Stealth BioTherapeutics Granted Orphan Drug Designation for Elamipretide for Treatment of Barth Syndrome

BOSTON – April 9, 2018 – Stealth BioTherapeutics (Stealth), a clinical-stage biopharmaceutical company developing therapeutics to treat mitochondrial dysfunction, today announced that the U.S. Food and Drug Administration (FDA) Office of Orphan Products Development has granted Orphan Drug Designation to Stealth’s investigational drug candidate, elamipretide, for the treatment of patients with Barth syndrome.

“There are currently no FDA-approved therapies for patients with Barth syndrome, a debilitating condition characterized by heart and skeletal muscle weakness,” said Reenie McCarthy, Stealth’s chief executive officer. “We believe elamipretide represents a promising, novel approach with the potential to offer hope for patients with Barth syndrome, and we are very pleased to have received Orphan Drug Designation for this indication.”

The Orphan Drug Act, enacted in 1983, encourages development of therapies for rare diseases. A disease is considered rare if it affects fewer than 200,000 persons in the United States. Once granted, Orphan Drug Designation provides various development benefits for an investigational drug, including seven-year exclusivity after marketing approval is received.

In March 2018, Stealth announced the completion of enrollment in the TAZPOWER clinical trial, a phase 2/3 crossover study evaluating the effects of daily treatment with elamipretide in 12 patients with genetically confirmed Barth syndrome followed by an open-label treatment extension. The primary endpoints include change in distance walked during the six-minute walk test and change in total fatigue as measured by a patient-reported outcome measure, the Barth Syndrome Symptom Assessment. Secondary endpoints include additional functional assessments, patient-reported outcomes and safety. Data from the TAZPOWER trial are expected later this year.

In November 2017, Stealth announced that the FDA granted Fast Track designation for elamipretide for the treatment of Barth syndrome. 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 often leading to heart failure, recurrent infections, delayed growth, and reduced life expectancy. 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

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 dry age-related macular degeneration (AMD). We received Orphan Drug Designation of elamipretide for the treatment of PMM from the FDA in September 2017. We are developing our second product candidate, SBT-20, for neurodegenerative diseases. To learn more information about us and our pipeline, visit


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