Stealth BioTherapeutics Initiates Phase 2/3 Study of Elamipretide in Patients with Barth Syndrome

Study will evaluate elamipretide in rare genetic mitochondrial disease characterized by muscle weakness, cardiac abnormalities, recurrent infections and delayed growth

BOSTON – July 19, 2017 – Stealth BioTherapeutics (Stealth), a clinical-stage biopharmaceutical company developing therapeutics to treat mitochondrial dysfunction, today announced the initiation of TAZPOWER, a Phase 2/3 study evaluating elamipretide in patients with Barth syndrome. Barth syndrome is a rare genetic mitochondrial disease, caused by mutations in the TAZ gene, and characterized by cardiac abnormalities, skeletal muscle weakness, recurrent infections and delayed growth.

“The severe problems experienced by patients with Barth syndrome are caused by misshapen and dysfunctional mitochondria, which reduce the energy production in the affected tissues. The resulting muscle weakness can lead to severe fatigue, heart failure and death,” said Stealth Chief Medical Officer Doug Weaver. “In this study, we hope to show that elamipretide may have clinical benefit by improving function in these affected mitochondria.”

TAZPOWER is a randomized, double-blind, placebo-controlled crossover study that will evaluate the effects of daily elamipretide treatment in a minimum of 12 patients with genetically confirmed Barth syndrome. Patients will be randomized to one of two sequence groups: 12 weeks of single daily subcutaneous injections of elamipretide in Treatment Period 1, followed by 12 weeks of treatment with placebo in Treatment Period 2, with a four-week wash-out period between periods, or vice versa. The primary endpoint is change in distance walked during the six-minute walk test. Secondary endpoints include functional assessments, patient-reported outcomes and safety.

“Our understanding of Barth syndrome and how it manifests has evolved significantly, but current treatment efforts are still limited to the management of symptoms,” said Hilary Vernon, M.D., Ph.D., assistant professor of Pediatrics at McKusick-Nathans Institute of Genetic Medicine at Johns Hopkins University and the primary investigator for the study. “The initiation of TAZPOWER represents an important milestone in the potential development of a disease-specific treatment option.”

TAZPOWER builds upon Stealth BioTherapeutics’s existing rare disease and cardiorenal programs, including three ongoing Phase 2 studies in adults with heart failure (IDDEA-HF, PROGRESS-HF, RESTORE-HF).

“This study underscores our commitment to develop elamipretide for the treatment of rare genetic mitochondrial diseases,” said Stealth Chief Executive Officer Reenie McCarthy. “The cardiovascular and skeletal muscle symptoms affecting this population share a common thread with symptoms experienced in diseases commonly associated with aging, such as heart failure, in which mitochondrial dysfunction contributes to the clinical pathology.”

For additional information on the TAZPOWER study or elamipretide, please refer to Stealth’s website.

About Barth Syndrome

Barth syndrome is a rare genetic condition characterized by muscle weakness, cardiac abnormalities, recurrent infections and delayed growth. Barth syndrome occurs almost exclusively in males and is estimated to affect one in 200,000 to 400,000 individuals worldwide at birth. There are currently no FDA-approved therapies for the disease.

About Stealth BioTherapeutics

We are a privately held clinical-stage biotechnology company focused on the development of therapeutics for diseases involving mitochondrial dysfunction. We believe there is a strong rationale for our lead product candidate, elamipretide, in indications in these diseases based on encouraging preclinical and early clinical data. We are investigating elamipretide in three primary mitochondrial diseases – primary mitochondrial myopathy (PMM), Barth syndrome and Leber’s hereditary optic neuropathy (LHON) – as well as in heart failure, Fuchs’ corneal dystrophy and dry age-related macular degeneration. We received Fast Track designation for elamipretide for the treatment of PMM from the FDA in December 2015. We are developing our second product candidate, SBT-20, for central nervous system disorders. Our mission is to be the leader in mitochondrial medicine. To learn more information about us and our pipeline, visit


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