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 ack...