SS-31 (elamipretide, Forzinity): research, side effects and dosage
In short
SS-31, or elamipretide, is a peptide acting on mitochondria that the FDA approved under accelerated approval in the United States only for the rare Barth syndrome [1]regulator. In other diseases large trials did not meet their primary goals [6, 9]A, and there is no marketing authorisation in the EU [12]regulator.
- The FDA approved elamipretide (Forzinity) for Barth syndrome on 19 Sep 2025. The approval rests on muscle strength, an intermediate measure, and a confirmatory trial is under way [1]regulator [13]E, not peer-reviewed.
- Trials in mitochondrial myopathy, heart failure and age-related macular degeneration did not meet their primary goals [6, 7, 9]A.
- Injection site reactions are common, and serious allergic reactions have been reported [2]official.
- The "SS-31 research peptide" sold online is not an approved medicine, and there is no reliable information on its content [10] [15]regulator.
What is SS-31?
SS-31 is a four-amino-acid peptide that belongs to the so-called Szeto-Schiller peptides. These target the inner mitochondrial membrane. SS-31 binds to cardiolipin, a lipid found only in the inner mitochondrial membrane [2]official [3].
As a medicine, SS-31 is called elamipretide, and it has also been studied under the code MTP-131 [2]official [8]A. The elamipretide product approved in the United States (Forzinity) is a sterile solution injected under the skin, containing benzyl alcohol as a preservative [2]official.
According to a review, SS-31 is also marketed directly to patients [10]. The "SS-31 research peptide" sold online is not an approved medicinal product [12]regulator [15]regulator. All substances: Peptides A-Z.
Evidence at a glance
Each cell gives the kind of study and its source. The letter is the evidence level, not the result.
| Claimed effect | Humans | Animals | Cells |
|---|---|---|---|
| Barth syndrome | 12 patients, crossover with placebo: primary goals not met [4]A; in the open extension walking distance increased [5]B | - | - |
| Mitochondrial myopathy | 218 adults, 24 weeks: no difference in walking distance or fatigue [6]A | - | - |
| Heart failure | 71 patients, 4 weeks: no improvement in heart function [7]A | - | - |
| Heart attack | Infusion did not reduce infarct size [8]A | - | - |
| Age-related macular degeneration | 176 patients, 48 weeks: primary goals not met [9]A | - | - |
| Protecting mitochondria | - | Described as protecting mitochondrial structure and energy production in animal studies (review) [3] | - |
| Safety | Injection site reactions common, serious allergic reactions reported [2]official | - | - |
"-" = no such study is known.
What is SS-31 used for?
SS-31 (elamipretide) has one approved indication in the United States: Barth syndrome in patients weighing at least 30 kg. According to the prescribing information, the indication is to improve muscle strength in adults and children with Barth syndrome [1]regulator [2]official.
Barth syndrome is a rare, life-threatening mitochondrial disease that mainly affects boys and men. It often starts with severe heart failure in infancy, and those who survive into adulthood often have fatigue and poor exercise tolerance [1]regulator. It is caused by defects in the TAZ gene, which change the structure of cardiolipin [4]A.
- Other diseases studied: mitochondrial myopathy [6]A, heart failure [7]A, heart attack [8]A and dry age-related macular degeneration [9]A. None of these trials met its primary goal.
Claims online. The claim that it increases stamina and energy is not supported by trials: in a trial of 218 adults, elamipretide did not improve walking distance or fatigue compared with placebo [6]A.
How does SS-31 work?
SS-31 binds to cardiolipin in the inner mitochondrial membrane. In animal studies it has been described as protecting mitochondrial structure and energy production [3].
In Barth syndrome the structure of cardiolipin is changed by a gene defect [4]A. According to the prescribing information, benefit has been shown on an intermediate measure, muscle strength [2]official.
Has SS-31 been studied in humans?
Yes. Elamipretide has been studied in several randomised human trials, but nearly all missed their primary goals [4, 6, 7, 8, 9]A.
