C4 Therapeutics, Inc.

To the Stockholders and Board of Directors

C4 Therapeutics, Inc.:

Opinion on the Consolidated Financial Statements

We have audited the accompanying consolidated balance sheets of C4 Therapeutics, Inc. and subsidiary (the Company) as of December 31, 2025 and December 31, 2024, the related consolidated statements of operations and comprehensive loss, stockholders’ equity, and cash flows for each of the years in the two-year period ended December 31, 2025, and the related notes (collectively, the consolidated financial statements). In our opinion, the consolidated financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2025 and December 31, 2024, and the results of its operations and its cash flows for each of the years in the two-year period ended December 31, 2025, in conformity with U.S. generally accepted accounting principles.

Basis for Opinion

These consolidated financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on these consolidated financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB.

We conducted our audits in accordance with the standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the consolidated financial statements are free of material misstatement, whether due to error or fraud. The Company is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audits, we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Company’s internal control over financial reporting. Accordingly, we express no such opinion.

Our audits included performing procedures to assess the risks of material misstatement of the consolidated financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the consolidated financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the consolidated financial statements. We believe that our audits provide a reasonable basis for our opinion.

Critical Audit Matter

The critical audit matter communicated below is a matter arising from the current period audit of the consolidated financial statements that was communicated or required to be communicated to the audit committee and that: (1) relates to accounts or disclosures that are material to the consolidated financial statements and (2) involved our especially challenging, subjective, or complex judgments. The communication of a critical audit matter does not alter in any way our opinion on the consolidated financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the accounts or disclosures to which it relates.

Revenue recognition for certain research and development services

As discussed in Notes 2 and 8 to the consolidated financial statements, the Company is party to collaboration agreements which have various performance obligations, including the promise to perform research and development (R&D) services for or on behalf of the customer. For certain collaboration agreements, the Company recognizes revenue for the transaction price allocated to each of the R&D performance obligations as the R&D services are provided, using an input method, according to costs incurred as related to the research and development target and the total costs incurred and expected to be incurred in the future to satisfy that individual performance obligation. Amounts received by the Company prior to satisfying the revenue recognition criteria are recorded as deferred revenue. For the year ended December 31, 2025, the Company recognized revenue from collaboration agreements of $35.9 million, a portion of which related to R&D services performed. In addition, as of December 31, 2025, a portion of the Company’s current and net of current deferred revenue related to R&D services to be performed.

We identified the evaluation of revenue recognition for certain R&D services as a critical audit matter. Specifically, evaluating the estimate of costs expected to be incurred in satisfying certain R&D performance obligations, including the assessment of the nature of the R&D services to be performed, involved especially challenging auditor judgment.

The following are the primary procedures we performed to address this critical audit matter. For a selection of R&D performance obligations, we evaluated the estimate of total R&D service costs expected to be incurred by:

•inspecting the underlying contract with the customer to gain an understanding of the nature of the R&D services to be performed

•comparing the Company’s prior period estimates to actual R&D service costs incurred to assess the Company’s ability to estimate accurately

•inspecting underlying documentation and third-party evidence and comparing it to management’s estimate of total R&D service costs incurred and expected to be incurred

•inquiring of R&D personnel of the Company to evaluate factors related to the nature of the R&D services to be performed and their impact on the total R&D service costs to be incurred, including progress to date and the estimate of remaining R&D service costs.

We have served as the Company’s auditor since 2016.

Boston, Massachusetts

February 26, 2026