item	Aug. 31, 2011 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Jul. 31, 2008 USD ($)
Minimum
Grant revenue
Term of grant program				2 years
Maximum
Grant revenue
Term of grant program				5 years
Collaboration agreement \| Genzyme
Collaborations and grants
Deferred revenue			$ 7,500,000			$ 100,000,000
Selling price of undelivered agreements			8,800,000
Deferred revenue recognized			$ 79,000,000
Collaboration revenue recognized				$ 3,756,000	$ 90,012,000
Collaboration agreement \| Roche and SMA Foundation
Collaborations and grants
Deferred revenue		$ 30,000,000			30,000,000
Deferred revenue recognized				13,417,000
Collaboration revenue recognized				18,405,000	2,072,000
Number of compounds in preclinical development \| item		3
Number of significant deliverables \| item		2
Additional consideration receivable upon achievement of specified events		$ 30,000,000
Research period for applying technology		2 years
Collaboration agreement \| Roche and SMA Foundation \| Research and development event milestones \| Maximum
Collaborations and grants
Additional consideration receivable upon achievement of specified events				135,000,000
Collaboration agreement \| Roche and SMA Foundation \| Sales milestones \| Maximum
Collaborations and grants
Additional consideration receivable upon achievement of specified events				325,000,000
Early stage collaboration and discovery agreements
Collaborations and grants
Deferred revenue				3,032,000	7,232,000
Collaboration revenue recognized				$ 6,618,000	$ 6,878,000
Number of significant deliverables \| item	2
Early stage collaboration and discovery agreements \| Minimum
Collaborations and grants
Research period for applying technology				3 years
Early stage collaboration and discovery agreements \| Maximum
Collaborations and grants
Research period for applying technology				4 years
Early stage collaboration and discovery agreements \| Research and development event milestones
Collaborations and grants
Additional consideration receivable upon achievement of specified events				$ 143,000,000
Early stage collaboration and discovery agreements \| Sales milestones \| Maximum
Collaborations and grants
Additional consideration receivable upon achievement of specified events				$ 252,000,000

Income taxes (Details) - USD ($)	12 Months Ended
Income taxes (Details) - USD ($)	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of the U.S. statutory income tax rate to the entity's effective tax rate
Federal income tax (benefit) at statutory rate (as a percent)	34.00%	34.00%
State income tax benefit, net of federal benefit (as a percent)	3.80%	4.20%
Other (as a percent)	(2.00%)	(1.60%)
Increase to valuation allowance (as a percent)	(35.80%)	(45.90%)
Effective income tax rate (as a percent)	0.00%	(9.30%)
Tax benefit on sale of net operating losses and research and development credits in the New Jersey Transfer Program		$ 2,300,000
Deferred tax assets:
Amortization	$ 91,871	103,355
Depreciation	1,535,952	1,196,569
Accrued expense	1,208,846	321,925
Deferred revenue	6,962,506	15,738,180
Federal tax credits	5,383,092	5,734,074
State tax credits	1,094,833	1,495,773
Federal net operating losses	71,752,278	56,074,019
State net operating losses	7,619,606	5,024,189
Capitalized research and development costs	10,479,055	11,184,849
Other	742,341	600,059
Total gross deferred tax assets	106,870,380	97,472,992
Less valuation allowance	(106,870,380)	(97,472,992)
Net deferred tax assets	$ 0	$ 0

Income taxes (Details 2) - USD ($)	12 Months Ended
Income taxes (Details 2) - USD ($)	Dec. 31, 2012	Dec. 31, 2011
Income taxes
Change in valuation allowance	$ 9,397,000	$ 12,909,000
Federal
Operating loss carryforwards
Net operating loss carryforwards	211,036,000
State
Operating loss carryforwards
Net operating loss carryforwards	$ 128,276,000

Income taxes (Details 3)	Dec. 31, 2012 USD ($)
Federal
Credit carryforwards
Credit carryforwards	$ 5,383,000
State
Credit carryforwards
Credit carryforwards	$ 1,546,000

Income taxes (Details 4) - USD ($)	12 Months Ended
Income taxes (Details 4) - USD ($)	Dec. 31, 2012	Dec. 31, 2011
Operating loss carryforwards
Receivable for operating loss carryforwards sold under the Transfer program		$ 2,305,576
U.S. federal income tax rate (as a percent)	34.00%	34.00%
Unrecognized income tax benefits	$ 0
State
Operating loss carryforwards
Net operating loss carryforwards sold under the Technology Business Tax Certificate Transfer Program		$ 28,463,900

Commitments and contingencies (Details) - USD ($)	12 Months Ended
Commitments and contingencies (Details) - USD ($)	Dec. 31, 2012	Dec. 31, 2011
Commitments and contingencies
Rent expense	$ 739,000	$ 735,000
Future minimum lease payments
2013	879,000
2014	849,000
2015	849,000
2016	849,000
2017	849,000
Thereafter	1,113,000
Total future minimum lease payments	5,388,000
Funding agreement \| Wellcome Trust \| Maximum
Other contingencies
Development and regulatory milestone payments which the entity may be obligated to pay	$ 68,900,000

401(k) plan (Details) - USD ($)	12 Months Ended
401(k) plan (Details) - USD ($)	Dec. 31, 2012	Dec. 31, 2011
401(k) plan
Matching contribution up to the first 5% of employee's base salary (as a percent)	20.00%
Percentage of employee's base salary, matched by employer	5.00%
Expense recorded	$ 154,000	$ 177,000

Subsequent events (Details)			1 Months Ended		9 Months Ended		12 Months Ended
Subsequent events (Details)	Mar. 07, 2013 USD ($) shares	Mar. 05, 2013 shares	Jun. 30, 2013 shares	May 31, 2013 shares	Sep. 30, 2013 shares	Sep. 30, 2012 USD ($)	Dec. 31, 2012 USD ($) shares	Dec. 31, 2011 shares	Feb. 28, 2013 USD ($)
Subsequent events
Aggregate gross proceeds \| $						$ 29,354,752	$ 29,354,752
Restricted stock
Subsequent events
Number of shares of restricted stock granted					1,131,524
Stock options
Subsequent events
Shares granted					2,007,713		5,715	8,123
2013 Stock Incentive Plan \| Restricted stock
Subsequent events
Shares granted		735,324
2013 Stock Incentive Plan \| Stock options
Subsequent events
Shares granted		4,613
Series Four
Subsequent events
Aggregate gross proceeds \| $	$ 54,000,000
Shares issued and sold	4,497,035			375,000
Common stock
Subsequent events
Reverse stock split ratio	0.0083
Shares issued and sold			9,627,800
Common stock \| 2013 Stock Incentive Plan
Subsequent events
Number of shares authorized		739,937
Series Five
Subsequent events
Number of shares issued upon conversion	6,700,487
Series Five \| Warrants
Subsequent events
Number of shares issued upon conversion	2,095,515
Series Four and Series Five Convertible Preferred Stock
Subsequent events
Number of shares issued upon conversion			14,170,956
Convertible promissory notes
Subsequent events
Principal amount of convertible promissory notes issued \| $									$ 6,000,000
Convertible promissory notes \| Series Four
Subsequent events
Shares issued upon conversion of convertible promissory notes	502,919
Subsequent event \| 2013 Stock Incentive Plan
Subsequent events
Number of additional shares available for issuance		0
Subsequent event \| 2013 Stock Incentive Plan \| Restricted stock
Subsequent events
Number of shares of restricted stock granted		735,324
Subsequent event \| 2013 Stock Incentive Plan \| Stock options
Subsequent events
Shares granted		4,613
Subsequent event \| Series Four
Subsequent events
Aggregate gross proceeds \| $	$ 54,000,000
Shares issued and sold	4,497,035
Subsequent event \| Common stock
Subsequent events
Reverse stock split ratio	0.0083
Subsequent event \| Common stock \| 2013 Stock Incentive Plan
Subsequent events
Number of shares authorized		739,937
Subsequent event \| Series Five
Subsequent events
Shares issued and sold	6,700,487
Subsequent event \| Series Five \| Warrants
Subsequent events
Shares issued and sold	2,095,515
Subsequent event \| Series Four and Series Five Convertible Preferred Stock
Subsequent events
Number of shares issued upon conversion	1
Subsequent event \| Convertible promissory notes
Subsequent events
Principal amount of convertible promissory notes issued \| $									$ 6,000,000
Subsequent event \| Convertible promissory notes \| Series Four
Subsequent events
Shares issued upon conversion of convertible promissory notes	502,919

Selected quarterly financial data (unaudited) (Details)		1 Months Ended	3 Months Ended											9 Months Ended		12 Months Ended
Selected quarterly financial data (unaudited) (Details)	Mar. 07, 2013	Jul. 31, 2012 USD ($)	Sep. 30, 2013 USD ($) $ / shares	Jun. 30, 2013 USD ($) $ / shares	Mar. 31, 2013 USD ($) $ / shares	Dec. 31, 2012 USD ($) $ / shares	Sep. 30, 2012 USD ($) $ / shares	Jun. 30, 2012 USD ($) $ / shares	Mar. 31, 2012 USD ($) $ / shares	Dec. 31, 2011 USD ($) $ / shares	Sep. 30, 2011 USD ($) $ / shares	Jun. 30, 2011 USD ($) $ / shares	Mar. 31, 2011 USD ($) $ / shares	Sep. 30, 2013 USD ($) $ / shares	Sep. 30, 2012 USD ($) $ / shares	Dec. 31, 2012 USD ($) $ / shares	Dec. 31, 2011 USD ($) $ / shares
Selected quarterly financial data (unaudited)
Collaboration and grant revenue			$ 16,289,573	$ 6,854,212	$ 7,141,664	$ 6,640,090	$ 7,195,076	$ 7,585,177	$ 12,525,720	$ 9,362,686	$ 86,423,733	$ 4,772,720	$ 4,853,008	$ 30,285,449	$ 27,305,973	$ 33,946,063	$ 105,412,147
Operating expenses			20,565,188	21,307,148	15,718,073	12,674,520	14,250,383	15,083,384	18,745,957	16,983,976	18,315,064	19,682,313	19,848,797	57,590,409	48,079,724	60,754,244	74,830,150
Income (loss) from operations			(4,275,615)	(14,452,936)	(8,576,409)	(6,034,430)	(7,055,307)	(7,498,207)	(6,220,237)	(7,621,290)	68,108,669	(14,909,593)	(14,995,789)	(27,304,960)	(20,773,751)	(26,808,181)	30,581,997
Net income (loss)			(4,416,499)	(14,586,578)	(14,684,535)	(6,272,044)	(7,297,125)	(6,068,072)	(6,597,861)	$ (5,764,646)	$ 67,608,165	$ (15,388,398)	$ (15,550,607)	(33,687,612)	(19,963,058)	(26,235,102)	30,904,514
Gain on exchange of convertible preferred stock in connection with recapitalization		$ 160,000,000			3,390,750			159,954,069						3,390,750	159,954,069	159,954,069
Less beneficial conversion charge								(377,787)							(377,787)	(377,787)
Net income (loss) attributable to common stockholders			$ (4,416,499)	$ (14,586,578)	$ (29,542,553)	$ (6,372,044)	$ (7,297,125)	$ 153,508,210	$ (6,597,861)					$ (48,545,630)	$ 139,613,224	$ 133,341,180	$ 30,904,514
Basic net income (loss) attributable to common stockholders per share (in dollars per share) \| $ / shares			$ (0.19)	$ (5.51)	$ (6,527.30)	$ 1,380.13	$ (1,605.53)	$ 168.00	$ (5,992.61)	$ (5,290.57)	$ 52.39	$ (14,140.93)	$ (14,289.99)	$ (5.40)	$ 182.41	$ 219.76	$ 23.95
Diluted net income (loss) attributable to common stockholders per share (in dollars per share) \| $ / shares			$ (0.19)	$ (5.51)	$ (6,527.30)	$ 1,380.13	$ (1,605.53)	$ 48.29	$ (5,992.61)	$ (5,290.57)	$ 9.95	$ (14,140.93)	$ (14,289.99)	$ (5.40)	$ 39.41	$ 42.50	$ 4.55
Common stock
Selected quarterly financial data (unaudited)
Reverse stock split ratio	0.0083
Subsequent event \| Common stock
Selected quarterly financial data (unaudited)
Reverse stock split ratio	0.0083

