SS-31 (Elamipretide)

What is SS-31 (elamipretide)?

SS-31 is a member of the Szeto-Schiller (SS) family of peptides, named for the researchers. These peptides selectively target the inner mitochondrial membrane. According to a 2014 review, SS-31 binds through electrostatic and hydrophobic interactions to cardiolipin, a phospholipid found only in the inner mitochondrial membrane; in this way it prevents cardiolipin from converting cytochrome c into a peroxidase, preserves the electron transport function of cytochrome c and supports the structure of the mitochondrial cristae. The review states that these findings come from extensive animal studies. ^[3] It also appears in the literature under the code name MTP-131.

The FDA prescribing information classifies elamipretide as a “mitochondrial cardiolipin binder.” The peptide sequence is D-Arg-2,6-dimethyl-Tyr-Lys-Phe-NH2; that is, it consists of four amino acids and the arginine is in the D form. Its absolute bioavailability when given subcutaneously is about 92%. ^[2]

This page treats two different things separately: Forzinity, a licensed drug, and products sold online under the name “SS-31” with a “for research purposes” label. Both carry the name of the same active substance, but they are not the same product in legal or quality terms.

What has been shown in Barth syndrome?

Barth syndrome is a rare genetic disease with X-linked recessive inheritance; according to the prescribing information, women are not expected to be affected. ^[2] The EMA orphan drug page states that in this disease cardiolipin in the inner mitochondrial membrane is deficient and that elamipretide is expected to correct energy production by binding to this lipid. ^[9] The basis of the license is the TAZPOWER trial.

This table explains why the license is “accelerated.” The randomized part was small and negative; the favorable findings came from the extension period, which had no control group. The FDA based the approval on the increase in muscle strength, an intermediate endpoint considered reasonably likely to predict clinical benefit. ^[2] Three employees of the manufacturing company are among the authors of the extension study. ^[4]

The FDA’s approval letter also records the process: the application was submitted on January 29, 2024, the company responded in full to the FDA’s May 15, 2025 action letter on August 15, 2025, and approval came on September 19, 2025. The condition of approval is confirmation of clinical benefit in a randomized, double-blind, placebo-controlled trial in Barth syndrome patients aged 5 years and older; according to the timeline submitted by the company, the trial is planned for completion in 09/2029 and the final report for submission in 03/2030. The FDA writes that it may withdraw the approval if the trial does not confirm benefit. The letter also lists 26-week carcinogenicity studies in transgenic mice, two-year carcinogenicity studies in rats and a metformin interaction study as postmarketing obligations. ^[1]

In the European Union, elamipretide received orphan designation for Barth syndrome on May 20, 2021. The EMA states explicitly that an orphan designation does not mean the drug is available or licensed. ^[9]

What happened in other diseases?

Elamipretide was tested in many diseases besides Barth syndrome. The three controlled trials below did not reach their primary endpoints.

In ReCLAIM-2, adverse event reporting was 86% in the drug group and 71% in the placebo group; the most common events were injection site reactions. Two employees of the manufacturing company are among the study’s authors, and the authors report having chosen the photoreceptor layer measurement as the primary endpoint of the phase 3 program. ^[6] MMPOWER-3 was funded by the manufacturing company, and one of the authors is a company employee. ^[5] Nominal differences in secondary endpoints are the hypothesis of a new trial; they are not counted as evidence from a trial whose primary results were negative.

Aging and performance claims

“Research peptide” sellers promote SS-31 for mitochondrial repair, anti-aging effects and neuroprotection; the product page quoted in the FDA’s 2026 warning letter uses exactly these statements. ^[10]

A randomized study in healthy older adults showed the following: in 39 healthy adults aged 60–85 selected for poor mitochondrial function, immediately after a single 2-hour intravenous infusion, mitochondrial ATP-producing capacity in the hand muscle increased compared with placebo (p=0.055 for absolute change, p=0.045 for percent change). By day 7 the difference was gone, and the muscle’s resistance to fatigue during repeated contractions did not change. ^[8] The manufacturing company funded the study; three authors were paid consultants of the company between 2014 and 2016, and the study was designed together with the company. ^[8]

This result is a short-term change in a laboratory measurement. The current elamipretide trial registered on ClinicalTrials.gov under healthy aging and physical function is a phase 2 trial in 30 healthy older adults lasting 4 weeks, with safety and tolerability as the primary outcome; at the last update enrollment was ongoing and no results have been published. ^[15] The effect on aging, long-term energy or athletic performance has therefore not been shown in humans. In the mitochondrial myopathy trial above, walking and fatigue did not improve even in people with mitochondrial disease. ^[5] For other peptides of mitochondrial origin: MOTS-c, Humanin

Is it safe? What does the prescribing information say?

