DYN

- 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 (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 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. 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. 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 traditional approval pathway in the U.S. for DYNE-302. Financing Updates Dyne entered into an amendment to its non-dilutive senior secured term loan facility with Hercules Capital, Inc. in June 2026, expanding its debt facility to up to $400 million. Dyne completed an underwritten public offering of 21,045,000 shares of its common stock at a public offering price of $20.50 per share in July 2026. The gross proceeds from the offering before deducting underwriting discounts and commissions and offering expenses payable by Dyne were approximately $431 million. Second Quarter Financial Results Cash position: Cash, cash equivalents and marketable securities were $898.5 million as of June 30, 2026. In July 2026, the Company completed an underwritten public offering of 21,045,000 shares of its common stock for estimated net proceeds of approximately $405.0 million. The Company expects that its cash, cash equivalents and marketable securities as of June 30, 2026, together with the net proceeds from the July 2026 underwritten public offering, will be sufficient to fund its operations into the second quarter of 2028. Research and development (R&D) expenses: R&D expenses were $152.2 million for the three months ended June 30, 2026 compared to $99.2 million for the three months ended June 30, 2025. The increase in R&D expense was primarily due to increased manufacturing activity and higher clinical costs related to z-rostudirsen and z-basivarsen during the three months ended June 30, 2026. General and administrative (G&A) expenses: G&A expenses were $29.5 million for the three months ended June 30, 2026 compared to $16.6 million for the three months ended June 30, 2025. The increase in G&A expenses was primarily due to increased costs in preparation for the potential launch of z-rostudirsen. Net loss: Net loss for the three months ended June 30, 2026 was $178.6 million, or $1.08 per basic and diluted share. This compares with a net loss of $110.9 million, or $0.97 per basic and diluted share, for the three months ended June 30, 2025. About Dyne Therapeutics 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. Forward-Looking Statements 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, projections and plans; objectives of management; the potential of the FORCE platform; the potential of zeleciment basivarsen (z-basivarsen, also known as DYNE-101), zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251), DYNE-253, DYNE-245, DYNE-244, DYNE-255 and DYNE-302; the anticipated timelines for initiating additional clinical trials, reporting data from clinical trials, submitting applications for marketing approval and launching commercially; the availability of an expedited approval pathway for z-basivarsen; expectations regarding the potential timing of regulatory approval, commercial launch and the outcome of interactions with regulatory authorities; and the sufficiency of Dyne’s cash resources for the period anticipated, 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 clinical trials; uncertainties as to the availability and timing of results from clinical trials; uncertainties as to the timing of and Dyne’s ability to enroll patients in clinical trials; whether results from preclinical studies and data from clinical trials will be predictive of the final results of the clinical trials or other trials; whether data from clinical trials will support submission for regulatory approvals; 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 as to the regulatory approval process for Dyne’s product candidates; whether Dyne’s cash resources will be sufficient to fund its foreseeable and unforeseeable operating expenses, debt service obligations 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. Contacts: Investors Mia [email protected] 781-317-0353 Media Stacy [email protected]

- Positive pre-BLA meeting completed with FDA for z-rostudirsen in exon 51 DMD; on track for BLA submission in Q2 2026 and potential launch in Q1 2027 - - Positive cardiopulmonary results and long-term dystrophin data from Phase 1/2 DELIVER trial of z-rostudirsen in exon 51 DMD presented at MDA conference - - Completion of enrollment in registrational expansion cohort of Phase 1/2 ACHIEVE trial of z-basivarsen in DM1 on track for Q2 2026; global confirmatory Phase 3 HARMONIA trial initiated - - New preclinical data to be presented at ASGCT underscore differentiated capability of clinically validated FORCETM platform to cross the blood-brain barrier - WALTHAM, Mass., May 11, 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 reported financial results for the first quarter of 2026 and recent business highlights. “Following positive topline data late last year, we continue to ramp up activities to support a potential launch of z-rostudirsen in DMD in the first quarter of 2027,” said John Cox, president and chief executive officer of Dyne. “We are grateful to the FDA for a collaborative pre-BLA meeting, where we aligned on the contents of our planned BLA submission for U.S. Accelerated Approval of z-rostudirsen, which is on track for this quarter.” “In DM1, we have reached our target of 60 participants in the registrational expansion cohort of the ACHIEVE trial of z-basivarsen. Based on a recent acceleration in the number of participants in screening, we currently expect to exceed this target when we complete enrollment later this quarter. As we look toward the important expected readout in the first quarter of 2027, we continue to be driven by our goal to deliver functional improvement for individuals living with DM1. We remain committed to disciplined execution as we advance our two lead programs and broader pipeline and aim to maximize returns for our shareholders,” concluded Mr. Cox. Zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251) in DMD (Duchenne muscular dystrophy) Positive cardiopulmonary results and long-term dystrophin data from the DELIVER trial In March 2026, at the 2026 Muscular Dystrophy Association (MDA) Clinical & Scientific Conference, Dyne presented positive results of new analyses of cardiac and pulmonary function among all DELIVER participants who were randomized to z-rostudirsen treatment at baseline (any dose1) and for whom cardiac magnetic resonance imaging and/or pulmonary function data were available. At the 2026 MDA Conference, Dyne also presented long-term data on dystrophin production from four participants in the DELIVER trial who had been dosed with 20 mg/kg Q4W for at least 12 months (67-104 weeks) at the time of an optional biopsy. Unadjusted dystrophin production in these participants reached an average of 9.48% of normal (n=4) as compared to 0.52% at baseline (n=3), and muscle content-adjusted dystrophin production reached an average of 18.33% of normal (n=4) as compared to 1.47% at baseline (n=3). In previously reported safety and tolerability data from 86 total participants enrolled in the DELIVER trial and followed for up to 36 months, z-rostudirsen demonstrated a favorable safety profile,2 and most related treatment emergent adverse events (TEAEs) were mild or moderate. The most commonly reported related TEAEs were pyrexia (fever) and headache. No related serious TEAEs were observed in the registrational expansion cohort (REC). Key milestones for z-rostudirsen Dyne has completed a positive pre-BLA meeting with the U.S. Food and Drug Administration (FDA) and remains on track to submit a Biologics License Application (BLA) for U.S. Accelerated Approval in Q2 2026. Dyne plans to initiate a global confirmatory Phase 3 clinical trial of z-rostudirsen in Q2 2026. Dyne has aligned with the FDA on the Phase 3 trial design and protocol. Dyne continues to expect a potential U.S. launch of z-rostudirsen in Q1 2027, 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-rostudirsen in patients with DMD who are amenable to exon 51 skipping. 