Trial of Elamipretide in Participants With Primary Mitochondrial Myopathy (MMPOWER-3) — VialBase Research
Trial Summary
MMPOWER-3 was a pivotal Phase 3 trial of elamipretide (SS-31, Bendavia, MTP-131) for primary mitochondrial myopathy. Elamipretide is a mitochondria-targeting tetrapeptide that concentrates in the inner mitochondrial membrane and stabilizes cardiolipin, a critical phospholipid for electron transport chain function.
Design
- Type: Randomized, double-blind, placebo-controlled, multicenter
- Population: 218 adults with genetically confirmed primary mitochondrial myopathy
- Arms: Elamipretide 40 mg SC daily vs. placebo
- Duration: 24 weeks
- Primary endpoint: Change from baseline in 6-minute walk test distance
- Secondary endpoints: Patient-reported fatigue (PMMSA), quality of life
Key Outcomes
- Trial terminated — failed to meet primary endpoint
- No statistically significant improvement in 6MWT distance vs. placebo
- Some trends in patient-reported outcomes but not statistically significant
- High placebo response observed
- The heterogeneity of mitochondrial disease (many different genetic causes) complicated efficacy assessment
- Stealth BioTherapeutics subsequently pivoted focus to Barth syndrome (more homogeneous population)
Significance for Peptide Research
The MMPOWER-3 failure illustrates the challenge of treating genetically heterogeneous mitochondrial diseases with a single agent. However, the elamipretide mechanism (cardiolipin stabilization) remains biologically sound. The pivot to Barth syndrome (a single-gene cardiolipin deficiency) was scientifically rational. Lessons learned: patient selection and disease homogeneity are critical for mitochondrial peptide trials. Relevant to elamipretide development and mitochondria-targeting peptides.
See Also
- Related compound: SS-31