Anglo-Swedish drug giant AstraZeneca has filed a sustained-release, once-a-day version of its popular schizophrenia drug Seroquel in the USA, under a strategy aiming to secure future sales of its second best-selling product, which could soon face generic competition.

Seroquel (quetiapine) is one of the company’s key growth drivers, with sales leaping 35% last year to nearly $2.8 billion. But the drug, which has patent protection until 2011, could soon have a battle for market share on its hands, if Israeli drugmaker Teva Pharmaceutical Industries is successful in its attempt to launch a generic version.

Teva challenged Seroquel’s patent shield last Autumn, causing AstraZeneca to promptly file a patent infringement lawsuit against Teva, thereby putting the launch date for the copycat version back to at least 2008 – unless of course a court judgement goes against AstraZeneca in the meantime.

The sustained release form of Seroquel has patent protection out to 2017, and a similar filing to European regulators is planned for towards the end of this year.