Mallinckrodt plc announced the U.S. Food and Drug Administration (FDA) has granted the company's request for a Fast Track designation for its Investigational New Drug (IND) application for Synacthen® Depot in the treatment of Duchenne muscular dystrophy (DMD). Synacthen Depot is a depot formulation of Synacthen (tetracosactide), a synthetic 24 amino acid melanocortin receptor agonist. Synacthen Depot is approved and marketed outside of the U.S. for certain autoimmune and inflammatory conditions, but has never been approved for use in patients in the U.S.

