Elamipretide Hydrochloride

iStock, Tatyana Kim Stealth BioTherapeutics originally submitted elamipretide for approval in January 2024, only to receive a rejection in May of this year. In addition to accepting the biotech’s resubmission, the FDA has promised to take action on the candidate by Sept. 26. Stealth BioTherapeutics is taking another shot at getting its Barth syndrome therapy elamipretide approved, with the FDA accepting a resubmitted application and agreeing to a speedy September decision date just days after the new filing . Elamipretide has been resubmitted to treat the ultra-rare genetic disorder that causes muscle weakness, fatigue and heart failure. About 85% of patients with Barth die by the age of five. Stealth originally submitted the application in January 2024 after years of discussion with the FDA and an advisory committee meeting that ultimately supported the approval of elamipretide. But in May, after a 16.5 month review, Stealth announced that the FDA had rejected the drug . The biotech at the time did not fully state the FDA’s concerns, noting some manufacturing issues. However, the Cardiovascular and Renal Drugs Advisory Committee in 2024 flagged the flawed nature of Stealth’s data that supported the drug and uncertainties regarding clinical efficacy. In rejecting the drug, the FDA left the door open for a resubmitted application under the accelerated review pathway. Stealth resubmitted that application on August 15, requesting the speedy review. The FDA has granted the accelerated review, promising to take action on elamipretide by Sept. 26, instead of Feb. 15, 2026, which would be the target date under a standard review application. The resubmission seeks approval of the drug based on improvements in knee extensor muscle strength. Stealth requested that this be the main endpoint for approval in the original application, which the FDA has agreed to. Knee extensor muscle strength is associated with improvements in a six-minute walk test. During Stealth’s Phase II TAZPOWER trial, which underpins the application, patients saw a greater than 45% improvement in the endpoint. The company has offered to conduct a post-marketing trial to confirm clinical benefit. Elamipretide is a mitochondria-targeted therapeutic that Stealth is also developing for primary mitochondrial myopathy and dry age-related macular degeneration.

NEEDHAM, MA, USA I August 18, 2025 I 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 Syndrome Barth 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 BioTherapeutics Stealth 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. SOURCE: Stealth BioTherapeutics