After years of setbacks and uncertainty, Stealth BioTherapeutics has achieved a historic breakthrough with FDA approval of Forzinity (elamipretide), the first treatment for Barth syndrome, an ultrarare, life-limiting genetic disorder. The decision announced September 19, 2025 and reported by Fiercepharma.com, comes via the FDA’s accelerated approval pathway, marking a transformative moment for patients and families affected by this devastating X-linked disease.
Barth Syndrome: An Urgent Unmet Need
Barth syndrome is a rare inherited disorder that primarily weakens the heart (cardiomyopathy) and skeletal muscles, resulting in severe fatigue, growth delays, and high mortality, especially in early childhood. With most patients not surviving past their 40s and no previous treatments available, the approval of Forzinity fills a critical gap in care.
A Tumultuous Road to Approval
Forzinity’s journey to approval was anything but smooth. The FDA initially rejected the drug after it failed to meet its primary endpoint in a six-minute walk test during clinical trials. Additional delays, split advisory committee opinions, and a protracted review process followed. Public outcry—including letters from Congress and advocacy from physicians—highlighted the urgency of the situation, especially as patients faced withdrawal from the experimental drug due to Stealth’s financial struggles.
Evidence and Accelerated Approval
Ultimately, the FDA granted accelerated approval based on evidence that Forzinity improved knee extensor muscle strength, an important intermediate indicator of physical function. This improvement is expected to translate to meaningful clinical benefits, such as enhanced ability to stand and walk. The approval is currently limited to patients weighing at least 60 pounds.
However, the FDA’s endorsement comes with a requirement: Stealth must conduct a rigorous, post-approval randomized, double-blind, placebo-controlled trial to confirm that gains in muscle strength lead to real-world improvements for patients. The agency emphasized that while current evidence is “reasonably likely to predict patient benefit,” further confirmation is essential.
A New Era for Rare Disease Treatment
Forzinity’s approval not only provides hope for those with Barth syndrome but also underscores the FDA’s commitment to supporting innovation in rare disease therapeutics. “The FDA remains committed to facilitating the development of effective and safe therapies for rare diseases,” said Dr. George Tidmarsh, director of the FDA’s Center for Drug Evaluation and Research.
Looking Forward
Forzinity’s approval is a milestone for Stealth BioTherapeutics, which faced existential challenges during the review process, including layoffs and financial strain. The decision is also a testament to the power of patient advocacy and the importance of flexible regulatory pathways for ultrarare diseases.
As Stealth embarks on post-approval trials, the Barth syndrome community finally has a reason for optimism and the possibility of improved quality—and length—of life.
