X0202 SCHEDULE 13G 0002115022 XXXXXXXX LIVE Common Stock, par value $0.0001 per share 03/31/2026 0001662579 C4 Therapeutics, Inc. 12529R107 490 Arsenal Way Suite 120 Watertown MA 02472 Rule 13d-1(b) Sirenia Capital Management LP b DE 0.00 23505000.00 0.00 23505000.00 23505000.00 N 9.9 IA PN Includes 14,170,000 shares of Common Stock (as defined in Item 2(a)) issuable upon exercise of the Reported Warrants (as defined in Item 4(a)). As more fully described in Item 4, the Reported Warrants are subject to the 9.99% Blocker (as defined in Item 4(a)) and the percentage set forth on row (11) gives effect to the 9.99% Blocker. However, rows (6), (8) and (9) show the number of shares of Common Stock that would be issuable upon the full exercise of the Reported Warrants and does not give effect to the 9.99% Blocker. Therefore, the actual number of shares of Common Stock beneficially owned by such Reporting Person, after giving effect to the 9.99% Blocker, is less than the number of securities reported on rows (6), (8) and (9). Alex Silverstein b X1 0.00 23505000.00 0.00 23505000.00 23505000.00 N 9.9 HC IN Includes 14,170,000 shares of Common Stock issuable upon exercise of the Reported Warrants. As more fully described in Item 4, the Reported Warrants are subject to the 9.99% Blocker and the percentage set forth on row (11) gives effect to the 9.99% Blocker. However, rows (6), (8) and (9) show the number of shares of Common Stock that would be issuable upon the full exercise of the Reported Warrants and does not give effect to the 9.99% Blocker. Therefore, the actual number of shares of Common Stock beneficially owned by such Reporting Person, after giving effect to the 9.99% Blocker, is less than the number of securities reported on rows (6), (8) and (9). C4 Therapeutics, Inc. 490 Arsenal Way, Suite 120, Watertown, MA 02472 This statement is filed by: (i) Sirenia Capital Management LP ("Sirenia") with respect to the common stock, par value $0.0001 per share ("Common Stock"), of C4 Therapeutics, Inc. (the "Issuer") held by, and issuable upon exercise of the Reported Warrants held by, SILV Fund, Ltd. (the "Sirenia Fund"), an investment fund it manages; and (ii) Alex Silverstein ("Mr. Silverstein"), the managing member of Sirenia Capital Management GP LLC, the general partner of Sirenia, with respect to the Common Stock held by, and issuable upon exercise of Reported Warrants held by, the Sirenia Fund. The foregoing persons are hereinafter sometimes collectively referred to as the "Reporting Persons." The filing of this statement should not be construed as an admission that any of the foregoing persons or any Reporting Person is, for the purposes of Section 13 of the Securities Exchange Act of 1934, the beneficial owner of the securities reported herein. Sirenia and Mr. Silverstein have entered into a Joint Filing Agreement, a copy of which is filed with this Schedule 13G as Exhibit 99.1, pursuant to which they have agreed to file this Schedule 13G jointly in accordance with the provisions of Rule 13d-1(k) of the Securities Exchange Act of 1934 (the "Act"). The address of the principal business office of Sirenia and Mr. Silverstein is 1674 Meridian Avenue, Suite 320, Miami Beach, FL 33139. Sirenia is a Delaware limited partnership. Mr. Silverstein is a United States citizen. N IA HC The information required by Item 4(a) is set forth in Row 9 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The percentage set forth in this Schedule 13G is calculated based upon an aggregate of 97,578,175 shares of Common Stock outstanding as of February 23, 2026, as reported in the Issuer's Annual Report on Form 10-K for the fiscal year ended December 31, 2025, filed with the Securities and Exchange Commission on February 26, 2026, and assumes the exercise of the warrants (the "Reported Warrants") held by the Sirenia Fund. Pursuant to the terms of the Reported Warrants, the Reporting Persons cannot exercise any of the Reported Warrants to the extent the Reporting Persons would beneficially own, after any such exercise, more than 9.99% of the outstanding shares of Common Stock (the "9.99% Blocker") and the percentage set forth in Row (11) of the cover page for each of the Reporting Persons gives effect to the 9.99% Blocker. Consequently, at this time, the Reporting Persons are not able to exercise all of such Reported Warrants due to the 9.99% Blocker. 9.9% The information required by Item 4(c)(i) is set forth in Row 5 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The information required by Item 4(c)(ii) is set forth in Row 6 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The information required by Item 4(c)(iii) is set forth in Row 7 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The information required by Item 4(c)(iv) is set forth in Row 8 of the cover page for each of the Reporting Persons and is incorporated herein by reference. Y N See Item 2(a). The Sirenia Fund has the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, more than 5 percent of the outstanding Common Stock. Y Y Y N By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11. Exhibit 99.1: Joint Filing Agreement Sirenia Capital Management LP /s/ Kolby Loft 05/15/2026 Alex Silverstein /s/ Alex Silverstein 05/15/2026