Impax Laboratories, Inc. v. Aventis Pharmaceuticals, Inc.

Proof of efficacy is not required for a prior art reference to be enabling for purposes of anticipation.

(Fed. Cir. 2006, 05-1313) 

Impax had originally filed an ANDA with the FDA seeking approval to market generic riluzole (6-trifluoromethoxy-2-benzothiazolamine) tablets for the treatment of ALS and prompting a suit for a declaratory judgment that Impax did not infringe, induce infringement of, or contribute to the infringement of Aventis’ U.S. Patent No. 5,527,814 (“the ’814 patent”).   Prior to this appeal, the district court had found that no inequitable conduct and that the ‘814 was not anticipated.

The claimed technology of the ‘814 patent comprises “[a] method for treating a mammal with [ALS], comprising the step of administering to said mammal in recognized need of said treatment an effective amount of [riluzole] or a pharmaceutically acceptable salt thereof.”  On appeal, the CAFC considered the district court’s determination that Impax failed to prove (1) that the ’814 patent is unenforceable due to inequitable conduct and (2) that the ’814 patent is invalid as anticipated.  As the CAFC found that the district court did not clearly err in its materiality and intent findings in relation to inequitable conduct, only the anticipation issue will be discussed here. 

The ‘624 application and the ’940 patent that matured therefrom (also owned by Aventis) were cited as prior art references against the ‘814 patent.  These references are directed to a class of compounds that literally encompass riluzole.  The ‘624 application does not identify riluzole by name, but riluzole is a species of the genus disclosed in ‘624.  The ‘940 patent, on the other hand, explicitly excludes riluzole from the class of claimed compounds. 

The district court had concluded that the ’814 patent was not anticipated by either reference because it did not disclose riluzole as being effective in treating ALS.  Also, the district court explained that the ’624 application, from which the ’940 patent claims priority, contained a disclosure similar to the ’940 patent and that there were no material differences between the two references.  Thus, neither reference was deemed to anticipate.  However, the issue according to the CAFC should be whether the ’940 or ‘624 references were enabling in the sense that they describe the claimed invention sufficiently to enable a person of ordinary skill in the art to carry out the invention?

Prior art is not enabling so as to be anticipating if it does not enable a person of ordinary skill in the art to carry out the invention.  Significantly, anticipation does not require actual performance of suggestions in a disclosure. Rather, anticipation only requires that those suggestions be enabled to one of skill in the art.  Proof of efficacy is not required for a prior art reference to be enabling for purposes of anticipation.

The CAFC also acknowledged the species-genus situation of In re Petering.  When 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.  A described genus does not necessarily anticipate a species within the genus. 

The ‘924 reference included riluzole as a compound and suggested that it may be used to treat ALS, but did not provide evidence that it would be effective.  However, the effectiveness of the prior art is not relevant, and therefore the use of this reason to find that the reference does not anticipate was improper.  On the other hand, the decision that the ‘624 reference does not anticipate, where riluzole is just one of hundreds of compounds included in formula I, was proper because the ‘624 does not enable treatment of ALS with riluzole (a particular species) under the standards discussed above. 

The decision of the district court was therefore vacated-in-part and the case remanded as to the issue of anticipation.

Notably, Judge Rader (in a concurring opinion) would find that when the disclosure leaves “substantial uncertainty” as to enablement, a finding of anticipation should be improper.  As read by Judge Rader, the ‘940 disclosure did not put one of skill in the art in possession of the invention at all. 

JW Note:  For more commentary on Genus-Species anticipation, see my previous post: A Species of the Anticipation Genus.