DYN

EX-99.1

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EX-99.1

EX-99.1

Exhibit 99.1

Dyne Therapeutics Reports Third Quarter 2026 Financial Results and Recent Business Highlights

- Biologics License Application (BLA) for z-rostudirsen in exon 51 Duchenne muscular dystrophy (DMD) under priority review by FDA; PDUFA target action date of January 21, 2027 -

- Additional one-year clinical data from Phase 1/2 ACHIEVE trial of z-basivarsen for myotonic dystrophy type 1 (DM1) presented at WMS and AANEM continued to support improvement at 6 months in video hand opening time (vHOT) as an early indicator of clinical benefit -

- Topline data from ACHIEVE registrational expansion cohort (REC) planned for Q1 2027 -

- Preclinical data presented at NMSG support the ongoing development of four investigational therapies for DMD amenable to skipping of exons 44, 45, 53, or 55 -

WALTHAM, Mass., November 5, 2026 – Dyne Therapeutics, Inc. (Nasdaq: DYN), a clinical-stage company focused on delivering functional improvement for people living with genetically driven neuromuscular diseases, today reported financial results for the third quarter of 2026 and recent business highlights.

“As we work toward potential commercialization, we are investing across multiple programs with the goal of unlocking the full value of our FORCETM platform,” said John Cox, president and chief executive officer of Dyne. “This includes preparations for the potential U.S. launch of z-rostudirsen for exon 51 DMD, if approved, and topline data from the registrational expansion cohort of the ACHIEVE trial for z-basivarsen in DM1, both expected in the first quarter of 2027. At the same time, we are advancing HARMONIA, the only Phase 3 clinical trial in DM1 currently enrolling participants and progressing four preclinical DMD programs that have the potential to expand our reach to over one third of individuals living with Duchenne.”

Zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251) in DMD (Duchenne muscular dystrophy)

Key milestones for z-rostudirsen

• Dyne’s BLA is under priority review by the FDA with a Prescription Drug User Fee Act (PDUFA) target action date of January 21, 2027.

• Dyne continues to expect a potential U.S. launch of z-rostudirsen in Q1 2027, assuming approval is received on the anticipated timeline.

• The ongoing confirmatory Phase 3 FORZETTO trial of z-rostudirsen is intended to support conversion of Accelerated Approval, if granted, to traditional approval in the U.S. and to support ex-U.S. marketing applications.

• In addition to z-rostudirsen, Dyne is advancing four development candidates (DYNE-244, DYNE-245, DYNE-253 and DYNE-255) for the potential treatment of DMD amenable to skipping of exons 44, 45, 53, and 55, respectively. Preclinical data supporting the ongoing development of these investigational therapies was recently presented at the 27th Annual Neuromuscular Study Group (NMSG) Scientific Meeting.

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Zeleciment basivarsen (z-basivarsen, also known as DYNE-101) in DM1 (myotonic dystrophy type 1)

Additional one-year clinical data from Phase 1/2 ACHIEVE trial

• Dyne presented additional one-year efficacy data from the multiple ascending dose (MAD) portion of the ongoing Phase 1/2 ACHIEVE clinical trial of z-basivarsen at the 31st Annual International Congress of the World Muscle Society (WMS) and the 2026 Annual Meeting of the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM).

• Data from a pooled dose group of participants initially enrolled in the MAD portion of ACHIEVE showed functional improvement versus baseline, versus placebo and versus a matched natural history cohort across multiple measures at 12 months.

Key milestones for z-basivarsen

• Topline data from the ACHIEVE REC are planned for Q1 2027 to support a potential BLA submission for U.S. Accelerated Approval in Q3 2027.

o Dyne intends to use data from the REC and from the already enrolled participants in the MAD and ongoing long-term extension portions of the ACHIEVE trial to support this potential BLA submission.

• Dyne expects a potential U.S. launch of z-basivarsen in H1 2028, assuming the FDA grants Priority Review and approval is received on the anticipated timeline.

• The ongoing confirmatory Phase 3 HARMONIA trial of z-basivarsen is intended to support conversion of Accelerated Approval, if granted, to traditional approval in the U.S. and to support ex-U.S. marketing applications.

Third Quarter Financial Results

Cash position: Cash, cash equivalents and marketable securities were $1.134 billion as of September 30, 2026. The Company expects that its cash, cash equivalents and marketable securities as of September 30, 2026, will be sufficient to fund its operations into the second quarter of 2028.

