GlaxoSmithKline and XenoPort Inc. announced the withdrawal of an application for approval by the Food and Drug Administration of Solzira, a drug for restless legs syndrome. The decision delays $23 million in milestone payments to XenoPort from GSK and Astellas Pharma.

The companies asked for FDA approval in September.

The companies said the withdrawal of the application "does not relate to the content of the filing." However, Glaxo said it plans to resubmit the application.

The FDA requested that data in a single study be reformatted. Solzira is aimed at treating restless legs syndrome, a neurological disorder characterized by sensations in the legs and an urge to move them for relief.

Japan's Astellas Pharma, eventually, will be in charge of marketing Solzira in Japan and five other countries of Asia.