SS-31 vs Vilon.

SS-31, known generically as elamipretide and chemically as the tetrapeptide D-Arg-Dmt-Lys-Phe-NH₂ (Dmt = 2',6'-dimethyltyrosine), is a synthetic, cell-permeable, mitochondria-targeting peptide of the "Szeto-Schiller" (SS) aromatic-cationic class, originally discovered by Hazel Szeto and Peter Schiller at Cornell during opioid-peptide work. It is the lead clinical candidate of this class and, as elamipretide HCl, received its first regulatory approval in 2025. It is best understood as a mitochondrial protective/bioenergetic agent rather than a growth-factor or "anabolic" peptide.

Vilon is a synthetic dipeptide, L-lysyl-L-glutamate (Lys-Glu), one of the short peptide bioregulators developed by Vladimir Khavinson's St. Petersburg Institute of Bioregulation and Gerontology in Russia. It was designed as a minimal synthetic analogue reflecting active sequences found in thymic peptide preparations such as thymalin. Despite its very small size, it is promoted as a geroprotective and immunomodulatory agent. It is a research compound with no approved medical use.

SS-31 carries an alternating aromatic-cationic motif giving it a net positive charge that drives selective, concentration-dependent accumulation (reported >1000-fold over cytosol) in the inner mitochondrial membrane, where it binds reversibly to cardiolipin, an anionic phospholipid unique to that membrane. By associating with cardiolipin it is thought to stabilize cristae architecture, protect the cardiolipin-cytochrome c interaction and electron-transport-chain organization, support membrane potential and ATP synthesis, and reduce mitochondrial reactive oxygen species. Unlike a classic free-radical scavenger, current biophysical work (e.g., studies of its effect on bilayer surface electrostatics) frames its primary action as modulation of mitochondrial membrane structure/electrostatics rather than simple antioxidant chemistry. These mechanisms are well characterized in cell and tissue models; the downstream clinical consequences in humans remain only partially established.

Vilon is hypothesized to act as a gene-regulating bioregulator: proponents propose that the dipeptide can penetrate cells, bind DNA and histones, and alter chromatin accessibility to switch on genes silenced with aging. In immune tissue it is reported to activate T-helper cells and modulate age-associated immune changes. Some microarray studies from the originating group describe changes in gene expression in mouse tissues after vilon exposure. As with other Khavinson peptides, these mechanistic claims rest mainly on the developing laboratory's own experiments rather than on independent confirmation.

The strongest human evidence is in Barth syndrome: based largely on the TAZPOWER program (an improvement in knee-extensor muscle strength taken as reasonably likely to predict clinical benefit), the FDA granted accelerated approval to elamipretide HCl (brand FORZINITY, Stealth BioTherapeutics) in September 2025 for Barth syndrome in patients weighing at least 30 kg, the first approved mitochondria-targeted peptide. In contrast, the larger Phase 3 MMPOWER-3 trial in primary mitochondrial myopathy (Karaa et al., Neurology 2023, ~218 participants) FAILED its co-primary endpoints (6-minute walk test and Total Fatigue Score), though post hoc analyses suggested possible benefit in a mitochondrial-DNA replisome/maintenance subgroup, motivating the follow-up NuPOWER trial. Trials in heart failure (PROGRESS-HF) and dry age-related macular degeneration (ReCLAIM) likewise missed their primary endpoints. Most other indications (kidney injury, aging, Barth cardiac and broader neurodegeneration) rest on preclinical/animal data, so the human evidence base is narrow and, outside Barth syndrome, largely negative or unproven.

The vilon evidence base is almost entirely preclinical and comes from Vladimir Khavinson, Vladimir Anisimov and colleagues, published largely in Russian journals. Reported findings include inhibition of spontaneous and chemically induced tumors and increased lifespan in mice, plus effects on biological-age markers and gene expression. These are animal and cell studies from a single research tradition; there are essentially no independent Western randomized controlled trials or robust human efficacy data. To state it plainly: there are no human clinical trials of vilon in the mainstream indexed literature, so every claim about human benefit is an extrapolation from rodent and cell-culture work. The animal studies are typically conducted in inbred mouse strains at a single institution, with lifespan and tumor incidence as endpoints, without blinded pathology review, without preregistration, and without replication in a second laboratory using a different animal facility and diet, all of which are known to influence rodent lifespan results. The mechanistic work is similar in character: microarray and cell-culture studies attributing changes in gene expression to direct dipeptide interaction with DNA and histones, reported by the originating group and by a small number of collaborating laboratories, including studies of short peptides in stem cell differentiation and in monocyte and macrophage cell lines. The internal consistency of results within the group is notable, but the lack of external replication is a major limitation. Claims of anti-aging or immune benefit in humans should therefore be regarded as unproven. Compared with its siblings in the same Khavinson tradition, vilon sits at the least developed end: thymalin and cortexin at least have registered clinical use and observational human reports in Russia, and Cerebrolysin, an unrelated animal-tissue peptide preparation, has enough independent randomized trials to have been assessed twice by Cochrane. Vilon has none of that. There is no published modern toxicology dossier, no human pharmacokinetic data, and no regulatory dossier available for external review.

Across clinical trials the most commonly reported adverse events have been injection-site reactions (pain, redness, swelling) consistent with subcutaneous administration, with milder reports of headache, dizziness, and nausea; published trial data generally did not show clinically significant changes in vital signs, routine labs, or ECG over extended dosing. However, long-term safety beyond the studied trial populations, and safety of non-pharmaceutical "research-use" material sold outside the approved product, are not established. Because the only rigorously studied, quality-controlled form is the FDA-approved prescription product, gray-market SS-31 carries additional unknowns around purity, sterility, and identity. This summary describes documented findings only and intentionally excludes any dosing or administration details.

In the animal studies reported by its developers, vilon appears to be well tolerated at the doses tested, with low toxicity described. However, there is no meaningful independent human safety data, no long-term human studies, and no regulatory safety review outside its originating context. Because no human trial has been conducted, there is no adverse-event table to consult: statements that vilon is safe in people are assertions rather than findings. The absence of a published modern toxicology package is the specific gap that matters, since a regulator would expect repeat-dose toxicity in two species, genotoxicity testing, reproductive toxicity, local tolerance at the injection site, and immunogenicity assessment before any first-in-human study. None of that is available in the indexed literature. The identity and purity of material sold as vilon for research use are not guaranteed, and lyophilized vials distributed through research-chemical channels are not manufactured to pharmaceutical standards, are not tested for sterility or bacterial endotoxin, and may differ from the labeled peptide in content or purity. Injecting a non-sterile preparation carries the ordinary hazards of contamination, including local infection and systemic febrile reactions. A compound proposed to alter gene expression and immune cell behavior also warrants caution in anyone with a history of malignancy or autoimmune disease, a question that has never been addressed experimentally in humans. This is educational information only and not medical or dosing advice.

As elamipretide HCl (FORZINITY), SS-31 received FDA accelerated approval in September 2025 for Barth syndrome, making it the first approved mitochondria-targeted peptide; accelerated approval means continued approval may depend on confirmatory benefit. For all other uses (e.g., heart failure, mitochondrial myopathy, ophthalmic and "anti-aging" applications) it remains investigational or unproven, and material marketed as "SS-31" for research is not an FDA-approved drug for those purposes.

Vilon is not approved as a drug by the US FDA, the European Medicines Agency, or other major Western regulators, and it is not a dietary supplement. It is sold and used only as a research chemical, and human clinical use is not sanctioned in the US.