Results of Operations and Financial Condition. On July 29, 2026, Dyne Therapeutics, Inc. (the “Company”) issued a press release announcing the Company’s financial results for the quarter ended June 30, 2026. A copy of the press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference. The information in this Form 8-K, including Exhibit 99.1 attached hereto, is being furnished and shall not be deemed “filed” for purposes of Section 18 of t…

Entry Into a Material Definitive Agreement. On July 21, 2026, Dyne Therapeutics, Inc. (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with Morgan Stanley & Co. LLC and Jefferies LLC, as representatives of the several underwriters named therein (the “Underwriters”), relating to an underwritten public offering (the “Offering”) of 18,300,000 shares (the “Underwritten Shares”) of the Company’s common stock, par value $0.0001 per share (the “Common Stock”). Al…

Other Events. Pricing of Public Offering The full text of the press release issued on July 21, 2026, announcing the pricing of the Offering, is attached as Exhibit 99.1 hereto and is incorporated herein by reference. Cash Runway The Company believes that the net proceeds from the Offering, together with its existing cash, cash equivalents and marketable securities, including the third term loan tranche of $50.0 million that it borrowed under the Loan and Security Agreement (the “Loan Agreemen…

Other Events. On July 20, 2026, Dyne Therapeutics, Inc. (the “Company”) announced that the U.S. Food and Drug Administration (“FDA”) has accepted for review its biologics license application (“BLA”) for zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251) for the treatment of individuals with Duchenne muscular dystrophy (“DMD”) amenable to exon 51 skipping. The FDA has granted the BLA Priority Review and assigned a Prescription Drug User Fee Act target action date of January 21, 202…

Director — Barry E. Greene: Mr. Barry E. Greene was elected as a Class I director to the Board of Directors.

Entry Into a Material Definitive Agreement. On June 16, 2026 (the “Amendment Closing Date”), Dyne Therapeutics, Inc. (the “Company”) entered into the Second Amendment (the “Second Amendment”) to its Loan and Security Agreement with Hercules Capital, Inc., in its capacity as administrative agent and collateral agent (the “Agent”), and certain other financial institutions party thereto as lenders (collectively, the “Lenders”), dated as of June 27, 2025 (the “Initial Loan Agreement” and as amend…

of the Company’s Current Report on Form 8-K filed with the Securities and Exchange Commission on December 8, 2025, and those terms are also incorporated by reference into this

Other Events. On June 3, 2026, the Company issued a press release announcing full enrollment of the REC of its Phase 1/2 ACHIEVE trial of z-basivarsen in individuals with DM1 with 71 participants. Additionally, the Company announced the following key milestones for z-basivarsen: • Topline data from the ACHIEVE REC are planned for the first quarter of 2027 to support a potential Biologics License Application (“BLA”) for U.S. Accelerated Approval in the third quarter of 2027. • The Company inte…

Results of Operations and Financial Condition. On May 11, 2026, Dyne Therapeutics, Inc. (the “Company”) issued a press release announcing the Company’s financial results for the quarter ended March 31, 2026. A copy of the press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference. The information in this Form 8-K, including Exhibit 99.1 attached hereto, is being furnished and shall not be deemed “filed” for purposes of Section 18 of t…

Results of Operations and Financial Condition. On March 2, 2026, Dyne Therapeutics, Inc. (the “Company”) issued a press release announcing the Company’s financial results for the year ended December 31, 2025. A copy of the press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference. The information in this Form 8-K, including Exhibit 99.1 attached hereto, is being furnished and shall not be deemed “filed” for purposes of Section 18 of…

Results of Operations and Financial Condition. Dyne Therapeutics, Inc. (the “Company”) disclosed on January 12, 2026, that although it has not finalized its full financial results for the fourth quarter and fiscal year ended December 31, 2025, it expects to report cash, cash equivalents and marketable securities of approximately $1.1 billion as of December 31, 2025. The estimated cash figure is preliminary and unaudited, represents a management estimate as of the date of this Current Report o…

Director — Vikram Karnani: Election of Vikram Karnani as a Class II director.

