XenoPort Rises After Winning U.S. Approval for First Drug

XenoPort Inc. had its biggest gain in Nasdaq trading after U.S. regulators approved its first product following more than a year of delays.

The Santa Clara, California-based company rose $3.58, or 56 percent, to $9.96 at 4 p.m. New York time in Nasdaq Stock Market composite trading, the largest percentage increase since the shares were listed in June 2005.

XenoPort and partner GlaxoSmithKline Plc said late yesterday that the Food and Drug Administration cleared their Horizant medicine as a treatment for moderate-to-severe restless legs syndrome. The FDA asked in February 2010 for more information about tumors in rats that were seen in early drug studies. The delay led XenoPort to fire half its employees.

“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,” said Michael Yee, an analyst with RBC Capital Markets in San Francisco, in an e-mail.

Horizant may bring in at least $100 million a year in U.S. sales, Yee said. The drug was developed by XenoPort and licensed to London-based Glaxo. It will compete with Glaxo’s Requip and closely held Boehringer Ingelheim GmbH’s Mirapex.

Millions of Patients

People with restless legs syndrome have uncontrollable urges to move their legs to relieve uncomfortable sensations, according to the National Institute of Neurological Disorders and Stroke. The condition affects 2 percent to 3 percent of the U.S. population, according to XenoPort.

In two studies of more than 400 patients, about 75 percent of those taking Horizant for 12 weeks said their symptoms were much or very much improved, compared with about 45 percent of those taking placebos.

“This significant milestone represents the culmination of XenoPort’s efforts,” said Ronald W. Barrett, XenoPort’s chief executive officer. “XenoPort is honored to have contributed to the efforts to find new treatments for restless legs syndrome.”

Horizant is a modified-release form of Neurontin, a Pfizer Inc. drug for epilepsy that is now sold as a generic. Astellas Pharma Inc., of Tokyo, has licensed rights to the product in Japan.