UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 13D/A

Under the Securities Exchange Act of 1934

(Amendment No. 1)*

C4 THERAPEUTICS, INC.

(Name of Issuer)

COMMON STOCK, $0.0001 PAR VALUE PER SHARE

(Title of Class of Securities)

12529R107

(CUSIP Number)

Cobro Ventures Opportunity Fund, L.P.

Attention: Marc Cohen

1000 Wilson Blvd.

#1800

Arlington, VA 22209

(202) 421-7994

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

June 14, 2021

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d 1(e), 240.13d 1(f) or 240.13d 1(g), check the following box.  ☐

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

EXPLANATION.

This Amendment No. 1 (this “Amendment”) amends and supplements the Schedule 13D (the “Schedule 13D”) filed with the Securities and Exchange Commission by the Reporting Persons on October 16, 2020 with respect to the common stock, par value $0.0001 per share (the “Common Stock”), of C4 Therapeutics, Inc., a Delaware corporation (the “Company”). Except as specifically provided herein, this Amendment does not modify any of the information previously reported in the Schedule 13D.

Paragraphs (a), (b) and (c) of this Item 5 are amended and restated as follows:

(a) and (b) As of June 14, 2021, Cobro Ventures directly owned no shares of Common Stock of the Company and Cobro GP beneficially owned no shares of Common Stock of the Company.

As of June 14, 2021, M. Cohen’s beneficial ownership consisted of (i) 1,874,805 shares of Common Stock held by M. Cohen, as trustee of the Marc Andrew Cohen Revocable Trust, (ii) 98,936 shares of Common Stock held by M. Cohen, and (iii) stock options exercisable for 154,258 shares of Common Stock within 60 days of June 14, 2021 held by M. Cohen, representing approximately 4.9% of the 43,195,352 shares of Common Stock outstanding as of May 3, 2021, as set forth in the Company’s quarterly report on Form 10-Q, for the period ended March 31, 2021, and filed with the Commission on May 13, 2021.

As of June 14, 2021, A. Cohen’s beneficial ownership consisted of (i) 1,741,930 shares of Common Stock held by A. Cohen, as trustee of the Alain J. Cohen Revocable Trust, (ii) 62,143 shares of Common Stock held by A. Cohen, and (iii) stock options exercisable for 23,672 shares of Common Stock within 60 days of June 14, 2021 held by A. Cohen, representing approximately 4.2% of the 43,195,352 shares of Common Stock outstanding as of May 3, 2021, as set forth in the Company’s quarterly report on Form 10-Q, for the period ended March 31, 2021, and filed with the Commission on May 13, 2021.

As of June 14, 2021, T. Kaloudis’ beneficial ownership consisted of 38,090 shares of Common Stock, representing approximately less than 0.1% of the 43,195,352 shares of Common Stock outstanding as of May 3, 2021, as set forth in the Company’s quarterly report on Form 10-Q, for the period ended March 31, 2021, and filed with the Commission on May 13, 2021.

(c) On June 14, 2021 Cobro Ventures distributed to its limited partners and sole general partner, Cobro GP, pro rata and without consideration, 2,484,425 shares of the Company’s Common Stock. Of these shares, 22,598 shares were distributed to M. Cohen as trustee of Marc Andrew Cohen Revocable Trust, 22,598 shares were distributed to A. Cohen as trustee of Alain J. Cohen Revocable Trust, 4,520 shares were distributed to T. Kaloudis, and 185,633 shares were distributed to Cobro GP.

In turn, Cobro GP, distributed to its members, pro rata and without consideration, the 185,633 shares it received from Cobro Ventures. Of these shares, on the same date Cobro GP distributed, pro rata and without consideration, 92,817 shares to M. Cohen, 61,877 shares to A. Cohen and 30,939 shares to T. Kaloudis.

As a result of the foregoing distributions, each of Cobro Ventures, Cobro GP, M. Cohen, A. Cohen and T. Kaloudis currently beneficially owns less than five percent of the Company’s outstanding shares of Common Stock and is no longer required to continue such Schedule 13D filings.

SIGNATURES

After reasonable inquiry and to the best of its knowledge and belief, the undersigned certifies that the information set forth in this Statement is true, complete and correct.

Dated: June 15, 2021

EXHIBIT INDEX

Exhibit 1

Joint Filing Agreement

In accordance with Rule 13d-1(k) under the Securities and Exchange Act of 1934, the persons or entities named below agree to the joint filing on behalf of each of them of a statement on Schedule 13D (including amendments thereto) with respect to the shares of common stock of the Company and further agree that this joint filing agreement be included as an exhibit to this Schedule 13D. In evidence thereof, the undersigned, being duly authorized, have executed this Joint Filing Agreement as of June 15, 2021.