Barth syndrome (TAZPOWER)
- Randomised phase. 12 patients received 12 weeks of elamipretide and 12 weeks of placebo in turn. Neither primary goal, a walking test or a symptom questionnaire, was met [4]A. Knee extensor strength did not increase in this phase [2]official.
- Open extension. Without a placebo group, 10 patients entered the extension and 8 were followed to week 168, and the six-minute walking distance increased by 96.1 m on average [5]B. Knee extensor strength increased in the extension [2]official.
- Researchers. Some of the researchers were employees of the manufacturer [4]A [5]B.
Other diseases
- Mitochondrial myopathy (MMPOWER-3). 218 adults received 24 weeks of elamipretide or placebo. The trial did not meet its primary goals: the difference in walking distance from placebo was -3.2 m, and fatigue did not decrease. Elamipretide was well tolerated [6]A.
- Heart failure. In a trial of 71 patients, four weeks of treatment did not improve left ventricular volume or pumping compared with placebo [7]A.
- Heart attack. During balloon angioplasty for ST-elevation myocardial infarction, a one-hour infusion into a vein did not reduce infarct size [8]A.
- Age-related macular degeneration (ReCLAIM-2). 176 patients with dry macular degeneration received 48 weeks of elamipretide or placebo. The primary goals, low-light visual acuity and growth of the lesion area, were not met. On secondary measures, damage to the photoreceptor layer progressed more slowly, but these differences were only nominally significant [9]A.
Who studies SS-31?
In the SS-31 trials in Barth syndrome some of the researchers were employees of the manufacturer [4]A [5]B. The substance has also been studied in mitochondrial myopathy, heart disease and age-related macular degeneration [6, 7, 8, 9]A. The confirmatory trial in Barth syndrome required by the FDA is under way [13]E, not peer-reviewed.
Who wrote this page: the editorial team
This page was written by the Molecular Recovery editorial team. The draft was made with the help of AI, and the claims were checked against the sources (AI policy). The page has not been medically reviewed. How we work: About us.
What are the side effects of SS-31?
The most common harm of SS-31 is an injection site reaction, and serious allergic reactions have been reported [2]official.
What users report. In the Reddit accounts we compiled (not research), 32 of 69 people (46%) reported some harm, most often: fatigue (13, 19%), anxiety or restlessness (4, 6%) and insomnia (4, 6%). People tend to post when something goes wrong, so this share does not tell how common harms are. 40 of 69 people (58%) used other substances at the same time, most often MOTS-c (21), NAD+ (14) and retatrutide (11). So the figures describe use that included SS-31, not SS-31 on its own. The harms in detail: SS-31 user experiences.
Harms in trials and in the label
- In the placebo-controlled phase in Barth patients, injection site reactions occurred in all 12 patients during elamipretide and in 8 of 12 during placebo. The most common were redness, pain, hardening and itching [2]official.
- Hypersensitivity reactions, including serious allergic reactions requiring emergency treatment, have been reported with elamipretide. They may occur within minutes to months after starting treatment [2]official. The FDA says serious reactions have also been reported [1]regulator.
- Blood eosinophil counts rose frequently [2]official.
- In the macular degeneration trial, adverse events were reported by 86% of those given elamipretide and 71% of those given placebo, most commonly injection site reactions [9]A.
SS-31 sold online
There are no data on the harms of "SS-31" sold online, because the content of such products is not known. According to Fimea, impurities such as endotoxins in injectable products raise the risk of serious health hazards [15]regulator. More: Side effects and safety.
Interactions and who lacks data
According to the prescribing information, the dose is lower in severe kidney impairment [2]official. The approval covers only Barth patients weighing at least 30 kg, so there is no approved information for other patient groups [1]regulator. According to the prescribing information, elamipretide did not inhibit the main drug-metabolising liver enzymes (CYP) in laboratory tests, and in humans it did not change the effect of aspirin, clopidogrel or heparin [2]official. There are no human data on pregnancy or breastfeeding, because Barth syndrome mainly affects males [2]official.
