SS-31 (Elamipretide): Mitochondrial Repair Peptide

Introduction

Elamipretide, also known by its research code SS-31, is one of the few peptides with a serious drug-development trajectory in mitochondrial disease. It’s a 4-amino-acid peptide that targets the inner mitochondrial membrane and binds cardiolipin, a phospholipid that’s essential for normal mitochondrial function. The molecule has been in clinical trials since the early 2010s for indications including Barth syndrome, primary mitochondrial myopathy, age-related macular degeneration, and heart failure.

Stealth BioTherapeutics has been the lead developer, with mixed results across programs. Some trials have failed their primary endpoints, others have shown signal in specific subgroups, and a few are still active. Most recently in 2025, the FDA approved elamipretide for Barth syndrome under the brand name Forzinity, making it the first FDA-approved drug for that ultra-rare disease.

This isn’t a mass-market longevity peptide despite how it’s marketed in some peptide community circles. It’s an investigational therapeutic with a real but narrow set of indications.

At TrimRx, we believe that understanding your options is the first step toward a more manageable health journey. You can take the free assessment quiz if you’re ready to see whether a personalized program is a fit for you.

What Is Elamipretide and How Does It Work?

Elamipretide is the peptide D-Arg-2′,6′-dimethylTyr-Lys-Phe-NH2, a four-residue peptide engineered to cross the outer mitochondrial membrane and concentrate in the inner mitochondrial membrane. It binds cardiolipin, a unique double-phosphatidylglycerol lipid that’s almost exclusively found in mitochondrial membranes.

Quick Answer: Elamipretide (SS-31) is a 4-amino-acid peptide that binds cardiolipin on the inner mitochondrial membrane

Cardiolipin is essential for the structural integrity of cristae, the folded inner mitochondrial membrane where electron transport chain complexes sit. With age, oxidative stress, and certain genetic conditions, cardiolipin becomes oxidized or depleted. This destabilizes cristae, impairs electron transport chain assembly, and reduces ATP production while increasing reactive oxygen species generation.

By binding cardiolipin and stabilizing it against oxidation, elamipretide is hypothesized to preserve mitochondrial function in cells where cardiolipin integrity is failing. The mechanism is supported by extensive preclinical work in cardiac, muscle, and retinal tissues.

What Does the Barth Syndrome Data Show?

Barth syndrome is an ultra-rare X-linked disorder caused by mutations in the TAZ gene, which encodes a phospholipid transacylase responsible for cardiolipin maturation. Without normal TAZ function, cardiolipin remodeling fails, mitochondria are dysfunctional, and patients present with cardiomyopathy, skeletal myopathy, neutropenia, and growth delay.

The TAZPOWER trial enrolled 12 adolescent and adult patients with Barth syndrome in a placebo-controlled crossover study, then continued into open-label extension. After 28 weeks of placebo-controlled treatment, the primary endpoint of 6-minute walk distance didn’t meet statistical significance, but the open-label extension showed durable improvements in walk distance and several patient-reported outcomes over 168 weeks.

The FDA approved elamipretide for Barth syndrome in 2025 (now sold as Forzinity) based largely on the open-label extension data and the strong mechanistic rationale, after initial complete response letters. The approval pathway reflects the ultra-rare disease context, fewer than 200 known US patients, and the lack of any alternative therapy.

How Has Elamipretide Performed in Other Indications?

The story is mixed. The MMPOWER-3 trial in primary mitochondrial myopathy (231 patients) failed its primary endpoint of 6-minute walk distance change at 24 weeks. Several secondary endpoints suggested signal, but the trial didn’t support broad approval.

In age-related macular degeneration (AMD), the ReCLAIM and ReCLAIM-2 trials tested elamipretide for non-exudative AMD. Results have been mixed, with some endpoint improvements in dry AMD subgroups but not consistent enough to drive approval to date.

In heart failure with preserved ejection fraction (HFpEF), early phase trials showed potential effects on mitochondrial function biomarkers, but no large efficacy trial has reported positive results. Stealth has been working through different patient subgroups and biomarker-defined populations.

How Is Elamipretide Administered?

In clinical trials, elamipretide is given by once-daily subcutaneous injection, typically 40 mg per day for systemic indications. For ophthalmic indications it’s been formulated as a topical ophthalmic drop. The intramuscular and intravenous routes have also been used in earlier studies.

The peptide is stable enough for refrigerated storage as a solution and has a half-life that supports daily dosing. It’s not orally bioavailable, like most peptides.

In Barth syndrome treatment, ongoing dosing is open-ended given the underlying genetic defect doesn’t resolve. Patients essentially stay on it indefinitely as long as they tolerate it.

What Are the Side Effects?

In clinical trials, elamipretide has been generally well-tolerated. The most common adverse events are injection site reactions, including redness, swelling, and discomfort. Some patients have reported headache, nausea, and fatigue, usually mild and transient.

No serious safety signal has driven program discontinuation in over a decade of clinical development. The injection site reactions are the dominant tolerability issue and can be significant for patients on daily long-term therapy.

For Barth syndrome patients on Forzinity, the labeled warnings include injection site reactions and the potential for hypersensitivity. There’s no major black box warning, which is unusual for a novel mechanism drug and reflects the clean safety database.

