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Tangential Exception Applied to Prevent Prosecution History Estoppel

06-1334,-1452 07-1202
February 28, 2008

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Last Month at the Federal Circuit - March 2008

Judges: Mayer, Lourie (author), Prost (dissenting-in-part)

[Appealed from: N.D. Cal., Judge Patel]

In Regents of the University of California v. Dakocytomation California, Inc., Nos. 06-1334, -1452, 07-1202 (Fed. Cir. Feb. 28, 2008), the Federal Circuit affirmed the district court’s denial of a preliminary injunction, affirmed-inpart the grant of SJ of noninfringement as to one patent, and reversed-in-part the district court’s grant of SJ of noninfringement as to a second patent. The Court remanded for further proceedings in light of its revised claim construction and its holding that the patentee is not precluded from asserting infringement of the claim limitation “blocking nucleic acid” under the DOE.

The Regents of the University of California, Abbott Molecular, Inc., and Abbott Laboratories, Inc. (collectively “the Regents”) are the owners and exclusive licensees of two patents, U.S. Patent Nos. 5,447,841 (“the ’841 patent”) and 6,596,479 (“the ’479 patent”). The ’841 and the ’479 patents are directed towards improved methods for identifying and classifying chromosomes in order to detect chromosomal abnormalities. Dako A/S and Dako North America, Inc. (collectively “Dako”) manufacture and sell HER2 FISH pharm DX kits (“HER2 kits”), which the Regents allege infringe the ’841 and the ’479 patents. The district court denied the Regents’ motion for a preliminary injunction to enjoin manufacture and sale of the HER2 kits, concluding they failed to show a likelihood of success on the merits in light of its claim construction determinations. The Regents appealed from this denial. Additionally, the district court later granted partial SJ of noninfringement based, inter alia, on its claim construction determinations and the conclusion that the Regents were barred from asserting infringement of a claim limitation under the DOE. The Regents filed an interlocutory appeal after the district court certified its order granting partial SJ of noninfringement.

On appeal, the Federal Circuit considered the preliminary injunction and SJ appeals together in view of the overlapping issues affecting both appeals. First, the Court affirmed the district court’s construction of a “heterogeneous mixture of labeled unique sequence nucleic acid fragments,” a limitation that is required by every claim of the ’479 patent. The Court stated that the district court initially erred in reasoning that the heterogeneous mixture excludes repetitive sequences in light of the ’841 patent, which the district court characterized as prior art to the ’479 patent. After realizing its error, however, the district court issued an amended preliminary injunction order that instead rejected the Regents’ proposed claim construction because it would likely render the ’479 patent invalid for obviousness-type double patenting in view of the ’841 patent. The Court agreed that the patentee disclaimed embodiments that included repetitive sequences during prosecution of the ’479 patent and that the accused products, which employ a mixture that includes repetitive sequences, did not infringe the ’479 patent.

In fact, the Court found that the prosecution history “sheds decisive light” on the scope of the claim term. Slip op. at 12. During prosecution of the ’479 patent, the original claim was cancelled and replaced with a new independent claim after the examiner issued rejections for lack of enablement, anticipation, and indefiniteness. The Court concluded that the patentees added the “unique sequence” limitation to this claim to overcome the enablement rejection and that statements made during prosecution with respect to this limitation evidenced a clear and unmistakable intent to limit the claims to embodiments that excluded repetitive sequences from the DNA mixture to disable the hybridization capacity of those repetitive sequences. Though the patentees did not expressly state that this limitation was added in response to the examiner’s enablement rejection, the Court noted that the examiner recognized that the original claim failed to include a limitation directed towards a problem that existed in the prior art—reducing the nonspecific binding of repetitive sequences— and that this problem would not arise with the new claim that restricted the heterogeneous mixture to labeled probes of “unique sequences.” The Court also stated that this conclusion was supported by the patentees’ decision to limit the ’841 patent to the blocking method claims and to pursue certain claims in the ’479 patent.

The Court rejected the Regents’ argument that the “unique sequences” limitation was added to overcome the anticipation rejection and had nothing to do with the issue of nonspecific binding of repetitive sequences. The Court noted that one of the anticipation references disclosed the unique sequence probes and that the patentees’ statements accompanying the amendment pointed to other amended claim language to overcome the anticipation rejection. Thus, the Court found “no basis for reversing the [district] court’s claim construction.” Id. at 18. Having found that the patentee limited the scope of the heterogeneous mixture to one that contains only unique sequences of nucleic acid fragments, the Court affirmed the district court’s grant of SJ of noninfringement as to the ’479 patent.