Balance sheets - USD ($)	Sep. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 24,044,819	$ 2,725,702
Marketable securities	133,182,565
Prepaid expenses and other current assets	2,126,575	855,750
Grant and collaboration receivables, net	783,851	1,013,813
Total current assets	160,137,810	4,595,265
Fixed assets, net	6,942,956	8,280,037
Deposits and other assets	163,349	197,050
Total assets	167,244,115	13,072,352
Current liabilities:
Accounts payable and accrued expenses	10,205,493	7,023,971
Current portion of long-term debt	84,234	4,444,171
Deferred revenue	3,631,430	16,690,747
Total current liabilities	13,921,157	28,158,889
Deferred revenue, less current portion		741,667
Long-term debt, less current portion		438,810
Other long-term liabilities	2,290,445	2,549,719
Total liabilities	16,211,602	31,889,085
Stockholders' (deficit) equity:
Common stock, $0.001 par value. Authorized 17,000,000 shares; issued and outstanding 4,526 shares at December 31, 2012. Authorized 125,000,000 shares; issued and outstanding 23,803,282 shares at September 30, 2013	24,344	545
Additional paid-in capital	461,960,966	177,583,672
Accumulated other comprehensive loss	(40,467)
Accumulated deficit	(310,912,330)	(277,224,718)
Total stockholders' (deficit) equity	151,032,513	(99,640,501)
Total liabilities, convertible preferred stocks and stockholders' (deficit) equity	167,244,115	13,072,352
Series One convertible preferred stock
Stockholders' (deficit) equity:
Preferred stock		62,263,852
Series Two convertible preferred stock
Stockholders' (deficit) equity:
Preferred stock		18,182,129
Series Three convertible preferred stock
Stockholders' (deficit) equity:
Preferred stock		377,787
Preferred stock
Stockholders' (deficit) equity:
Preferred stock

Balance sheets (Parenthetical) - $ / shares	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001	$ 0.001
Common stock, Authorized shares	125,000,000	17,000,000	216,666
Common stock, issued shares	23,803,282	4,526	1,083
Common stock, outstanding shares	23,803,282	4,526	1,083
Series One convertible preferred stock
Preferred stock, designated shares		2,000,000
Preferred stock, issued shares		1,483,337
Preferred stock, outstanding shares		1,483,337
Series Two convertible preferred stock
Preferred stock, designated shares		13,750,000
Preferred stock, issued shares		10,701,405
Preferred stock, outstanding shares		10,701,405
Series Three convertible preferred stock
Preferred stock, designated shares		13,750,000
Preferred stock, issued shares		2,853,517
Preferred stock, outstanding shares		2,853,517
Preferred stock
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001	$ 0.001
Preferred stock, designated shares		156,995,095	156,995,095
Preferred stock, undesignated shares	5,000,000
Preferred stock, issued shares	0
Preferred stock, outstanding shares	0

Statements of operations - USD ($)	1 Months Ended	3 Months Ended											9 Months Ended		12 Months Ended
Statements of operations - USD ($)	Jul. 31, 2012	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Revenues:
Collaboration revenue													$ 27,395,315	$ 22,860,543	$ 28,779,078	$ 98,960,851
Grant revenue													2,890,134	4,445,430	5,166,985	6,451,296
Total revenues and non-cash cancellation revenue		$ 16,289,573	$ 6,854,212	$ 7,141,664	$ 6,640,090	$ 7,195,076	$ 7,585,177	$ 12,525,720	$ 9,362,686	$ 86,423,733	$ 4,772,720	$ 4,853,008	30,285,449	27,305,973	33,946,063	105,412,147
Operating expenses:
Research and development													39,855,115	36,688,786	46,138,868	58,677,081
General and administrative													17,735,294	11,390,938	14,615,376	16,153,069
Total operating expenses		20,565,188	21,307,148	15,718,073	12,674,520	14,250,383	15,083,384	18,745,957	16,983,976	18,315,064	19,682,313	19,848,797	57,590,409	48,079,724	60,754,244	74,830,150
Loss from operations		(4,275,615)	(14,452,936)	(8,576,409)	(6,034,430)	(7,055,307)	(7,498,207)	(6,220,237)	(7,621,290)	68,108,669	(14,909,593)	(14,995,789)	(27,304,960)	(20,773,751)	(26,808,181)	30,581,997
Interest (expense) income, net													(6,249,534)	(1,007,586)	(1,209,577)	(2,444,417)
Loss on extinguishment of debt													(129,963)
Other income (expense), net													(3,155)	1,818,279	1,782,656	461,358
Net loss		(4,416,499)	(14,586,578)	(14,684,535)	(6,272,044)	(7,297,125)	(6,068,072)	(6,597,861)	$ (5,764,646)	$ 67,608,165	$ (15,388,398)	$ (15,550,607)	(33,687,612)	(19,963,058)	(26,235,102)	30,904,514
Deemed dividend		4,416,499		18,248,768		7,297,125							(18,248,768)
Gain on exchange of convertible preferred stock in connection with recapitalization	$ 160,000,000			3,390,750			159,954,069						3,390,750	159,954,069	159,954,069
Less beneficial conversion charge							(377,787)							(377,787)	(377,787)
Net (loss) income attributable to common stockholders		$ (4,416,499)	$ (14,586,578)	$ (29,542,553)	$ (6,372,044)	$ (7,297,125)	$ 153,508,210	$ (6,597,861)					$ (48,545,630)	$ 139,613,224	$ 133,341,180	$ 30,904,514
Weighted-average shares outstanding:
Basic (in shares)													8,995,167	2,937	3,328	1,089
Weighted-average shares outstanding:
Diluted (in shares)													8,995,167	13,593	17,205	5,729
Net (loss) income per share applicable to common stockholders-basic (in dollars per share)		$ (0.19)	$ (5.51)	$ (6,527.30)	$ 1,380.13	$ (1,605.53)	$ 168.00	$ (5,992.61)	$ (5,290.57)	$ 52.39	$ (14,140.93)	$ (14,289.99)	$ (5.40)	$ 182.41	$ 219.76	$ 23.95
Net (loss) income per share applicable to common stockholders-diluted (in dollars per share)		$ (0.19)	$ (5.51)	$ (6,527.30)	$ 1,380.13	$ (1,605.53)	$ 48.29	$ (5,992.61)	$ (5,290.57)	$ 9.95	$ (14,140.93)	$ (14,289.99)	(5.40)	$ 39.41	42.50	$ 4.55
Pro forma net income per share applicable to common stockholders-(unaudited) (in dollars per share)													$ 2.73		$ 9.40
Pro forma weighted-average number of shares outstanding (unaudited)													17,812,651		14,188,161

Statements of comprehensive loss - USD ($)	3 Months Ended											9 Months Ended		12 Months Ended
Statements of comprehensive loss - USD ($)	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Statements of comprehensive loss
Net loss	$ (4,416,499)	$ (14,586,578)	$ (14,684,535)	$ (6,272,044)	$ (7,297,125)	$ (6,068,072)	$ (6,597,861)	$ (5,764,646)	$ 67,608,165	$ (15,388,398)	$ (15,550,607)	$ (33,687,612)	$ (19,963,058)	$ (26,235,102)	$ 30,904,514
Other comprehensive loss:
Unrealized loss on marketable securities												(40,467)			(3,606)
Comprehensive loss												$ (33,728,079)	$ (19,963,058)	$ (26,235,102)	$ 30,900,908

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

Statements of cash flows - USD ($)	9 Months Ended		12 Months Ended
Statements of cash flows - USD ($)	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Cash flows from operating activities
Net loss	$ (33,687,612)	$ (19,963,058)	$ (26,235,102)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,810,850	2,048,682	2,704,151
Change in valuation of warrant liability	3,158	(1,818,279)	(1,782,655)
Non-cash interest expense	6,048,580	204,422	225,730
Loss on extinguishment of debt	129,963
Share-based compensation expense	5,142,187	1,815,722	2,288,392
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(1,287,875)	2,250,089	2,452,430
Grant and collaboration receivables	229,962	75,698	230,315
Deposits and other assets	33,699	24,399	83,817
Accounts payable and accrued expenses	3,181,522	(4,748,005)	(6,025,483)
Other long-term liabilities	(262,432)	(68,432)	102,757
Deferred revenue	(13,800,984)	(16,711,980)	(21,972,143)
Net cash used in operating activities	(32,458,982)	(36,890,742)	(47,927,791)
Cash flows from investing activities
Purchases of fixed assets	(473,769)	(183,511)	(188,681)
Purchases of marketable securities	(139,730,579)
Maturities of marketable securities	6,507,547
Net cash used in investing activities	(133,696,801)	(183,511)	(188,681)
Cash flows from financing activities
Payments on long-term debt	(4,960,151)	(6,240,116)	(6,943,988)
Net proceeds from sale of Series One convertible preferred stock		29,354,752	29,354,752
Net proceeds from sale of Series Four convertible preferred stock	60,785,363
Net proceeds from initial public offering	131,649,688
Net cash provided by financing activities	187,474,900	23,114,636	22,410,764
Net (decrease) increase in cash and cash equivalents	21,319,117	(13,959,617)	(25,705,708)
Cash and cash equivalents, beginning of period	2,725,702	28,431,410	28,431,410
Cash and cash equivalents, end of period	24,044,819	14,471,793	2,725,702
Supplemental disclosure of cash information
Cash paid for interest	365,589	1,009,478	1,211,764
Supplemental disclosures of non-cash information related to investing and financing activities
Change in unrealized loss on marketable securities	(40,467)
Change in carry value of preferred securities resulting from recapitalization	$ 3,390,750	$ 159,576,282	$ 159,954,069

The Company	9 Months Ended	12 Months Ended
The Company	Sep. 30, 2013	Dec. 31, 2012
The Company
The Company	1. The Company PTC Therapeutics, Inc. (the Company or PTC) was incorporated as a Delaware corporation on March 31, 1998. The Company is a biopharmaceutical company focused on the discovery and development of orally administered, proprietary small-molecule drugs that target post-transcriptional control processes. The Company has devoted substantially all of its efforts to research and development, including clinical trials. The Company has not completed development of any drugs. The Company has not generated product revenue to date and is subject to a number of risks similar to those of other early stage companies, including dependence on key individuals, the difficulties inherent in the development of commercially usable products, the potential need to obtain additional capital necessary to fund the development of its products, and competition from other companies. As of September 30, 2013, the Company had an accumulated deficit of approximately $310.9 million. The Company has financed its operations to date primarily through the issuance and sale of its common stock in its initial public offering (see note 7 below), private placements of its convertible preferred stock, collaborations, bank debt, convertible debt financings, grant funding and clinical trial support from governmental and philanthropic organizations and patient advocacy groups in the disease areas addressed by the Company's product candidates. The Company believes that its existing cash, cash equivalents, including the Company's net proceeds from its initial public offering of common stock, and marketable securities provide for sufficient resources to fund its currently planned operations through the fourth quarter of 2015.	1. The Company PTC Therapeutics, Inc. (the Company or PTC) was incorporated as a Delaware corporation on March 31, 1998. The Company is a biopharmaceutical company focused on the discovery and development of orally administered, proprietary small-molecule drugs that target post-transcriptional control processes. The Company has devoted substantially all of its efforts to research and development, including clinical trials. The Company has not completed development of any drugs. The Company has not generated product revenue to date and is subject to a number of risks similar to those of other early stage companies, including dependence on key individuals, the difficulties inherent in the development of commercially usable products, the potential need to obtain additional capital necessary to fund the development of its products, and competition from other companies. As of December 31, 2012, the Company had an accumulated deficit of approximately $277.2 million. The Company has financed its operations to date primarily through private placements of its convertible preferred stock, collaborations, bank debt, convertible debt financings, grant funding and clinical trial support. The Company will need to obtain additional funding in connection with its ongoing operations. Additional financing may not be available to the Company. If the Company is unable to raise capital when needed or on attractive terms, the Company could be forced to delay, reduce or eliminate its research and development programs or any future commercialization efforts. As more fully described in Note 7, the Company completed a recapitalization of its outstanding convertible preferred stock in 2012 to enable the Company to raise additional capital. Use of estimates The preparation of financial statements in conformity with U.S. generally accepted accounting principles (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Summary of significant accounting policies

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Summary of significant accounting policies

Summary of significant accounting policies

2. Summary of significant accounting policies

Unaudited pro forma presentation

Basis of presentation

Use of estimates

Reverse stock split

Marketable securities

Revenue recognition

The Company's revenue is generated primarily through collaborative research and development and licensing agreements and grants.

Fair value of financial instruments

•: Level 1—Unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the balance sheet date.
•: Level 2—Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability

(i.e., interest rates, yield curves, etc.), and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs).

