RA Capital reports 9.99% stake in C4 Therapeutics

Rhea-AI Filing Summary

RA Capital Management and affiliated reporting persons report their beneficial ownership in C4 Therapeutics, Inc. common stock in an amended Schedule 13G. As of June 30, 2026, they beneficially owned 11,383,696 shares of common stock, representing 9.99% of the class, with shared voting and dispositive power and no sole power.

The RA Capital Healthcare Fund directly holds 8,000,000 common shares and multiple series of warrants exercisable for additional shares. These include pre-funded, Class A, and Class B warrants, all subject to Beneficial Ownership Blockers that prevent exercises that would raise beneficial ownership above 9.99% of the outstanding common stock.

Key Figures

Beneficial ownership shares: 11,383,696 shares Beneficial ownership percentage: 9.99% Shares outstanding baseline: 110,567,222 shares +5 more

8 metrics

Beneficial ownership shares 11,383,696 shares Shares of C4 Therapeutics common stock beneficially owned as of June 30, 2026

Beneficial ownership percentage 9.99% Percentage of C4 Therapeutics common stock class beneficially owned as of June 30, 2026

Shares outstanding baseline 110,567,222 shares C4 Therapeutics common stock outstanding as of May 1, 2026, used for ownership calculation

Shares issuable upon warrant exercise 3,383,696 shares Common shares included in ownership from exercisable warrants, subject to Beneficial Ownership Blockers

Fund common shares held 8,000,000 shares C4 Therapeutics common stock directly held by RA Capital Healthcare Fund, L.P.

Pre-funded warrants 8,195,000 shares Shares of C4 Therapeutics common stock exercisable under pre-funded warrants held by the Fund

Class A warrants 16,195,000 shares Shares of C4 Therapeutics common stock exercisable under Class A Warrants held by the Fund

Class B warrants 16,195,000 shares Shares of C4 Therapeutics common stock exercisable under Class B Warrants held by the Fund

Key Terms

Beneficial Ownership Blockers, pre-funded warrants, Class A Warrants, Class B Warrants, +2 more

6 terms

Beneficial Ownership Blockers regulatory

"Each of the Pre-Funded Warrants, the Class A Warrants and the Class B Warrants contains a provision (the "Beneficial Ownership Blockers")"

pre-funded warrants financial

"pre-funded warrants (the "Pre-Funded Warrants") exercisable for up to 8,195,000 shares of common stock"

Pre-funded warrants are financial instruments that give investors the right to purchase a company's stock at a set price, but with most or all of the purchase price paid upfront. They function like a coupon or gift card for stock, allowing investors to buy shares later at a fixed price, which can be beneficial if they want to avoid future price increases. This makes them important for investors seeking flexibility and certainty in their investment plans.

Class A Warrants financial

"Class A warrants (the "Class A Warrants") exercisable for up to 16,195,000 shares of common stock"

Class B Warrants financial

"Class B warrants (the "Class B Warrants" and, together with the Pre-Funded Warrants and Class A Warrants, the "Warrants")"

Class B warrants are tradable contracts that give the holder the right to buy a company's Class B shares at a fixed price before a set date. Think of them as a coupon for a specific model of a product: if the market price of those Class B shares rises above the coupon price, the warrant lets an investor buy shares more cheaply, offering leveraged upside but also the potential to dilute existing owners when converted.

Section 13(d) of the Act regulatory

"may be deemed a beneficial owner, for purposes of Section 13(d) of the Act"

beneficial owner regulatory

"may be deemed a beneficial owner, for purposes of Section 13(d) of the Act, of any securities"

A beneficial owner is the person who ultimately owns or controls a financial asset or property, even if their name isn't directly on official documents. Think of it like someone who secretly holds the keys to a safe deposit box—others may appear to have access, but the true owner is the one who benefits from what's inside. Identifying beneficial owners helps ensure transparency and prevent illegal activities like money laundering or fraud.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What stake in CCCC does RA Capital report owning in this Schedule 13G/A?

RA Capital and affiliated reporting persons report beneficial ownership of 11,383,696 shares of C4 Therapeutics common stock, representing 9.99% of the class as of June 30, 2026, with shared voting and dispositive power over these shares.

