Stealth BioTherapeutics Initiates Phase 3 Study of Elamipretide in Patients with Primary Mitochondrial Myopathy

BOSTON, Nov. 6, 2017 /PRNewswire/ — Stealth BioTherapeutics (Stealth), a clinical-stage biopharmaceutical company developing therapeutics to treat mitochondrial dysfunction, today announced the initiation of MMPOWER-3, a Phase 3 study evaluating the efficacy and safety of daily subcutaneous injections of elamipretide in patients with primary mitochondrial myopathy (PMM). MMPOWER-3 will enroll eligible patients who previously participated in RePOWER, an ongoing, prospective, non-interventional study evaluating patients with PMM.

“There are no FDA-approved treatments for people with primary mitochondrial myopathy, leaving clinicians with limited options, such as vitamin regimens and palliative care, to treat the debilitating muscle weakness and fatigue that affect a patient’s ability to perform everyday tasks,” said Dr. Bruce H. Cohen, Director of the NeuroDevelopmental Science Center at Akron Children’s Hospital. “The encouraging results from two prior Phase 2 clinical trials with elamipretide in this population make us optimistic about this investigational compound’s potential to treat patients with PMM.”

MMPOWER-3 is a randomized, double-blind, parallel-group, placebo-controlled trial to evaluate the effect of elamipretide in approximately 200 patients with PMM between the ages of 16 and 80. It will be followed by an open-label extension period. The trial will be conducted at 30 clinical sites across North America, Europe and Australia. The primary endpoints will be change in the distance walked during the six-minute walk test and change in the Total Fatigue score on the Primary Mitochondrial Myopathy Symptom Assessment (PMMSA), a patient-reported outcome measure. Secondary endpoints include safety, tolerability, and additional patient- and clinician-reported outcomes.

In June 2016, Stealth announced results from MMPOWER, its initial Phase 2 clinical trial studying elamipretide in PMM. In June 2017, Stealth announced results from MMPOWER-2, a Phase 2 continuation trial evaluating elamipretide’s safety, tolerability and efficacy for patients with PMM, which showed evidence of effectiveness across multiple endpoints. Findings from MMPOWERMMPOWER-2 and RePOWER helped inform the Phase 3 trial design and patient population.

“As leaders in the field of mitochondrial medicine, we are committed to developing new treatment options for patients with unmet medical needs,” said Stealth Chief Executive Officer Reenie McCarthy. “We are thrilled to advance this program for elamipretide in PMM, for which we have recently received Orphan Drug Designation, into our first Phase 3 clinical trial intended to support a future regulatory filing in this indication.”

For additional information on MMPOWER-3 or elamipretide, please refer to Stealth’s website or


MMPOWER-3 is a Phase 3, randomized, double-blind, parallel-group, placebo-controlled trial to evaluate the efficacy and safety of daily subcutaneous injections of elamipretide followed by an open-label treatment extension in subjects with PMM. Subjects will have been previously enrolled in RePOWER, which is still recruiting. The trial will assess approximately 200 patients between the ages of 16 and 80 with confirmed PMM.

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 – PMM, Barth syndrome and Leber’s hereditary optic neuropathy – as well as in heart failure, Fuchs’ corneal dystrophy and dry age-related macular degeneration. 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 neurodegeneration. To learn more information about us and our pipeline, visit


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