•: Level 3—Inputs are unobservable and reflect the Company's assumptions as to what market participants would use in pricing the asset or liability. The Company develops these inputs based on the best information available.

Warrant liability

Share-based compensation

2. Summary of significant accounting policies

Unaudited pro forma presentation

Segment and geographic information

Accounting changes

Cash equivalents

Fixed assets

Fixed assets are stated at cost. Depreciation is computed starting when the asset is placed into service on a straight-line basis over the estimated useful life of the related asset as follows:



Leasehold improvements		Lesser of useful life or lease term
Computer equipment and software		3 years
Furniture, fixtures, and lab equipment		3 to 7 years

Grant and collaboration receivables

Concentration of risks

Reverse stock split

Deferred rent

Revenue recognition

The Company's revenue is generated primarily through collaborative research and development and licensing agreements and grants.

For new collaborations or for material modifications made to existing collaborations, in 2011 and thereafter, the Company adopted the updated multiple element revenue recognition guidance. Under this new guidance, all non-contingent arrangement consideration is allocated to the identified units of accounting based on their relative selling price at inception of the collaboration arrangement. The Company derives the selling price using a combination of internal subjective and available external objective information, such as comparable transactions. The Company recognizes revenue commensurate with delivery, such as in the case with delivery of a license, or ratably over the course of a service period, as appropriate, such as in the case of ongoing research and development activities.

Research and development costs

Fair value of financial instruments

The Company follows the fair value measurement rules, which provides guidance on the use of fair value in accounting and disclosure for assets and liabilities when such accounting and disclosure is called for by other accounting literature. These rules establishes a fair value hierarchy for inputs to be used to measure fair value of financial assets and liabilities. This hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three levels: Level 1 (highest priority), Level 2, and Level 3 (lowest priority).

•: Level 1—Unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the balance sheet date.
•: Level 2—Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (i.e., interest rates, yield curves, etc.), and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs).
•: Level 3—Inputs are unobservable and reflect the Company's assumptions as to what market participants would use in pricing the asset or liability. The Company develops these inputs based on the best information available.

Beneficial conversion

Warrant liability

Warrants to purchase the Company's common stock with nonstandard antidilution provisions and preferred stock that include a put feature, regardless of the probability or likelihood that may conditionally obligate the issuer to ultimately transfer assets, are classified as liabilities and are recorded at their estimated fair value at each reporting period. Any change in fair value of these warrants is recorded as gain/(loss) on warrant valuation each reporting period in Other income on the Company's statement of operations.

Impairment of long-lived assets

Share-based compensation

Income taxes

Net income per share

Fair value of financial instruments and marketable securities

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Fair value of financial instruments and marketable securities

Fair value of financial instruments and marketable securities

3. Fair value of financial instruments and marketable securities

	December 31, 2012


	Total		Quoted prices in active markets for identical assets (level 1)		Significant other observable inputs (level 2)		Significant unobservable inputs (level 3)

Warrant liability	$	95,661	$	—	$	—	$	95,661

	September 30, 2013


	Total		Quoted prices in active markets for identical assets (level 1)		Significant other observable inputs (level 2)		Significant unobservable inputs (level 3)

Marketable securities	$	133,182,565	$	—	$	133,182,565	$	—
Warrant liability		98,819		—		—		98,819

The following is a summary of marketable securities accounted for as available-for-sale securities at September 30, 2013:

	September 30, 2013


			Gross Unrealized
	Amortized Cost		Gross Unrealized					Fair Value
	Amortized Cost		Gains		Losses			Fair Value

Commercial paper	$	24,978,703	$	20,527	$	—		$	24,999,230
U.S. corporate debt securities		108,244,329		19,642		(80,636	)		108,183,335

	$	133,223,032	$	40,169	$	(80,636	)	$	133,182,565

Marketable securities on the balance sheet at September 30, 2013 mature as follows:

	September 30, 2013


	Less than 12 Months		More than 12 Months

Commercial paper	$	24,999,230	$	—
U.S. corporate debt securities		57,824,657		50,358,678

Total Marketable securities	$	82,823,887	$	50,358,678

There were no marketable securities as of December 31, 2012.

Level 3 valuation

The table presented below is a summary of changes in the fair value of the Company's Level 3 valuation for warrant liability for the period ended September 30, 2013:

	Level 3 assets



Beginning balance as of December 31, 2012	$	95,661
Warrants issued in connection with convertible promissory notes		6,000,000
Deemed dividend		18,248,768
Exercise of warrants issued in connection with convertible promissory notes		(24,248,765	)
Change in fair value of warrant liability		3,155

Ending balance as of September 30, 2013	$	98,819

3. Fair value of financial instruments and investments

	December 31, 2011


	Total		Quoted prices in active markets for identical assets (level 1)	Significant other observable inputs (level 2)	Significant unobservable inputs (level 3)

Warrant liability	$	1,878,316	$—	$—	$1,878,316

	December 31, 2012


	Total		Quoted prices in active markets for identical assets (level 1)	Significant other observable inputs (level 2)	Significant unobservable inputs (level 3)

Warrant liability	$	95,661	$—	$—	$95,661

Level 3 valuation

The warrant liability is classified in Other long-term liabilities on the Company's balance sheet. The warrant liability is marked-to-market each reporting period with the change in fair value recorded as a gain or loss within Other income on the Company's statement of operations until the warrants are exercised, expire or other facts and circumstances lead the warrant liability to be reclassified as an equity instrument. The fair value of the warrant liability is determined at each reporting period by utilizing the Black-Scholes option pricing model.

The table presented below is a summary of changes in the fair value of the Company's Level 3 valuation for warrant liability for the years ended December 31, 2011 and 2012:

	Level 3 assets



Beginning balance January 1, 2011	$	2,340,263
Change in fair value of warrant liability		(461,947	)

Ending balance as of December 31, 2011		1,878,316
Change in fair value of warrant liability		(1,782,655	)

Ending balance as of December 31, 2012	$	95,661

Fair value of the warrant liability is estimated using an option-pricing model, which includes variables such as the expected volatility based on guideline public companies, the preferred stock value, and the estimated time to a liquidity event. The significant assumptions used in preparing the option pricing model for valuing the Company's warrants as of December 31, 2011 include (i) volatility (88%), (ii) risk free interest rate (0.25%-1.62%), (iii) strike price ($7.26-$16.00), (iv) fair value of preferred shares ($16) and (v) expected life (2-8 years). The significant assumptions used in preparing the option pricing model for valuing the Company's warrants as of December 31, 2012 include (i) volatility (87%), (ii) risk free interest rate (0.16%-1.18%), (iii) strike price ($16), (iv) fair value of preferred shares ($2.35) and (v) expected life (1-7 years). The fair value of the preferred shares declined significantly due to the recapitalization of the Company's outstanding convertible preferred stock in June 2012 as described in Note 7.

- Definition

+ References + Details

Other comprehensive income (loss) and accumulated other comprehensive items

9 Months Ended

Sep. 30, 2013

Other comprehensive income (loss) and accumulated other comprehensive items

Other comprehensive income (loss) and accumulated other comprehensive items

4. Other comprehensive income (loss) and accumulated other comprehensive items

Other comprehensive income (loss) includes changes in equity that are excluded from net income (loss), such as unrealized gains and losses on marketable securities.

The following table summarizes other comprehensive loss and the changes in accumulated other comprehensive items for the nine months ended September 30, 2013:

	Unrealized losses on marketable securities			Total accumulated other comprehensive items



Balance at December 31, 2012	$	—		$	—
Other comprehensive loss before reclassifications		(40,467	)		(40,467	)
Amounts reclassified from other comprehensive items		—			—

Other comprehensive loss		(40,467	)		(40,467	)

Balance at September 30, 2013	$	(40,467	)	$	(40,467	)

- Definition

The entire disclosure for comprehensive income, which includes, but is not limited to, 1) the amount of income tax expense or benefit allocated to each component of other comprehensive income, including reclassification adjustments, 2) the reclassification adjustments for each classification of other comprehensive income and 3) the ending accumulated balances for each component of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e689-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669619-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e640-108580

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e716-108580

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e709-108580

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e637-108580

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e681-108580

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Reclassification Adjustments
-URI http://asc.fasb.org/extlink&oid=6522872

+ Details

Accounts payable and accrued expenses

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Accounts payable and accrued expenses

Accounts payable and accrued expenses

5. Accounts payable and accrued expenses

Accounts payable and accrued expenses at December 31, 2012 and September 30, 2013 consist of the following:

	December 31, 2012		September 30, 2013



Employee compensation, benefits, and related accruals	$	3,096,475	$	3,659,084
Consulting and contracted research		2,515,678		3,556,350
Professional fees		559,228		1,532,458
Accounts payable		621,591		1,017,122
Other		230,999		440,479

	$	7,023,971	$	10,205,493

5. Accounts payable and accrued expenses

Accounts payable and accrued expenses at December 31, 2011 and 2012 consist of the following:

	December 31,


	2011		2012

Employee compensation, benefits, and related accruals	$	3,492,170	$	3,096,475
Consulting and contracted research		6,749,272		2,515,678
Professional fees		492,811		559,228
Accounts payable		1,878,109		621,591
Other		437,092		230,999

	$	13,049,454	$	7,023,971

Debt	9 Months Ended
Debt	Sep. 30, 2013
Debt
Debt	6. Debt In July 2013, the Company paid in full the outstanding principal and interest of $2.6 million due under promissory notes issued in connection with a $25 million secured debt facility with a syndicate of two lenders. The notes were secured by substantially all of the Company's assets except for intellectual property and carried a fixed interest rate of 13.65%. As a result of this transaction, the Company recorded a loss on extinguishment of debt of $0.1 million on the Company's statement of operations for the nine months ended September 30, 2013, The loss on extinguishment of debt primarily represented the write off of related deferred financing costs, the acceleration of recognition of debt extinguishment fees and the prepayment premium payable.

Capital structure

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Capital structure

Capital structure

7. Capital structure

2013 Recapitalization

The rights and preferences of the shares of Series Four and Series Five are as follows:

Dividends—The holders of Series Four and Series Five, in preference to the holders of common stock, are entitled to noncumulative dividends when and if declared by the Board of Directors.

In May 2013, the Company issued and sold an additional 375,000 shares of Series Four, at a price per share of $12.00, for an aggregate purchase price of $4.5 million.

Common stock

Initial public offering

Upon closing the initial public offering, all outstanding shares of the Series Four and Series Five were converted into 14,170,956 shares of common stock.

Warrants

The following is a summary of the Company's outstanding warrants as of December 31, 2012:

		Exercise price



Series Two	24,712	$	16.00	2014
Series Two	50,000	$	16.00	2017
Series Two	56,250	$	16.00	2019 and 2020
Common stock	645	$	2,520	2013 and 2014

The following is a summary of the Company's outstanding warrants as of September 30, 2013:

	Warrant shares	Exercise price		Expiration



Common stock	3,088	$	128.00	2014
Common stock	6,250	$	128.00	2017
Common stock	7,030	$	128.00	2019 and 2020
Common stock	645	$	2,520	2013 and 2014

7. Capital structure

Convertible preferred stock prior to 2012 recapitalization

The rights and preferences of the shares of Series A, Series B, Series C, Series D, Series E, Series E-2, Series F, Series F-2 and Series G were as follows:

Recapitalization

In connection with the recapitalization, the Company sold 1,483,337 shares of Series One for aggregate gross proceeds of approximately $29.7 million.

The rights and preferences of the shares of Series One, Two and Three are as follows:

Warrants

The following is a summary of the Company's outstanding warrants as of December 31, 2011:

		Exercise price



Series E convertible preferred stock	54,465	$	7.26	2014
Series F convertible preferred stock	50,000	$	16.00	2017
Series F-2 convertible preferred stock	56,250	$	16.00	2019 and 2020
Common stock	645	$	2,520	2013 and 2014

In connection with the recapitalization, all of the Series E, F, and F-2 outstanding warrants became warrants to purchase Series Two.

