Stealth BioTherapeutics Provides Commercial and R&D Pipeline Update and Outlines 2026 Strategic Priorities

FORZINITY™ now commercially available following U.S. Food and Drug Administration (FDA) accelerated approval for Barth syndrome (BTHS)

FDA engagement planned to advance development for younger BTHS and primary mitochondrial disease (PMD) patients; dry age-related macular degeneration (AMD) development efforts progressing

NEEDHAM, Mass., Jan. 6, 2026 /PRNewswire/ -- Stealth BioTherapeutics Inc. (the "Company" or "Stealth"), a commercial-stage biotechnology company focused on the discovery, development and commercialization of novel therapies for diseases involving mitochondrial dysfunction, today provided an update on the Company's commercial and R&D progress and highlighted 2026 strategic priorities.  

"Since receiving accelerated approval for FORZINITY 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," said Reenie McCarthy, Chief Executive Officer of Stealth BioTherapeutics. "As we continue development efforts for younger affected individuals as well as for individuals living with primary mitochondrial disease and dry AMD, we remain committed to accelerating innovation across our pipeline to address urgent unmet needs in rare and age-related diseases of mitochondrial dysfunction."

Commercial Update:

FORZINITY is currently commercially available for eligible US patients living with BTHS, a rare, serious and life-threatening mitochondrial disease.

• On September 19, 2025, FORZINITY (elamipretide) injection received accelerated approval from the FDA as the first treatment to improve muscle strength for children and adults weighing at least 30 kg (approximately 66 pounds) with BTHS (eligible patients).
• FORZINITY commercial supply was available in late November 2025 and AnovoRx Specialty Pharmacy, the exclusive US specialty pharmacy, began filling prescriptions in December 2025.
• Ahead of formal launch next quarter, early demand from prescribers for eligible US patients, including those previously receiving elamipretide through the Company's expanded access program (EAP), has exceeded the Company's expectations.
• Preliminary prescriber data suggest that diagnostic code usage for BTHS, known to affect approximately 150 U.S. individuals, may meaningfully exceed U.S. patient prevalence estimates.
• The Company has engaged with pharmacy benefit providers covering over 40% of US lives to provide education in support of access and reimbursement for FORZINITY and has launched Mito Assist™, a voluntary, patient support program, to serve as a single point of coordination throughout the treatment journey.
• The Company welcomed key members of its sales, market access, marketing and medical affairs team to support its planned formal launch of FORZINITY in the second quarter of 2026.

Research & Development Update:

In parallel with commercial execution, the Company continues to advance its development of elamipretide and other mitochondria-targeted pipeline compounds for diseases of mitochondrial dysfunction.

• BTHS. The Company will meet with the FDA in early 2026 to discuss a regulatory path forward for individuals living with BTHS who do not currently meet the FDA-approved weight threshold for FORZINITY. The Company is continuing to provide uninterrupted elamipretide access for those younger patients already enrolled in its EAP or for whom doctors submit new requests for emergency access. The Company is on track to initiate its FDA-required post-marketing trial to confirm clinical benefit during the first half of 2026.
• nPMD. The Company plans to meet with the FDA in early 2026 to discuss next steps in its development efforts for patients living with PMD due to polymerase gamma and other nDNA mutations (nPMD), which the Company plans to pursue as a potential next rare disease indication for elamipretide.
• Dry AMD. The Company's fully-enrolled Phase 3 ReNEW clinical trial of elamipretide for dry AMD is expected to read out in late 2027. An eye drop formulation of the Company's next-in-class clinical stage compound, bevemipretide, is in Phase 1 development for dry AMD, with Phase 2 initiation targeted by year-end 2026.
• Pipeline. Systemic bevemipretide, has recently demonstrated neuroprotective effects in Parkinson's disease preclinical studies supported by the Michael J Fox Foundation. The Company is evaluating next steps for development of systemic bevemipretide and other pipeline compounds for diseases of mitochondrial dysfunction.

About FORZINITY™ (elamipretide) injection

INDICATION

FORZINITY™ is a mitochondrial cardiolipin binder indicated to improve muscle strength in adult and pediatric patients with Barth syndrome weighing at least 30 kg.

This indication is approved under accelerated approval based on an improvement in knee extensor muscle strength, an intermediate clinical endpoint. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial(s).

CONTRAINDICATIONS
Serious hypersensitivity to elamipretide or any of the ingredients.

WARNINGS AND PRECAUTIONS
FORZINITY is not approved in neonates.  FORZINITY contains benzyl alcohol and serious adverse reactions including fatal reactions have been reported in low birth weight neonates and preterm neonates who received benzyl alcohol-containing drugs intravenously.  FORZINITY is not approved for intravenous use.

Hypersensitivity reactions, including serious allergic reactions requiring emergency medical intervention, have been reported in patients receiving FORZINITY.  Monitor patients for signs and symptoms of hypersensitivity reactions during treatment.

ADVERSE REACTIONS
Most common adverse reactions are injection site reactions.

To report SUSPECTED ADVERSE REACTIONS, contact Stealth BioTherapeutics Inc. at 1-844-444-6486 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

For more information about FORZINITY, please see the full US Prescribing Information, including important safety information.

About Barth Syndrome
BTHS is 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 is associated with reduced life expectancy, with 85% of early deaths occurring by age 5. BTHS occurs primarily in males and is estimated to affect one in 1,000,000 male births. There are no EMA-approved therapies for patients with BTHS.

About Stealth BioTherapeutics
Stealth BioTherapeutics' mission is to develop novel therapies to improve the lives of patients living with diseases of mitochondrial dysfunction. Stealth's commercial product, FORZINITY™ (elamipretide) injection, was granted accelerated approval by the U.S. Food & Drug Administration (FDA) in September 2025 as the first FDA-approved treatment for BTHS, as well as the first FDA-approved mitochondria-targeted therapeutic. Continued approval for this indication may be contingent upon verification of clinical benefit in confirmatory trial(s). Stealth is studying elamipretide in additional indications, including dry AMD and nPMD and is developing its next-in-class clinical-stage candidate, bevemipretide, for ophthalmic and neurological disease indications.

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SOURCE Stealth BioTherapeutics Inc.