Peptide LibrarySix-minute walk distance and fatigue
Low certaintyPatient-important outcome · 4 studies · 284 participants
The evidence conflicts
The certainty of the evidence is low, so the true effect may differ substantially from what these studies suggest. The largest and longest trial found that elamipretide did not improve walking distance or fatigue compared with placebo in adults with primary mitochondrial myopathy. Two small, short trials and later subgroup analyses hinted at benefit, but these results are less reliable. Whether elamipretide helps people with specific genetic forms of the disease is still being tested.
What the research measured: 6MWT findings differed by trial. In MMPOWER-3 (218 randomized, 24 weeks), the between-group difference in 6MWT change was -3.2 m (95% CI -18.7 to 12.3; p=0.69) and in PMMSA total fatigue -0.07 (95% CI -0.1 to 0.26; p=0.37), both not significant. In a 30-participant 4-week crossover trial, the 6MWT difference was 19.8 m favoring elamipretide (95% CI -2.8 to 42.5; p=0.0833), with nominally significant reductions in PMMSA fatigue (p=0.0006) and Neuro-QoL fatigue (p=0.0115). In a 36-participant 5-day dose-escalation trial, the top dose group changed 64.5 m vs 20.4 m with placebo (p=0.053), with a dose-dependent trend (p=0.014). Post hoc MMPOWER-3 subgroups (mtDNA replisome, CPEO) suggested benefit only in genotype-restricted subsets.
What remains unknown: Whether benefit exists in specific genotypes, such as mtDNA replisome disorders, needs confirmation in prospectively designed trials. Effects beyond 24 weeks are unknown. Full trial reports with arm sizes, attrition and multiplicity handling are not available. Safety data are only narrative, and no reported serious events in small short trials does not establish long-term safety.
Reviewers’ note: Starting at high for randomized evidence, the rating was lowered one level for risk of bias and one level for inconsistency, giving low certainty. The post hoc MMPOWER-3 analysis reuses participants from the main trial and was not counted as independent evidence.
How the certainty was judged
| Domain | Judgment | Why |
|---|---|---|
| Starting level | High (randomized evidence) | |
| Risk of bias | Serious (rated down one level) | All four records are available only as abstracts, so allocation, blinding, attrition and analysis populations cannot be checked. RoB2 judgments are some concerns for the main MMPOWER-3 outcomes and high for the dose-escalation 6MWT result and the post hoc genotype subgroups. In the crossover trial, frequent injection site reactions could have unblinded participants for self-reported fatigue. |
| Inconsistency | Serious (rated down one level) | The largest and longest trial (MMPOWER-3, 24 weeks) found no difference in 6MWT distance or fatigue. The smaller, shorter trials reported favorable 6MWT trends and nominally significant fatigue reductions. The positive post hoc findings are confined to genotype subsets defined after the primary endpoint failed. |
| Indirectness | Not serious | All trials enrolled adults with genetically confirmed primary mitochondrial myopathy, compared elamipretide with placebo, and measured 6MWT and fatigue directly. The small trials' very short treatment periods (5 days, 4 weeks) limit their relevance to sustained benefit, but the main trial ran 24 weeks. |
| Imprecision | Not serious | The pivotal 218-participant trial gave reasonably narrow intervals for 6MWT (-18.7 to 12.3 m) and fatigue (-0.1 to 0.26). The small trials were imprecise, with intervals crossing zero or no interval reported, but they add little weight relative to the main trial. |
| Publication bias | Not detected | Both null and positive trials from the same development program are published. Selective reporting within trials (secondary endpoints without data, post hoc subgroups) is handled under risk of bias rather than here. |
Included studies
- Genotype-specific effects of elamipretide in patients with primary mitochondrial myopathy: a post hoc analysis of the MMPOWER-3 trial. (Randomized controlled trial, 218 participants)
- Efficacy and Safety of Elamipretide in Individuals With Primary Mitochondrial Myopathy: The MMPOWER-3 Randomized Clinical Trial. (Randomized controlled trial, 218 participants)
- Randomized dose-escalation trial of elamipretide in adults with primary mitochondrial myopathy. (Randomized controlled trial, 36 participants)
- A randomized crossover trial of elamipretide in adults with primary mitochondrial myopathy. (Randomized controlled trial, 30 participants)
Version 1 · published November 8, 2026 · evidence through November 8, 2026 · research snapshot 2026.1.1 · methodology ev-1 · GRADE (handbook, 2013) · Automated assessment by AI (claude-opus-5-5 and claude-sonnet-5-5), not reviewed by a person.