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) Phase 3 HARMONIA trial underway Dyne initiated the global confirmatory Phase 3 HARMONIA trial of z-basivarsen in March 2026. Dyne has aligned with the FDA on the Phase 3 trial design and protocol, which was presented at the 2026 MDA Clinical & Scientific Conference. Key milestones for z-basivarsen Dyne has reached its enrollment target of 60 participants in the ACHIEVE REC. Dyne plans to allow any participants currently in screening to enroll if they meet all eligibility criteria. As a result, Dyne expects to complete enrollment of more than 60 participants in Q2 2026. Data from this cohort are planned for Q1 2027 to support a potential BLA submission for U.S. Accelerated Approval in early Q3 2027. 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 a potential submission for Accelerated Approval in the U.S. Dyne expects a potential U.S. launch of z-basivarsen in Q1 2028, assuming 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. New preclinical data showing robust central nervous system (CNS) activity in nonhuman primates with FORCE platform This week, Dyne is presenting new preclinical data highlighting the differentiated capability of the clinically validated FORCE platform to cross the blood-brain barrier. The oral presentation will take place on Wednesday, May 13, at 10:30 a.m. ET at the American Society of Gene + Cell Therapy (ASGCT) 2026 Annual Meeting being held in Boston, MA, and virtually. First Quarter Financial Results Cash position: Cash, cash equivalents and marketable securities were $972.2 million as of March 31, 2026. The Company continues to expect that its cash, cash equivalents and marketable securities as of March 31, 2026, will be sufficient to fund its operations into the first quarter of 2028. Research and development (R&D) expenses: R&D expenses were $100.9 million for the three months ended March 31, 2026 compared to $106.4 million for the three months ended March 31, 2025. The decrease in R&D expense was primarily due to the timing of manufacturing batches of z-rostudirsen and z-basivarsen. General and administrative (G&A) expenses: G&A expenses were $24.4 million for the three months ended March 31, 2026 compared to $15.9 million for the three months ended March 31, 2025. The increase in G&A expenses was primarily due to increased costs in preparation for the potential launch of z-rostudirsen. Net loss: Net loss for the three months ended March 31, 2026 was $120.9 million, or $0.73 per basic and diluted share. This compares with a net loss of $115.4 million, or $1.05 per basic and diluted share, for the three months ended March 31, 2025. About Dyne Therapeutics 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. Forward-Looking Statements 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, projections and plans; objectives of management; the potential of the FORCE platform; the potential of zeleciment basivarsen (z-basivarsen, also known as DYNE-101) and zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251); the anticipated timelines for initiating additional clinical trials, reporting data from clinical trials, enrolling registrational cohorts, submitting applications for marketing approval and launching commercially; the availability of expedited approval pathways for z-basivarsen and z-rostudirsen; expectations regarding the potential timing of regulatory approval, commercial launch and the outcome of interactions with regulatory authorities; and the sufficiency of Dyne’s cash resources for the period anticipated, 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 clinical trials; uncertainties as to the availability and timing of results from clinical trials; uncertainties as to the timing of and Dyne’s ability to enroll patients in clinical trials; whether results from preclinical studies and data from clinical trials will be predictive of the final results of the clinical trials or other trials; whether data from clinical trials will support submission for regulatory approvals; 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 as to the regulatory approval process for Dyne’s product candidates; whether Dyne’s cash resources will be sufficient to fund its foreseeable and unforeseeable operating expenses, debt service obligations 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. Contacts: Investors Mia Tobias [email protected] 781-317-0353 Media Stacy Nartker [email protected] 781-317-1938

- New analyses out to 24-months showed improvement in heart and lung function compared to expected declines in DMD natural history - - Data expand on previously reported results demonstrating that z-rostudirsen treatment led to sustained functional improvement across multiple clinical measures - WALTHAM, Mass., March 08, 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 additional positive data from the ongoing Phase 1/2 DELIVER clinical trial of zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251), in individuals with Duchenne muscular dystrophy (DMD) amenable to exon 51 skipping. These data are being presented in a late-breaking poster presentation at the 2026 Muscular Dystrophy Association (MDA) Clinical & Scientific Conference being held March 8-11, 2026, in Orlando, FL, which is available in the Scientific Publications & Presentations section of Dyne’s website along with all of Dyne’s other posters being presented at the conference. “This week we are presenting additional analyses of 24-month data from the DELIVER trial showing the breadth of potential benefits z-rostudirsen may bring to individuals with exon 51 skip amenable DMD beyond the previously reported unprecedented improvements in muscle function,” said Doug Kerr, M.D., Ph.D., chief medical officer of Dyne. “Cardiopulmonary issues are a key area of concern in DMD, so we are particularly encouraged by new analyses showing improvement in both heart and lung function out to 24 months. We attribute these results to the differentiated capabilities of our FORCE platform to deliver therapeutics to a broad range of muscles, including the heart, trunk and diaphragm, as well as the CNS.” Dyne announced the results of new analyses of cardiac and pulmonary function amongst all DELIVER participants who were randomized to z-rostudirsen treatment at baseline (any dose1) and for whom cardiac magnetic resonance imaging and/or pulmonary function data were available. Improvement from baseline in lung function, as measured by Forced Vital Capacity Percent Predicted (FVC%p), was observed through 24 months, as compared to the expected decline estimated in published natural history data2-4. Improvement from baseline was observed through 24 months in circumferential strain, an early signal of cardiac performance, as compared to the expected worsening estimated in published natural history data5,6. Improvement from baseline in left ventricular ejection fraction, a measure of how well the heart is pumping, was observed at 24 months, in contrast with the expected decline estimated in published natural history data5,6. In previously reported safety and tolerability data from 86 total participants enrolled in the DELIVER trial and followed for up to 36 months, z-rostudirsen demonstrated a favorable safety profile7, and most related treatment emergent adverse events (TEAEs) were mild or moderate. The most commonly reported related TEAEs were pyrexia (fever) and headache. No related serious TEAEs were observed in the REC. These data will be presented in a poster titled “Zeleciment rostudirsen led to trends in long-term improvement in clinical outcomes including cardiopulmonary function: