The U.S. Court of Appeals for the Federal Circuit recently affirmed a district court's determination that a patent did not qualify as an enabling prior art reference and, therefore, was insufficient to support an anticipation rejection. Impax Laboratories, Inc. v. Aventis Pharmaceuticals Inc., Case No. 07-1513 (Fed. Cir. Oct. 3, 2008)(Rader J.)
The patent-in-suit, which is owned by Aventis Pharmaceuticals Inc., relates to the use of riluzole to treat amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease). Aventis markets riluzole under the trade name RILUTEK.
Impax Laboratories, Inc. filed an Abbreviated New Drug Application (ANDA) with the FDA seeking approval to market generic riluzole tablets. One year later, Impax sued Aventis for a declaratory judgment that Impax did not infringe, induce infringement of or contribute to the infringement of the Aventis patent. In its suit, Impax alleged that the patent was invalid as anticipated and unenforceable.
After a bench trial, the district court determined that Impax did not prove that the patent was unenforceable due to inequitable conduct or that the asserted claims of the patent were anticipated by the prior art.
Impax appealed that determination to the Federal Circuit, which affirmed-in-part, vacated-in-part and remanded to the district court. On remand, the trial court was advised to consider whether the prior art patent enables a person of ordinary skill in the art to treat ALS with riluzole and thus qualified as enabling prior art.
On remand, the district court found that because the prior art patent disclosed a formula encompassing hundreds or thousands of compounds for the treatment of several diseases, excessive experimentation would have been required to use riluzole to treat ALS. In addition, the district court determined that nothing in the prior art patent directed one skilled in the to recognize that riluzole could be used to treat ALS, rejecting Impax's assertion that "the mere mention of riluzole is sufficient to put one skilled in the art in the possession of the claimed invention." Pursuant to Federal Circuit precedent, once an infringer has met the burden of showing a prior art reference anticipatory, such anticipating prior art is presumed enabling, shifting the burden to the patent holder, who "may overcome that presumption with persuasive evidence showing that the prior art patent does not enable the claimed invention."
In the second appeal, the patentee met that burden with persuasive evidence that the prior art patent did not enable the claimed invention, stating that each component of the claimed invention would require undue experimentation based on the teachings of the prior art patent. Because the district court did not err in finding the prior art patent to be non-enabling, the Federal Circuit also found that the district court had correctly determined that the prior art patent did not anticipate the asserted claims of the patent-in-suit.
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