FDA OKs First Treatment for Kids With Lambert-Eaton Myasthenic Syndrome

Megan Brooks

Disclosures

May 08, 2019

The US Food and Drug Administration (FDA) has approved the first treatment for children with Lambert-Eaton myasthenic syndrome (LEMS), a rare autoimmune disorder.

Amifampridine (Ruzurgi, Jacobus Pharmacuetical) is an oral potassium channel blocker indicated for children and adolescents aged 6 years to less than 17 years who have LEMS.

The FDA first approved amifampridine tablets (Firdapse, Catalyst Pharmaceuticals) for adults with LEMS in November 2018, as reported by Medscape Medical News.

"We continue to be committed to facilitating the development and approval of treatments for rare diseases, particularly those in children," Billy Dunn, MD, director of the Division of Neurology Products in the FDA's Center for Drug Evaluation and Research, said in a news release. "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 Dunn.

LEMS affects the connection between nerves and muscles and causes weakness and other symptoms in affected patients. LEMS may be associated with other autoimmune diseases but more commonly occurs in patients with small–cell lung cancer. In these patients, its onset precedes or coincides with the diagnosis of cancer.

The prevalence of LEMS in pediatric patients is not known, but the overall prevalence of LEMS is estimated to be three per 1 million individuals worldwide, according to the FDA.

The agency says use of Ruzurgi in patients aged 6 years to less than 17 years is supported by evidence from studies conducted in adults with LEMS as well as pharmacokinetic modeling and simulation to identify the appropriate dosing regimen for children and to determine safety data for children.

The effectiveness of amifampridine for the treatment of LEMS was established in a randomized, double-blind, placebo-controlled withdrawal study of 32 adults who took amifampridine for at least 3 months prior to entering the study. Effectiveness was measured by the degree of change in scores on the Timed Up and Go Test. Patients who continued to take amifampridine instead of switching to placebo experienced less impairment than those who took placebo.

Effectiveness was also measured with a self-assessment scale for LEMS-related weakness that evaluated the feeling of weakening or strengthening. The scores indicated greater perceived weakening in the patients who switched to placebo.

The most common side effects experienced by pediatric and adult patients taking amifampridine were paresthesia, abdominal pain, indigestion, dizziness, and nausea. Side effects reported in children were similar to those seen in adult patients. Seizures have been observed in patients who do not have a history of seizures.

The drug received breakthrough and orphan drug designation and priority review.

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