Treatment for Congenital Myasthenic Syndromes Fails to Meet Primary Endpoint in Phase 3 Clinical Trial

Although participant improvements were observed in some subgroups, the trial did not improve its primary endpoint of subject global impression (SGI) or the secondary endpoint of muscle function measure (MFM) across all tested subtypes. 

In phase 3 of the CMS-001 trial (NCT02562066),  amifampridine phosphate (Firdapse; Catalyst Pharmaceuticals, Inc., Coral Gables, FL) did not meet endpoints for treating genetically confirmed Congenital Myasthenic Syndromes (CMS) in adults and children of 2 years and above.  

The trial, which took nearly 4 years to enroll 20 participants because of the rarity of the disease, was a placebo-controlled, 2-period, 2-treatment crossover study designed to evaluate the efficacy and safety of amifampridine phosphate. Amifampridine phosphate is approved by the FDA for the treatment of Lambert-Eaton Myasthenic Syndrome (LEMS) in the participants. 

“While we are disappointed that this trial did not reach its primary or secondary endpoints in the evaluated CMS patient subtypes, we are pleased with the new valuable clinical information that these results will provide to the medical and scientific communities as we work to develop FDA-approved treatment options for patients with this disease” said Patrick J. McEnany, chairman and CEO, Catalyst Pharmaceuticals. “We also remain committed to developing FDA-approved treatment options for other rare neuromuscular disorders.”