Yes, for one disease. FDA granted Forzinity accelerated approval in September 2025 for Barth syndrome, in patients weighing 30 kg or more, on knee extensor strength . A confirmatory randomized trial is required as a condition . Nothing else is approved. A research vial labelled SS-31 is not Forzinity, and none of the trial evidence attaches to it.

SS-31: uses, evidence and status | Inside Your Peptides

compound file

The answer, first. A four-amino-acid mitochondria-targeting peptide that binds cardiolipin in the inner mitochondrial membrane, developed as elamipretide and taken through registered clinical trials by Stealth BioTherapeutics. The strongest evidence is for Barth syndrome, graded A — approval or replicated trials.

FDA granted accelerated approval in September 2025 for patients weighing at least 30 kg, on improved knee extensor strength ⁹. The randomized crossover in 12 patients missed both primary endpoints ².

The gains came from the open-label extension ²³. The rest of what it is sold for — healthy aging and physical function, primary mitochondrial myopathy, dry age-related macular degeneration, heart failure with reduced ejection fraction — grade D or E: animal or mechanism data only, or a claim the human trials have already tested and not supported.

What it is used for

Every use graded on its own evidence, not the compound as a whole. 6 outcomes, ranked by what the human record supports.

#outcome · human · animal · gradewhat the best evidence actually shows

01Barth syndromephase 2/3 crossover plus extension, approved · supportivegrade AFDA granted accelerated approval in September 2025 for patients weighing at least 30 kg, on improved knee extensor strength ⁹. The randomized crossover in 12 patients missed both primary endpoints ². The gains came from the open-label extension ²³.

02Mitochondrial energy in aging muscleone randomized crossover, 39 adults · aged micegrade COne 2-hour infusion raised in-vivo muscle ATPmax in 39 adults aged 60 to 85 against placebo [p=0.045], and the effect was gone by day 7 ⁶. Fatigue resistance did not change ⁶.

03Healthy aging and physical functionphase 2 recruiting, no results · aged micegrade DA single dose restored mitochondrial ATP production, coupling and cell energy state to young levels in aged mice within one hour ⁷. Eight days of dosing raised endurance ⁷. A 30-person healthy-aging phase 2 is recruiting ¹¹.

04Primary mitochondrial myopathyphase 3, 218 randomized · positive rodent workgrade EThe phase 3 killed this one. 218 adults received 40 mg daily for 24 weeks ¹. Six-minute walk distance differed from placebo by -3.2 metres [95% CI -18.7 to 12.3, p=0.69], and fatigue did not move ¹.

05Dry age-related macular degenerationphase 2, 176 randomized · cell and animal retina workgrade EThe trial missed what it set out to show. In 176 patients over 48 weeks, low-luminance visual acuity and geographic atrophy growth both failed ⁴. A nominal secondary, 43% less ellipsoid zone loss, is now a phase 3 endpoint ⁴.

06Heart failure with reduced ejection fractiontwo randomized trials · dog and rodent workgrade ETwo randomized trials found nothing durable. In 71 patients, 28 days of 4 or 40 mg daily did not change left ventricular end systolic volume against placebo ⁵. An earlier single-infusion study showed a transient change only ¹⁰.

gradewhat it means

ARegulatory approval, or multiple adequately-powered trials agreeing with each other

BAt least one well-powered human randomised trial, with the direction replicated

CSmall or open-label human trials only

DAnimal or mechanism data only, with no controlled human outcome

EA claim the human trials have already killed

How it works

The proposed mechanism, in three steps. A mechanism is a reason to run a trial, never a substitute for one.

1targetElamipretide concentrates in the inner mitochondrial membrane and binds cardiolipin, the phospholipid that organises the respiratory chain ⁸.

2signalCardiolipin binding stabilises cristae structure and restores electron transport coupling, cutting hydrogen peroxide leak ⁸.

3effectATP production rises in damaged mitochondria and stays unchanged in healthy ones, in aged mice and in older human muscle ⁶⁷.

What it does not do

Claims the current record does not support. Worth knowing before you set expectations.

not supported by the evidence

It improves walking and fatigue in mitochondrial disease. A phase 3 in 218 adults returned Class I evidence of no effect on six-minute walk or fatigue at 24 weeks ¹.
It reverses heart failure. Twenty-eight days at either dose did not change left ventricular volumes in 71 randomized patients ⁵.
It is approved as an anti-aging drug. The approval covers Barth syndrome at 30 kg and above, under accelerated approval on a strength endpoint, with a confirmatory trial required ⁹.
A research vial is the trial drug. Every result on this page used a manufactured product with a released specification. A research vial carries no such assurance.

How it is used

What published protocols administered, and what the community reports doing. Descriptive on both counts, and never a recommendation.

routeSubcutaneous injection once daily in the approved product and in most trials. Some trials used intravenous infusion or a topical eye drop.

formatSolution for subcutaneous injection as the approved product. Research vials are lyophilised powder.

published dosesThe registered trials dosed 40 mg subcutaneously once daily: 24 weeks in mitochondrial myopathy ¹, 12-week crossover periods in Barth syndrome ², 48 weeks in dry AMD ⁴. The heart failure trial tested 4 mg and 40 mg daily for 28 days ⁵. The approved product is once-daily subcutaneous ⁹.

human pharmacokineticsShort. A single infusion raised muscle ATPmax immediately and the effect had gone by day 7, consistent with rapid clearance ⁶.

reported conventionsAs reported on longevity forums, 2021-2026: a daily subcutaneous amount well below the 40 mg used in the trials, run in blocks of several weeks. Reports are few, and cost visibly shapes what gets described. Convention, not guidance.

commonly paired withMOTS-c NAD+

This site does not publish protocols to follow. The doses above are what studies administered or what users report, stated as facts about the literature and the market. How protocols are structured, mixing and storage and the reconstitution calculator cover the arithmetic.

