Understand the source comparison
SS-31 Clinical Trials 2026: Comparison of Trial Outcomes and Endpoints
The table below summarizes the primary SS-31 clinical trials active or reported in 2026, comparing study design, endpoints, and results across indications. This comparison clarifies where elamipretide has shown signal vs where results have been inconclusive or
No winner is assigned.
This page preserves a source comparison for education. It does not add a rating, recommendation or clinical judgment.
- The table below summarizes the primary SS-31 clinical trials active or reported in 2026, comparing study design, endpoints, and results across indications. This comparison clarifies where elamipretide has shown signal vs where results have been inconclusive or negative.
- MMPOWER-3
- Primary mitochondrial myopathy
- III
- Change in 6-minute walk distance (6MWD) at 24 weeks
- +10.5 meters vs placebo (not statistically significant, p=0.09)
- Trend toward improvement but missed primary endpoint. Insufficient power or heterogeneous patient population may explain null result
- TAZPOWER
- Barth syndrome
- Change in 6MWD at 12 weeks
- +13.3 meters vs placebo (p=0.04, statistically significant but below MCID threshold)
- Statistically significant but clinically modest. FDA declined approval in 2023, resubmission under discussion in 2026
- PROGRESS-HFpEF
- Heart failure with preserved ejection fraction
- II
- Change in peak VO₂ at 4 weeks
- No significant change vs placebo
- Null result. Either wrong endpoint, wrong dosing duration, or mitochondrial dysfunction not rate-limiting in HFpEF pathophysiology
- EMBRACE STEMI
- Ischemia-reperfusion injury during PCI
- Infarct size (cardiac MRI) at 5 days
- Numerical reduction (−8% relative to placebo, p=0.12)
- Trend toward benefit but underpowered. Acute dosing model may require higher dose or earlier administration
- ReCLAIM-2
- Dry age-related macular degeneration (geographic atrophy)
- Change in geographic atrophy growth rate at 12 months
- Trial ongoing, results expected Q4 2026
- Exploratory endpoint. Retinal pigment epithelium mitochondrial dysfunction is well established, but whether SS-31 penetrates retina at therapeutic levels is unproven
- The pattern across trials: statistically significant results (TAZPOWER) have not met clinically meaningful thresholds, and trials targeting complex multifactorial diseases (HFpEF, STEMI) have shown biological trends without statistical significance. The rare disease trials (MMPOWER, TAZPOWER) face the inherent challenge of small sample sizes and heterogeneous genotypes. Patients with different mitochondrial DNA mutations respond differently because the severity and tissue distribution of mitochondrial dysfunction vary. A patient with a mutation affecting Complex I in skeletal muscle may respond differently than one with Complex IV dysfunction in cardiac and neural tissue.
- The FDA's rejection of elamipretide for Barth syndrome despite positive p-value reflects regulatory expectation that rare disease therapies must demonstrate functional benefit large enough to justify risk, cost, and patient burden. A 13-meter improvement in 6MWD, while statistically different from placebo, does not necessarily translate to improved independence, reduced hospitalizations, or extended survival, the outcomes that matter for quality of life and healthcare systems. Stealth BioTherapeutics has indicated it will submit additional long-term open-label extension data and patient-reported outcome measures in 2026 to address the magnitude-of-effect concern.