Elamipretide

The labelled product is Forzinity. FDA granted accelerated approval on 19 September 2025, NDA 215244, to improve muscle strength in adult and pediatric patients with Barth syndrome weighing at least 30 kg. Barth syndrome is X-linked; that is disease biology, not a class of peptides. Research-chemical SS-31 is not Forzinity. Approval does not travel to a similarly named research compound, and it does not make elamipretide a general mitochondrial supplement.

A mitochondria-targeted tetrapeptide that binds cardiolipin on the inner mitochondrial membrane. The labelled product is described as a mitochondrial cardiolipin binder that can change mitochondrial morphology and function. That mechanism is the same scaffold sold as research SS-31. The labelled use is not a property of the sequence.

TAZPOWER (Reid Thompson et al., Genet Med 2021, PMID 33077895) was a 12-person randomized crossover in Barth syndrome. The randomized period did not meet its primary endpoints (six-minute walk and a Barth symptom scale). The Forzinity label and the 19 September 2025 FDA notice base accelerated approval on later improvement in knee extensor muscle strength, an intermediate endpoint the agency treats as reasonably likely to predict benefit. A confirmatory trial is required. MMPOWER-3 (Karaa et al., Neurology 2023, PMID 37268435) randomized 218 people with primary mitochondrial myopathy. It missed both primary endpoints. The paper reports Class I evidence that elamipretide did not improve six-minute walk or fatigue at 24 weeks versus placebo. Other development programs have been mixed. That is why the grade stays Moderate.

Forzinity is the FDA-approved product. The labelled use is improvement of muscle strength in Barth syndrome in patients weighing at least 30 kg. Accelerated approval can be withdrawn if confirmatory evidence does not support clinical benefit. Research-chemical SS-31 is a different object: it is not the labelled drug, and it does not inherit the approval. A payer may be asked to cover labelled Forzinity as a rare-disease specialty product. That is not a coverage guarantee. Research SS-31 is not a reimbursable labelled medicine.

Investigational (Stealth BioTherapeutics programs). Access is a trial or, in limited cases, an expanded-access/rare-disease pathway — not a retail peptide shop. Research-chemical 'SS-31' is not the trial product.

Same four pathways as the Sourcing guide.

Trial product is study-funded. No approved US benefit. Rare-disease expanded access is case-by-case.

SS-31 powders sold to longevity buyers. Those are not GMP trial supply.

Strand does not list vendors. See the grey market.

The Forzinity label lists injection-site reactions as the most common adverse reactions. Hypersensitivity, including serious reactions, is a labelled warning. The product contains benzyl alcohol and is not approved for use in neonates. MMPOWER-3 reported that subcutaneous elamipretide was generally tolerated in that trial. Trial tolerability is not a green light for unregulated SS-31.

• Injection-site reactions are common in trials.
• Mixed efficacy by indication — failed primaries are data, not a conspiracy.
• Unregulated SS-31 adds identity and sterility risk the trial never assigned.

• FDA accelerated approval notice, 19 September 2025 · 2025

  FDA Grants Accelerated Approval to First Treatment for Barth Syndrome. Forzinity (elamipretide) injection. NDA 215244. Patients weighing at least 30 kg. Intermediate endpoint: knee extensor muscle strength. Confirmatory trial required.

• Forzinity (elamipretide) prescribing information · 2025

  DailyMed label, NDA 215244. Indicated to improve muscle strength in adult and pediatric patients with Barth syndrome weighing at least 30 kg. Accelerated approval based on knee extensor muscle strength. Setid 146bf34c-76f2-48db-ac07-fb29cce2cd75.

• Reid Thompson et al., TAZPOWER · 2021 · Genet Med

  A phase 2/3 randomized clinical trial followed by an open-label extension to evaluate elamipretide in Barth syndrome. Genet Med. 2021. Randomized period missed primary endpoints. PMID 33077895. DOI 10.1038/s41436-020-01006-8. PMID 33077895.

• Karaa et al., MMPOWER-3 · 2023 · Neurology

  Efficacy and safety of elamipretide in primary mitochondrial myopathy. Neurology. 2023. Missed primary endpoints (6MWT and fatigue). PMID 37268435. DOI 10.1212/WNL.0000000000207402. PMID 37268435.

• Szeto, cardiolipin-protective SS-31 review · 2014 · Br J Pharmacol

  First-in-class cardiolipin-protective compound as a therapeutic agent to restore mitochondrial bioenergetics. Br J Pharmacol. 2014. PMID 24117165. DOI 10.1111/bph.12461. PMID 24117165.