FDA reviews GSK's response to Complete Response letter for Horizant

GlaxoSmithKline (NYSE: GSK) and XenoPort, Inc. (Nasdaq: XNPT) announced today that the U.S. Food and Drug Administration (FDA) has accepted for review GSK's response to FDA's Complete Response letter for Horizant™ (gabapentin enacarbil) Extended-Release Tablets. Horizant is under review for the treatment of moderate-to-severe primary Restless Legs Syndrome (RLS).

FDA has designated the resubmission as a Class 2 response and set a new Prescription Drug User Fee Act goal date of April 6, 2011.

Last month, GSK submitted its response to questions raised by FDA in a Complete Response letter dated February 17, 2010. GSK's response to FDA included new data from nonclinical studies of Horizant and two epidemiology studies, conducted by GSK, exploring gabapentin use and cancer based on the UK General Practice Research Database. The resubmission also included a final safety update that provided updated or new safety information on patients in clinical studies who have been treated with Horizant. In order for FDA to be able to consider published gabapentin nonclinical data in their assessment of Horizant, GSK amended the New Drug Application (NDA) for Horizant from a 505(b)(1) to a 505(b)(2) application.

Horizant, also referred to as GSK1838262/XP13512, is a patented new chemical entity. It is an investigational non-dopaminergic treatment for moderate-to-severe primary RLS. It is not approved or marketed anywhere in the world.

The NDA was submitted to FDA on January 9, 2009.