A potential treatment for restless leg syndrome shows effectiveness in a Phase III clinical trial, GlaxoSmithKline (NYSE: GSK) and its development partner XenoPort reported on Tuesday.

The drug was “generally well tolerated” while showing a “significant difference” between patients receiving it and those receiving a placebo, the companies said.

“This study is an important next step in moving toward the submission of the [new drug application] for XP13512, a potential new treatment for patients with primary RLS,” said Dr. Atul Pande, GSK’s senior vice president for Neurosciences Medicines Development Center.