US Court of Appeals for the Federal Circuit has issued a decision reversing a lower court ruling that upholds the Pfizer’s U.S. Patent No. 4,879,303 (the ‘303 patent) covering amlodipine besylate, the active ingredient of Norvasc worth US $ 4.86 billion in Sales in 2006. The ruling came on an appeal made by Apotex, which lost a patent challenge in January 2006 when the US District Court for the Northern District of Illinois had ruled the ‘303 patent valid and enforceable. Following CAFC decision, Mylan, which earlier lost patent challenge over Norvasc last month, has launched its generic Norvasc in the US. Mylan claims to have first-to-file status for Norvasc and likely to enjoy 180-days of marketing exclusivity. It is expected that Mylan earlier introduction of generic Norvasc may cost Pfizer US $ 1 billion in sales. CAFC found claims 1-3 of the ‘303 patent invalid for obviousness contradicting Pfizer’s assertion that (1) amlodipine besylate exhibits unexpectedly superior results would be enough to overcome the objection of obviousness over the prior art, and (2) finding of amlodipine besylate corresponds to ‘discovery’ as it was obtained through the use of trial and error procedures. Read CAFC decision Pfizer, Inc. v. Apotex, Inc.