SS-31 is one of the few compounds in the research-peptide market where the active ingredient has actually completed Phase 3 human trials — and, as of September 2025, received FDA accelerated approval under a different name for a specific rare disease. That's a different evidence picture than most research peptides, and it comes with a distinction worth being precise about upfront: the approved drug and the research compound sold as SS-31 vial or SS-31 nasal spray are not the same product, even though they share the same active peptide.
SS-31, Elamipretide, and Forzinity Are the Same Molecule — Not the Same Product
SS-31 is a mitochondria-targeted tetrapeptide, also known by its generic name elamipretide. In September 2025, the FDA granted accelerated approval to Forzinity (elamipretide hydrochloride), manufactured by Stealth BioTherapeutics, to improve muscle strength in patients with Barth syndrome — a rare, life-limiting genetic disorder of mitochondrial cardiolipin metabolism. It's the first FDA-approved mitochondria-targeted therapeutic [1].
This is the same relationship the peptide research market already deals with elsewhere: semaglutide is the approved active ingredient in Ozempic, but research-grade semaglutide sold by chemical suppliers is a different product, manufactured to a different standard, for a different purpose. SS-31 works the same way. Forzinity is an FDA-approved, prescription-only pharmaceutical, produced under GMP manufacturing and indicated specifically for Barth syndrome. Research-grade SS-31 is an unapproved research compound, sold for laboratory and research use only — not the approved drug, not manufactured to the same standard, and not intended for human administration outside of that approved, prescribed context.
What SS-31 Is Proposed to Do
SS-31 accumulates selectively in the inner mitochondrial membrane, where it binds cardiolipin, a phospholipid essential to mitochondrial energy production and cristae structure. By stabilizing that membrane, SS-31 is thought to preserve electron transport chain coupling and reduce reactive oxygen species at the source, rather than scavenging free radicals after they've already formed [2]. That's a mechanistically different approach than most antioxidant compounds, which is part of why it's attracted research interest across a wide range of mitochondrial-dysfunction models — from traumatic brain injury to cardiomyopathy to age-related mitochondrial decline.
In preclinical models, SS-31 has been studied at doses roughly in the 0.1–5 mg/kg range (subcutaneous or intraperitoneal), with effects reported as early as 1 hour post-administration in some models, consistent with rapid mitochondrial accumulation. In one mouse study, SS-31 (5 mg/kg) given intraperitoneally 30 minutes after traumatic brain injury reduced markers of mitochondrial dysfunction measured 24 hours later [3]. In a separate model, SS-31 improved mitochondrial function, synaptic markers, and memory performance in mice with LPS-induced neuroinflammation [4].
What the Human Trials Actually Found
This is where SS-31 differs most from the rest of the research-peptide catalog: there's real, completed, randomized controlled trial data, and it's an honest mixed picture rather than a clean win.
Barth Syndrome — TAZPOWER
The trial that led to FDA approval was a 12-patient, randomized, double-blind, placebo-controlled crossover study: 40 mg/day subcutaneous elamipretide versus placebo, each arm 12 weeks, separated by a 4-week washout [5]. The initial double-blind phase did not clearly separate from placebo on its primary endpoints. What ultimately supported approval was the long-term open-label extension — patients followed for up to 168 weeks showed sustained improvements in functional measures relevant to the Barth syndrome cardiac and skeletal muscle phenotype [6]. That's a meaningfully different evidentiary path than a clean positive randomized trial, and it's part of why the approval was granted on an accelerated basis specific to this ultra-rare, life-limiting condition rather than a standard approval.
Primary Mitochondrial Myopathy — MMPOWER-3
A larger, 218-patient Phase 3 trial (MMPOWER-3) tested the same 40 mg/day subcutaneous dose over 24 weeks in patients with genetically confirmed primary mitochondrial myopathy, a broader and more heterogeneous patient population than Barth syndrome. This trial did not meet its primary endpoints — six-minute walk distance and total fatigue score did not separate from placebo across the full study population [7]. A post hoc subgroup analysis found a signal in patients with nuclear DNA-related mitochondrial defects, but subgroup findings from a trial that missed its primary endpoint are hypothesis-generating, not confirmatory.
Put together, the honest summary is: SS-31 has real, completed human trial data, it produced an FDA approval for one specific rare-disease indication with a long-term-extension evidence path, and it also has a completed Phase 3 trial in a different, broader condition that missed its primary endpoints. That's not a story of "proven safe and effective across the board" — it's a story of a compound whose clinical evidence is real but indication-specific.
What This Means for Research-Grade SS-31
None of the above changes what research-grade SS-31 is: an unapproved compound, sold for laboratory and preclinical research use only, not for human consumption, and not equivalent to Forzinity regardless of sharing an active peptide. The clinical trial history is relevant context for understanding SS-31's mechanism and safety profile in the published literature — it is not a basis for treating a research-grade product as a substitute for an approved, prescribed medication.
For sourcing, the same standard applies as any other research peptide: batch-specific certificates of analysis, HPLC purity with mass spectrometry identity confirmation, and clear RUO labeling. The clinical trial history doesn't change the sourcing bar — if anything, a compound with this much publication history attracts more counterfeit and mislabeled product in the research-chemical market, which makes verified documentation more important, not less.
The Takeaway
SS-31 (elamipretide) accumulates in the inner mitochondrial membrane and binds cardiolipin, a mechanism distinct from most antioxidant research compounds. It has more completed human clinical trial history than almost anything else in the research-peptide space, including an FDA accelerated approval — as Forzinity — for Barth syndrome, alongside a separate Phase 3 trial in primary mitochondrial myopathy that missed its primary endpoints. Research-grade SS-31, sold as a vial or nasal spray for laboratory use, shares the active peptide with that approved drug but is a different, unapproved product — not a substitute for it, and not intended for human use outside of that specific, prescribed, approved context.
All products are intended for research use only. Not for human consumption. Must be 21 years of age or older to purchase.
References
- Stealth BioTherapeutics. (2025). FDA Accelerated Approval of FORZINITY (elamipretide HCl) for Barth Syndrome. U.S. Food and Drug Administration accelerated approval, September 19, 2025.
- Birk, A. V., Liu, S., Soong, Y., et al. (2013). The mitochondrial-targeted compound SS-31 re-energizes ischemic mitochondria by interacting with cardiolipin. Journal of the American Society of Nephrology, 24(8), 1250-1261.
- Zhu, Y., Wang, H., Fang, J., Dai, W., Zhou, J., Wang, X., & Zhou, M. (2018). SS-31 provides neuroprotection by reversing mitochondrial dysfunction after traumatic brain injury. Oxidative Medicine and Cellular Longevity, 2018, 4783602.
- Zhao, W., Xu, Z., Cao, J., Fu, Q., Wu, Y., Zhang, X., Long, Y., Zhang, X., Yang, Y., Li, Y., & Mi, W. (2019). Elamipretide (SS-31) improves mitochondrial dysfunction, synaptic and memory impairment induced by lipopolysaccharide in mice. Journal of Neuroinflammation, 16, 230.
- Thompson, W. R., Hornby, B., Manuel, R., et al. (2021). 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. Genetics in Medicine, 23(3), 471-478.
- Long-term efficacy and safety of elamipretide in patients with Barth syndrome: 168-week open-label extension results of TAZPOWER. Genetics in Medicine, 2024.
- Karaa, A., Bertini, E., Carelli, V., et al. (2023). Efficacy and safety of elamipretide in individuals with primary mitochondrial myopathy: the MMPOWER-3 randomized clinical trial. Neurology, 101(3), e238-e252.
