Stealth BioTherapeutics Granted Orphan Drug Designation of Elamipretide for Treatment of Patients with Primary Mitochondrial Myopathy

BOSTON – October 2, 2017 – Stealth BioTherapeutics (Stealth), a clinical-stage biopharmaceutical company developing therapeutics to treat mitochondrial dysfunction, today announced that the U.S. Food and Drug Administration’s (FDA) Office of Orphan Products Development (OOPD) has granted Orphan Drug Designation to Stealth’s investigational drug candidate, elamipretide, for the treatment of patients with primary mitochondrial myopathy (PMM).

“We are thrilled to achieve this key regulatory milestone for the treatment of PMM, a debilitating condition characterized by muscle weakness and fatigue with no FDA-approved treatments,” said Reenie McCarthy, Stealth’s chief executive officer. “We will continue to work closely with the FDA as we advance into our Phase 3 trial of elamipretide in patients with PMM.”

The Orphan Drug Act was enacted in 1983 to encourage development of drugs for rare diseases, which are diseases that affect 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 June 2017, Stealth announced results from MMPOWER-2, a Phase 2 continuation trial evaluating safety, tolerability and efficacy of treatment with elamipretide for PMM, which showed benefit of elamipretide across multiple endpoints assessed and supports a Phase 3 trial in this patient population. Stealth is currently recruiting for the RePOWER trial, an observational study of patients with PMM. Patients enrolled in RePOWER may have the opportunity to participate in the Phase 3 trial to further evaluate the potential efficacy, safety and tolerability of elamipretide for patients with PMM.

For additional information on elamipretide, please refer to Stealth’s website.

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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