The following is a summary of the Company's outstanding warrants as of December 31, 2012:

		Exercise price



Series 2 convertible preferred stock	24,712	$	16.00	2014
Series 2 convertible preferred stock	50,000	$	16.00	2017
Series 2 convertible preferred stock	56,250	$	16.00	2019 and 2020
Common stock	645	$	2,520	2013 and 2014

- Definition

+ References

+ Details

Net income (loss) per share

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Net income (loss) per share

Net income (loss) per share

8. Net income (loss) per share

The following tables set forth the computation of basic and diluted net income (loss) per share for common stockholders:

	Nine months ended September 30,


	2012			2013

Numerator
Net loss	$	(19,963,058	)	$	(33,687,612	)
Deemed dividend		—			(18,248,768	)
Gain on exchange of convertible preferred stock in connection with recapitalization		159,954,069			3,390,750
Less beneficial conversion charge		(377,787	)		—
Less net income attributable to participating securities		(139,077,495	)		—

Net income (loss) attributable to common stockholders	$	535,729		$	(48,545,630	)

Denominator
Denominator for basic net income (loss) per share		2,937			8,995,167
Effect of dilutive securities
Series Three convertible preferred stock		10,656			—

Denominator for diluted net income (loss) per share		13,593			8,995,167

Net income (loss) per share:
Basic	$	182.41		$	(5.40	)*

Diluted	$	39.41		$	(5.40	)*

* In the nine months ended September 30, 2013, the Company experienced a net loss and therefore did not report any dilutive share impact.

	As of September 30,


	2012		2013

Stock Options		44,218		1,987,860
Unvested restricted stock		—		1,113,807

Total		44,218		3,101,667

8. Earnings per share

The following table sets forth the computation of basic and diluted earnings per share for common stockholders:

Net income per share

	Year ended December 31


	2011			2012

Numerator
Net income (loss)	$	30,904,514		$	(26,235,102	)
Gain on exchange of convertible preferred stock in connection with recapitalization		—			159,954,069
Less beneficial conversion charge		—			(377,787	)
Less net income attributable to participating preferred stock		(30,878,445	)		(132,609,918	)

Net income attributable to common stockholders	$	26,069		$	731,262

Denominator
Denominator for basic earnings per share		1,089			3,328
Effect of dilutive securities:
Employee stock options		4,640			—
Series 3 convertible preferred stock		—			13,877

Denominator for diluted earnings per share		5,729			17,205

Net income per share:
Basic		23.95			219.76

Diluted		4.55			42.50

Stock option plan

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Stock option plan

Stock option plan

9. Stock option plan

A summary of stock option activity is as follows:

(in thousands)			Exercise price	Weighted- average exercise price		Weighted- average remaining contractual term	Aggregate intrinsic value




Outstanding at December 31, 2012	42,394		$218.40-$1,149.60	$	469.48
Granted	2,007,713		$10.59-$10.85	$	10.85
Exercised	—		—		—
Forfeited	(62,247	)	$10.85-$1,149.60	$	17.10

Outstanding at September 30, 2013	1,987,860		$10.59-$1,149.60	$	20.44	9.51 years	$	20,652

Exercisable at September 30, 2013	61,834		$10.59-$1,149.60	$	290.39	6.06 years	$	265

The fair value of grants made in the period ended September 30, 2013 was contemporaneously estimated on the date of grant using the following assumptions:

		Nine months ended September 30, 2013



Risk-free interest rate		0.85%-1.69%
Expected volatility		87%-88%
Expected term		5.00 to 6.00 years
Expected dividend yield		0.0%

The Company assumed no expected dividends for all grants. The weighted average grant date fair value of options granted during the nine month period ended September 30, 2013 was $7.86 per share.

The following table summarizes information on the Company's restricted stock:

	Restricted stock


	Number of shares			Weighted average grant date fair value

January 1, 2013		—			—
Granted		1,131,524		$	10.68
Vested		—		$	—
Forfeited		(17,717	)	$	10.63

Unvested at September 30, 2013		1,113,807		$	10.68

The Company recorded share-based compensation expense in the statement of operations as follows:

	Nine months ended September 30,


	2012		2013

Research and development	$	653,462	$	1,377,640
General and administrative		1,162,260		3,764,547

Total	$	1,815,722	$	5,142,187

9. Stock option plan

A summary of stock option activity is as follows:

	Number of options		Exercise price	Weighted- average exercise price		Weighted- average remaining contractual term



Outstanding at December 31, 2010	39,557		$226.80-$1,149.60	$	547.20
Granted	8,123		$490.80	$	490.80
Exercised	(11	)	$451.20-$508.80	$	459.60
Forfeited	(875	)	$226.80-$1,149.60	$	757.20

Outstanding at December 31, 2011	46,794		$226.80-$1,149.60	$	532.80	5.74 years
Granted	5,715		$218.40	$	218.40
Exercised	—
Forfeited	(10,115	)	$218.40-$1,149.60	$	604.80

Outstanding at December 31, 2012	42,394		$218.40-$1,149.60	$	474.00	5.02 years	—

Exercisable at December 31, 2012	33,414		$218.40-$1,149.60	$	482.40	4.14 years	—

Exercisable and expected to vest at December 31, 2012	42,184		$218.40-$1,149.60	$	476.40	4.97 years	—

The fair value of grants made in the years ended December 31, 2011 and 2012 was contemporaneously estimated on the date of grant using the following assumptions:





Risk-free interest rate	2.40%	1.135%
Expected volatility	87%	87%
Expected term	6.00-6.25 years	6.00-6.25 years

Collaboration Revenue	9 Months Ended
Collaboration Revenue	Sep. 30, 2013
Collaboration Revenue.
Collaboration Revenue	10. Collaboration revenue On August 8, 2013, the Company announced the selection of a development candidate in its spinal muscular atrophy collaboration with F. Hoffman-La Roche Ltd and Hoffman-La Roche Inc. (Roche) and the Spinal Muscular Atrophy Foundation. The achievement of this milestone triggered a $10.0 million payment to the Company from Roche. The Company considered this milestone event substantive because the applicable criteria of its revenue recognition policy (see Note 2) would be satisfied and recorded it as collaboration revenue for the nine months ended September 30, 2013.

Selected quarterly financial data

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Selected quarterly financial data

Selected quarterly financial data

11. Selected quarterly financial data

	For the quarters ending


	March 31			June 30			September 30

2012:
Collaboration and grant revenue	$	12,525,720		$	7,585,177		$	7,195,076
Operating expenses		18,745,957			15,083,384			14,250,383
Income (loss) from operations		(6,220,237	)		(7,498,207	)		(7,055,307	)
Net income (loss)		(6,597,861	)		(6,068,072	)		(7,297,125	)
Gain on exchange of convertible preferred stock in connection with recapitalization		—			159,954,069			—
Less beneficial conversion charge		—			(377,787	)		—
Net income (loss) attributable to common stockholders		(6,597,861	)		153,508,210			(7,297,125	)
Basic net income (loss) per common share(1)	$	(5,992.61	)	$	168.00		$	(1,605.53	)
Diluted net income (loss) per common share(1)	$	(5,992.61	)	$	48.29		$	(1,605.53	)
2013:
Collaboration and grant revenue	$	7,141,664		$	6,854,212		$	16,289,573
Operating expenses		15,718,073			21,307,148			20,565,188
Income (loss) from operations		(8,576,409	)		(14,452,936	)		(4,275,615	)
Net income (loss)		(14,684,535	)		(14,586,578	)		(4,416,499	)
Deemed dividend		(18,248,768	)		—			—
Gain on exchange of convertible preferred stock in connection with recapitalization		3,390,750			—			—
Net income (loss) attributable to common stockholders		(29,542,553	)		(14,586,578	)		(4,416,499	)
Basic net income (loss) per common share(1)	$	(6,527.30	)	$	(5.51	)	$	(0.19	)
Diluted net income (loss) per common share(1)	$	(6,527.30	)	$	(5.51	)	$	(0.19	)

(1) The amounts were computed independently for each quarter and the sum of the quarters may not total the annual amounts.

15. Selected quarterly financial data (unaudited)

	For the quarters ending


	March 31			June 30			September 30			December 31

2011:
Collaboration and grant revenue	$	4,853,008		$	4,772,720		$	86,423,733		$	9,362,686
Operating expenses		19,848,797			19,682,313			18,315,064			16,983,976
Income (loss) from operations		(14,995,789	)		(14,909,593	)		68,108,669			(7,621,290	)
Net income (loss)		(15,550,607	)		(15,388,398	)		67,608,165			(5,764,646	)
Basic net income (loss) per common share(1)	$	(14,289.99	)	$	(14,140.93	)	$	52.39		$	(5,290.57	)
Diluted net income (loss) per common share(1)	$	(14,289.99	)	$	(14,140.93	)	$	9.95		$	(5,290.57	)
2012:
Collaboration and grant revenue	$	12,525,720		$	7,585,177		$	7,195,076		$	6,640,090
Operating expenses		18,745,957			15,083,384			14,250,383			12,674,520
Income (loss) from operations		(6,220,237	)		(7,498,207	)		(7,055,307	)		(6,034,430	)
Net income (loss)		(6,597,861	)		(6,068,072	)		(7,297,125	)		(6,272,044	)
Gain on exchange of convertible preferred stock in connection with recapitalization		—			159,954,069			—			—
Less beneficial conversion charge		—			(377,787	)		—			—
Net income (loss) attributable to common stockholders		(6,597,861	)		153,508,210			(7,297,125	)		(6,372,044	)
Basic net income (loss) attributable to common stockholders per share	$	(5,992.61	)	$	168.00		$	(1,605.53	)	$	(1,380.13	)
Diluted net income (loss) attributable to common stockholders per share(1)	$	(5,992.61	)	$	48.29		$	(1,605.53	)	$	(1,380.13	)

(1) The amounts were computed independently for each quarter and the sum of the quarters may not total the annual amounts.

Subsequent events	9 Months Ended	12 Months Ended
Subsequent events	Sep. 30, 2013	Dec. 31, 2012
Subsequent events
Subsequent events	12. Subsequent events The Company continues to advance the development of its spinal muscular atrophy (SMA) collaboration with Roche and the SMA Foundation. The collaboration was initially funded in part by the SMA Foundation. In December 2011, the Company announced a partnership with Roche in the collaboration which provided an upfront payment of $30 million, up to $460 million in milestone payments and royalties on future sales. In August 2013, a development candidate for the program was announced which triggered a $10 million milestone payment from Roche. In January 2014, a Phase 1 clinical program was initiated which triggered a $7.5 million milestone payment from Roche. Roche is responsible for pursuing clinical development of compounds from the program consistent with a governance structure that includes representation from the Company and the SMA Foundation and then commercialization of these compounds. On December 13, 2013, the Compensation Committee of the Company's Board of Directors approved the waiver of the remaining performance vesting triggers with respect to performance-based stock options granted to the Company's executive officers during 2013, such that 25% of the shares underlying such stock options vested on December 31, 2013, and an additional 2.0833% of the shares underlying such stock options will vest at the end of each successive month following December 31, 2013 until December 31, 2016. Approximately $0.6 million is expected to be recorded as share-based compensation in the fourth quarter of 2013 as a result of the modification of these stock options, which represents the incremental fair value of such modified stock options computed in accordance with ASC Topic 718 as of the date of modification.	14. Subsequent events On January 29, 2013, the Company entered into a financing arrangement with certain existing investors providing for the issuance by the Company of convertible promissory notes and warrants to purchase shares of Series One and Series Two. The Company issued convertible promissory notes in January and February 2013 in an aggregate principal amount of $6 million under this financing arrangement. This financing was closed in anticipation of an additional financing event, which is described in the next paragraph below. On March 7, 2013, the Company closed a private placement of a new series of convertible preferred stock that resulted in another recapitalization event. In this private placement, the Company issued and sold an aggregate of 4,497,035 shares of Series Four senior preferred stock (Series Four) for an aggregate purchase price of approximately $54 million. In addition, the Company issued an aggregate of 502,919 shares of Series Four upon conversion of the convertible promissory notes described above that it originally issued in January and February 2013. In connection with this private placement, the Company effected a one-for-120 reverse stock split of its common stock and an exchange of outstanding shares of Series One, Series Two and Series Three into an aggregate of 6,700,487 shares of a new series of Series Five junior preferred stock (Series Five). In addition, the Company issued an aggregate of 2,095,515 shares Series Five upon the automatic exercise of the Series One and Series Two warrants described above that it originally issued in January 2013. The Company expects to account for the March 2013 Series Four financing and recapitalization as an extinguishment of its Series One, Series Two and Series Three stock and will record a gain or loss for the difference between the fair value of the new Series Four and Series Five shares over the carrying value of the Series One, Two and Three shares extinguished. The warrants to purchase shares of Series One, Two and Three issued in connection with the January 2013 convertible note financing will be recorded as a liability and remeasured each reporting period. The Company expects to record a debt discount resulting from the allocation of proceeds to the fair value of the warrants and reflect the discount as interest expense during the quarter ended March 31, 2013. Valuation—The value of the Company was estimated using the PWERM. The PWERM considered the most significant near-term driver of value for the Company as the ability to file a MAA with the EMA for conditional approval of ataluren for the treatment of nmDMD. The Company has initiated a confirmatory Phase 3 clinical trial of ataluren for the treatment of nmDMD. If favorable, the results of the confirmatory Phase 3 clinical trial could serve as the basis for full approval by the EMA and the FDA of ataluren for the treatment of nmDMD in the European Union and the United States. The remaining scenarios in the PWERM related to funding the completion of the confirmatory Phase 3 clinical trial of ataluren for the treatment of nmDMD. After identifying the various potential liquidity scenarios and their likely timing, a pre-money enterprise value was assigned to each scenario based on a combination of management's guidance and recent trends in the capital markets. The resulting enterprise value for each liquidity event was divided by the total shares that would be outstanding under each scenario to arrive at a price per share for the common and preferred classes of stock. Each scenario was then assigned an outcome probability based on management's estimates. The resulting probability weighted share values were then discounted to present value at a rate that reflects general industry risks (but not Company specific risks). The rights and preferences of the shares of Series Four and Five are as follows: Dividends—The holders of Series Four and Series Five, in preference to the holders of common stock, are entitled to noncumulative dividends when and if declared by the Board of Directors. Liquidation—Upon the liquidation, dissolution, reorganization or winding-up of the Company, the holders of Series Four will be entitled to receive, before any distribution or payment is made to any other class of security, an amount equal to the original issuance price, plus all declared, but unpaid, dividends. To the extent there are excess assets to distribute, the holders of Series Five will be entitled to receive, before any distribution or payment is made to the holders of the common stock, an amount equal to the stated liquidation preference, plus all declared, but unpaid, dividends. To the extent there are remaining assets to distribute, the holders of common stock will be entitled to receive such remaining assets. Voting—Each holder of Series Four and Series Five are entitled to cast the number of votes into which such holder's shares would convert. Except as required by law, holders of common stock have limited voting rights. Additionally, except as required by law, and except in certain enumerated circumstances, holders of Series Four and Series Five shall vote together with the holders of common stock as a single class. Conversion—Each share of Series Four and Series Five is convertible at any time at the option of the holder into one share of common stock. These conversion ratios are subject to adjustment for certain dilutive events, including certain types of stock splits or stock dividends or future recapitalizations. On March 5, 2013, the Company's Board of Directors approved the 2013 Stock Incentive Plan, which provides for the granting of stock option awards, stock appreciation rights, restricted stock, restricted stock units and other stock-based in the aggregate of 739,937 shares of Common Stock (calculated after the one-for-120 reverse stock split of its common stock). On March 5, 2013, the Board approved a grant of 735,324 shares of restricted stock and 4,613 stock options. There are no additional shares available for issuance under this plan.

