Muscle Ultrasound in an Open-Label Study of Losmapimod in Subjects with FSHD1


Clinical Trials

Poster Number: 126


Joost Kools, MD, Radboud University Medical Centre (Radboudumc), Nijmegen, NL, Nicol Voermans, MD, PhD, Radboud University Medical Centre (Radboudumc), Karlien Mul, MD, Radboud University Medical Centre (Radboudumc), John Jiang, PhD, Fulcrum Therapeutics, Kelly Marshall, Fulcrum Therapeutics, Markus Karlsson, PhD, AMRA Medical AB, Linköping, Sweden

Objective: Evaluate muscle ultrasound (US) in an open-label trial of losmapimod in FSHD1 patients. Background: Natural history studies have identified US as a viable imaging biomarker for FSHD muscle progression, complementary to MRI. Losmapimod is an orally active, selective, small molecule inhibitor of p38α/β. Methods: Fourteen subjects ages 18 to 65 years with genetically confirmed FSHD1, clinical severity score 2 to 4 (range 0-5) and MRI-eligible skeletal muscles for needle biopsy received open-label 15 mg twice daily losmapimod for 52 weeks with the primary objective of safety. Assessments included safety, MRI, US, clinical outcomes, and Patient Reported Outcomes. US was performed on 7 muscles bilaterally using a standardized protocol. US echointensity was expressed as a z-score relative to matched healthy controls, with abnormal being defined as >2. Results: The mean (SD) change from baseline in echogenicity of all muscles was -0.17 (0.9), in the upper extremity muscles -0.32 (0.9) and lower extremities -0.13 (1.0), represented a trend towards improvement. The distribution of muscle z-scores (<2, 2-4, 4-6, and >6) at baseline and after 52 weeks of treatment remained the same. Echointensity correlated strongly with MFI for the biceps brachii (r=0.84, p<0.01), tibialis anterior (r=0.76, p<0.01), and gastrocnemius medialis (r=0.50, p<0.01). Correlations between US and clinical outcomes will be presented. Conclusions: Losmapimod demonstrated stability in muscle US over 52 weeks.