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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2014	Feb. 24, 2015	Jun. 30, 2014
Document and Entity Information
Entity Registrant Name	PTC THERAPEUTICS, INC.
Entity Central Index Key	0001070081
Document Type	10-K
Document Period End Date	Dec. 31, 2014
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float			$ 683,512,510
Entity Common Stock, Shares Outstanding		33,688,913
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY

Consolidated Balance Sheets - USD ($)	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 49,748,000	$ 15,414,000
Marketable securities	265,493,000	127,053,000
Prepaid expenses and other current assets	3,885,000	1,599,000
Receivables, net	4,445,000	958,000
Total current assets	323,571,000	145,024,000
Fixed assets, net	9,159,000	6,730,000
Deposits and other assets	489,000	149,000
Total assets	333,219,000	151,903,000
Current liabilities:
Accounts payable and accrued expenses	29,121,000	12,207,000
Current portion of long-term debt		49,000
Deferred revenue	3,354,000	878,000
Total current liabilities	32,475,000	13,134,000
Other long-term liabilities	2,277,000	2,227,000
Total liabilities	34,752,000	15,361,000
Stockholders' equity:
Common stock, $0.001 par value. Authorized 125,000,000 shares; issued and outstanding 32,898,392 shares at December 31, 2014. Authorized 125,000,000 shares; issued and outstanding 23,803,282 shares at December 31, 2013	33,000	24,000
Additional paid-in capital	721,722,000	465,246,000
Accumulated other comprehensive (loss) income	(737,000)	70,000
Accumulated deficit	(422,551,000)	(328,798,000)
Total stockholders' equity	298,467,000	136,542,000
Total liabilities and stockholders' equity	$ 333,219,000	$ 151,903,000

Consolidated Balance sheets (Parenthetical) - $ / shares	Dec. 31, 2014	Dec. 31, 2013
Consolidated Balance Sheets
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, undesignated shares	5,000,000	5,000,000
Preferred stock, issued shares	0	0
Preferred stock, outstanding shares	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized shares	125,000,000	125,000,000
Common stock, issued shares	32,898,392	23,803,282
Common stock, outstanding shares	32,898,392	23,803,282

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues:
Net product revenue	$ 717
Collaboration revenue	22,246	$ 31,326	$ 28,779
Grant revenue	2,282	3,370	5,167
Total revenues	25,245	34,696	33,946
Operating expenses:
Research and development	79,838	54,875	46,139
Selling, general and administrative	44,820	25,219	14,615
Total operating expenses	124,658	80,094	60,754
Loss from operations	(99,413)	(45,398)	(26,808)
Interest income (expense), net	1,180	(6,084)	(1,210)
Loss on extinguishment of debt		(130)
Other income (expense), net	(213)	38	1,783
Loss from operations before tax benefit	(98,446)	(51,574)	(26,235)
Net tax benefit	4,693
Net loss	(93,753)	(51,574)	(26,235)
Deemed dividend		(18,249)
Gain on exchange of convertible preferred stock in connection with recapitalization		3,391	159,954
Less beneficial conversion charge			(378)
Net (loss) income attributable to common stockholders	$ (93,753)	$ (66,432)	$ 133,341
Net (loss) income attributable to common stockholders per share:
Basic net income (loss) per common share	$ (2.97)	$ (5.18)	$ 219.76
Diluted net income (loss) per common share	$ (2.97)	$ (5.18)	$ 42.50
Weighted-average shares outstanding:
Basic (in shares)	31,565,310	12,829,411	3,328
Diluted (in shares)	31,565,310	12,829,411	17,205

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Consolidated statements of comprehensive loss
Net loss	$ (93,753)	$ (51,574)	$ (26,235)
Other comprehensive (loss) income:
Unrealized (loss) gain on marketable securities	(457)	70
Foreign currency translation loss	(350)
Comprehensive loss	$ (94,560)	$ (51,504)	$ (26,235)

- Definition

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

+ References + Details

Consolidated Statements of Convertible Preferred Stock and Changes in Stockholders' Equity (Deficit) - USD ($)	Series A-G convertible preferred stock	Series One-Three convertible preferred stock	Series Four convertible preferred stock	Series Five convertible preferred stock	Common stock	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deficit	Total
Balance, beginning of period at Dec. 31, 2011	$ 214,379,914
Balance, beginning of period (in shares) at Dec. 31, 2011	154,728,267
Increase (decrease) in temporary equity
Issuance and exchange of series of convertible preferred stock for series of convertible preferred stock	$ (211,423,085)	$ 80,823,768
Issuance and exchange of series of convertible preferred stock for series of convertible preferred stock (in shares)	(149,560,902)	15,038,259
Conversion of series of convertible preferred stock to common stock	$ (2,956,829)
Conversion of series of convertible preferred stock to common stock (in shares)	(5,167,365)
Balance, end of period at Dec. 31, 2012		$ 80,823,768
Balance, end of period (in shares) at Dec. 31, 2012		15,038,259
Balance at Dec. 31, 2011					$ 133	$ 12,007,007		$ (250,611,829)	$ (238,604,689)
Balance (in shares) at Dec. 31, 2011					132,122
Increase (Decrease) in Stockholders' Equity
Issuance and exchange of series of convertible preferred stock for series of convertible preferred stock						159,954,069			159,954,069
Conversion of series of convertible preferred stock to common stock					$ 412	2,956,417			2,956,829
Conversion of series of convertible preferred stock to common stock (in shares)					413,223
Beneficial conversion charge						377,787		(377,787)
Share-based compensation expense						2,288,392			2,288,392
Net loss								(26,235,102)	(26,235,000)
Balance at Dec. 31, 2012					$ 545	177,583,672		(277,224,718)	(99,640,501)
Balance (in shares) at Dec. 31, 2012					545,345
Increase (decrease) in temporary equity
Issuance and exchange of series of convertible preferred stock for series of convertible preferred stock		$ (80,823,768)	$ 60,785,363	$ 101,681,783
Issuance and exchange of series of convertible preferred stock for series of convertible preferred stock (in shares)		(15,038,259)	5,374,954	8,796,002
Conversion of series of convertible preferred stock to common stock			$ (60,785,363)	$ (101,681,783)
Conversion of series of convertible preferred stock to common stock (in shares)			(5,374,954)	(8,796,002)
Increase (Decrease) in Stockholders' Equity
Reverse stock split					(540,819)
Issuance and exchange of series of convertible preferred stock for series of convertible preferred stock						(14,857,927)			(14,857,927)
Issuance of common stock from IPO and exercise of over allotment exercise, net of offering costs					$ 9,628	131,640,060			131,649,688
Issuance of common stock from IPO and exercise of over allotment exercise, net of offering costs (in shares)					9,627,800
Conversion of series of convertible preferred stock to common stock					$ 14,171	162,452,975			162,467,146
Conversion of series of convertible preferred stock to common stock (in shares)					14,170,956
Share-based compensation expense						8,427,188			8,427,188
Net loss								(51,573,575)	(51,574,000)
Comprehensive income (loss)							$ 70,393		70,000
Balance at Dec. 31, 2013					$ 24,344	465,245,968	70,393	(328,798,293)	136,542,000
Balance (in shares) at Dec. 31, 2013					23,803,282
Increase (Decrease) in Stockholders' Equity
Exercise of stock options					$ 109	1,195,286			1,195,395
Exercise of stock options (in shares)					108,645
Vesting of restricted stocks					$ 373	(373)
Vesting of restricted stock (in shares)					373,200
Issuance of common stock from IPO and exercise of over allotment exercise, net of offering costs					$ 8,072	235,971,025			235,979,097
Issuance of common stock from IPO and exercise of over allotment exercise, net of offering costs (in shares)					8,613,265
Share-based compensation expense						19,309,652			19,309,652
Net loss								(93,753,493)	(93,753,000)
Comprehensive income (loss)							(807,058)		(807,058)
Balance at Dec. 31, 2014					$ 32,898	$ 721,721,558	$ (736,665)	$ (422,551,786)	$ 298,467,000
Balance (in shares) at Dec. 31, 2014					32,898,392

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities
Net loss	$ (93,753)	$ (51,574)	$ (26,235)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	2,235	2,396	2,704
Change in valuation of warrant liability	130	(38)	(1,783)
Non-cash interest expense		6,049	226
Loss on extinguishment of debt		130
Share-based compensation expense	19,310	8,427	2,289
Amortization of premiums on investments	1,607
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(2,286)	(760)	2,452
Receivables, net	(3,487)	56	230
Deposits and other assets	(340)	48	84
Accounts payable and accrued expenses	16,914	5,183	(6,026)
Other long-term liabilities	(80)	(285)	103
Deferred revenue	2,476	(16,554)	(21,972)
Net cash used in operating activities	(57,274)	(46,922)	(47,928)
Cash flows from investing activities
Purchases of fixed assets	(4,664)	(846)	(189)
Purchases of marketable securities	(247,804)	(156,045)
Sale & redemption of marketable securities	107,300	29,062
Net cash used in investing activities	(145,168)	(127,829)	(189)
Cash flows from financing activities
Payments on long-term debt	(49)	(4,996)	(6,944)
Net proceeds from sale of Series One preferred stock			29,355
Net proceeds from sale of Series Four convertible preferred stock		60,785
Net proceeds from public offerings	235,979	131,650
Proceeds from exercise of options	1,196
Net cash provided by financing activities	237,126	187,439	22,411
Effect of exchange rate changes on cash	(350)
Net increase (decrease) in cash and cash equivalents	34,334	12,688	(25,706)
Cash and cash equivalents, beginning of period	15,414	2,726	28,432
Cash and cash equivalents, end of period	49,748	15,414	2,726
Supplemental disclosure of cash information
Cash paid for interest	1	367	1,212
Cash paid for income taxes		2	2
Supplemental disclosures of non-cash information related to investing and financing activities
Change in unrealized gain (loss) on marketable securities	$ (457)	70
Change in carry value of preferred securities resulting from recapitalization		$ 3,391	$ 159,954

The Company	12 Months Ended
The Company	Dec. 31, 2014
The Company
The Company	1. The Company PTC Therapeutics, Inc. (the Company or PTC) was incorporated as a Delaware corporation on March 31, 1998. PTC is a global biopharmaceutical company focused on the discovery, development and commercialization of orally administered, small molecule therapeutics targeting an area of RNA biology referred to as post-transcriptional control. The letters "PTC" in the corporate name are an acronym for post-transcriptional control processes, which are the regulatory events that occur in cells during and after a messenger RNA is copied from DNA through the transcription process. The Company has discovered all of its compounds currently under development using its proprietary technologies. The Company plans to continue to develop these compounds both on its own and through selective collaboration arrangements with leading pharmaceutical and biotechnology companies. The Company believes that systematically targeting post-transcriptional control processes represents an unexploited approach to drug discovery and development. The Company's internally discovered pipeline addresses multiple therapeutic areas, including rare disorders, oncology and infectious diseases The Company's lead product, Translarna™ (ataluren) received marketing authorization from the European Commission, or EC, in August 2014 for the treatment of nonsense mutation Duchenne muscular dystrophy, or nmDMD, in ambulatory patients age 5 years and over in the 31 member states of the European Economic Area, or EEA. nmDMD is a rare, life threatening disorder. This marketing authorization is subject to annual review and renewal by the European Medicines Agency, or EMA following its reassessment of the risk-benefit balance of the authorization and is further conditioned on the Company's ability to complete its global, confirmatory Phase 3 clinical trial in nmDMD, which it refers to as ACT DMD, and submit the final report, including additional efficacy and safety data from the trial, during 2015. See "Business—Regulation in the European Union" and "Risk Factors—Risks Related to Regulatory Approval of our Product Candidates" for further detail regarding the EMA's approval process, including a description of the risk-benefit balance. The Company launched Translarna on a commercial basis in Germany in December 2014 and expects to expand its launch activities across the EEA throughout 2015 and future years, subject to successful completion of pricing and reimbursement negotiations. Concurrently, the Company has been pursuing reimbursed early access programs in selected countries where those mechanisms exist, both within Europe and in those countries outside of Europe that will reference the marketing authorization described above. The Company has not generated significant 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, 2014, the Company had an accumulated deficit of approximately $422.6 million. The Company has financed its operations to date primarily through public offerings of common stock in February 2014 and October 2014, its initial public offering of common stock in June 2013 (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 area addressed by the Company's product candidates.

