Fulcrum Therapeutics Acquires Experimental Facioscapulohumeral Muscular Dystrophy Drug

According to a press release from Massachusetts-based biotech company Fulcrum Therapeutics, the company has successfully secured global commercialization rights of GlaxoSmithKline-developed experimental facioscapulohumeral muscular dystrophy (FSHD) drug losmapimod.

Losmapimod, an investigational MAPK inhibitor, has undergone early phase clinical trials. Fulcrum’s acquisition of the drug rights comes in anticipation of the initiation of a phase 2b trial designed to test the effectiveness of the drug in treating FSHD, for which their are currently no existing treatments.

About Facioscapulohumeral Muscular Dystrophy

Facioscapulohumeral muscular dystrophy is a genetically-linked neuromuscular disease characterized by the progressive weakening and subsequent atrophy of certain muscles. “Facioscapulohumeral” refers to the muscles most commonly affected by FSHD: those in the face, shoulders, and upper arms. Though there are technically two types of FSHD (types 1 and 2, appropriately), they have roughly the same symptoms and differ only in their root genetic origin. Additionally, the vast majority (about 95%) of all reported cases of FSHD are type 1.

In these cases, a mutation in a region of the fourth chromosome called D4Z4 allows a gene called DUX4 to remain active throughout adulthood. Scientists aren’t yet positive what DUX4 does when active, but theorize it may regulate the activity of other genes – potentially acting as a sort of master circuit breaker for other mutations.

Symptoms of FSHD typically don’t present until adolescence, though individual cases do vary and can occur as early as infancy or as late as adulthood. Severity of the condition can vary in turn. Over time, muscle weakness may intensify and spread to other regions of the body. Long-term effects even include moderate hearing loss or lordosis (pronounced rounding of the lower spine).

Concerning Losmapimod and its Recent Acquisition

Losmapimod has existed, in a laboratory sense, for several years already. It’s classified as a MAPK inhibitor, a class of drugs that works to inhibit certain elements of signal transduction pathways. That’s a fancy way of saying losmapimod and other MAPK inhibitors can shut off certain gene signals that are being erroneously expressed in some individual.

Fulcrum Therapeutics, realizing the potential of MAPK inhibitors to treat a variety of chronic conditions, quickly identified losmapimod as a potential inhibitor of DUX4 expression. In a bold prediction, Fulcrum wrote in its press release that the Company believes losmapimod “has the potential to slow or halt the progressive muscle weakness that characterizes [FSHD].”

In exchange for global rights over losmapimod, including existing research materials and rights-of-reference, Fulcrum surrendered an undisclosed but “high single-digit” ownership percentage of the Company to GlaxoSmithKline.

Fulcrum hopes to proceed with phase 2b testing of its new product around midyear.


When might pathway inhibitors be preferable to more “invasive” forms of gene silencing, like gene therapy? Share your thoughts with Patient Worthy!

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