CGEM Cullinan Therapeutics Inc

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

(Rule 14a-101)

Information Required in Proxy Statement

Schedule 14A Information

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Securities Exchange Act of 1934

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CULLINAN ONCOLOGY, INC.

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Your Vote Counts!    CULLINAN ONCOLOGY, INC. 2023 Annual Meeting Vote by June 7, 2023 11:59 PM ET CULLINAN ONCOLOGY, INC. ONE MAIN STREET SUITE 1350 CAMBRIDGE, MA 02142 V11695-P92927    You invested in CULLINAN ONCOLOGY, 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 8, 2023 at 10:00 a.m., Eastern Time. Get informed before you vote View the Notice and Proxy Statement online OR you can receive a free paper or email copy of the material(s) by requesting prior to May 25, 2023. 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 Virtually at the Meeting* Point your camera here and June 8, 2023 vote without entering a 10:00 a.m., Eastern Time control number    Virtually at: www.virtualshareholdermeeting.com/CGEM2023 *Please check the meeting materials for any special requirements for meeting attendance. V1.1

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. Please follow the instructions on the reverse side to vote these important matters.    Board Voting Items Recommends 1. Election of the following individuals nominated to serve as Class III directors, for a three-year term ending at the    annual meeting of stockholders to be held in 2026:    Nominees:    01) Nadim Ahmed For 02) Stephen Webster 2. Proposal to ratify the appointment of KPMG LLP as Cullinan Oncology’s independent registered public accounting firm For for the fiscal year ending December 31, 2023. Note: The Board of Directors will consider and act upon any other business as may properly come before the annual 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”. V11696-P92927