SS-31
SS-31 is a mitochondria-targeted peptide that concentrates at the inner mitochondrial membrane, studied for its interaction with cardiolipin and its role in reducing oxidative stress in research models.
Part of KYIN Peptides' standard catalogue — see the product page for pricing, or paired with MOTS-c in our Mitochondrial Bundle.
What Is SS-31?
SS-31 is one of the clearer examples of a serendipitous discovery in peptide research. Hazel Szeto and Peter Schiller weren't looking for a mitochondrial compound at all — they were studying opioid receptors as part of a broader peptide-chemistry research program, part of what became known more generally as the Szeto–Schiller (SS) peptide series. In the course of that work, they found that one of their lead compounds behaved unexpectedly: it concentrated heavily inside mitochondria and bound tightly to cardiolipin, a phospholipid found almost exclusively on the inner mitochondrial membrane. That single observation redirected the entire research program. SS-31 is an amphipathic tetrapeptide, alternating basic and aromatic amino acids in a pattern that gives it a strong affinity for cardiolipin-rich membranes. See its full discovery history.
Research Focus
Because SS-31's entire research relevance stems from its cardiolipin-binding discovery, most research applications trace directly back to that single mechanistic finding. It sits in KYIN's Longevity & Cellular Health category alongside Epitalon and NAD+, and is paired with MOTS-c in our Mitochondrial Bundle. See our Longevity & Cellular Health research overview, or how it compares to MOTS-c and Epitalon.
- Mitochondrial membrane research
- Oxidative stress studies
- Cardiolipin interaction research
Clinical & Preclinical Trial Data
The TAZPOWER trial studied SS-31 (as elamipretide) in 12 genetically-confirmed Barth syndrome patients: a 28-week randomized, double-blind, placebo-controlled phase, followed by a 168-week open-label extension. In the blinded 28-week phase, elamipretide did not reach statistical significance against placebo on its primary endpoints. The positive results came later, from the open-label extension: knee extensor muscle strength improved more than 45%, and 6-Minute Walk Test distance improved by 96.1 meters at week 168 versus the extension's own baseline (p=.003). The FDA's accelerated approval of FORZINITY (elamipretide) in September 2025 was based on this muscle-strength and open-label data, specifically for Barth syndrome — not on the initial blinded trial result. Separately, trials in primary mitochondrial myopathy (the MMPOWER program) produced mixed, inconclusive results, underlining that the approval is specific to Barth syndrome rather than mitochondrial dysfunction broadly. It's the first FDA-approved mitochondria-targeted therapeutic of any kind, though the approval applies to the pharmaceutical product FORZINITY under prescription and medical supervision — KYIN's SS-31 is sold strictly for laboratory research use, not as an approved drug.
Availability
SS-31 is part of KYIN Peptides' standard catalogue — see the product page for pricing, or contact us to order.
SS-31 questions
What is SS-31?
SS-31 is an amphipathic tetrapeptide discovered by Hazel Szeto and Peter Schiller during opioid-receptor research, when one of their lead compounds unexpectedly concentrated inside mitochondria and bound tightly to cardiolipin, a phospholipid found almost exclusively on the inner mitochondrial membrane. It is studied for its role in reducing oxidative stress.
Has SS-31 been tested in human trials?
Yes. Under the pharmaceutical brand name FORZINITY (elamipretide), it received FDA accelerated approval in September 2025 to improve muscle strength in patients with Barth syndrome, a rare genetic disorder of mitochondrial cardiolipin metabolism. The approval was supported by the TAZPOWER trial's open-label extension, which showed more than 45% improvement in knee extensor muscle strength.
Does KYIN Peptides sell SS-31?
Yes — SS-31 is part of our standard catalogue, both individually and in our Mitochondrial Bundle. See the product page for pricing.
Interested in SS-31?
See pricing and order on the product page, or browse our other longevity-focused peptides.