SS-31

SS-31 stands for Szeto-Schiller peptide 31, named after Dr. Hazel Szeto of Cornell University and Dr. Peter Schiller of the Montreal Clinical Research Institute, who characterized it in the early 2000s. It is a synthetic aromatic-cationic tetrapeptide, only four amino acids long, that carries a net positive charge, and it is also known by the drug name elamipretide and earlier development codes such as MTP-131 and Bendavia. Unlike mitochondrial-derived peptides such as MOTS-c or humanin, SS-31 is not produced naturally in the body; it was deliberately designed to concentrate inside cells and reach the inner mitochondrial membrane. Its small size and positive charge let it cross multiple membranes and accumulate where it acts on a phospholipid called cardiolipin. Stealth BioTherapeutics carried it through clinical development, and in 2025 the FDA granted it accelerated approval under the brand name Forzinity for Barth syndrome, described as the first approved therapy that specifically targets the mitochondria.

The common thread behind interest in SS-31 is mitochondrial dysfunction, which is considered one of the root drivers of aging and of many chronic diseases. Its only approved use is Barth syndrome, an ultra-rare genetic disorder affecting only a few hundred people worldwide, so every other application discussed in the wellness space is off-label. Reported interest clusters around cognitive decline and dementia, recovery from traumatic brain injury, chronic kidney disease, insulin resistance, and chronic fatigue or post-viral syndromes such as long COVID, along with general anti-aging and energy support. Because cardiolipin declines with age, some commentators frame SS-31 as most relevant from roughly age 50 onward, or when lab markers suggest mitochondrial decline, rather than for young and healthy users. It is sometimes paired with MOTS-c, with SS-31 framed as structural repair of the membrane and MOTS-c as a signaling molecule that activates AMPK, though the ideal stacking order is actively debated among practitioners.

Most peptides act on receptors or signaling pathways, but SS-31 works structurally, which is what makes it distinctive. It concentrates in the inner mitochondrial membrane and binds cardiolipin, a negatively charged phospholipid that holds the electron transport chain complexes stable. When reactive oxygen species leak from that chain, they damage cardiolipin, which destabilizes the chain and generates still more reactive oxygen species in a self-reinforcing cycle of mitochondrial decline. By binding and stabilizing cardiolipin, SS-31 is described as interrupting that cycle, protecting ATP production and reducing oxidative stress. Because it stabilizes rather than activates or stimulates growth pathways, some clinicians argue it carries less theoretical risk than peptides that push signaling or proliferative mechanisms.

Human trials of SS-31 have used intravenous infusion and subcutaneous injection, with daily subcutaneous injection being the more common and practical route in the long-term studies. There is no published human data on oral SS-31, and reportedly not even animal studies using an oral form. Although its very small four-amino-acid size might suggest some oral potential, commentators note that intestinal transporters efficiently absorb mainly two and three amino acid peptides, so a four amino acid peptide like SS-31 is more likely to be degraded without an advanced formulation. Reported protocols in the trials describe 40 mg subcutaneously per day, and some practitioners speculate that people with only mild age-related dysfunction might use less, partly for cost reasons since compounded material runs around a dollar per milligram. The 40 mg figure is what the trials used, not a dose to take.

SS-31 has an unusually deep human safety record for a peptide in this space, with multiple long-term trials at 40 mg daily reporting no significant adverse effects beyond local injection-site reactions. The strongest efficacy evidence is in Barth syndrome, where an extended trial in a small group reported meaningful improvements in muscle strength and heart function markers over roughly three years, which supported the FDA approval. Beyond that the picture is mixed: a heart failure trial and a macular degeneration trial did not show large effects, while a small phase two trial in kidney artery stenting was more encouraging. Most of the widely promoted uses, including dementia, traumatic brain injury, kidney disease, diabetes, and anti-aging, rest on mouse and other preclinical models rather than human trials, and the chronic fatigue and long COVID uses are essentially speculative, extrapolated from mechanism and anecdote. Overall the mechanism is well characterized and the safety data look strong, but human efficacy outside rare mitochondrial disease remains largely unproven.

In 2025 the FDA granted elamipretide, also known as SS-31, accelerated approval under the brand name Forzinity for Barth syndrome, making it the first approved drug that specifically targets the mitochondria. That approval is narrow, so every other use, including anti-aging, cognitive, and energy applications, is off-label. Outside that indication, material is typically obtained through compounding pharmacies or research-chemical channels, where purity and legality vary and rules differ by country. It appears under several names, including elamipretide, MTP-131, and the older code Bendavia, which can cause confusion when comparing sources.