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Prior Invention Leaves Insecticidal Gene Patent Invalid

March 12, 2001

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Last Month at the Federal Circuit - April 2001

Judges: Clevenger (author), Bryson, and Linn

In Mycogen Plant Science, Inc. v. Monsanto Co., No. 00-1001 (Fed. Cir. Mar. 12, 2001), the Federal Circuit affirmed a district court verdict of noninfringement based on patent invalidity due to prior invention under 35 U.S.C. § 102(g).

Mycogen Plant Science, Inc. and Agrigenetics, Inc. (collectively “Mycogen”) sued Monsanto Company, DeKalb Genetics Corporation, and Delta and Pine Land Company (collectively “Monsanto”) for infringement of Mycogen’s U.S. Patent Nos. 5,567,600 (“the ‘600 patent”) and 5,637,862 (“the ‘862 patent”). A jury found no infringement and invalidity based on Monsanto’s prior invention.

Arising from the same parent application, the ‘600 and ‘862 patents, both entitled “Synthetic Insecticidal Crystal Protein Gene,” are directed to genetically engineered plant genes. Specifically, the relevant patent claims involve genetic engineering for the expression of Bt proteins, pesticides naturally produced by certain bacteria, in a variety of plants. Expression of the gene allows plants to make their own insecticides. To successfully integrate the native Bt gene into plants, the gene’s DNA sequences were modified for improved expression in plant systems. In particular, many of the modifications disclosed in the Mycogen patents involved changing the frequencies of duplicative amino acid encoding sequences, called codons, in the natural Bt gene to those frequencies of use preferred in plant cells.

At trial, the jury’s findings indicated that Monsanto’s products did not infringe the patentsin- suit and that earlier Monsanto research anticipated both patents as having constituted prior invention of the claimed subject matter. Because this same research led to what the jury considered noninfringing products, Mycogen asserted that the jury verdict was inconsistent. However, the district court subsequently granted Mycogen’s JMOL that the Monsanto products literally infringed the patents.

With regard to claim interpretation, Mycogen contended that the district court’s interpretation of the language “greater number of codons preferred” present in several claims of the ‘600 patent was incorrect. Mycogen contended that this language refers to those codons that appear most frequently for each amino acid. The district court defined a “preferred codon” to be any codon with a higher frequency of use in the host plant than the native Bt gene and, in turn, brings the modified Bt gene’s frequency of codon usage closer to that of the intended plant host. Thus, Mycogen’s definition only allows for one preferred codon, whereas the district court’s definition allows for more than one codon.

The Court affirmed the district court’s interpretation based upon the claims themselves. Finding both the patent specifications and prosecution histories inconclusive, the Court turned to the plain meaning of the claims. First, the Court noted that Mycogen did not literally use the term “most preferred codon” when it could have added this language to the claims. Second, the Court disagreed with Mycogen that this language as interpreted by the district court was synonymous with other claim language specifying a frequency of codon usage which more closely resembles the host plant. Also, the Court observed that a shortened Bt gene sequence, without any substitutions, could result in a closer frequency resemblance to the plant host, but not in a greater number of preferred codons. Thus, a distinction exists between these two pieces of claim language, which the district court correctly did not treat as identical.

Mycogen also objected to the district court’s jury instructions regarding the doctrine of simultaneous conception and reduction to practice as it related to Monsanto’s anticipatory research. Mycogen contended that the doctrine could only apply to product claims and, in any event, was a question of law that cannot be submitted to a jury. The Court rejected both arguments, finding that the doctrine is properly applicable to either product or method claims in an unpredictable art such as biology. Given the proper jury instructions, the Court ruled, this was a question of law that could be properly submitted to a jury.

With regard to prior invention, the Court found that the dispute centered entirely on Monsanto’s appreciation of the results of their research. Finding that Monsanto’s research efforts constituted a reduction to practice of the claimed invention of the Mycogen patents, the Court focused on Mycogen’s argument that Monsanto did not have a true reduction to practice because their researchers did not have an appreciation for having used the claimed methods of the Mycogen patents. The Court packaged Mycogen’s argument as one of “accidental anticipation,” then rejected it, noting that Monsanto was specifically conducting research directed towards finding a synthetic gene for improved Bt expression. In addition, the Court pointed to the testimony of Monsanto’s researchers that demonstrated their appreciation of the key claim limitations. The Court concluded that this was sufficient proof that Monsanto’s discovery was not accidental.