Mitochondria-Targeted Peptide
SS-31 (Elamipretide)
Also known as: Elamipretide, Bendavia, Forzinity
A synthetic mitochondria-targeted tetrapeptide that received its first FDA approval in September 2025 (as Forzinity, for Barth syndrome) — the first approved mitochondria-targeted therapeutic of its kind, after a long clinical development history under the research name SS-31.
A note on regulatory status — this one changed recently
SS-31 stands out among the peptides on this site: on September 19, 2025, the FDA granted accelerated approval to elamipretide HCl (brand name Forzinity) for Barth syndrome, an ultra-rare genetic mitochondrial disease — the first-ever approved mitochondria-targeted therapeutic. If you've encountered "SS-31" described elsewhere as a purely experimental research peptide, that description is now out of date for at least this specific indication.
Overview
SS-31/elamipretide is a synthetic tetrapeptide engineered to selectively target and concentrate in mitochondria, where it's proposed to stabilize cardiolipin, a lipid in the inner mitochondrial membrane essential to normal mitochondrial energy production.
Proposed Mechanism of Action
By binding and stabilizing cardiolipin, elamipretide is proposed to improve mitochondrial bioenergetic efficiency, reduce harmful reactive oxygen species production, and prevent a specific trigger of programmed cell death (cytochrome c release) — mechanistically distinct from most peptides on this site, which typically act via cell-surface receptors.
Research Context
The cited trial studied elamipretide specifically in Barth syndrome, a genetic disorder that impairs cardiolipin metabolism and causes cardiac and skeletal muscle dysfunction. It's worth reading the full result honestly: the initial randomized crossover phase did not meet its primary endpoints, but the longer open-label extension (36 weeks) showed statistically significant improvement in both walking distance and symptom scores — a pattern regulators ultimately found persuasive enough, combined with other trial data (including the TAZPOWER extension study), to support accelerated approval.
Limitations of the Current Evidence
- The approval is narrow: specifically for Barth syndrome, in patients weighing at least 30 kg, based on an intermediate endpoint (muscle strength) under the FDA's accelerated approval pathway — not a general approval for mitochondrial support or anti-aging use.
- The cited trial is small (12 subjects) with an initially negative randomized phase; the positive result is from the longer open-label extension, which lacks the same blinding/placebo control as the earlier phase.
- Other studied indications (heart failure, kidney injury, general aging) remain investigational and have not reached approval.
Research-Setting Dosing (as reported in literature)
| Route | Range (as reported) | Frequency | Notes |
|---|---|---|---|
| Subcutaneous injection | 40–40 mg | Once daily | Thompson et al. (2021); 12-week treatment arms in a crossover design, followed by an open-label extension. In the initial crossover phase, neither primary endpoint (6-minute walk test, symptom scale) reached statistical significance; at 36 weeks in the open-label extension, both showed significant improvement. |
Figures above are extracted directly from the cited preclinical/research literature. They describe what researchers administered to study subjects (frequently animal models) — they are not human dosing recommendations and are not medical advice.
Cited Studies
A phase 2/3 randomized clinical trial followed by an open-label extension to evaluate the effectiveness of elamipretide in Barth syndrome, a genetic disorder of mitochondrial cardiolipin metabolism
Thompson WR, Hornby B, Manuel R, Bradley E, Laux J, Carr J, Vernon HJ · Genetics in Medicine · 2021
Human clinical trial (Phase 2/3, randomized, double-blind, placebo-controlled crossover, 12 subjects, with open-label extension)View source →
Last updated August 1, 2026