{"id":"ss-31","name":"SS-31 (elamipretide)","aliases":["elamipretide","MTP-131","Bendavia","Forzinity","Elamipretide HCl","D-Arg-Dmt-Lys-Phe-NH2"],"url":"https://lyoresearch.com/compounds/ss-31","class":{"id":"longevity-compounds","name":"Mitochondrial, antioxidant and longevity compounds","url":"https://lyoresearch.com/classes/longevity-compounds"},"summary":"SS-31, developed as elamipretide, is a four-amino-acid peptide that concentrates in mitochondria and binds cardiolipin, a lipid of the inner membrane. After a decade of trials it was approved in the United States in September 2025 for Barth syndrome, an ultra-rare genetic disease — on the strength of an open-label extension, since its randomised crossover missed both primary endpoints. Larger randomised trials in primary mitochondrial myopathy and in heart failure were negative. It is a genuine, narrowly approved medicine, not a general 'mitochondrial' or anti-ageing treatment.","overall_grade":"C","overall_grade_meaning":"weak human evidence","human_trials":"Several RCTs (mostly negative) + one approval","regulatory_status":"Approved (Rx, US; Barth syndrome only)","molecule":{"formula":"C32H49N9O5","molecular_weight":"639.8","cas":"736992-21-5","pubchem_cid":11764719,"note":null},"pharmacokinetics":{"basis":"label","route":"Subcutaneous injection, once daily","half_life":"Not stated in the label","licensed_regimen":"40 mg subcutaneously once daily in patients weighing at least 30 kg (Barth syndrome)","product":"Forzinity (elamipretide)","source":{"title":"Forzinity prescribing information (DailyMed)","url":"https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=146bf34c-76f2-48db-ac07-fb29cce2cd75"}},"outcomes":[{"outcome":"Barth syndrome (muscle strength & symptoms)","grade":"C","grade_meaning":"weak human evidence","effect_size":"small","adverse":false,"human_studies":"1 crossover RCT + open-label extension (n=12)","evidence":"TAZPOWER: the 12-week randomised crossover missed both primary endpoints; improvements in walk distance and symptom score emerged only in the open-label extension at 36 weeks. This extension is the basis of the 2025 accelerated approval.","references":[{"citation":"Thompson WR, et al. A phase 2/3 randomized clinical trial followed by an open-label extension to evaluate elamipretide in Barth syndrome (TAZPOWER).","where":"Genet Med, 2021;23:471–478","url":"https://pubmed.ncbi.nlm.nih.gov/33077895/"}],"verbatim":{"text":"In part 1 neither primary endpoint was met. At 36 weeks in part 2, there were significant improvements in 6MWT (+95.9 m, p = 0.024) and BTHS-SA (-2.1 points, p = 0.031).","citation":"Thompson WR, et al. A phase 2/3 randomized clinical trial followed by an open-label extension to evaluate elamipretide in Barth syndrome (TAZPOWER).","url":"https://pubmed.ncbi.nlm.nih.gov/33077895/"}},{"outcome":"Primary mitochondrial myopathy","grade":"D","grade_meaning":"no human evidence","effect_size":"not measurable","adverse":false,"human_studies":"1 phase 3 RCT (n=218)","evidence":"MMPOWER-3, the pivotal trial in the larger primary-mitochondrial-myopathy population, was negative on both primary endpoints at 24 weeks.","references":[{"citation":"Karaa A, et al. Efficacy and safety of elamipretide in individuals with primary mitochondrial myopathy: the MMPOWER-3 randomized clinical trial.","where":"Neurology, 2023;101:e238–e252","url":"https://pubmed.ncbi.nlm.nih.gov/37268435/"}],"verbatim":{"text":"The study did not meet its primary endpoints assessing changes in the 6MWT and PMMSA total fatigue score (TFS).","citation":"Karaa A, et al. Efficacy and safety of elamipretide in individuals with primary mitochondrial myopathy: the MMPOWER-3 randomized clinical trial.","url":"https://pubmed.ncbi.nlm.nih.gov/37268435/"}},{"outcome":"Heart failure (reduced ejection fraction)","grade":"D","grade_meaning":"no human evidence","effect_size":"not measurable","adverse":false,"human_studies":"1 phase 2 RCT (n=71)","evidence":"PROGRESS-HF tested four weeks of daily elamipretide against placebo and found no improvement in left-ventricular end-systolic volume.","references":[{"citation":"Butler J, et al. Effects of elamipretide on left ventricular function in patients with HFrEF: the PROGRESS-HF phase 2 trial.","where":"J Card Fail, 2020;26:429–437","url":"https://pubmed.ncbi.nlm.nih.gov/32068002/"}],"verbatim":{"text":"Elamipretide was well tolerated but did not improve LVESV at 4 weeks in patients with stable HFrEF compared with placebo.","citation":"Butler J, et al. Effects of elamipretide on left ventricular function in patients with HFrEF: the PROGRESS-HF phase 2 trial.","url":"https://pubmed.ncbi.nlm.nih.gov/32068002/"}},{"outcome":"Dry age-related macular degeneration","grade":"C","grade_meaning":"weak human evidence","effect_size":"small","adverse":false,"human_studies":"1 phase 2 RCT (n=176)","evidence":"ReCLAIM-2 missed its two primary endpoints; a slowing of ellipsoid-zone loss on OCT is a secondary signal the developer is carrying into phase 