First-in-Class Drug Approved for Lambert-Eaton Myasthenic Syndrome

Firdapse was previously granted Orphan Drug designation and Breakthrough Therapy designation, as well as Priority Review by the FDA.

The Food and Drug Administration (FDA) has approved Firdapse (amifampridine; Catalyst), a first-in-class treatment for adults with Lambert-Eaton myasthenic syndrome (LEMS).

Amifampridine is a nonspecific, voltage-dependent, potassium channel blocker was evaluated in 2 randomized, double-blind, placebo-controlled trials (N=64) in adults with confirmed LEMS. The co-primary efficacy endpoints were the change from baseline to the end of the discontinuation period in the Quantitative Myasthenia Gravis (QMG) score and the Subject Global Impression (SGI) score. 

In Study 1, patients in the placebo group had a significantly greater worsening of muscle weakness and of global impression of the effects of the study treatment on their physical well-being vs patients who received Firdapse (change in QMG: 2.2 vs 0.4, P =.045; change in SGI -2.6 vs -0.8; P =.003)

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In Study 2, patients treated with Firdapse were randomized to either continue treatment or change to placebo for 4 days. From baseline to Day 4, there was significantly greater worsening in the QMG score in the placebo group vs the Firdapse arm (6.54 vs 0.00; P =.0004). Also, there was significantly greater worsening in the SGI score in the placebo group vs the Firdapse group (-3.59 vs -0.64; P =.0003). 

Paresthesia, upper respiratory tract infection, abdominal pain, nausea, diarrhea, headache, elevated liver enzymes, back pain, hypertension, and muscle spasms were the most commonly reported adverse events.  

Firdapse will be available as 10mg tablets in 10-count blister packs and as 60- and 240-count bottles. 

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