After the district court held that an earlier patent (Pat. No. 5,236,940) did not qualify as an enabling prior art reference and didn’t anticipate claims of U.S. Pat. No. 5,527,814, relating to the use of riluzole to treat amyotrophic lateral sclerosis (ALS or Lou Gehrig’s disease), the U.S. Court of Appeals for the Federal Circuit agreed that 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 the ’814 patent.  Impax Labs v. Aventis Pharma (07-1513)

Aventis Pharmaceuticals owns the ’814 patent and sells riluzole under the trade name RILUTEK.  After Impax Labs filed for an Abbreviated New Drug Application (ANDA) with the Food and Drug Administration (FDA) seeking approval to market generic riluzole tablets, Impax sued Aventis for a declaratory judgment that Impax did not infringe the ’814 patent.

The trial court examined the asserted prior art, the ’940 patent, for evidence that it enables the use of riluzole to treat ALS and thus qualifies as enabling prior art and determined 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.

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. 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).

The district court found that:

  1. formula I encompasses a particularly large number of compounds;
  2. riluzole was not meaningfully discussed in the treatment of medical conditions associated with the effects of glutamate;
  3. the language of the ’940 patent itself created “substantial uncertainty” regarding use of glutamate inhibiting compounds in the treatment of ALS; and
  4. the language in the ’940 patent discussing conditions implicating glutamate is speculative, at best.  In other words, the district court found that the disclosure of the ’940 patent did not put one of ordinary skill in the possession of the invention.

The CAFC then 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.

The district court found that excessive experimentation would have been necessary to practice the invention and rejected the notion that “the mere mention of riluzole is sufficient to put one skilled in the art in the possession of the claimed invention.”

The CAFC agreed:

As shown by the trial court, the ‘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.

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.

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