Mighty Therapeutics Announces First Patient Dosed in Phase 4 Confirmatory Study of Elamipretide in Barth Syndrome

– Comprehensive updates to be presented at Barth Syndrome Foundation conference –

NEEDHAM, Mass., July 8, 2026 /PRNewswire/ -- Mighty Therapeutics (the "Company" or "Mighty"), a commercial-stage biotechnology company pioneering a new class of medicines that directly target mitochondrial dysfunction in rare and age-related diseases, today announced that the first patient has been dosed in 4TAZPower, its global Phase 4 study to confirm the efficacy, safety, and pharmacokinetics of once-daily elamipretide in individuals at least 5 years of age living with Barth syndrome. FORZINITY™ (elamipretide) injection received accelerated approval from the United States (US) Food and Drug Administration (FDA) for individuals with Barth syndrome weighing at least 30kg, based on an improvement in knee extensor muscle strength, an intermediate clinical endpoint. The largest clinical development effort in Barth syndrome to date, the 4TAZPower study, has been designed to further confirm the clinical benefit and expand the understanding of the long-term safety of elamipretide for individuals living with Barth syndrome.

"We are committed to supporting and potentially expanding access to elamipretide for individuals living with Barth syndrome in the US and, we hope, globally," said Reenie McCarthy, Chief Executive Officer of Mighty Therapeutics. "Barth syndrome is a devastating progressive disease that knows no borders. Timely dosing of the first individual in our 4TAZPower study is a key step toward meeting our post-marketing commitments to the US FDA. As importantly, this milestone underscores our commitment to broaden participation opportunities to the global patient community. Patients remain at the forefront of our mission, so we are celebrating this step toward what we hope will be global access to the only therapy currently approved for this ultra-rare, life-threatening mitochondrial disease."

"Mighty's initiation of global development efforts for this devastating progressive disease is a milestone for the Barth syndrome patient and medical communities," said Hilary Vernon, M.D., Ph.D., Professor of Genetic Medicine at Johns Hopkins University School of Medicine and chair of the Trial Scientific Review Committee for the 4TAZPower study. "Throughout my career, I have met, treated, and consulted on the care of many patients living with Barth syndrome worldwide. For far too long, we had no therapeutic options to offer. It is gratifying to see Mighty take rapid steps to deliver upon its promise to broaden access to elamipretide for the global Barth syndrome community."  

"Patients and families around the world affected by Barth syndrome need more research and innovation for this devastating condition, and we are grateful for the new advances that the 4TAZPower study may deliver," said Michaela Damin, Chief Executive of Barth Syndrome UK. "The global Barth community is enthusiastic about participating in the study on behalf of patients today and for generations to come."

The 4TAZPower study is a randomized, double-blind, parallel-group, placebo-controlled clinical trial to evaluate the efficacy, safety, and pharmacokinetics of a once-daily subcutaneous injection of elamipretide in participants with genetically confirmed Barth syndrome for 72 weeks.

Barth Syndrome Clinical Program Presentations

The Company and its clinical collaborators will present updates on their Barth syndrome clinical development efforts at the Barth Syndrome Foundation's 2026 International Scientific, Medical, and Family Conference, which is being held on July 19-26, 2026, in Bonita Springs, Florida. At the conference, the Company will provide an overview of the 4TAZPower study and its progress on FDA-required post-marketing commitments.

In addition, the Company will provide an update on its efforts toward potential label expansion for individuals living with Barth syndrome who do not currently meet the approved weight threshold for FORZINITY. This includes a one-month safety and pharmacokinetic study to verify dosing for children weighing less than 30 kilograms, which the Company plans to initiate this year to support a potential 2027 supplemental new drug application (sNDA) submission for children as young as age 5. For infants and younger children, the Company is working to initiate a registry to standardize the collection of data from its expanded access program (EAP) to support potential  enhanced labeling for this population.

Mighty's presentations at the Barth Syndrome Foundation Conference are as follows:

• Oral Presentation and Q&A: "Mighty Therapeutics Scientific/Clinical Update"
  • Presenter: Anthony Abbruscato, Pharm.D., Sr. Vice President, Clinical Development, Mighty Therapeutics
  • Presentation Time: Wednesday, July 22 at 4:15-5:00 p.m. ET
  • Location: Calusa D-H
• Oral Presentation and Q&A: "Mighty Therapeutics Patient and Family Update"
  • Presenter: Reenie McCarthy, Chief Executive Officer, Mighty Therapeutics
  • Presentation Time: Friday, July 24 at 2:15-3:15 p.m. ET
  • Location: Calusa D-H
• Flash Talk: "Expanded Access Use of Elamipretide in an Infant with Barth Syndrome Caused by a Novel Variant of the TAFAZZIN Gene"
  • Presenter: Majid Husain, M.D., Pediatric Cardiologist, Mattel Children's Hospital at University of California Los Angeles
  • Presentation Time: Friday, July 24 at 4:00-5:45 p.m. ET
  • Session: "Research Spotlights 3B: Emerging Therapies & Research Strategies"
  • Location: Calusa A-C
• Flash Talk: "Claims Database Analysis to Assess the Complexity and Severity of Patient Cases, Disease Burden, and Health Care Resource Utilization (HCRU) in U.S. Barth Syndrome Patients"
  • Presenter: Mary Kay Koenig, M.D., Pediatric Neurologist, University of Texas McGovern Medical School
  • Presentation Time: Friday, July 24 at 4:00-5:45 p.m. ET
  • Session: "Research Spotlights 3B: Emerging Therapies & Research Strategies" 
  • Location: Calusa A-C

Held every two years, the Barth Syndrome Foundation's International Scientific, Medical, and Family Conference is the largest gathering of the global Barth syndrome community, bringing together affected individuals, caregivers, researchers, clinicians, and healthcare leaders.

About Mighty Therapeutics
Mighty Therapeutics, together with its wholly owned operating subsidiary, Stealth BioTherapeutics, Inc., is advancing novel therapies for people living with diseases involving mitochondrial dysfunction. Grounded in rigorous science and inspired by 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.

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Investor Contact
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SOURCE Mighty Therapeutics