Dr. Pep

Peptides · Mitochondria-targeted tetrapeptide (cardiolipin binder)

SS-31: what the studies show

Every line below comes from a study, label or regulator record, checked by two models, with the source linked. Information, not medical advice. For adults 18+.

What it is

  • SS-31 is the research name for elamipretide (also MTP-131, Bendavia), a short synthetic peptide (four amino acids) that attaches to cardiolipin, a fat found in the inner membrane of mitochondria, the cell's energy plants. It is given by injection.[1][2]
  • Elamipretide is now an approved drug. The Forzinity label (2025) is for improving muscle strength in adults and children weighing at least 30 kg who have Barth syndrome, a rare genetic mitochondrial disease. The approval is accelerated, based on knee-extensor muscle strength, and continued approval may depend on a confirmatory trial.[1]

Bottom line

  • Elamipretide has real human trials, and it is approved only for Barth syndrome. Trials in other conditions mostly missed their main goals: heart attack, heart failure and a large mitochondrial myopathy study. There is no evidence that it helps healthy people or slows ageing.[1][3][4][5][2]

What the human studies found

  • Barth syndrome: in a randomised, double-blind, placebo-controlled crossover trial of 12 patients (40 mg daily for 12 weeks), neither primary endpoint (6-minute walk, symptom score) was met. In the open-label extension, 10 patients continued; the 6-minute walk improved by 96.1 m at week 168 (p=0.003). The label states the drug was not superior to placebo in the randomised part, and the muscle-strength gain was seen only in the extension. An open extension without a control group cannot separate drug effect from other changes.[6][7][1]
  • Primary mitochondrial myopathy: in the phase 3 MMPOWER-3 RCT (218 adults, subcutaneous elamipretide vs placebo for 24 weeks), the change in 6-minute walk distance versus placebo was -3.2 m (95% CI -18.7 to 12.3) and fatigue score did not differ. Both main goals were missed. Treatment was well tolerated.[3]
  • Heart failure with reduced ejection fraction: in a double-blind RCT in 71 patients, elamipretide 4 mg or 40 mg daily for 28 days did not reduce left ventricular end-systolic volume versus placebo.[4]
  • Heart attack: in the EMBRACE STEMI phase 2a RCT (first anterior STEMI, infusion 0.05 mg/kg/h for 1 hour during angioplasty), infarct size by CK-MB did not differ from placebo and no secondary outcomes improved. It was safe and well tolerated.[5]
  • Dry age-related macular degeneration: in the phase 2 ReCLAIM-2 RCT (176 patients, 117 on elamipretide), the main goals (vision and geographic atrophy area) were not met. A nominal reduction in loss of the ellipsoid zone, a retinal imaging marker, was reported. Injection-site reactions were most common, and adverse events were 86% versus 71% on placebo.[8]
  • Healthy older adults: in a randomised trial of 39 people aged 60 to 85 with poorly working mitochondria, a single 2-hour infusion raised muscle energy capacity (ATPmax) immediately (p=0.045) but not 7 days later, and did not improve muscle fatigue resistance. This tests one dose in one hand muscle.[2]

Known risks and side effects

  • Label: the most common adverse reactions are injection-site reactions (redness, pain, hardening, itching, bruising, hives). Serious allergic reactions needing emergency care have been reported, from minutes to months after starting, and serious hypersensitivity is a contraindication.[1]
  • Label: the product contains benzyl alcohol (20 mg/mL) and is not approved for neonates or intravenous use because of fatal gasping syndrome seen with benzyl alcohol in premature infants.[1]
  • The label safety database is small: 12 male patients aged 12 to 35 with Barth syndrome. Safety in healthy adults and long-term use outside this group is not established.[1]

Legal status

  • Forzinity (elamipretide) has an FDA label dated 2025 under accelerated approval for Barth syndrome in patients weighing at least 30 kg.[1]
  • An FDA warning letter dated 2026-08-24 to Peptide Partners LLC named "SS-31 (Elamipretide)" sold on its website, with semaglutide, tirzepatide, retatrutide, tesamorelin and PT-141, as an unapproved new drug under section 505(a) of the FD&C Act. The approval for Forzinity does not cover research-labelled SS-31 vials sold online.[9][1]

Sources

  1. [1] Forzinity (Elamipretide Hydrochloride) Injection prescribing information
  2. [2] In vivo mitochondrial ATP production is improved in older adult skeletal muscle after a single dose of elamipretide in a randomized trial.
  3. [3] Efficacy and Safety of Elamipretide in Individuals With Primary Mitochondrial Myopathy: The MMPOWER-3 Randomized Clinical Trial.
  4. [4] Effects of Elamipretide on Left Ventricular Function in Patients With Heart Failure With Reduced Ejection Fraction: The PROGRESS-HF Phase 2 Trial.
  5. [5] EMBRACE STEMI study: a Phase 2a trial to evaluate the safety, tolerability, and efficacy of intravenous MTP-131 on reperfusion injury in patients undergoing primary percutaneous coronary intervention.
  6. [6] A phase 2/3 randomized clinical trial followed by an open-label extension to evaluate the effectiveness of elamipretide in Barth syndrome, a genetic disorder of mitochondrial cardiolipin metabolism.
  7. [7] Long-term efficacy and safety of elamipretide in patients with Barth syndrome: 168-week open-label extension results of TAZPOWER.
  8. [8] ReCLAIM-2: A Randomized Phase II Clinical Trial Evaluating Elamipretide in Age-related Macular Degeneration, Geographic Atrophy Growth, Visual Function, and Ellipsoid Zone Preservation.
  9. [9] FDA: Warning Letter, Peptide Partners LLC (2026-08-24), research-use-only semaglutide, tirzepatide, retatrutide, tesamorelin, PT-141