Catalyst to file FDA request soon for increase to maximum Firdapse dose

Company seeks to raise maximum recommended daily dose to 100 mg

Andrea Lobo, PhD avatar

by Andrea Lobo, PhD |

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Catalyst Pharmaceuticals is on track to submit an application requesting an increase to the maximum recommended daily dose of Firdapse (amifampridine) — its approved treatment for Lambert-Eaton myasthenic syndrome (LEMS) — from 80 to 100 mg.

Currently, the maximum daily dosage of Firdapse is 80 mg for adults and children weighing at least 45 kg (around 99 pounds), according to its label. The maximum recommended dosage for children weighing less than 45 kg is 40 mg daily.

The company recently had a type C meeting with the U.S. Food and Drug Administration (FDA) to discuss its plans for a supplemental new drug application (sNDA) requesting the approval of the higher dose.

Based on feedback from the meeting, the company believes it now has the necessary information to move forward with the application later this year.

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“We thank the Agency for their collaboration in reviewing our submitted materials and providing their feedback,” Patrick J. McEnany, chairman and CEO at Catalyst, said in a company press release. “Based on the positive outcome of the meeting, we remain on track to file an sNDA submission early in the third quarter of 2023.”

“If approved, we believe this change will address an important need for LEMS patients, caregivers, and physicians who may benefit from an optimized therapy,” he added.

LEMS is a rare autoimmune disease mainly characterized by muscle weakness in the limbs. It is caused by an autoimmune attack directed against a specific type of calcium channel found at nerve endings, called voltage-gated calcium channels, which play a key role in muscle movement control.

Calcium channels are required for the release of acetylcholine, a chemical messenger that instructs muscles to contract. Failure to release enough acetylcholine results in muscle weakness and fatigue.

Firdapse is a small molecule that blocks another type of protein channel found on nerve cells, called voltage-dependent potassium channels. This causes any remaining healthy calcium channels to stay open, allowing calcium to enter nerve cells and potentially increasing the amount of acetylcholine released. This, in turn, is expected to enhance muscle strength.

Firdapse is the first and only oral therapy approved in the U.S. for the symptomatic treatment of LEMS. It was originally approved by the FDA in November 2018 to treat LEMS patients 17 and older. Its approval was expanded in October 2022 to include children as young as 6.

The medication is also approved for adults with LEMS in Europe and Canada.

As part of Catalyst’s plans to expand the availability of Firdapse to Asian countries, a Phase 3 clinical study is ongoing in Japan, which is expected to be complete by the end of the year.