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RQS Scoring Log

SS-31

Longevity & Cellular Aging· Observational· Scored June 2026· View compound profile →
50 /100
Limited Evidence
7 dimensions · 100 points total · Methodology by PeptideClear
Evidence grade note: Phase II/III trials exist but primary endpoints were not met
SS-31 (elamipretide) has advanced further through clinical development than most compounds in the Longevity & Cellular Aging category — reaching Phase II/III RCTs in primary mitochondrial myopathy (MMPOWER-3), heart failure (PROGRESS-HF), and Barth syndrome (TAZPOWER). However, MMPOWER-3 (the pivotal Phase 3 trial) did not meet its primary endpoints and was terminated early for futility in the double-blind phase. TAZPOWER showed improvement in the 6-minute walk test after 48 weeks, but was an open-label extension. The evidence grade is scored as Observational rather than Human RCT because the available completed RCTs did not demonstrate statistically significant primary endpoint efficacy, even though the trials themselves were RCT in design.
Dimension Breakdown
DimensionScoring NotesScore
Study Design
Multiple Phase II and one Phase III RCT completed. MMPOWER-3 was a rigorous 24-week, randomized, double-blind, placebo-controlled trial enrolling 218 participants across 27 international sites — gold-standard design. PROGRESS-HF and TAZPOWER are Phase II. The design quality is genuinely high; the outcomes are the limitation. Scored at Phase I/II tier to reflect that the best-powered trial (MMPOWER-3) failed its primary endpoints, and no completed Phase III has demonstrated efficacy.
10 / 25
Sample Size
MMPOWER-3 enrolled 218 participants — the largest SS-31 human trial to date. PROGRESS-HF enrolled ~47. TAZPOWER enrolled 12 (Barth syndrome is an ultra-rare disease). Cumulative human exposure across completed trials is in the low hundreds. Meaningful Phase II/III-level sample in MMPOWER-3; smaller in other indications.
8 / 20
Replication
Multiple trials across multiple independent sites and research groups — Harvard/MGH, Cleveland Clinic, Nationwide Children's, and international academic centers contributed to MMPOWER-3. TAZPOWER and PROGRESS-HF were conducted by separate principal investigator groups. Meaningful independent replication exists at the trial level, though all sponsored by Stealth BioTherapeutics. Separate academic-led investigator-initiated studies (e.g., FRDA trial at NCT05168774) add independent replication signal.
10 / 20
Journal Impact Factor
MMPOWER-3 results published in Neurology (IF ~9). TAZPOWER in Genetics in Medicine (IF ~8). Foundational cardiolipin/SS-31 mechanism papers in PNAS (IF ~11) and JASN (Journal of the American Society of Nephrology, IF ~13). Solid journal placement across the evidence base — this is one of the better-published compounds in the Longevity category.
12 / 15
Funding Independence
Stealth BioTherapeutics (formerly Stealth Peptides) funded the major clinical trials. The company filed for bankruptcy in 2022 after MMPOWER-3 failed — trials were pre-registered and conducted to pharmaceutical standards, but funding was entirely industry (no NIH or independent academic primary funding for Phase II/III trials). Foundational Szeto laboratory work at Weill Cornell was NIH-funded. Mixed picture — industry for clinical, academic for mechanistic. Scored to reflect industry dominance in the clinical evidence.
4 / 10
Population Diversity
MMPOWER-3 was 94% White, mean age 45.6, 64% women — conducted across 7 countries but ethnically narrow by modern trial standards. Barth syndrome trials by definition enroll a very narrow rare-disease pediatric/young adult population. Limited diversity score reflects this honestly.
1 / 5
Researcher h-Index
Hazel Szeto (Weill Cornell) is the discoverer of the SS-peptide class with h-Index ~50+ in mitochondrial pharmacology. Vincenzo Carelli (University of Bologna), lead MMPOWER-3 investigator, has h-Index ~50+ in mitochondrial disease research. Top-tier researchers across the program.
5 / 5