CAMBRIDGE, MA, USA I August 19, 2019 IFulcrum Therapeutics, Inc. (Nasdaq: FULC), a clinical-stage biopharmaceutical company focused on improving the lives of patients with genetically defined rare diseases, today announced it has initiated ReDUX4, a Phase 2b clinical trial of losmapimod in facioscapulohumeral muscular dystrophy (FSHD). The clinical trial is designed to evaluate the efficacy and safety of losmapimod, an investigational selective p38α/β MAPK inhibitor, in addressing the underlying cause of FSHD, a rare, progressive and disabling muscular dystrophy. 

“We are excited to evaluate losmapimod’s efficacy and safety in FSHD, a disease for which there are currently no approved treatments,” said Robert J. Gould, Ph.D., Fulcrum’s president and chief executive officer. “Initiating ReDUX4 is a significant milestone that brings us a step closer to our goal of improving the lives of patients and families who are impacted by FSHD. Losmapimod, a p38α/β mitogen activated protein kinase (MAPK) inhibitor identified through our proprietary product engine, reduced expression of the DUX4 gene in patient-derived muscle cells, which is the root cause of FSHD.”

The multicenter trial is a randomized, double-blind, placebo-controlled, 24-week study of losmapimod, and will enroll patients with genetically confirmed FSHD. The primary endpoint of the study is to evaluate the efficacy of losmapimod in inhibiting or reducing DUX4-driven gene expression. DUX4 expression will be measured by a subset of DUX4-regulated gene transcripts in skeletal muscle biopsies. Clinical data are expected in the third quarter of 2020. In parallel, Fulcrum will also initiate a 52-week open label study, which will include interim analyses.

About FSHD
FSHD is characterized by progressive skeletal muscle loss that initially causes weakness in muscles in the face, shoulders, arms and trunk, and progresses to weakness throughout the lower body. Skeletal muscle weakness results in significant physical limitations, including an inability to smile and difficulty using arms for activities, with many patients ultimately becoming dependent upon the use of a wheelchair for daily mobility.

FSHD is caused by mis-expression of DUX4 in skeletal muscle, resulting in the presence of DUX4 proteins that are toxic to muscle tissue. Normally, DUX4-driven gene expression is limited to early embryonic development, after which time the DUX4 gene is silenced. In people with FSHD, the DUX4 gene is turned “on” as a result of a genetic mutation. The result is death of muscle and its replacement by fat, leading to skeletal muscle weakness and progressive disability. There are no approved therapies for FSHD, one of the most common forms of muscular dystrophy, with an estimated patient population of 16,000 to 38,000 in the United States alone.

About Losmapimod
Losmapimod is a selective p38α/β mitogen activated protein kinase (MAPK) inhibitor that was exclusively in-licensed by Fulcrum Therapeutics following Fulcrum’s discovery of the role of p38α/β inhibitors in the reduction of DUX4 expression and an extensive review of known compounds. Utilizing its internal product engine, Fulcrum discovered that inhibition of p38α/β reduced expression of the DUX4 gene in muscle cells derived from patients with FSHD. Although losmapimod has never previously been explored in muscular dystrophies, it has been evaluated in more than 3,500 subjects in clinical trials across multiple other indications, including in several Phase 2 trials and a Phase 3 trial. No safety signals were attributed to losmapimod in any of these trials.

About Fulcrum Therapeutics
Fulcrum Therapeutics is a clinical-stage biopharmaceutical company focused on improving the lives of patients with genetically defined diseases in areas of high unmet medical need, with an initial focus on rare diseases. Fulcrum’s proprietary product engine identifies drug targets which can modulate gene expression to treat the known root cause of gene mis-expression. Please visit www.fulcrumtx.com.

SOURCE: Fulcrum Therapeutics