FDA spurns XenoPort's Horizant app

In a setback, the FDA has rejected an application from XenoPort and GlaxoSmithKline to approve the use of Horizant for restless leg syndrome. Regulators pinpointed the potential link of the drug to cancer found in rats during animal studies and made it crystal clear that they were particularly sensitive to risks associated with a drug intended to treat a condition that isn't life threatening.

According to the agency's complete response letter, the presence of pancreatic acinar cell tumors in rats during the drug's preclinical review proved too great a stumbling block to permit approval. And now both companies say they plan to ponder the FDA's response before deciding what they should do next.

The drug is an extended-release form of gabapentin, an epilepsy therapy. The FDA also noted that it had earlier decided to overlook the cancer risk for gabapentin due to the seriousness of epilepsy.

Analysts, however, sense that any possible path forward for Horizant would likely involve some serious new R&D work. "The FDA's response must raise questions over the future for this product, without further significant work being carried out to clarify the risk in humans," note analysts at Jefferies.

- here's the press release
- here's the story from Reuters