The Food and Drug Administration (FDA) has approved Ruzurgi (amifampridine; Jacobus Pharmaceutical) for the treatment of Lambert-Eaton myasthenic syndrome (LEMS) in patients 6 to <17 years of age.

Ruzurgi contains amifampridine, a broad spectrum potassium channel blocker. The mechanism by which amifampridine exerts its therapeutic effect in LEMS patients has not been fully elucidated.

The use of Ruzurgi for pediatric patients was based on evidence from clinical studies evaluating the treatment in adults. Data from these trials were used to identify a dosing regimen for younger patients. Amifampridine is marketed under the brand name Firdapse (Catalyst) for adult patients with LEMS.

The approval of Ruzurgi was based on data from a placebo-controlled withdrawal study conducted in 32 adult patients who were taking Ruzurgi for ≥3 months before entering the study; patients either continued on Ruzurgi or were switched to placebo. Results showed that those who continued with the treatment experienced less impairment based on a test that assessed the time it took to rise from a chair, walk 3 meters, and return to the chair 3 consecutive times without stopping.

In addition, compared with patients who continued treatment with Ruzurgi, those in the placebo group reported greater perceived weakening, according to scores derived from a self-assessment scale for LEMS-related weakness.

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With regard to safety, the most common adverse reactions experienced by both pediatric and adult patients were paresthesia, abdominal pain, indigestion, dizziness, and nausea.

“This approval will provide a much-needed treatment option for pediatric patients with LEMS who have significant weakness and fatigue that can often cause great difficulties with daily activities,” said Billy Dunn, MD, director of the Division of Neurology Products in the FDA’s Center for Drug Evaluation and Research.

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