Firdapse Approved to Treat Rare Autoimmune Disorder

November 28, 2018 – The U.S. FDA has approved Firdapse® (amifampridine), manufactured by Catalyst Pharmaceuticals, Inc., to treat adult patients who have Lambert-Eaton myasthenic syndrome (LEMS), a rare autoimmune disorder. Firdapse is the first FDA-approved treatment for LEMS.

Approximately 400 individuals in the United States have LEMS, a disease in which the body’s immune system attacks the connections between nerves and muscles. This can lead to weakness and fatigue, reduced tendon reflexes, and difficulty breathing, speaking, or swallowing, among other symptoms. Roughly 60% of LEMS cases are associated with small cell lung cancer (SCLC), with the LEMS diagnosis typically preceding the cancer diagnosis. Most patients who develop both LEMS and SCLC are older, and have a long history of smoking. For patients who develop LEMS but not an associated cancer, onset can occur at any age.

In clinical trials, patients treated with Firdapse received greater benefit than those given a placebo. Treatment efficacy was measured using the Quantitative Myasthenia Gravis score, a 13-item physician-rated categorical scale that assessed muscle weakness, and Subject Global Impression, a seven-point scale on which patients rated their overall impression of the effects of the study treatment on their physical well-being.

The recommended total daily dose is 15mg to 30mg initially, taken in divided doses three to four times during the day. Patients should take no more than 20mg at one time. If needed, the total daily dose can be increased by 5mg every three or four days, up to a maximum of 80mg per day. Patients with renal or hepatic impairment, or who are known N-acetyltransferase 2 (NAT2) poor metabolizers, should begin treatment at the 15mg/day dose.

Firdapse will be available in 10mg scored tablets. Catalyst plans to launch the product in early 2019. Pricing plans have not been announced.