Stealth BioTherapeutics (Stealth), a biopharmaceutical company developing drug candidates for treating mitochondrial dysfunction, announced that the U.S. Food and Drug Administration (FDA) has granted Fast Track designation for MTP-131 (also known as Bendavia) for the treatment of primary mitochondrial myopathy, characterized by muscle weakness in patients with genetic mitochondrial diseases. MTP-131 is currently being studied for the treatment of primary mitochondrial myopathy in its MMPOWER trial, with results expected midyear.