SLDB Solid Biosciences Inc

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No. )

Filed by the Registrant ☒

Filed by a Party other than the Registrant ☐

Check the appropriate box:

SOLID BIOSCIENCES INC.

(Name of Registrant as Specified in its Charter)

(Name of Person(s) Filing Proxy Statement, if Other Than the Registrant)

Payment of Filing Fee (Check all boxes that apply):

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE STOCKHOLDER MEETING TO BE HELD ON JUNE 12, 2025 Your Vote Counts! SOLID BIOSCIENCES INC. 2025 Annual Meeting June 12, 2025 8:00 AM ET Virtual Meeting Site: www.virtualshareholdermeeting.com/SLDB2025 SOLID BIOSCIENCES INC. C/O PROXY SERVICES P.O. BOX 9142 FARMINGDALE, NY 11735 V72911-P31568 You invested in SOLID BIOSCIENCES INC. and it’s time to vote! You have the right to vote on proposals being presented at the Annual Meeting. Get informed before you vote View the Notice, Proxy Statement and Annual Report online OR you can receive a free paper or email copy of the material(s) by requesting prior to May 29, 2025. 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. For complete information and to vote, visit www.ProxyVote.com Control # Smartphone users Vote in Advance of the Meeting Vote by June 11, 2025 11:59 PM ET Point your camera here and Visit www.ProxyVote.com vote without entering a Vote Virtually at the Meeting* control number June 12, 2025 8:00 AM ET Visit: www.virtualshareholdermeeting.com/SLDB2025 *Please check the meeting materials for any special requirements for meeting attendance.

Vote at www.ProxyVote.com THIS IS NOT A VOTABLE BALLOT This is an overview of the proposals being presented at the upcoming stockholder meeting. 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. Board Voting Items Recommends 1. Election of Class I Directors Nominees: 1a. Alexander Cumbo For 1b. Sukumar Nagendran For 2. The ratification of the appointment of PricewaterhouseCoopers LLP as the Company’s independent registered public For accounting firm for the fiscal year ending December 31, 2025. 3. The approval of an amendment to the Company’s Certificate of Incorporation, as amended, to increase the number For of authorized shares of the Company’s common stock from 120,000,000 to 240,000,000. 4. The approval of an amendment to the Company’s Amended and Restated 2020 Equity Incentive Plan to increase the number of shares of our common stock available for issuance thereunder by 9,000,000 shares and amend the For evergreen provision. 5. The approval of an advisory vote on executive compensation. For NOTE: The proxies are authorized to vote, in their discretion, upon such other business as may properly come before the meeting or any adjournment or postponement thereof. Prefer to receive an email instead? While voting on www.ProxyVote.com, be sure to click “Delivery Settings”. V72912-P31568