GlaxoSmithKline/XenoPort get negative response from USA's FDA for Horizant; Merck & Co won't file for vicriviroc now

UK drugs giant GlaxoSmithKline and partner XenoPort have received a negative response from the US Food and Drug Administration regarding their marketing application for their restless legs syndrome (RLS) drug.

In a Complete Response letter from the FDA the New Drug Application (NDA) for Horizant (gabapentin enacarbil; formerly known as XP13512) extended-release tablets, an investigational non-dopaminergic treatment for moderate-to-severe primary RLS, the agency indicated that a preclinical finding of pancreatic acinar cell tumors in rats was of sufficient concern to preclude approval of Horizant for RLS at this time. The FDA acknowledged that similar findings were known for gabapentin at the time of its approval 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. The NDA was submitted to the FDA on January 9, 2009.

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