TOKYO & SANTA CLARA, Calif.--(BUSINESS WIRE)--Astellas Pharma Inc. and XenoPort, Inc. (NASDAQ:XNPT) today announced that a new drug application (NDA) has been filed 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 data supporting safety and efficacy in the NDA filing comes from the successful Phase 2 study in RLS patients and long-term safety study conducted by Astellas in Japan and the RLS clinical program conducted by XenoPort in the United States. The acceptance of filing of the NDA triggers a $5 million milestone payment from Astellas to XenoPort.