Duck Salad: Don’t Let Claim Preambles Get Lost in the Weeds

Posted by Diana Borgas on Jun 12, 2017

Duck salad—not the tasty Asian dish, but rather a pesky aquatic weed that grows among rice crops—is the subject of the patent challenged in the recent IPR Aceto Agricultural Chemicals Corp. v. Gowan Company, LLC (IPR2016-00076). The Board’s final written decision illustrates a point that should not be overlooked: the broadest reasonable interpretation, which the Board applies to most claims in IPR, is not the broadest conceivable interpretation. The distinction made all the difference in this case. 

The Board’s decision concerned U.S. Patent No. 8,791,049, which relates to an herbicidal composition to combat the growth of the undesirable duck salad weed in rice crops. The challenged claim does not mention this specific use of the composition in the body of the claim, which is where claim requirements are typically found. Rather, the only mention of duck salad weed is in the preamble. Details in the preamble do not typically limit the scope of the claim, which would mean in this case that the challenged claim covers any use of the composition, not just for control or eradication of duck salad weed in rice crops.

Relying on the rule that the preamble is typically not limiting, and supporting its position based on the patent prosecution history—in which the examiner at one point characterized the preamble as merely reciting an intended use—the petitioner presented prior art concerning the use of the composition with corn crops.  None of the prior art references described using the composition to combat duck salad weed or its use in rice crops. The petition, therefore, turned on whether the preamble’s reference to duck salad weed limited the scope of the claim. If so, the petitioner had no prior art that disclosed that requirement.

The patent owner argued that the preamble provides more than just an intended use because it gives meaning to “effective amount”; namely, it informs that the compounds are in an amount effective for removing duck salad weed from rice crops. The patent owner further argued that, following the addition of the effective amount feature to the claim, the examiner clearly and unmistakably relied on the preamble’s recitation to distinguish the claim from the prior art.

The Board ultimately sided with the patent owner in holding that the preamble’s reference to use the composition against duck salad weed in rice crops limited the claims to that specific application. In so doing, the Board also pointed out the emphasis in the specification of the efficacy of the claimed composition against duck salad weed in rice crops. Since the petitioner’s prior art lacked that disclosure, it was insufficient to anticipate the claims, and the Board found the challenged claims patentable over the prior art. 


For petitioners, this decision is a reminder that the Board will entertain arguments to limit the scope of the claims, including that the preamble is limiting. Petitioners should not neglect to consider whether, in view of the body of the claim, the specification, and/or the prosecution history, the claims are actually narrower than the prior art and the broadest conceivable interpretation. 

For patent owners, the decision is a reminder that the Board may rely on the prosecution history to construe claim limitations. The Board’s willingness to narrow the claims based on the preamble is notable, given that it generally applies the broadest reasonable interpretation during IPR. This case illustrates that patent owners might be able to save their claims by arguing that the petitioner’s proposed construction, even if conceivable, is not reasonable in light of the claim preamble, specification and/or prosecution history. 

Both petitioners and patent owners should be aware of the proactive approach the Board may take in constructing and narrowing the scope of the claims. In view of this approach, petitioners and patent owners should not take the preamble lightly and let it get lost in the weeds.

Now, if you choose to make a duck salad (the dish), I recommend it with a honey ginger dressing. But you, unlike the challenged claim in this case, are not limited in how you prepare it. 

Topics: BioPharma

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