Stealth BioTherapeutics Cuts Workforce Following FDA Rejection, Pursues Accelerated Approval for Barth Syndrome Therapy

Stealth BioTherapeutics, a Needham, Massachusetts-based biotech company focusing on therapies for mitochondrial dysfunction, has announced significant changes following the U.S. Food and Drug Administration's (FDA) rejection of its new drug application (NDA) for elamipretide, a potential treatment for Barth syndrome. Despite this setback, the company remains optimistic about the drug's future and is pursuing an accelerated approval pathway.

Workforce Reduction and Resource Reallocation

In response to the FDA's decision, Stealth BioTherapeutics has implemented a 30% reduction in its workforce. This move, announced on May 29, 2025, is aimed at conserving resources to fund a potential NDA resubmission for elamipretide. While the exact number of affected employees was not disclosed, estimates based on the company's LinkedIn profile suggest that approximately 28 staff members may have been impacted by these cuts.

FDA Rejection and Potential Accelerated Approval Pathway

Despite rejecting Stealth's initial NDA for elamipretide, submitted in January 2024, the FDA has identified a potential accelerated approval pathway for the drug. This development comes after years of discussions between Stealth and the FDA, including a 2024 Cardiovascular and Renal Drugs Advisory Committee meeting that concluded elamipretide is effective for treating Barth syndrome.

The FDA has agreed to consider knee extensor muscle strength as a potential intermediate clinical endpoint to support accelerated approval. Stealth's January 2024 NDA included data showing that knee extensor muscle strength improved by over 45% in a Phase II clinical trial and was significantly correlated with improvements on a six-minute walk test.

Challenges in Elamipretide's Development

Stealth BioTherapeutics CEO Reenie McCarthy acknowledged the complex development path of elamipretide, which has involved four different FDA review divisions since 2019. The ultra-rare nature of Barth syndrome, FDA reservations regarding data from the SPIBA-001 Phase 3 natural history control study, and previous refusals to consider an accelerated approval pathway have all contributed to the challenges faced during the review process.

The company also experienced a setback when the FDA missed the Prescription Drug User Fee Act (PDUFA) target decision date for elamipretide on April 29, 2025. Despite these obstacles, Stealth remains committed to pursuing approval for elamipretide, particularly in light of increasing emergency access requests for critically ill infants from medical experts worldwide.