Summary of significant accounting policies

12 Months Ended

Dec. 31, 2014

Summary of significant accounting policies

Summary of significant accounting policies

2. Summary of significant accounting policies

Basis of presentation

The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) and include all adjustments necessary for the fair presentation of the Company's financial position for the periods presented.

Use of estimates

The preparation of financial statements in conformity with U.S. generally accepted accounting principles 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.

Consolidation

The consolidated financial statements include the accounts of PTC Therapeutics, Inc. and our wholly owned subsidiaries. All inter-company accounts, transactions, and profits have been eliminated in consolidation.

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 and reporting segment.

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.

Marketable securities

The Company considers securities with original maturities of greater than 90 days to be available for sale securities. Securities under this classification are recorded at fair value and unrealized gains and losses within accumulated other comprehensive income. The estimated fair value of the available for sale securities is determined based on quoted market prices or rates for similar instruments. In addition, the cost of debt securities in this category is adjusted for amortization of premium and accretion of discount to maturity. The Company evaluates securities with unrealized losses to determine whether such losses, if any, are other than temporary.

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

Concentration of credit risk

The Company's financial instruments that are exposed to credit risks consist primarily of cash and cash equivalents, available-for-sale marketable securities and accounts receivable. The Company maintains its cash and cash equivalents in bank accounts, which, at times, exceed federally insured limits. The Company has not experienced any credit losses in these accounts and does not believe it is exposed to any significant credit risk on these funds. The Company's investment policy includes guidelines on the quality of the financial institutions and financial instruments the Company is allowed to invest in, which the Company believes minimizes the exposure to concentration of credit risk.

The Company is subject to credit risk from its accounts receivable related to its product sales revenue of Translarna. The payment terms are predetermined and the Company evaluates the creditworthiness of each customer or distributor on a regular basis. The Company periodically assesses the financial strength of the holders of its accounts receivable to establish allowances for anticipated losses, if necessary. The Company reserves all uninsured amounts billed directly to a patient until the time of cash receipt as collectability is not reasonably assured at the time the product is received. To date, the Company has not incurred any credit losses.

Inventories and cost of product revenue

On August 4, 2014, the Company was notified that the European Commission, or EC, granted conditional marketing authorization for Translarna for the treatment of Duchenne muscular dystrophy caused by nonsense mutations, or nmDMD, in ambulatory patients aged five years and older. The conditional marketing authorization allows the Company to market Translarna in the European Economic Area, or EEA, which is comprised of the 28 member states of the European Union plus Norway, Iceland and Liechtenstein. The conditional marketing authorization is subject to an annual review by the European Medicines Agency, or EMA, and the Company will seek to renew the approval on an annual basis until the Company's obligations have been fulfilled and the approval is converted from a conditional approval into a full approval. The launch in these countries is on a country by country basis. The Company does do not have sufficient history or experience from which to accurately forecast product sales or demand generation. As such, the Company has not capitalized inventory and will not capitalize inventory until full approval has been obtained or until the Company can reasonably predict future product sales. The costs incurred related to the manufacturing of Translarna have been recorded as research and development expense in the statements of operations. The Company's cost of product sales includes royalties and other miscellaneous selling costs, which were not material for the year ended 2014 and therefore included as a component of research and development costs in the current year presentation. The time period over which this inventory is consumed will depend on a number of factors, including the amount of future Translarna sales, and the ability to utilize inventory prior to its expiration date.

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.

Accumulated other comprehensive income (loss)

Accumulated other comprehensive income (loss) consists of unrealized gains or losses on marketable securities and foreign currency translation adjustments.

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.

Net Product Sales

PTC's net product sales have consisted solely of sales of Translarna for the treatment of DMD caused by nonsense mutations. The Company applies the revenue recognition guidance in accordance with Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("ASC") Subtopic 605-15, Revenue Recognition—Products. The Company recognizes revenue from product sales when there is persuasive evidence that an arrangement exists, title to product and associated risk of loss has passed to the customer, the price is fixed or determinable, collectability is reasonably assured and the Company has no further performance obligations.

The Company has recorded revenue on sales where Translarna is available on a reimbursed early access program and typically paid for by a government authority or institution. The Company generally recognizes revenue for these named patient or cohort early access programs on a cash basis if all other revenue recognition criteria have been met. Once the Company has established a pattern of collectability, revenue will be recorded upon shipment assuming all other revenue recognition criteria are met.

The Company records revenue net of estimated discounts and rebates. Allowances are recorded as a reduction of revenue at the time revenues from product sales are recognized. Allowances for government rebates and discounts are established at the time of delivery. These allowances are adjusted to reflect known changes in factors and may impact such allowances in the quarter those changes are known.

Collaboration and Grant Revenue

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.

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 deferred research and development advance payments were $0.9 million as of December 31, 2014 and not significant as of December 31, 2013.

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 and investments are reflected in the accompanying financial statements at fair value. The carrying amount of 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 $0.4 million.

Warrant liability

Warrants to purchase the Company's common stock with nonstandard antidilution provisions, 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) 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, 2014.

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. Restricted stock awards are measured based on the fair market values of the underlying stock on the dates of grant. 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.

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 tax benefit

The Company recognized a tax benefit of $4.9 million related to the sale of net operating losses in the New Jersey Technology Business Tax Certificate Transfer Program for the year ended December 31, 2014. We did not participate in this program during the year ended December 31, 2013.

Net (loss) 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. During periods in which the Company incurs net losses, both basic and diluted loss per share is calculated by dividing the net loss by the weighted average shares outstanding—potentially dilutive securities are excluded from the calculation because their effect would be anti-dilutive. Dilutive common stock equivalents are comprised of convertible preferred stock and options outstanding under the Company's stock option plans.

In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers. ASU 2014-09 will eliminate transaction- and industry-specific revenue recognition guidance under current GAAP and replace it with a principle-based approach for determining revenue recognition. ASU 2014-09 will require that companies recognize revenue based on the value of transferred goods or services as they occur in the contract. The ASU also will require additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. ASU 2014-09 is effective for annual reporting periods beginning after December 15, 2016. Early application is not permitted. Entities can transition to the standard either retrospectively or as a cumulative-effect adjustment as of the date of adoption. Presently, the Company is assessing what effect the adoption of ASU 2014-09 will have on its financial statements and accompanying notes.

Fair value of financial instruments and investments

12 Months Ended

Dec. 31, 2014

Fair value of financial instruments and investments

Fair value of financial instruments and investments

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.

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 and liabilities that are required to be measured at fair value on a recurring basis as of December 31, 2014 and 2013:

	December 31, 2014
	Total		Quoted prices in active markets for identical assets (level 1)		Significant other observable inputs (level 2)		Significant unobservable inputs (level 3)
Marketable securities	$	265,493	$	—	$	265,493	$	—
Warrant liability	$	188	$	—	$	—	$	188

	December 31, 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	$	127,053	$	—	$	127,053	$	—
Warrant liability	$	58	$	—	$	—	$	58

The Company uses the market approach to measure fair value for its financial assets. The market approach uses prices and other relevant information generated by market transactions involving identical or comparable assets. The Company's marketable securities investments classified as Level 2 primarily utilize broker to value these securities. No transfers of assets between Level 1 and Level 2 of the fair value measurement hierarchy occurred during the year ended December 31, 2014.

The following is a summary of marketable securities accounted for as available-for-sale securities at December 31, 2014:

	December 31, 2014
			Gross Unrealized
	Amortized Cost		Gross Unrealized					Fair Value
	Amortized Cost		Gains		Losses			Fair Value
Corporate debt securities	$	230,379	$	80	$	(428	)	$	230,031
Government obligations		35,501		7		(46	)		35,462

	$	265,880	$	87	$	(474	)	$	265,493

	December 31, 2013
			Gross Unrealized
	Amortized Cost		Gross Unrealized					Fair Value
	Amortized Cost		Gains		Losses			Fair Value
Commercial paper	$	14,994	$	4	$	—		$	14,998
Corporate debt securities		111,989		97		(31	)		112,055

	$	126,983	$	101	$	(31	)	$	127,053

Unrealized gains and losses are reported as a component of accumulated other comprehensive (loss) income in stockholders' equity. During the year ended December 31, 2014, the Company did not have any realized gains/losses from the sale of marketable securities. The cost of securities sold is based on the specific identification method. The Company evaluates investments with unrealized losses to determine if the losses are other than temporary. At December 31, 2014, 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. In addition, the Company considered the financial condition, credit ratings and near-term prospects of the issuers, and the magnitude of the losses as compared to the cost and the length of time the investments have been in an unrealized loss position when determining if the losses are other than temporary.

Marketable securities on the balance sheet at December 31, 2014 mature as follows:

	December 31, 2014
	Less Than 12 Months		More Than 12 Months
U.S. corporate debt securities	$	157,758	$	72,273
Government Obligations		6,003		29,459

Total Marketable securities	$	163,761	$	101,732

Marketable securities on the balance sheet at December 31, 2013 matured as follows:

	December 31, 2013
	Less Than 12 Months		More Than 12 Months
Commercial paper	$	14,998	$	—
U.S. corporate debt securities		54,159		57,896

Total Marketable securities	$	69,157	$	57,896

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) 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, 2014 and 2013:

	Level 3 assets
Beginning balance January 1, 2013	$	96
Change in fair value of warrant liability		(38	)

Ending balance as of December 31, 2013	$	58
Change in fair value of warrant liability		130

Ending balance as of December 31, 2014	$	188

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, 2014 include (i) volatility (68-70%), (ii) risk free interest rate (0.89%-1.65%), (iii) strike price ($128.00-$2,520.00), (iv) fair value of common stock ($51.77) and (v) expected life (2.5-4.7 years).The significant assumptions used in preparing the option pricing model for valuing the Company's warrants as of December 31, 2013 include (i) volatility (61-89%), (ii) risk free interest rate (0.07%-2.1%), (iii) strike price ($128.00-$2,520.00), (iv) fair value of common stock($16.97) and (v) expected life (0.3-5.7 years).

