In Bayer Cropscience AG v. Dow AgroSciences LLC, the Federal Circuit upheld the district court’s claim construction that interpreted “2,4-D monooxygenase” in accordance with its  established scientific meaning, even though the exemplified embodiment was shown not to be a “monooxygenase.” This case illustrates the risks of functional claim language, particularly if the recited function is proven to be inapplicable, but also if the specification does not provide adequate written description for the breadth of embodiments encompassed by the functional language.

The Patent At Issue 

The patent at issue was Bayer’s U.S. Patent 6,153,401, which relates to constructs and methods for “genetically modifying plants in order to confer resistance to a commonly used herbicide called 2,4-dichlorophenoxyacetic acid, or ’2,4-D’ for short.” The methods involve genetically modifying plants to express an enzyme that catalyzes a reaction that breaks the herbicide down “into something harmless to plants.” Claim 1 recites:

A recombinant gene, comprising a DNA sequence encoding a polypeptide having the biological activity of 2,4-D monooxygenase which is capable of being expressed in a plant, operably linked to a heterologous promoter capable of promoting the expression in a plant of a structural gene operably linked thereto.

Dependent claim 4 recites embodiments of claim 1 “wherein the DNA sequence is the structural gene sequence of FIG. 10.”

The “Monooxygenase” Issue

As summarized by the Federal Circuit, at the time the patent was filed it was known that “certain bacteria found in soil could grow on 2,4-D,” and that “those bacteria first convert 2,4-D into a substance called 2,4-dichlorophenol, or ’2,4-DCP,’ which the bacteria… use as a ‘source[] of carbon and energy.’” Thus, scientists were trying to identify the genes that encoded enzymes that catalyzed that reaction. According to the Federal Circuit decision, “[t]he inventors of the ’401 patent were the first ‘to isolate, to clone, and to characterize’ a gene that had that property, a gene from the soil bacterium strain Alcaligenes eutrophus JMP134.” The nucleotide sequence of that gene is set forth in Figure 10 of the patent, and is the only gene identified in the ’patent.

According to the Federal Circuit, although the inventors had identified an enzyme of interest, “they did not fully understand the enzymatic reaction that they were studying.” For example, while “the reaction requires the presence of the oxygen molecule, O2,… the inventors did not know where one of the two oxygen atoms wound up.” At the time the patent was filed, they and others in “the scientific community” believed that it “was incorporated into water.” In accordance with this understanding, the patent refers to the enzymes of interest as “monooxygenases.” Importantly, the record “established beyond dispute” that the term “monooxygenases” refers to “enzymes catalyzing a reaction in which one oxygen atom ends up in water and the second is incorporated into a product other than water.”

While the ’401 patent still was pending, it was determined that the enzyme it described was not a “monooxygenase” because the second oxygen atom does not end up in water, but rather is “incorporated into products other than water.” As such, the enzyme is properly characterized as a “dioxygenase.”

[D]espite the announcement of this discovery in the very title of the article, and Bayer’s knowledge of the article, Bayer did not alter the claims of its application—which did not mature into a patent until seven years after the 1993 discovery.

The Accused Products

The accused products relate to Dow AgroSciences’ genetically modified seeds that are resistant to 2,4-D and other herbicides. Dow’s genes are dioxygenases that catalyze a reaction in which 2,4-D converts to 2,4-DCP.

The District Court Decision 

Bayer asserted that its claims encompass “any enzyme that triggers cleaving of the side chain of 2,4-D to produce 2,4-DCP, even if it is a dioxygenase and even if it does not share other biological activities of the particular enzyme whose gene Bayer sequenced.” The district court rejected Bayer’s arguments, and construed the “monooxygenase” claim language in accordance with its ordinary eaning, i.e., as reciting enzymes that catalyze reactions in which one oxygen atom ends up in a water molecule. Since Dow’s enzymes are dioxygenases, Dow does not infringe under that claim construction.

The Federal Circuit Decision 

The Federal Circuit conducted a two-part analysis of Bayer’s claim construction arguments.

First, the court found that the intrinsic record did not support the broad claim construction.

The conclusion we draw is that there is no clear message that the patent gives Bayer’s broad meaning to “2,4-D monooxygenase” in place of the term’s accepted scientific meaning, which describes a particular mechanism of action.….

In short, as the district court explained, the claim language has a strong accepted scientific meaning. Bayer’s alternative construction strips the monooxygenase half of the claim phrase of its accepted descriptive meaning and then asserts a specification “definition” of the biological-activity half. We do not find enough in the specification or prosecution history to justify those steps.

Second, the court noted if the claims were construed as broadly as Bayer urged, they likely would be invalid under 35 USC § 112.

Bayer’s proposed construction broadly covers a class of enzymes defined by their function of causing cleaving of the side chain of 2,4-D, while its written description structurally identifies just one gene sequence and the enzyme it encodes. We have not articulated a comprehensive and precise formulation for identifying when such a combination runs afoul of Section 112(a)’s written description requirement; indeed, we have counseled against “bright-line rules” in this area.… But we have indicated the primacy of structural identification for inventions in certain areas like the one at issue here, and when we have adverted to the possibility of other means of identification, we have focused on whether such alternative means sufficiently correlate with structure….

The coverage of claim 1 that Bayer proposes would leave the ’401 patent far from providing even an indirect structural identification of all that would be within the claim’s scope. The enzymatic function—under Bayer’s construction, causing the cleaving of the side chain of 2,4-D—would be broad, yet the patent provides the DNA sequence (and hence amino-acid sequence) of just one embodiment. As the district court explained,… neither the patent nor the knowledge in the art showed that what Bayer offered in place of a description of the shared structure—the growth test—correlated closely with an enzyme’s structure. The patent provided what was “[a]t best. . . a roadmap [that would] ‘leav[e] it to the. . . industry to complete [the] unfinished invention.’”

Thus, the Federal Circuit affirmed the district court’s claim construction and the summary judgment of non-infringement.

Caveat Patentee

The Federal Circuit noted that the district court decision referenced precedential “decisions about the potentially unwelcome consequences of a patentee’s chosen claim language.” Further, the Federal Circuit remarked several times that the patentee was aware of the discovery that its enzyme was not a monooxygenase, but “did not change its claim language.” What is not clear from the Federal Circuit decision is who at Bayer was aware of the discovery and whether they were actively involved in prosecuting the patents.