FDA will consider request to raise Firdapse’s maximum daily dose

Catalyst asks that 100 mg of the therapy, rather than 80 mg, be available

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by Steve Bryson, PhD |

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The U.S. Food and Drug Administration (FDA) has agreed to review Catalyst Pharmaceuticals’ request to raise to 100 mg the maximum recommended daily dose of Firdapse (amifampridine), its approved treatment for Lambert-Eaton myasthenic syndrome (LEMS).

Firdapse’s label allows for an 80 mg maximum daily dose in adults and children, ages 6 and older, weighing 45 kg (about 99 lbs) or more. Among children weighing less than 45 kg, the maximum dosage is 40 mg per day.

An FDA decision on the request, submitted in the form of a supplemental new drug application (sNDA), is expected on or before June 4, 2024.

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“We are pleased by the Agency’s acceptance of the sNDA filing for Firdapse, marking yet another milestone in the advancement of our initiative to address an important need of LEMS patients and their physicians who desire an increased daily dosage,” Patrick J. McEnany, Catalyst’s chairman and CEO, said in a company press release. “We look forward to working collaboratively with the Agency during the application review process.”

LEMS occurs when the immune system mistakenly attacks a specific type of calcium channel protein found in the nerve cells responsible for controlling muscle movement. Marked by muscle weakness that starts in the lower limbs, people with LEMS have difficulties walking and climbing stairs. As the disease progresses, the arms and shoulders also are affected.

About half of LEMS cases are associated with a type of lung cancer called small-cell lung cancer, or SCLC. It is thought that antibodies that the immune system generates to eliminate cancer cells, which also harbor the same calcium channels, wrongly target these channel proteins on nerve cells, leading to LEMS symptoms.

Firdapse is designed to block another type of nerve cell protein channel, helping to ensure that remaining healthy calcium channels stay open and functional. This is expected to improve communication between nerves and muscles, and enhance muscle strength.

Approved in the U.S. in 2018 for LEMS patients ages 17 and older, Firdapse’s use expanded in 2022 to include patients as young as age 6.

“Firdapse has proven to be an important therapeutic option for individuals in the U.S. affected by LEMS, including those comorbid with small-cell lung cancer,” McEnany said. “If approved, this will offer additional indicated dosage options for LEMS patients who may benefit from a Firdapse daily dosage greater than 80mg.”

The medication also is available for adults with LEMS in Europe and Canada. In Japan, data from an ongoing Phase 3 clinical study, expected to be reported by the end of the year, aims to support Catalyst’s plans to expand the therapy’s availability to LEMS patients in Asian countries.