Impax Laboratories v. Aventis Pharmaceuticals (CAFC 2007-1513)

An issued patent enjoys a presumption of validity. Impax Labs., 468 F.3d at 1378. Thus, a party challenging patent validity has the burden to prove its case with clear and convincing evidence. Id. When the examiner considered the asserted prior art and basis for the validity challenge during patent prosecution, that burden becomes particularly heavy. See Hewlett-Packard Co. v. Bausch & Lomb Inc., 909 F.2d 1464, 1467 (Fed. Cir. 1990).

In order to anticipate a claimed invention, a prior art reference must enable one of ordinary skill in the art to make the invention without undue experimentation. Finisar Corp. v. DirecTV Group, Inc., 523 F.3d 1323, 1336 (Fed. Cir. 2008) (citing In re Omeprazole Patent Litig., 483 F.3d 1364, 1379 (Fed. Cir. 2007)). In other words, the prior art must enable the claimed invention. Minn. Mining & Mfg. Co. v. Chemque, Inc. (3M), 303 F.3d 1294, 1301 (Fed. Cir. 2002). The "undue experimentation" component of that equation examines (1) the quantity of experimentation; (2) the amount of direction or guidance present; (3) the presence or absence of working examples; (4) the nature of the invention; (5) the state of the prior art; (6) the relative skill of those in the art; (7) the predictability or unpredictability of the art; and (8) the breadth of the claims. In re Wands, 858 F.2d 731, 737 (Fed. Cir. 1988).

Whether a prior art reference is enabling presents a question of law based upon underlying factual findings. 3M, 303 F.3d at 1301. This court reviews the ultimate question of enablement without deference while reviewing the underlying factual inquiries for clear error. Elan Pharms., Inc. v. Mayo Found. Med. Educ. & Research, 346 F.3d 1051, 1054 (Fed. Cir. 2003). Under the clear error standard, the district court's findings will not be overturned in the absence of a definite and firm conviction that a mistake has been made. Impax Labs., 468 F.3d at 1375.

The district court found the prior art Impax liked insufficient. On first appeal, the CAFC wanted a better sense of enablement. Again, the district court found the prior art insufficient.

[T]he district court found that the disclosure of the '940 patent did not put one of ordinary skill in the possession of the invention. See id. at 1384-85 (Rader, J., concurring-in-part). This court remanded for a specific determination on whether the '940 patent enables a person of ordinary skill in the art to treat ALS with riluzole without regard to the efficacy of such treatment. Id. at 1384.

On remand, the district court made additional factual findings on that specific question. The district court found that excessive experimentation would have been necessary to practice the invention.

The appeals court found no error with that. Barbering split hairs, the CAFC described how, once an infringer has met the burden to showing a prior art reference anticipatory, such anticipating prior art is presumed enabling, shifting the burden to the patent holder, who may overcome "may overcome that presumption with persuasive evidence showing that the prior art patent does not enable the claimed invention."

As this court explained during the first appeal, when an accused infringer asserts that a prior art patent anticipates specific patent claims, the infringer enjoys a presumption that the anticipating disclosure also enables the claimed invention. Impax Labs., 468 F.3d at 1382. However, the patentee may overcome that presumption with persuasive evidence showing that the prior art patent does not enable the claimed invention. Id. On appeal, Impax argues that the district court's silence regarding the initial presumption of enablement to both claimed and unclaimed material is reversible legal error. For this proposition, Impax cites this court's opinion in Amgen Inc. v. Hoechst Marion Roussel, Inc., 314 F.3d 1313, 1355-56 (Fed. Cir. 2003).

To the contrary, in Amgen, the district court placed an affirmative burden of proving the prior art reference's enablement of the claimed invention on the alleged infringer. Id. This court assigned error to that shifting of the burden. In this case, the district court correctly placed the burden of proving non-enablement on the patentee. The patentee then met that burden with persuasive evidence that the '940 patent does not enable claims 1-5 of the '814 patent. The district court did not need to specifically articulate its correct burden-shifting framework. In this case, as the district court found, the record shows sufficient evidence to overcome the presumption of enablement.

Affirmed.