Stealth BioTherapeutics Presents Data for Elamipretide on Cardiac Function in Barth Syndrome

October 17, 2019
BOSTON, Oct. 17, 2019 /PRNewswire/ -- Stealth BioTherapeutics (NASDAQ: MITO), a clinical-stage biotechnology company focused on the discovery, development and commercialization of novel therapies for diseases involving mitochondrial dysfunction, today announced the presentation of new data from the open-label extension portion of the Phase 2/3 TAZPOWER study evaluating elamipretide in patients with Barth syndrome. The findings, presented at the American Society of Human Genetics (ASHG) 2019 Annual Meeting in Houston, Texas, showed that treatment with elamipretide resulted in a 27% increase in average cardiac stroke volume, or the amount of blood pumped by the heart's left ventricle per contraction, from the trial baseline (40.8 mL) to week 36 (51.8 mL) of the open-label extension. Left-ventricular stroke volume is one of the primary determinants of cardiac output, or the volume of blood pumped by the heart, which is an important indicator of how efficiently the heart can meet the body's demands for perfusion to various organs. In unaffected adolescent boys, an average stroke volume of 85 mL would be expected.

"Based on the data presented showing an increase in stroke volume, treatment with elamipretide appears to have improved heart function, which might indicate cardiac remodeling," noted Dr. W. Reid Thompson, Associate Professor of Pediatrics at the Johns Hopkins University School of Medicine. "Most patients with Barth syndrome have underlying heart disease, so a cardiac effect would be an important outcome in this setting that warrants further investigation."

Barth syndrome is an ultra-rare mitochondrial disease in which reduced levels of the mitochondrial phospholipid cardiolipin are associated with skeletal muscle weakness, debilitating fatigue, cardiac abnormalities, recurrent infections and delayed growth. Life expectancy is reduced in Barth, with early mortality, including in early childhood, due primarily to heart disease.

TAZPOWER was a Phase 2/3 crossover study of elamipretide in 12 patients with Barth syndrome followed by an open-label extension, in which 10 of the 12 patients participated. In the extension, previously presented as a late-breaker at the 2019 MDA Clinical & Scientific Conference, elamipretide demonstrated potential to improve measures of exercise performance, strength and patient- and clinician-reported outcomes.

"We are encouraged to learn that elamipretide may be associated with improvements in cardiac function in Barth patients, in addition to possible improvements in muscle function," said Chief Executive Officer Reenie McCarthy. "These changes in well-established biomarkers add to the body of evidence we expect to discuss with regulatory authorities over the next several months, as we progress toward our commitment to bring therapies to patients suffering from this life-limiting disease."

The U.S. Food and Drug Administration (FDA) has granted Fast Track and Orphan Drug designations for elamipretide for the treatment of Barth syndrome.

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

About the TAZPOWER Study

TAZPOWER is a Phase 2/3 crossover study evaluating the effects of daily subcutaneous (SC) treatment with elamipretide in 12 patients with genetically confirmed Barth syndrome followed by an open-label treatment extension. Part 1 was a 28-week crossover trial of patients randomized to elamipretide 40 mg SC daily for 12 weeks, followed by SC placebo daily for 12 weeks, or vice versa, separated by a 4-week washout. Part 2 is an open-label assessment for up to 168 weeks of functional assessments, patient-reported outcomes and safety/tolerability.

The primary endpoints included change in distance walked during the 6MWT and change in the BTHS-SA Total Fatigue score. Secondary endpoints included additional functional assessments, patient-reported outcomes and safety/tolerability.

About Barth Syndrome

Barth syndrome is an ultra-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 300,000 to 400,000 individuals worldwide at birth. There are currently no FDA-approved therapies for patients with Barth syndrome.

About Stealth

 We are a clinical-stage biotechnology company focused on improving the lives of patients suffering from diseases involving mitochondrial dysfunction through the discovery, development and commercialization of novel mitochondrial medicines. Mitochondria, found in nearly every cell in the body, are the body's main source of energy production and are critical for normal organ function. Dysfunctional mitochondria characterize a number of rare genetic diseases, collectively known as primary mitochondrial diseases, and are also involved in many common age-related diseases. We believe our lead product candidate, elamipretide, has the potential to treat both rare genetic and common age-related mitochondrial diseases. We are studying elamipretide in the following primary mitochondrial diseases: primary mitochondrial myopathy, Barth syndrome and Leber's hereditary optic neuropathy. We are also studying elamipretide in geographic atrophy associated with dry age-related macular degeneration. Our other pipeline candidates include SBT-272, which we are evaluating for rare neurodegenerative disease indications, and SBT-20 and SBT-259, being evaluated for rare peripheral neuropathies. We have optimized our discovery platform to identify novel mitochondrial-targeted compounds, which may be nominated as therapeutic product candidates or utilized as scaffolds to deliver other compounds to mitochondria. We have assembled a highly experienced management team, board of directors and group of scientific advisors to help us achieve our mission of leading mitochondrial medicine.


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