Stealth BioTherapeutics Advances First FDA-Approved Mitochondrial Therapy FORZINITY for Barth Syndrome
Key Insights
FORZINITY (search) (elamipretide) injection became commercially available following FDA accelerated approval in September 2025 as the first treatment for Barth syndrome (search) and first mitochondria-targeted therapeutic.
Early prescriber demand for the ultra-rare disease treatment has exceeded company expectations, with diagnostic code usage suggesting patient prevalence may be higher than estimated 150 U.S. individuals.
Stealth BioTherapeutics (search) plans FDA meetings in early 2026 to expand treatment access to younger BTHS patients and advance development for primary mitochondrial disease (search).
Stealth BioTherapeutics (search) has achieved a significant milestone in rare disease treatment with the commercial launch of FORZINITY (search) (elamipretide) injection, marking the first FDA-approved therapy for Barth syndrome (search) and the inaugural mitochondria-targeted therapeutic to reach the market. The company reported strong early demand that has exceeded expectations as it prepares for formal launch in the second quarter of 2026.
Commercial Launch Exceeds Expectations
FORZINITY (search) received accelerated approval from the FDA on September 19, 2025, for improving muscle strength in children and adults weighing at least 30 kg with Barth syndrome (search). Commercial supply became available in late November 2025, with AnovoRx Specialty Pharmacy (search) beginning prescription fulfillment in December 2025.
"Since receiving accelerated approval for FORZINITY (search) in September, we've built a robust commercial foundation and are working closely with prescribers and payers to ensure access for eligible patients with Barth syndrome (search)," said Reenie McCarthy, Chief Executive Officer of Stealth BioTherapeutics (search).
Early prescriber data reveal promising market dynamics, with diagnostic code usage for BTHS suggesting patient prevalence may meaningfully exceed the estimated 150 U.S. individuals known to be affected by the condition. The company has engaged with pharmacy benefit providers covering over 40% of U.S. lives to support access and reimbursement, while launching Mito Assist, a patient support program to coordinate treatment journeys.
Expanding Access and Pipeline Development
Stealth plans to meet with the FDA in early 2026 to discuss regulatory pathways for younger BTHS patients who do not meet the current 30 kg weight threshold. The company continues providing uninterrupted elamipretide access through its expanded access program for younger patients and is on track to initiate the FDA-required post-marketing trial during the first half of 2026.
Primary Mitochondrial Disease Development
The company is pursuing primary mitochondrial disease (search) due to polymerase gamma and other nDNA mutations (nPMD) as a potential next indication for elamipretide. FDA discussions planned for early 2026 will outline development strategies for this rare disease population.
Dry AMD and Pipeline Advances
Stealth's fully-enrolled Phase 3 ReNEW clinical trial of elamipretide for dry age-related macular degeneration (search) is expected to read out in late 2027. Additionally, an eye drop formulation of bevemipretide, the company's next-in-class clinical-stage compound, is in Phase 1 development for dry AMD, with Phase 2 initiation targeted by year-end 2026.
Systemic bevemipretide has demonstrated neuroprotective effects in Parkinson's disease (search) preclinical studies supported by the Michael J Fox Foundation, with the company evaluating next development steps for this and other pipeline compounds targeting mitochondrial dysfunction.
Addressing Ultra-Rare Disease Burden
Barth syndrome (search) represents an ultra-rare genetic condition characterized by mitochondrial abnormalities leading to muscle weakness, exercise intolerance, debilitating fatigue, heart failure, recurrent infections, and delayed growth. The disease carries significant mortality risk, with 85% of early deaths occurring by age 5. BTHS occurs primarily in males and affects an estimated one in 1,000,000 male births.
FORZINITY (search)'s approval was based on improvement in knee extensor muscle strength, an intermediate clinical endpoint, under the FDA's accelerated approval pathway. The drug functions as a mitochondrial cardiolipin (search) binder and is contraindicated in patients with serious hypersensitivity to elamipretide. The most common adverse reactions are injection site reactions, with hypersensitivity reactions requiring monitoring during treatment.
The therapy's commercial availability represents a breakthrough for patients with Barth syndrome (search), who previously had no EMA-approved treatment options. As Stealth continues expanding its mitochondria-targeted therapeutic platform, the company aims to address urgent unmet needs across rare and age-related diseases involving mitochondrial dysfunction.