SS-31
/ Synthetic mitochondria-targeted tetrapeptide that binds cardiolipin in the inner mitochondrial membraneALIAS · Elamipretide · MTP-131 · Bendavia
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Extensive mechanistic literature on mitochondrial bioenergetics. However, the Phase 3 MMPOWER-3 trial in primary mitochondrial myopathy was negative on primary endpoints. Development continues in other indications.
SS-31 (elamipretide) is a synthetic mitochondria-targeted tetrapeptide that binds cardiolipin in the inner mitochondrial membrane. It is proposed to stabilize cristae architecture, improve electron transport chain function, and reduce reactive oxygen species production. Pre-clinical work by the Szeto laboratory provides the mechanistic foundation.
Development history includes Phase 2 and Phase 3 trials in primary mitochondrial myopathy, heart failure, and age-related macular degeneration. The pivotal MMPOWER-3 Phase 3 trial (Karaa 2023, Neurology) did NOT meet its primary endpoints of 6-minute walk distance or PMMSA fatigue score, although a subgroup with nuclear-DNA variants showed suggestive benefit. Development continues in other indications.
Phase 2 and Phase 3 trials reported generally acceptable tolerability with injection-site reactions and headache as most common adverse events. No serious unexpected safety signals emerged.
Regulatory status
- FDA status:
- Not FDA-approved
- Compounding:
- Not eligible for compounding (approved, not in shortage)
Social-media enthusiasm for SS-31 as a mitochondrial fix-all routinely omits the negative MMPOWER-3 Phase 3 result in primary mitochondrial myopathy. Compelling mechanistic data does not equal demonstrated clinical efficacy; the pivotal trial should be cited alongside any mechanistic claim.