– Identity recognizes the resilience of mitochondrial disease patient communities and celebrates the momentum following the approval of the first FDA-approved therapy to directly target mitochondria – 

NEEDHAM, Mass., June 16, 2026 /PRNewswire/ — Stealth BioTherapeutics Holdings Inc., a commercial-stage biotechnology company focused on the discovery, development, and commercialization of novel therapies for rare and age-related diseases driven by mitochondrial dysfunction, today announced it will now operate as Mighty Therapeutics (the “Company” or “Mighty”) following the company’s evolution into a commercial-stage biotechnology company and reflecting its continued leadership in pioneering mitochondrial medicine.

The rebrand follows the U.S. Food and Drug Administration (FDA)’s accelerated approval and the commercial launch of FORZINITY™ (elamipretide) injection for patients weighing at least 30 kg with Barth syndrome. This milestone introduced a new class of therapies offering hope for future therapeutic innovation for individuals living with mitochondrial disease.

“Mighty Therapeutics honors the patients and families who inspire our work every day,” said Reenie McCarthy, chief executive officer of Mighty Therapeutics. “Their partnership, trust, and advocacy continue to shape our science and strengthen our commitment to advancing therapies that target mitochondrial dysfunction.”

Mighty is advancing therapies designed to directly target the mitochondrial dysfunction underlying a range of rare and age-related diseases. Through its differentiated scientific focus on bioenergetics, development expertise, and maturing pipeline, the company is helping define the emerging field of mitochondrial medicine. 

“The mitochondrial disease community has long hoped for greater visibility, scientific investment, and therapeutic advancement,” said Kira Mann, chief executive officer of MitoAction. “Mighty Therapeutics openly centering patients and families in its identity is an encouraging moment for our community and for the future of this field.”

Walker Burger, an individual living with Barth syndrome, shared what the new name means to him personally.

“When I hear the word ‘Mighty,’ I think about continuing to push forward even when things are hard,” said Burger. “Living with Barth syndrome takes strength every day. To see a company choose a name that reflects how strong this community is makes me feel seen and hopeful for what comes next.”

The company recently reported strong early commercial momentum for FORZINITY, including broad reimbursement access, rapid patient onboarding timelines, and widespread adoption of its Mito Assist™ patient support program. Mighty continues to expand its medical and commercial infrastructure to support patients and families, and to educate healthcare providers and treatment centers across the United States. The company is also progressing clinical and regulatory initiatives to address post marketing commitments and support potential label expansion for younger children living with Barth syndrome.

Looking forward, Mighty remains focused on expanding the potential of mitochondrial medicine to other diseases of mitochondrial dysfunction. These include polymerase-gamma related mitochondrial disease, where ongoing regulatory engagement is planned to support pivotal trial initiation, and dry age-related macular degeneration (AMD), where the company’s fully enrolled ReNEW Phase 3 clinical trial is approaching completion in late 2027 and its Phase 2 clinical trial of bevemipretide topical ophthalmic drops is expected to start by year end. 

Beyond these programs, Mighty continues to innovate in mitochondrial medicine by investigating the role of mitochondria in aging and other diseases of mitochondrial dysfunction. The company will present data from a Phase 2a pilot study in older individuals at the American Aging Association in June. The company is also advancing preclinical initiatives to inform potential development for Parkinson’s disease, fatty acid oxidation disorders, Friedreich’s ataxia, Leigh syndrome and others.

The rebrand to Mighty Therapeutics will be implemented across the company’s corporate identity, website, and communications materials over the coming weeks. Learn more at www.mightytx.com

About Mighty Therapeutics

Mighty Therapeutics is advancing novel therapies for people living with diseases involving mitochondrial dysfunction. Grounded in rigorous science and meaningful patient partnerships, the company is building a proprietary pipeline to directly address bioenergetic deficits at the source.

In September 2025, Mighty marked a historic milestone with the U.S. Food and Drug Administration (FDA) approval of its first commercial therapy, establishing both the first FDA-approved treatment for Barth syndrome and the first FDA-approved therapy to directly target mitochondria.

Today, Mighty’s development portfolio encompasses rare and age-related diseases. Mighty continues to develop elamipretide in Barth syndrome, polymerase gamma related mitochondrial disease and dry age-related macular degeneration. Mighty is also progressing its next-generation clinical candidate, bevemipretide, for ophthalmic and neurological pathologies, and continues to develop preclinical assets SBT-255 and SBT-589 for rare mitochondrial disorders. For more information, visit www.mightytx.com. 

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).

IMPORTANT SAFETY INFORMATION
Contraindications

FORZINITY is contraindicated in patients with serious hypersensitivity to elamipretide or any of the excipients in FORZINITY.

Warnings and Precautions

Benzyl Alcohol Toxicity – Do Not Use in Neonates
Serious and fatal reactions (including metabolic acidosis progressing to neurotoxicity and gasping syndrome) have occurred in preterm and low–birth weight neonates receiving benzyl alcohol (BA)-containing drugs.

FORZINITY contains 20 mg BA/mL and is not approved for use in neonates or for IV administration.

Hypersensitivity

Reported reactions include rash, papular lesions, eczema/dermatitis, cough, and serious allergic reactions requiring emergency medical intervention.

Reactions may occur minutes to months after starting treatment. Monitor patients for signs and symptoms during treatment.

Discontinue FORZINITY permanently if a serious hypersensitivity reaction occurs.

Adverse Reactions

Adverse reactions occurring more commonly on FORZINITY than on placebo included injection site reactions such as injection site erythema, pain, induration, pruritus, bruising, and urticaria.

Eosinophilia

Modest elevations in eosinophil counts (peak ~90 days) occurred but were not associated with clinical symptoms.

To report SUSPECTED ADVERSE REACTIONS, contact FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Please see Full Prescribing Information for FORZINITY.

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.

Media Contact
Ascent Strategic Communications
media@ascentcomms.com

Investor Contact
Precision AQ
Austin Murtagh
Austin.Murtagh@precisionaq.com

Patient Advocacy
PatientAdvocacy@mightytx.com

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SOURCE Stealth BioTherapeutics Inc.