Impax Labs v. Aventis Pharmaceuticals (Fed. Cir. 2008)
This appeal focuses on the question of when a prior art disclosure is sufficiently enabled.
An Aventis patent covers the use of RILUTEK (riluzole) to treat ALS. Impax filed an ANDA with the FDA (seeking to market a generic version of the drug). In subsequent litigation, Impax also alleged, inter alia, that the listed patent should be held invalid. In particular, Impax argued that an earlier Aventis patent (the '940 patent) anticipates the asserted Aventis patent (the '814 patent) by suggesting a class of compounds may be used to treat ALS. The district court, however found that the '940 patent "does not enable a person of ordinary skill in the art to treat ALS with riluzole and therefore does not anticipate claims 1-5 of the '814 patent."
Burden particularly heavy: A defendant who hopes to use previously considered art to invalidate a patent has a "particularly heavy" burden.
Thus, a party challenging patent validity has the burden to prove its case with clear and convincing evidence. 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 this case, the '940 patent had been considered by the examiner during prosecution of the asserted patent.
Enabled Prior Art: To anticipate, the prior art must be enabling – i.e., it must "enable one of ordinary skill in the art to make the invention without undue experimentation." This enablement standard is different from the applicant's 112 enablement requirement which requires enablement of both making and using the invention. That distinction becomes lost in cases like this, however, where the patent covers a method of treatment. Here, the Federal Circuit appears to require anticipatory prior art to enable practicing the claimed method.
Enablement of prior art is a question of law, but is based on underlying factual findings. In close cases, the important factual finding is the amount of experimentation that would have been necessary. Applying Wands factors, the Federal Circuit agreed that the prior reference was not enabling.
As shown by the trial court, the [prior art] '940 patent's dosage guidelines are broad and general without sufficient direction or guidance to prescribe a treatment regimen. The alleged prior art also contains no working examples. Finally, nothing in the '940 patent would have led one of skill in the art to identify riluzole as a treatment for ALS. In sum, 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.
Burden of Proving Enabled Prior Art: In judging anticipation, courts generally presume that prior art is enabled. That presumption may be overcome by a patentee by providing "persuasive evidence" of nonenablement. At that point, the ultimate burden of proof (with clear and convincing evidence) lies with the accused infringer. In this case, the district court did not explicitly follow this burden shifting framework. On appeal, the Federal Circuit held that articulation of the rule was not necessary. The burden was properly shifted because Aventis presented "sufficient evidence to overcome the presumption of enablement."
Holding: Affirmed. Validity challenge defeated because prior art was not enabled.
- The opinion did not focus on timing: As technology develops more and more prior art references become enabled. Thus, it is important to consider at what point in time the reference must be enabling.
Disclosure: My former colleagues at MBHB represent Aventis in this case. The district court case was ongoing while I was there.