Stealth BioTherapeutics, a clinical-stage biotechnology company focused on the discovery, development and commercialisation of novel therapies for diseases involving mitochondrial dysfunction, announced that the US Food and Drug Administration (FDA) has accepted for review the resubmission of the New Drug Application (NDA) for elamipretide for the treatment of Barth syndrome.

While the FDA considers the resubmission a complete, class 2 response with a six-month user fee goal date of February 15, 2026, the agency has advised the Company that its planned goal date is September 26, 2025, the company said in a statement.

Reenie McCarthy, Chief Executive Officer, Stealth BioTherapeutics said, “We appreciate the FDA's timely acceptance and commitment to expeditiously review our NDA resubmission. We are sharing this news in the spirit of transparency with families living with Barth syndrome and their many champions, and with gratitude to the FDA for recognising the urgency of the unmet need.”

Stealth resubmitted its NDA to the FDA on August 15, 2025, following its receipt of a May 2025 complete response (CR). As recommended by the FDA in the CR, the resubmission seeks accelerated approval of elamipretide on the basis of improvements in knee extensor muscle strength, an intermediate clinical endpoint, which improved by >45 percent in the TAZPOWER Phase 2 open-label clinical trial. Stealth's resubmission included a protocol for a post-marketing trial to confirm clinical benefit.

If approved, this would be the first marketing authorisation for elamipretide, a first-in-class mitochondria-targeted therapeutic. Elamipretide is also in development for primary mitochondrial myopathy and dry age-related macular degeneration, the company stated.