Catalyst Pharmaceuticals Submits NDA for LEMS Treatment

Today, Catalyst Pharmaceuticals announced its submission of a New Drug application (NDA) to the U.S. Food and Drug Administration (FDA) for amifampridine phosphate (Firdapse) for the treatment of Lambert-Eaton myasthenic syndrome (LEMS).

LEMS is a rare autoimmune disease in which antibodies form against voltage-gated potassium channels in between the nerves and muscles they communicate with. The disease usually effects the extremities, especially the legs, making movement difficult. It also disrupts the autonomic nervous system.¹ Amifampridine phosphate is a nonspecific voltage-dependent potassium (K⁺) channel blocker, causing depolarization of the presynaptic membrane while slowing or inhibiting repolarization.

The effects of the drug occur in the opening of slow voltage-dependent calcium (Ca²⁺) channels, making the exocytosis of synaptic vessels containing ACh induced to release more Ach into the synaptic cleft. This reaction enhances neuromuscular transmission, thus, improving muscle function.³

Hope for the drug’s future is further supported by its Phase 3 clinical trial in patients with LEMS (in which it was found effective and safe).

The study consisted of 4 parts with multiple doses of amifampridine phosphate, and the efficacy and safety of amifampridine phosphate in patients with LEMS served as the primary endpoint.

Participants were divided into 2 study arms. The experimental arm was administered 30-80 mg of amifampridine phosphate 3-4 times a day with a maximum dose of 20 mg (2 x 10 mg tablets) for 2 weeks while the placebo comparator arm was administered placebo tablets 3-4 times a day for 2 weeks.²

Among the data collected from the enrolled 38 adult participants, primary data included a 25 Foot Walking Test (T25FW) and a 7-point CGI I Score, which were both recorded at days 0 (baseline), 8, and 14. The T25FW consisted of a 25-foot walking component that included 2 walks 5 minutes apart. The average speed, which was expressed in feet/minutes, was the measurement of the 2 completed walks. The 7-point CGI I Score ranged on a scale from 1 (very much improved) to 7 (very much worse).²

Patrick J. McEnany, Chairman and Chief Executive Officer of Catalyst Pharmaceuticals, Inc., states his optimism with the drug’s orphan designation by the FDA. “We are pleased to reach this regulatory milestone and believe that our NDA submission contains all of the necessary information to satisfy the FDA requirements. This important milestone is the culmination of a strong collaboration and commitment among the patients, physicians and Catalyst employees who have worked diligently to advance Firdapse and to further expand access to an FDA-approved product to all LEMS patients. We look forward to continuing to work with the FDA during the review process and to a potential future launch of Firdapse, if it is approved.”¹

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References:

1. “Catalyst Pharmaceuticals Announces Submission of New Drug Application for Firdapse for Treatment of Lambert-Eaton Myasthenic Syndrome.” GlobeNewswire. 29, Mar. 2018.
2. “A Phase 3 Study of Amifampridine Phosphate in Patients With Lambert Eaton Myasthenic Syndrome (LEMS).” NIH. 4, Jan. 2018.
3. “Amifampridine Phosphate.” Catalyst Pharmaceuticals.