Aventis Pharma S.A. v. Amphastar Pharmaceuticals, Inc.

Aventis (plaintiff) held patents covering a blood-thinning drug marketed as Lovenox. During prosecution, Aventis's expert submitted declarations comparing the drug's half-life to a prior-art compound, but omitted the prior-art compound's dosage, which later proved highly material to the comparison. After the patent issued, Aventis sued Amphastar (defendant) for infringement when Amphastar sought to sell a generic version. The district court initially found inequitable conduct and held the patent unenforceable; on appeal, the Federal Circuit sent the case back for a finding on intent to deceive. On remand, the district court found Aventis's expert intended to deceive the examiner, and Aventis appealed again.