3.","references":[{"citation":"Ehlers JP, et al. ReCLAIM-2: a randomized phase 2 clinical trial evaluating elamipretide in dry age-related macular degeneration.","where":"Ophthalmol Sci, 2025;5:100628","url":"https://pubmed.ncbi.nlm.nih.gov/39605874/"}],"verbatim":{"text":"While the primary end points were not met in this phase II study, elamipretide treatment was associated with a slowing of progressive EZ degradation/loss, a surrogate for photoreceptor damage.","citation":"Ehlers JP, et al. ReCLAIM-2: a randomized phase 2 clinical trial evaluating elamipretide in dry age-related macular degeneration.","url":"https://pubmed.ncbi.nlm.nih.gov/39605874/"}},{"outcome":"Safety in humans","grade":"C","grade_meaning":"weak human evidence","effect_size":"small","adverse":true,"human_studies":"Across the trial programme","evidence":"Consistently well tolerated across trials; the main issue is injection-site reactions. Long-term safety data come mostly from the small Barth open-label extension.","references":[{"citation":"Karaa A, et al. Efficacy and safety of elamipretide in individuals with primary mitochondrial myopathy: the MMPOWER-3 randomized clinical trial.","where":"Neurology, 2023;101:e238–e252","url":"https://pubmed.ncbi.nlm.nih.gov/37268435/"}],"verbatim":{"text":"Elamipretide treatment was well-tolerated with most adverse events being mild to moderate in severity.","citation":"Karaa A, et al. Efficacy and safety of elamipretide in individuals with primary mitochondrial myopathy: the MMPOWER-3 randomized clinical trial.","url":"https://pubmed.ncbi.nlm.nih.gov/37268435/"}}],"regions":[{"region":"European Union","status":"Not authorised","note":"No EMA marketing authorisation. Supplying it for human use is an offence under national medicines law."},{"region":"United States","status":"Approved (Barth syndrome only)","note":"Accelerated approval September 2025 as Forzinity (elamipretide) for Barth syndrome. Any other use, and any product sold as 'SS-31' outside that channel, is unapproved."},{"region":"United Kingdom","status":"Not licensed","note":"No MHRA licence. Sold otherwise as an unlicensed medicine or research chemical."},{"region":"Australia","status":"Not on the ARTG","note":"Prescription-only, unapproved; imports without a prescription are seized."},{"region":"Canada","status":"Not authorised","note":"No Drug Identification Number."},{"region":"Sport (WADA)","status":"Not listed","note":"Not named on the 2026 Prohibited List; athletes should still check, since new peptides are added regularly."}],"faq":[{"q":"Is SS-31 approved?","a":"Only for one disease. In September 2025 the US FDA approved elamipretide (Forzinity) for Barth syndrome, an ultra-rare genetic disorder. It is not approved for heart failure, general fatigue, ageing or 'mitochondrial health', and the trials in the larger conditions were negative."},{"q":"Is SS-31 the same as elamipretide?","a":"Yes. SS-31 is the research name; elamipretide is the drug name; MTP-131 and Bendavia are older codes for the same molecule."},{"q":"Does it help with ageing or energy?","a":"There is no human evidence for that. Its record in people is one narrow approval and several failed trials in serious diseases."}],"references":[{"cite":"Thompson WR, et al. A phase 2/3 randomized clinical trial followed by an open-label extension to evaluate elamipretide in Barth syndrome (TAZPOWER).","where":"Genet Med, 2021;23:471–478","url":"https://pubmed.ncbi.nlm.nih.gov/33077895/","note":"12 subjects; part-1 crossover negative, part-2 extension positive at 36 weeks."},{"cite":"Karaa A, et al. Efficacy and safety of elamipretide in individuals with primary mitochondrial myopathy: the MMPOWER-3 randomized clinical trial.","where":"Neurology, 2023;101:e238–e252","url":"https://pubmed.ncbi.nlm.nih.gov/37268435/","note":"218 participants; both primary endpoints negative."},{"cite":"Butler J, et al. Effects of elamipretide on left ventricular function in patients with HFrEF: the PROGRESS-HF phase 2 trial.","where":"J Card Fail, 2020;26:429–437","url":"https://pubmed.ncbi.nlm.nih.gov/32068002/","note":"71 patients; no effect on LVESV."},{"cite":"Ehlers JP, et al. ReCLAIM-2: a randomized phase 2 clinical trial evaluating elamipretide in dry age-related macular degeneration.","where":"Ophthalmol Sci, 2025;5:100628","url":"https://pubmed.ncbi.nlm.nih.gov/39605874/","note":"176 patients; primaries missed, ellipsoid-zone secondary signal."},{"cite":"US FDA / Stealth BioTherapeutics. Accelerated approval of Forzinity (elamipretide) for Barth syndrome.","where":"FDA, September 2025","url":"https://www.fda.gov/drugs","note":"First therapy approved for Barth syndrome; accelerated approval."}],"last_reviewed":"2026-09-03","literature_searched_to":"2026-09-03","changelog":[{"date":"2026-09-03","note":"Initial publication. Grades reflect one accelerated approval and several negative randomised trials."}],"license":"CC BY 4.0 — cite as “LYO Research” with a link.","methodology":"https://lyoresearch.com/methodology"}