• Stealth BioTherapeutics Corp (NASDAQ: MITO) has received a Refusal to File letter from the FDA regarding its marketing application for elamipretide, a mitochondria-targeted therapy for Barth syndrome.

• Barth syndrome is an ultra-rare genetic condition characterized by cardiac abnormalities often leading to heart failure and reduced life expectancy, recurrent infections, muscle weakness, and delayed growth.

• Related: Stealth Bio Posts Encouraging Preclinical Data In Parkinson's Animal Studies.

• Upon its preliminary review, the FDA determined that the application was not sufficiently complete to permit a substantive review.

• The agency noted that the SPIBA-201 Phase 2 trial was negative during the randomized, double-blind portion of the study. The FDA does not consider the open-label extension of the trial to be adequate and well-controlled.

• The letter did not explain why SPIBA-001 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.

• Related content: Benzinga's Full FDA Calendar.

• Price Action: MITO shares are down 17.4% at $1.14 during the premarket session on the last check Wednesday.

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