- 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, 2014

Fixed assets

Fixed assets

4. Fixed assets

Fixed assets, net were as follows at December 31, 2014 and 2013:

	December 31,
	2014			2013
Leasehold improvements	$	13,051		$	12,474
Computer equipment and software		2,472			2,285
Furniture, fixtures, and lab equipment		15,070			14,284
Assets in process		3,483			369

		34,076			29,412
Less accumulated depreciation and amortization		(24,917	)		(22,682	)

	$	9,159		$	6,730

Depreciation expense was approximately $2.2 million, $2.4 million, and $2.7 million for the years ended December 31, 2014, 2013 and 2012, respectively.

Accounts payable and accrued expenses

12 Months Ended

Dec. 31, 2014

Accounts payable and accrued expenses

Accounts payable and accrued expenses

5. Accounts payable and accrued expenses

Accounts payable and accrued expenses at December 31, 2014 and 2013 consist of the following:

	December 31,
	2014		2013
Employee compensation, benefits, and related accruals	$	9,312	$	5,103
Consulting and contracted research		9,349		4,006
Professional fees		3,334		1,294
Accounts payable		4,128		1,124
Other		2,998		680

	$	29,121	$	12,207

Long-term debt	12 Months Ended
Long-term debt	Dec. 31, 2014
Long-term debt.
Long-term debt	6. Long-term debt In September 2009, the Company entered into a $25.0 million secured debt facility with a syndicate of two lenders. The Company borrowed $12.5 million under the facility in September 2009 and an additional $10.0 million under the facility in December 2010 and issued the lenders promissory notes. The notes were secured by substantially all of the Company's assets except for intellectual property. In July 2013, the Company paid in full the outstanding principal and interest of $2.6 million due under the promissory notes issued in connection with the secured debt facility. 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 year ended December 31, 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

12 Months Ended

Dec. 31, 2014

Capital structure

Capital structure

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 have been 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 did not declare any dividends through December 31, 2012.

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 $160.0 million represented 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.

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 One, Two and Three were as follows:

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

Liquidation—Upon the liquidation, dissolution, reorganization or winding-up of the Company, the holders of Series One would have been entitled to receive, before any distribution or payment was 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 had been excess assets to distribute, the holders of Series Two would have been be entitled to receive 76.47% of such excess assets, and the holders of Series One would have been entitled to receive 23.53% of such excess assets, until the holders of Series Two received 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 had been remaining assets after Series Two distributions, the holders of Series Three would have been entitled to receive 8.82% of such remaining assets, and the holders of Series One and Series Two would have been entitled to receive 23.53% and 67.65%, respectively, of such remaining assets, until the holders of Series Three received 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 had been remaining assets to distribute, the holders of Series One, Series Two, and Series Three would have been entitled to receive 20%, 55%, and 25% of such remaining assets, respectively.

Voting—Each holder of Series One was 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 have converted. Except as required by law, holders of Series Two and Series Three had limited voting rights. Additionally, the holders of Series One, voting as a single class, were entitled to elect twelve members of the Board of Directors.

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

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 and Series Two convertible preferred stock. 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 $6.0 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 another recapitalization event (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 $6.0 million raised with the bridge financing, total gross proceeds raised during the quarter ended March 31, 2013 was approximately $60.0 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 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 convertible preferred stock 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 convertible preferred stock. The gain of approximately $3.4 million represents the excess of the Series One, Series Two and Series Three convertible preferred stock 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.

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, were 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 would have been entitled to receive, before any distribution or payment was 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 had been excess assets to distribute, the holders of Series Five would have been entitled to receive, before any distribution or payment was 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 had been remaining assets to distribute, the holders of common stock would have been entitled to receive such remaining assets.

Voting—Each holder of Series Four and Series Five was entitled to cast the number of votes into which such holder's shares would have converted. Except as required by law, holders of common stock had limited voting rights. Additionally, except as required by law, and except in certain enumerated circumstances, holders of Series Four and Series Five would have voted 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 were 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.

Follow-On Offerings

In February 2014, the Company closed a follow-on 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 5,163,265 shares of common stock under the registration statement at a public offering price of $24.50 per share, including 673,469 shares pursuant to the exercise by the underwriters of an over-allotment option. The Company received net proceeds from the follow -on public offering of approximately $118.4 million, after deducting underwriting discounts and commissions and other offering expenses payable by the Company.

On October 16, 2014, the Company closed an underwritten public offering of its common stock pursuant to a registration statement on Form S-3. The Company issued and sold an aggregate of 3,450,000 shares of common stock under the registration statement at a public offering price of $36.25 per share, including 450,000 shares issued upon exercise by the underwriters of their option to purchase additional shares. The Company received net proceeds of approximately $117.6 million after deducting underwriting discounts and commissions and other offering expenses payable by the Company.

Warrants

All of the Company's outstanding warrants are classified as liabilities as of December 31, 2014 and 2013 because they contain non-standard antidilution provisions.

The following is a summary of the Company's outstanding warrants as of December 31, 2014:

	Warrant shares		Exercise price		Expiration
Common stock		6,250	$	128.00	2017
Common stock		7,030	$	128.00	2019 and 2020
Common stock		130	$	2,520.00	2019

The following is a summary of the Company's outstanding warrants as of December 31, 2013:

	Warrant shares		Exercise price		Expiration
Common stock		1,428	$	128.00	2014
Common stock		6,250	$	128.00	2017
Common stock		7,030	$	128.00	2019 and 2020
Common stock		452	$	2,520.00	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.

- 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))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 4.E)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74512-122707

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29-31)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB TOPIC 4.C)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187143-122770

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 8: 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 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23285-112656

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-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
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph d
-Article 4

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 29, 30, 31
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Reference 16: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

Reference 17: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Article 4

Reference 18: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section C

Reference 19: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Article 3

+ Details

Earnings per share

12 Months Ended

Dec. 31, 2014

Earnings per share

Earnings Per Share

8. Earnings 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 Prior Series Preferred outstanding in 2012 (through the date of the recapitalization) as well as the Series One, Series Two and Series Three outstanding during 2012 (subsequent to the recapitalization) participated in earnings of the Company through dividend rights. Accordingly, the Company measured earnings per share based upon the two-class method. Net income attributable to common stockholders excludes $132.6 million for the year ended 2012 for net income attributable to participating securities.

The diluted earnings per share for the year ended December 31, 2012 exclude the impact of approximately 0.6 million and 1.3 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 (loss) income per share

	Year ended December 31
	2014			2013			2012
Numerator
Net (loss) income	$	(93,753	)	$	(51,574	)	$	(26,235	)
Deemed dividend		—			(18,249	)		—
Gain on exchange of convertible preferred stock in connection with recapitalization		—			3,391			159,954
Less beneficial conversion charge		—			—			(378	)
Less net income attributable to participating preferred stock		—			—			(132,610	)

Net (loss) income attributable to common stockholders	$	(93,753	)	$	(66,432	)	$	731

Denominator
Denominator for basic earnings per share		31,565,310			12,829,411			3,328
Effect of dilutive securities:
Employee stock options		—			—			—
Series 3 convertible preferred stock		—			—			13,877

Denominator for diluted earnings per share		31,565,310			12,829,411			17,205

Net (loss) income per share:
Basic	$	(2.97	)	$	(5.18	)	$	219.76

Diluted	$	(2.97	)	$	(5.18	)	$	42.50

Stock award plan

12 Months Ended

Dec. 31, 2014

Stock award plan

Stock award plan

9. Stock award 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.

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 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. There are no additional shares available for issuance under this plan.

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) 262,044 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, 2009 Equity and Long Term Incentive 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. As of December 31, 2014, awards for 255,463 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.

Inducement stock option awards

Pursuant to the NASDAQ inducement grant exception, during the year ended December 31, 2014, the Company issued options to purchase an aggregate of 595,300 shares of common stock to certain new hire employees at a weighted-average exercise price of $37.15 per share. An aggregate of 5,900 of these options were forfeited during the year ended December 31, 2014 in connection with employee separations from the company.

A summary of stock option activity is as follows:

	Number of options			Exercise price	Weighted- average exercise price		Weighted- average remaining contractual term		Aggregate intrinsic value
									(in thousands)
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
Granted		2,117,113		$10.59 - $20.76	$	11.29
Exercised		—
Forfeited		(63,915	)	$10.85 - $1,149.60	$	12.57

Outstanding at December 31, 2013		2,095,592		$10.59 - $1,149.60	$	20.24		9.29 years

Granted		1,639,996		$18.78 - $50.45	$	31.09
Exercised		(108,645	)	$10.85 - $20.71	$	11.00
Forfeited		(193,971	)	$10.85 - $1,149.60	$	32.91

Outstanding at December 31, 2014		3,432,972		$10.59 - $1,149.60	$	25.00		8.77 years	$	106,796

Vested or expected to vest at December 31, 2014		3,239,515			$	24.15		8.78 years	$	101,391

Exercisable at December 31, 2014		764,277			$	31.84		8.24 years	$	29,809

There were no stock option exercises in 2012 or 2013.

The fair value of grants made in the years ended December 31, 2014, 2013 and 2012 was contemporaneously estimated on the date of grant using the following assumptions:

	2014	2013	2012
Risk-free interest rate	0.11 - 2.04%	0.85 - 1.90%	1.14%
Expected volatility	70 - 91%	87 - 89%	87%
Expected term	5.50 - 6.25 years	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, 2014, 2013 and 2012 was $22.39, $8.23, and $160.65, respectively.

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.

The following table summarizes stock options outstanding and exercisable at December 31, 2014:

	Outstanding						Exercisable
Range of Exercise Price	Number of Options		Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Life (in years)		Number of Options		Weighted Average Exercise Price
$10.59 - $10.85		1,752,630	$	10.85		8.37		704,958	$	10.85
$10.85 - $20.76		114,425	$	19.42		8.90		28,675	$	19.72
$20.76 - $27.05		982,796	$	26.91		9.12		350	$	27.05
$27.05 - $50.45		554,400	$	39.25		9.62		2,968	$	40.45
$50.45 - $1,149.60		28,721	$	569.97		4.32		27,326	$	585.05

		3,432,972						764,277

In December 2013, the Compensation Committee of the Board of Directors modified the terms of stock options granted to executive management. Under the modified terms, the Committee waived all remaining performance conditions associated with the initial vesting of the options such that the options vest with service only conditions. The Company accounted for the modification to the option grants pursuant to ASC Topic 718-20-35 and recognized approximately $0.6 million as additional compensation that was charged to operations during the period ended December 31, 2013.

In 2014, the Company modified the terms of stock options granted to a departing member of the executive team. The Company accounted for the modification to the option grants pursuant to ASC Topic 718-20-35 and recognized approximately $1.9 million as additional compensation that was charged to operations during the year ended December 31, 2014.

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, 2014		1,110,226		$	10.68
Granted		—			—
Vested		(373,200	)	$	10.59
Forfeited		(18,626	)	$	10.75

Unvested at December 31, 2014		718,400		$	10.72

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

	Year ended December 31,
	2014		2013		2012
Research and development	$	9,739	$	4,312	$	1,269
Selling, general and administrative		9,571		4,115		1,020

Total	$	19,310	$	8,427	$	2,289

As of December 31, 2014, there was approximately $38.4 million of total unrecognized compensation cost related to unvested share-based compensation arrangements granted under the Company's Plans. This cost is expected to be recognized as compensation expense over the weighted average remaining service period of approximately 2.66 years.

