Catalyst Pharmaceuticals (CPRX) said Tuesday that its sub-licensee, DyDo Pharma, has launched Firdapse, or amifampridine, tablets 10 mg in Japan to treat muscle weakness in patients with Lambert-Eaton myasthenic syndrome, or LEMS, a rare autoimmune disorder.

Firdapse is the only treatment approved by the US Food and Drug Administration for LEMS in adults and pediatric patients aged six and older, and it is supported by a comprehensive patient support program in the US to ensure accessibility for eligible patients, the company said.

Shares of Catalyst Pharmaceuticals were down 1% in recent trading.

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