How is RA Capital’s 9.99% beneficial ownership in CCCC calculated?

The 9.99% stake is based on 110,567,222 shares of C4 Therapeutics common stock outstanding as of May 1, 2026, plus 3,383,696 shares issuable upon warrant exercise, subject to Beneficial Ownership Blockers limiting total ownership.

What securities related to CCCC does RA Capital Healthcare Fund directly hold?

RA Capital Healthcare Fund directly holds 8,000,000 common shares, plus warrants: pre-funded warrants exercisable for 8,195,000 shares, Class A warrants for 16,195,000 shares, and Class B warrants for 16,195,000 shares of C4 Therapeutics common stock.

What are the Beneficial Ownership Blockers mentioned for CCCC warrants?

Each pre-funded, Class A, and Class B warrant includes Beneficial Ownership Blockers that prevent exercise if, after exercise, the Fund and its affiliates would own more than 9.99% of C4 Therapeutics outstanding common stock, limiting exercisability at any time.

Who are the reporting persons in this CCCC Schedule 13G/A amendment?

The reporting persons are RA Capital Management, L.P., RA Capital Healthcare Fund, L.P., and individuals Peter Kolchinsky and Rajeev Shah. They file jointly but expressly disclaim status as a group and certain beneficial ownership outside Section 13(d) purposes.

Does the Fund claim beneficial ownership of all CCCC securities it holds?

The Fund disclaims beneficial ownership of the securities it holds for Section 13(d) purposes because it has delegated sole voting and investment power to RA Capital and cannot revoke that delegation on less than 61 days’ notice, though the positions are reported for compliance.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 08/14/2026 - 04:43 PM Accepted by SEC EDGAR 08/14/2026 - 04:40 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

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)

06/30/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 12529R107

1

Names of Reporting Persons

RA Capital Management, L.P.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 11,383,696.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 11,383,696.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

11,383,696.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

9.9 %

12

Type of Reporting Person (See Instructions)

IA, PN

SCHEDULE 13G

CUSIP Number(s): 12529R107

1

Names of Reporting Persons

Peter Kolchinsky

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 11,383,696.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 11,383,696.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

11,383,696.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

9.9 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

CUSIP Number(s): 12529R107

1

Names of Reporting Persons

Rajeev Shah

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 11,383,696.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 11,383,696.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

11,383,696.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

9.9 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

CUSIP Number(s): 12529R107

1

Names of Reporting Persons

RA Capital Healthcare Fund, L.P.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 11,383,696.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 11,383,696.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