Key Takeaway: Mixed clinical trial results in age-related macular degeneration, heart failure, and primary mitochondrial myopathy

Is SS-31 Sold for Longevity Use?

Yes, the peptide community sells SS-31 (the research code rather than the brand name Forzinity) as a research peptide, labeled not for human use. Pricing for research-grade SS-31 runs around $100 to $300 per 10 mg vial.

The marketing claims around longevity uses center on the cardiolipin-stabilization mechanism and assertions that aging itself involves cardiolipin loss. There’s real biology behind that, age-related cardiolipin decline is documented in heart and skeletal muscle. Whether SS-31 in healthy aging adults produces meaningful clinical benefit isn’t established. The clinical trial data in primary mitochondrial disease is at best mixed in younger patients with severe defects.

If you’re considering SS-31 from a peptide vendor for general longevity, you’re using research-grade material at unvalidated doses for an indication that hasn’t been studied in randomized trials. The legitimate medical product is Forzinity, but it’s labeled and priced for an ultra-rare disease, not for general wellness use.

How Does This Compare to Other Mitochondrial Interventions?

Several approaches target mitochondrial function. Coenzyme Q10 supplementation is widely used in mitochondrial disease, with weak but supportive evidence. Nicotinamide riboside and NMN are NAD precursors with active research programs in metabolism and aging. Urolithin A has emerging human data on muscle mitochondrial biogenesis through mitophagy. MOTS-c and other mitochondrial-derived peptides are in earlier research stages.

None of these have the targeted mechanism elamipretide has. None are FDA-approved for any indication. CoQ10 is sold as a supplement and is reasonable to take in mitochondrial disease, but it doesn’t reverse the underlying lipid pathology elamipretide targets.

For general aging support, the evidence base is mixed across all of these. For specific mitochondrial diseases like Barth syndrome, elamipretide is now uniquely the FDA-approved option.

How Does Elamipretide Fit Into Metabolic Health?

This is where the marketing sometimes overreaches. Elamipretide has been studied in heart failure with mixed results, but it isn’t a weight loss drug, isn’t a diabetes drug, and doesn’t have the kind of metabolic outcome data that drives clinical decisions in the obesity and cardiometabolic disease space.

For weight loss and cardiometabolic risk, the GLP-1 class has the strongest data. STEP 1 (Wilding 2021 NEJM) showed 14.9% weight loss with semaglutide. SURMOUNT-1 (Jastreboff 2022 NEJM) showed 20.9% with tirzepatide. SELECT (Lincoff 2023 NEJM) showed 20% MACE reduction in patients with established cardiovascular disease and overweight or obesity.

TrimRx offers a free assessment quiz to see if compounded semaglutide or tirzepatide is appropriate for your situation. That’s the evidence-based path for metabolic health.

What’s the Future of Elamipretide Research?

With Forzinity approval secured for Barth syndrome, Stealth and academic collaborators are continuing work in mitochondrial disease subtypes, age-related macular degeneration, heart failure with biomarker selection, and possibly ischemia-reperfusion injury contexts. The compound has a real mechanism and a long safety track record, so additional indications are plausible but each requires trial work.

Whether elamipretide moves beyond rare disease into broader populations depends on whether biomarker-selected subgroups in common diseases (HFpEF, AMD, perhaps sarcopenia) show large enough effect sizes to justify the development cost and the chronic injection burden.

Bottom line: Self-administration from peptide vendors carries product quality and pharmacokinetic risks

FAQ

Is SS-31 the Same as Elamipretide?

Yes, SS-31 is the research code name, elamipretide is the generic drug name, and Forzinity is the FDA-approved brand for Barth syndrome.

Can I Get Elamipretide for General Longevity?

Not through legitimate prescribing channels. Forzinity is indicated for Barth syndrome. Off-label prescribing for general aging isn’t supported by the evidence base and likely not by insurance. Research peptide vendors sell SS-31 but not for human use.

Did Elamipretide Work in Mitochondrial Myopathy Trials?

The MMPOWER-3 phase 3 trial didn’t meet its primary endpoint of 6-minute walk distance at 24 weeks. Some secondary signals existed but weren’t sufficient for that indication.

Does SS-31 Help with Macular Degeneration?

The ReCLAIM trials showed some signal in non-exudative AMD subgroups but didn’t consistently hit primary endpoints. Development continues in selected subgroups, but no FDA approval for AMD exists.

How Is Forzinity Different From Research-grade SS-31?

Same active molecule, but Forzinity is FDA-approved, GMP-manufactured, sterility-tested, and clinically supervised. Research-grade SS-31 from peptide vendors is sold as a research chemical with no equivalent quality assurances.

What’s the Cost of Forzinity?

Ultra-rare disease pricing, typically six figures per patient per year. The exact list price varies and access is largely through specialty pharmacy with prior authorization for confirmed Barth syndrome diagnosis.

Should I Take SS-31 for Aging?

There’s no strong human evidence that SS-31 improves clinical aging endpoints in healthy adults. The mechanism is plausible, the data isn’t there. If you’re acting on it, you’re betting on extrapolation from mitochondrial disease trials rather than direct evidence.

Disclaimer: This content is for informational purposes only and does not constitute medical advice. It is not intended to diagnose, treat, cure, or prevent any disease or condition. Individual results may vary. Always consult a qualified healthcare professional before starting any weight loss program or medication.