Research and development (R&D) expenses: R&D expenses were $161.7 million for the three months ended September 30, 2026 compared to $97.2 million for the three months ended September 30, 2025. The increase in R&D expense was primarily

EX-99.1

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EX-99.1

EX-99.1

Exhibit 99.1

Dyne Therapeutics Reports Second Quarter 2026 Financial Results and Recent Business Highlights

- Biologics License Application (BLA) for z-rostudirsen in exon 51 DMD accepted for review by FDA; Priority Review granted; PDUFA target action date set for January 21, 2027 -

- Completed enrollment of 71 participants in registrational expansion cohort of Phase 1/2 ACHIEVE trial of z-basivarsen in DM1; topline data planned for Q1 2027 -

- Investigational New Drug (IND) Application cleared by FDA for DYNE-302 in FSHD -

- Expected cash runway into Q2 2028 -

WALTHAM, Mass., July 29, 2026 – Dyne Therapeutics, Inc. (Nasdaq: DYN), a clinical-stage company focused on delivering functional improvement for people living with genetically driven neuromuscular diseases, today reported financial results for the second quarter of 2026 and recent business highlights.

“We continue to make significant progress as we execute on our goal of delivering functional improvement for people living with genetically driven neuromuscular diseases,” said John Cox, president and chief executive officer of Dyne. “The FDA’s acceptance of our BLA for z-rostudirsen marks an important milestone for individuals living with DMD amenable to exon 51 skipping and a defining step in Dyne’s evolution toward becoming a commercial-stage company in the near future.”

“Across our portfolio, we have achieved key clinical and regulatory milestones, including completion of enrollment in the registrational expansion cohort of ACHIEVE, initiation of the global confirmatory Phase 3 HARMONIA and FORZETTO trials, and FDA clearance of our IND for FSHD, underscoring the breadth of opportunity enabled by our FORCE™ platform. With a potential U.S. approval of z-rostudirsen in January 2027, we are investing in the capabilities needed to support patients, execute successfully as a commercial organization and maximize long-term shareholder value.”

Zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251) in DMD (Duchenne muscular dystrophy)

Phase 3 FORZETTO trial underway

• Dyne initiated the global confirmatory Phase 3 FORZETTO trial of z-rostudirsen in May 2026. Dyne has aligned with the U.S. Food and Drug Administration (FDA) on the Phase 3 trial design and protocol, which was presented at the 19th International Congress on Neuromuscular Diseases (ICNMD 2026).

Key milestones for z-rostudirsen

• Dyne’s BLA was accepted for review by the FDA in July 2026, with Priority Review granted (Prescription Drug User Fee Act (PDUFA) target action date set for January 21, 2027).

• Dyne continues to expect a potential U.S. launch of z-rostudirsen in Q1 2027, assuming approval is received on the anticipated timeline.

• Dyne also continues to pursue approval pathways outside of the U.S. for z-rostudirsen in patients with DMD who are amenable to exon 51 skipping.

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• In addition to z-rostudirsen, Dyne is advancing four development candidates (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.

Zeleciment basivarsen (z-basivarsen, also known as DYNE-101) in DM1 (myotonic dystrophy type 1)

Clinical trial execution progress

• Dyne completed enrollment of 71 participants in the registrational expansion cohort (REC) of ACHIEVE in June 2026.

• Dyne began dosing participants in the global confirmatory Phase 3 HARMONIA trial of z-basivarsen in July 2026.

Key milestones for z-basivarsen

• Topline data from the ACHIEVE REC are planned for Q1 2027 to support a potential BLA submission for U.S. Accelerated Approval in Q3 2027.

o Dyne intends to use data from the REC and from the already enrolled participants in the multiple ascending dose (MAD) and ongoing long-term extension portions of the ACHIEVE trial to support this potential BLA submission.

• Dyne expects a potential U.S. launch of z-basivarsen in H1 2028, assuming the FDA grants Priority Review and approval is received on the anticipated timeline.

• Dyne also continues to pursue approval pathways outside of the U.S. for z-basivarsen in DM1.

DYNE-302 in FSHD (facioscapulohumeral muscular dystrophy)

IND clearance and Phase 1 trial overview

• Dyne received clearance from the FDA in July 2026 for its IND application to initiate a Phase 1 clinical trial for DYNE-302 in FSHD. DYNE-302 leverages the same FORCETM platform as Dyne’s first two clinical programs, z-rostudirsen in exon 51 DMD and z-basivarsen in DM1.

• Dyne plans to evaluate DYNE-302 in a Phase 1 randomized, placebo-controlled, double-blind, MAD clinical trial in ambulatory adult individuals with FSHD. The primary endpoint will be safety and tolerability. The trial will also assess pharmacokinetics and pharmacodynamics, including change from baseline in muscle DUX4 transcriptome and plasma KHDC1L levels, which Dyne has independently identified as a DUX4-regulated biomarker in FSHD.

• Dyne intends to pursue a t

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