Pfizer to Supply Elranatamab for C4's Phase 1b Cemsidomide Study

Rhea-AI Filing Summary

C4 Therapeutics, Inc. announced on October 1, 2025 that it entered a clinical trial collaboration and supply agreement with Pfizer. Under the agreement, Pfizer will supply elranatamab (ELREXFIO®), a BCMAxCD3 bispecific antibody, at no cost for C4's upcoming Phase 1b trial testing the safety and tolerability of cemsidomide plus dexamethasone in combination with elranatamab for patients receiving second-line or later therapy for multiple myeloma. C4 will sponsor and run the trial while Pfizer will receive access to trial data. The company furnished a press release as Exhibit 99.1 to the current report.

Positive

• Elranatamab supplied at no cost, reducing trial drug expense for the sponsor
• Phase 1b trial launched to test cemsidomide+dexamethasone with a clinically relevant bispecific in later‑line multiple myeloma
• Pfizer gains data access, aligning incentives for timely data collection and potential follow‑on collaboration

Negative

• No financial consideration disclosed, so the deal's long‑term commercial or revenue implications are unclear
• Data access in exchange for supply may limit C4's exclusive control over resulting data exploitation
• Safety and tolerability unknown for the combination; adverse findings could delay development

Insights

Clinical Development Strategist

Collaboration reduces drug supply costs and accelerates combination testing.

The agreement provides elranatamab supply at no cost, which lowers trial expense and ensures access to a late‑stage bispecific for a Phase 1b combination study with cemsidomide and dexamethasone. That supports testing a biologic+small‑molecule regimen in relapsed multiple myeloma without immediate drug procurement delays.

The main dependencies are trial enrollment and safety readouts; if the combination shows acceptable tolerability, data sharing with Pfizer could enable joint learning or future collaborations within 2025–2026 development timelines.

Corporate Partnering Analyst

Data access is the primary commercial currency in the deal.

Pfizer supplies the investigational agent in exchange for access to trial data rather than an upfront payment, indicating a data‑for‑supply structure that conserves cash for the sponsor and provides Pfizer strategic insights into combination safety and activity.

Key near‑term items to watch are the trial initiation date and first safety data from the Phase 1b cohort, which will determine whether further joint activities or broader collaboration terms become relevant.

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

_________________________________________________________________

FORM 8-K

_________________________________________________________________

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): October 1, 2025

_________________________________________________________________

C4 THERAPEUTICS, INC.

(Exact name of Registrant as Specified in Its Charter)

_________________________________________________________________

Delaware			001-39567			47-5617627
(State or Other Jurisdiction of Incorporation)			(Commission File Number)			(IRS Employer Identification No.)
490 Arsenal Way,   Suite 120 Watertown,  MA						02472
(Address of Principal Executive Offices)						(Zip Code)

Registrant’s Telephone Number, Including Area Code: (617) 231-0700

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

_________________________________________________________________

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

o			Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
o			Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
o			Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))
o			Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class

Trading Symbol(s)

Name of each exchange on which registered

Common Stock, $0.0001 par value per share

CCCC

The Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company o

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. o

Item 7.01 Regulation FD Disclosure.

On October 1, 2025, C4 Therapeutics, Inc. (the “Company”) issued a press release announcing that the Company had entered into a clinical trial collaboration and supply agreement (the “Agreement”) with Pfizer Inc. (“Pfizer”). A copy of this press release is being furnished as Exhibit 99.1 to this Current Report on Form 8-K.

The information contained in Item 7.01 of this Current Report on Form 8-K and Exhibit 99.1 is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended (the “Securities Act”), or the Exchange Act, except as expressly set forth by specific reference in such a filing. The furnishing of this information hereby shall not be deemed an admission as to the materiality of any such information.

Item 8.01 Other Events.

On October 1, 2025, the Company announced that it had entered into the Agreement with Pfizer. Under the terms of the Agreement, Pfizer will supply elranatamab (ELREXFIO®), a B-cell maturation antigen CD3 targeted bispecific antibody (BCMAxCD3 bispecific), to the Company for its upcoming Phase 1b trial evaluating the safety and tolerability of cemsidomide, an IKZF1/3 degrader, and dexamethasone in combination with elranatamab as a second line or later therapy for patients with multiple myeloma. Pursuant to the Agreement, Pfizer will supply elranatamab to the Company at no cost in exchange for access to data from the trial, while the Company will sponsor and conduct the trial.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits. The exhibits shall be deemed to be filed or furnished, depending on the relevant item requiring such exhibit, in accordance with the provisions of Item 601 of Regulation S-K (17 CFR 229.601) and Instruction B.2 to this form.

Exhibit Number						Description
99.1						Press release issued October 1, 2025
104						Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

			C4 Therapeutics, Inc.
Date: October 1, 2025			By:			/s/ Jolie M. Siegel
						Jolie M. Siegel
						Chief Legal Officer and Secretary

FAQ

What did C4 Therapeutics (CCCC) announce in the 8-K?

C4 announced a clinical trial collaboration and supply agreement with Pfizer to receive elranatamab at no cost for a Phase 1b combination trial.

What product will Pfizer supply to C4?

Elranatamab (ELREXFIO®), a BCMAxCD3 bispecific antibody, will be supplied for the trial.

What regimen will be tested in the Phase 1b trial?

The trial will evaluate cemsidomide, an IKZF1/3 degrader, plus dexamethasone in combination with elranatamab for second‑line or later multiple myeloma patients.

Who will sponsor and run the clinical trial?

C4 Therapeutics will sponsor and conduct the trial, while Pfizer supplies the investigational drug and receives access to the trial data.

Does the filing disclose any payments from Pfizer to C4?

No payments are disclosed; the filing states Pfizer will supply the drug at no cost in exchange for data access.