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Prior Art Patent’s Dosage Guidelines Failed to Provide Sufficient Guidance to Prescribe a Treatment Regimen and Did Not Enable Claimed Invention so as to Anticipate Patent-in-Suit

October 03, 2008

Decision icon Decision

Last Month at the Federal Circuit - November 2008

Judges: Rader (author), Schall, Zobel (District Judge sitting by designation)

[Appealed from: D. Del., Judge Farnan]

In Impax Laboratories, Inc. v. Aventis Pharmaceuticals Inc., No. 07-1513 (Fed. Cir. Oct. 3, 2008), the Federal Circuit held that the district court correctly determined that U.S. Patent No. 5,236,940 (“the ’940 patent”) was not an enabling prior art reference and therefore did not anticipate U.S. Patent No. 5,527,814 (“the ’814 patent”) owned by Aventis Pharmaceuticals Inc. (“Aventis”).

The ’814 patent relates to the use of riluzole to treat Lou Gehrig’s disease or amyotrophic lateral sclerosis (“ALS”). Impax Laboratories, Inc. (“Impax”) filed an ANDA seeking FDA approval to market generic riluzole. Impax then sued Aventis seeking a DJ of noninfringement, invalidity, and unenforceability. With respect to invalidity, Impax alleged that the ’940 patent, which disclosed pharmaceutical compositions useful for the treatment of medical conditions associated with the effects of glutamate, enabled the use of riluzole to treat ALS and therefore qualified as enabling prior art.

The district court found that the disclosure of the ’940 patent did not put one of ordinary skill in possession of the invention. As such, the district court determined that Impax did not prove that the ’814 patent was anticipated by the ’940 patent. Impax Labs., Inc. v. Aventis Pharms. Inc., 333 F. Supp. 2d 265 (D. Del. 2004).

On appeal by Impax, the Federal Circuit remanded for a specific determination on whether the ’940 patent enabled a person of ordinary skill in the art to treat ALS with riluzole without regard to the efficacy of such treatment. Impax Labs., Inc. v. Aventis Pharms. Inc., 468 F.3d 1366, 1384 (Fed. Cir. 2006). On remand, the district court concluded that nothing in the ’940 patent would direct a skilled artisan to recognize that riluzole could be used to treat ALS, rejecting that “the mere mention of riluzole [was] sufficient to put one skilled in the art in the possession of the claimed invention.” Impax Labs., Inc. v. Aventis Pharms. Inc., 496 F. Supp. 2d 428, 432 (D. Del. 2007). In addition, the trial court noted that the dosage guidelines in the disclosure were broad and not specific to any of the hundreds of formulas of the claimed invention or to any of the listed diseases. Finally, the district court also noted the absence of working examples. In view of these findings, the district court found that a skilled artisan would have needed extensive experimentation to link riluzole with the treatment of ALS such that the ’940 patent did not enable the claims and thus did not anticipate the ’814 patent.

On appeal, the Federal Circuit noted that the ’940 patent’s dosage guidelines were broad and general without sufficient direction or guidance to prescribe a treatment regimen. The Court also noted the absence of working examples or anything in the ’940 patent that would have led a skilled artisan to identify riluzole as a treatment for ALS. Thus, the Court stated that “each component of the claimed invention—identifying riluzole as a treatment for ALS and devising dosage parameters—would require undue experimentation based on the teachings of the ’940 patent.” Slip op. at 5.

In addition, the Court addressed Impax’s argument that the district court’s silence on remand regarding the initial presumption of enablement to both claimed and unclaimed material in the ’940 patent was reversible legal error. The Court stated that the district court correctly placed the burden of proving nonenablement of the ’940 patent on the patentee. The Court stated that the district court did not need to specifically articulate its correct burden-shifting framework. As such, the Court affirmed the district court’s holding that the ’940 patent was not an enabling prior art reference and did not anticipate the claims of the ’814 patent.