December 19, 2006 is going to be critical for AstraZeneca as European Patent Office will be hearing an appeal over a European Patent EP0652872 (the ‘872 patent) covering esomeprazole, the active ingredient of blockbuster drug Nexium. Losing the appeal would allow generic players to enter European Nexium market four years early than the expected expire until 2014. Even though AstraZeneca loses appeal, data exclusivity will continue to protect the Nexium from generic competition until at least 2010. At appeal EPO will be deciding that whether the ‘872 patent on Nexium is valid as esomeprazole is enantiomeric form of previous AstraZeneca blockbuster Prilosec, generically known as omeprazole. AstraZeneca expressing its confidence in patent contended that it was not obvious that isolating the isomer would have produced an improved drug. Earlier in November 2003, EPO ruled that the ‘872 patent is valid after been opposed by German drug manufacture Ratiopharm. However, the ruling was later appealed by Ratiopharm. In US, AstraZeneca is already defending Para IV challenges against Ranbaxy (November 2005 in U.S. District Court for the District of New Jersey) and Ivax (March 2006 in the U.S. District Court for the District of New Jersey).