XenoPort rockets up after FDA approves Horizant for RLS

After surviving a turbulent year marked by a painful restructuring and a setback in the clinical development of one of its key programs, XenoPort ($XNPT) has won approval for Horizant, a new therapy for restless leg syndrome. The news electrified doubtful investors, who swiftly bid up XenoPort's share price by 57 percent.

Horizant (gabapentin enacarbil) was adapted from the epilepsy drug gabapentin. Fourteen months ago regulators handed XenoPort and its partner GlaxoSmithKline a complete response letter raising concerns about tumors seen in rats during early research work. But XenoPort stuck with the program, answered the queries and now has its first approval in hand.

"We think it's a great example of a company able to work with the FDA to clear up misconceptions, suggesting the agency indeed can still work rationally with biotech companies," RBC Capital Market analyst Michael Yee told Bloomberg. He added that the company stands to earn $100 million a year from U.S. sales of the drug.

GlaxoSmithKline signed up as a collaborator more than four years ago, offering a $75 million milestone and $565 million in development and sales milestones in exchange for marketing rights.

In its deal with GSK XenoPort held on to co-promotion rights for the drug in the U.S., but CEO Ron Barrett tells FierceBiotech this morning that there are no plans to field a sales force of its own anytime soon. For now GSK will handle marketing with some 500 reps in the field. XenoPort has three years to start its own marketing operation, he adds, giving the developer time to push ahead with other programs it has in the neurology arena and raising the possibility of eventually having a portfolio of several drugs to sell in the U.S. And in the meantime there are new Horizant approvals to seek in Europe as well as Japan, where Astellas holds the marketing rights to the drug.

XenoPort is preparing a Phase III study for arbaclofen placarbil (AP) as a treatment for spasticity in MS patients. And Barrett says XenoPort has reached agreement with the FDA that the project is "potentially fileable with a single successful study." There's also a Phase II study for a Parkinson's program that should deliver data later in the year.

Now that XenoPort has finally gained an FDA approval for a drug that was originally filed back in 2008, Barrett offers some simple advice to other biotechs: The more communication a developer can have with the FDA about a drug program, the better. That "can be very helpful in highlighting issues they may have concerns about," says Barrett, who was blindsided late in the approval game by the FDA's concern about the tumor signs seen in rats early on.

- see the Xenoport release
- read the Bloomberg story