Additional Proxy Soliciting Materials (Form DEFA14A)

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:

Cogent 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):

Your Vote Counts! COGENT BIOSCIENCES, INC. 2026 Annual Meeting Vote by June 8, 2026 11:59 PM ET COGENT BIOSCIENCES, INC. 275 WYMAN ST., 3RD FLOOR WALTHAM, MA 02451 V87717-P47250 You invested in COGENT BIOSCIENCES, INC. and it's time to vote! You have the right to vote on proposals being presented at the Annual Meeting. This is an important notice regarding the availability of proxy materials for the stockholder meeting to be held on June 9, 2026. Get informed before you vote View the Proxy Statement, Notice and Annual Report for the year ended December 31, 2025 online OR you can receive a free paper or email copy of the material(s) by requesting prior to May 26, 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 [email protected]. 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 Point your camera here and vote without entering a control number Vote Virtually at the Meeting* June 9, 2026 9:00 AM ET Virtually at: www.virtualshareholdermeeting.com/COGT2026 *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 more complete proxy materials that are available to you on the Internet. You may view the proxy materials at www.proxyvote.com or easily request a paper copy. 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 on these important matters. Board Recommends Voting Items 1. Election of the three Class II director nominees to serve until the 2029 Annual Meeting of Stockholders and until their successors are duly elected and qualified. For Nominees: 01) Dr. Chris Cain 02) Arlene M. Morris 03) Todd Shegog 2. Ratification of the selection of PricewaterhouseCoopers LLP as the Company's independent registered public accounting firm for the year ending December 31, 2026. For 3. Approval, on a non-binding, advisory basis, of the compensation of the Company's named executive officers. For NOTE: Such other business as may properly come before the meeting or any adjournment or postponement thereof.