GSK, XenoPort Get Complete Response Letter for RLS Drug

GlaxoSmithKline and XenoPort, Inc. received a Complete Response letter from the FDA regarding the NDA for Horizant (gabapentin enacarbil) Extended-Release Tablets, an investigational non-dopaminergic treatment for moderate-to-severe primary Restless Legs Syndrome (RLS). The NDA was submitted to the FDA on January 9, 2009.

The letter states that a preclinical finding of pancreatic acinar cell tumors in rats was a concern and that the FDA can’t approve the drug for RLS at this time. The FDA acknowledged that similar findings were known for gabapentin for refractory epilepsy, but concluded that the seriousness and severity of refractory epilepsy justified the potential risks. The companies are assessing the appropriate next steps and will be communicating with FDA.