A US court has denied AstraZeneca’s request for a preliminary injunction against FDA. AstraZeneca filed a lawsuit against the agency at the beginning of March 2012 with regards to the antipsychotic medicines Seroquel (quetiapine fumarate) and Seroquel XR.

The injunction had sought to prevent FDA from granting final marketing approval to a generic version of quetiapine until December 2012. Prior to the injunction, AstraZeneca had filed Citizen Petitions with FDA last year concerning labeling issues for generic drugs. Seroquel is required to carry warnings about hyperglycemia and suicidal thoughts, but the same labeling may not be needed for generic versions of the drug. AstraZeneca’s Citizen Petitions attested that generic quetiapine should require the same warning labels and that FDA should withhold approving any generic form of the medicine that does not include such labeling.

FDA denied the petition earlier this month.

The US is not the only territory where AstraZeneca faces loss of market exclusivity for Seroquel. Last week, a court in the UK ruled that the formulation patent protecting Seroqeul XR was invalid. The patent had been challenged by several generic drug manufacturers, including Accord Healthcare, Intas Pharmaceuticals, Hexal, Sandoz, Teva UK, and Teva Pharmaceutical Industries. Teva UK launched a generic version of Seroquel in the UK on Mar. 27, 2012.

According to a blog from Pharmaceutical Executive, the core patent for Seroquel IR expired in September last year and pediatric patent is due to expire soon. Seroquel XR reportedly still has protection until 2017, but according to a press statement, AstraZeneca is engaged in numerous proceedings related to the drug and its related patents and regulatory exclusivity.