GlaxoSmithKline and XenoPort, Inc announced that the New Drug Application (NDA) for Solzira (gabapentin enacarbil) extended release tablets for the treatment of moderate-to-severe primary restless legs syndrome (RLS) has been withdrawn. The United States Food and Drug Administration (FDA) has requested that the data in a single study be reformatted. In addition, GSK will conduct a review of other trial data sets taking this input into account. The withdrawal does not relate to the content of the filing. GSK plans to resubmit the NDA quickly once this work is complete.

The resubmission will lead to a delay in the receipt by XenoPort of milestone payments of $23 million in the aggregate from GSK and Astellas Pharma Inc, which are associated with the acceptance by the FDA of the NDA for Solzira.

Solzira is a new chemical entity that is designed to improve upon the pharmacokinetics of gabapentin by taking advantage of high-capacity transport mechanisms in the gastrointestinal tract to improve absorption.

XenoPort is a biopharmaceutical company focused on developing a portfolio of internally discovered product candidates that utilize the body's natural nutrient transport mechanisms to improve the therapeutic benefits of existing drugs.