Additional data from DELIVER” (poster # 476 LBT). About the DELIVER Trial DELIVER is a global, randomized, placebo-controlled, double-blind, Phase 1/2 clinical trial that evaluated the safety, tolerability and efficacy (as measured by both biomarker and functional improvement) of zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251) in individuals with Duchenne muscular dystrophy (DMD) who have mutations in the DMD gene that are amenable to exon 51 skipping. The multiple ascending dose (MAD) portion of the study resulted in the selection of a registrational dose and regimen of 20 mg/kg of z-rostudirsen administered every four weeks. The placebo-controlled portion of the registrational expansion cohort (REC) to support a potential regulatory submission for U.S. Accelerated Approval has been completed. The primary endpoint for this cohort was the change from baseline in dystrophin protein levels as measured by Western blot at 6 months. Participants from the MAD and REC portions had the option to enroll in the open-label extension and long-term extension portions of the study. For more information on the DELIVER trial, visit clinicaltrials.gov and euclinicaltrials.eu. About zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251) Z-rostudirsen is an investigational therapeutic being evaluated in the Phase 1/2 global DELIVER clinical trial for individuals with DMD who have mutations in the DMD gene that are amenable to exon 51 skipping. Z-rostudirsen consists of a phosphorodiamidate morpholino oligomer (PMO) conjugated to an antigen-binding fragment (Fab) that binds to the transferrin receptor 1 (TfR1). It is designed to enable the production of near full-length dystrophin in muscle and the central nervous system (CNS) to provide functional improvement. Z-rostudirsen has received Breakthrough Therapy, Fast Track and Rare Pediatric Disease designations from the U.S. Food and Drug Administration (FDA), as well as Orphan Drug designation from the FDA and European Medicines Agency (EMA) and the Ministry of Health, Labour and Welfare (MHLW) in Japan for the treatment of individuals with DMD amenable to exon 51 skipping. In addition to z-rostudirsen, Dyne is building a DMD franchise and has preclinical programs targeting other exons, including DYNE-253, DYNE-245, DYNE-244 and DYNE-255. About Duchenne Muscular Dystrophy (DMD) Duchenne muscular dystrophy (DMD) is a rare X-linked progressive neuromuscular disorder caused by mutations in the DMD gene. These mutations result in a complete or near-complete absence of dystrophin, a protein critical for maintaining muscle structure and function. DMD is the most common form of childhood-onset muscular dystrophy, affecting approximately 12,000 individuals in the U.S. and 16,000 in the EU. Symptoms typically emerge between ages 3 and 5, beginning with muscle weakness in the upper arms, thighs and pelvic region, and progressively impacting the lower limbs, forearms, neck and trunk. In addition to physical decline, individuals may experience cognitive impairment and neuropsychiatric challenges such as intellectual disabilities, learning difficulties and behavioral disorders. Despite existing therapies, there remains a significant unmet need for new treatment options that deliver functional improvement. About Dyne Therapeutics 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. Forward-Looking Statements 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 platform, the clinical potential of zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251) and its potential cardiopulmonary effects, and expectations regarding the availability of accelerated approval pathways for z-rostudirsen, 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; whether results from preclinical studies and initial data from clinical trials will be predictive of the final results of the clinical trials or future trials; uncertainties as to the FDA’s and other regulatory authorities’ interpretation of the data from Dyne's clinical trials and the regulatory approval process; 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-K 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. Contacts: Investors Mia Tobias [email protected] 781-317-0353 Media Stacy Nartker [email protected] 781-317-1938

Never miss an important update on your stock portfolio and cut through the noise. Over 7 million investors trust Simply Wall St to stay informed where it matters for FREE. Dyne Therapeutics (DYN) is back in focus after Q4 2025 results showed a loss per share that came in ahead of expectations, alongside continued net losses and detailed progress in its late stage pipeline. See our latest analysis for Dyne Therapeutics. Despite Q4 earnings beating expectations, Dyne Therapeutics' recent share price has eased. The 30 day share price return is 19.83% and the 90 day share price return is 25.05%, while the 1 year total shareholder return of 24.18% indicates that longer term holders have still seen gains. This suggests some momentum has cooled as investors weigh clinical progress against ongoing losses and recent financing steps such as the shelf registration. If this earnings update has you thinking about other neuromuscular and biotech names, it could be a good moment to scan through 32 healthcare AI stocks as potential ideas to research next. With shares giving back some of their recent gains and the stock trading at a discount to analyst targets, investors now face a simple question: is this weakness a genuine opening, or is the market already pricing in Dyne’s future growth? On the numbers provided, Dyne Therapeutics trades on a P/B of 2.6x, which sits slightly below the US biotechs industry average of 2.7x and well below the peer group average of 8.7x. At a last close of $15.20 and with the shares described as trading at an 88.2% discount to an internal fair value estimate, the market is clearly pricing Dyne as a higher risk, loss making clinical stage name, but not at the premium levels seen across many peers. P/B looks at what investors are paying relative to the company’s net assets on the balance sheet. This tends to be a common yardstick for pre revenue and unprofitable biotechs where traditional earnings based metrics are less useful. For Dyne, this metric is being applied to a business that reports no meaningful revenue, a net loss of $446.214m and a negative return on equity of 45.9%, alongside forecasts that it will remain unprofitable over the next three years. The combination of a modest P/B versus the broader biotech industry and a much lower P/B than the 8.7x peer average suggests the market is putting a materially lower price on Dyne’s balance sheet and pipeline than on comparable companies. At the same time, the SWS DCF model points to a future cash flow value of $128.28 per share versus the current $15.20. This is a very large gap that reflects how sensitive this kind of model can be to long term assumptions for companies that are still loss making and forecast to have no revenue next year. See what the numbers say about this price — find out in our valuation breakdown. Result: Price-to-Book of 2.6x (UNDERVALUED) However, you still need to factor in clinical trial uncertainty and ongoing net losses of $446.214m. These could pressure funding needs and sentiment. Find out about the key risks to this Dyne Therapeutics narrative. While the 2.6x P/B ratio suggests Dyne looks inexpensive against both the industry and peers, the SWS DCF model goes much further, with a future cash flow value of $128.28 per share versus today’s $15.20. That implies a very large gap. The key question is how comfortable you are with the long term assumptions behind it. Look into how the SWS DCF model arrives at its fair value. Simply Wall St performs a discounted cash flow (DCF) on every stock in the world every day (check out Dyne Therapeutics for example). We show the entire