SS-31 is the research name for elamipretide, a peptide designed to act on mitochondria. The human trials are few and small. This article covers what they showed, why the one approval was granted, and what is not known about the research vial sold here.
What it is
Elamipretide is a tetrapeptide that binds cardiolipin, a lipid in the inner mitochondrial membrane. The aim is to stabilise the membrane structure and support energy production. This is a mechanism claim, and it has not by itself been shown to help people.
The approval
On 19 September 2025 the FDA granted accelerated approval to elamipretide, sold as Forzinity, to improve muscle strength in Barth syndrome, a very rare genetic disorder, in people weighing at least 30 kg. Accelerated approval rests on an intermediate measure that is expected to predict benefit, and it requires a confirmatory trial after approval.
The basis: TAZPOWER
The approval rests on TAZPOWER, a randomised, double-blind, placebo-controlled crossover trial in a small group of people with Barth syndrome. Its randomised part was small, and the primary endpoints were the six-minute walk and a fatigue score. The strength gain that FDA relied on was seen in the knee extensors.
MMPOWER-3: the miss
- Adults with primary mitochondrial myopathy, 218 in total, randomised 1:1 to elamipretide 40 mg daily under the skin or placebo for 24 weeks.
- Six-minute walk difference: -3.2 m (95% CI -18.7 to 12.3; p = 0.69).
- Total fatigue score difference: -0.07 (95% CI -0.10 to 0.26; p = 0.37).
- The drug was well tolerated, and most side effects were mild to moderate.
Later analyses
A post hoc analysis of MMPOWER-3 by genotype found a 6-minute walk improvement in a subgroup with nuclear DNA variants, and no difference in the mitochondrial DNA group. The authors used these results to design a further phase 3 trial. Post hoc subgroups generate questions; they do not show that the drug works in those people.
What is not known about the research vial
No published human study used the research vial sold here. Its dose, purity and long-term safety are not established by any trial we checked, and it is not the approved product.
What this does not say
- It does not show benefit for aging, general fatigue, muscle strength in healthy adults, or heart disease.
- It does not show benefit in primary mitochondrial myopathy; the main trial was negative.
- The Barth syndrome approval does not establish benefit in other conditions.
- Animal and cell studies in heart failure and other models are not proof of benefit in people.
How we use this
Our physicians read this evidence before recommending anything. The only approval is narrow and rests on a surrogate measure in a small group, and the mitochondrial myopathy trial was negative.
We do not present the research vial as the approved medicine, and we do not use the approval to support claims beyond Barth syndrome.
Explore weight loss treatmentsSources
- 1.Shirley M. Elamipretide: First Approval. Drugs, 2026
- 2.FDA press announcement: FDA grants accelerated approval to first treatment for Barth syndrome (Forzinity, elamipretide). U.S. Food and Drug Administration, 19 Sept 2025
- 3.Karaa A, Bertini E, Carelli V, et al. Efficacy and safety of elamipretide in individuals with primary mitochondrial myopathy: the MMPOWER-3 randomized clinical trial. Neurology, 2023
- 4.Karaa A, et al. Genotype-specific effects of elamipretide in patients with primary mitochondrial myopathy: a post hoc analysis of the MMPOWER-3 trial. Orphanet Journal of Rare Diseases, 2024
- 5.Van den Eynde J, Chinni B, Vernon H, et al. Identifying responders to elamipretide in Barth syndrome: hierarchical clustering for time series data. Orphanet Journal of Rare Diseases, 2023
- 6.Tung C, Varzideh F, Farroni E, et al. Elamipretide: a review of its structure, mechanism of action, and therapeutic potential. International Journal of Molecular Sciences, 2025