Impax Laboratories has suffered a setback after regulators in the USA turned down its long-acting Parkinson's disease treatment Rytary.

The Food and Drug Administration has issued a complete response letter for Rytary, an extended-release capsule of carbidopa and levodopa for PD. The agency told Impax it requires "a satisfactory re-inspection" of the company’s Hayward facility as a result of a warning letter issued in May 2011.

The facility was used in the development of Rytary "and supportive manufacturing and distribution activities". Impax noted, however, that during the assessment of the New Drug Application, the company withdrew the Hayward plant as an alternative site of commercial production at launch.

Larry Hsu, Impax chief executive, said that "we will work with the FDA on the appropriate next steps for the Rytary application". He added that "we remain committed to resolving the warning letter and bringing this new treatment option to patients who are suffering from Parkinson’s disease".

Rytary was licensed to GlaxoSmithKline in December 2010 to market the treatment for countries outside the USA and Taiwan.