FDA Grants Orphan Drug Designation for Losmapimod for Facioscapulohumeral Muscular Dystrophy

The Food and Drug Administration (FDA) has granted orphan drug designation to losmapimod (Fulcrum Therapeutics, Cambridge, MA), a selective p38α/β mitogen-activated protein kinase (MAPK) inhibitor for the treatment of facioscapulohumeral muscular dystrophy (FSHD). The FDA grants orphan status for development of medicines intended for safe and effective treatment, diagnosis, or prevention of rare diseases that affect fewer than 200,000 people in the US. 

Preliminary results from clinical trials (NL8000) of losmapimod in participants with FSHD showed that the drug achieved dose-dependent concentrations in plasma and muscle believed to be adequate for efficacy based on preclinical pharmacology studies. 

Researchers discovered that inhibition of p38α/β reduced expression of the DUX4 gene in muscle cells derived from individuals with FSHD. 

“We are pleased to have been granted orphan drug designation for losmapimod in FSHD as it underscores the critical need for treating this rare muscular dystrophy that has no approved therapies,” said Robert J. Gould, PhD, president and chief executive officer, Fulcrum Therapeutics. “We believe losmapimod represents a promising, novel approach to treat the known root cause of FSHD and remain on-track to announce data from the phase 2b ReDUX4 clinical trial in the third quarter of 2020.”