SS-31
Longevity & mitochondrialAlso known as Elamipretide, Bendavia, MTP-131, Forzinity
A four-amino-acid peptide that binds cardiolipin in the inner mitochondrial membrane. Approved in the United States in September 2025, for one rare disease.
How it works
D-Arg-dimethylTyr-Lys-Phe-NH2. It concentrates in the inner mitochondrial membrane and binds cardiolipin, the lipid that organises the electron transport chain into supercomplexes. Binding cardiolipin changes how cytochrome c interacts with it, which the approved label describes as improving mitochondrial morphology and function. It is not an antioxidant supplement and not a hormone.
In the body
Animal data. 4 hours, measured in dogs given it intravenous, reported by ADDF Cognitive Vitality review, SS-31. Check it yourself. The dashed curve shows how the shape behaves, not how much is in you, and nothing is calculated from it: no time to clear, no build-up, no steady state.
Not stated anywhere citable for people. This is the unusual case of an approved drug whose label reports absorption, distribution and excretion but no half-life: peak at 0.5 to 1 hour after subcutaneous injection, 92% bioavailable, and essentially the whole dose recovered in urine as parent or the M1 and M2 metabolites by 48 hours, with minimal accumulation on daily dosing. Those facts bound it below a day without giving a figure. The 4 hours recorded here was measured in dogs given it intravenously, so the curve drawn from it shows a shape and not a level.
Your notes
Doses
40 mg subcutaneously once daily, in the abdomen or outer thigh, rotating sites. Halved to 20 mg in adults with an eGFR under 30 mL/min who are not on dialysis. This is the Barth syndrome dose in patients weighing at least 30 kg, and it is the same 40 mg daily dose used in the mitochondrial myopathy and heart failure trials.
Vial sizes
Commonly treated as good for 28 days refrigerated once reconstituted.
Side effects
- Injection site reactions, which are close to universal: every patient in the approved crossover trial had injection site erythema, and induration, pruritus and pain each affected two thirds or more.
- Raised eosinophils, appearing when dosing runs past 30 days and peaking around day 90, then returning to baseline on continued treatment or after stopping. Not associated with any symptom or other laboratory change.
- Hypersensitivity, including reactions needing emergency treatment. Rash, papular lesions, eczematous dermatitis and cough, from minutes to months after starting.
Cautions
- Serious hypersensitivity to elamipretide. Anyone who has had one should not be rechallenged.
- Neonates. The approved solution is preserved with benzyl alcohol, 20 mg/mL, which has caused fatal gasping syndrome in low birth weight and preterm infants.
- Severe renal impairment without a dose reduction. Exposure to the M1 and M2 metabolites rose by 280% and 640% at a creatinine clearance under 30 mL/min.
- Known or suspected cancer, cautiously. In one mouse model of liver cancer, mitochondria-targeted antioxidants including this one increased tumour number and size while conventional antioxidants reduced them. Mouse data, one model, and never assessed in people.
Status
Approved by the FDA in September 2025 as Forzinity, to improve muscle strength in Barth syndrome at 30 kg and above. That is an accelerated approval resting on knee extensor strength, an intermediate endpoint, in twelve patients. Its phase 3 trial in primary mitochondrial myopathy, MMPOWER-3, enrolled 218 people and missed its primary endpoints, as did phase 2 trials in heart failure and the original Barth trial.
Sources
Reference information for personal record-keeping. Not medical advice, and not a recommendation to use any of these compounds.