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Herbicide-Resistant Plant Patent Fails to Resist Nonenablement and Noninfringement Challenges

January 13, 2003

Decision icon Decision

Last Month at the Federal Circuit - February 2003

Judges: Michel (author), Newman, and Prost

In Plant Genetic Systems, N.V. v. DeKalb Genetics Corp., No. 02-1011 (Fed. Cir. Jan. 13, 2003), the Federal Circuit affirmed the district court’s ruling that certain claims of Plant Genetic Systems, N.V.’s (“PGS”) U.S. Patent No. 5,561,236 (“the ’236 patent”) were invalid for lack of enablement and that the remaining asserted claims of the ’236 patent were not infringed.

The ’236 patent claims a priority date of March 11, 1987, and is directed to transgenic plant cells, plants, and seeds that contain an herbicide-resistant gene. DeKalb Genetics Corporation (“DeKalb”) makes and sells transgenic corn seeds that contain an herbicide-resistant gene. PGS sued DeKalb for infringement the day the ’236 patent issued.

The ’236 patent describes genetically engineered plant cells that express a gene encoding a protein that prevents herbicides, such as bialaphos or glufosinate, from blocking the activity of glutamine synthetase. As a result, plants containing these genetically modified cells can grow in the presence of these glutamine-synthetase inhibitors, while other surrounding plants or weeds die. Claims 1-5 and 10-11 (“the cell claims”) are directed to cell, tissue, and culture claims. The cell claims depend from claim 1, which is directed to a plant cell comprising a heterologous DNA encoding a protein that inactivates a glutamine-synthetase inhibitor in the plant cell. Claims 8-9 and 12-15 (“the plant and seed claims”) are directed to plants and seeds consisting of the cells of claim 1, where the plant or seed is “susceptible to infection and transformation by Agrobacterium and capable of regeneration thereafter.”

A key issue in this case was the scope of the terms “plant” or “plant cell” in the claims. Flowering plants can be broadly categorized as either monocotyledons (“monocots”) or dicotyledons (“dicots”), based on whether the initial seedling develops one leaf (monocot) or two leaves (dicot). In the ’236 patent, all the working examples involve dicots. DeKalb’s transgenic corn, on the other hand, is a monocot.

The district court concluded that the cell claims were invalid for lack of enablement because it would have required undue experimentation as of
March 11, 1987, to carry out stable gene transformation in monocots. On appeal, PGS argued that the district court’s invalidity decision should be reversed because the district court (1) failed to make any findings regarding the pioneering nature of the claimed invention; (2) improperly shifted the burden of proof by requiring the patentee to establish enablement; (3) failed to consider all relevant evidence; and (4) improperly relied on posteffective filing date work in evaluating enablement. The Federal Circuit considered each of these arguments and found none of them persuasive.

First, the Federal Circuit found no precedent to support PGS’s argument that a “pioneering” patent is entitled to a lower standard of enablement. Accordingly, the district court did not err by not making any findings regarding the “pioneering” status of the ’236 patent.

Next, PGS argued that the district court had improperly shifted the burden of proof to PGS by using In re Goodman, 11 F.3d 1046 (Fed. Cir. 1993) as a starting point for the state of the art in 1985 regarding Agrobacterium-mediated transformation of corn and then looking for evidence between 1985 and 1987 to alter the Goodman conclusion that reliable transformation techniques for monocots did not exist in 1985. The Federal Circuit rejected this argument, finding that the district court did not exclude any evidence that could rebut the findings of Goodman and that the district court’s search for evidence of enablementbetween 1985 and 1987 did not shift the burden to PGS, but rather indicated the strength of the nonenablement evidence.

The Federal Circuit also rejected PGS’s argument that the district court did not consider certain documents cited by PGS, observing that the district court’s failure to cite every piece of evidence in its opinion does not, by itself, establish that the evidence was not considered. Rather, a presumption exists that the fact finder reviewed all the presented evidence unless explicitly expressed otherwise.

Finally, the Federal Circuit found that the district court had properly relied on post-1987 work as evidence of the state of the art in 1987. The Federal Circuit agreed with the district court that the reporting of a first successful monocot transformation after 1987 suggests failure or difficulty in or before 1987.

PGS also appealed the district court’s claim construction for the plant and seed claims and sought reversal of the district court’s noninfringement decision. Based on the specification and prosecution history of the ’236 patent, the district court construed the limitation “susceptible to infection and transformation by Agrobacterium and capable of regeneration” as excluding monocots. In particular, during prosecution of the ’236 patent, the Examiner rejected the plant and seed claims as nonenabled for monocots, including corn. PGS overcame the rejection by adding the limitation at issue. Accordingly, the district court held that DeKalb’s monocot corn products did not infringe the plant and seed claims of the ’236 patent.

On appeal, PGS argued that the district court had ignored the plain meaning of the claim language, which covers any plant, monocot, or dicot. The Federal Circuit, however, disagreed. Relying on the prosecution history alone, it held that the district court did not err in its claim construction. Finally, the Federal Circuit rejected PGS’s argument that the district court had erred in considering extrinsic evidence to construe the plant and seed claims. Here, the district court properly consulted the intrinsic evidence and then considered extrinsic evidence to ensure that its claim interpretation was not inconsistent with the understanding in the relevant technical field.