Other comprehensive income (loss) and accumulated other comprehensive items

12 Months Ended

Dec. 31, 2014

Other comprehensive income (loss) and accumulated other comprehensive items

Other comprehensive income (loss) and accumulated other comprehensive items

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

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

The following table summarizes other comprehensive income (loss) and the changes in accumulated other comprehensive items, by component, for the years ended December 31, 2014, 2013, and 2012, respectively.

	Unrealized Gains On Marketable Securities			Foreign Currency Translation			Total Accumulated Other Comprehensive Items
Balance at December, 2011	$	—		$	—		$	—
Other comprehensive income/(loss) before reclassifications		—			—			—
Amounts reclassified from other comprehensive items		—			—			—
Other comprehensive income/(loss)		—			—			—

Balance at December 31, 2012	$	—		$	—		$	—
Other comprehensive income before reclassifications		70			—			70
Amounts reclassified from other comprehensive items		—			—			—

Other comprehensive income		70			—			70

Balance at December 31, 2013	$	70		$	—		$	70
Other comprehensive loss before reclassifications		(457	)		(350	)		(807	)
Amounts reclassified from other comprehensive items		—			—			—

Other comprehensive loss		(387	)		(350	)		(737	)

Balance at December 31, 2014	$	(387	)	$	(350	)	$	(737	)

- 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=36458714&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=36458714&loc=SL7669619-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e640-108580

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e716-108580

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e709-108580

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
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-Section S99
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-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
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-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e637-108580

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=36458714&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

Collaborations and grants	12 Months Ended
Collaborations and grants	Dec. 31, 2014
Collaborations and grants
Collaborations and grants	11. 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. The following are the key terms to the Company's (i) ongoing collaborations and (ii) early stage discovery and development arrangements. 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 $30.0 million during the research term, which was terminated effective December 31, 2014, Roche provided us with funding, based on an agreed-upon full-time equivalent rate, for an agreed-upon number of full-time equivalent employees that we contributed to the research program. The Company applied the 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 $30.0 million upfront payment which was recognized over the estimated performance period of two years, which was the contracted research period. For the years ended December 31, 2014, 2013 and 2012, the Company recognized approximately $20.2 million, $26.6 million and $18.4 million respectively, in collaboration revenue. The balance of the remaining deferred upfront payment was fully recognized as of December 31, 2013. 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. In January 2014, the Company announced the initiation of a Phase 1 clinical program in its spinal muscular atrophy collaboration with Roche and the SMA Foundation which triggered a $7.5 million milestone payment from Roche. The Company considered this milestone event substantive because the applicable criteria of its revenue recognition policy would be satisfied and recorded it as collaboration revenue for the year ended December 31, 2014. In November 2014, the Company announced the initiation of a Phase 2 study in adult and pediatric patients in its spinal muscular atrophy collaboration with Roche and the SMA Foundation which triggered a $10 million payment from Roche. The Company considered this milestone event substantive because the applicable criteria of its revenue recognition policy would be satisfied and recorded it as collaboration revenue for the year ended December 31, 2014. Early stage collaboration and discovery agreements From time to time, 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. The Company applies 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. Since the Company's discovery technologies are highly specialized, the Company has generally determined that the license does not have standalone value without the ongoing research and development services and generally accounts for these arrangements as a single unit of accounting. As a result, the Company has deferred revenue of $1.8 million and $0.9 million as of December 31, 2014 and 2013, respectively, related to these arrangements. For the years ended December 31, 2014 and 2013, the Company recognized approximately $1.3 million and $4.8 million 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, 2014

Income taxes

Income taxes

12. Income taxes

Income Taxes

The Income Tax Provision consisted of the following for the years ended December 31, 2014 and December 31, 2013:

	2014			2013
Current:
U.S. Federal	$	—		$	—
U.S. State and Local		(4,890	)		2
Foreign		197			—

	$	(4,693	)	$	2

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

				December 31,
	2014			2013			2012
Federal income tax (benefit) at statutory rate		34.00	%		34.00	%		34.00	%
State income tax benefit, net of federal benefit		(1.60	)		5.65			3.80
Permanent differences		(0.93	)		(5.90	)		—
NOL IRC Section 382 Limitations		(21.53	)		—			—
Research and development		3.78			15.88			—
Increase to valuation allowance		9.17			(49.63	)		(35.80	)
Foreign Taxes		(18.14	)		—			—
Other		0.01			—			(2.00	)

Effective income tax rate		4.76	%		0.00	%		0.00	%

The significant components of the Company's deferred tax assets and liabilities at December 31, 2014 and 2013 are as follows:

	2014			2013
Current:
Accrued Expense	$	611		$	333
Deferred tax assets:
Amortization		69			80
Depreciation		2,268			1,922
Deferred revenue		699			350
Federal tax credits		17,807			14,082
State tax credits		1,274			1,587
Federal net operating losses		76,933			88,188
State net operating losses		9,185			10,457
Capitalized research and development costs		10,585			12,254
Other		3,852			3,212

Total gross deferred tax assets		123,283			132,465
Less valuation allowance		(123,283	)		(132,465	)

Net deferred tax assets	$	—		$	—

At December 31, 2014 and 2013, the Company recorded a full valuation allowance against its net deferred tax assets of approximately $123.3 million and $132.5 million, respectively. The change in the valuation allowance during the years ended December 31, 2014 and 2013 was approximately $9.2 million and $25.6 million, 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, 2014, the Company has approximately $226.3 million and $154.6 million of federal and state net operating loss carryforwards, respectively. As of December 31, 2014, credit carryforwards for federal and state purposes are approximately $6.5 million and $1.7 million, respectively. In addition the Orphan Drug Credit Carryover available as of December 31, 2013 is approximately $11.4 million. The federal net operating loss carryforwards begin to expire in 2021, while the federal credit carryforwards begin to expire in 2019. State net operating loss carryforwards begin to expire in 2030, and the state credit carryforwards begin to expire in 2015. 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 undergone an ownership change and has determined that a "change in ownership" as defined by IRC Section 382 of the Internal Revenue Code of 1986, as amended, and the rules and regulations promulgated thereunder, did occur in June of 2013. Accordingly, about $231.5 million of the Company's NOL carryforwards are limited and the Company can only use $16.7 million for the first five years from the ownership change and $5.7 million per year going forward. Therefore, $169.2 million of the NOL's will be freed up over the next 20 years and $62.3 million are expected to expire unused which are not included in the deferred tax assets listed above. In summary, there are $226.1 million of NOLs available, out of which $169.2 million are limited by IRC Section 382. At December 31, 2014, there is $82.1 million available for immediate use and an additional $16.7 million will free up in 2015.

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 and research and development credits totaling $50.4 million during 2014. The New Jersey net operating losses and research and development credits sold during 2014 were generated in 2007 through 2010. The Company recognized a tax benefit of $4.9 million for the year ended December 31, 2014. The company did not participate in this program during the year ended December 31, 2013.

The income tax benefit for the years ended December 31, 2013 and 2014 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 nondeductible expenses, tax credits generated, utilization of net operating loss carryforwards, and increases in the Company's valuation allowance. The Company applies the elements of FASB ASC 740-10 "Income Taxes—Overall" regarding accounting for uncertainty in income taxes. This clarifies the accounting for uncertainty in income taxes recognized in financial statements and required 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, 2014 the company did not have any unrecognized tax benefits and has not accrued any interest or penalties through 2014. 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 2011 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.

For all years through December 31, 2014, the Company generated research credits but has not conducted a study to document the qualified activities. This study may result in an adjustment to the Company's research and development credit carryforwards; however, until a study is completed and any adjustment is known, no amounts are being presented as an uncertain tax position for the last two years. A full valuation allowance has been provided against the Company's research and development credits and, if an adjustment is required, this adjustment would be offset by an adjustment to the deferred tax asset established for the research and development credit carryforwards and the valuation allowance.

In July 2013, the FASB issued amended guidance for the presentation of an unrecognized tax benefit when a net operating loss carry forward exits, which is effective for the Company January 1, 2014. This amended guidance requires an entity to present an unrecognized tax benefit as a reduction of a deferred tax asset for a net operating carry forward, a similiar tax loss or a tax credit carry forward. If an applicable deferred tax asset is not available or a company does not expect to use the applicable deferred tax asset, the unrecognized tax benefit should be presented as a liability in the financial statements and should not be combined wth an unrelated deferred tax asset. The Company does not expect the adoption of this amended guidance to have a significant impact on the consolidated financial statements.

Commitments and contingencies

12 Months Ended

Dec. 31, 2014

Commitments and contingencies

Commitments and contingencies

13. Commitments and contingencies

Operating leases

The Company leases office space under a noncancelable operating lease through February 2019. Rent expense was approximately $0.9 million for the years ended December 31, 2014, and $0.7 million for the years ended 2013 and 2012. The Company also leases certain office equipment under operating leases. Future minimum lease payments as of December 31, 2014 are as follows:

2015	$	1,268
2016		932
2017		923
2018		1,035
2019		176
Thereafter		—

	$	4,334

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.

Geographic Segments

12 Months Ended

Dec. 31, 2014

Geographic Segments

Geographic segments

14. Geographic Segments

The Company views its operations and manages its business in one operating segment. The following table presents financial information based on the geographic location of the facilities of the company as of and for the years ended:

	Year ended December 31, 2014
	United States		Non-US		Total
Total assets	$	330,663	$	2,556	$	333,219
Property and equipment, net	$	8,555	$	604	$	9,159
Revenue	$	25,245	$	—	$	25,245

	Year ended December 31, 2013
	United States		Non-US		Total
Total assets	$	151,903	$	—	$	151,903
Property and equipment, net	$	6,730	$	—	$	6,730
Revenue	$	34,696	$	—	$	34,696

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8981-108599

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9038-108599

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8971-108599

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8595-108599

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8380-108599

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8933-108599

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 26
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8844-108599

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 35
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8984-108599

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9031-108599

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9054-108599

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8538-108599

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 29
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8864-108599

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8924-108599

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8906-108599

+ Details

401(k) plan	12 Months Ended
401(k) plan	Dec. 31, 2014
401(k) plan
401(k) plan	15. 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 33% matching contribution for up to the first 6% of each contributing employee's base salary contributions. The Company made matching contributions to the 401(k) plan and recorded expense of approximately $0.3 million, $0.1 million and $0.2 million for the years ended December 31, 2014, 2013 and 2012, respectively.

Subsequent events	12 Months Ended
Subsequent events	Dec. 31, 2014
Subsequent events
Subsequent events	16. Subsequent events The Company has evaluated all events or transactions that occurred after December 31, 2014. In the judgment of management, there were no material events that impacted the consolidated financial statements or disclosures.

