Stealth BioTherapeutics Completes Enrollment of Pivotal Study in Primary Mitochondrial Myopathy

Date : April 25, 2019

BOSTON, April 25, 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 completion of enrollment for MMPOWER-3 (SPIMM-301), with top-line data expected by year end. MMPOWER-3 is a Phase 3, randomized, double-blind, parallel-group, placebo-controlled study to evaluate the efficacy and safety of daily subcutaneous injections of elamipretide in patients with primary mitochondrial myopathy (PMM) followed by an open-label treatment extension. 

Stealth BioTherapeutics Logo (PRNewsFoto/Stealth BioTherapeutics)

"The debilitating fatigue and muscle weakness due to primary mitochondrial myopathy often has a negative impact on the quality of life of affected patients," said Dr. Michio Hirano, professor of neurology at Columbia University Medical Center in New York, who enrolled the most patients across the 28 sites involved in the trial. "I am encouraged by the data demonstrated with elamipretide in prior trials and was pleased to be able to offer our patients the opportunity to participate in this trial."

Approximately 40,000 individuals in the U.S. have been diagnosed with PMM, a rare primary mitochondrial disease. There are currently no therapies approved by the U.S. Food and Drug Administration (FDA) for the treatment of PMM.

"We are grateful to the scientific, advocacy and patient communities, as well as the FDA, for partnering with us in our efforts to reach this important milestone, which we hope will pave the way toward providing potentially transformative therapy for affected individuals," said Stealth Chief Executive Officer Reenie McCarthy. "We are particularly encouraged by the strong patient interest, which enabled us to exceed our enrollment goal."

The MMPOWER-3 study exceeded its expected enrollment with 218 patients out of a targeted 202 patients. The primary endpoints of the six-month, parallel-design study are change in distance walked (meters) as measured by 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 and tolerability, as well as patient- and clinician-reported outcomes. Patients completing the double-blind portion of the study (Part 1) are eligible to continue into an open-label extension (Part 2); 80 of the 85 patients who have completed Part 1 so far are participating in Part 2.

In December 2015, the FDA granted Fast Track designation for elamipretide for the treatment of PMM. In October 2017, the FDA Office of Orphan Products Development granted Orphan Drug Designation for elamipretide for this indication.

For additional information on the MMPOWER-3 study or elamipretide, please refer to Stealth's website and

About Primary Mitochondrial Myopathy

Primary (inherited) mitochondrial myopathy, or PMM, is characterized by debilitating fatigue, skeletal muscle weakness and exercise intolerance. It is estimated that approximately 40,000 individuals in the U.S. have been diagnosed with PMM. There are no therapies approved by the U.S. Food and Drug Administration (FDA) or the European Medicines Agency (EMA) for the treatment of PMM.

About Stealth

We are a clinical-stage biotechnology company focused on the discovery, development and commercialization of novel therapies for diseases involving mitochondrial dysfunction. 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 dry age-related macular degeneration. Our other pipeline candidates include SBT-272, which we are evaluating for rare neurodegenerative disease indications, and SBT-20, which we are evaluating 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.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. Such forward-looking statements include those regarding Stealth BioTherapeutics' plans, strategies and expectations for its preclinical and clinical advancement of its drug development programs, including its ongoing clinical trials of elamipretide for the treatment of primary mitochondrial myopathy. Statements that are not historical facts, including statements about Stealth BioTherapeutics' beliefs, plans and expectations, are forward-looking statements. The words "anticipate," "expect," "hope," "plan," "potential," "possible," "will," "believe," "estimate," "intend," "may," "predict," "project," "would" and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Stealth BioTherapeutics may not actually achieve the plans, intentions or expectations disclosed in these forward-looking statements, and you should not place undue reliance on these forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements as a result of known and unknown risks, uncertainties and other important factors, including: Stealth BioTherapeutics' ability to obtain additional funding; the ability to successfully demonstrate the efficacy and safety of Stealth BioTherapeutics' product candidates and future product candidates; the preclinical and clinical results for Stealth BioTherapeutics' product candidates, which may not support further development and marketing approval; the potential advantages of Stealth BioTherapeutics' product candidates; the content and timing of decisions made by the U.S. FDA, the EMA or other regulatory authorities, investigational review boards at clinical trial sites and publication review bodies, which may affect the initiation, timing and progress of preclinical studies and clinical trials of Stealth BioTherapeutics product candidates; Stealth BioTherapeutics' ability to obtain and maintain requisite regulatory approvals and to enroll patients in its planned clinical trials; unplanned cash requirements and expenditures; competitive factors; Stealth BioTherapeutics' ability to obtain, maintain and enforce patent and other intellectual property protection for any product candidates it is developing; and general economic and market conditions. These and other risks are described in greater detail under the caption "Risk Factors" included in Stealth BioTherapeutics' most recent Annual Report on Form 20-F filed with the Securities and Exchange Commission ("SEC"), as well as in any future filings with the SEC. Forward-looking statements represent management's current expectations and are inherently uncertain. Except as required by law, Stealth BioTherapeutics does not undertake any obligation to update forward-looking statements made by us to reflect subsequent events or circumstances.


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