Amifampridine phosphate (Firdapse(®)) is effective and safe in a phase 3 clinical trial in LEMS.

OBJECTIVE: We evaluated the efficacy and safety of amifampridine phosphate (Firdapse(®)) for symptomatic treatment in Lambert-Eaton myasthenic syndrome (LEMS).

METHODS: Phase 3, randomized, double-blind, study. Patients were treated initially with amifampridine phosphate for 7-91 days, followed by randomization to continue amifampridine phosphate for 14 days or placebo (7-day taper, 7-day placebo). The primary efficacy endpoints were changes from baseline at day 14 in Quantitative Myasthenia Gravis and Subject Global Impression scores.

RESULTS: The coprimary efficacy end points and 1 of the secondary efficacy end points were met, showing a significant benefit of aminfampridine phosphate over placebo at Day 14. All 5 primary, secondary, and tertiary endpoints achieved statistical significance at Day 8. Amifampridine phosphate was well tolerated; the most common adverse events were oral and digital paresthesias, nausea, and headache.

CONCLUSIONS: This study provides Class I evidence of efficacy of amifampridine phosphate as a symptomatic treatment for LEMS.