calculation in full. You can track the result in your watchlist or portfolio and be alerted when this changes, or use our stock screener to discover 47 high quality undervalued stocks. If you save a screener we even alert you when new companies match - so you never miss a potential opportunity. Mixed messages in the numbers and valuation models can be confusing. If this update has sharpened your curiosity, take a moment to review the full picture for yourself and weigh the trade off between risk and potential upside by checking out 1 key reward and 3 important warning signs. Before you move on, give yourself a wider watchlist by checking a few focused stock lists that match different goals and risk levels. Target potential mispricings by reviewing 47 high quality undervalued stocks that pair quality fundamentals with what could be attractive entry points. Strengthen your income watchlist by scanning 14 dividend fortresses that combine higher yields with a focus on resilience. Aim for steadier rides by checking 73 resilient stocks with low risk scores that screen for more resilient balance sheets and lower overall risk scores. This article by Simply Wall St is general in nature. We provide commentary based on historical data and analyst forecasts only using an unbiased methodology and our articles are not intended to be financial advice. It does not constitute a recommendation to buy or sell any stock, and does not take account of your objectives, or your financial situation. We aim to bring you long-term focused analysis driven by fundamental data. Note that our analysis may not factor in the latest price-sensitive company announcements or qualitative material. Simply Wall St has no position in any stocks mentioned. Companies discussed in this article include DYN. Have feedback on this article? Concerned about the content? Get in touch with us directly. Alternatively, email [email protected]

- Planned submission for U.S. Accelerated Approval of z-rostudirsen on track for Q2 2026; potential launch in Q1 2027 - - Positive topline results reported from Phase 1/2 DELIVER trial of z-rostudirsen in exon 51 skip amenable Duchenne muscular dystrophy (DMD); additional long-term data to be presented at MDA - - Completion of enrollment in registrational expansion cohort of Phase 1/2 ACHIEVE trial of z-basivarsen in myotonic dystrophy type 1 (DM1) expected in Q2 2026; Phase 3 trial design to be presented at MDA - - Advancing four development candidates for the potential treatment of DMD amenable to skipping of exons 53, 45, 44, and 55 - - Year-end cash of $1.1 billion; reaffirming expected cash runway into Q1 2028 - WALTHAM, Mass., March 02, 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 reported financial results for the fourth quarter and full year 2025 and recent business highlights. “Dyne is entering a critical period of transformation as we advance programs from our clinically validated FORCE platform toward commercialization, with our first potential launch in DMD in less than 12 months, if Priority Review is granted and approval is received. The positive topline results we reported in December for z-rostudirsen further demonstrate the potential of the FORCE platform to safely and effectively deliver drug payloads broadly and deeply into targeted tissues, all with the goal of providing functional improvement to patients in urgent need of new therapies,” said John Cox, president and chief executive officer of Dyne. “In 2026, we are focused on disciplined execution across our two lead programs with the goal of delivering potential best-in-class therapies to patients as quickly as possible. We are actively preparing a submission for U.S. Accelerated Approval of z-rostudirsen, positioning us for a potential launch planned for the first quarter of next year. We have added seven new sites since September to the ACHIEVE trial of z-basivarsen in DM1, and we continue to accelerate patient screening and enrollment, which we believe will enable completion of enrollment in the second quarter. At the same time, we expect to initiate two field-defining Phase 3 trials in DMD and DM1, as we continue to advance and expand our differentiated pipeline based on the FORCE platform,” concluded Mr. Cox. Zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251) in DMD Positive topline results from Registrational Expansion Cohort (REC) of DELIVER trial In December 2025, Dyne reported that the REC (n=32) met its primary endpoint, demonstrating a statistically significant change from baseline in muscle content-adjusted dystrophin expression to 5.46% of normal at six months (p<0.0001), a 7-fold change from baseline. Improvement relative to placebo was observed across all six prespecified topline functional endpoints. Two of these measures, Time to Rise (TTR) Velocity and 10-Meter Walk/Run (10MWR) Velocity, both improved relative to placebo at six months with a nominal p<0.05, even though the trial was not powered to demonstrate statistical significance in any of the functional measures. 1 Lung function, the loss of which is a leading cause of mortality in DMD, as measured by Forced Vital Capacity Percent Predicted (FVC%p), was preserved at 6 months compared to a decline in placebo. In addition, positive long-term results from the DELIVER trial showed sustained functional improvement across the same six endpoints out to 24 months, for participants treated with z-rostudirsen in the 10 mg/kg Q4W cohort of the multiple ascending dose (MAD) portion of the trial who were dose escalated to 20 mg/kg Q4W in the open-label extension period. Z-rostudirsen continued to demonstrate a favorable safety profile, 2 and most related treatment emergent adverse events (TEAEs) were mild or moderate. These results, along with additional long-term data showing the potential preservation of cardiopulmonary function, will be presented at the 2026 Muscular Dystrophy Association (MDA) Clinical & Scientific Conference being held March 8-11, 2026, in Orlando, FL, and virtually. Key milestones for z-rostudirsen Dyne plans to submit a Biologics License Application (BLA) for U.S. Accelerated Approval in Q2 2026. Dyne remains on track to initiate a global confirmatory Phase 3 clinical trial of z-rostudirsen in Q2 2026. Dyne has aligned with the U.S. Food and Drug Administration (FDA) on the Phase 3 trial design and protocol. Dyne continues to expect a potential U.S. launch of z-rostudirsen in Q1 2027, 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-rostudirsen in patients with DMD who are amenable to exon 51 skipping. Zeleciment basivarsen (z-basivarsen, also known as DYNE-101) in DM1 Key milestones for z-basivarsen Dyne expects to complete enrollment of 60 participants in the ACHIEVE REC in Q2 2026. Data from this cohort are planned for Q1 2027 to support a potential BLA submission for U.S. Accelerated Approval in early Q3 2027. Dyne intends to use data from the REC and from the already enrolled patients in the MAD and ongoing long-term extension portions of the ACHIEVE trial to support a potential submission for Accelerated Approval in the U.S. Dyne expects a potential U.S. launch of z-basivarsen in Q1 2028, assuming FDA grants Priority Review. Dyne remains on track to initiate a global confirmatory Phase 3 clinical trial of z-basivarsen in March 2026. Dyne has aligned with the FDA on the Phase 3 trial design and protocol. The design of this Phase 3 trial will be presented at the 2026 MDA Clinical & Scientific Conference being held March 8-11, 2026, in Orlando, FL, and virtually. Dyne also continues to pursue approval pathways outside of the U.S. for z-basivarsen in DM1. Other Exons in DMD 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, into IND-enabling studies. These programs are designed to enable the production of near full-length dystrophin in patients with DMD amenable to skipping of exons 53, 45, 44, or 55 by