FDA Approves First Therapy for LEMS

The US Food and Drug Administration (FDA) has approved amifampridine (Firdapse) tablets as the first ever treatment of the rare autoimmune disorder Lambert-Eaton myasthenic syndrome (LEMS) in adults.

LEMS, distinguished by its damage to the connection between nerves and muscles, is capable of disrupting the nerve cells’ ability to send signals to muscle cells. It most commonly presents in patients with small cell lung cancer—either preceding or coinciding with the cancer diagnosis. It is associated with other autoimmune conditions, and is estimated to be prevalent in approximately 3 million people worldwide.

Its efficacy was studied in a pair of clinical trials involved 64 adult patients administered either amifampridine or placebo. Using the 13-item, physician-rated categorial Quantitative Myasthenia Gravis scale to assess for muscle weakness, as well as the seven-point, patient-rated Subject Global Impression, investigators assessed the therapy’s benefit for LEMS’ most prevalent symptoms.

For both measures, patients treated with amifampridine reported greater benefits than those administered placebo. The most prevalent side effects included paresthesia, upper respiratory tract infection, abdominal pain, nausea, diarrhea, headache, elevated liver enzymes, back pain, hypertension, and muscle spasms.

Prior to the approval, amifampridine was granted Priority Review and Breakthrough Therapy designations by the FDA—as well as an Orphan Drug Designation for its potential as a rare disease therapy.

In a statement included with the announced approval, Billy Dunn, MD, director of the Division of Neurology Products in the FDA’S Center for Drug Evaluation and Research, noted the burdens faced by the 3 million-patient population.

“There has been a long-standing need for a treatment for this rare disorder,” Dunn said. “Patients with LEMS have significant weakness and fatigue that can often cause great difficulties with daily activities.”