Dyne Therapeutics to Present Preclinical Data for Multiple Development Candidates for Duchenne Muscular Dystrophy (DMD) at 27th Annual NMSG Scientific Meeting

- Data support the ongoing development of four investigational therapies for DMD amenable to skipping of exons 53, 45, 44 or 55, all of which are advancing into IND-enabling studies -

- All development candidates leverage the same FORCE™ platform as zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251), which is under FDA review for exon 51 DMD -

WALTHAM, Mass., Sept. 03, 2026 (GLOBE NEWSWIRE) -- Dyne Therapeutics, Inc. (Nasdaq: DYN), a clinical-stage company focused on delivering functional improvement for people living with genetically driven neuromuscular diseases, today announced that it will present preclinical data supporting the ongoing development of DYNE-253, DYNE-245, DYNE-244 and DYNE-255 for the potential treatment of DMD amenable to skipping of exons 53, 45, 44 and 55, respectively, at the 27 th Annual Neuromuscular Study Group (NMSG) Scientific Meeting being held September 25-27, 2026, in San Antonio, TX.

“As we approach the potential launch of z-rostudirsen for individuals living with DMD amenable to exon 51 skipping, we also aim to build a leading franchise across additional mutations,” said Ranjan Batra, PhD, chief scientific officer of Dyne. “These preclinical results further strengthen our confidence in the ability of our FORCE™ platform to deliver therapeutic payloads to tissues relevant to DMD and drive meaningful exon skipping and dystrophin production, supporting advancement of these programs into IND-enabling studies.”

Data presented will include:

• In vitro exon skipping results for DYNE-253, DYNE-245, DYNE-244 and DYNE-255.

• In vivo pharmacokinetic and pharmacodynamic results for DYNE-253, including exon skipping and dystrophin levels in a Del52 mouse model of DMD.

Abstract Title: Delivering for DMD: Leveraging the FORCE platform to deliver exon skipping oligonucleotides for a broad set of DMD patients Poster Session Date and Time: Friday, September 25, 5:00-7:00 p.m. CT (6:00-8:00 p.m. ET)

The poster presentation will be available in the Scientific Publications & Presentations section of Dyne’s website at the commencement of the poster session.

Dyne Therapeutics is focused on delivering functional improvement for people living with genetically driven neuromuscular diseases. We are developing therapeutics that target muscle and the central nervous system (CNS) to address the root cause of disease. The company is advancing clinical programs for Duchenne muscular dystrophy (DMD) and myotonic dystrophy type 1 (DM1) as well as preclinical programs for facioscapulohumeral muscular dystrophy (FSHD), Pompe disease and multiple DMD mutations. At Dyne, we are on a mission to deliver functional improvement for individuals, families and communities. Learn more at https://www.dyne-tx.com/, and follow us on X, LinkedIn and Facebook.

This press release contains forward-looking statements that involve substantial risks and uncertainties. All statements, other than statements of historical facts, contained in this press release, including statements regarding Dyne’s strategy, future operations, prospects and plans, objectives of management, the potential of the FORCE TM platform, and the therapeutic potential of zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251), DYNE-253, DYNE-245, DYNE-244 and DYNE-255, the potential for a commercial launch of z-rostudirsen and future regulatory interactions, constitute forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. The words “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “might,” “objective,” “ongoing,” “plan,” “predict,” “project,” “potential,” “should,” “will,” or “would,” or the negative of these terms, or other comparable terminology are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Dyne may not actually achieve the plans, intentions or expectations disclosed in these forward-looking statements, and you should not place undue reliance on these forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in these forward-looking statements as a result of various important factors, including: uncertainties inherent in the identification and development of product candidates, including the initiation and completion of preclinical studies and clinical trials; uncertainties as to the availability and timing of results from preclinical studies and clinical trials; the timing of and Dyne’s ability to enroll patients in clinical trials; whether results from preclinical studies and initial data from early clinical trials will be predictive of the final results of the clinical trials or future trials or longer-term performance than is measured in the clinical trial; uncertainties as to the FDA’s and other regulatory authorities’ interpretation of the data from Dyne's clinical trials and acceptance of Dyne's clinical programs and the regulatory approval process, including the availability of accelerated approval pathways; whether Dyne’s cash resources will be sufficient to fund its foreseeable and unforeseeable operating expenses and capital expenditure requirements; as well as the risks and uncertainties identified in Dyne’s filings with the Securities and Exchange Commission (SEC), including the Company’s most recent Form 10-Q and in subsequent filings Dyne may make with the SEC. In addition, the forward-looking statements included in this press release represent Dyne’s views as of the date of this press release. Dyne anticipates that subsequent events and developments will cause its views to change. However, while Dyne may elect to update these forward-looking statements at some point in the future, it specifically disclaims any obligation to do so. These forward-looking statements should not be relied upon as representing Dyne’s views as of any date subsequent to the date of this press release.