FDA Approves First Treatment for Pediatric Lambert-Eaton Myasthenic Syndrome

The FDA has granted approval to the first treatment for children with Lambert-Eaton myasthenic syndrome (LEMS), a rare autoimmune disorder. The drug, amifampridine (Ruzurgi), is approved for the treatment of patients aged 6 years to less than 17 years.

LEMS affects the connection between nerves and muscles, causing weakness and other symptoms, and causing the immune system to attack the neuromuscular junction, which disrupts the ability of nerve cells to send signals to muscles.

“We continue to be committed to facilitating the development and approval of treatment for rare diseases, particularly those in children,” said Billy Dunn, MD, director of the Division of Neurology Products in the FDA’s Center for Drug Evaluation and Research, in a statement. “The approval will provide a much-needed treatment option for pediatric patients with LEMS who have significant weakness and fatigue that often cause great difficulties with daily activities.”

The only other treatment approved for the disorder is only approved for the treatment of adults. According to STAT News, the approval might bring unforeseen but welcome competition to the already approved treatment, which was approved last December and comes with a list price of $375,000, depending on total dosing. Jacobus Pharmaceuticals, who markets amifampridine, has yet to release its list price.

The approval was supported by studies of the drug in adults with LEMS, pharmacokinetic data in adult patients, pharmacokinetic modeling and simulation to identify appropriate doing in pediatric patients, and safety data from pediatric patients aged 6 years to less than 17 years.

In a randomized controlled trial, the drug demonstrated efficacy among 32 patients who were taking the tablets for at least 3 months prior to enrolling in the study. Comparing patients who stayed on the drug to those who switched to placebo, patients who continued amifampridine experienced less impairment than those taking placebo.

Effectiveness was measured by the degree of change in the time it took the patient to rise from a chair, walk 3 meters, and return to the chair for 3 consecutive laps without pause. It was also measured by a self-assessment scale for LEMS-related weakness that assessed the feeling of weakening of strengthening. Scores indicating greater perceived weakening were more prevalent among those taking placebo.

The most common side effects of the drug experienced by both adult and pediatric patients included burning or prickling sensation, abdominal pain, indigestion, dizziness, and nausea. According to data, reported side effects in pediatric patients were similar to that seen in adult patients.