LONDON (AP) -- A British court has ruled that AstraZeneca's patent on an extended-release version of its blockbuster antidepressant drug Seroquel is invalid, the company said Thursday.
The ruling came in a challenge brought by Accord Healthcare Ltd., Intas Pharmaceuticals Ltd., Hexal AG and Sandoz Ltd., Teva UK Ltd., and Teva Pharmaceutical Industries Ltd.
The U.K. patent on quetiapine, the active ingredient in Seroquel, expires on Friday. AstraZeneca was hoping to preserve its rights on that drug by creating an extended-release version, Seroquel XR, with a formulation patent that was to expire in May 2017.
The court, however, ruled that patent invalid in Britain.
AstraZeneca said it was evaluating its legal options but did not immediately say whether it would seek to appeal.
AstraZeneca, which is trying to fend off generic competition, says this is the first ruling against the company on this matter. It has already won a case in the Netherlands and is dealing with similar actions in Spain and the United States.
Shares in the company were down half a percent at 2,836 pence in London following the announcement.
The Seroquel brand, AstraZeneca's second-best seller behind cholesterol drug Crestor, accounted for 17 percent of the company's sales of $33.6 billion in 2011. Sales of Seroquel XR were $1.49 billion or 4.4 percent of total revenue.
The patent covering the formulation of Seroquel XR expires in 2017 in most European markets, the company said.
AstraZeneca announced on March 13 that it had filed suit against the U.S. Food and Drug Administration, seeking to block the agency from allowing generic competition until Dec. 2.