UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K/A

(Amendment No. 1)

For the fiscal year ended: December 31, 2022

or

Commission file number: 001-35969

PTC THERAPEUTICS, INC.

(Exact name of registrant as specified in its charter)

(908) 222-7000

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes x    No ¨

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes ¨    No x

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes x    No ¨

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes x    No ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. x

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ¨    No x

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. ¨

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to § 240.10D-1(b). ¨

The aggregate market value of the Common Stock held by non-affiliates of the registrant, based upon the last sale price of the Common Stock reported on the Nasdaq Global Select Market on June 30, 2022, the last business day of the registrant’s most recently completed second fiscal quarter, was $2,129,532,394. For purposes of this calculation, shares of Common Stock held by directors and officers have been treated as shares held by affiliates.

As of February 16, 2023, the registrant had 73,815,144 shares of Common Stock, $0.001 par value per share, outstanding.

EXPLANATORY NOTE

This Amendment No. 1 on Form 10-K/A (“Amendment No. 1”) to the Annual Report on Form 10-K of PTC Therapeutics, Inc. (the “Company”) for the year ended December 31, 2022, originally filed with the Securities and Exchange Commission (the “SEC”) on February 21, 2023 (the “Original Filing”), is being filed solely for the purpose of amending Item 15, Exhibits and Financial Statement Schedules, of Part IV, to add reference to new Exhibits 10.57, 10.58 and 10.59. References in the exhibit index to these exhibits, which are incorporated by reference to prior filings by the Company with the SEC, were inadvertently omitted from the Original Filing due to an administrative error.

In addition, as required by Rule 12b-15 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), new certifications by our principal executive officer and principal financial officer pursuant to Rules 13a-14(a) and 15d-14(a) of the Exchange Act are filed as exhibits to this Amendment No. 1.

This Amendment No. 1 does not update or amend the Company’s financial statements or any other items in the Original Filing in any way other than as described in the preceding paragraphs, and the Original Filing, as amended by this Amendment No. 1, continues to speak as of the date of the Original Filing. Accordingly, this Amendment No. 1 should be read in conjunction with the Original Filing and the Company’s other filings with the SEC.

PART IV

Item 15.   Exhibits and Financial Statement Schedules

Financial Statements

The response to this portion of Item 15 is incorporated by reference from the Original Filing into this Amendment.

Exhibits

Those exhibits required to be filed with the Annual Report on Form 10-K by Item 601 of Regulation S-K are listed in the exhibit index below.

Exhibit Index

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.