Horizant receives complete response
XenoPort Inc. (NASDAQ:XNPT) fell $12.93 (66%) to $6.67 on Thursday after FDA issued a complete response letter for an NDA for Horizant gabapentin enacarbil ( XP13512, GSK1838262) extended-release tablets to treat moderate to severe primary restless legs syndrome (RLS). XenoPort and partner GlaxoSmithKline plc (LSE:GSK; NYSE:GSK) said FDA 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." On a conference call, XenoPort said this is the first time FDA has raised concerns about preclinical tumors. The partners also plan to delay future development of the compound for neuropathic pain, for which it is in Phase II testing, until they can address FDA's concerns. Horizant is a transported prodrug of gabapentin.
The companies said FDA noted that similar preclinical findings were identified for gabapentin at the time of its approval for refractory epilepsy, but the agency concluded that the seriousness and severity of refractory epilepsy justified the potential risk. ...