The Food and Drug Administration (FDA) has granted Fast Track designation to losmapimod for the treatment of facioscapulohumeral muscular dystrophy (FSHD).

FSHD is a rare, progressive disease characterized by skeletal muscle loss. The disease is caused by the abnormal expression of the DUX4 gene in skeletal muscle, resulting in the presence of DUX4 proteins that are toxic to muscle tissue. Losmapimod is a selective p38α/β mitogen activated protein kinase (MAPK) inhibitor that works by reducing the expression of the DUX4 gene in muscle cells. 

The Company is evaluating the efficacy and safety of losmapimod in patients with FSHD in the randomized, double-blind, placebo-controlled phase 2b ReDUX4 trial (ClinicalTrials.gov: NCT04003974). Findings from a pre-specified sensitivity analysis showed that treatment with losmapimod led to a 38-fold reduction in DUX4-driven gene expression in patients with the highest pre-treatment DUX4-driven gene expression in their muscle biopsy sample, compared with a 5.4-fold reduction for placebo. Full trial data is expected to be presented at the virtual FSHD International Research Congress on June 24-25, 2021. 

“There are no approved therapies to treat patients with FSHD, and losmapimod is currently the only drug in clinical development for this serious and debilitating disease,” said Judith Dunn, PhD, Fulcrum’s president of research and development. “We are pleased that the FDA has granted Fast Track designation, which we believe demonstrates the potential for losmapimod to address unmet medical needs for people living with FSHD.”


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The FDA’s Fast Track designation allows for expedited review of therapies that are meant to treat serious or life-threatening conditions. Generally, the designation is granted to drugs that are expected to have an impact on factors such as survival and daily functioning.

References

  1. Fulcrum Therapeutics announces U.S. Food and Drug Administration grants Fast Track designation to losmapimod for the potential treatment of facioscapulohumeral muscular dystrophy (FSHD). [press release]. Cambridge, MA: Fulcrum Therapeutics, Inc; May 12, 2021. 
  2. Fulcrum Therapeutics announces interim analysis data from its ReDUX4 trial in facioscapulohumeral muscular dystrophy (FSHD). [press release]. Cambridge, MA: Fulcrum Therapeutics, Inc; August 11, 2020.