Elamipretide

What is Elamipretide?

Elamipretide is a cationic, water-soluble tetrapeptide (D-Arg-2',6'-dimethylTyr-Lys-Phe-NH2) that concentrates at the inner mitochondrial membrane, where it binds cardiolipin and stabilizes the structural architecture required for efficient oxidative phosphorylation. Developed by Stealth BioTherapeutics, it received FDA accelerated approval in September 2024 under the brand name Forzinity for the treatment of Barth syndrome in adult and pediatric patients weighing at least 30 kg — the first mitochondria-targeted peptide ever to clear FDA review. Barth syndrome is an X-linked disorder of cardiolipin remodeling affecting roughly 150 individuals in the United States, characterized by cardiomyopathy, skeletal myopathy, neutropenia, and growth delay. It is important to note that elamipretide is chemically identical to the research-grade peptide widely known as SS-31; the two names refer to the same molecule at different stages of its regulatory life. This entry focuses on the approved-drug context — label, indication, access, pricing — while the broader clinical-development story and off-label discussion live on the SS-31 page.

History & Discovery

Elamipretide's scientific origin is the Szeto-Schiller peptide program at Cornell University in the late 1990s and early 2000s, where Hazel Szeto and Peter Schiller systematically engineered small cationic peptides that could penetrate cell membranes and concentrate in mitochondria without depending on membrane potential. SS-31 — the fourth generation of that series — distinguished itself by its ability to bind cardiolipin on the inner mitochondrial membrane with unusual selectivity, independent of the mitochondrial membrane potential that had limited earlier triphenylphosphonium-based targeting strategies. Stealth BioTherapeutics (originally Stealth Peptides) licensed the molecule and advanced it through clinical development under multiple names — Bendavia for cardiovascular indications, MTP-131 in early trial documentation, and ultimately elamipretide as the International Nonproprietary Name. The program's regulatory arc spanned more than a decade: EMBRACE-STEMI in acute ST-elevation myocardial infarction missed its primary endpoint, PROGRESS-HF in heart failure with reduced ejection fraction was negative, ReCLAIM and ReNEW in dry age-related macular degeneration failed, and MMPOWER-3 in broader primary mitochondrial myopathy missed its primary endpoint despite signals in genotype-defined subgroups. The Barth syndrome program — TAZPOWER and its 168-week open-label extension, paired with an EMBRACE natural-history-controlled comparison in pediatric and adolescent patients — produced the package that ultimately persuaded the FDA. Regulatory review was itself protracted: Stealth received a Complete Response Letter in 2021 and a second in 2023, and the final accelerated approval for Forzinity on September 20, 2024 made elamipretide the first FDA-approved mitochondria-targeted peptide and, in a broader sense, the first drug ever approved specifically for Barth syndrome. Confirmatory studies are required under the accelerated-approval commitment.

How It Works

Elamipretide is a small peptide that homes to the inner membrane of your cells' mitochondria — the powerhouses that make cellular energy. Once there, it binds to cardiolipin, a lipid that holds the energy-producing machinery in the right shape. By stabilizing cardiolipin, elamipretide helps mitochondria run more efficiently and produce less oxidative damage. In Barth syndrome, a genetic defect in cardiolipin metabolism causes heart and muscle dysfunction, which is why this mechanism is a particularly close match for the disease.

