SS-31 (Elamipretide)

Yes — SS-31 is the original research designation (from the Szeto-Schiller peptide series developed at Weill Cornell). Elamipretide is the generic name, and Forzinity is the brand name for the FDA-approved formulation marketed by Stealth BioTherapeutics since September 2025. MTP-131 and Bendavia are older development code names that appear in earlier publications. All four terms refer to the identical molecule (H-D-Arg-Dmt-Lys-Phe-NH2).

Forzinity is approved under FDA accelerated approval (September 19, 2025) for ONE indication: improvement of muscle strength in adult and pediatric patients with Barth syndrome who weigh at least 30 kg. Barth syndrome is an ultra-rare X-linked genetic disease caused by TAFAZZIN mutations — approximately 150 patients in the US. The approval is NOT for heart failure, primary mitochondrial myopathy, macular degeneration, aging, or any other mitochondrial condition. Continued approval is contingent on confirmatory trials.

There is no clinical evidence supporting SS-31 for anti-aging or general longevity use. The molecule has mechanism-of-action appeal in the aging field (mitochondrial dysfunction is a hallmark of aging, and cardiolipin peroxidation increases with age), and there is preclinical work in aged rodents showing restored muscle function. But the only randomized clinical trial conducted in an age-related disease population — ReCLAIM-2 in dry AMD — did NOT meet its primary endpoints, though it did show a secondary signal on ellipsoid-zone preservation that Phase 3 trials (ReNEW/ReGAIN) are now evaluating. Two other Phase 3 trials (MMPOWER-3 in primary mitochondrial myopathy, PROGRESS-HF in heart failure) failed outright. Until Phase 3 data from ReNEW/ReGAIN reads out, the honest answer is: SS-31 works for Barth syndrome, and we don't know if it works for anything else.

Both were negative Phase 3 trials: MMPOWER-3 (primary mitochondrial myopathy, 218 patients, 24 weeks) showed Class I evidence that elamipretide did NOT improve the 6-minute walk test or fatigue score vs placebo; PROGRESS-HF (HFrEF, 71 patients, 28 days) showed no change in LV end-systolic volume by cardiac MRI. The mechanistic biology held up — the drug does bind cardiolipin, supercomplex function does improve ex-vivo in failing human hearts (Chatfield 2019) — but these cellular effects did not translate into clinical outcomes in these populations. Why Barth worked and PMM/HFrEF didn't remains unclear. One hypothesis: in Barth, cardiolipin itself is defective (the primary molecular lesion) so stabilizing it addresses root cause; in PMM and HFrEF, cardiolipin dysfunction is downstream of other problems and stabilizing it is a partial intervention at best.

40 mg subcutaneous injection, once daily, for adult and pediatric Barth syndrome patients weighing ≥30 kg. This is a fixed dose — there is no titration schedule. Injection rotation among standard SC sites is recommended to minimize injection-site reactions, which are the most common adverse event. Treatment is chronic; improvements in 6-minute walk test and muscle strength in TAZPOWER were sustained across 168 weeks of continuous dosing. Forzinity is dispensed through specialty pharmacy by Stealth BioTherapeutics.

Peptide research vendors do sell 'research-use-only' SS-31, but this is unregulated material that has NOT been through FDA cGMP manufacturing. It is not bioequivalent to Forzinity (the approved drug), purity is not guaranteed, and there is no quality assurance on the peptide sequence or formulation. Using research-chemical SS-31 to self-treat Barth syndrome, heart failure, macular degeneration, or primary mitochondrial myopathy is strongly discouraged — particularly for Barth syndrome, where an FDA-approved formulation is available through prescription and specialty pharmacy. For non-Barth indications where no approval exists, the underlying evidence does not yet support self-treatment with any form.

No. Compounded SS-31 is not legally available in the United States. Forzinity has orphan drug exclusivity, is not on the FDA Drug Shortage list, and has no reference listed drug that would enable a compounding pathway. This differs materially from the compounded-semaglutide situation of 2022–2024, which relied on an active shortage designation. Any US compounding pharmacy offering 'compounded SS-31' is either operating outside lawful parameters or is not manufacturing the approved elamipretide formulation. For Barth syndrome patients, the approved Forzinity should be accessed through the prescribing specialist and Stealth's specialty pharmacy network.

Stealth BioTherapeutics has not publicly disclosed Forzinity pricing as of early 2026, but ultra-rare orphan drugs for indications of ~150 US patients typically price at $200,000–$750,000+ per patient per year. Barth Syndrome Foundation and Stealth have communicated intent to use standard specialty-pharmacy and patient-assistance programs to minimize out-of-pocket cost for diagnosed Barth patients, with payer reimbursement (commercial insurance, Medicaid, Medicare for eligible adults) expected to cover the wholesale acquisition cost. Patients with a confirmed TAFAZZIN-based Barth diagnosis should work with their prescribing specialist and Stealth's patient support team rather than trying to navigate access independently.

Preclinical evidence suggests limited but detectable CNS penetration. The molecule's small size (639 Da), aromatic-cationic character, and membrane-partitioning behavior allow some passage, and neuroprotective effects have been shown in preclinical spinal cord injury and traumatic brain injury models. However, no elamipretide clinical trial has been conducted in a primary CNS indication (no Parkinson's, Alzheimer's, ALS, or stroke trials). The drug's development focus has been peripheral (cardiac, skeletal muscle, retina, kidney) and the approved Barth indication works through skeletal muscle. Extrapolating to CNS use requires human CNS-penetration data that doesn't exist.

As of April 2026: (1) Phase 3 ReNEW and ReGAIN trials in dry AMD with geographic atrophy are ongoing, using the ellipsoid-zone preservation endpoint that emerged from ReCLAIM-2's secondary analysis — these are the most consequential upcoming readouts because a positive result would expand elamipretide from an ultra-rare orphan drug to a potentially large commercial indication; (2) confirmatory trials in Barth syndrome are required for continued approval under the accelerated pathway; (3) compassionate-use and expanded-access protocols continue for individual pediatric mitochondrial cases (Maeder 2023, PMID 36636586). The heart failure and primary mitochondrial myopathy programs are effectively closed following the negative Phase 3 readouts, absent new subgroup or biomarker-driven rationale.