Stealth BioTherapeutics Corp (Nasdaq: MITO), a clinical-stage biotechnology company focused on the discovery, development, and commercialization of novel therapies for diseases involving mitochondrial dysfunction, today announced that it received a Refusal to File letter from the United States Food and Drug Administration (FDA) regarding Stealth’s New Drug Application (NDA) for elamipretide, a mitochondria-targeted therapy for the treatment of Barth syndrome.
The FDA determined, upon its preliminary review, that the NDA was not sufficiently complete to permit a substantive review. In the letter, the FDA stated that the NDA does not contain an adequate and well-controlled trial that provides evidence of effectiveness, noting that the SPIBA-201 Phase 2 clinical trial of elamipretide for the treatment of Barth syndrome was negative during the randomized, double-blind portion of the study and that the FDA does not consider the open label extension of the SPIBA-201 trial to be adequate and well-controlled. The FDA reiterated its commitment to work with Stealth on a pathway by which a beneficial effect of elamipretide might be demonstrated within the small patient population.
The letter did not explain why SPIBA-001, the Company’s positive Phase 3 trial comparing SPIBA-201 results to a retrospective natural history control and the primary basis for the NDA submission, would not be considered an adequate and well-controlled trial. Stealth is evaluating the appropriate next steps and anticipates providing an update in early November.
Stealth and the FDA have previously discussed the challenges of conducting additional clinical trials in Barth syndrome, which is an ultra-rare genetic disease affecting fewer than 130 individuals in the United States. “We submitted our NDA at the request of the Barth syndrome patient community, which petitioned us and the FDA to gain access to elamipretide and shared with the FDA its tolerance of risk of uncertainty of benefit based on the data from the small clinical trials we were able to conduct in this ultra-rare disease,” said Chief Executive Officer Reenie McCarthy. “We deeply value our relationship with the Barth syndrome patient community, and hope to find a way to progress elamipretide as a treatment for Barth syndrome.”
Elamipretide was previously granted rare pediatric designation, fast track designation, and orphan drug designation by the FDA, and orphan drug designation by the European Medicines Agency (EMA), for the treatment of Barth syndrome.