AstraZeneca has been boosted by the news that the validity of its patent on  the blockbuster antipsychotic Seroquel XR has been upheld in the USA.

The US Court of Appeals for the Federal Circuit has upheld a lower court ruling made in March 2012 that had found the formulation patent protecting Seroquel XR (quetiapine fumarate) extended-release tablets in the USA to be valid. That decision supported AstraZeneca's view that the formulation patent, which expires in November 2017, had been infringed by Anchen Pharmaceuticals, Osmotica Pharmaceutical Corp, Torrent and Mylan.

The continued success of Seroquel XR is vital to the fortunes of the Anglo-Swedish drugmaker at a time when patent expiries and tough market conditions continue to hurt its profits. Sales of the drug came in at around $1.5 billion last year, a rise of about 4%.

AstraZeneca said it is "pleased with the appellate court’s decision, which again demonstrates the strength of the intellectual property protecting Seroquel XR". However the stance taken by US judges has not been reciprocated in Europe; courts in the UK and Germany have recently decreed that the patent on the drug is invalid.