Summary
With respect to the blockbuster antidepressant drug Lexapro®, the US Court of Appeals for the Federal Circuit, CAFC or Fed Cir, affirmed the prior November, 2006 Opinion of the Delaware District Court with respect to Plaintiff Forest Labs (NYSE:FRX) Paragraph (IV) patent infringement litigation against Ivax and Cipla. More specifically, the CAFC (a) affirmed that Reissue Patent 34712 [an Orange Book patent which protects Lexapro®] is valid; (b) affirmed the trial court's injunction order against both Ivax and Cipla; and (c) modified the scope of the injunction to apply only to escitalopram oxalate (the active product ingredient in Lexapro® - the single-isomer). This Fed Cir ruling is a definitive, solid win for Forest Labs; however, it does not mean that other currently marketed optically-pure drugs are all safe from generic manufacturers' assertions of patent invalidity.
Analysis
Paragraph (IV) Abbreviated New Drug Application (ANDA) patent infringement litigation is of high-stakes critical importance to both innovator and generic pharmaceutical manufacturers. On the positive side (from Big Pharma's perspective) this Federal Circuit victory for Forest Labs shows that 2nd generation, single-enantiomer drug products can be successfully asserted against possible generic product launches. On the other hand, for the generic manufacturers seeking early market entry, the assault against the Orange Book innovator patents will continue. The specific facts of this Lexapro® litigation do not imply that other optically-pure branded drug patents will survive the Paragraph (IV) Patent Challenges. The Federal Circuit's Opinion notes the following in reaching its conclusions: (a) a key prior art reference, Smith, is not enabling with respect to anticipation or obvious patent invalidity; (b) a team of chemists at Lundbeck had unsuccessfully tried for 2 years to separate the enantiomers of citalopram (the active product ingredient as a racemic mixture) into the 2 individual stereoisomer; and (c) the intentional use of an optically-pure diol intermediate enantiomer in the chemical synthesis of Lexapro® is yet another factor used in reaching the decision to reject the assertions of patent invalidity by the Defendants Ivax & Cipla.
