FDA approves increasing Firdapse’s maximum daily dose to 100 mg

New dose is for adults and children who weigh at least 99 pounds

Andrea Lobo, PhD avatar

by Andrea Lobo, PhD |

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The U.S. Food and Drug Administration (FDA) has approved increasing from 80 to 100 mg the maximum recommended daily dose of Firdapse (amifampridine) for adults and children weighing at least 45 kg (about 99 pounds) with Lambert-Eaton myasthenic syndrome (LEMS).

The decision follows a supplemental new drug application (sNDA) request by Catalyst Pharmaceuticals, which markets the therapy. Before the change, Firdapse’s label allowed for a maximum daily dose of 80 mg in adults and children, ages 6 and older, who weighed at least 45 kg, and 40 mg in children under 45 kg.

“This pivotal achievement further underscores our dedication to meeting the evolving needs of LEMS patients and their healthcare providers,” Richard J. Daly, Catalyst’s president and CEO, said in a company press release. “We believe that this milestone will have a meaningful impact on the lives of LEMS patients, offering a new level of flexibility in treatment while aligning with our overarching mission to optimize LEMS patient outcomes.”

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More flexibility for healthcare providers

LEMS is an autoimmune disease that occurs when the immune system mistakenly attacks voltage-gated calcium channels (VGCCs), a specific type of calcium channel, found at nerve endings at the neuromuscular junction where nerve and muscle cells communicate to control muscle movements.

Calcium channels are required for the release of acetylcholine, a chemical messenger released by nerve cells to instruct muscles to contract. Failure to release enough acetylcholine causes muscle weakness, usually starting in the lower limbs, with patients having difficulties walking and climbing stairs. As the disease progresses, the arms and shoulders also are affected.

Firdapse is an oral therapy that blocks other protein channels on nerve cells called voltage-dependent potassium channels. This helps the remaining healthy VGCCs stay open and functional, which should improve nerve-muscle communication and enhance muscle strength.

Firdapse was first approved in the U.S. in 2018 for LEMS patients ages 17 and older. That approval was extended in 2022 to include children as young as 6. It’s also approved to treat LEMS in Europe and Canada, and is under review in Japan, where a decision is expected later this year.

The approved increase in the maximum daily dose offers healthcare providers and patients more flexibility in treatment regimens for managing LEMS symptoms, according to Catalyst.