What speaks against it and what is unknown
Nearly all randomised trials missed their primary goals, including the randomised phase in Barth syndrome [4, 6, 7, 8, 9]A.
Contrary evidence
- In the randomised phase of TAZPOWER the primary goals were not met [4]A. The approval rests on knee extensor strength, an intermediate measure [1]regulator [2]official.
- In mitochondrial myopathy the difference in walking distance from placebo was -3.2 m [6]A.
- No benefit was seen in heart failure or heart attack [7, 8]A.
- In age-related macular degeneration the primary goals were not met [9]A.
What the evidence does not support
- "SS-31 is an approved medicine, so SS-31 from the internet is safe": the approval covers the Forzinity product for Barth syndrome [1]regulator [2]official. According to a review, the grey market for unapproved peptides operates largely outside regulatory oversight [10].
- "SS-31 increases stamina and energy": this has not been shown [6, 7]A.
- "The Barth syndrome approval rests on a clear benefit": it rests on an intermediate measure, and the FDA requires a confirmatory trial [1]regulator [2]official [4]A.
- "SS-31 is harmless": injection site reactions occurred in all 12 Barth patients given elamipretide, and serious allergic reactions have been reported [2]official.
It is not known whether the benefit in Barth syndrome will be confirmed, or what online "SS-31" contains [10] [13]E, not peer-reviewed [15]regulator.
SS-31 dosage in studies and in the label
Elamipretide has an approved dosage in the United States for Barth syndrome, but no marketing authorisation in the EU [2]official [12]regulator. Below are the dose in the US prescribing information and the doses used in trials. They are not advice; use of the approved product is decided by a doctor.
| Study | Who | Dose and route | Duration |
|---|---|---|---|
| Forzinity, US prescribing information | Barth syndrome, weight at least 30 kg | 40 mg under the skin once a day; 20 mg in severe kidney impairment | duration not stated [2]official |
| TAZPOWER (2021) | 12 Barth patients | 40 mg under the skin once a day | 12 weeks plus 12 weeks of placebo [4]A |
| TAZPOWER extension (2024) | 10 Barth patients (8 to week 168) | 40 mg under the skin once a day | 168 weeks [5]B |
| MMPOWER-3 (2023) | 218 adults, mitochondrial myopathy | 40 mg under the skin once a day | 24 weeks [6]A |
| PROGRESS-HF (2020) | 71 heart failure patients | 4 mg or 40 mg once a day | 28 days [7]A |
| EMBRACE STEMI (2016) | heart attack patients | 0.05 mg/kg per hour into a vein | 1 hour [8]A |
| ReCLAIM-2 (2025) | 176 macular degeneration patients | 40 mg under the skin once a day | 48 weeks [9]A |
What the numbers do not tell you. The label dose applies to the approved sterile product in Barth patients, not to powder bought online [2]official [15]regulator. More: SS-31 dosage. The calculator has no SS-31 preset, because the approved product is a ready-to-use solution whose dose is set by the doctor.
Situation in the United States
On 19 Sep 2025 the FDA granted accelerated approval to elamipretide (Forzinity) for Barth syndrome in patients weighing at least 30 kg [1]regulator.
The approval rests on improved knee extensor muscle strength, which the FDA considers reasonably likely to predict benefit but which does not directly measure patient benefit. Continued approval may depend on a confirmatory trial [1]regulator [2]official.
Is SS-31 legal in Finland?
SS-31 (elamipretide) has no marketing authorisation in the EU, although it holds an orphan designation [11, 12]regulator.
- Orphan designation. Elamipretide has held an EU orphan designation for Barth syndrome since 20 May 2021, but according to EMA the designation does not mean the medicine is available or authorised [11]regulator.
