SS-31: From mitochondrial research peptide to an FDA-approved drug

SS-31, also published as elamipretide, MTP-131, and Bendavia, is a tetrapeptide that associates with cardiolipin on the inner mitochondrial membrane. That mechanism came out of careful work, not marketing. Hazel Szeto’s SS-peptide series, and later Stealth BioTherapeutics’ clinical program, spent years putting it through heart-failure, mitochondrial-myopathy, and Barth-syndrome trials.

What September 19, 2025 changed

FDA granted accelerated approval to Forzinity (elamipretide) injection as the first treatment for Barth syndrome in patients weighing at least 30 kilograms. Accelerated approval is a real approval with a real obligation: a confirmatory randomized trial to show that the muscle-strength changes mean something a patient can feel. The labeled product is a specific formulation, a specific manufacturer, a specific indication, and a specific route. In that program it is administered subcutaneously once daily. Injection-site reactions were the common adverse effect.

Related sequences can share a research history while living in very different product worlds.

A lyophilized research lot labeled SS-31 is a chemical for laboratory work. It is a different object from Forzinity: it has not been through the Barth-syndrome clinical program, and it is not interchangeable with the approved product. The useful habit is to keep the names straight — research material on one side, labeled drug on the other — so the approval story stays attached to the product that earned it.