The companies said the Food and Drug Administration approved Horizant as a treatment for nerve pain that follows shingles, a viral infection related to chicken pox. Xenoport and GlaxoSmithKline said around 1 million cases of shingles, or herpes zoster, are diagnosed in the U.S. each year and about 10 percent of patients later develop nerve pain. The condition is called postherpetic neuralgia.
Xenoport is based in Santa Clara, Calif., and it said it will receive a $10 million payment from GlaxoSmithKline upon the first commercial sale of Horizant as a treatment for postherpetic neuralgia. The FDA approved Horizant in April 2011 as a treatment for restless legs syndrome, and it is Xenoport's only approved drug.
Side effects of Horizant in clinical trials for postherpetic neuralgia included tiredness and dizziness.
Shares of Xenoport lost 31 cents, or 5.1 percent, to $5.76 in afternoon trading. The stock has advanced 16.5 percent since May 11. Shares of GlaxoSmithKline rose 16 cents to $44.54.
