FDA Grants Orphan Drug Designation to Stealth BioTherapeutics’ Experimental Mitochondrial Myopathy Drug Elamipretide


The investigational drug elamipretide, under development by Stealth BioTherapeutics to treat muscle weakness caused by mitochondrial disease, has received U.S. Food and Drug Administration (FDA) Orphan Drug Designation.

Elamipretide is designed to modify disease by helping restore normal energy production in mitochondria and decrease oxidative stress. Mitochondria are small, essential organelles that populate every cell of the body and are often referred as the “powerhouse of the cell,” since they generate most of the energy in an organism.

What this means for individuals and families

Orphan Drug Designation may help facilitate development of elamipretide for the treatment of mitochondrial myopathy, as it provides incentives meant to encourage Stealth BioTherapeutics to develop and market it.

Last year, the company reported results from its completed phase 2 MMPOWER trial, showing that treatment with elamipretide was safe and well-tolerated. In June 2017, the results from MMPOWER-2, a phase 2 continuation study, showed treatment with elamipretide was associated with significant benefits across multiple measurements, including the primary endpoint, the six-minute walk test, which measures the distance a person can walk on a flat, hard surface in a period of six minutes.

Stealth BioTherapeutics currently is recruiting participants for the RePOWER trial, an observational study of people with primary mitochondrial disease (PMM). RePOWER is designed to better characterize and correlate symptoms and signs of myopathy, genetic test results and the use of commonly prescribed treatments. Participants in the RePOWER study may have the opportunity to participate in a future phase 3 trial for elamipretide.

To be eligible to participate in RePOWER, you must be 16 – 65 years old and meet additional eligibility criteria. For more information, visit ClinicalTrials.gov and enter NCT03048617 into the search box.

What this means for Stealth BioTherapeutics

Orphan Drug Designation is important to companies, like Stealth BioTherapeutics, that are developing therapies because it makes them eligible for special incentives that have been put into place to encourage the development of treatments for rare disorders. In the U.S., a disorder is considered “rare” if it affects fewer than 200,000 individuals — and all the diseases under MDA’s umbrella are considered rare under this definition.

When a potential therapy receives this designation, the sponsor (i.e. the company who is seeking approval from the FDA) can benefit from incentives including reduced taxes, reduced or waived fees for filing with the FDA, and additional years of market exclusivity (when they are protected by law from competition), among others.

The purpose of the Orphan Drug Designation incentives is to encourage companies to work in the rare disease space where the high costs associated with developing a therapy are less likely to be recouped if the treatment is approved and marketed due to the small patient population that may be eligible to benefit from the therapy.

Because mitochondrial disease impacts fewer than 200,000 individuals in the U.S. and because the other Orphan Drug Designation requirements were satisfied by Stealth BioTherapeutics, elamipretide will have the protections and benefits of Orphan Drug status.