Dyne Therapeutics Inc

To the Stockholders and Board of Directors of Dyne Therapeutics, Inc.

Opinion on the Financial Statements

We have audited the accompanying consolidated balance sheets of Dyne Therapeutics, Inc. and subsidiary (the "Company") as of December 31, 2024 and 2023, the related consolidated statements of operations and comprehensive loss, stockholders' equity, and cash flows for the years then ended and the related notes (collectively referred to as the "financial statements"). In our opinion, the financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2024 and 2023, and the results of its operations and its cash flows for each of the three years in the period ended December 31, 2024, in conformity with accounting principles generally accepted in the United States of America.

We have also audited, in accordance with the standards of the Public Company Accounting Oversight Board (United States) (PCAOB), the Company's internal control over financial reporting as of December 31, 2024, based on criteria established in Internal Control — Integrated Framework (2013) issued by the Committee of Sponsoring Organizations of the Treadway Commission and our report dated February 27, 2025, expressed an unqualified opinion on the Company's internal control over financial reporting.

Basis for Opinion

These financial statements are the responsibility of the Company's management. Our responsibility is to express an opinion on the Company's financial statements based on our audits. We are a public accounting firm registered with the 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 financial statements are free of material misstatement, whether due to error or fraud. Our audits included performing procedures to assess the risks of material misstatement of the 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 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 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 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 financial statements and (2) involved our especially challenging, subjective, or complex judgments. The communication of critical audit matters does not alter in any way our opinion on the 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.

Accrued and Prepaid Research and Development Expense – Refer to Note 2 and 6 to the financial statements.

Critical Audit Matter Description

The Company records accrued expenses and prepaid expenses associated with ongoing research and development costs, including costs associated with outsourced agreements for clinical trials with contract research organizations (CROs) and production of research materials with contract manufacturing organizations (CMOs). Estimates of expenses incurred are determined by analyzing progress of the studies, including phase or completion of events, invoices received, payments made, communication with third-party CROs and CMOs, and internal tracking of work completed to date. Expenses incurred in excess of amounts invoiced are recorded as accrued expenses. Payments made in excess of expenses incurred are recorded as prepaid costs. We note that these balances are included in the “Accrued Expenses” and “Prepaid expenses and other current assets”, respectively, in the financial statements. We identified auditing the estimates of the extent of work performed by CROs and CMOs as a critical audit matter because of the level of management judgment required and volume of such estimates made by management. This required a high degree of auditor judgment and an increased extent of effort when performing audit procedures to evaluate the reasonableness of management’s estimates.

How the Critical Audit Matter Was Addressed in the Audit

Our audit procedures related to accrued and prepaid research and development expenses included the following, among others:

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We tested the design and effectiveness of controls over the estimation of accrued and prepaid research and development expenses.

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For a sample of studies and clinical trials, we performed the following:

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Inspected the related contracts, purchase orders, statements of work and other contractual documentation.

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Tested the completeness and accuracy of the underlying data used to develop the estimates.

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Performed corroborating inquiries with the Company’s research and development personnel.

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Inspected information from third-party service providers to understand the nature and progress of the studies.

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Obtained corresponding invoices and evidence of payment to third-party service providers.

/s/Deloitte & Touche LLP

Boston, Massachusetts

February 27, 2025

We have served as the Company’s auditor since 2020.