Selected quarterly financial data

12 Months Ended

Dec. 31, 2014

Selected quarterly financial data

Selected quarterly financial data

17. 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. Summarized quarterly data for 2014 and 2013 are as follows:

	For the quarters ending
	March 31			June 30			September 30			December 31
2014:
Net product sales	$	—		$	—		$	81		$	636
Collaboration and grant revenue		9,217			1,677			1,613			12,022
Operating expenses		23,429			27,046			29,295			44,888
Loss from operations		(14,212	)		(25,369	)		(27,601	)		(32,230	)
Net loss attributable to common stockholders		(14,098	)		(25,104	)		(27,282	)		(27,269	)
Basic net loss per common share(1)	$	(0.58	)	$	(0.86	)	$	(0.93	)	$	(0.84	)
Diluted net loss per common share(1)	$	(0.58	)	$	(0.86	)	$	(0.93	)	$	(0.84	)
2013:
Collaboration and grant revenue	$	7,142		$	6,854		$	16,290		$	4,411
Operating expenses		15,718			21,307			20,565			22,503
Loss from operations		(8,576	)		(14,453	)		(4,276	)		(18,093	)
Net loss		(14,685	)		(14,587	)		(4,416	)		(17,886	)
Deemed dividend		(18,249	)		—			—			—
Gain on exchange of convertible preferred stock in connection with recapitalization		3,391			—			—			—
Net income (loss) attributable to common stockholders		(29,543	)		(14,587	)		(4,416	)		(17,886	)
Basic net income (loss) per common share(1)	$	(6,527.30	)	$	(5.51	)	$	(0.19	)	$	(0.75	)
Diluted net income (loss) per common share(1)	$	(6,527.30	)	$	(5.51	)	$	(0.19	)	$	(0.75	)

(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)

12 Months Ended

Dec. 31, 2014

Summary of significant accounting policies

Basis of presentation

Use of estimates

Consolidation

Segment and geographic information

Cash equivalents

Marketable securities

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

Concentration of credit risks

Concentration of credit risk

Inventories and cost of product revenue

Deferred rent

Accumulated other comprehensive income (loss)

Accumulated other comprehensive income (loss) consists of unrealized gains or losses on marketable securities and foreign currency translation adjustments.

Revenue recognition

Net Product Sales

Collaboration and Grant Revenue

Research and development costs

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.

Beneficial conversion

Warrant liability

Impairment of long-lived assets

Share-based compensation

Income taxes

Net tax benefit

Net (loss) income per share

Summary of significant accounting policies (Tables)

12 Months Ended

Dec. 31, 2014

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)

12 Months Ended

Dec. 31, 2014

Fair value of financial instruments and investments

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

	December 31, 2014
	Total		Quoted prices in active markets for identical assets (level 1)		Significant other observable inputs (level 2)		Significant unobservable inputs (level 3)
Marketable securities	$	265,493	$	—	$	265,493	$	—
Warrant liability	$	188	$	—	$	—	$	188

	December 31, 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	$	127,053	$	—	$	127,053	$	—
Warrant liability	$	58	$	—	$	—	$	58

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

	December 31, 2014
			Gross Unrealized
	Amortized Cost		Gross Unrealized					Fair Value
	Amortized Cost		Gains		Losses			Fair Value
Corporate debt securities	$	230,379	$	80	$	(428	)	$	230,031
Government obligations		35,501		7		(46	)		35,462

	$	265,880	$	87	$	(474	)	$	265,493

	December 31, 2013
			Gross Unrealized
	Amortized Cost		Gross Unrealized					Fair Value
	Amortized Cost		Gains		Losses			Fair Value
Commercial paper	$	14,994	$	4	$	—		$	14,998
Corporate debt securities		111,989		97		(31	)		112,055

	$	126,983	$	101	$	(31	)	$	127,053

Schedule of marketable securities on the balance sheet

	December 31, 2014
	Less Than 12 Months		More Than 12 Months
U.S. corporate debt securities	$	157,758	$	72,273
Government Obligations		6,003		29,459

Total Marketable securities	$	163,761	$	101,732

Marketable securities on the balance sheet at December 31, 2013 matured as follows:

	December 31, 2013
	Less Than 12 Months		More Than 12 Months
Commercial paper	$	14,998	$	—
U.S. corporate debt securities		54,159		57,896

Total Marketable securities	$	69,157	$	57,896

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

	Level 3 assets
Beginning balance January 1, 2013	$	96
Change in fair value of warrant liability		(38	)

Ending balance as of December 31, 2013	$	58
Change in fair value of warrant liability		130

Ending balance as of December 31, 2014	$	188

Fixed assets (Tables)

12 Months Ended

Dec. 31, 2014

Fixed assets

Schedule of fixed assets, net

	December 31,
	2014			2013
Leasehold improvements	$	13,051		$	12,474
Computer equipment and software		2,472			2,285
Furniture, fixtures, and lab equipment		15,070			14,284
Assets in process		3,483			369

		34,076			29,412
Less accumulated depreciation and amortization		(24,917	)		(22,682	)

	$	9,159		$	6,730

Accounts payable and accrued expenses (Tables)

12 Months Ended

Dec. 31, 2014

Accounts payable and accrued expenses

Schedule of components of accounts payable and accrued expenses

	December 31,
	2014		2013
Employee compensation, benefits, and related accruals	$	9,312	$	5,103
Consulting and contracted research		9,349		4,006
Professional fees		3,334		1,294
Accounts payable		4,128		1,124
Other		2,998		680

	$	29,121	$	12,207

Capital structure (Tables)

12 Months Ended

Dec. 31, 2014

Capital structure

Summary of the Company's outstanding warrants

	Warrant shares		Exercise price		Expiration
Common stock		6,250	$	128.00	2017
Common stock		7,030	$	128.00	2019 and 2020
Common stock		130	$	2,520.00	2019

The following is a summary of the Company's outstanding warrants as of December 31, 2013:

	Warrant shares		Exercise price		Expiration
Common stock		1,428	$	128.00	2014
Common stock		6,250	$	128.00	2017
Common stock		7,030	$	128.00	2019 and 2020
Common stock		452	$	2,520.00	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)

12 Months Ended

Dec. 31, 2014

Earnings per share

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

	Year ended December 31
	2014			2013			2012
Numerator
Net (loss) income	$	(93,753	)	$	(51,574	)	$	(26,235	)
Deemed dividend		—			(18,249	)		—
Gain on exchange of convertible preferred stock in connection with recapitalization		—			3,391			159,954
Less beneficial conversion charge		—			—			(378	)
Less net income attributable to participating preferred stock		—			—			(132,610	)

Net (loss) income attributable to common stockholders	$	(93,753	)	$	(66,432	)	$	731

Denominator
Denominator for basic earnings per share		31,565,310			12,829,411			3,328
Effect of dilutive securities:
Employee stock options		—			—			—
Series 3 convertible preferred stock		—			—			13,877

Denominator for diluted earnings per share		31,565,310			12,829,411			17,205

Net (loss) income per share:
Basic	$	(2.97	)	$	(5.18	)	$	219.76

Diluted	$	(2.97	)	$	(5.18	)	$	42.50

Stock option plan (Tables)

12 Months Ended

Dec. 31, 2014

Stock award plan

Summary of stock option activity

	Number of options			Exercise price	Weighted- average exercise price		Weighted- average remaining contractual term		Aggregate intrinsic value
									(in thousands)
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
Granted		2,117,113		$10.59 - $20.76	$	11.29
Exercised		—
Forfeited		(63,915	)	$10.85 - $1,149.60	$	12.57

Outstanding at December 31, 2013		2,095,592		$10.59 - $1,149.60	$	20.24		9.29 years

Granted		1,639,996		$18.78 - $50.45	$	31.09
Exercised		(108,645	)	$10.85 - $20.71	$	11.00
Forfeited		(193,971	)	$10.85 - $1,149.60	$	32.91

Outstanding at December 31, 2014		3,432,972		$10.59 - $1,149.60	$	25.00		8.77 years	$	106,796

Vested or expected to vest at December 31, 2014		3,239,515			$	24.15		8.78 years	$	101,391

Exercisable at December 31, 2014		764,277			$	31.84		8.24 years	$	29,809

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

	2014	2013	2012
Risk-free interest rate	0.11 - 2.04%	0.85 - 1.90%	1.14%
Expected volatility	70 - 91%	87 - 89%	87%
Expected term	5.50 - 6.25 years	6.00 - 6.25 years	6.00 - 6.25 years

Summary of stock options outstanding and exercisable

The following table summarizes stock options outstanding and exercisable at December 31, 2014:

	Outstanding						Exercisable
Range of Exercise Price	Number of Options		Weighted- Average Exercise Price		Weighted-Average Remaining Contractual Life (in years)		Number of Options		Weighted Average Exercise Price
$10.59 - $10.85		1,752,630	$	10.85		8.37		704,958	$	10.85
$10.85 - $20.76		114,425	$	19.42		8.90		28,675	$	19.72
$20.76 - $27.05		982,796	$	26.91		9.12		350	$	27.05
$27.05 - $50.45		554,400	$	39.25		9.62		2,968	$	40.45
$50.45 - $1,149.60		28,721	$	569.97		4.32		27,326	$	585.05

		3,432,972						764,277

Summary of information on the Company's restricted stock

	Restricted Stock
	Number of Shares			Weighted Average Grant Date Fair Value
January 1, 2014		1,110,226		$	10.68
Granted		—			—
Vested		(373,200	)	$	10.59
Forfeited		(18,626	)	$	10.75

Unvested at December 31, 2014		718,400		$	10.72

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

	Year ended December 31,
	2014		2013		2012
Research and development	$	9,739	$	4,312	$	1,269
Selling, general and administrative		9,571		4,115		1,020

Total	$	19,310	$	8,427	$	2,289

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

12 Months Ended

Dec. 31, 2014

Other comprehensive income (loss) and accumulated other comprehensive items

Summary of other comprehensive income (loss) and the changes in accumulated other comprehensive items

	Unrealized Gains On Marketable Securities			Foreign Currency Translation			Total Accumulated Other Comprehensive Items
Balance at December, 2011	$	—		$	—		$	—
Other comprehensive income/(loss) before reclassifications		—			—			—
Amounts reclassified from other comprehensive items		—			—			—
Other comprehensive income/(loss)		—			—			—

Balance at December 31, 2012	$	—		$	—		$	—
Other comprehensive income before reclassifications		70			—			70
Amounts reclassified from other comprehensive items		—			—			—

Other comprehensive income		70			—			70

Balance at December 31, 2013	$	70		$	—		$	70
Other comprehensive loss before reclassifications		(457	)		(350	)		(807	)
Amounts reclassified from other comprehensive items		—			—			—

Other comprehensive loss		(387	)		(350	)		(737	)

Balance at December 31, 2014	$	(387	)	$	(350	)	$	(737	)

Income taxes (Tables)

12 Months Ended

Dec. 31, 2014

Income taxes

Components of Income Tax Provision

	2014			2013
Current:
U.S. Federal	$	—		$	—
U.S. State and Local		(4,890	)		2
Foreign		197			—