What to expect

Where a trial measured it, the trial. Where only the community reports it, that is said out loud.

onsetImmediate where it has been measured. Muscle ATPmax rose straight after a 2-hour infusion in 39 older adults and was back at baseline by day 7 ⁶. The Barth syndrome strength and walking gains needed 36 weeks of daily dosing before they appeared ².

most common reportIn the registered trials the modal result was a null on the primary endpoint. As reported: nothing dramatic, and injection site irritation.

adverse effectsInjection site reactions dominate. In the dry AMD trial adverse events were reported by 86% on elamipretide against 71% on placebo, mostly injection site itching, pain, bruising and redness ⁴. FDA notes serious reactions have also been reported ⁹.

the stop signalIn the trials, dosing stopped at a fixed protocol endpoint. FDA requires a confirmatory randomized trial for continued approval, so the stopping question here is regulatory rather than personal ⁹.

Approval and status

What regulators and sport bodies have actually said, separately from what the evidence shows.

approvalApproved in the US as Forzinity for Barth syndrome, September 2025.

FDAAccelerated approval on knee extensor strength in patients 30 kg and over. A confirmatory randomized trial is required.

sport [WADA]Not named on the 2026 List. S0 no longer applies now it is approved.

sold asresearch chemical

Check the vial

The grade above describes a molecule studied under controlled conditions. It says nothing about the powder in a particular vial.

That gap is the one part of this market a reader can actually close. How to read a certificate of analysis covers the five measures in five minutes, and the 2026 audit grades vendors on the documents they publish against a rubric printed in full.

Questions we get

What is SS-31 used for?

One approved use and a long list of failed ones. It is approved in the US for Barth syndrome, on a knee extensor strength endpoint, in patients 30 kg and over ⁹.

Trials in primary mitochondrial myopathy ¹, dry age-related macular degeneration ⁴ and heart failure ⁵ all missed their primary endpoints. It is sold as a research chemical for mitochondrial energy and aging, which is not an approved use.

How is SS-31 used?

Descriptively, and not as guidance: subcutaneous injection once daily, which is both the approved schedule and the schedule of most trials ⁹. The trials dosed 40 mg daily, for 24 to 48 weeks depending on the study ¹²⁴.

Community reports describe amounts well below that, run in blocks of weeks. The single-dose muscle study used a 2-hour intravenous infusion ⁶.

How long does SS-31 take to work?

It depends entirely on the endpoint. Mitochondrial ATP production in older muscle rose immediately after one infusion and was gone by day 7 ⁶.

Barth syndrome walking and strength gains took 36 weeks of daily dosing to reach significance, and only in the open-label phase ². Nothing in the record supports a felt effect on any timescale.

Is SS-31 approved?

Yes, for one disease. FDA granted Forzinity accelerated approval in September 2025 for Barth syndrome, in patients weighing 30 kg or more, on knee extensor strength ⁹.

A confirmatory randomized trial is required as a condition ⁹. Nothing else is approved. A research vial labelled SS-31 is not Forzinity, and none of the trial evidence attaches to it.

Did the big trials work?

Mostly no, and that is the honest core of this file. The phase 3 in 218 adults with mitochondrial myopathy missed both primaries ¹. The Barth syndrome crossover missed both primaries before the open-label extension produced the gains that carried the approval ²³.

The dry AMD phase 2 missed both primaries ⁴. Heart failure showed no change at 28 days ⁵.

References

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
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. Genet Med. 2021;23:471-478. PMID 33077895
Thompson WR, Hornby B, Reid Thompson W, 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
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
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
Roshanravan B, Liu SZ, Ali AS, et al. In vivo mitochondrial ATP production is improved in older adult skeletal muscle after a single dose of elamipretide in a randomized trial. PLoS One. 2021;16:e0253849. PMID 34264994
Siegel MP, Kruse SE, Percival JM, et al. Mitochondrial-targeted peptide rapidly improves mitochondrial energetics and skeletal muscle performance in aged mice. Aging Cell. 2013;12:763-771. PMID 23692570
Birk AV, Liu S, Soong Y, et al. The mitochondrial-targeted compound SS-31 re-energizes ischemic mitochondria by interacting with cardiolipin. J Am Soc Nephrol. 2013;24:1250-1261. PMID 23813215
US Food and Drug Administration. FDA grants accelerated approval to first treatment for Barth syndrome. Press announcement, 19 September 2025. fda.gov
Daubert MA, Yow E, Dunn G, et al. Novel mitochondria-targeting peptide in heart failure treatment: a randomized, placebo-controlled trial of elamipretide. Circ Heart Fail. 2017;10:e004389. PMID 29217757
ClinicalTrials.gov. Study of healthy aging and physical function with elamipretide, NCT07275424. Phase 2, 30 participants, recruiting. Accessed 24 Aug 2026. clinicaltrials.gov

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