Elamipretide (SS-31)
Mechanism, regulatory status, and an honest, tiered evidence map.
What it is
Class: Cardiolipin-binding tetrapeptide
Also known as: SS-31, MTP-131, FORZINITY
Relationship to mitochondrial health: Elamipretide is a cell-permeable tetrapeptide that binds cardiolipin at the inner mitochondrial membrane, where it is intended to stabilise cristae and respiratory-chain organisation. It is a rare-disease drug, not an aging therapy.
Regulatory status
FDA accelerated approval in September 2025 (as FORZINITY) to improve muscle strength in patients with Barth syndrome (an ultra-rare genetic mitochondrial disease) weighing ≥30 kg. This is a rare-disease approval — NOT an anti-aging or longevity approval. Continued approval may be contingent on confirmatory trials.
Mechanism
Cardiolipin-targeting peptide; the aging-adjacent primary-mitochondrial-myopathy Phase 3 (MMPOWER-3) failed its primary endpoints, while the Barth-syndrome program earned accelerated approval on a muscle-strength endpoint. See /cardiolipin.
Evidence — Human (Phase 3, disease population)
| Species / population | Adults with genetically confirmed primary mitochondrial myopathy (MMPOWER-3, Karaa 2023). |
| Exposure, route, schedule | Subcutaneous elamipretide daily for 24 weeks. |
| Comparator / duration | Placebo-controlled, randomized, double-blind. |
| Endpoint / numeric result | Did NOT meet its co-primary endpoints (6-minute walk distance and a mitochondrial-myopathy symptom assessment). |
| What it did NOT establish | A failed Phase 3 in a disease population; not an aging trial and not evidence of any healthy-aging benefit. |
Evidence — Regulatory (Barth syndrome)
| Species / population | Patients with Barth syndrome (ultra-rare cardiolipin/tafazzin disorder), ≥30 kg. |
| Exposure, route, schedule | Elamipretide (FORZINITY), FDA accelerated approval September 2025. |
| Comparator / duration | Accelerated approval based on an intermediate endpoint (knee-extensor muscle strength) from the open-label TAZPOWER program. |
| Endpoint / numeric result | First FDA-approved therapy for Barth syndrome and first mitochondria-targeted therapeutic; approved to improve muscle strength. |
| What it did NOT establish | A rare-disease approval on a surrogate strength endpoint. It is NOT an anti-aging approval and says nothing about healthy human lifespan. |
Negative or null findings
- MMPOWER-3 Phase 3 failed both co-primary endpoints in primary mitochondrial myopathy.
- The Barth-syndrome accelerated approval is on an intermediate (muscle-strength) endpoint and is disease-specific; confirmatory clinical-benefit trials may be required.