- Marketing authorisation. On 12 Oct 2026 the EMA data on centrally authorised medicines contained no elamipretide [12]regulator, and the EMA Article 57 database, which must list every human medicine authorised in the EU and EEA, had no elamipretide product in any country (data as of 21 Sep 2026) [16]regulator.
- Fimea warning, 29 June 2026. Fimea warned about injectable peptides bought online and advises buying medicines only from legal pharmacies. According to Fimea, a "for research use only" label means the product is not intended for humans [15]regulator.
- Import. Ordering medicines from outside the EU is covered on Peptides and the law in Finland.
This is not legal advice. Disclaimer.
Is SS-31 doping?
Probably not, but this is not certain. The WADA 2026 Prohibited List does not name elamipretide or SS-31. Class S0 prohibits substances with no approval by any government health authority for human therapeutic use [14]regulator. The FDA has approved elamipretide for Barth syndrome [1]regulator, so by its wording S0 does not appear to apply. Athletes should confirm with their national anti-doping organisation before use.
How is an SS-31 product assessed?
The approved elamipretide product (Forzinity) is an FDA-approved sterile solution in single-patient vials [1]regulator [2]official. There is no comparable information on the "SS-31 research peptide" sold online, and according to a review the grey market for unapproved peptides operates largely outside regulatory oversight [10].
According to Fimea, an unauthorised product may contain a different substance than the packaging states, and for injectables endotoxins are a particular risk [15]regulator. A seller's own certificate of analysis (COA) does not by itself show that a product is pure or sterile. More: How to read a COA and check a test result.
The future: what comes next?
The 72-week placebo-controlled confirmatory SS-31 trial in Barth syndrome required by the FDA (4TAZPower) started on 2 Jul 2026 and was recruiting on 12 Oct 2026 [1]regulator [13]E, not peer-reviewed. Continued US approval may depend on the confirmatory trial [1]regulator [2]official.
FAQ
What is SS-31?
A four-amino-acid peptide that binds to cardiolipin in the inner mitochondrial membrane. As a medicine it is called elamipretide [2]official [3].
Is SS-31 an approved medicine?
Partly. In the United States, elamipretide (Forzinity) has accelerated approval only for Barth syndrome in patients weighing at least 30 kg [1]regulator. It has no marketing authorisation in the EU [12]regulator.
Is SS-31 sold online the same as the elamipretide medicine?
No. The approved medicine is an FDA-approved product [1]regulator [2]official, whereas there is no reliable information on the content and quality of products sold online [10] [15]regulator.
Does SS-31 increase stamina?
This has not been shown. In a trial of 218 adults, elamipretide did not improve walking distance or fatigue compared with placebo [6]A.
What is known about the side effects of SS-31?
The most common are injection site reactions, and serious allergic reactions have been reported. Rises in blood eosinophils have also been seen [2]official [9]A.
What doses did SS-31 trials use?
Most trials used 40 mg under the skin once a day [4, 6, 9]A. This is not dosing guidance: dosage in studies. Use of the approved product is decided by a doctor [2]official.
Is SS-31 legal in Finland?
Elamipretide has no marketing authorisation in the EU [12]regulator. This is not legal advice.
Is SS-31 a doping substance?
Probably not, but this is not certain. The Prohibited List does not name elamipretide or SS-31, and class S0 covers only substances that no authority has approved [14]regulator. The FDA has approved elamipretide [1]regulator. Athletes should confirm with their national anti-doping organisation.
What do users themselves report about SS-31?
In the Reddit accounts of 69 people we compiled (not research), 44 (64%) reported some benefit and 32 (46%) some harm. The accounts are self-selected and prove neither that it works nor that it is safe: SS-31 user experiences.
Read the research yourself: sources
Every source opens the original publication or the regulator's page. The level shows what the source itself reports.