Safety information for the licensed product rests on a small program of 12 male patients with Barth syndrome. According to the prescribing information, in the placebo-controlled part, injection site reactions occurred in 12 of 12 patients (100%) receiving the drug and in 8 (67%) of those receiving placebo; injection site erythema occurred in 100% with the drug and 25% with placebo. ^[2]

Other headings in the prescribing information are as follows: ^[2]

• Hypersensitivity: Hypersensitivity reactions, including serious allergic reactions requiring emergency medical intervention, were reported; reactions can appear from minutes to months after starting treatment. The drug is not given again to those who have had a serious reaction.
• Eosinophilia: In studies of 30 days or longer, blood eosinophil counts frequently rose, peaked at about day 90 and returned to baseline in 6–12 months; this was not associated with a clinical finding.
• Benzyl alcohol: The licensed product contains benzyl alcohol as a preservative and is not approved in newborns; a fatal “gasping syndrome” has been reported with benzyl-alcohol-containing drugs in low-birth-weight and premature infants.
• Kidney: A dose adjustment is defined for severe renal impairment; it has not been studied in dialysis patients.
• Cancer and pregnancy: Carcinogenicity studies have not been performed; there are no human data in pregnancy.

This information applies to the licensed product from an inspected manufacturing chain. Whether a product sold online “for research purposes” really contains elamipretide, and its purity and sterility, are unknown; general injection-related risks are covered in a separate guide: Peptide side effects

FDA, WADA and Türkiye: what is the legal status?

US: the licensed drug and “research” products

In the US, elamipretide is a licensed drug with an indication for muscle strength in Barth syndrome. ^[1] This does not make SS-31 sold online legal. In a warning letter dated August 24, 2026, the FDA characterized the products of a company selling seven products, including “SS-31 (Elamipretide),” as unapproved new drugs: there was no approved application in effect for these products. According to a footnote of the letter, despite the statements “for research use only” and “not for human or animal consumption” on the product labels, evidence on the website showed that the products were being sold for use as drugs in humans; the company also offered bacteriostatic water and a “peptide calculator” for preparing injections. The FDA stressed that injectable products carry a risk of serious harm because they bypass some of the body’s defense mechanisms. ^[10] The meaning of this label is covered in a separate guide: What does “research peptide” mean?

Sport (WADA)

Elamipretide is not named in the WADA list in effect from January 1, 2026. The S0 section of the list always prohibits substances that are not covered in later sections and that no governmental health authority has approved for human therapeutic use. ^[11] Elamipretide has had an approved product in the US since September 2025; the list has no specific provision on this situation, and the classification of a specific substance is within WADA’s authority.

Türkiye

No product with elamipretide as the active ingredient appears on the TİTCK (Turkish Medicines and Medical Devices Agency) Licensed Human Medicinal Products List dated October 16, 2026. ^[12] Article 19 of Law No. 1262 on Pharmaceutical and Medicinal Preparations (İspençiyari ve Tıbbi Müstahzarlar Kanunu) punishes those who manufacture unlicensed preparations and those who knowingly sell, offer for sale or have them sold with imprisonment of one to five years; importing unlicensed preparations for commercial purposes is treated as smuggling. Additional Article 7 of the Law provides that the Ministry may permit the bringing in of unlicensed preparations for examination, experiment or personal treatment, provided the amount does not exceed the quantity to be accepted by the Ministry; this is a permission mechanism, not a right of free import. ^[13] Under Article 24 of Law No. 6197 on Pharmacists and Pharmacies (Eczacılar ve Eczaneler Hakkında Kanun), medicines cannot be sold on the internet or any other electronic medium. ^[14]

The general legal framework for peptides: Are peptides legal?

Evidence table: claim, population and limits

Limits of this guide

This page summarizes published clinical studies on elamipretide and documents from official bodies. It gives no dose, course, preparation, administration technique or product sourcing information. Barth syndrome and mitochondrial diseases are conditions diagnosed and monitored by specialist physicians; the use of the licensed drug is decided by the physician.