The U.S. Court of Appeals for the Federal Circuit affirmed a district court’s holding that omission during prosecution of comparative data relating to compounds not at issue in a prior art rejection did not constitute inequitable conduct, but remanded the case for reconsideration of the proper legal standard for enablement of a prior art reference. Impax Laboratories Inc. v. Aventis Pharmaceuticals Inc., Case No. 05-1313 (Fed. Cir., Nov. 20, 2006) (Rader, J.).
Riluzole is the chemical compound 6-trifluoromethoxy-2-benzothiazolamine, which is sold by Aventis under the trade name Rilutek® for treatment of amyotrophic lateral sclerosis (ALS). ALS, also known as Lou Gehrig’s disease, is a disease of the central nervous system that involves progressive degeneration of the nerves that control motor function and carry impulses to muscles. In the 12 months preceding August 2006, domestic sales of Rilutek®, the only FDA-approved treatment for ALS, approached $37 million dollars. Aventis owns U.S. Patent No. 5,527,814 (the ’814 patent), with claims directed to the use of riluzole to treat ALS.
Impax filed an ANDA to market a generic version of Rilutek® and, during the course of the approval process, became aware of Aventis’ ’814 patent). At the time, the ’814 patent was not listed in the Orange Book, and thus Impax filed a declaratory judgment action, seeking a declaration that it had not infringed the patent and asserting that the patent was invalid and unenforceable. Under 35 U.S.C. § 271(e)(2), it is an act of infringement to submit an ANDA for a drug claimed in a patent before the patent’s expiration. Impax asserted that the claims of the ’814 patent were invalid over the prior art and made allegations of inequitable conduct.
Regarding the assertion of inequitable conduct, Impax’s main contention was that, during prosecution of the ’814 patent and its priority application, Aventis presented comparative data related to certain compounds, which were the basis for arguing the distinction of a prior art reference, while withholding from the examiner test results of other compounds not at issue in the rejection. The Court agreed with the district court’s ruling that Aventis’ omission of certain data was insufficient to establish an intent to deceive, as required for inequitable conduct.
Turning to the allegation of invalidity over the prior art, Impax asserted that claims 1 through 5 of the ’814 patent were anticipated by Aventis’ U.S. Patent No. 5,236,940 (the ’940 patent). The district court agreed with Impax that formula I disclosed in the ’940 patent included riluzole. Nevertheless, based on the reasoning that the ’940 patent was not enabling because formula I encompassed such a large number of compounds that a skilled artisan would not have recognized that riluzole was effective in treating ALS, the district court concluded that the ’814 patent was not anticipated. Citing its 2005 Rasmusson v. SmithKline Beecham Corp. decision (IP Update, Vol. 8, No. 7), the Court reiterated that the enablement standard for an anticipatory prior art reference differs from the enablement standard under 35 U.S.C. § 112 and that proof of efficacy is not required for a prior art reference to be sufficiently enabling for the purposes of anticipation. The Court thus remanded the case to the district court to determine whether the ’940 patent is enabling using the proper legal standard.
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