Jennifer McNary, Executive Director, Head of Patient Advocacy and Engagement at Fulcrum Therapeutics, and mother to two Duchenne muscular dystrophy patients, discusses the significance of using reachable workspace (RWS) as the primary outcome measure for REACH, a  phase 3 study testing losmapimod in facioscapulohumeral muscular dystrophy (FSHD) patients.

FSHD is a rare, progressive musculoskeletal disease in which persons initially lose muscle strength in the face, shoulders, arms, and trunk, but later the disease progresses throughout the lower body. FSHD is due to the mis-expression of DUX4 in skeletal muscles. There are currently no approved treatments for the disease.

REACH will be a randomized, double-blind, placebo-controlled, multinational trial to evaluate the efficacy and safety of losmapimod, an investigational, selective p38α/β mitogen activated protein kinase (MAPK) inhibitor, for the treatment of FSHD. The trial is expected to enroll approximately 230 adults with FSHD. Patients will be randomized 1:1 to receive either losmapimod or placebo, and evaluated over a 48-week treatment period. 

As Ms. McNary mentions the primary outcome for the REACH study is the absolute change from baseline in reachable workspace, which is a quantitative and relevant measurement of function that can be used to assess disease progression as well as response to treatment in people with FSHD. RWS evaluates shoulder and proximal arm mobility by utilizing 3D motion sensor technology to track upper limb trajectory across five regions. The use of RWS as a primary outcome measure is significant as historically, primary outcomes in studies have not always represented clinically meaningful outcomes for muscular dystrophy patients. The decision to use RWS as a primary outcome is clinically meaningful as the condition causes progressive loss of range of motion in patients’ shoulders and arms, which impacts basic daily tasks such as cooking, getting dressed, opening the door, etc. It was important to many patients Ms. McNary spoke with that any potentially approved therapy for FSHD have a positive impact on RWS. Fulcrum Therapeutics recently announced data from two phase 2 clinical trials that demonstrated that losmapimod preserved or improved function in people with FSHD, as measured by RWS.

To learn more about FSHD and other rare musculoskeletal diseases, visit