Elamipretide: what the studies show

The approved population

Elamipretide, also called SS-31 or MTP-131, is marketed as Forzinity. FDA granted accelerated approval in September 2025 to improve muscle strength in adults and children with Barth syndrome who weigh at least 30 kg. Approval does not extend to general fatigue or longevity.

Randomized and open-label results

TAZPOWER enrolled 12 males with genetically confirmed Barth syndrome. During the randomized crossover phase, each treatment period lasted 12 weeks. Elamipretide did not outperform placebo on walking distance or the disease-specific fatigue score.

Knee-extensor strength improved later in the open-label extension. There was no concurrent placebo group during that period. The extension followed the same participants and is not an independent replication. FDA used the strength finding as an intermediate clinical endpoint for accelerated approval.

Product and confirmatory evidence

The approved product is a daily subcutaneous injection. Injection-site reactions were common in the trial. Research products called SS-31 or MTP-131 do not share Forzinity's approval. A confirmatory trial must verify clinical benefit. Whether the observed strength change leads to durable improvements in everyday function remains unresolved.