by Dennis Crouch
Ajinomoto Co., Inc. v. ITC; CJ CheilJedang Corp. v. ITC (Fed. Cir. 2019)
Some aspects of patent law are unduly complicated. Here is one: Prosecution History Estoppel (PHE) as applied to the Doctrine of Equivalents (DOE).
The DOE finds infringement when someone is practicing something very similar (albeit different) than what is literally claimed. Although the doctrine is court-created, courts are also wary of the potentially unmoored doctrine and thus have created a number of major limitations on the doctrine that have severely limited its scope. Prosecution History Estoppel is one such limitation and arises when patent claims are narrowed during patent prosecution (something that happens in the vast majority of cases).
Under PHE, a narrowing limitation during prosecution is “presumed to be a general disclaimer of the territory between the original claim and the amended claim.” Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722 (2002). In Festo though, the Supreme Court identified the disclaimer as rebuttable upon proof that “the amendment cannot reasonably be viewed as surrendering a particular equivalent.” The high court particularly identified three mechanisms of such proof:
- The equivalent was unforeseeable at the time;
- The reasons for the amendment bear only a “tangential relation to the equivalent”; or
- “some other reason.”
The Federal Circuit has noted in the past that these exceptions are “very narrow” Cross Med. Prods., Inc. v. Medtronic Sofamor Danek, Inc., 480 F.3d
1335, 1342 (Fed. Cir. 2007)). Further, proof of the exceptions and the patent applicant’s intent must be “objectively apparent” and “discernible from the prosecution history record.”
Like I said, unduly complicated. The easiest way to state this (recklessly ignoring the various burdens) is that PHE applies to cut-of DOE when there is a narrowing amendment reasonably related to the equivalent at issue.
I also have to say that this is a really poorly written opinion by Judge Taranto in that it muddles together various facts over many pages — often without spelling out which facts are relevant for what purposes. The dissent by Judge Dyk is much more clear-headed as written.
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Ajinomoto’s patent claims E. coli bacteria genetically engineered with the yddG gene to increase L-amino acid production (including tryptophan) and also claims the method of making the amino acids by cultivating the aforementioned bacteria. Ajinomoto filed a complaint against CJ CheilJedang in the USITC, and the Commission eventually sided with the patentee — finding infringement under the doctrine of equivalents.
The claim structure here is odd. Claim 20 is the claim at issue and is couched as a multiple dependent method claim — the method of producing the L-amino acid by cultivating bacteria “according to any one of claims 9-12, 13, 14, 15-18, or 19.” The appeal here focuses only on claim 20’s L-amino acid production according to claim 9.
The dissent explains why CJ does not literally infringe:
Claim 9 covers a recombinant bacteria having [sic] a “protein consist[ing] of the amino acid sequence of SEQ ID NO: 2.” Id. col. 22, ll. 56–57. This corresponds to the amino acid sequence of E. coli YddG protein (a membrane-bound protein involved in the cellular export of aromatic amino acids). [CJ’s] Strain B does not
literally infringe claim 9 because it produces a protein with an amino acid sequence that differs from SEQ ID NO: 2. Instead, Ajinomoto asserts infringement under the doctrine of equivalents, arguing that Strain B’s non-E. coli YddG protein is equivalent to the E. coli YddG protein (SEQ ID NO: 2) in claim 9.
Although not literally the same as what was claimed, the ITC found that it was the equivalent and therefore infringing. On appeal, the Federal Circuit agreed — that DOE applies generally, but then focused on whether it was limited by PHE.
The original claim language covered SEQ ID NO: 2 along with modification such as “deletion, substitution, insertion or addition of one or several amino acids” of SEQ ID NO: 2. That claim was narrowed after an anticipation rejection to get around a different naturally occurring protein (YfiK). By narrowing the claim, it also now excludes the particular YddG protein variation used by CJ.
On appeal, the Federal Circuit held that the purpose of the appeal was to get around the YfiK prior art, not the YddG prior art. As such, the reasons for the amendment were merely tangential to the equivalent in question.
Judge Dyk writing in dissent argued the other side:
Originally, the claim covered proteins with amino acid sequence variations from SEQ ID NO: 2, which would have included the non-E. coli YddG protein at issue here. The examiner rejected the original claim based on anticipating prior art, and the patentee responded with a narrowing amendment. Instead of continuing to define the covered proteins in terms of amino acid sequence variations from SEQ ID NO: 2, the patentee deliberately chose to redefine the claimed proteins in terms of the ability of their encoding nucleotide sequences to hybridize with SEQ ID NO: 1 under the claimed conditions. The amended claim language excluded the prior art protein (Livshits) because it was made based on a nucleotide sequence that did not meet the newly added hybridization requirement. The accused equivalent is similarly not covered by the amended claims because it is produced based on an encoding nucleotide sequence that does not hybridize with SEQ ID NO: 1 under the claimed conditions. Thus, I do not see how the reason for the narrowing amendment is tangential to the accused equivalent. . . .
In my view the tangential exception cannot apply. The equivalent is directly related to the reason for the amendment—to exclude those proteins made by an encoding nucleotide sequence that does not hybridize with SEQ ID NO: 1 under the specified conditions.
The majority disagreed with this analysis and affirmed the infringement holding.