Catalyst Given US Patent Covering Firdapse in Treating LEMS

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by David Melamed, PhD |

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The U.S. Patent and Trademark Office has issued a new patent to Catalyst Pharmaceuticals covering the company’s rights to Firdapse (amifampridine), a treatment for Lambert-Eaton myasthenic syndrome (LEMS).

The patent (No. 10,793,893), “Methods of administering 3,4-diaminopyridine,” expires on April 7, 2034.

Catalyst’s rights over Firdapse had been guaranteed by the U.S. Food and Drug Administration (FDA) through the agency having designated Firdapse an orphan drug, which grants seven years of market exclusivity.

“We are pleased that our patent for Firdapse (amifampridine) has issued and believe that it will create significant barriers to therapeutically equivalent generic competition from entering the market for approximately nine years beyond orphan drug exclusivity,” Patrick J. McEnany, chairman and CEO of Catalyst, said in a press release.

Firdapse is the first treatment for adults with LEMS approved by the FDA, and to date their only approved treatment. It is also available for LEMS patients in the European Union, Canada, and elsewhere.

The transmission of signals between the nervous system and muscles occurs at the neuromuscular junction, where motor neurons and muscle fibers meet, and relies on the activity of proteins called voltage-gated calcium channels and voltage-gated potassium channels.

In patients with LEMS, autoantibodies target calcium channels at nerve endings, preventing the uptake of calcium ions and ultimately weakening the communication with muscles. Firdapse, an oral medication, is designed to block the potassium channels, which opens the remaining calcium channels and promotes muscle function.

The active ingredient is Firdapse is amifampridine, also known as 3,4-diaminopyridine (3,4-DAP), a small molecule able to increase muscular activity.

Firdapse is broken down by the enzyme N-acetyltransferase 2 (NAT-2). The rate at which NAT-2 breaks down amifampridine is unique to each patient, which makes dosing crucial.

The patent issued covers suitable dosing regimens for patients who break down amifampridine slowly.

“This patent is directed to innovative methods of administering amifampridine to slow metabolizers of amifampridine,” said Steven Miller, PhD, the company’s chief operating and chief scientific officer.

Firdapse’s recommended starting dose is 15 mg to 30 mg daily, taken as separate doses three to four times daily, with a maximum total dose of 80 mg daily and maximum single daily dose of 20 mg, according to its FDA label.

Catalyst is also investigating Firdapse as a treatment for other neuromuscular conditions, including MuSK antibody-positive myasthenia gravis and spinal muscular atrophy type 3. Firdapse was also designated an orphan drug for myasthenia gravis by the FDA.

“We remain committed to serving the neuromuscular community by continuing to investigate Firdapse for other rare neurodegenerative diseases,” McEnany said. “We also look forward to results from various investigator-sponsored trials that, if positive, will strengthen the value proposition for the use of Firdapse.”