SS-31
Elamipretide
SS-31, known as elamipretide, is a synthetic mitochondria-targeted peptide that binds cardiolipin in the inner mitochondrial membrane — and it is now an FDA-approved drug for one rare disease.
Regulatory status: FDA-approved in 2025 as Forzinity (NDA 215244) under accelerated approval, for improving muscle strength in adult and paediatric patients with Barth syndrome weighing at least 30 kg. A separate phase 3 trial in primary mitochondrial myopathy (MMPOWER-3) was terminated in 2020 after the double-blind portion missed its primary endpoints, so the approval is specific to Barth syndrome.
Default vial
50 mg
Default mix
2 mL
Reported range
4–40 mg
Draw (U-100)
40 u
Mitochondria-targeting peptide; trial ranges are wide.
What it is
- A synthetic aromatic-cationic tetrapeptide designed to bind cardiolipin, a phospholipid concentrated in the inner mitochondrial membrane.
- Given subcutaneously; the label specifies 40 mg once daily for the approved indication, adjusted for renal impairment.
- Developed by Stealth BioTherapeutics. The formulation contains benzyl alcohol, which drives a specific neonatal warning on the label.
- Also studied in primary mitochondrial myopathy, geographic atrophy and heart failure, with mixed trial outcomes.
How it is described to act
- 1
Absorbed and distributed systemically after subcutaneous injection, per the FDA pharmacokinetic labelling.
- 2
Its cationic structure is described in the label as allowing accumulation in tissues with high mitochondrial density.
- 3
The label describes binding to cardiolipin in the inner mitochondrial membrane, proposed to stabilise cristae structure and improve electron-transport-chain efficiency.
- 4
Clinically this underlies the approved Barth syndrome use; the mitochondrial myopathy trial did not confirm efficacy on its primary endpoint.
What the research has looked at
Barth syndrome — the approved indication
- The FDA label states approval was based on an improvement in knee extensor muscle strength, an intermediate clinical endpoint, under the accelerated approval pathway, with continued approval contingent on confirmatory trial verification.
Primary mitochondrial myopathy — terminated trial
- The phase 3 MMPOWER-3 trial (NCT03323749) was terminated because the double-blind portion did not meet its primary endpoints, per its ClinicalTrials.gov record.
Other investigational areas
- Elamipretide has also been studied in geographic atrophy / dry AMD and heart failure. Those are separate from the approval and are not covered by the current indication.
Strength of evidence: Approved drug (for a specific indication)
Approval covers one narrow indication in Barth syndrome. Evidence for other proposed uses — including general mitochondrial support or anti-ageing — is preclinical or comes from trials that missed their endpoints, and should not be conflated with the approval.
This molecule is an approved medicine for at least one indication. Where that is the case, the approved prescribing information — not community convention — governs its use.
Reported cautions and unknowns
- The label lists injection-site reactions as the most common adverse reaction.
- The label warns it is not approved for use in neonates because of benzyl-alcohol toxicity risk, including fatal reactions reported with other benzyl-alcohol-containing drugs in low-birth-weight or preterm neonates.
- The label also warns of hypersensitivity reactions, including serious allergic reactions with skin and respiratory symptoms occurring anywhere from minutes to months after starting treatment, requiring discontinuation.
References
Handling this vial
- Lyophilized vials are generally stored at 2–8 °C and kept out of light; once reconstituted with bacteriostatic water they are refrigerated and commonly discarded after 28 days.
- Mix by aiming water down the vial wall and rolling gently — do not shake — and never re-freeze a reconstituted vial.
- Pep-Tidy cannot verify what is in your vial. Ask your supplier for a current Certificate of Analysis (HPLC/MS).
SS-31 questions people ask
How do you reconstitute SS-31?
A common starting point for a 50 mg vial of SS-31 is 2 mL of bacteriostatic water, which gives 25 mg per mL. Aim the water down the inside wall of the vial, let it dissolve on its own, and roll gently instead of shaking. Pep-Tidy's reconstitution calculator will recalculate the numbers for any other vial size or water volume you use.
How many units of SS-31 is one dose?
At 25 mg per mL, that works out to about 40 units on a U-100 insulin syringe for a 10000 mcg dose. Change the vial size, water volume, or target dose in the calculator and the syringe reading updates with it. This is arithmetic, not a dosing recommendation.
What dosing schedule is reported for SS-31?
Published and community sources describe 4–40 mg, subcutaneous, every day, typically run 4 weeks on and 4 weeks off. These figures describe what has been reported, not what anyone should take — talk to a licensed clinician first.
How should SS-31 be stored?
Lyophilized SS-31 vials are generally kept at 2–8 °C and out of light. Once reconstituted with bacteriostatic water they are refrigerated and commonly discarded after about 28 days. Never re-freeze a reconstituted vial and never shake it.
Read this before you act on anything above
Everything on this page is a summary of what other people have published — it is not medical advice, not a recommendation, and not a dosing instruction. Reported dose ranges describe what appears in the literature or in community protocols, not what anyone should take. Talk to a licensed clinician before using any peptide.