- U.S. Food and Drug Administration. FDA Grants Accelerated Approval to First Treatment for Barth Syndrome. Press announcement, 19 Sep 2025. FDA regulator
- U.S. Food and Drug Administration. FORZINITY (elamipretide) injection, prescribing information, NDA 215244 (revised 9/2025). FDA (Drugs@FDA) official
- Szeto HH. First-in-class cardiolipin-protective compound as a therapeutic agent to restore mitochondrial bioenergetics. Br J Pharmacol. 2014;171:2029-50. PMID 24117165 (review)
- Reid Thompson W, Hornby B, Manuel R, et al. A phase 2/3 randomized clinical trial followed by an open-label extension to evaluate the effectiveness of elamipretide in Barth syndrome, a genetic disorder of mitochondrial cardiolipin metabolism. Genet Med. 2021;23:471-478. PMID 33077895 A
- Thompson WR, Manuel R, Abbruscato A, et al. Long-term efficacy and safety of elamipretide in patients with Barth syndrome: 168-week open-label extension results of TAZPOWER. Genet Med. 2024;26:101138. PMID 38602181 B
- Karaa A, Bertini E, Carelli V, et al. Efficacy and Safety of Elamipretide in Individuals With Primary Mitochondrial Myopathy: The MMPOWER-3 Randomized Clinical Trial. Neurology. 2023;101:e238-e252. PMID 37268435 A
- Butler J, Khan MS, Anker SD, et al. Effects of Elamipretide on Left Ventricular Function in Patients With Heart Failure With Reduced Ejection Fraction: The PROGRESS-HF Phase 2 Trial. J Card Fail. 2020;26:429-437. PMID 32068002 A
- Gibson CM, Giugliano RP, Kloner RA, et al. EMBRACE STEMI study: a Phase 2a trial to evaluate the safety, tolerability, and efficacy of intravenous MTP-131 on reperfusion injury in patients undergoing primary percutaneous coronary intervention. Eur Heart J. 2016;37:1296-303. PMID 26586786 A
- Ehlers JP, Hu A, Boyer D, et al. ReCLAIM-2: A Randomized Phase II Clinical Trial Evaluating Elamipretide in Age-related Macular Degeneration, Geographic Atrophy Growth, Visual Function, and Ellipsoid Zone Preservation. Ophthalmol Sci. 2025;5:100628. PMID 39605874 A
- Mendias CL, Awan TM. Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance. Sports Med. 2026;56:1921-1935. PMID 41966639 (review)
- European Medicines Agency. EU/3/21/2430: orphan designation for treatment of Barth syndrome (elamipretide), designated 20 May 2021. EMA regulator
- European Medicines Agency. Medicine data (data set of 12 Oct 2026): no medicine with elamipretide. EMA regulator
- ClinicalTrials.gov. NCT07531251: Clinical Trial in Patients With Barth Syndrome (4TAZPower), phase 3b/4, status recruiting (record updated 17 Sep 2026). ClinicalTrials.gov E, not peer-reviewed
- World Anti-Doping Agency. The 2026 Prohibited List, class S0 Non-approved substances (in effect from 1 Jan 2026). WADA regulator
- Fimea. Fimea warns: do not use injectable peptides purchased online (29 Jun 2026). Fimea regulator
- European Medicines Agency. Article 57 product data (EMA/518502/2018 Rev.89, data as of 21 Sep 2026): no product with elamipretide in any EU/EEA country. EMA regulator
Sources checked 12 Oct 2026. The study substance MTP-131 in source 8 is elamipretide: its chemical name is the same as in the prescribing information.
Evidence levels: A = randomised human trial or meta-analysis · B = observational human study or case series · C = animal study · D = cell or laboratory study · E = not peer-reviewed · regulator = a regulator's assessment or decision, not research evidence. The marker official means official product information (summary of product characteristics or label); it is not research evidence. For a review, the level shows what kind of research the statement rests on. No level: statements that something has not been studied, reviews' interpretations, named hypotheses and the general rules in our certificate-of-analysis guide.
Content is general information about research, not medical advice. If you have symptoms, contact a healthcare professional.