utilizing the same FORCETM platform (Fab, linker, and payload chemistry) as z-rostudirsen. Fourth Quarter and Full Year 2025 Financial Results Cash position: Cash, cash equivalents and marketable securities were $1.1 billion as of December 31, 2025. The Company continues to expect that its cash, cash equivalents and marketable securities as of December 31, 2025, will be sufficient to fund its operations into the first quarter of 2028. Research and development (R&D) expenses: R&D expenses were $95.4 million and $81.8 million for the quarters ended December 31, 2025 and 2024, respectively. R&D expenses were $398.3 million and $281.4 million for the years ended December 31, 2025 and 2024, respectively. General and administrative (G&A) expenses: G&A expenses were $20.7 million and $15.3 million for the quarters ended December 31, 2025 and 2024, respectively. G&A expenses were $69.9 million and $62.5 million for the years ended December 31, 2025 and 2024, respectively. Net loss: Net loss for the quarter ended December 31, 2025 was $112.0 million, or $0.76 per basic and diluted share. This compares with a net loss of $89.5 million, or $0.88 per basic and diluted share, for the quarter ended December 31, 2024. Net loss for the year ended December 31, 2025 was $446.2 million, or $3.47 per basic and diluted share. This compares with a net loss of $317.4 million, or $3.37 per basic and diluted share, for the year ended December 31, 2024. About Dyne Therapeutics 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 a preclinical programs for facioscapulohumeral muscular dystrophy (FSHD) and Pompe disease. 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. Forward-Looking Statements 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 platform, the potential of zeleciment basivarsen (z-basivarsen, also known as DYNE-101), zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251), DYNE-253, DYNE-245, DYNE-244 and DYNE-255; the anticipated timelines for initiating additional clinical trials, reporting additional data from the ACHIEVE and DELIVER clinical trials, enrolling registrational cohorts, submitting applications for marketing approval and launching commercially; the availability of expedited approval pathways for z-basivarsen and z-rostudirsen; expectations regarding the potential timing of regulatory approval, commercial launch and the outcome of interactions with regulatory authorities; and the sufficiency of Dyne’s cash resources for the period anticipated, 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 clinical trials; uncertainties as to the availability and timing of results from clinical trials; uncertainties as to the timing of and Dyne’s ability to enroll patients in clinical trials; whether results from preclinical studies and data from clinical trials will be predictive of the final results of the clinical trials or other trials; whether data from clinical trials will support submission for regulatory approvals; 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 as to the regulatory approval process for Dyne’s product candidates; whether Dyne’s cash resources will be sufficient to fund its foreseeable and unforeseeable operating expenses, debt service obligations 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. Contacts: Investors Mia Tobias [email protected] 781-317-0353 Media Stacy Nartker [email protected] 781-317-1938

- Topline data from Registrational Expansion Cohort of DELIVER trial of zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251) in DMD on track for December 2025 to support potential submission for U.S. Accelerated Approval in Q2 2026 - - FDA recently granted Breakthrough Therapy Designation to z-rostudirsen for the treatment of patients with DMD amenable to exon 51 skipping - - U.S. sites activated in ACHIEVE trial of zeleciment basivarsen (z-basivarsen, also known as DYNE-101) in DM1; completion of enrollment now expected in early Q2 2026 - - Additional one-year clinical data from ACHIEVE trial demonstrating sustained functional improvement across multiple clinical measures recently presented at WMS - - Reaffirming expected cash runway into Q3 2027, beyond Dyne’s first planned commercial launch of z-rostudirsen in DMD and potential z-basivarsen BLA submission in DM1 - WALTHAM, Mass., Nov. 05, 2025 (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 reported financial results for the third quarter of 2025 and recent business highlights. “Our lead programs in DMD and DM1 have now each been granted Breakthrough Therapy Designation by the FDA and are advancing toward anticipated U.S. Accelerated Approval submissions, as we aim to further validate the potential of our FORCE platform to safely and effectively deliver multiple drug payloads broadly and deeply into muscle and the CNS. We believe z-rostudirsen has the potential to transform the lives of individuals living with DMD amenable to exon 51 skipping, and we are excited to share topline data in December,” said John Cox, president and chief executive officer of Dyne. “We continue to advance z-basivarsen toward a U.S. Accelerated Approval submission in DM1 and now anticipate full enrollment in the ongoing Registrational Expansion Cohort of our ACHIEVE trial in early Q2 2026. This is a change from previous guidance of Q4 2025, but, starting in September, we initiated a significant expansion of clinical trial sites for ACHIEVE, including the recent activation of the first sites in the U.S. We expect that the additional sites will enable full enrollment of the planned 60 participants on this timeline. Importantly, we believe that the progress we have made across both programs positions us to launch two potentially best-in-class medicines within roughly one year of each other, beginning with z-rostudirsen potentially in Q1 2027,” concluded Mr. Cox. Zeleciment basivarsen (z-basivarsen, also known as DYNE-101) in Myotonic Dystrophy Type 1 (DM1) First U.S. sites activated and enrolling in Registrational Expansion Cohort (REC) of ACHIEVE trial Dyne initiated the U.S. site activation process in June 2025 after submitting a revised protocol for the REC to the U.S. Food and Drug Administration (FDA) with video hand opening time (vHOT) as the primary endpoint; U.S. site activation began in September and U.S. patient enrollment and dosing was initiated in October. ACHIEVE REC enrollment of 60 participants expected to be completed in early Q2 2026 Dyne anticipates a potential BLA (Biologics License Application) submission for U.S. Accelerated Approval in early Q3 2027. Dyne intends to use data from the REC and from the already enrolled patients in the multiple ascending dose (MAD) and ongoing long-term extension portions of the ACHIEVE trial to support a potential submission for Accelerated Approval in the U.S. Dyne expects a potential U.S. launch of z-basivarsen in Q1 2028, assuming FDA grants Priority Review. Dyne remains on track to initiate a confirmatory Phase 3 clinical trial in Q1 2026. Dyne also continues to pursue approval pathways outside of the U.S. for z-basivarsen in DM1. Additional one-year clinical data demonstrating functional improvement across multiple measures In October 2025, Dyne presented additional one-year clinical data from the ACHIEVE trial of z-basivarsen at the 30th Annual International Congress of the World Muscle Society (WMS). These data demonstrated clinically meaningful functional improvement across multiple measures at the selected registrational dose of 6.8 mg/kg Q8W, including assessments of function and strength, as well as patient- and clinician-reported outcomes. Zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251) in Duchenne Muscular Dystrophy (DMD) “Z-rostudirsen has the potential to provide functional improvement for patients with DMD amenable to exon 51 skipping, with a favorable safety profile and the convenience of monthly dosing,” said