Summary of significant accounting policies (Policies)	9 Months Ended	12 Months Ended
Summary of significant accounting policies (Policies)	Sep. 30, 2013	Dec. 31, 2012
Summary of significant accounting policies
Basis of Presentation	Basis of presentation The accompanying financial information as of September 30, 2013 and for the nine months ended September 30, 2012 and 2013 has been prepared by the Company, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). Certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles in the United States (GAAP) have been condensed or omitted pursuant to such rules and regulations. These interim financial statements should be read in conjunction with the Company's audited financial statements as of December 31, 2012 and notes thereto included in the final prospectus related to the Company's initial public offering. In the opinion of management, the unaudited financial information as of September 30, 2013 and the nine months ended September 30, 2012 and 2013 reflects all adjustments, which are normal recurring adjustments, necessary to present a fair statement of financial position, results of operations and cash flows. The results of operations for the nine month period ended September 30, 2013 is not necessarily indicative of the results to be expected for the year ended December 31, 2013 or for any other interim period or for any other future year.
Use of estimates	Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Reverse stock split	Reverse stock split On March 7, 2013, the Company effected a one-for-120 reverse stock split of its common stock, pursuant to which each 120 shares of the Company's outstanding common stock were reclassified and combined into one share of common stock. All common stock share and per share references in the financial statements and notes thereto have been restated to reflect the reverse stock split on a retroactive basis.	Reverse stock split As a result of the one-for-120 reverse stock split that was effected on March 7, 2013, each 120 shares of the Company's outstanding common stock were reclassified and combined into one share of common stock. All references to common stock have been restated to reflect the reverse stock split on a retroactive basis.
Marketable Securities	Marketable securities Management determines the classification of marketable securities at the time of purchase and reevaluates such designation as of each balance sheet date. Marketable securities are classified as available-for-sale and carried at fair value, with any unrealized gain or loss recorded as a separate component of stockholders' (deficit) equity.
Revenue recognition	Revenue recognition The Company recognizes revenue when amounts are realized or realizable and earned. Revenue is considered realizable and earned when the following criteria are met: (1) persuasive evidence of an arrangement exists; (2) delivery has occurred or services have been rendered; (3) the price is fixed or determinable; and (4) collection of the amounts due are reasonably assured. The Company's revenue is generated primarily through collaborative research and development and licensing agreements and grants. The terms of these agreements typically include payments to the Company of one or more of the following: nonrefundable, upfront license fees; milestone payments; research funding and royalties on future product sales. In addition, the Company generates service revenue through agreements that generally provide for fees for research and development services and may include additional payments upon achievement of specified events. For existing collaborations entered into prior to the adoption in 2011 of the revised multiple element revenue recognition guidance described below, the Company recognized revenue consistent with the approach established at the inception of each arrangement. For these existing collaborations, where the Company has continuing involvement, the Company recorded nonrefundable, upfront fees as deferred revenue and recognizes revenue on a straight-line basis as collaboration revenue over the expected performance period. For new collaborations or for material modifications made to existing collaborations, in 2011 and thereafter, the Company adopted the updated multiple element revenue recognition guidance. Under this guidance, all non-contingent arrangement consideration is allocated to the identified units of accounting based on their relative selling price at inception of the collaboration arrangement. The Company derives the selling price using a combination of internal subjective and available external objective information, such as comparable transactions. The Company recognizes revenue commensurate with delivery, such as in the case with delivery of a license, or ratably over the course of a service period, as appropriate, such as in the case of ongoing research and development activities. The Company evaluates all contingent consideration earned, such as a milestone payment, using the criteria as provided by the Financial Accounting Standards Board (FASB) guidance on the milestone method of revenue recognition. At the inception of a collaboration arrangement, the Company evaluates if milestone payments are substantive. The criteria requires that (1) the Company determines if the milestone is commensurate with either its performance to achieve the milestone or the enhancement of value resulting from its activities to achieve the milestone; (2) the milestone be related to past performance; and (3) the milestone be reasonable relative to all deliverable and payment terms of the collaboration arrangement. If these criteria are met then the contingent milestones can be considered as substantive milestones and will be recognized as revenue in the period that the milestone is achieved. The Company recognizes royalties as earned in accordance with the terms of various research and collaboration agreements. If not substantive, the contingent consideration is allocated to the existing units of accounting based on relative selling price and recognized following the same basis previously established for the associated unit of accounting. The Company recognizes revenue for reimbursements of research and development costs under collaboration agreements as the services are performed. The Company records these reimbursements as revenue and not as a reduction of research and development expenses as the Company has the risks and rewards as the principal in the research and development activities.	Revenue recognition The Company recognizes revenue when amounts are realized or realizable and earned. Revenue is considered realizable and earned when the following criteria are met: (1) persuasive evidence of an arrangement exists; (2) delivery has occurred or services have been rendered; (3) the price is fixed or determinable; and (4) collection of the amounts due are reasonably assured. The Company's revenue is generated primarily through collaborative research and development and licensing agreements and grants. The terms of these agreements typically include payments to the Company of one or more of the following: nonrefundable, upfront license fees; milestone payments; research funding and royalties on future product sales. In addition, the Company generates service revenue through agreements that generally provide for fees for research and development services and may include additional payments upon achievement of specified events. For existing collaborations entered into prior to the adoption in 2011 of the revised multiple element revenue recognition guidance described below, the Company recognized revenue consistent with the approach established at the inception of each arrangement. For these existing collaborations, where the Company has continuing involvement, the Company recorded nonrefundable, upfront fees as deferred revenue and recognizes revenue on a straight-line basis as collaboration revenue over the expected performance period. For new collaborations or for material modifications made to existing collaborations, in 2011 and thereafter, the Company adopted the updated multiple element revenue recognition guidance. Under this new guidance, all non-contingent arrangement consideration is allocated to the identified units of accounting based on their relative selling price at inception of the collaboration arrangement. The Company derives the selling price using a combination of internal subjective and available external objective information, such as comparable transactions. The Company recognizes revenue commensurate with delivery, such as in the case with delivery of a license, or ratably over the course of a service period, as appropriate, such as in the case of ongoing research and development activities. The Company evaluates all contingent consideration earned, such as a milestone payment, using the criteria as provided by the Financial Accounting Standards Board (FASB), guidance on the milestone method of revenue recognition. At the inception of a collaboration arrangement, the Company evaluates if milestone payments are substantive. The criteria requires that (1) the Company determines if the milestone is commensurate with either its performance to achieve the milestone or the enhancement of value resulting from our activities to achieve the milestone; (2) the milestone be related to past performance; and (3) the milestone be reasonable relative to all deliverable and payment terms of the collaboration arrangement. If these criteria are met then the contingent milestones can be considered as substantive milestones and will be recognized as revenue in the period that the milestone is achieved. The Company recognizes royalties as earned in accordance with the terms of various research and collaboration agreements. If not substantive, the contingent consideration is allocated to the existing units of accounting based on relative selling price and recognized following the same basis previously established for the associated unit of accounting. The Company recognizes revenue for reimbursements of research and development costs under collaboration agreements as the services are performed. The Company records these reimbursements as revenue and not as a reduction of research and development expenses as the Company has the risks and rewards as the principal in the research and development activities.
Fair value of financial instruments	Fair value of financial instruments The Company follows the fair value measurement rules, which provides guidance on the use of fair value in accounting and disclosure for assets and liabilities when such accounting and disclosure is called for by other accounting literature. These rules establish a fair value hierarchy for inputs to be used to measure fair value of financial assets and liabilities. This hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three levels: Level 1 (highest priority), Level 2, and Level 3 (lowest priority). • Level 1—Unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the balance sheet date. • Level 2—Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (i.e., interest rates, yield curves, etc.), and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs). • Level 3—Inputs are unobservable and reflect the Company's assumptions as to what market participants would use in pricing the asset or liability. The Company develops these inputs based on the best information available. Cash equivalents are reflected in the accompanying financial statements at fair value. The carrying amount of grant and collaboration receivables, accounts payable and accrued expenses, and debt approximates fair value due to the short-term nature of those instruments.	Fair value of financial instruments The Company follows the fair value measurement rules, which provides guidance on the use of fair value in accounting and disclosure for assets and liabilities when such accounting and disclosure is called for by other accounting literature. These rules establishes a fair value hierarchy for inputs to be used to measure fair value of financial assets and liabilities. This hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three levels: Level 1 (highest priority), Level 2, and Level 3 (lowest priority). • Level 1—Unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the balance sheet date. • Level 2—Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 2 inputs include quoted prices for similar assets and liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability (i.e., interest rates, yield curves, etc.), and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market corroborated inputs). • Level 3—Inputs are unobservable and reflect the Company's assumptions as to what market participants would use in pricing the asset or liability. The Company develops these inputs based on the best information available. Cash equivalents and investments are reflected in the accompanying financial statements at fair value. The carrying amount of grant and collaboration receivables and accounts payable and accrued expenses approximates fair value due to the short-term nature of those instruments.
Warrant liability	Warrant liability Warrants to purchase the Company's common stock with nonstandard antidilution provisions and preferred stock that include a put feature, regardless of the probability or likelihood that may conditionally obligate the issuer to ultimately transfer assets, are classified as liabilities and are recorded at their estimated fair value at each reporting period. Any change in fair value of these warrants is recorded as gain (loss) on warrant valuation each reporting period in Other income (expense), net on the Company's statement of operations.	Warrant liability Warrants to purchase the Company's common stock with nonstandard antidilution provisions and preferred stock that include a put feature, regardless of the probability or likelihood that may conditionally obligate the issuer to ultimately transfer assets, are classified as liabilities and are recorded at their estimated fair value at each reporting period. Any change in fair value of these warrants is recorded as gain/(loss) on warrant valuation each reporting period in Other income on the Company's statement of operations.
Share-based compensation	Share-based compensation The Company measures the cost of employee services received in exchange for an award of equity instruments based on the grant date fair value of the award. For service type awards, share-based compensation expense is recognized on a straight-line basis over the period during which the employee is required to provide service in exchange for the entire award. For awards that vest or begin vesting upon achievement of a performance condition, the Company estimates the likelihood of satisfaction of the performance condition and recognizes compensation expense when achievement of the performance condition is deemed probable using an accelerated attribution model. The fair value of options is calculated using the Black-Scholes option pricing model to determine the fair value of stock options on the date of grant based on key assumptions, such as expected volatility and expected term. As a new public company, the Company does not have sufficient history to estimate the volatility of its common stock price or the expected life of the options. The Company calculates expected volatility based on reported data for similar publicly traded companies for which historical information is available and will continue to do so until the historical volatility of its common stock is sufficient to measure expected volatility for future option grants.	Share-based compensation The Company measures the cost of employee services received in exchange for an award of equity instruments based on the grant date fair value of the award. That cost is recognized on a straight-line basis over the period during which the employee is required to provide service in exchange for the entire award. The fair value of options is calculated using the Black-Scholes option pricing model to determine the fair value of stock options on the date of grant based on key assumptions such as stock price, expected volatility and expected term. The Company's estimates of these assumptions are primarily based on third-party valuations, historical data, peer company data and judgment regarding future trends and factors. The Company utilized various valuation methodologies in accordance with the framework of the 2004 American Institute of Certified Public Accountants Technical Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation, to estimate the fair value of its stock. The methodologies included an option pricing method to estimate the Company's underlying equity value, and a methodology that determined an estimated value under an initial public offering (IPO) scenario and a sale scenario based upon an assessment of the probability of occurrence of each scenario. Each valuation methodology includes estimates and assumptions that require the Company's judgment. These estimates include assumptions regarding future performance, including the completion of clinical trials and the time to complete an IPO or sale of the Company. As with any valuation, significant changes to the key assumptions used in the valuations could result in different fair values of common stock at each valuation date.

