Impax Laboratories, Inc. v. Aventis Pharmaceuticals Inc. (Fed. Cir. 2006)

    By Donald Zuhn --

In an appeal from a District Court judgment holding claims 1-5 of U.S. Patent No. 5,527,814 (the '814 patent) enforceable, valid, and infringed, the Federal Circuit affirmed the District Court's finding of no inequitable conduct, vacated the District Court's finding that claims 1-5 of the '814 patent were not invalid as anticipated, and remanded the case for further proceedings on the issue of anticipation.

Defendant-Appellee Aventis Pharmaceuticals Inc. (Aventis) owns the '814 patent, which relates to methods for treating amyotrophic lateral sclerosis (ALS) using 2-amino-6-(trifluoromethoxy) benzothiazole, commonly referred to as riluzole.  Dr. Erik Louvel, the lone inventor on the '814 patent, had discovered in comparative testing of eight compounds on rat spinal cord cells, that only riluzole produced positive results for all three of the key parameters tested.

Seeking approval to market generic riluzole tablets for the treatment of ALS, Plaintiff-Appellant Impax Laboratories, Inc. (Impax) filed an Abbreviated New Drug Application (ANDA) with the FDA.  Impax became aware of the '814 patent in the course of preparing its ANDA, and thereafter filed a declaratory judgment action in the District of Delaware.  In its suit, Impax sought a declaration that it had not infringed the '814 patent by filing its ANDA, and that its proposed manufacture and sale of riluzole would not infringe the '814 patent.  In addition, Impax asserted that the '814 patent was invalid over the prior art, as well as unenforceable due to inequitable conduct.

Following a bench trial, the District Court determined that Impax's manufacture and sale of riluzole would infringe the '814 patent, and that Impax had not established that the '814 patent was unenforceable due to inequitable conduct or that claims 1-5 were invalid as anticipated by the prior art.  Impax appealed the District Court's determination that it failed to prove that the '814 patent was unenforceable due to inequitable conduct or invalid as anticipated.

On the issue of enforceability, the Federal Circuit found that the District Court had not erred in determining that some of Dr. Louvel's comparative testing results were not material.  Before the District Court, and again on appeal, Impax argued that Dr. Louvel had failed to disclose the testing results for all of the eight compounds he tested, and therefore, had withheld material information from the Patent Office.  In particular, Impax contended that Dr. Louvel had failed to disclose the results for a compound that yielded positive results for two of the three key parameters tested.  Aventis countered that the withheld data was not material because only riluzole had yielded positive results for all three parameters tested.  The Federal Circuit concluded that "the district court correctly recognized that the comparative test data did not produce results that indicated that any of [the compounds for which data was withheld] was effective in treating ALS," and therefore, found "no error in the ruling of the district court that the [withheld test results] were not material under either Rule 56 standard."  The Federal Circuit also concluded that the District Court had not erred in finding no intent to deceive, and affirmed the District Court's ruling that the '814 patent was not unenforceable due to inequitable conduct.

On the issue of validity, Impax asserted before the District Court that Aventis' U.S. Patent No. 5,236,940 (the '940 patent) and Aventis' French Application No. 2,640,624 (the '624 application), from which the '940 patent claims priority, anticipate claims 1-5 of the '814 patent.  In particular, Impax contended that the '940 patent and '624 application disclose a class of compounds that includes riluzole, and suggest that this class of compounds may be used to treat ALS.  Aventis countered that the prior art cited by Impax was not enabling because it did not provide specific instruction for using riluzole and, in fact, taught away from using riluzole.

Citing Rasmusson v. SmithKline Beecham Corp., 413 F.3d 1318 (Fed. Cir. 2005), as standing for the proposition that "proof of efficacy is not required for a prior art reference to be enabling," the Federal Circuit determined that the District Court had focused on whether the prior art disclosed that riluzole was effective for treating ALS rather than on whether the prior art enabled the use of riluzole for treating ALS.  In Rasmusson, the Federal Circuit had reversed a decision by the Board of Patent Appeals and Interferences that a prior art reference disclosing a method of treating prostrate cancer using finasteride was not enabling, and therefore, not anticipatory, because the reference failed to demonstrate that finasteride was effective in treating prostrate cancer.  The Federal Circuit determined that the instant case was similar to Rasmusson, since "the district court stopped its analysis after concluding that the [prior art] did not disclose the compounds of formula I [of the '814 patent] were effective in treating ALS," and failed to "determine whether the [prior art] enables a person of ordinary skill in the art to treat ALS with riluzole."

Finding that the District Court had stopped short of completing a proper enablement analysis, the Federal Circuit looked to the allegedly anticipatory references to determine whether either was enabling.  With respect to the '624 application, the Federal Circuit noted that "[w]hen a reference discloses a class of compounds, i.e., a genus, a person of ordinary skill in the art should be able to 'at once envisage each member of th[e] . . . class' for the individual compounds, i.e., species, to be enabled" (citing In re Petering, 301 F.2d 676, 681 (C.C.P.A. 1962).  The Federal Circuit concluded that because riluzole is just one of hundreds of compounds encompassed by the class of compounds disclosed in that application, and because the '624 application does not identify riluzole by name, the '624 application did not enable the use of the species riluzole for treating ALS.  Thus, the Federal Circuit affirmed the District Court's finding that the '264 application does not anticipate the '814 patent.

The Federal Circuit, however, reached a different conclusion with respect to the '940 patent.  Noting that the '940 patent, unlike the '264 application, identifies riluzole by name (by explicitly exempting riluzole from formula I), the Federal Circuit concluded that this reference could not be similarly dismissed as nonenabling.  Instead, the Federal Circuit vacated the District Court's finding with respect to the '940 patent, and remanded the case to allow the District Court to reach its own legal conclusion as to whether this reference is enabled.

Finally, in a separate opinion in which he joined the majority on all issues except the anticipation determination, Judge Rader concluded that "[w]hile the trial court referred to effectiveness, its findings go beyond that narrow ruling and suffice to uphold its judgment," and further, that "the majority opinion provides even more evidence that the '940 patent is not an enabling reference for purposes of anticipating the '814 patent."

Impax Laboratories, Inc. v. Aventis Pharmaceuticals Inc. (Fed. Cir. 2006)
Panel: Circuit Judges Rader, Schall, and Prost
Opinion by Circuit Judge Schall; concurring-in-part opinion by Circuit Judge Rader

Thanks to MBHB attorney Brad Crawford for providing the structure of riluzole.

Additional Disclaimer:  MBHB represented Aventis in the above appeal.  To the extent that this case summary contains any opinions, the opinions would be of Dr. Zuhn and not Aventis or MBHB.