Doug Kerr, M.D., Ph.D., chief medical officer of Dyne. “Prior data from DELIVER demonstrated that DMD patients treated with z-rostudirsen can achieve dystrophin levels well above those possible with currently approved therapies for exon 51, as well as unprecedented improvements across multiple functional outcomes. We look forward to reporting topline data next month from the Registrational Expansion Cohort of DELIVER – the first potentially registrational data emerging from Dyne’s FORCE platform. I expect this to be a validating milestone for our pipeline and platform, but I am even more excited for these data to form the basis of a potential submission for U.S. Accelerated Approval in the second quarter of next year.” DELIVER REC topline results expected in December 2025 Dyne completed enrollment of 32 patients in the REC of the DELIVER trial in March 2025 and expects to announce data for the 6-month primary analysis in December 2025. The primary endpoint of the REC is the change from baseline in dystrophin protein by Western blot at 6 months. Dyne expects these data, along with comprehensive data from the MAD portion of the DELIVER trial, including safety, to support a potential submission for U.S. Accelerated Approval. Dyne also plans to report data on secondary endpoints, including functional assessments, although the REC is not powered to demonstrate statistical significance on these endpoints. In August 2025, the FDA granted Breakthrough Therapy Designation to z-rostudirsen for the treatment of patients with DMD, amenable to exon 51 skipping. Z-rostudirsen remains on track for potential launch in Q1 2027 Dyne continues to anticipate a potential BLA submission for U.S. Accelerated Approval in Q2 2026. Dyne continues to expect a potential U.S. launch of z-rostudirsen in Q1 2027, assuming FDA grants Priority Review. 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. Third Quarter Financial Results “We believe we have sufficient funds to generate data from two registrational trials, submit two BLAs for U.S. Accelerated Approval, and launch our first commercial product,” said Erick Lucera, chief financial officer of Dyne. “We are on track with the buildout of a capital-efficient rare disease commercial organization, along with our CMC infrastructure. Our management team is in place to operate effectively and create long-term value for shareholders.” Cash position: Cash, cash equivalents and marketable securities were $791.9 million as of September 30, 2025. The Company continues to expect that its cash, cash equivalents and marketable securities as of September 30, 2025, will be sufficient to fund its operations into the third quarter of 2027. Research and development (R&D) expenses: R&D expenses were $97.2 million for the three months ended September 30, 2025 compared to $92.8 million for the three months ended September 30, 2024. General and administrative (G&A) expenses: G&A expenses were $16.7 million for the three months ended September 30, 2025 compared to $12.9 million for the three months ended September 30, 2024. Net loss: Net loss for the three months ended September 30, 2025 was $108.0 million, or $0.76 per basic and diluted share. This compares with a net loss of $97.1 million, or $0.96 per basic and diluted share, for the three months ended September 30, 2024. About Dyne Therapeutics Dyne Therapeutics is focused on discovering and advancing innovative life-transforming therapeutics for people living with genetically driven neuromuscular diseases. Leveraging the modularity of its FORCE™ platform, Dyne is developing targeted therapeutics that are designed to overcome limitations in delivery to muscle tissue and the central nervous system (CNS). Dyne has a broad pipeline for neuromuscular diseases, including clinical programs for myotonic dystrophy type 1 (DM1) and Duchenne muscular dystrophy (DMD) and preclinical programs for facioscapulohumeral muscular dystrophy (FSHD) and Pompe disease. For more information, please visit https://www.dyne-tx.com/, and follow us on X, LinkedIn and Facebook. Forward-Looking Statements 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 platform, the potential of zeleciment basivarsen (z-basivarsen, also known as DYNE-101) and zeleciment rostudirsen (z-rostudirsen, also known as DYNE-251); the anticipated timelines for reporting additional data from the ACHIEVE and DELIVER clinical trials, initiating and enrolling registrational cohorts, initiating additional clinical trials, submitting applications for marketing approval and commercial launches; the availability of expedited approval pathways for z-basivarsen and z-rostudirsen; expectations regarding the potential timing of regulatory approval, commercial launch and the outcome of interactions with regulatory authorities; and the sufficiency of Dyne’s cash resources for the period anticipated, 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 clinical trials; uncertainties as to the availability and timing of results from clinical trials; uncertainties as to the timing of and Dyne’s ability to enroll patients in clinical trials; whether results from preclinical studies and data from clinical trials will be predictive of the final results of the clinical trials or other trials; whether data from clinical trials will support submission for regulatory approvals; 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 as to the regulatory approval process for Dyne’s product candidates; whether Dyne’s cash resources will be sufficient to fund its foreseeable and unforeseeable operating expenses, debt service obligations 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. Contacts: Investors Mia Tobias [email protected] 781-317-0353 Media Stacy Nartker [email protected] 781-317-1938

- Expected cash runway extended into Q3 2027, beyond multiple potential inflection points including Dyne’s first planned commercial launch in early 2027 - - Registrational Expansion Cohort of DELIVER Trial of DYNE-251 in DMD fully enrolled to support potential submission for U.S. Accelerated Approval in early 2026 - - Registrational Expansion Cohort of ACHIEVE Trial of DYNE-101 in DM1 ongoing to support potential submission for U.S. Accelerated Approval in late 2026 - WALTHAM, Mass., July 28, 2025 (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 reported financial results for the second quarter of 2025 and recent business highlights. “This quarter we made significant progress on our clinical and regulatory plans for our DM1 and DMD investigational therapies, as we advance both programs toward potential U.S. Accelerated Approval submissions in 2026 and possible commercial launches in 2027,” said John Cox, president and chief executive officer of Dyne. “We also strengthened our balance sheet, extending our cash runway into the third quarter of 2027 and believe we are well funded to achieve multiple value-creating milestones including two data readouts in DM1 and DMD, two potential U.S. Accelerated Approval submissions in those indications, and the potential launch of DYNE-251 in DMD in the U.S.” DYNE-101 in Myotonic Dystrophy Type 1 (DM1) In June 2025, Dyne announced that the U.S. Food and Drug Administration (FDA) has granted Breakthrough Therapy Designation to DYNE-101 for the treatment of DM1. Additionally, Dyne submitted a revised protocol to the FDA for the Registrational Expansion Cohort of the ACHIEVE trial with video hand opening time (vHOT) as the primary endpoint, to serve as an intermediate clinical endpoint for U.S. Accelerated Approval. Dyne also reported new positive long-term data from adult DM1 patients enrolled in the randomized, placebo-controlled multiple ascending dose (MAD) portion of the DYNE-101 ACHIEVE trial, including data from the 6.8 mg/kg Q8W cohort (n=6) at up to 12 months. Dyne plans to complete enrollment of 60 patients in the Registrational Expansion Cohort of