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13 January 2020

The Elamipretide trials (MMPOWER-3) organised by Stealth BioTherapeutics for the treatment of Primary Mitochondrial Myopathy unfortunately did not turn out to meet the defined primary endpoints. The six-minute walk test and the Primary Mitochondrial Myopathy Symptom Asessment (PMMSA) Total Fatigue Score did not show sufficient improvement. In other words the first analyses did not generate the desired treatment effect. Safety results showed that treatment with elamipretide was well tolerated with most adverse events mild to moderate in severity.

This unanticipated and extremely disappointing result led to the decision to discontinue all PMM trials completely.

"We are deeply grateful to our patients and families, our investigators and their teams, and our advocacy partners for their support of this study, and share their disappointment that it did not meet the promise of our earlier trials in this indication," said Chief Executive Officer Reenie McCarthy. "We remain confident in the promise of our platform and committed to our mission of improving the lives of people living with diseases involving mitochondrial dysfunction. We plan to meet with the FDA in early 2020 regarding our Barth syndrome program, where we have observed significant improvement in cardiac stroke volume during open-label extension, and continue to enroll our Phase 2b clinical trial in geographic atrophy associated with dry age-related macular degeneration, in which we observed improvement in visual function during an earlier Phase 1 study. We are also progressing our pipeline of second-generation mitochondrial therapeutics, with lead pipeline compound SBT-272 entering Phase 1."

The Company plans to review its operational resources to align them with its near-term priorities of progressing its Barth, AMD and pipeline programs, and expects to provide further guidance next month.

About the MMPOWER-3 Clinical Trial:

MMPOWER-3 was a Phase 3 randomized, double-blind, parallel-group, placebo-controlled trial to evaluate the efficacy and safety of elamipretide over 32 weeks in 218 patients with primary mitochondrial myopathy between the ages of 16 and 80. The trial was conducted at 28 clinical sites across Europe and Australia.

For more information about Stealth: https://www.stealthbt.com/

© 2020 Int. Mito Patients