Elamipretide is chemically identical to the research peptide SS-31, a 4-residue cationic peptide developed in the Szeto-Schiller program at Cornell. Its distinguishing pharmacological property is selective, voltage-independent binding to cardiolipin on the matrix-facing leaflet of the inner mitochondrial membrane. Cardiolipin is a dimeric phospholipid unique to mitochondria (and bacterial membranes) that organizes the supercomplexes of Complex I, III, and IV of the electron transport chain and maintains the tight cristae curvature required for efficient ATP synthesis. By binding cardiolipin, elamipretide (i) preserves cristae architecture, (ii) stabilizes electron transport chain supercomplexes, improving electron flux and ATP synthesis, and (iii) reduces generation of reactive oxygen species by limiting electron leak. It also prevents peroxidation of cardiolipin itself — a cardinal early event in mitochondrial dysfunction across many disease contexts. Barth syndrome is caused by loss-of-function mutations in TAFAZZIN (TAZ), the gene encoding tafazzin, a phospholipid-remodeling acyltransferase. Loss of tafazzin activity leads to immature, monolyso-cardiolipin-enriched membranes, disorganized cristae, and impaired oxidative phosphorylation — producing cardiomyopathy, skeletal myopathy, growth delay, and cyclic neutropenia. Because elamipretide acts directly on cardiolipin architecture, the mechanistic match to Barth biology is unusually direct, which underpins the accelerated-approval rationale where earlier heart-failure and dry-AMD programs (PROGRESS-HF, ReCLAIM, ReNEW) did not produce convincing benefit and MMPOWER-3 in broader primary mitochondrial myopathy missed its primary endpoint.

Use Cases & Evidence Levels

Evidence Snapshot

Research Gaps & Open Questions

What the current literature has not yet settled about Elamipretide:

• 01Confirmatory clinical benefit — as an accelerated-approval drug, Forzinity's post-marketing confirmatory studies are a material part of its evidentiary story. Outcomes of those studies over the next several years will determine whether full approval is granted or whether the indication is narrowed or withdrawn.
• 02Pediatric access below 30 kg — weight-adjusted dosing was studied but is not currently part of the approved label; pathways to extend labeling to younger Barth patients are an open question.
• 03Long-term safety beyond the 168-week extension — larger populations and longer exposures are needed to characterize rare adverse events.
• 04Cardiac imaging and biomarker endpoints — the heterogeneity of Barth cardiomyopathy and the small patient population mean endpoint validation remains an ongoing area of work.
• 05Broader mitochondrial disease indications — whether subgroup signals in MMPOWER-3 or new formulations might eventually support label expansion beyond Barth syndrome is not resolved.
• 06Non-Barth and healthy-population use — despite marketing adjacent to 'mitochondrial support' in the research-chemical and longevity space, there are no controlled trials of elamipretide in healthy adults supporting any longevity or anti-aging claim.

Forms & Administration

Forzinity is supplied as a lyophilized powder for reconstitution into an aqueous solution for daily subcutaneous injection. The label provides a 40 mg daily dose for adult and pediatric Barth patients ≥30 kg. Administration is performed at home by patients or caregivers after training, using subcutaneous injection sites that rotate across the abdomen, thigh, and upper arm to minimize local reactions. All injectable peptides should only be administered under the guidance of a qualified healthcare provider. Never self-administer without clinician oversight.

Dosing & Protocols

The ranges below reflect protocols commonly discussed in the literature and by clinicians — not a prescription. Actual dosing for any individual should be determined by a qualified healthcare provider who knows the patient.

Dosing information reflects the FDA-approved Barth syndrome label. Use of elamipretide or SS-31 outside this indication is off-label and is not supported by the approved evidence base.

Timeline of Effects

Common Questions

Who Elamipretide Is NOT For

Drug & Supplement Interactions

Elamipretide has a relatively limited published drug-interaction profile, in part because it is cleared by peptidase-mediated degradation rather than hepatic CYP metabolism. The approval package did not flag major CYP-based interactions. In Barth syndrome clinical experience, patients are commonly on cardiac medications including beta-blockers, ACE inhibitors, and diuretics; these have been used alongside elamipretide in trials without signals of clinically meaningful interaction. Granulocyte colony-stimulating factor and growth hormone — both used in selected Barth patients — have also been used concomitantly in the development program. Patients and caregivers should disclose all concurrent medications, supplements, and compounded products to the prescribing specialist, who will coordinate with a specialty pharmacy as part of Forzinity initiation.

Safety Profile

Legal Status

Regulatory status changes over time. Verify current local rules with a qualified professional.

Myths & Misconceptions