the ACHIEVE trial in Q4 2025. Data from this cohort are planned for mid-2026 to support a potential U.S. Accelerated Approval Biologics License Application (BLA) submission in late 2026. Dyne plans to initiate a confirmatory Phase 3 clinical trial in Q1 2026. Dyne also continues to pursue approval pathways outside of the U.S. for DYNE-101 in DM1. DYNE-251 in Duchenne Muscular Dystrophy (DMD) Dyne has completed enrollment of 32 patients in the Registrational Expansion Cohort of the DELIVER trial. Data from this cohort are planned for late 2025. Dyne anticipates a potential BLA submission for U.S. Accelerated Approval in early 2026. Dyne also continues to pursue approval pathways outside of the U.S. for DYNE-251 in patients with DMD who are amenable to exon 51 skipping. DYNE-302 in Facioscapulohumeral Muscular Dystrophy (FSHD) In June 2025, Dyne presented new preclinical data demonstrating the potential of DYNE-302 to achieve functional improvement in FSHD at the 32nd Annual FSHD Society’s International Research Congress. Financing Updates In June 2025, Dyne entered into a $275 million non-dilutive senior secured term loan facility with Hercules Capital, Inc. The loan facility consists of five tranches, including an initial term loan of $100 million funded at closing, and three additional term loan tranches totaling up to $115 million, which can be drawn at Dyne’s option subject to achievement of specified clinical, regulatory and commercial milestones. A final term loan tranche of up to $60 million is available, subject to Hercules’ approval. In July 2025, Dyne completed an underwritten public offering of 27,878,788 shares of its common stock at a public offering price of $8.25 per share. The gross proceeds from the offering before deducting underwriting discounts and commissions and offering expenses payable by Dyne were approximately $230 million. Cash Runway Dyne expects that its existing cash, cash equivalents and marketable securities, including the net proceeds from the July 2025 public offering and initial term loan tranche from Hercules Capital, will be sufficient to fund its operating expenses, debt service obligations, and capital expenditure requirements into the third quarter of 2027. Based on the company’s current plans and anticipated timelines, Dyne estimates that these funds would be sufficient to enable the company to: Obtain data from the registrational expansion cohorts of the ACHIEVE and DELIVER clinical trials; Submit BLAs to the FDA for DYNE-251 in DMD and DYNE-101 in DM1 using the Accelerated Approval pathway; and Commercially launch DYNE-251 in the U.S. if approved by the FDA. Second Quarter Financial Results Cash position: Cash, cash equivalents and marketable securities were $683.9 million as of June 30, 2025. In July 2025, the Company completed an underwritten public offering of 27,878,788 shares of its common stock for estimated net proceeds of approximately $215.2 million. The Company expects that its cash, cash equivalents and marketable securities as of June 30, 2025, together with the net proceeds from the July 2025 underwritten public offering, will be sufficient to fund its operations into the third quarter of 2027. Research and development (R&D) expenses: R&D expenses were $99.2 million for the three months ended June 30, 2025 compared to $62.3 million for the three months ended June 30, 2024. General and administrative (G&A) expenses: G&A expenses were $16.6 million for the three months ended June 30, 2025 compared to $9.7 million for the three months ended June 30, 2024. Net loss: Net loss for the three months ended June 30, 2025 was $110.9 million, or $0.97 per basic and diluted share. This compares with a net loss of $65.1 million, or $0.70 per basic and diluted share, for the three months ended June 30, 2024. About Dyne Therapeutics 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 myotonic dystrophy type 1 (DM1) and Duchenne muscular dystrophy (DMD), and preclinical programs for facioscapulohumeral muscular dystrophy (FSHD) and Pompe disease. 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. Forward-Looking Statements 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 platform, the potential of DYNE-101 and DYNE-251; the anticipated timelines for reporting additional data from the ACHIEVE and DELIVER clinical trials, initiating and enrolling registrational cohorts, initiating additional clinical trials, submitting applications for marketing approval and commercial launches; the availability of expedited approval pathways for DYNE-101 and DYNE-251; expectations regarding the timing and outcome of interactions with regulatory authorities; and the sufficiency of Dyne’s cash resources for the period anticipated, 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,” 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; uncertainties as to the timing of and Dyne’s ability to enroll patients in clinical trials; whether results from preclinical studies and data from clinical trials will be predictive of the final results of the clinical trials or other trials; whether data from clinical trials will support submission for regulatory approvals; 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 as to the regulatory approval process for Dyne’s product candidates; whether Dyne’s cash resources will be sufficient to fund its foreseeable and unforeseeable operating expenses, debt service obligations 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. Contacts: Investors Mia Tobias [email protected] 781-317-0353 Media Stacy Nartker [email protected] 781-317-1938

- FDA (CDER) Type C meeting held in May 2025 for DYNE-101 in DM1 and Dyne plans to provide a regulatory update following receipt of meeting minutes - - Registrational Expansion Cohort of ACHIEVE Trial of DYNE-101 in DM1 initiated to support potential submission for U.S. Accelerated Approval in H1 2026 - - Registrational Expansion Cohort of DELIVER Trial of DYNE-251 in DMD fully enrolled to support potential submission for U.S. Accelerated Approval in early 2026 - WALTHAM, Mass., May 08, 2025 (GLOBE NEWSWIRE) -- Dyne Therapeutics, Inc. (Nasdaq: DYN), a clinical-stage company focused on advancing life-transforming therapeutics for people living with genetically driven neuromuscular diseases, today reported financial results for the first quarter of 2025 and recent business highlights. “Our two lead programs continue to demonstrate compelling and favorable data, including evidence of functional improvement across multiple measures in DM1 and DMD. We are urgently advancing both programs toward potential U.S. Accelerated Approval submissions in 2026 and possible commercial launches in 2027,” said John Cox, president and chief executive officer of Dyne. “I am also thrilled to welcome Erick, Vik and Ron to the Dyne leadership team, which now includes a new role for Oxana as chief innovation officer. Together, our team has the proven experience and capabilities to efficiently drive the business, deliver therapies that bring functional improvement and create significant shareholder value.” DYNE-101 in DM1 Dyne participated in a Type C meeting with the Center for Drug Evaluation and Research (CDER) at the Food and Drug Administration (FDA) in May 2025 and discussed the path to regulatory approval, including U.S. Accelerated Approval, for DYNE-101 in DM1. Dyne participated in a Type C meeting with the Center for Drug Evaluation and Research (CDER) at the Food and Drug Administration (FDA) in May 2025 and discussed the path to regulatory approval, including U.S. Accelerated Approval, for DYNE-101 in DM1. Dyne has initiated a global placebo-controlled Registrational Expansion Cohort in the ACHIEVE trial that will include up to 48 participants with full enrollment planned for mid-2025. Data from this cohort is planned for H1 2026 to support a potential U.S. Accelerated Approval Biologics