After a May 2025 rejection, the FDA accepted Stealth BioTherapeutics’ resubmitted NDA for elamipretide and told the company to expect a decision around September 26, 2025. The formal review clock runs to February 15, 2026, but the agency plans to move faster because of the unmet need.
At a glance
- What happened: The FDA accepted Stealth’s resubmission for elamipretide on August 21. The agency signaled a planned target decision date of September 26, 2025.
- Official clock: The filing is a Class 2 response, which normally allows up to six months. The official user fee goal date is February 15, 2026.
- Why this is urgent: Stealth has tight finances and said a full six-month timeline could jeopardize operations and patient access through the expanded access program.
- Who is affected: People with Barth syndrome, an ultra-rare genetic condition that mostly affects males and can lead to heart failure, severe fatigue, and early mortality. About 150 individuals are estimated to be affected in the United States.
What changed since the rejection
- In May 2025, the FDA issued a Complete Response Letter (CRL).
- The CRL said the data did not support regular approval, and the surrogate endpoint data were not enough for accelerated approval.
- The CRL also flagged good manufacturing practice (GMP) inspection findings at a third-party facility. Those issues must be resolved before approval.
- The FDA outlined a potential path to accelerated approval if Stealth focused on an intermediate clinical endpoint: improvement in knee extensor muscle strength.
What Stealth submitted now
- Stealth resubmitted the NDA on August 15, 2025, addressing the FDA’s feedback.
- The company highlighted results from the TAZPOWER Phase II open-label study, which reported a greater than 45 percent improvement in knee extensor strength.
- The FDA accepted the filing and, despite the Class 2 clock, told Stealth to plan for a September 26, 2025 decision.
Why this matters
- For patients: There are no approved therapies for Barth syndrome in the United States. Faster review could preserve access for patients currently receiving elamipretide through expanded access.
- For caregivers and clinicians: A potential accelerated approval would likely include post-marketing requirements to confirm benefit. Planning for data collection and real-world outcomes will be important.
- For the company: Stealth reduced its workforce by 30 percent after the CRL to fund the resubmission and keep patient access going. A faster decision helps manage runway risk.
Plain-English definitions
- Class 2 review: The FDA’s standard six-month review timeline for a resubmission.
- User fee goal date: The latest date by which the FDA aims to complete its review under the official clock.
- Accelerated approval: Approval based on a meaningful intermediate or surrogate endpoint that is reasonably likely to predict clinical benefit, with confirmatory studies required after approval.
- Open-label study: A study where both researchers and participants know which treatment is given.
- Knee extensors: Thigh muscles that straighten the leg. Stronger knee extensors can indicate improved muscle strength and function.
Key numbers and timeline
- >45 percent improvement in knee extensor strength in TAZPOWER (Phase II, open-label).
- 30 percent workforce reduction after the May 2025 CRL to fund resubmission and maintain access.
- Aug 15, 2025: Resubmission filed.
- Aug 21, 2025: FDA acceptance.
- Sep 26, 2025: Planned FDA decision date signaled to the company.
- Feb 15, 2026: Official user fee goal date under the Class 2 clock.
Executive voice
“We appreciate the FDA’s timely acceptance and commitment to expeditiously review our NDA resubmission,” said CEO Reenie McCarthy, noting both the urgency for families and the importance of a timely review given the company’s financing constraints.
What to watch next
- Whether the FDA grants accelerated approval and what post-marketing studies are required.
- Confirmation that GMP issues at the third-party site are fully resolved.
- Stealth’s near-term financing plans and the continuity of its expanded access program.
Additional context
Elamipretide targets the cardiolipin deficit that is central to Barth syndrome biology. The product is also in Phase III trials for dry age-related macular degeneration and primary mitochondrial myopathy.
Navigating accelerated approval and rare-disease communications requires precision. Connect with CI Health to align regulatory content, medical affairs enablement, and stakeholder communications.
Source: Citeline Scrip coverage via Insights: Speedy FDA review could save Stealth from sinking
