Claimed effect · SS-31 (elamipretide)

Does SS-31 (elamipretide) help with barth syndrome?

C
Grade C — weak human evidence1 crossover RCT + open-label extension (n=12) · effect size: small
Short answerWeak human evidence. 1 crossover RCT + open-label extension (n=12): enough to be interesting, not enough to count on. Where an effect is seen it is a small effect. TAZPOWER: the 12-week randomised crossover missed both primary endpoints; improvements in walk distance and symptom score emerged only in the open-label extension at 36 weeks. This extension is the basis of the 2025 accelerated approval.

What the studies show

TAZPOWER: the 12-week randomised crossover missed both primary endpoints; improvements in walk distance and symptom score emerged only in the open-label extension at 36 weeks. This extension is the basis of the 2025 accelerated approval.

“In part 1 neither primary endpoint was met. At 36 weeks in part 2, there were significant improvements in 6MWT (+95.9 m, p = 0.024) and BTHS-SA (-2.1 points, p = 0.031).”

Verbatim, from the abstractThompson WR, et al. A phase 2/3 randomized clinical trial followed by an open-label extension to evaluate elamipretide in Barth syndrome (TAZPOWER). Genet Med, 2021;23:471–478

A few small or poorly-controlled human studies. Enough to be interesting; not enough to count on. Most of what gets called “clinically proven” online lives here.

  1. 1
    Thompson WR, et al. A phase 2/3 randomized clinical trial followed by an open-label extension to evaluate elamipretide in Barth syndrome (TAZPOWER).Genet Med, 2021;23:471–47812 subjects; part-1 crossover negative, part-2 extension positive at 36 weeks.

In context

SS-31, developed as elamipretide, is a four-amino-acid peptide that concentrates in mitochondria and binds cardiolipin, a lipid of the inner membrane. After a decade of trials it was approved in the United States in September 2025 for Barth syndrome, an ultra-rare genetic disease — on the strength of an open-label extension, since its randomised crossover missed both primary endpoints. Larger randomised trials in primary mitochondrial myopathy and in heart failure were negative. It is a genuine, narrowly approved medicine, not a general 'mitochondrial' or anti-ageing treatment.

SS-31 (elamipretide) is approved (rx, us; barth syndrome only). Legal status differs by country — see the regulation section or the jurisdiction pages.

Questions

Is SS-31 (elamipretide) proven to help with barth syndrome?
No. The human evidence is weak (1 crossover RCT + open-label extension (n=12)); LYO grades it C.
What studies are behind the grade?
TAZPOWER: the 12-week randomised crossover missed both primary endpoints; improvements in walk distance and symptom score emerged only in the open-label extension at 36 weeks. This extension is the basis of the 2025 accelerated approval.
Is SS-31 (elamipretide) approved for this?
SS-31 (elamipretide) is an approved medicine (Approved (Rx, US; Barth syndrome only)); whether this particular outcome is a licensed indication is stated on the compound page's regulation section.

Other outcomes for SS-31 (elamipretide)

Written and maintained by LYO Research — how pages are written and checked. Reviewed 3 September 2026. Grades count human evidence only; see how LYO grades. Not medical advice. Correct this page →