11,383,696.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

9.9 %

12

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: C4 Therapeutics, Inc.
(b)	Address of issuer's principal executive offices: 490 Arsenal Way, Suite 120, Watertown, MA, 02472.
Item 2.
(a)	Name of person filing: The names of the persons filing this report (collectively, the "Reporting Persons") are: RA Capital Management, L.P. ("RA Capital") Peter Kolchinsky ("Dr. Kolchinsky") Rajeev Shah ("Mr. Shah") RA Capital Healthcare Fund, L.P. (the "Fund") The Reporting Persons expressly disclaim status as a "group" for purposes of this Schedule 13G/A.
(b)	Address or principal business office or, if none, residence: The address of the principal business office of each of the Reporting Persons is: c/o RA Capital Management, L.P., 200 Berkeley Street, 18th Floor, Boston MA 02116
(c)	Citizenship: RA Capital and the Fund are Delaware limited partnerships. Dr. Kolchinsky and Mr. Shah are United States citizens.
(d)	Title of class of securities: Common Stock, $0.0001 par value per share
(e)	CUSIP No.: 12529R107
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: Row 9 of each Reporting Person's cover page to this Schedule 13G sets forth the aggregate number of shares of common stock of the Issuer beneficially owned by such Reporting Person as of June 30, 2026 and is incorporated by reference. The Fund directly holds (i) 8,000,000 shares of common stock, (ii) pre-funded warrants (the "Pre-Funded Warrants") exercisable for up to 8,195,000 shares of common stock, (iii) Class A warrants (the "Class A Warrants") exercisable for up to 16,195,000 shares of common stock, and (iv) Class B warrants (the "Class B Warrants" and, together with the Pre-Funded Warrants and Class A Warrants, the "Warrants") exercisable for up to 16,195,000 shares of common stock. Each of the Pre-Funded Warrants, the Class A Warrants and the Class B Warrants contains a provision (the "Beneficial Ownership Blockers") which precludes exercise of the Warrants to the extent that, following exercise, the Fund, together with its affiliates and other attribution parties, would own more than 9.99% of the common stock outstanding. The Fund is currently prohibited from exercising the Warrants to the extent that such exercise would result in the Reporting Persons' beneficial ownership of more than 11,383,696 shares of common stock. RA Capital Healthcare Fund GP, LLC is the general partner of the Fund. The general partner of RA Capital is RA Capital Management GP, LLC, of which Dr. Kolchinsky and Mr. Shah are the controlling persons. RA Capital serves as investment adviser for the Fund and may be deemed a beneficial owner, for purposes of Section 13(d) of the Act, of any securities of the Issuer held by the Fund. The Fund has delegated to RA Capital the sole power to vote and the sole power to dispose of all securities held in the Fund's portfolio, including the shares of the Issuer's common stock reported herein. Because the Fund has divested voting and investment power over the reported securities it holds and may not revoke that delegation on less than 61 days' notice, the Fund disclaims beneficial ownership of the securities it holds for purposes of Section 13(d) of the Act. As managers of RA Capital, Dr. Kolchinsky and Mr. Shah may be deemed beneficial owners, for purposes of Section 13(d) of the Act, of any securities of the Issuer beneficially owned by RA Capital. RA Capital, Dr. Kolchinsky, and Mr. Shah disclaim beneficial ownership of the securities reported in this Schedule 13G/A other than for the purpose of determining their obligations under Section 13(d) of the Act, and the filing of this Schedule 13G/A shall not be deemed an admission that either RA Capital, Dr. Kolchinsky, or Mr. Shah is the beneficial owner of such securities for any other purpose.
(b)	Percent of class: Due to the Beneficial Ownership Blockers listed in the Warrants, each Reporting Person's beneficial ownership percentage was 9.99% as of June 30, 2026. Such percentage is based upon the sum of (i) 110,567,222 shares of common stock outstanding as of May 1, 2026, as reported in the Issuer's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (the "SEC") on May 12, 2026, and (ii) 3,383,696 shares of common stock issuable upon the exercise of Warrants. Due to field limitations of the EDGAR filing system, the percentages listed in Row 11 of the Reporting Persons' cover pages have been rounded down to 9.9%.
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: Row 5 of each Reporting Person's cover page to this Schedule 13G/A sets forth the sole power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person as of June 30, 2026 and is incorporated by reference.
	(ii) Shared power to vote or to direct the vote: Row 6 of each Reporting Person's cover page to this Schedule 13G/A sets forth the shared power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person as of June 30, 2026 and is incorporated by reference.
	(iii) Sole power to dispose or to direct the disposition of: Row 7 of each Reporting Person's cover page to this Schedule 13G/A sets forth the sole power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person as of June 30, 2026 and is incorporated by reference.
	(iv) Shared power to dispose or to direct the disposition of: Row 8 of each Reporting Person's cover page to this Schedule 13G/A sets forth the shared power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person as of June 30, 2026 and is incorporated by reference.
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above 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.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

RA Capital Management, L.P.

Signature:	/s/ Peter Kolchinsky
Name/Title:	By Peter Kolchinsky, Authorized Signatory
Date:	08/14/2026

Peter Kolchinsky

Signature:	/s/ Peter Kolchinsky
Name/Title:	Peter Kolchinsky
Date:	08/14/2026

Rajeev Shah

Signature:	/s/ Rajeev Shah
Name/Title:	Rajeev Shah
Date:	08/14/2026

RA Capital Healthcare Fund, L.P.

Signature:	/s/ Peter Kolchinsky
Name/Title:	By RA Capital Healthcare Fund GP, LLC, its General Partner, By Peter Kolchinsky, Manager
Date:	08/14/2026

Exhibit Information

Exhibit 99.1 Joint Filing Agreement (incorporated by reference to Exhibit 99.1 to Schedule 13G filed on October 24, 2025)