	$	(4,693	)	$	2

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

				December 31,
	2014			2013			2012
Federal income tax (benefit) at statutory rate		34.00	%		34.00	%		34.00	%
State income tax benefit, net of federal benefit		(1.60	)		5.65			3.80
Permanent differences		(0.93	)		(5.90	)		—
NOL IRC Section 382 Limitations		(21.53	)		—			—
Research and development		3.78			15.88			—
Increase to valuation allowance		9.17			(49.63	)		(35.80	)
Foreign Taxes		(18.14	)		—			—
Other		0.01			—			(2.00	)

Effective income tax rate		4.76	%		0.00	%		0.00	%

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

	2014			2013
Current:
Accrued Expense	$	611		$	333
Deferred tax assets:
Amortization		69			80
Depreciation		2,268			1,922
Deferred revenue		699			350
Federal tax credits		17,807			14,082
State tax credits		1,274			1,587
Federal net operating losses		76,933			88,188
State net operating losses		9,185			10,457
Capitalized research and development costs		10,585			12,254
Other		3,852			3,212

Total gross deferred tax assets		123,283			132,465
Less valuation allowance		(123,283	)		(132,465	)

Net deferred tax assets	$	—		$	—

Commitments and contingencies (Tables)

12 Months Ended

Dec. 31, 2014

Commitments and contingencies

Schedule of future minimum lease payments

2015	$	1,268
2016		932
2017		923
2018		1,035
2019		176
Thereafter		—

	$	4,334

Geographic segments (Tables)

12 Months Ended

Dec. 31, 2014

Geographic Segments

Summary of financial information based on geographical location

	Year ended December 31, 2014
	United States		Non-US		Total
Total assets	$	330,663	$	2,556	$	333,219
Property and equipment, net	$	8,555	$	604	$	9,159
Revenue	$	25,245	$	—	$	25,245

	Year ended December 31, 2013
	United States		Non-US		Total
Total assets	$	151,903	$	—	$	151,903
Property and equipment, net	$	6,730	$	—	$	6,730
Revenue	$	34,696	$	—	$	34,696

Selected quarterly financial data (Tables)

12 Months Ended

Dec. 31, 2014

Selected quarterly financial data

Summary of quarterly data

	For the quarters ending
	March 31			June 30			September 30			December 31
2014:
Net product sales	$	—		$	—		$	81		$	636
Collaboration and grant revenue		9,217			1,677			1,613			12,022
Operating expenses		23,429			27,046			29,295			44,888
Loss from operations		(14,212	)		(25,369	)		(27,601	)		(32,230	)
Net loss attributable to common stockholders		(14,098	)		(25,104	)		(27,282	)		(27,269	)
Basic net loss per common share(1)	$	(0.58	)	$	(0.86	)	$	(0.93	)	$	(0.84	)
Diluted net loss per common share(1)	$	(0.58	)	$	(0.86	)	$	(0.93	)	$	(0.84	)
2013:
Collaboration and grant revenue	$	7,142		$	6,854		$	16,290		$	4,411
Operating expenses		15,718			21,307			20,565			22,503
Loss from operations		(8,576	)		(14,453	)		(4,276	)		(18,093	)
Net loss		(14,685	)		(14,587	)		(4,416	)		(17,886	)
Deemed dividend		(18,249	)		—			—			—
Gain on exchange of convertible preferred stock in connection with recapitalization		3,391			—			—			—
Net income (loss) attributable to common stockholders		(29,543	)		(14,587	)		(4,416	)		(17,886	)
Basic net income (loss) per common share(1)	$	(6,527.30	)	$	(5.51	)	$	(0.19	)	$	(0.75	)
Diluted net income (loss) per common share(1)	$	(6,527.30	)	$	(5.51	)	$	(0.19	)	$	(0.75	)

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

The Company (Details) $ in Thousands	12 Months Ended
The Company (Details) $ in Thousands	Dec. 31, 2014 USD ($) item	Dec. 31, 2013 USD ($)
The Company
Accumulated deficit \| $	$ 422,551	$ 328,798
Minimum age of ambulatory patient	5 years
Number of member states of the European Union \| item	31

Summary of significant accounting policies (Details)	12 Months Ended
Summary of significant accounting policies (Details)	Dec. 31, 2014 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 3)		12 Months Ended
Summary of significant accounting policies (Details 3)	Mar. 07, 2013	Dec. 31, 2014 USD ($)	Dec. 31, 2012 USD ($)
Research and development costs
Deferred research and development advance payments		$ 900,000
Beneficial conversion
Beneficial conversion charge			$ 378,000
Impairment of long-lived assets
Impairment of long-lived assets		0
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Net tax benefit		4,693,000
New Jersey
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Net tax benefit		$ 4,900,000
Common stock
Reverse Stock Split [Abstract]
Reverse stock split ratio	0.0083

Fair value of financial instruments and investments (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Financial assets and liabilities measured at fair value on recurring basis
Marketable securities	$ 265,493	$ 127,053
Recurring basis \| Total
Financial assets and liabilities measured at fair value on recurring basis
Marketable securities	265,493	127,053
Warrant liability	188	58
Recurring basis \| Significant other observable inputs (level 2)
Financial assets and liabilities measured at fair value on recurring basis
Marketable securities	265,493	127,053
Recurring basis \| Significant unobservable inputs (level 3)
Financial assets and liabilities measured at fair value on recurring basis
Warrant liability	$ 188	$ 58

Fair value of financial instruments and investments (Details 2) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Fair value of financial instruments and investments
Transfers of assets between Level 1 and Level 2 of the fair value measurement hierarchy	$ 0
Marketable securities accounted for as available-for-sale securities
Amortized Cost	265,880	$ 126,983
Gross Unrealized Gains	87	101
Gross Unrealized Losses	(474)	(31)
Total Marketable securities	265,493	127,053
Commercial paper
Marketable securities accounted for as available-for-sale securities
Amortized Cost		14,994
Gross Unrealized Gains		4
Total Marketable securities		14,998
Corporate Debt Securities [Member]
Marketable securities accounted for as available-for-sale securities
Amortized Cost	230,379	111,989
Gross Unrealized Gains	80	97
Gross Unrealized Losses	(428)	(31)
Total Marketable securities	230,031	$ 112,055
Government Agencies Debt Securities [Member]
Marketable securities accounted for as available-for-sale securities
Amortized Cost	35,501
Gross Unrealized Gains	7
Gross Unrealized Losses	(46)
Total Marketable securities	$ 35,462

Fair value of financial instruments and investments (Details 3) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Marketable securities on the balance sheet
Total Marketable securities, Less Than 12 Months	$ 163,761	$ 69,157
Total Marketable securities, More Than 12 Months	101,732	57,896
Commercial paper
Marketable securities on the balance sheet
Total Marketable securities, Less Than 12 Months		14,998
U.S. corporate debt securities
Marketable securities on the balance sheet
Total Marketable securities, Less Than 12 Months	157,758	54,159
Total Marketable securities, More Than 12 Months	72,273	$ 57,896
Government Agencies Debt Securities [Member]
Marketable securities on the balance sheet
Total Marketable securities, Less Than 12 Months	6,003
Total Marketable securities, More Than 12 Months	$ 29,459

Fair value of financial instruments and investments (Details 4) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2013
Common stock
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model
Fair value of shares (in dollars per share)			$ 15.00
Warrant
Changes in the fair value of warrant liability
Beginning balance	$ 58	$ 96
Change in fair value of warrant liability	130	(38)
Ending balance	$ 188	$ 58
Warrant \| Minimum
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model
Volatility (as a percent)	68.00%	61.00%
Risk-free interest rate (as a percent)	0.89%	0.07%
Strike price (in dollars per share)	$ 128.00	$ 128.00
Expected life	2 years 6 months	3 months 18 days
Warrant \| Maximum
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model
Volatility (as a percent)	70.00%	89.00%
Risk-free interest rate (as a percent)	1.65%	2.10%
Strike price (in dollars per share)	$ 2,520.00	$ 2,520.00
Expected life	4 years 8 months 12 days	5 years 8 months 12 days
Warrant \| Common stock
Assumption used to estimate the fair value of warrant liability by utilizing the Black-Scholes option-pricing model
Fair value of shares (in dollars per share)	$ 51.77	$ 16.97

Fixed assets (Details) - USD ($) $ in Thousands	12 Months Ended
Fixed assets (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fixed assets
Gross fixed assets	$ 34,076	$ 29,412
Less accumulated depreciation and amortization	(24,917)	(22,682)
Net fixed assets	9,159	6,730
Depreciation expense	2,235	2,396	$ 2,704
Leasehold improvements
Fixed assets
Gross fixed assets	13,051	12,474
Computer equipment and software
Fixed assets
Gross fixed assets	2,472	2,285
Furniture, fixtures, and lab equipment
Fixed assets
Gross fixed assets	15,070	14,284
Assets in process
Fixed assets
Gross fixed assets	$ 3,483	$ 369

Accounts payable and accrued expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013
Accounts payable and accrued expenses
Employee compensation, benefits, and related accruals	$ 9,312	$ 5,103
Consulting and contracted research	9,349	4,006
Professional fees	3,334	1,294
Accounts payable	4,128	1,124
Other	2,998	680
Accounts payable and accrued expenses	$ 29,121	$ 12,207

Long-term debt (Details) $ in Thousands	1 Months Ended			12 Months Ended
Long-term debt (Details) $ in Thousands	Jul. 31, 2013 USD ($)	Dec. 31, 2010 USD ($)	Sep. 30, 2009 USD ($) item	Dec. 31, 2013 USD ($)
Debt
Paid outstanding principal and interest, due under promissory notes issued	$ 2,600
Gains (Losses) on Extinguishment of Debt				$ (130)
Secured debt facility
Debt
Maximum borrowing capacity			$ 25,000
Amount borrowed		$ 10,000	$ 12,500
Number of lenders \| item			2

Capital structure (Details)	1 Months Ended	3 Months Ended	12 Months Ended
Capital structure (Details)	Jul. 31, 2012 USD ($)	Mar. 31, 2013 USD ($)	Dec. 31, 2013 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
Proceeds from Issuance of Convertible Preferred Stock \| $				$ 29,355,000
Preferred Stock Redemption Discount \| $	$ 160,000,000	$ 3,391,000	$ 3,391,000	$ 159,954,000
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 convertible preferred stock
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 convertible preferred stock
Capital structure
Number of members of board of directors who can be elected by holders of the preferred stock, voting as a single class \| item				12
Stock Issued During Period, Shares, New Issues				1,483,337
Proceeds from Issuance of Convertible Preferred Stock \| $				$ 29,700,000
Original issuance price multiplier \| item				2
Assets available for distribution to series convertible preferred stock, distribution percentage				23.53%
Assets available for distribution to series convertible preferred stock, distribution percentage.				23.53%
Remaining assets distribution percentage				20.00%
Shares issued upon conversion of preferred stock multiplier \| item				5
Convertible Preferred Stock, Shares Issued upon Conversion				2
Series Two convertible preferred stock
Capital structure
Assets available for distribution to series convertible preferred stock, distribution percentage				76.47%
Stated liquidation preference amount multiplier \| item				1
Assets available for distribution to series convertible preferred stock, distribution percentage.				67.65%
Remaining assets distribution percentage				55.00%
Convertible Preferred Stock, Shares Issued upon Conversion				1
Series Three convertible preferred stock
Capital structure
Stated liquidation preference amount multiplier \| item				1
Assets available for distribution to series convertible preferred stock, distribution percentage.				8.82%
Remaining assets distribution percentage				25.00%
Convertible Preferred Stock, Shares Issued upon Conversion				1

