SS-31 (Elamipretide): Approved Use, Side Effects, Evidence

Elamipretide, also known as SS-31, MTP-131 and Bendavia, is an aromatic-cationic tetrapeptide that concentrates at the inner mitochondrial membrane. Its approved product, FORZINITY, is a condition-specific prescription medicine for Barth syndrome, a rare genetic mitochondrial disorder. It is not a general mitochondrial supplement.

Elamipretide binds cardiolipin, a lipid that helps organize the folds of the inner membrane (cristae) and the respiratory-chain proteins. Binding is proposed to stabilize membrane structure and electron transfer, reduce electron leak, and support energy production under mitochondrial stress. Its localization is described as direct lipid association rather than accumulation driven by membrane voltage.

Laboratory studies report downstream effects on reactive oxygen species, cristae structure and mitochondrial quality control. These findings are relevant to genetically defined mitochondrial disease. They do not establish a general anti-aging effect in healthy people.

Human trial: MMPOWER-3, a Phase III randomized, double-blind, placebo-controlled trial in 218 adults with primary mitochondrial myopathy, did not improve the six-minute walk test or fatigue scores compared with placebo. An earlier, shorter randomized crossover trial in the same condition, MMPOWER-2, missed statistical significance on its primary walking endpoint, while patient-reported fatigue measures favored elamipretide. The authors called it an efficacy signal.

Human trial: in Barth syndrome, a randomized, placebo-controlled crossover trial in 12 patients was followed by a long open-label extension. According to the FORZINITY label, the drug was not superior to placebo on the randomized trial's primary endpoints, walking distance and fatigue, and gains in knee extensor muscle strength were not seen during the randomized phase. Strength gains appeared only during the extension, which had no concurrent control group and included authors employed by the manufacturer. The FDA accelerated approval rests on that intermediate strength endpoint, and continued approval may depend on a confirmatory trial.

Human trial: a randomized, vehicle-controlled Phase II trial of an eye-drop form in 12 people with Leber hereditary optic neuropathy did not meet its primary visual-acuity endpoint, though the authors described some post hoc and open-label findings as encouraging.

The FORZINITY label lists reactions where the drug is given as the most common adverse reactions. Its warnings cover hypersensitivity, including serious allergic reactions that needed emergency care and that can appear from minutes to months after starting, and benzyl alcohol toxicity in newborns, since the product contains benzyl alcohol and is not approved for neonates. It is contraindicated in people with serious hypersensitivity to elamipretide or its ingredients. The label carries no boxed warning.

In MMPOWER-3, most adverse events were mild to moderate. The Barth syndrome safety record comes from about a dozen patients, so rare and long-term risks are not well defined. Products sold online outside a pharmacy are not the approved medicine, and Health Canada warns they may be mislabelled or contaminated.

In the United States, elamipretide is approved only as FORZINITY for Barth syndrome under accelerated approval. Health Canada's Drug Product Database lists no product containing it, and Health Canada's April 2026 advisory names SS-31 among seized unauthorized peptide drugs. It is not named on the 2026 WADA Prohibited List.