Other Events. Pricing of Public Offering The full text of the press release issued on December 9, 2025, announcing the pricing of the Offering, is attached as Exhibit 99.1 hereto and is incorporated herein by reference. Cash Runway The Company believes that the net proceeds from the Offering, together with its existing cash, cash equivalents and marketable securities, including the second term loan tranche of $50.0 million that the Company borrowed under its Loan and Security Agreement (the “…

Entry Into a Material Definitive Agreement. On December 9, 2025, Dyne Therapeutics, Inc. (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with Morgan Stanley & Co. LLC, Jefferies LLC, Stifel, Nicolaus & Company, Incorporated and Guggenheim Securities, LLC, as representatives of the several underwriters named therein (the “Underwriters”), relating to an underwritten public offering (the “Offering”) of 18,980,478 shares (the “Underwritten Shares”) of the Com…

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. On December 8, 2025 (the “Amendment Closing Date”), Dyne Therapeutics, Inc. (the “Company”) entered into the First Amendment (the “First Amendment”) to Loan and Security Agreement with Hercules Capital, Inc. (“Hercules”), in its capacity as administrative agent and collateral agent (the “Agent”), and certain other financial institutions party thereto as lenders (collectively, the…

Other Events. On December 8, 2025, the Company issued a press release announcing positive topline results from the REC of its DELIVER trial evaluating z-rostudirsen in individuals with DMD amenable to exon 51 skipping. Additionally, the Company announced new positive long-term clinical data from the ongoing OLE and LTE portions of the DELIVER trial. The REC met its primary endpoint, demonstrating a statistically significant increase in muscle content-adjusted dystrophin expression to 5.46% of…

of the Company’s Current Report on Form 8-K filed with the Securities and Exchange Commission on June 30, 2025 (the “Initial Loan Agreement Form 8-K”) and those terms are incorporated by reference into this

Results of Operations and Financial Condition. On November 5, 2025, Dyne Therapeutics, Inc. (the “Company”) issued a press release announcing the Company’s financial results for the quarter ended September 30, 2025. A copy of the press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference. The information in this Form 8-K, including Exhibit 99.1 attached hereto, is being furnished and shall not be deemed “filed” for purposes of Section…

Director — Brian Posner: Election of Brian Posner as a Class III director.

Results of Operations and Financial Condition. On July 28, 2025, Dyne Therapeutics, Inc. (the “Company”) issued a press release announcing the Company’s financial results for the quarter ended June 30, 2025. A copy of the press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference. The information in this Form 8-K, including Exhibit 99.1 attached hereto, is being furnished and shall not be deemed “filed” for purposes of Section 18 of t…

Other Events. Pricing of Public Offering The full text of the press release issued on June 30, 2025, announcing the pricing of the Offering is attached as Exhibit 99.1 hereto and is incorporated herein by reference. Cash Runway The Company believes that the net proceeds from the Offering, together with its existing cash, cash equivalents and marketable securities, including the initial term loan tranche of $100.0 million that the Company borrowed under its Loan and Security Agreement (the “Lo…

Entry Into a Material Definitive Agreement. On June 30, 2025, Dyne Therapeutics, Inc. (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with Morgan Stanley & Co. LLC, Jefferies LLC, Stifel, Nicolaus & Company, Incorporated and Guggenheim Securities, LLC, as representatives of the several underwriters named therein (the “Underwriters”), relating to an underwritten public offering (the “Offering”) of 24,242,425 shares (the “Underwritten Shares”) of the Compan…

Entry into a Material Definitive Agreement. On June 27, 2025 (the “Closing Date”), Dyne Therapeutics, Inc. (the “Company”) entered into a Loan and Security Agreement (the “Loan Agreement”) with Hercules Capital, Inc. (“Hercules”), in its capacity as administrative agent and collateral agent (the “Agent”) and as a lender, and certain other financial institutions that from time to time become parties to the Loan Agreement as lenders (collectively, the “Lenders”). The Loan Agreement provides for…

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. The information set forth in

Other Events. On June 17, 2025, the Company issued a press release announcing that the FDA has granted Breakthrough Therapy Designation to DYNE-101 for the treatment of DM1. The Company also announced an updated plan for obtaining U.S. Accelerated Approval for DYNE-101 in DM1 following a Type C meeting with the FDA and analysis of new long-term functional data. Accelerated Approval Pathway for DYNE-101 in DM1 • In May 2025, the Company participated in a Type C meeting with the Center for Drug…