SEC Form DEFA14A filed by PTC Therapeutics Inc.

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Filed by a Party other than the Registrant ☐

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Preliminary Proxy Statement

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Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

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Definitive Proxy Statement

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Definitive Additional Materials

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Soliciting Material under §240.14a-12

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PTC Therapeutics, Inc.

(Name of Registrant as Specified In Its Charter)

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(Name of Person(s) Filing Proxy Statement, if other than the Registrant)

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☐  Fee paid previously with preliminary materials.

☐  Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-111.

Your Vote Counts! Smartphone users Point your camera here and vote without entering a control number For complete information and to vote, visit www.ProxyVote.com Control # V93918-P50471 PTC THERAPEUTICS, INC. 500 WARREN CORPORATE CENTER DRIVE WARREN, NJ 07059 PTC THERAPEUTICS, INC. 2026 Annual Meeting June 2, 2026 9:00 AM ET Virtual Meeting Site: www.virtualshareholdermeeting.com/PTCT2026 Important Notice Regarding the Availability of Proxy Materials for the Stockholder Meeting to Be Held on June 2, 2026 You invested in PTC THERAPEUTICS, INC. and it’s time to vote! You have the right to vote on proposals being presented at the 2026 Annual Meeting. Vote Virtually at the 2026 Annual Meeting* Vote on June 2, 2026 9:00 a.m., Eastern Time Visit www.virtualshareholdermeeting.com/PTCT2026 *Please check the proxy and www.virtualshareholdermeeting.com/PTCT2026 for any special requirements for meeting attendance. Get informed before you vote View the Notice and Proxy Statement and 2025 Annual Report online OR you can receive a free paper or email copy of the material(s) by requesting prior to May 19, 2026. If you would like to request a copy of the material(s) for this and/or future stockholder meetings, you may (1) visit www.ProxyVote.com, (2) call 1-800-579-1639 or (3) send an email to sendmaterial@proxyvote.com. If sending an email, please include your control number (indicated below) in the subject line. Unless requested, you will not otherwise receive a paper or email copy. Vote in Advance of the 2026 Annual Meeting Vote by June 1, 2026 11:59 PM ET. For shares held in a Plan, vote by May 30, 2026 11:59 PM ET. Visit www.ProxyVote.com

Vote at www.ProxyVote.com Prefer to receive an email instead? While voting on www.ProxyVote.com, be sure to click “Delivery Settings”. Voting Items Board Recommends V93919-P50471 THIS IS NOT A VOTABLE BALLOT This is an overview of the more complete proxy materials that are available to you on the Internet. We encourage you to access and review all of the important information contained in the proxy materials before voting. Please follow the instructions on the reverse side to vote these important matters. 1. Election of Four Class I Directors For Nominees: 01) Jessica Chutter 02) Matthew B. Klein, M.D., M.S., F.A.C.S. 03) Stephanie S. Okey, M.S. 04) Jerome B. Zeldis, M.D., Ph.D. 2. Ratification of the appointment of Ernst & Young LLP as the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2026. For 3. Approval on a non-binding, advisory basis, of the Company’s named executive officer compensation as described in the proxy statement. For NOTE: To transact any other business that may be properly brought before the meeting or any adjournment or postponement of the meeting.