XenoPort has now earned $65 million through its deal with Astellas.

XenoPort will receive a $10 million milestone payment from partner Astellas Pharma on the latter’s achievement of Japanese regulatory approval for Regnite® (gabapentin enacarbil) as a treatment for moderate-to-severe primary restless legs syndrome (RLS).

Clearance by Japan’s regulator was based on data from a Phase II study in RLS patients, and a long-term safety study carried out by Astellas in Japan, along with the RLS clinical program conducted by XenoPort in the U.S., and additional pharmacokinetic studies in Japanese patients.

Regnite is a once-daily, oral small molecule compound that was originally discovered by XenoPort. Once absorbed, the drug is converted into gabapentin, which binds to specific proteins that regulate neuronal activity. In 2005 Astellas negotiated exclusive rights to develop and commercialize Regnite in Japan, Korea, the Philippines, Indonesia, Thailand, and Taiwan. The $10 million milestone payment received by XenoPort on Japanese approval of the drug for the RLS indication takes to $65 million the total milestones received by the firm under the collaboration agreement with Astellas. XenoPort could in addition earn up to another $20 million in clinical and regulatory milestones, plus double-digit royalties on sales of the drug in the latter’s territories.

GlaxoSmithKline holds exclusive development and commercialization rights to gabapentin enacarbil in the U.S., where the drug is under mid-late-stage development as a treatment for post-herpetic neuralgia.

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