UPDATE 1-Glaxo's Requip drug suffers U.S. setback

(Updates with further details, wraps Requip XL and CR stories)

LONDON Dec 10 (Reuters) - Plans by GlaxoSmithKline Plc (GSK.L) to market two long-lasting versions of its Requip medicine in the United States suffered a double blow on Monday.

Europe's biggest drugmaker said the Food and Drug Administration (FDA) had delayed approval of its Requip XL extended-release, or 24-hour, form of the medicine for Parkinson's disease.

At the same time, Glaxo said it had decided not to pursue an application to market Requip CR -- a controlled-release, or 14-hour, formulation of the drug -- for treatment of restless leg syndrome.

Glaxo has just received a so-called approvable letter from the FDA for Requip XL, indicating that conditions must be satisfied prior to obtaining final U.S. marketing approval.

A Glaxo spokeswoman said the company remained hopeful that Requip XL would still get to market before too long, since the FDA had not requested additional clinical data.

Glaxo is expecting a Class 1 review, meaning the regulator should come back with a final decision over issues such as labelling within two months.

In the case of Requip CR for restless leg syndrome, however, where an approvable letter was issued in August, Glaxo has decided that it is not possible to resolve the issues.

"Our intention is to withdraw the NDA (new drug application)," the spokeswoman said.

These decisions do not affect the immediate-release formulation of Requip, which is approved for both conditions.

Requip is a relatively small but fast-growing product for Glaxo. Worldwide sales were 251 million pounds ($511.9 million) in the first nine months of 2007, up 40 percent on a year earlier, of which 174 million was generated in the U.S. market. (Reporting by Ben Hirschler; Editing by Clara Marques, Paul Bolding)