STEALTH BIOTHERAPEUTICS RESUBMITS NEW DRUG APPLICATION FOR ELAMIPRETIDE FOR THE TREATMENT OF BARTH SYNDROME

, /PRNewswire/ -- Stealth BioTherapeutics, a clinical-stage biotechnology company focused on the discovery, development and commercialization of novel therapies for diseases involving mitochondrial dysfunction, today announced the resubmission of a New Drug Application (NDA) to the U.S. Food and Drug Administration (FDA) for Barth syndrome. As directed by the FDA in its May 2025 complete response (CR) and subsequent correspondence, the resubmission contains no new clinical efficacy data, a minor safety update, and confirmation that previously cited manufacturing deficiencies were resolved by FDA, which determined in July that the facility remains in compliance. At FDA's request, the resubmission also contains additional post-marketing commitments regarding a proposed post-marketing trial to confirm the clinical benefit of elamipretide for the treatment of Barth syndrome. "We appreciate FDA's recent recognition of the seriousness of Barth syndrome and the unmet need for potential therapies, and its commitment to complete its review of our NDA resubmission as expeditiously as possible," said Reenie McCarthy, Chief Executive Officer of Stealth. "With FDA's confirmation that the manufacturing observations cited in the CR have been resolved, and the progress we have made to align on post-marketing trial design, we believe that all concerns raised by the FDA have been addressed." In May 2025, the FDA issued a CR recommending resubmission of Stealth's NDA for accelerated approval on the basis of improvements in knee extensor muscle strength, an intermediate clinical endpoint. Knee extensor muscle strength improved by >45% in the TAZPOWER Phase 2 open-label clinical trial and was significantly correlated with gains in the six-minute walk test, an FDA-recognized indicator of clinical benefit. The CR also cited CGMP observations from a May 2025 surveillance inspection of a third-party manufacturing facility. In July 2025, the FDA confirmed that the facility remains in full CGMP compliance with no corrective action required and advised Stealth to include this confirmation in its NDA resubmission, which now also incorporates the agreed-upon Phase 4 protocol, previous feasibility data, and proposed timelines. FDA policy is to classify resubmissions as Class 1 (two month review) or Class 2 (six month review) upon receipt and preliminary review. Although FDA signaled a likely Class 2 review, Stealth has requested Class 1 because, with manufacturing concerns resolved, no new inspection should be required. This is the third NDA submission containing the TAZPOWER muscle strength data and comes 19-months after the prior priority review NDA submission. The company urges the FDA to act with urgency, consistent with its stated commitment to expedite review of and an early action on the resubmission. If approved, this would be the first marketing authorization for elamipretide, a first-in-class mitochondrial targeted therapeutic. Elamipretide is also in development for primary mitochondrial myopathy and dry age-related macular degeneration. About Barth SyndromeBarth syndrome is an ultra-rare genetic condition characterized by exercise intolerance, muscle weakness, debilitating fatigue, heart failure, recurrent infections, and delayed growth. The disease is associated with reduced life expectancy, with 85% of early deaths occurring by age 5. Barth syndrome occurs almost exclusively in males and is estimated to affect one in 1,000,000 males worldwide or around 150 individuals in the United States. There are currently no FDA- or EMA-approved therapies for patients with Barth syndrome. Elamipretide has Orphan Drug, Fast Track and Rare Pediatric Designation from the FDA and Orphan Drug Designation from the EMA for the treatment of Barth syndrome. The Barth syndrome NDA was granted priority review. About Stealth BioTherapeuticsStealth BioTherapeutics is a clinical-stage biotechnology company focused on the discovery, development, and commercialization of novel therapies for diseases involving mitochondrial dysfunction. Mitochondria, found in nearly every cell in the body, are the body's main source of energy production and are critical for normal organ function. Dysfunctional mitochondria characterize a number of rare genetic diseases and are involved in many common age-related diseases, typically involving organ systems with high energy demands such as the heart, the eye, and the brain. The Company believes its lead product candidate, elamipretide, has the potential to treat rare diseases including Barth syndrome and primary mitochondrial myopathy and common age-related diseases including dry age-related macular degeneration. The Company is also evaluating a topical ophthalmic formulation of bevemipretide, its second-generation clinical-stage candidate, for dry age-related macular degeneration. The Company has a deep pipeline of novel compounds under evaluation for rare neurological and cardiac disease indications following promising preclinical data. Media ContactAnna StallmannAscent Strategic Communications[email protected] Investor Relations ContactAustin MurtaghPrecision AQ[email protected] SOURCE Stealth BioTherapeutics Inc. WANT YOUR COMPANY'S NEWS FEATURED ON PRNEWSWIRE.COM? 440k+ Newsrooms & Influencers 9k+ Digital Media Outlets 270k+ Journalists Opted In

STEALTH BIOTHERAPEUTICS RESUBMITS NEW DRUG APPLICATION FOR ELAMIPRETIDE FOR THE TREATMENT OF BARTH SYNDROME

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