- Definition

Disclosure of accounting policy for revenue recognition. If the entity has different policies for different types of revenue transactions, the policy for each material type of transaction is generally disclosed. If a sales transaction has multiple element arrangements (for example, delivery of multiple products, services or the rights to use assets) the disclosure may indicate the accounting policy for each unit of accounting as well as how units of accounting are determined and valued. The disclosure may encompass important judgment as to appropriateness of principles related to recognition of revenue. The disclosure also may indicate the entity's treatment of any unearned or deferred revenue that arises from the transaction.

+ References + Details

Fair value of financial instruments and marketable securities (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Fair value of financial instruments and marketable securities

Schedule of financial assets that are required to be measured at fair value on a recurring basis

	December 31, 2012


	Total		Quoted prices in active markets for identical assets (level 1)		Significant other observable inputs (level 2)		Significant unobservable inputs (level 3)

Warrant liability	$	95,661	$	—	$	—	$	95,661

	September 30, 2013


	Total		Quoted prices in active markets for identical assets (level 1)		Significant other observable inputs (level 2)		Significant unobservable inputs (level 3)

Marketable securities	$	133,182,565	$	—	$	133,182,565	$	—
Warrant liability		98,819		—		—		98,819

	December 31, 2011


	Total		Quoted prices in active markets for identical assets (level 1)	Significant other observable inputs (level 2)	Significant unobservable inputs (level 3)

Warrant liability	$	1,878,316	$—	$—	$1,878,316

	December 31, 2012


	Total		Quoted prices in active markets for identical assets (level 1)	Significant other observable inputs (level 2)	Significant unobservable inputs (level 3)

Warrant liability	$	95,661	$—	$—	$95,661

Summary of marketable securities accounted for as available-for-sale securities

	September 30, 2013


			Gross Unrealized
	Amortized Cost		Gross Unrealized					Fair Value
	Amortized Cost		Gains		Losses			Fair Value

Commercial paper	$	24,978,703	$	20,527	$	—		$	24,999,230
U.S. corporate debt securities		108,244,329		19,642		(80,636	)		108,183,335

	$	133,223,032	$	40,169	$	(80,636	)	$	133,182,565

Schedule of marketable securities on the balance sheet

	September 30, 2013


	Less than 12 Months		More than 12 Months

Commercial paper	$	24,999,230	$	—
U.S. corporate debt securities		57,824,657		50,358,678

Total Marketable securities	$	82,823,887	$	50,358,678

Summary of changes in the fair value of the Company's Level 3 valuation for warrant liability

	Level 3 assets



Beginning balance as of December 31, 2012	$	95,661
Warrants issued in connection with convertible promissory notes		6,000,000
Deemed dividend		18,248,768
Exercise of warrants issued in connection with convertible promissory notes		(24,248,765	)
Change in fair value of warrant liability		3,155

Ending balance as of September 30, 2013	$	98,819

	Level 3 assets



Beginning balance January 1, 2011	$	2,340,263
Change in fair value of warrant liability		(461,947	)

Ending balance as of December 31, 2011		1,878,316
Change in fair value of warrant liability		(1,782,655	)

Ending balance as of December 31, 2012	$	95,661

Other comprehensive income (loss) and accumulated other comprehensive items (Tables)

9 Months Ended

Sep. 30, 2013

Other comprehensive income (loss) and accumulated other comprehensive items

Summary of other comprehensive loss and the changes in accumulated other comprehensive items

	Unrealized losses on marketable securities			Total accumulated other comprehensive items



Balance at December 31, 2012	$	—		$	—
Other comprehensive loss before reclassifications		(40,467	)		(40,467	)
Amounts reclassified from other comprehensive items		—			—

Other comprehensive loss		(40,467	)		(40,467	)

Balance at September 30, 2013	$	(40,467	)	$	(40,467	)

Accounts payable and accrued expenses (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Accounts payable and accrued expenses

Schedule of components of accounts payable and accrued expenses

	December 31, 2012		September 30, 2013



Employee compensation, benefits, and related accruals	$	3,096,475	$	3,659,084
Consulting and contracted research		2,515,678		3,556,350
Professional fees		559,228		1,532,458
Accounts payable		621,591		1,017,122
Other		230,999		440,479

	$	7,023,971	$	10,205,493

	December 31,


	2011		2012

Employee compensation, benefits, and related accruals	$	3,492,170	$	3,096,475
Consulting and contracted research		6,749,272		2,515,678
Professional fees		492,811		559,228
Accounts payable		1,878,109		621,591
Other		437,092		230,999

	$	13,049,454	$	7,023,971

Capital structure (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Capital structure

Summary of the Company's outstanding warrants

The following is a summary of the Company's outstanding warrants as of December 31, 2012:

		Exercise price



Series Two	24,712	$	16.00	2014
Series Two	50,000	$	16.00	2017
Series Two	56,250	$	16.00	2019 and 2020
Common stock	645	$	2,520	2013 and 2014

The following is a summary of the Company's outstanding warrants as of September 30, 2013:

	Warrant shares	Exercise price		Expiration



Common stock	3,088	$	128.00	2014
Common stock	6,250	$	128.00	2017
Common stock	7,030	$	128.00	2019 and 2020
Common stock	645	$	2,520	2013 and 2014

The following is a summary of the Company's outstanding warrants as of December 31, 2011:

		Exercise price



Series E convertible preferred stock	54,465	$	7.26	2014
Series F convertible preferred stock	50,000	$	16.00	2017
Series F-2 convertible preferred stock	56,250	$	16.00	2019 and 2020
Common stock	645	$	2,520	2013 and 2014

The following is a summary of the Company's outstanding warrants as of December 31, 2012:

		Exercise price



Series 2 convertible preferred stock	24,712	$	16.00	2014
Series 2 convertible preferred stock	50,000	$	16.00	2017
Series 2 convertible preferred stock	56,250	$	16.00	2019 and 2020
Common stock	645	$	2,520	2013 and 2014

- Definition

+ References + Details

Net income (loss) per share (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Net income (loss) per share

Schedule of computation of basic and diluted net income (loss) per share for common stockholders

	Nine months ended September 30,


	2012			2013

Numerator
Net loss	$	(19,963,058	)	$	(33,687,612	)
Deemed dividend		—			(18,248,768	)
Gain on exchange of convertible preferred stock in connection with recapitalization		159,954,069			3,390,750
Less beneficial conversion charge		(377,787	)		—
Less net income attributable to participating securities		(139,077,495	)		—

Net income (loss) attributable to common stockholders	$	535,729		$	(48,545,630	)

Denominator
Denominator for basic net income (loss) per share		2,937			8,995,167
Effect of dilutive securities
Series Three convertible preferred stock		10,656			—

Denominator for diluted net income (loss) per share		13,593			8,995,167

Net income (loss) per share:
Basic	$	182.41		$	(5.40	)*

Diluted	$	39.41		$	(5.40	)*

* In the nine months ended September 30, 2013, the Company experienced a net loss and therefore did not report any dilutive share impact.

	Year ended December 31


	2011			2012

Numerator
Net income (loss)	$	30,904,514		$	(26,235,102	)
Gain on exchange of convertible preferred stock in connection with recapitalization		—			159,954,069
Less beneficial conversion charge		—			(377,787	)
Less net income attributable to participating preferred stock		(30,878,445	)		(132,609,918	)

Net income attributable to common stockholders	$	26,069		$	731,262

Denominator
Denominator for basic earnings per share		1,089			3,328
Effect of dilutive securities:
Employee stock options		4,640			—
Series 3 convertible preferred stock		—			13,877

Denominator for diluted earnings per share		5,729			17,205

Net income per share:
Basic		23.95			219.76

Diluted		4.55			42.50

Schedule of historical dilutive common share equivalents outstanding

	As of September 30,


	2012		2013

Stock Options		44,218		1,987,860
Unvested restricted stock		—		1,113,807

Total		44,218		3,101,667

Stock option plan (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Stock option plan

Summary of stock option activity

(in thousands)			Exercise price	Weighted- average exercise price		Weighted- average remaining contractual term	Aggregate intrinsic value




Outstanding at December 31, 2012	42,394		$218.40-$1,149.60	$	469.48
Granted	2,007,713		$10.59-$10.85	$	10.85
Exercised	—		—		—
Forfeited	(62,247	)	$10.85-$1,149.60	$	17.10

Outstanding at September 30, 2013	1,987,860		$10.59-$1,149.60	$	20.44	9.51 years	$	20,652

Exercisable at September 30, 2013	61,834		$10.59-$1,149.60	$	290.39	6.06 years	$	265

	Number of options		Exercise price	Weighted- average exercise price		Weighted- average remaining contractual term



Outstanding at December 31, 2010	39,557		$226.80-$1,149.60	$	547.20
Granted	8,123		$490.80	$	490.80
Exercised	(11	)	$451.20-$508.80	$	459.60
Forfeited	(875	)	$226.80-$1,149.60	$	757.20

Outstanding at December 31, 2011	46,794		$226.80-$1,149.60	$	532.80	5.74 years
Granted	5,715		$218.40	$	218.40
Exercised	—
Forfeited	(10,115	)	$218.40-$1,149.60	$	604.80

Outstanding at December 31, 2012	42,394		$218.40-$1,149.60	$	474.00	5.02 years	—

Exercisable at December 31, 2012	33,414		$218.40-$1,149.60	$	482.40	4.14 years	—

Exercisable and expected to vest at December 31, 2012	42,184		$218.40-$1,149.60	$	476.40	4.97 years	—

Schedule of assumptions used to estimate fair value of grants made on the date of grant

		Nine months ended September 30, 2013



Risk-free interest rate		0.85%-1.69%
Expected volatility		87%-88%
Expected term		5.00 to 6.00 years
Expected dividend yield		0.0%





Risk-free interest rate	2.40%	1.135%
Expected volatility	87%	87%
Expected term	6.00-6.25 years	6.00-6.25 years

Summary of information on the Company's restricted stock

	Restricted stock


	Number of shares			Weighted average grant date fair value

January 1, 2013		—			—
Granted		1,131,524		$	10.68
Vested		—		$	—
Forfeited		(17,717	)	$	10.63

Unvested at September 30, 2013		1,113,807		$	10.68

Schedule of share-based compensation expense recorded in the statement of operations

	Nine months ended September 30,


	2012		2013

Research and development	$	653,462	$	1,377,640
General and administrative		1,162,260		3,764,547

Total	$	1,815,722	$	5,142,187

Selected quarterly financial data (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2013

