The UK-based drug major AstraZeneca has filed one more patent lawsuit against Gujarat-based Torrent Pharmaceuticals and its US subsidiary, for alleged move to manufacture and sell the generic version of its extended release anti-psychotic drug, Seroquel XR prior to the expiry of its patent.

The company has filed a complaint against Torrent Pharma in the District Court of New Jersey, US, following the a para IV filing of the latter to produce and market the quetiapine fumarate extended release drug, the generic form of AstraZeneca's Seroquel XR, used to treat schizophrenia and bipolar disorder, according to reports available.

The complaint alleges that by for the Para IV certificate Torrent has infringed its US patent with patent numbers 4,879,288 (the `288 patent) for novel dibenzothiazepine antipsychotic, issued on November 7, 1989 and 5,948,437 (the `437 patent) for pharmaceutical compositions using thiazepine, issued on September 7, 1999. The ‘288 patent is expected to expire on September 26, 2011 while the ’437 patent is dated to expire on May 28, 2017.

According to the company reports following the announcement of the first quarter results for 2010, Seroquel XR now accounts for 13 percent of total prescriptions for the franchise in US and has recorded 210 per cent increase in prescriptions as against the 1.4 per cent total prescriptions for the Seroquel franchise in the nation. In the US, Seroquel sales went up 14 per cent to reach $913 million. The strong growth for the extended release in the global market is mostly from either new starts or switches from other therapy, and not switches from the immediate release Seroquel, added the report.

Sales of the extended release form in the rest of the world has nearly doubled and accounts for 29 per cent of franchise sales outside the US and the total Seroquel franchise sales in emerging markets reported a growth of 18 per cent. AstraZeneca has also sued Osmotica Pharmaceutical Corporation, based in Argentina and has principal operations in US, for infringement of the same patents, as per the report.

Torrent Pharma is also a manufacturing partner for AstraZeneca, since the UK based drug major has announced its first branded generic supply deal with Torrent, in March, 2010, for supply of 18 generic drugs in nine countries in the initial stage as part of its effort to increase presence in the emerging markets.