Elamipretide is a synthetic peptide that spent years circulating in research and longevity circles under its laboratory name, SS-31. Unlike most peptides discussed on this site, it has crossed a meaningful regulatory threshold: the FDA has approved it, under the brand name Forzinity, for one specific rare disease.
What It Is
Elamipretide was developed by Stealth BioTherapeutics as a small peptide designed to concentrate inside mitochondria, the structures inside cells responsible for producing energy. It binds to cardiolipin, a lipid found in the inner mitochondrial membrane that is essential to normal mitochondrial function, and appears in laboratory and animal research to help stabilize mitochondrial structure and reduce oxidative stress.
Regulatory Status: A Narrow but Real Approval
On September 19, 2025, the FDA granted accelerated approval to elamipretide, marketed as Forzinity, as the first treatment for Barth syndrome, a rare and serious X-linked mitochondrial disease that causes severe heart failure, fatigue, and exercise intolerance, primarily in males. The approval was based on improvement in a specific muscle-strength measure (knee-extension strength) that the FDA considers reasonably likely to predict a real clinical benefit, such as improved standing and walking ability. This is an accelerated approval, meaning Stealth BioTherapeutics is required to complete a confirmatory randomized, placebo-controlled trial to verify that clinical benefit. Forzinity also received priority review and rare pediatric disease designation, and is approved specifically for patients weighing at least 30 kg, administered as a once-daily subcutaneous injection.
It's worth being precise about what this approval covers. Forzinity is approved for Barth syndrome, and only Barth syndrome, through an accelerated pathway that is still pending final confirmation. It is not a general approval for "mitochondrial health," anti-aging, or athletic performance, whatever the underlying molecule's marketing history might suggest.
What Else Has Been Studied
Beyond Barth syndrome, elamipretide has also been investigated in larger trials for other conditions, including primary mitochondrial myopathy and dry age-related macular degeneration. Results in those programs have been mixed, and neither indication currently carries FDA approval. Broader claims circulating about elamipretide's effects on general energy, aging, or athletic recovery rest mostly on preclinical and animal research, or on data collected for narrower, specific disease populations, not on confirmed large-scale human evidence for those broader uses.
Why the Same Peptide Shows Up in Enforcement Actions
Because elamipretide (SS-31) has a long research history under its non-brand name, it continues to be sold by research-chemical vendors marketed toward mitochondrial function or general wellness, entirely separate from Stealth BioTherapeutics' approved Forzinity product and its associated prescribing information, quality controls, and physician oversight. A peptide sold this way, regardless of what name it's marketed under, hasn't gone through the same manufacturing and quality standards as the approved drug, even when the underlying molecule is nominally the same.
Safety Considerations
In the Barth syndrome clinical program, the most common side effects were mild-to-moderate injection site reactions, though more serious reactions have also been reported. This safety profile applies specifically to the approved daily-injection regimen studied in that trial population; it does not establish a safety profile for other doses, formulations, or unapproved uses.
The Bottom Line
Elamipretide is a genuine example of a peptide that moved from research compound to an FDA-approved therapy, but only for a specific rare disease and through a conditional approval pathway. Anyone encountering "SS-31" marketed for unrelated purposes should understand that product is not the same regulated, physician-prescribed medicine as Forzinity, and should talk to a doctor about legitimate treatment options for any condition they're trying to address.