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SS-31 (elamipretide) gets first FDA approval — Barth syndrome.

Stealth BioTherapeutics' Forzinity approved at 40mg/d. The first cardiolipin-targeting peptide to clear the FDA. Dry AMD is the bigger prize.

Apr 18, 20262 min#ss-31#fda#rare-disease

The FDA approved Forzinity (elamipretide / SS-31) at 40 mg daily for Barth syndrome — a rare X-linked cardiomyopathy affecting ~250 people in the US.

Why it matters:

SS-31 is the first cardiolipin-targeting to clear the FDA. The mechanism (mitochondrial inner-membrane stabilization) was novel enough that the agency had been cautious. The Barth indication is small but the approval establishes regulatory precedent for the broader pipeline.

What we're watching:

the dry AMD program (ReCLAIM-2 missed primary but hit secondary EZ-zone preservation), the Friedreich's ataxia program, and whether off-label use spikes now that the molecule has a real label.

We've updated the SS-31 page with the new approval status. Trial-dose ratio-check is now active for SS-31 (was previously gated as phase-2-only).