Epithalon vs SS-31
Epithalon and SS-31 are both short synthetic peptides discussed in the context of ageing biology, but they are very different research subjects 3,6. Epithalon is a tetrapeptide (Ala-Glu-Asp-Gly) studied mainly in publications co-authored by one research group, with proposed effects on telomerase and pineal function 1,3. SS-31, also called elamipretide, is a mitochondria-targeted tetrapeptide that binds cardiolipin and received FDA accelerated approval in September 2025 for a single rare-disease indication, Barth syndrome 8,11,12.
Side by side
| Field | Epithalon | SS-31 (Elamipretide) |
|---|---|---|
| Class | Synthetic tetrapeptide, described as a pineal-regulating peptide 3,4 | Szeto-Schiller mitochondria-targeted tetrapeptide; labeled as a mitochondrial cardiolipin binder 6,11 |
| Origin and structure | Ala-Glu-Asp-Gly; a synthetic tetrapeptide studied alongside Epithalamin, a complex of peptides isolated from the pineal gland 3,5 | SS-31 (elamipretide), an amphipathic polybasic tetrapeptide of the SS peptide class 8 |
| Proposed mechanism | Induced telomerase expression, enzymatic activity and telomere elongation in human fetal fibroblast cultures 1; allowed those cells about 10 extra passages in vitro 2 | Binds cardiolipin on the inner mitochondrial membrane, protecting cristae structure and promoting ATP recovery in rat renal ischemia (animal data) 7; also modulates membrane surface electrostatics in model systems 8 |
| Half-life | Not identified in the sources reviewed | Not stated in the label sections reviewed; the label reports peak concentrations 0.5 to 1 hour after subcutaneous administration and about 92% bioavailability 11 |
| Highest human trial phase | Small, mostly uncontrolled human reports; no phase labels given in the sources reviewed 4,5 | Phase 3 (primary mitochondrial myopathy) and a crossover trial with long-term extension (Barth syndrome) 9,10,11 |
| FDA status | Listed by the FDA among bulk substances for compounding that may present significant safety risks; FDA has not identified safety information for the proposed route 13 | FDA accelerated approval (September 19, 2025) as Forzinity to improve muscle strength in patients with Barth syndrome weighing at least 30 kg; continued approval may depend on a confirmatory trial 11,12 |
| Published human outcomes | Uncontrolled reports: a stated positive clinical effect in 90% of patients with degenerative retinal lesions 4; increased night melatonin in elderly people with pineal insufficiency 5 | Barth syndrome crossover trial: not superior to placebo on its two primary endpoints; knee extensor strength increases were observed in the open-label extension, not in the randomized period 11. Primary mitochondrial myopathy phase 3 trial (218 participants): primary endpoints not met 9 |
| Safety signals | No safety findings were identified in the sources reviewed beyond a statement of no side effects in one Russian-language report 5; the FDA lacks safety information 13 | Label: injection-site reactions most common; hypersensitivity reactions including serious allergic reactions; eosinophilia; benzyl alcohol warning for neonates 11 |
| WADA status | Not individually named in the 2026 Prohibited List text reviewed; class S0 covers substances with no governmental approval for human therapeutic use, and this was not assessed here 14 | Not individually named in the 2026 Prohibited List text reviewed 14 |
| Evidence level | Cell and mouse data plus small, uncontrolled human reports, mostly from one group 1,2,3,4,5 | Regulatory-grade human trials (phase 3, crossover with extension) plus extensive animal and mechanistic data 6,9,11 |
Epithalon: what the data says
Epithalon research is concentrated in a small number of publications co-authored by one research group 1,3,4. In cultures of human fetal fibroblasts (cell data), it induced expression of the telomerase catalytic subunit, telomerase activity and telomere elongation 1, and in a follow-up study treated cells made about 10 more passages than controls 2. In female SHR mice followed until natural death (animal-only evidence), Epithalon did not change mean life span, food consumption or body weight, but was associated with a 12.3% longer maximum life span, fewer bone-marrow chromosome aberrations, and a 6-fold lower leukemia incidence, with no change in total spontaneous tumor incidence 3.
Human data are limited to older uncontrolled reports 4,5. One paper described a positive clinical effect in 90% of patients with degenerative retinal lesions, without a control group in the abstract 4. A Russian-language report described restored night-time melatonin release in elderly people with pineal insufficiency after Epithalamin or Epitalon 5.