Dec. 31, 2012

Selected quarterly financial data

Summary of quarterly data

Summarized quarterly data for 2012 and 2013 are as follows (in thousands, except per share data):

	For the quarters ending


	March 31			June 30			September 30

2012:
Collaboration and grant revenue	$	12,525,720		$	7,585,177		$	7,195,076
Operating expenses		18,745,957			15,083,384			14,250,383
Income (loss) from operations		(6,220,237	)		(7,498,207	)		(7,055,307	)
Net income (loss)		(6,597,861	)		(6,068,072	)		(7,297,125	)
Gain on exchange of convertible preferred stock in connection with recapitalization		—			159,954,069			—
Less beneficial conversion charge		—			(377,787	)		—
Net income (loss) attributable to common stockholders		(6,597,861	)		153,508,210			(7,297,125	)
Basic net income (loss) per common share(1)	$	(5,992.61	)	$	168.00		$	(1,605.53	)
Diluted net income (loss) per common share(1)	$	(5,992.61	)	$	48.29		$	(1,605.53	)
2013:
Collaboration and grant revenue	$	7,141,664		$	6,854,212		$	16,289,573
Operating expenses		15,718,073			21,307,148			20,565,188
Income (loss) from operations		(8,576,409	)		(14,452,936	)		(4,275,615	)
Net income (loss)		(14,684,535	)		(14,586,578	)		(4,416,499	)
Deemed dividend		(18,248,768	)		—			—
Gain on exchange of convertible preferred stock in connection with recapitalization		3,390,750			—			—
Net income (loss) attributable to common stockholders		(29,542,553	)		(14,586,578	)		(4,416,499	)
Basic net income (loss) per common share(1)	$	(6,527.30	)	$	(5.51	)	$	(0.19	)
Diluted net income (loss) per common share(1)	$	(6,527.30	)	$	(5.51	)	$	(0.19	)

(1) The amounts were computed independently for each quarter and the sum of the quarters may not total the annual amounts.

	For the quarters ending


	March 31			June 30			September 30			December 31

2011:
Collaboration and grant revenue	$	4,853,008		$	4,772,720		$	86,423,733		$	9,362,686
Operating expenses		19,848,797			19,682,313			18,315,064			16,983,976
Income (loss) from operations		(14,995,789	)		(14,909,593	)		68,108,669			(7,621,290	)
Net income (loss)		(15,550,607	)		(15,388,398	)		67,608,165			(5,764,646	)
Basic net income (loss) per common share(1)	$	(14,289.99	)	$	(14,140.93	)	$	52.39		$	(5,290.57	)
Diluted net income (loss) per common share(1)	$	(14,289.99	)	$	(14,140.93	)	$	9.95		$	(5,290.57	)
2012:
Collaboration and grant revenue	$	12,525,720		$	7,585,177		$	7,195,076		$	6,640,090
Operating expenses		18,745,957			15,083,384			14,250,383			12,674,520
Income (loss) from operations		(6,220,237	)		(7,498,207	)		(7,055,307	)		(6,034,430	)
Net income (loss)		(6,597,861	)		(6,068,072	)		(7,297,125	)		(6,272,044	)
Gain on exchange of convertible preferred stock in connection with recapitalization		—			159,954,069			—			—
Less beneficial conversion charge		—			(377,787	)		—			—
Net income (loss) attributable to common stockholders		(6,597,861	)		153,508,210			(7,297,125	)		(6,372,044	)
Basic net income (loss) attributable to common stockholders per share	$	(5,992.61	)	$	168.00		$	(1,605.53	)	$	(1,380.13	)
Diluted net income (loss) attributable to common stockholders per share(1)	$	(5,992.61	)	$	48.29		$	(1,605.53	)	$	(1,380.13	)

(1) The amounts were computed independently for each quarter and the sum of the quarters may not total the annual amounts.

The Company (Details) - USD ($)	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
The Company
Accumulated deficit	$ 310,912,330	$ 277,224,718	$ 250,611,829

Summary of significant accounting policies (Details)	Mar. 07, 2013
Common stock
Reverse stock split
Reverse stock split ratio	0.0083

Fair value of financial instruments and marketable securities (Details) - USD ($)	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Financial assets measured at fair value on recurring basis
Marketable securities	$ 133,182,565
Recurring basis \| Total
Financial assets measured at fair value on recurring basis
Marketable securities	133,182,565
Warrant liability	98,819	$ 95,661	$ 1,878,316
Recurring basis \| Significant other observable inputs (level 2)
Financial assets measured at fair value on recurring basis
Marketable securities	133,182,565
Recurring basis \| Significant unobservable inputs (level 3)
Financial assets measured at fair value on recurring basis
Warrant liability	$ 98,819	$ 95,661	$ 1,878,316

Fair value of financial instruments and marketable securities (Details 2)	9 Months Ended
	Sep. 30, 2013 USD ($)
Marketable securities accounted for as available-for-sale securities
Amortized Cost	$ 133,223,032
Gross Unrealized Gains	40,169
Gross Unrealized Losses	(80,636)
Total Marketable securities	133,182,565
Commercial paper
Marketable securities accounted for as available-for-sale securities
Amortized Cost	24,978,703
Gross Unrealized Gains	20,527
Total Marketable securities	24,999,230
U.S. corporate debt securities
Marketable securities accounted for as available-for-sale securities
Amortized Cost	108,244,329
Gross Unrealized Gains	19,642
Gross Unrealized Losses	(80,636)
Total Marketable securities	$ 108,183,335

Fair value of financial instruments and marketable securities (Details 3) - USD ($)	Sep. 30, 2013	Dec. 31, 2012
Marketable securities on the balance sheet
Total Marketable securities, Less Than 12 Months	$ 82,823,887
Total Marketable securities, More Than 12 Months	50,358,678
Marketable securities		$ 0
Commercial paper
Marketable securities on the balance sheet
Total Marketable securities, Less Than 12 Months	24,999,230
U.S. corporate debt securities
Marketable securities on the balance sheet
Total Marketable securities, Less Than 12 Months	57,824,657
Total Marketable securities, More Than 12 Months	$ 50,358,678

Fair value of financial instruments and marketable securities (Details 4) - USD ($)	3 Months Ended			9 Months Ended	12 Months Ended
	Sep. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Changes in the fair value of warrant liability
Deemed dividend	$ (4,416,499)	$ (18,248,768)	$ (7,297,125)	$ 18,248,768
Warrant
Changes in the fair value of warrant liability
Beginning balance		$ 95,661		95,661	$ 1,878,316	$ 2,340,263
Warrants issued in connection with convertible promissory notes				6,000,000
Deemed dividend				18,248,768
Exercise of warrants issued in connection with convertible promissory notes				(24,248,765)
Change in fair value of warrant liability				3,155	(1,782,655)	(461,947)
Ending balance	$ 98,819			$ 98,819	$ 95,661	$ 1,878,316
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model
Volatility (as a percent)					87.00%	88.00%
Strike price (in dollars per share)	$ 128			$ 128	$ 16
Warrant \| Minimum
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model
Volatility (as a percent)				69.00%
Risk-free interest rate (as a percent)				0.02%	0.16%	0.25%
Strike price (in dollars per share)						$ 7.26
Expected life				2 months 19 days	1 year	2 years
Warrant \| Maximum
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model
Volatility (as a percent)				87.00%
Risk-free interest rate (as a percent)				1.705%	1.18%	1.62%
Strike price (in dollars per share)						$ 16.00
Expected life				5 years 11 months 23 days	7 years	8 years
Warrant \| Preferred shares
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model
Fair value of common shares (in dollars per share)	$ 21.46			$ 21.46	$ 2.35	$ 16.00

Other comprehensive income (loss) and accumulated other comprehensive items (Details)	9 Months Ended
	Sep. 30, 2013 USD ($)
Other comprehensive income (loss) and accumulated other comprehensive items
Other comprehensive loss before reclassifications	$ (40,467)
Other comprehensive loss	(40,467)
Balance at the end of the period	(40,467)
Unrealized Losses On Marketable Securities
Other comprehensive income (loss) and accumulated other comprehensive items
Other comprehensive loss before reclassifications	(40,467)
Other comprehensive loss	(40,467)
Balance at the end of the period	$ (40,467)

- Definition

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

+ References + Details

Accounts payable and accrued expenses (Details) - USD ($)	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Accounts payable and accrued expenses
Employee compensation, benefits, and related accruals	$ 3,659,084	$ 3,096,475	$ 3,492,170
Consulting and contracted research	3,556,350	2,515,678	6,749,272
Professional fees	1,532,458	559,228	492,811
Accounts payable	1,017,122	621,591	1,878,109
Other	440,479	230,999	437,092
Accounts payable and accrued expenses	$ 10,205,493	$ 7,023,971	$ 13,049,454

Debt (Details)	1 Months Ended		9 Months Ended
Debt (Details)	Jul. 31, 2013 USD ($) item	Sep. 30, 2009 USD ($) item	Sep. 30, 2013 USD ($)	Dec. 31, 2012
Debt
Paid outstanding principal and interest, due under promissory notes issued	$ 2,600,000
Loss on extinguishment of debt			$ (129,963)
Secured debt facility
Debt
Maximum borrowing capacity	$ 25,000,000	$ 25,000,000
Number of lenders \| item	2	2
Fixed interest rate of notes (as a percent)	13.65%			13.65%

Capital structure (Details)		1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended
Capital structure (Details)	Mar. 07, 2013 USD ($) shares	Jun. 30, 2013 USD ($) $ / shares shares	May 31, 2013 USD ($) $ / shares shares	Jul. 31, 2012 USD ($)	Mar. 31, 2013 USD ($)	Jun. 30, 2012 USD ($)	Sep. 30, 2013 USD ($) shares	Sep. 30, 2012 USD ($)	Dec. 31, 2012 USD ($) shares	Feb. 28, 2013 USD ($) $ / shares shares	Dec. 31, 2011 shares
Capital structure
Aggregate gross proceeds \| $								$ 29,354,752	$ 29,354,752
Gross proceeds raised \| $					$ 60,000,000
Gain on extinguishment of shares of Series One, Two and Three stock \| $				$ 160,000,000	3,390,750	$ 159,954,069	$ 3,390,750	$ 159,954,069	$ 159,954,069
Common stock
Common stock, Authorized shares \| shares			125,000,000				125,000,000		17,000,000		216,666
Initial Public Offering
Net proceeds from initial public offering after deducting underwriting discounts and commissions and other offering expenses payable \| $							$ 131,649,688
Series One and Series Two \| Warrants
Capital structure
Warrants issued to purchase shares \| shares										2,527,675
Exercise price (in dollars per share) \| $ / shares										0.01
Shares issued and sold \| shares	2,527,675
Series Four
Capital structure
Shares issued and sold \| shares	4,497,035		375,000
Aggregate gross proceeds \| $	$ 54,000,000
Share price (in dollars per share) \| $ / shares			$ 12.00
Aggregate purchase price \| $			$ 4,500,000
Series Five
Capital structure
Number of shares issued upon conversion \| shares	6,700,487
Series Five \| Warrants
Capital structure
Number of shares issued upon conversion \| shares	2,095,515
Common stock
Capital structure
Shares issued and sold \| shares		9,627,800
Reverse stock split ratio	0.0083
Share price (in dollars per share) \| $ / shares		$ 15.00
Initial Public Offering
Common stock shares issuable pursuant to the exercise by the underwriters of an over-allotment option \| shares		1,255,800
Net proceeds from initial public offering after deducting underwriting discounts and commissions and other offering expenses payable \| $		$ 131,600,000
Series Four and Series Five Convertible Preferred Stock
Capital structure
Number of shares issued upon conversion \| shares		14,170,956
Convertible promissory notes
Capital structure
Principal amount of convertible promissory notes issued \| $										$ 6,000,000
Debt discount recorded to interest expense \| $					6,000,000
Amount raised in bridge financing \| $					$ 6,000,000
Convertible promissory notes \| Series Four
Capital structure
Shares issued upon conversion of convertible promissory notes \| shares	502,919

