Will Horizant's new use soothe tempers at XenoPort, GSK?

Horizant can move out of the restless-legs corral. The GlaxoSmithKline-XenoPort drug won FDA approval to treat post-shingles nerve pain, a use that adds about 100,000 patients per year to its marketing pool. Whether the approval will mend fences between the two companies is another question.

Earlier this year, XenoPort ($XNPT) accused Glaxo ($GSK) of lackadaisical Horizant marketing and gave notice that it would terminate their partnership. GSK fired back with a lawsuit, asking a federal court to affirm that it had lived up to its obligations.

The numbers on Horizant show why XenoPort is less than pleased: According to XenoPort's first-quarter Securities and Exchange Commission filing, Glaxo recorded net sales of just $1.3 million for the period. (Glaxo's earnings release didn't break out Horizant sales.) But Glaxo has sunk $120 million into the deal, so it has plenty of motivation to boost the drug's sales.

Horizant's new indication is based on a 12-week key study, plus two adjunct studies, in 574 patients. XenoPort gets a $10 million milestone payment as soon as Glaxo makes its first sale under the new use.

- read the release from GSK and XenoPort