Japanese filing of gabapentin enacarbil for RLS triggers $5 million milestone from Astellas to XenoPort

Japanese drug major Astellas Pharma has filed a New Drug Application with the Pharmaceuticals and Medical Device Agency (PMDA) in Japan for ASP8825 (gabapentin enacarbil), also known as XP13512, as a potential treatment for restless legs syndrome (RLS).

The acceptance of the NDA submission triggers a $5 million milestone payment from Astellas to XenoPort, the US firm which granted Astellas rights to the drug in Japan and other Asian countries in December 2005.

The data supporting safety and efficacy in the NDA filing comes from the successful Phase II study in RLS patients and long-term safety study conducted by Astellas in Japan and the RLS clinical program conducted by XenoPort in the USA.

'We are pleased to submit the NDA for ASP8825 in Japan,' said Masafumi Nogimori, Astellas' president and chief executive. 'We look forward to delivering this new treatment to patients suffering from RLS in Japan.'

'Astellas has made great progress in advancing its RLS development program,' said Ronald Barrett, XenoPort's chief executive, noting that, 'if approved, ASP8825 could be an important new treatment for patients with RLS in Japan.'

Astellas holds exclusive rights to develop and commercialize XP13512 in Japan, Korea, the Philippines, Indonesia, Thailand and Taiwan. Under the terms of the Astellas collaboration agreement, XenoPort received an initial license payment of $25 million in December 2005 and, prior to the latest announcement, has received milestone payments of $18 million.

XenoPort is eligible to receive potential clinical and regulatory milestone payments totaling up to an additional $42 million. In addition, assuming regulatory approval, the US firm is entitled to receive royalties on any sales of XP13512 in the Astellas