Capital structure (Details 2) - Warrants	Sep. 30, 2013 $ / shares shares	Dec. 31, 2012 $ / shares shares	Dec. 31, 2011 $ / shares shares
Series Two \| 2014
Warrants
Warrant shares \| shares		24,712
Exercise price (in dollars per share) \| $ / shares		16.00
Series Two \| 2017
Warrants
Warrant shares \| shares		50,000
Exercise price (in dollars per share) \| $ / shares		16.00
Series Two \| 2019 and 2020
Warrants
Warrant shares \| shares		56,250
Exercise price (in dollars per share) \| $ / shares		16.00
Common stock \| 2014
Warrants
Warrant shares \| shares	3,088
Exercise price (in dollars per share) \| $ / shares	128.00
Common stock \| 2017
Warrants
Warrant shares \| shares	6,250
Exercise price (in dollars per share) \| $ / shares	128.00
Common stock \| 2019 and 2020
Warrants
Warrant shares \| shares	7,030
Exercise price (in dollars per share) \| $ / shares	128.00
Common stock \| 2013 and 2014
Warrants
Warrant shares \| shares	645	645	645
Exercise price (in dollars per share) \| $ / shares	2,520	2,520	2,520

Net income (loss) per share (Details) - USD ($)	1 Months Ended	3 Months Ended											9 Months Ended		12 Months Ended
Net income (loss) per share (Details) - USD ($)	Jul. 31, 2012	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Numerator
Net loss		$ (4,416,499)	$ (14,586,578)	$ (14,684,535)	$ (6,272,044)	$ (7,297,125)	$ (6,068,072)	$ (6,597,861)	$ (5,764,646)	$ 67,608,165	$ (15,388,398)	$ (15,550,607)	$ (33,687,612)	$ (19,963,058)	$ (26,235,102)	$ 30,904,514
Deemed dividend		$ 4,416,499		18,248,768		$ 7,297,125							(18,248,768)
Gain on exchange of convertible preferred stock in connection with recapitalization	$ 160,000,000			$ 3,390,750			159,954,069						3,390,750	159,954,069	159,954,069
Less beneficial conversion charge							$ (377,787)							(377,787)	(377,787)
Less net income attributable to participating securities														(139,077,495)	(132,609,918)	(30,878,445)
Net loss attributable to common stockholders													$ (48,545,630)	$ 535,729	$ 731,262	$ 26,069
Denominator
Denominator for basic net income (loss) per share (in shares)													8,995,167	2,937	3,328	1,089
Effect of dilutive securities Series Three convertible preferred stock (in shares)														10,656	13,877
Denominator for diluted net income (loss) per share (in shares)													8,995,167	13,593	17,205	5,729
Net income (loss) per share:
Basic (in dollars per share)		$ (0.19)	$ (5.51)	$ (6,527.30)	$ 1,380.13	$ (1,605.53)	$ 168.00	$ (5,992.61)	$ (5,290.57)	$ 52.39	$ (14,140.93)	$ (14,289.99)	$ (5.40)	$ 182.41	$ 219.76	$ 23.95
Diluted (in dollars per share)		$ (0.19)	$ (5.51)	$ (6,527.30)	$ 1,380.13	$ (1,605.53)	$ 48.29	$ (5,992.61)	$ (5,290.57)	$ 9.95	$ (14,140.93)	$ (14,289.99)	$ (5.40)	$ 39.41	$ 42.50	$ 4.55

Net income (loss) per share (Details 2) - shares	9 Months Ended		12 Months Ended
Net income (loss) per share (Details 2) - shares	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Net income (loss) per share
Total shares excluded from calculation	3,101,667	44,218	600,000	1,300,000
Stock Options
Net income (loss) per share
Total shares excluded from calculation	1,987,860	44,218
Unvested restricted stock
Net income (loss) per share
Total shares excluded from calculation	1,113,807

Stock option plan (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	9 Months Ended	12 Months Ended
	Mar. 05, 2013	May 31, 2013	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Restricted stock
Number of Shares
Granted (in shares)			1,131,524
Forfeited (in shares)			(17,717)
Unvested at the end of the period (in shares)			1,113,807
Weighted Average Grant Date Fair Value
Granted (in dollars per share)			$ 10.68
Forfeited (in dollars per share)			10.63
Unvested at the end of the period (in dollars per share)			$ 10.68
Stock options
Number of options
Outstanding at the beginning of the period (in shares)			42,394	46,794	39,557
Granted (in shares)			2,007,713	5,715	8,123
Forfeited (in shares)			(62,247)	(10,115)	(875)
Outstanding at the end of the period (in shares)			1,987,860	42,394	46,794
Exercisable at the end of the period (in shares)			61,834	33,414
Exercise price
Granted (in dollars per share)				$ 218.40	$ 490.80
Weighted-average exercise price
Outstanding at the beginning of the period (in dollars per share)			$ 469.48	532.80	547.20
Granted (in dollars per share)			10.85	218.40	490.80
Forfeited (in dollars per share)			17.10	604.80	757.20
Outstanding at the end of the period (in dollars per share)			20.44	469.48	$ 532.80
Exercisable at the end of the period (in dollars per share)			$ 290.39	$ 482.40
Weighted-average remaining contractual term
Outstanding at the end of the period			9 years 6 months 4 days	5 years 7 days	5 years 8 months 26 days
Exercisable at the end of the period			6 years 22 days	4 years 1 month 20 days
Aggregate intrinsic value
Outstanding at the end of the period (in dollars)			$ 20,652
Exercisable at the end of the period (in dollars)			$ 265
Valuation assumptions
Risk-free interest rate (as a percent)				1.135%	2.40%
Expected volatility (as a percent)				87.00%	87.00%
Expected dividend yield (as a percent)			0.00%	0.00%	0.00%
Weighted average grant date fair value (in dollars per share)			$ 7.86	$ 160.65	$ 364.80
Stock options \| Minimum
Exercise price
Outstanding at the beginning of the period (in dollars per share)			218.40	226.80	226.80
Granted (in dollars per share)			10.59
Forfeited (in dollars per share)			10.85	218.40	226.80
Outstanding at the end of the period (in dollars per share)			10.59	218.40	$ 226.80
Exercisable at the end of the period (in dollars per share)			$ 10.59	$ 218.40
Valuation assumptions
Risk-free interest rate (as a percent)			0.85%
Expected volatility (as a percent)			87.00%
Expected term			5 years	6 years	6 years
Stock options \| Maximum
Exercise price
Outstanding at the beginning of the period (in dollars per share)			$ 1,149.60	$ 1,149.60	$ 1,149.60
Granted (in dollars per share)			10.85
Forfeited (in dollars per share)			1,149.60	1,149.60	1,149.60
Outstanding at the end of the period (in dollars per share)			1,149.60	1,149.60	$ 1,149.60
Exercisable at the end of the period (in dollars per share)			$ 1,149.60	$ 1,149.60
Valuation assumptions
Risk-free interest rate (as a percent)			1.69%
Expected volatility (as a percent)			88.00%
Expected term			6 years	6 years 3 months	6 years 3 months
2013 Stock Incentive Plan \| Restricted stock
Number of options
Granted (in shares)	735,324
2013 Stock Incentive Plan \| Stock options
Number of options
Granted (in shares)	4,613
2013 Stock Incentive Plan \| Common stock
Stock option plan
Number of shares authorized	739,937
2009 Stock Incentive Plan
Stock option plan
Number of additional shares authorized		2,500,000
2009 Stock Incentive Plan \| Common stock
Stock option plan
Number of shares available for issuance				14,271
2013 Long Term Incentive Plan \| Common stock \| Minimum
Stock option plan
Annual increase in the number of shares on the first day of the fiscal year		2,500,000
Annual increase in the number of shares outstanding on the first day of the fiscal year (as a percent)		4.00%
2013 Long Term Incentive Plan \| Common stock \| Maximum
Stock option plan
Number of shares subject to outstanding awards		3,040,444
2009 Equity and Long Term Incentive Plan and 2013 Stock Incentive Plan \| Common stock
Stock option plan
Number of shares available for issuance		122,296

Stock option plan (Details 2) - USD ($)	9 Months Ended		12 Months Ended
Stock option plan (Details 2) - USD ($)	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Share-based compensation expense recorded in the statement of operations
Share-based compensation expense	$ 5,142,187	$ 1,815,722	$ 2,288,000	$ 2,817,000
Research and development
Share-based compensation expense recorded in the statement of operations
Share-based compensation expense	1,377,640	653,462
General and administrative
Share-based compensation expense recorded in the statement of operations
Share-based compensation expense	$ 3,764,547	$ 1,162,260

Stock option plan (Details 3) - 1998, 2009 and 2013 Plans - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Additional disclosures
Unrecognized compensation cost	$ 21.0	$ 2.2
Weighted average remaining service period for recognition of unrecognized compensation cost	2 years 3 months 11 days

Collaboration Revenue (Details) $ in Millions	Aug. 08, 2013 USD ($)
Collaboration Revenue.
Milestone payment received from Roche	$ 10.0

Selected quarterly financial data (Details) - USD ($)	1 Months Ended	3 Months Ended											9 Months Ended		12 Months Ended
Selected quarterly financial data (Details) - USD ($)	Jul. 31, 2012	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2011
Selected quarterly financial data
Collaboration and grant revenue		$ 16,289,573	$ 6,854,212	$ 7,141,664	$ 6,640,090	$ 7,195,076	$ 7,585,177	$ 12,525,720	$ 9,362,686	$ 86,423,733	$ 4,772,720	$ 4,853,008	$ 30,285,449	$ 27,305,973	$ 33,946,063	$ 105,412,147
Operating expenses		20,565,188	21,307,148	15,718,073	12,674,520	14,250,383	15,083,384	18,745,957	16,983,976	18,315,064	19,682,313	19,848,797	57,590,409	48,079,724	60,754,244	74,830,150
Income (loss) from operations		(4,275,615)	(14,452,936)	(8,576,409)	(6,034,430)	(7,055,307)	(7,498,207)	(6,220,237)	(7,621,290)	68,108,669	(14,909,593)	(14,995,789)	(27,304,960)	(20,773,751)	(26,808,181)	30,581,997
Net income (loss)		(4,416,499)	(14,586,578)	(14,684,535)	(6,272,044)	(7,297,125)	(6,068,072)	(6,597,861)	$ (5,764,646)	$ 67,608,165	$ (15,388,398)	$ (15,550,607)	(33,687,612)	(19,963,058)	(26,235,102)	30,904,514
Deemed dividend		(4,416,499)		(18,248,768)		(7,297,125)							18,248,768
Gain on exchange of convertible preferred stock in connection with recapitalization	$ 160,000,000			3,390,750			159,954,069						3,390,750	159,954,069	159,954,069
Less beneficial conversion charge							(377,787)							(377,787)	(377,787)
Net income (loss) attributable to common stockholders		$ (4,416,499)	$ (14,586,578)	$ (29,542,553)	$ (6,372,044)	$ (7,297,125)	$ 153,508,210	$ (6,597,861)					$ (48,545,630)	$ 139,613,224	$ 133,341,180	$ 30,904,514
Basic (in dollars per share)		$ (0.19)	$ (5.51)	$ (6,527.30)	$ 1,380.13	$ (1,605.53)	$ 168.00	$ (5,992.61)	$ (5,290.57)	$ 52.39	$ (14,140.93)	$ (14,289.99)	$ (5.40)	$ 182.41	$ 219.76	$ 23.95
Diluted (in dollars per share)		$ (0.19)	$ (5.51)	$ (6,527.30)	$ 1,380.13	$ (1,605.53)	$ 48.29	$ (5,992.61)	$ (5,290.57)	$ 9.95	$ (14,140.93)	$ (14,289.99)	$ (5.40)	$ 39.41	$ 42.50	$ 4.55

Subsequent events (Details) - USD ($)			1 Months Ended
Subsequent events (Details) - USD ($)	Dec. 13, 2013	Aug. 08, 2013	Jan. 31, 2014	Aug. 31, 2013	Dec. 31, 2011	Nov. 30, 2011
Subsequent events
Milestone payments		$ 10,000,000
Collaboration agreement \| Roche and SMA Foundation
Subsequent events
Upfront payment					$ 30,000,000	$ 30,000,000
Collaboration agreement \| Roche and SMA Foundation \| Sales milestones \| Maximum
Subsequent events
Milestone payments					$ 460,000,000
Collaboration agreement \| Roche and SMA Foundation \| Development event milestones
Subsequent events
Milestone payments				$ 10,000,000
Subsequent event \| Stock options
Subsequent events
Expected compensation cost on modification of awards	$ 600,000
Subsequent event \| Executive officers \| Stock options
Subsequent events
Awards vested during the period on waiver of remaining performance condition (as a percent)	25.00%
Expected vesting percentage	2.0833%
Subsequent event \| Collaboration agreement \| Roche and SMA Foundation \| Clinical development milestones
Subsequent events
Milestone payments			$ 7,500,000