C4 Therapeutics, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A INFORMATION

PROXY STATEMENT PURSUANT TO SECTION 14(a)

OF THE SECURITIES EXCHANGE ACT OF 1934

Filed by the Registrantx Filed by a Party other than the Registranto

Check the appropriate box:

(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 boxes that apply):

Watertown, Massachusetts 02472

NOTICE OF 2025 ANNUAL MEETING OF STOCKHOLDERS

To be held June 18, 2025

Notice is hereby given that the 2025 Annual Meeting of Stockholders, or Annual Meeting, of C4 Therapeutics, Inc., will be held online on Thursday, June 18, 2025, at 8:30 a.m. Eastern Time. You will be able to attend, vote and submit your questions atwww.virtualshareholdermeeting.com/CCCC2025. You will need the 16-digit control number included with these proxy materials to attend the Annual Meeting. The purpose of the Annual Meeting is the following:

1. To elect three Class II directors to our Board of Directors, each to serve until the 2028 annual meeting of stockholders and until his or her successor has been duly elected and qualified, or until his or her earlier resignation or removal;

2. To cast a non-binding, advisory vote to approve the compensation of our named executive officers;

3. To ratify the appointment of KPMG LLP as our independent registered public accounting firm for the fiscal year ending December 31, 2025;

4. To approve an amendment to our Fifth Amended and Restated Certificate of Incorporation to increase the number of authorized shares of common stock from 150,000,000 to 300,000,000; and

5. To transact any other business properly brought before the Annual Meeting or any adjournment or postponement of the Annual Meeting.

The proposal for the election of directors relates solely to the election of Class II directors nominated by the Board of Directors. Only C4 Therapeutics, Inc., stockholders of record at the close of business on April 22, 2025 will be entitled to vote at the Annual Meeting and any adjournment or postponement thereof.

We are pleased to take advantage of Securities and Exchange Commission rules that allow companies to furnish their proxy materials over the Internet. We believe that this e-proxy process will not only expedite stockholders’ receipt of proxy materials, but also lower the costs of printing and distributing our proxy materials, as well as reduce the environmental impact of our Annual Meeting. We will mail the Notice of Availability of Proxy Materials, or Notice, instead of a paper copy of our proxy materials and our 2024 Annual Report to Stockholders, or 2024 Annual Report, on or about April 29, 2025. The Notice contains instructions on how to access those documents and to cast your vote via the Internet. The Notice also contains instructions on how to request a paper copy of our proxy materials and our 2024 Annual Report.

Your vote is important. Whether or not you are able to attend the meeting in person, it is important that your shares be represented. To ensure that your vote is recorded promptly, please vote as soon as possible, even if you plan to attend the meeting, by submitting your proxy via the Internet at the address listed on the proxy card or by signing, dating and returning the proxy card.

By order of the Board of Directors,

Andrew J. Hirsch

President and Chief Executive Officer

Watertown, Massachusetts

April 29, 2025