License Application (BLA) submission in H1 2026. Dyne has initiated a global placebo-controlled Registrational Expansion Cohort in the ACHIEVE trial that will include up to 48 participants with full enrollment planned for mid-2025. Data from this cohort is planned for H1 2026 to support a potential U.S. Accelerated Approval Biologics License Application (BLA) submission in H1 2026. Data from this cohort is planned for H1 2026 to support a potential U.S. Accelerated Approval Biologics License Application (BLA) submission in H1 2026. Dyne also continues to advance preparations for a Phase 3 trial with the goal of initiating the trial in 2025. Dyne also continues to advance preparations for a Phase 3 trial with the goal of initiating the trial in 2025. Management plans to provide a regulatory update for DYNE-101 following receipt of final FDA meeting minutes and the company’s incorporation of regulatory feedback. Management plans to provide a regulatory update for DYNE-101 following receipt of final FDA meeting minutes and the company’s incorporation of regulatory feedback. Dyne is also pursuing expedited approval pathways globally for DYNE-101. Dyne is also pursuing expedited approval pathways globally for DYNE-101. DYNE-251 in DMD In April 2025, the European Commission granted Orphan Drug Designation to DYNE-251 for the treatment of patients with DMD who are amenable to exon 51 skipping. In April 2025, the European Commission granted Orphan Drug Designation to DYNE-251 for the treatment of patients with DMD who are amenable to exon 51 skipping. Dyne has fully enrolled the Registrational Expansion Cohort of 32 patients as part of the DELIVER trial. Data from this cohort are planned for late 2025. Dyne has fully enrolled the Registrational Expansion Cohort of 32 patients as part of the DELIVER trial. Data from this cohort are planned for late 2025. Dyne anticipates a potential BLA submission for U.S. Accelerated Approval in early 2026. Dyne anticipates a potential BLA submission for U.S. Accelerated Approval in early 2026. Dyne continues to pursue expedited approval pathways globally for DYNE-251 in patients with DMD who are amenable to exon 51 skipping. Dyne continues to pursue expedited approval pathways globally for DYNE-251 in patients with DMD who are amenable to exon 51 skipping. New Leadership Appointments Dyne recently strengthened its leadership team in preparation for potential regulatory filings, approvals and commercial launches of DYNE-101 and DYNE-251: Erick Lucera, chief financial officer (CFO), brings more than thirty years of capital markets, operational and investment experience in the life science industry to his leadership role at Dyne. Erick Lucera, chief financial officer (CFO), brings more than thirty years of capital markets, operational and investment experience in the life science industry to his leadership role at Dyne. Vikram (Vik) Ranade, PhD, chief business officer (CBO) is driving business development, corporate strategy and strategic partnerships to support the company’s late-stage clinical and commercialization plans. Vikram (Vik) Ranade, PhD, chief business officer (CBO) is driving business development, corporate strategy and strategic partnerships to support the company’s late-stage clinical and commercialization plans. Ranjan (Ron) Batra, PhD, chief scientific officer (CSO) is leading the company’s research strategy, pipeline development and activities supporting clinical development. Ranjan (Ron) Batra, PhD, chief scientific officer (CSO) is leading the company’s research strategy, pipeline development and activities supporting clinical development. Oxana Beskrovnaya, PhD, the company’s previous CSO, has taken on a new role as our chief innovation officer (CIO) and is developing and advancing Dyne’s comprehensive strategy to maximize the value of its FORCE™ platform across multiple tissues, therapeutic areas and indications. Oxana Beskrovnaya, PhD, the company’s previous CSO, has taken on a new role as our chief innovation officer (CIO) and is developing and advancing Dyne’s comprehensive strategy to maximize the value of its FORCE™ platform across multiple tissues, therapeutic areas and indications. First Quarter Financial Results Cash position: Cash, cash equivalents and marketable securities were $677.5 million as of March 31, 2025. The company expects that its cash, cash equivalents and marketable securities as of March 31, 2025 will be sufficient to fund its operations at least into the second half of 2026. Research and development (R&D) expenses: R&D expenses were $106.4 million for the quarter ended March 31, 2025 compared to $44.5 million for the quarter ended March 31, 2024. General and administrative (G&A) expenses: G&A expenses were $15.9 million for the quarter ended March 31, 2025 compared to $24.6 million for the quarter ended March 31, 2024. Net loss: Net loss for the quarter ended March 31, 2025 was $115.4 million, or $1.05 per basic and diluted share. This compares with a net loss of $65.6 million, or $0.81 per basic and diluted share, for the quarter ended March 31, 2024. About Dyne Therapeutics Dyne Therapeutics is discovering and advancing innovative life-transforming therapeutics for people living with genetically driven neuromuscular diseases. Leveraging the modularity of its FORCE™ platform, Dyne is developing targeted therapeutics that deliver to muscle and the central nervous system (CNS). Dyne has a broad pipeline for neuromuscular diseases, including clinical programs for myotonic dystrophy type 1 (DM1) and Duchenne muscular dystrophy (DMD) and preclinical programs for facioscapulohumeral muscular dystrophy (FSHD) and Pompe disease. For more information, please visit https://www.dyne-tx.com/, and follow us on X, LinkedIn and Facebook. Forward-Looking Statements 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 platform, the potential of DYNE-101 and DYNE-251, the anticipated timelines for reporting additional data from the ACHIEVE and DELIVER clinical trials, initiating and enrolling registrational cohorts, initiating additional clinical trials, submitting applications for marketing approval and commercial launches, the availability of expedited approval pathways for DYNE-101 and DYNE-251, expectations regarding the timing and outcome of interactions with regulatory authorities, and the sufficiency of Dyne’s cash resources for the period anticipated, 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,” 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 data from clinical trials will be predictive of the final results of the clinical trials or other trials; whether data from clinical trials will support submission for regulatory approvals; 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 as to the regulatory approval process for Dyne’s product candidates; 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. Dyne Therapeutics, Inc. Condensed Consolidated Statement of Operations (in thousands, except share and per share data) Three Months Ended March 31, 2025 2024 Operating expenses: Research and development $ 106,447 $ 44,539 General and administrative 15,925 24,618 Total operating expenses 122,372 69,157 Loss from operations (122,372 ) (69,157 ) Other (expense) income, net 7,011 3,508 Net loss $ (115,361 ) $ (65,649 ) Net loss per share, basic and diluted $ (1.05 ) $ (0.81 ) Weighted average common shares outstanding, basic and diluted 109,911,628 81,043,741 March 31, December 31, 2025 2024 Assets Cash, cash equivalents and marketable securities $ 677,492 $ 642,268 Other assets 43,582 48,966 Total assets $ 721,074 $ 691,234 Liabilities and Stockholders’ Equity Liabilities 52,101 61,396 Stockholders' equity 668,973 629,838 Total liabilities and stockholders' equity $ 721,074 $ 691,234 Contacts: Investors Mia Tobias [email protected] 781-317-0353 Media Stacy Nartker [email protected] 781-317-1938