Item 7.01. Regulation FD Disclosure. On July 28, 2025, PTC Therapeutics, Inc. (the “ Company”), announced that the U. S. Food and Drug Administration (“ FDA”) approved Sephience™ (sepiapterin) for the treatment of children and adults living with phenylketonuria (“ PKU”). Sephience is indicated for the treatment of hyperphenylalaninemia in adult and pediatric patients one month of age and older with sepiapterin-responsive PKU. T he full text of the press release issued in connection with the announcement is furnished as Exhibit 99.1 to this Current Report on Form 8-K (this “ Report”) and is incorporated by reference into this Item 7.01. The Company will host aconference call on July 28, 2025 at 5:00 p. m. Eastern Time to discuss the approval. Instructions on how to access the conference call are included in the press release furnished as Exhibit 99.1 hereto.

Item 9.01. Financial Statements and Exhibits. (d) Exhibits Exhibit No. Description 99.1 Press Release, dated July 28, 2025 issued by PTC Therapeutics, Inc. ────────────────────────────────────────────────────────────────────────────────────────────────── 104 The cover page from this Current Report on Form 8-K, formatted in Inline XBRL SIGNATURE Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this Report to be signed on its behalf by the undersigned hereunto duly authorized. PTC Therapeutics, Inc. Date: July 28, 2025 By: /s/ Pierre Gravier Name: Pierre Gravier Title: Chief Financial Officer