Elamipretide (SS-31)

What it is

Elamipretide is a small, water-soluble aromatic-cationic tetrapeptide originally known in research as SS-31 and by the development code MTP-131 S4. It is designed to concentrate inside mitochondria, where it binds the inner-membrane phospholipid cardiolipin and is thought to help stabilize mitochondrial membrane structure and support energy production S4. It was developed by Stealth BioTherapeutics, which studied it across a range of conditions marked by mitochondrial dysfunction S3.

Marketed as

In its approved form, elamipretide is sold under the brand name Forzinity as a prescription therapy for Barth syndrome S1. Independently of that approved product, the same molecule circulates on the gray market under its research name SS-31, where it is offered as a "research chemical" rather than an approved medicine S4. Material sold this way is not FDA-approved, not quality-assured, and its purity or identity is not guaranteed, and claims that it treats aging, boosts athletic performance, or cures disease in these unapproved settings are not established fact S4.

Regulatory status (US)

On September 19, 2025 the FDA granted accelerated approval to elamipretide (Forzinity) for Barth syndrome in patients weighing at least 30 kg, making it the first FDA-approved therapy for a mitochondrial disease S1. The approval was based on a surrogate endpoint — improved strength of the muscle that straightens the leg at the knee — which the agency considered reasonably likely to predict clinical benefit S1. As a condition of accelerated approval, the manufacturer must conduct a confirmatory post-approval randomized, placebo-controlled trial, and the approval can be withdrawn if benefit is not verified S1. The path was not straightforward: an FDA advisory committee voted 10–6 in favor in October 2024, the agency declined to approve the application in May 2025, and Stealth resubmitted before the eventual accelerated approval S3.

Around the world

Public regulatory activity for elamipretide has centered on the US FDA accelerated approval for Barth syndrome S1. Availability, approval, or reimbursement in other jurisdictions is not established here and should be checked against the relevant national regulator S3.

Evidence

The scientific rationale is mechanistic: elamipretide targets cardiolipin in the inner mitochondrial membrane, which is central to mitochondrial structure and energy generation S4. Beyond Barth syndrome, elamipretide has been studied in primary mitochondrial myopathy and other primary mitochondrial diseases, including registry-listed clinical trials in patients with mitochondrial disease from nuclear-DNA mutations S5. These broader uses remain investigational, and the Barth syndrome approval itself rests on a surrogate muscle-strength measure rather than confirmed long-term clinical outcomes S1.

Anti-doping

Elamipretide is a peptide affecting mitochondrial energy metabolism, which places it in a category athletes should scrutinize. It does not appear to be explicitly named on the WADA Prohibited List as reviewed here, but an approved or investigational peptide can still be captured under a listed category or the prohibited-substance framework, so competitive athletes should verify its current status directly with WADA or their anti-doping authority before assuming it is permitted S6.

Safety

In the approval materials, the most frequently reported adverse events were mild-to-moderate injection-site reactions, though more serious reactions have been reported S1. Because accelerated approval relied on a surrogate endpoint, the full long-term risk–benefit picture is still being established through the required confirmatory trial S1. Gray-market SS-31 carries additional, distinct risks: unverified identity, purity, and dosing, and the absence of medical oversight or FDA quality controls S4. Anyone considering elamipretide should evaluate a legitimate provider and pathway with a qualified clinician rather than an unregulated source S4.

What's changing

The near-term watch items are whether the confirmatory post-approval trial verifies clinical benefit — a requirement of accelerated approval that, if unmet, could lead to withdrawal S1 — and whether elamipretide advances toward approval in broader mitochondrial indications such as primary mitochondrial myopathy on the strength of ongoing studies S5. Because the regulatory picture has moved repeatedly and recently, the specific decision state should be re-verified before this page is republished S1S3.