SS-31 (Elamipretide): what the data says
SS-31 has been studied extensively in mechanistic work 6,8. It binds with high affinity to cardiolipin on the inner mitochondrial membrane, and in rats given renal ischemia (animal-only evidence) it protected cristae membranes, accelerated ATP recovery and was associated with reduced kidney injury 7. Biophysical work shows that it partitions into membranes and modulates their surface charge 8.
In humans, SS-31 (elamipretide) was tested in a 24-week phase 3 trial of 218 people with primary mitochondrial myopathy, which did not meet its primary endpoints (6-minute walk distance and fatigue score) 9. In Barth syndrome, a 12-subject crossover trial did not show superiority over placebo on its two primary endpoints; increases in knee extensor strength were seen during the open-label extension, which led to accelerated approval on an intermediate clinical endpoint 11,12. The 168-week extension reported injection-site reactions as the most common adverse events, in 10 patients who entered the extension 10.
Key research differences
- Regulatory status: SS-31 (elamipretide) has FDA accelerated approval for Barth syndrome only 11,12, while Epithalon appears on the FDA's list of bulk substances that may present significant safety risks 13.
- Proposed target: Epithalon is proposed to act through telomerase and pineal function 1,5, whereas SS-31 binds cardiolipin in the inner mitochondrial membrane 7.
- Human evidence: Epithalon has only small uncontrolled reports, mostly from one group 3,4,5; SS-31 has randomized controlled trials, which missed their primary endpoints 9,11.
- Animal evidence differs in type: Epithalon in lifespan and tumor-incidence studies in mice 3, SS-31 in organ ischemia models in rats 7.
- Safety information: SS-31 has a prescribing-information safety section listing injection-site reactions, hypersensitivity and eosinophilia 11, whereas the FDA says it has not identified safety information on Epithalon for the proposed route 13.
- Neither compound is individually named in the 2026 WADA list text reviewed 14.
Where the evidence is limited
Evidence for both compounds is limited in different ways 1,9. For Epithalon, the identified publications largely share authors from one research group, the human reports are uncontrolled, and no independent replication was identified 1,3,4. For SS-31, the randomized trials were small or did not meet their primary endpoints, the Barth syndrome approval rests on an intermediate endpoint seen in an open-label extension, and a confirmatory trial is required 9,11,12.
Frequently asked questions
Is Epithalon the same as Epithalamin?
What has been reported about Epithalon and telomeres?
Is SS-31 an approved drug?
Did SS-31 meet its endpoints in clinical trials?
References
- Epithalon peptide induces telomerase activity and telomere elongation in human somatic cells Bulletin of Experimental Biology and Medicine. 2003
- Peptide promotes overcoming of the division limit in human somatic cell Bulletin of Experimental Biology and Medicine. 2004
- Effect of Epitalon on biomarkers of aging, life span and spontaneous tumor incidence in female Swiss-derived SHR mice Biogerontology. 2003
- Pineal-regulating tetrapeptide epitalon improves eye retina condition in retinitis pigmentosa Neuroendocrinology Letters. 2002
- Normalizing effect of the pineal gland peptides on the daily melatonin rhythm in old monkeys and elderly people (in Russian) Advances in Gerontology. 2007
- First-in-class cardiolipin-protective compound as a therapeutic agent to restore mitochondrial bioenergetics British Journal of Pharmacology. 2014
- The mitochondrial-targeted compound SS-31 re-energizes ischemic mitochondria by interacting with cardiolipin Journal of the American Society of Nephrology. 2013
- The mitochondria-targeted peptide SS-31 binds lipid bilayers and modulates surface electrostatics as a key component of its mechanism of action Journal of Biological Chemistry. 2020
- Efficacy and Safety of Elamipretide in Individuals With Primary Mitochondrial Myopathy: The MMPOWER-3 Randomized Clinical Trial Neurology. 2023
- Long-term efficacy and safety of elamipretide in patients with Barth syndrome: 168-week open-label extension results of TAZPOWER Genetics in Medicine. 2024
- FORZINITY (elamipretide hydrochloride) injection: prescribing information FDA label (DailyMed). 2025
- Elamipretide: The first cardiolipin-directed mitochondrial therapeutic for Barth syndrome approved under accelerated approval Drug Discoveries & Therapeutics. 2026
- Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (Category 2; content current as of 04/22/2026) FDA (Human Drug Compounding). 2026
- International Standard: Prohibited List 2026 WADA. 2026
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