Capital structure (Details 2)			1 Months Ended				3 Months Ended		12 Months Ended
Capital structure (Details 2)	Oct. 16, 2014 USD ($) $ / shares shares	Mar. 07, 2013 USD ($) shares	Feb. 28, 2014 USD ($) $ / shares shares	Jun. 30, 2013 USD ($) $ / shares shares	May 31, 2013 USD ($) $ / shares shares	Jul. 31, 2012 USD ($)	Mar. 31, 2014 USD ($)	Mar. 31, 2013 USD ($)	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($) shares	Dec. 31, 2012 USD ($)	Feb. 28, 2013 USD ($) $ / shares shares
Capital structure
Aggregate gross proceeds \| $											$ 29,355,000
Gross proceeds raised \| $							$ 60,000,000
Gain on extinguishment of shares of Series One, Two and Three stock \| $						$ 160,000,000		$ 3,391,000		$ 3,391,000	$ 159,954,000
Aggregate purchase price \| $									$ 235,979,097	$ 131,649,688
Common stock
Common stock, authorized shares					125,000,000				125,000,000	125,000,000
Series One and Series Two \| Warrant
Capital structure
Warrants issued to purchase shares												2,527,675
Exercise price (in dollars per share) \| $ / shares												$ 0.01
Shares issued and sold		2,527,675
Series Four convertible preferred stock
Capital structure
Shares issued and sold		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 convertible preferred stock
Capital structure
Number of shares issued upon conversion		6,700,487
Common stock
Number of shares issued upon conversion		6,700,487
Series Five convertible preferred stock \| Warrant
Capital structure
Number of shares issued upon conversion		2,095,515
Common stock
Number of shares issued upon conversion		2,095,515
Common stock
Capital structure
Shares issued and sold	3,450,000		5,163,265	9,627,800
Reverse stock split ratio		0.0083
Share price (in dollars per share) \| $ / shares				$ 15.00
Public offering price (in dollars per share) \| $ / shares	$ 36.25		$ 24.50
Common stock
Common stock shares issuable pursuant to the exercise by the underwriters of an over-allotment option	450,000		673,469	1,255,800
Net proceeds from public offerings \| $	$ 117,600,000		$ 118,400,000
Net proceeds from initial public offering \| $				$ 131,600,000
Series Four and Series Five Convertible Preferred Stock
Capital structure
Number of shares issued upon conversion				14,170,956
Number of shares issuable upon conversion of each stock				1
Common stock
Number of shares issued upon conversion				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 convertible preferred stock
Capital structure
Shares issued upon conversion of convertible promissory notes		502,919

Capital structure (Details 3) - Common stock - $ / shares	Dec. 31, 2014	Dec. 31, 2013
2014.
Warrants
Warrant shares		1,428
Exercise price (in dollars per share)		$ 128.00
2017
Warrants
Warrant shares	6,250	6,250
Exercise price (in dollars per share)	$ 128.00	$ 128.00
2019 and 2020
Warrants
Warrant shares	7,030	7,030
Exercise price (in dollars per share)	$ 128.00	$ 128.00
2019
Warrants
Warrant shares	130
Exercise price (in dollars per share)	$ 2,520.00
2014
Warrants
Warrant shares		452
Exercise price (in dollars per share)		$ 2,520.00

Earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Jul. 31, 2012	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net income (loss) per share
Common stock equivalents excluded from calculation of diluted earnings per share since the effect would be anti-dilutive											600,000	1,300,000
Numerator
Net loss						$ (17,886)	$ (4,416)	$ (14,587)	$ (14,685)	$ (93,753)	$ (51,574)	$ (26,235)
Deemed dividend									(18,249)		(18,249)
Gain on exchange of convertible preferred stock in connection with recapitalization	$ 160,000								$ 3,391		3,391	159,954
Less beneficial conversion charge												(378)
Less net income attributable to participating preferred stock												(132,610)
Net loss attributable to common stockholders										$ (93,753)	$ (66,432)	$ 731
Denominator
Denominator for basic earnings per share (in shares)										31,565,310	12,829,411	3,328
Effect of dilutive securities:
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Preferred Stock												13,877
Denominator for diluted earnings per share (in shares)										31,565,310	12,829,411	17,205
Net loss per share:
Earnings Per Share, Basic		$ (0.84)	$ (0.93)	$ (0.86)	$ (0.58)	$ (0.75)	$ (0.19)	$ (5.51)	$ (6,527.30)	$ (2.97)	$ (5.18)	$ 219.76
Earnings Per Share, Diluted		$ (0.84)	$ (0.93)	$ (0.86)	$ (0.58)	$ (0.75)	$ (0.19)	$ (5.51)	$ (6,527.30)	$ (2.97)	$ (5.18)	$ 42.50

Stock option plan (Details) - USD ($)		1 Months Ended	12 Months Ended
Stock option plan (Details) - USD ($)	Mar. 05, 2013	May 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Weighted-average remaining contractual term
Outstanding at the end of the period						5 years 8 months 27 days
Stock option
Number of options
Outstanding at the beginning of the period (in shares)			2,095,592	42,394	46,794
Granted (in shares)			1,639,996	2,117,113	5,715
Exercised (in shares)			(108,645)
Forfeited (in shares)			(193,971)	(63,915)	(10,115)
Outstanding at the end of the period (in shares)			3,432,972	2,095,592	42,394	46,794
Vested or expected to vest at the end of the period (in shares)			3,239,515
Exercisable at the end of the period (in shares)			764,277
Exercise price
Granted (in dollars per share)					$ 218.40
Weighted-average exercise price
Outstanding at the beginning of the period (in dollars per share)			$ 20.24	$ 474.00	532.80
Granted (in dollars per share)			31.09	11.29	218.40
Exercised (in dollars per share)			11.00
Forfeited (in dollars per share)			32.91	12.57	604.80
Outstanding at the end of the period (in dollars per share)			25.00	$ 20.24	$ 474.00	$ 532.80
Vested or expected to vest at the end of the period (in dollars per share)			24.15
Exercisable at the end of the period (in dollars per share)			$ 31.84
Weighted-average remaining contractual term
Outstanding at the end of the period			8 years 9 months 7 days	9 years 3 months 15 days	5 years 7 days
Vested or expected to vest at the end of the period			8 years 9 months 11 days
Exercisable at the end of the period			8 years 2 months 27 days
Valuation assumptions
Risk-free interest rate (as a percent)					1.14%
Expected volatility (as a percent)					87.00%
Expected dividend yield (as a percent)			0.00%	0.00%	0.00%
Weighted average grant date fair value (in dollars per share)			$ 22.39	$ 8.23	$ 160.65
Aggregate intrinsic value
Outstanding at the end of the period (in dollars)			$ 106,796
Vested or expected to vest at the end of the period (in dollars)			101,391
Exercisable at the end of the period (in dollars)			$ 29,809
Stock option \| Minimum
Stock option plan
Vesting period			3 years
Exercise price
Outstanding at the beginning of the period (in dollars per share)			$ 10.59	218.40	226.80
Granted (in dollars per share)			18.78	10.59
Exercised (in dollars per share)			10.85
Forfeited (in dollars per share)			10.85	10.85	218.40
Outstanding at the end of the period (in dollars per share)			$ 10.59	$ 10.59	$ 218.40	226.80
Valuation assumptions
Risk-free interest rate (as a percent)			0.11%	0.85%
Expected volatility (as a percent)			70.00%	87.00%
Expected term			5 years 6 months	6 years	6 years
Stock option \| 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
Granted (in dollars per share)			50.45	20.76
Exercised (in dollars per share)			20.71
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	$ 1,149.60
Valuation assumptions
Risk-free interest rate (as a percent)			2.04%	1.90%
Expected volatility (as a percent)			91.00%	89.00%
Expected term			6 years 3 months	6 years 3 months	6 years 3 months
2009 Equity and Long-Term Incentive Plan
Stock option plan
Number of shares available for issuance		0
Number of additional shares authorized		2,500,000
2009 Equity and Long-Term Incentive Plan \| Stock option \| 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 Equity and Long-Term Incentive Plan \| Stock option \| Maximum
Stock option plan
Expiration period			10 years
2013 Stock Incentive Plan
Stock option plan
Number of shares available for issuance	0
2013 Stock Incentive Plan \| Stock option
Stock option plan
Number of shares of restricted stock granted	4,613
2013 Stock Incentive Plan \| Restricted stock
Stock option plan
Number of shares of restricted stock granted	735,324
2013 Stock Incentive Plan \| Common stock
Stock option plan
Number of shares authorized	739,937
2009 Equity and Long Term Incentive Plan and 2013 Stock Incentive Plan \| Common stock
Stock option plan
Number of shares available for issuance		262,044
2013 Long Term Incentive Plan \| Common stock
Stock option plan
Number of shares available for issuance			255,463
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
Inducement grant plan \| Stock option
Number of options
Granted (in shares)			595,300
Forfeited (in shares)			(5,900)
Exercise price
Granted (in dollars per share)			$ 37.15

Stock option plan (Details 2) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Stock options outstanding and exercisable
Outstanding, Number of options (in shares)	3,432,972
Exercisable, Number of options (in shares)	764,277
Additional compensation recognized due to modifications to the options granted	$ 1.9	$ 0.6
$10.59-$10.85
Stock options outstanding and exercisable
Range of Exercise Price, Lower (in dollars per share)	$ 10.59
Range of Exercise Price, Higher (in dollars per share)	$ 10.85
Outstanding, Number of options (in shares)	1,752,630
Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 10.85
Outstanding, Weighted-Average Remaining Contractual Life	8 years 4 months 13 days
Exercisable, Number of options (in shares)	704,958
Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 10.85
$10.85-$20.76
Stock options outstanding and exercisable
Range of Exercise Price, Lower (in dollars per share)	10.85
Range of Exercise Price, Higher (in dollars per share)	$ 20.76
Outstanding, Number of options (in shares)	114,425
Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 19.42
Outstanding, Weighted-Average Remaining Contractual Life	8 years 10 months 24 days
Exercisable, Number of options (in shares)	28,675
Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 19.72
$20.76 - $490.80
Stock options outstanding and exercisable
Range of Exercise Price, Lower (in dollars per share)	20.76
Range of Exercise Price, Higher (in dollars per share)	$ 27.05
Outstanding, Number of options (in shares)	982,796
Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 26.91
Outstanding, Weighted-Average Remaining Contractual Life	9 years 1 month 13 days
Exercisable, Number of options (in shares)	350
Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 27.05
$490.80-735.60
Stock options outstanding and exercisable
Range of Exercise Price, Lower (in dollars per share)	27.05
Range of Exercise Price, Higher (in dollars per share)	$ 50.45
Outstanding, Number of options (in shares)	554,400
Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 39.25
Outstanding, Weighted-Average Remaining Contractual Life	9 years 7 months 13 days
Exercisable, Number of options (in shares)	2,968
Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 40.45
$1,149.60
Stock options outstanding and exercisable
Range of Exercise Price, Lower (in dollars per share)	50.45
Range of Exercise Price, Higher (in dollars per share)	$ 1,149.60
Outstanding, Number of options (in shares)	28,721
Outstanding, Weighted-Average Exercise Price (in dollars per share)	$ 569.97
Outstanding, Weighted-Average Remaining Contractual Life	4 years 3 months 26 days
Exercisable, Number of options (in shares)	27,326
Exercisable, Weighted-Average Exercise Price (in dollars per share)	$ 585.05

