Compare prices and buy SS-31 from 36 research peptide vendors - also called suppliers or sources. Updated daily.
SS-31 (elamipretide, CAS 736992-21-5) is a synthetic tetrapeptide, D-Arg-2,6-dimethyl-Tyr-Lys-Phe-NH2, that concentrates in the inner mitochondrial membrane and binds cardiolipin, the signature phospholipid of that membrane. In laboratory studies this binding stabilizes cristae architecture and respiratory-chain function, supporting ATP synthesis and reducing reactive oxygen species. As elamipretide, under the brand name Forzinity, it holds an FDA accelerated approval to improve muscle strength in Barth syndrome.
For research purposes only. Not medical advice.
SS-31 is a synthetic tetrapeptide (four amino acids: D-Arg-2',6'-dimethyltyrosine-Lys-Phe-amide) known in the scientific literature as Szeto-Schiller peptide 31 and by the international nonproprietary name elamipretide. Earlier development names include MTP-131 and Bendavia.
Its defining property is targeting. SS-31 concentrates in the inner mitochondrial membrane, where it binds cardiolipin, the signature phospholipid of that membrane. By stabilizing cardiolipin's interactions with membrane proteins, it supports the folded "cristae" architecture of the inner membrane and the assembly of the respiratory-chain supercomplexes that carry out oxidative phosphorylation. In laboratory systems this is associated with more efficient ATP synthesis and reduced production of reactive oxygen species. This structural, membrane-targeted mechanism sets SS-31 apart from MOTS-C, another peptide in the mitochondrial category, which is a mitochondrial-derived signaling peptide that acts through metabolic pathways rather than by binding a membrane lipid.
SS-31 (elamipretide) has been evaluated by Stealth BioTherapeutics in several controlled trials, with mixed results worth reporting plainly. In primary mitochondrial myopathy, the Phase 3 MMPOWER-3 trial (published in Neurology in 2023) did not meet its primary endpoints. The difference from placebo on the six-minute walk test was not statistically significant. In Barth syndrome, an ultra-rare genetic disorder of cardiolipin metabolism, the Phase 2/3 TAZPOWER trial showed no significant effect on its primary endpoints during the randomized phase, though improvements in functional and cardiac measures were reported during a subsequent open-label extension.
On September 19, 2025, the FDA granted accelerated approval to elamipretide (brand name FORZINITY, from Stealth BioTherapeutics) to improve muscle strength in adult and pediatric patients with Barth syndrome weighing at least 30 kg. The FDA called it the first treatment for Barth syndrome.
Two qualifiers matter for reading that milestone. The approval was granted under the accelerated-approval pathway on the basis of an improvement in knee-extensor muscle strength (an intermediate clinical endpoint seen during the open-label extension rather than the randomized phase), and the approval letter requires a randomized, double-blind, placebo-controlled confirmatory trial. The FDA may withdraw the approval if that trial fails to verify clinical benefit. And it is narrow: the indication is Barth syndrome specifically, a condition the FDA's review estimated at about 150 patients in the United States. It covers no other condition. Elamipretide received orphan drug and rare pediatric disease designations, and the application was granted priority review.
Because elamipretide holds a current approval, its US status is set by that application, not by the 503A bulks-list process that decides most research peptides' compounding status. It appears on neither FDA's 503A list of nominated bulk drug substances (updated May 14, 2026) nor the 503B list (updated March 21, 2025).
Research vendors sell the compound mostly as "SS-31," sometimes with the elamipretide name in parentheses. Other aliases seen on product pages and in the literature include MTP-131 and the historical name Bendavia. Some listings use altered codes instead, including MTP-31, MTS-31, MTT-31, S-31, S-31-S, PUR-31 and OC-SS. PeptideScouter verifies each listing against the molecular formula (C32H49N9O5, CAS 736992-21-5) and normalizes the various aliases to a single canonical entry so per-milligram prices stay comparable across vendors.
Yes. SS-31 (Szeto-Schiller peptide 31) is the research designation, and elamipretide is the international nonproprietary name. The same compound has also been called MTP-131 and Bendavia. It was approved by the FDA in September 2025 under the brand name FORZINITY.
Elamipretide received FDA accelerated approval on September 19, 2025 (brand name FORZINITY, Stealth BioTherapeutics) to improve muscle strength in Barth syndrome patients weighing at least 30 kg. It is a narrow orphan-disease approval based on an intermediate endpoint, with a confirmatory trial required. The SS-31 sold by research vendors is research-grade material for laboratory use only, not the approved drug and not for human consumption.
SS-31 accumulates in the inner mitochondrial membrane and binds cardiolipin, the phospholipid that organizes that membrane. By stabilizing cardiolipin-protein interactions it supports cristae structure and respiratory-chain supercomplex assembly, which in laboratory systems is linked to preserved ATP synthesis and lower reactive oxygen species. This is a mechanistic description of preclinical and clinical research, not a statement of benefit in healthy people.
Both are sold in the mitochondrial category but work differently. SS-31 is a synthetic tetrapeptide that structurally targets the inner-membrane lipid cardiolipin. MOTS-C is a mitochondrial-derived peptide that acts as a metabolic signaling molecule. They are not interchangeable, and the comparison is mechanistic rather than a ranking.
SS-31 is sold by 36 research peptide vendors indexed on PeptideScouter, with 68 tracked listings compared per vendor in the table above. Pricing is normalized and refreshed daily.
32 of the 36 indexed vendors currently have SS-31 in stock. The comparison table marks out-of-stock listings, and stock state is refreshed daily.
Studz Peptides currently lists SS-31 at $1.20/mg, the lowest listed price across 36 tracked research peptide vendors. With current vendor discount codes applied, the lowest effective price is $1.08/mg.
Discount codes are issued per vendor rather than per peptide, so any code applies across that vendor's whole catalog. All 36 vendors listing SS-31 publish a PeptideScouter code, worth 5% to 50% off. Applied, the lowest effective price falls from $1.20/mg listed to $1.08/mg at Studz Peptides. Each vendor's code is shown beside its price in the table above.
SS-31 ranges from $1.20/mg to $10.00/mg across 68 listings from 36 research peptide vendors, normalized to USD per milligram and refreshed daily.
36 research peptide vendors currently list SS-31 on PeptideScouter, with 32 in stock right now. We track 68 listings across size and kit variants.
SS-31's CAS Registry Number is 736992-21-5. It is also sold as MTP-131, S-31-S, MTT-31.
