FDA Accepts NDA & Grants Priority Review Status for Amifampridine Phosphate for LEMS

The US Food and Drug Administration (FDA) has accepted for Priority Review Catalyst Pharmaceuticals’ New Drug Application (NDA) for amifampridine phosphate (Firdapse), to treat those with the rare autoimmune disorder, Lambert-Eaton myasthenic syndrome (LEMS).

“We are delighted to have received Priority Review status for Firdapse for the treatment of LEMS and look forward to continuing to work closely with the FDA during the review process,” Catalyst’s chairman and CEO Patrick J. McEnany, said in a recent statement. “Together, with the previous grant of Breakthrough Therapy Designation, the Priority Review underscores the robust potential of Firdapse and the need for a safe and effective FDA-approved treatment for LEMS.”

The submission is supported by positive results from 2 phase 3 studies.

In those with LEMS, the body’s immune system hinders the ability of nerve cells to send signals to muscle cells. The disorder is often characterized by the gradual onset of muscle weakness and decreased tendon reflexes, making it difficult to climb stairs, lift objects, talk, or chew.

Amifampridine phosphate is described as a “nonspecific, voltage-dependent, potassium (K) channel blocker that causes depolarization of the presynaptic membrane and slows or inhibits repolarization,” according to Catalyst. By doing this, it opens slow voltage-dependent calcium channels (Ca²⁺), which allows for more Ca²⁺ to get through. It also prompts the exocytosis of ACh-containing synaptic vesicles to release more ACh into the synaptic cleft, which, in turn, works to boost neuromuscular transmission and improve muscle function.

Previous to the FDA accepting the NDA for amifampridine phosphate, it was approved by the European Medicines Agency for the treatment of LEMS. In fact, the European Federation of Neurological Societies recommends it as first-line treatment for those with the disorder.

The Prescription Drug User Fee Act (PDUFA) action date for the treatment has been set to November 28, 2018.

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