Stock option plan (Details 3) - Restricted stock	12 Months Ended
Stock option plan (Details 3) - Restricted stock	Dec. 31, 2014 $ / shares shares
Number of Shares
Balance at the beginning of the period (in shares) \| shares	1,110,226
Vested (in shares) \| shares	(373,200)
Forfeited (in shares) \| shares	(18,626)
Balance at the end of the period (in shares) \| shares	718,400
Weighted Average Grant Date Fair Value
Balance at the beginning of the period (in dollars per share) \| $ / shares	$ 10.68
Vested \| $ / shares	10.59
Forfeited (in dollars per share) \| $ / shares	10.75
Balance at the end of the period (in dollars per share) \| $ / shares	$ 10.72

Stock option plan (Details 4) - USD ($) $ in Thousands	12 Months Ended
Stock option plan (Details 4) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based compensation expense recorded in the statement of operations
Share-based compensation expense	$ 19,310	$ 8,427	$ 2,289
Unrecognized compensation cost	$ 38,400
Weighted average remaining service period for recognition of unrecognized compensation cost	2 years 7 months 28 days
Research and development
Share-based compensation expense recorded in the statement of operations
Share-based compensation expense	$ 9,739	4,312	1,269
Selling, general and administrative
Share-based compensation expense recorded in the statement of operations
Share-based compensation expense	$ 9,571	$ 4,115	$ 1,020

Other comprehensive income (loss) and accumulated other comprehensive items (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Other comprehensive income and accumulated other comprehensive items
Balance at the beginning of the period	$ 70
Other comprehensive income/(losses) before reclassifications	(807)	$ 70
Other comprehensive income/(loss)	(737)	70
Balance at the end of the period	(737)	70
Unrealized Gains/(Losses) On Marketable Securities
Other comprehensive income and accumulated other comprehensive items
Balance at the beginning of the period	70
Other comprehensive income/(losses) before reclassifications	(457)	70
Other comprehensive income/(loss)	(387)	70
Balance at the end of the period	(387)	$ 70
Foreign Currency Gain (Loss) [Member]
Other comprehensive income and accumulated other comprehensive items
Other comprehensive income/(losses) before reclassifications	(350)
Other comprehensive income/(loss)	(350)
Balance at the end of the period	$ (350)

- 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

Collaborations and grants (Details) $ in Millions		1 Months Ended			12 Months Ended
Collaborations and grants (Details) $ in Millions	Jan. 02, 2011 item	Nov. 30, 2014 USD ($)	Jan. 31, 2014 USD ($)	Nov. 30, 2011 USD ($) item	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Minimum
Grant revenue
Term of grant program					2 years
Maximum
Grant revenue
Term of grant program					5 years
Collaboration agreement \| Development event milestones
Collaborations and grants
Collaboration revenue recognized		$ 10.0	$ 7.5
Collaboration agreement \| Roche and SMA Foundation
Collaborations and grants
Deferred revenue				$ 30.0
Collaboration revenue recognized					$ 20.2	$ 26.6	$ 18.4
Number of compounds in preclinical development \| item				3
Number of significant deliverables \| item				2
Research period for applying technology				2 years
Collaboration agreement \| Roche and SMA Foundation \| Development event milestones \| Maximum
Collaborations and grants
Additional consideration receivable upon achievement of specified events					135.0
Collaboration agreement \| Roche and SMA Foundation \| Sales milestones \| Maximum
Collaborations and grants
Additional consideration receivable upon achievement of specified events					325.0
Early stage collaboration and discovery agreements
Collaborations and grants
Deferred revenue					1.8	0.9
Collaboration revenue recognized					$ 1.3	$ 4.8
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 \| Development event milestones
Collaborations and grants
Additional consideration receivable upon achievement of specified events					$ 143.0
Early stage collaboration and discovery agreements \| Sales milestones \| Maximum
Collaborations and grants
Additional consideration receivable upon achievement of specified events					$ 252.0

Income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
Income taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current:
U.S. State and local	$ (4,890)	$ 2
Foreign	197
Current Income Tax Expense (Benefit), Total	$ (4,693)	$ 2
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%	34.00%
State income tax benefit, net of federal benefit (as a percent)	(1.60%)	5.65%	3.80%
Permanent differences (as a percent)	(0.93%)	(5.90%)
NOL IRC Section 382 Limitations	(21.53%)
Research and development (as a percent)	3.78%	15.88%
Increase to valuation allowance (as a percent)	9.17%	(49.63%)	(35.80%)
Foreign Taxes	(18.14%)
Other (as a percent)	0.01%		(2.00%)
Effective income tax rate (as a percent)	4.76%	0.00%	0.00%
Deferred tax assets:
Amortization	$ 69	$ 80
Depreciation	2,268	1,922
Accrued expense	611	333
Deferred revenue	699	350
Federal tax credits	17,807	14,082
State tax credits	1,274	1,587
Federal net operating losses	76,933	88,188
State net operating losses	9,185	10,457
Capitalized research and development costs	10,585	12,254
Other	3,852	3,212
Total gross deferred tax assets	123,283	132,465
Less valuation allowance	$ 123,283	$ 132,465

Income taxes (Details 2) - USD ($) $ in Millions	12 Months Ended
Income taxes (Details 2) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013
Income taxes
Change in valuation allowance	$ 9.2	$ 25.6
Federal
Operating loss carryforwards
Net operating loss carryforwards	226.3
State
Operating loss carryforwards
Net operating loss carryforwards	$ 154.6

Income taxes (Details 3) $ in Millions	12 Months Ended
Income taxes (Details 3) $ in Millions	Dec. 31, 2014 USD ($)
Credit carryforwards
Orphan drug credit carryover	$ 11.4
Limited NOL carryforwards	231.5
Operating loss carryforwards, not subject to expiration	$ 169.2
NOL carryforward period	20 years
Operating loss carryforwards, subject to expiration	$ 62.3
Operating loss carryforwards for immediate use	82.1
Operating loss carryforwards in next twelve months	16.7
Federal
Credit carryforwards
Credit carryforwards	6.5
Net operating loss carryforwards	226.3
State
Credit carryforwards
Credit carryforwards	1.7
Net operating loss carryforwards	154.6
First five years from ownership change
Credit carryforwards
Net operating loss carryforwards	16.7
After five years
Credit carryforwards
Net operating loss carryforwards	$ 5.7

Income taxes (Details 4) - USD ($) $ in Thousands	12 Months Ended
Income taxes (Details 4) - USD ($) $ in Thousands	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating loss carryforwards
Net tax benefit	$ 4,693
Uncertain tax position	$ 0	$ 0
U.S. federal income tax rate (as a percent)	34.00%	34.00%	34.00%
New Jersey
Operating loss carryforwards
Net tax benefit	$ 4,900
State \| New Jersey
Operating loss carryforwards
Net operating loss carryforwards sold under the Technology Business Tax Certificate Transfer Program	$ 50,400

Commitments and contingencies (Details) $ in Millions	Dec. 31, 2014 USD ($)
Funding agreement \| Wellcome Trust \| Maximum
Other contingencies
Development and regulatory milestone payments which the entity may be obligated to pay	$ 68.9

Geographic segments (Details) $ in Thousands	12 Months Ended
Geographic segments (Details) $ in Thousands	Dec. 31, 2014 USD ($) item	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Revenues from External Customers and Long-Lived Assets [Line Items]
Number of Operating Segments \| item	1
Total assets	$ 333,219	$ 151,903
Property and equipment, net	9,159	6,730
Revenue, Net	25,245	34,696	$ 33,946
Operating Segments
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	333,219	151,903
Property and equipment, net	9,159	6,730
Revenue, Net	25,245	34,696
US
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	330,663	151,903
Property and equipment, net	8,555	6,730
Revenue, Net	25,245	$ 34,696
Non US
Revenues from External Customers and Long-Lived Assets [Line Items]
Total assets	2,556
Property and equipment, net	$ 604

401(k) plan (Details) - USD ($) $ in Millions	12 Months Ended
401(k) plan (Details) - USD ($) $ in Millions	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
401(k) plan
Matching contribution up to the first 6% of employee's base salary (as a percent)	33.00%
Percentage of employee's base salary, matched by employer	6.00%
Expense recorded	$ 0.3	$ 0.1	$ 0.2

Selected quarterly financial data (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Jul. 31, 2012	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Selected quarterly financial data
Net Product Sales		$ 636	$ 81							$ 717
Collaboration and grant revenue		12,022	1,613	$ 1,677	$ 9,217	$ 4,411	$ 16,290	$ 6,854	$ 7,142
Operating Expenses		44,888	29,295	27,046	23,429	22,503	20,565	21,307	15,718	124,658	$ 80,094	$ 60,754
Loss from operations		(32,230)	(27,601)	(25,369)	(14,212)	(18,093)	(4,276)	(14,453)	(8,576)	(99,413)	(45,398)	(26,808)
Net loss						(17,886)	(4,416)	(14,587)	(14,685)	(93,753)	(51,574)	(26,235)
Deemed Dividend									18,249		18,249
Gain on exchange of convertible preferred stock in connection with recapitalization	$ 160,000								3,391		3,391	159,954
Less beneficial conversion charge												(378)
Net income (loss) attributable to common stockholders		$ (27,269)	$ (27,282)	$ (25,104)	$ (14,098)	$ (17,886)	$ (4,416)	$ (14,587)	$ (29,543)	$ (93,753)	$ (66,432)	$ 133,341
Basic net income (loss) per common share		$ (0.84)	$ (0.93)	$ (0.86)	$ (0.58)	$ (0.75)	$ (0.19)	$ (5.51)	$ (6,527.30)	$ (2.97)	$ (5.18)	$ 219.76
Diluted net income (loss) per common share		$ (0.84)	$ (0.93)	$ (0.86)	$ (0.58)	$ (0.75)	$ (0.19)	$ (5.51)	$ (6,527.30)	$ (2.97)	$ (5.18)	$ 42.50

Label	Element	Value
Operating Leases, Future Minimum Payments, Due in Three Years	us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears	$ 923,000
Operating Leases, Future Minimum Payments, Due in Two Years	us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears	932,000
Operating Leases, Rent Expense, Net	us-gaap_OperatingLeasesRentExpenseNet	700,000
Operating Leases, Rent Expense, Net	us-gaap_OperatingLeasesRentExpenseNet	900,000
Operating Leases, Future Minimum Payments Due, Next Twelve Months	us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent	1,268,000
Operating Leases, Future Minimum Payments Due	us-gaap_OperatingLeasesFutureMinimumPaymentsDue	4,334,000
Operating Leases, Future Minimum Payments, Due in Four Years	us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears	1,035,000
Operating Leases, Future Minimum Payments, Due in Five Years	us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears	$ 176,000