The FDA has approved amifampridine tablets (Ruzurgi, Jacobus Pharmaceutical Company) for the treatment of Lambert-Eaton myasthenic syndrome (LEMS) in pediatric patients aged 6 years to less than 17 years. Amifampridine is the first FDA-approved treatment specifically for children with LEMS.
LEMS is a rare autoimmune disorder affecting the connection between nerves and muscles, causing weakness, fatigue, and other symptoms in affected patients. Although it can be associated with other autoimmune diseases, LEMS usually occurs in patients with cancer, such as small-cell lung cancer; its onset precedes or coincides with the cancer diagnosis.
The prevalence of LEMS specifically in children is not known, but overall cases are estimated at three per million individuals worldwide.
The use of amifampridine in pediatric patients is supported by evidence from adequate and well-controlled studies of the drug in adults with LEMS; pharmacokinetic data from adult patients; pharmacokinetic modeling and simulation to identify the dosing regimen in pediatric patients; and safety data from children aged 6 to less than 17 years.
Amifampridine’s effectiveness was shown in a randomized, double-blind, placebo-controlled withdrawal study of 32 adults taking amifampridine for at least three months prior to study entry. The study compared patients continuing on amifampridine with patients who had switched to placebo.
In a test assessing the time participants took to rise from a chair, walk three meters, and return to the chair, the amifampridine patients were less impaired than placebo patients. Also, scores from a self-assessment scale for LEMS-related weakness that evaluated the feeling of weakening or strengthening suggested that placebo patients perceived a greater weakening than amifampridine patients.
The most common side effects of amifampridine in pediatric and adult patients were paresthesia, abdominal pain, indigestion, dizziness, and nausea. Side effects reported in children were similar to those in adult patients.
The FDA granted amifampridine priority review, fast track, and orphan drug designations.
Source: FDA, May 6, 2019