The Court then turned to the district court’s determination on SJ that the ’841 patent was not infringed by two accused products—the HER2 kit and the TOP2A kit. The Court concluded that the district court erred in applying prosecution history estoppel to the claim limitation “blocking nucleic acid,” which is present in all claims of the ’841 patent. The Court stated that because the prosecution history suggests that the patentees limited the claim to the blocking method at least in part to overcome the examiner’s rejections, the patentees presumptively surrendered all equivalents of the “blocking nucleic acid” limitation. However, the Court determined that the prosecution history reveals that in narrowing the claim to overcome the prior art rejections, the focus of the patentees’ arguments centered on the method of blocking, not on the particular type of nucleic acid that could be used for blocking. Indeed, the “nucleic acid” limitation was never narrowed during prosecution and was not at issue in the office action rejecting the claims, the Examiner Interview Summary Record, or the patentees’ remarks accompanying the amendment. Thus, the Court concluded that the Regents met their burden of showing that the amendment did not surrender the equivalent in question because the narrowing amendment was only tangential to the accused PNA equivalent found in Dako’s accused kits—the peptide nucleic acid. Accordingly, the Court remanded this issue for the district court to consider whether Dako’s products infringe the ’841 patent under the DOE.

In considering the preliminary injunction denial, the Federal Circuit noted that it already considered the “heterogeneous mixture” claim construction issue and agreed with the district court’s construction of this claim limitation. Thus, it also affirmed the district court’s denial of the preliminary injunction based on the failure to show a likelihood of success that Dako’s HER2 kit met this limitation of the ’479 patent. The Federal Circuit then turned to the remaining issue presented in the preliminary injunction appeal—the construction of a “morphologically identifiable cell nucleus.” The Court noted that this issue need not be reached in order to consider the merits of the preliminary injunction denial, but decided to consider it in the interest of judicial efficiency, as the issue had been fully briefed and that term would likely be at issue on remand.

The Court determined that the district court erred in its construction of this term. First, the plain language of the claim term “morphologically identifiable cell nucleus” suggests that the nucleus must be identifiable by form or structure, and does not indicate that a full set of chromosomal DNA must be present in the cell nucleus in contrast to the district court’s construction of this term as “a single cell nucleus that contains the full complement of chromosomal DNA.” Dako did not dispute that the word “morphological” generally refers to form or structure, not to identity of chromosomal DNA content. Also, the prosecution history of the ’841 patent revealed that the term “morphologically identifiable cell nucleus” was added to the claim to clarify that the target chromosomal DNA remained in a natural biological structure during in situ hybridization. The Court stated that nowhere in the prosecution history, or the specification for that matter, did it find any indication that the “morphologically identifiable” language was added to impose a requirement that the cell nucleus must retain its full complement of chromosomal DNA. Thus, the Court held that the proper construction of “morphologically identifiable cell nucleus” is one that is capable of being identified by its form or structure.

Judge Prost dissented from the Court’s holding that prosecution history estoppel did not apply to the term “blocking nucleic acid.” Judge Prost stated that this conclusion was contrary to the Court’s precedent and to the proper application of prosecution history estoppel, as set forth by the Supreme Court. In her view, the fact that narrowing the claim to a method of blocking with a “blocking nucleic acid” may not have been necessary to distinguish over the prior art did not change the analysis. Here, the amendment narrowed the scope of the invention to a method of disabling repetitive sequences using “blocking nucleic acids” and the parties stipulated that “blocking nucleic acid” means “fragments of repetitive-sequence-enriched DNA or RNA.” Therefore, in Judge Prost’s view, the patentee surrendered methods of blocking other than with DNA or RNA. Judge Prost stated that it is irrelevant to the determination of the scope of the surrendered territory that to overcome the prior art references, the patentee did not need to amend the claims to the scope it used but instead could have amended the claims to a method of disabling repetitive sequences by blocking.

Judge Prost further concluded that the tangential exception of Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 739-40 (2002), the only one raised before the district court and on appeal, did not save the patentees from a prosecution history estoppel bar. Focusing on the question of whether the amendment was peripheral or not directly relevant to the alleged equivalent, Judge Prost concluded that the amendment limited the claims to a method of disabling repetitive sequences by blocking with DNA or RNA, which are nucleic acid sequences. The accused Dako kit equivalent (PNA), however, functions to do exactly that, i.e., to disable repetitive sequences. Thus, the purpose for the amendment was directly related to the equivalent—they both related to means for disabling repetitive sequences. Based on this analysis, Judge Prost concluded that the Regents should be estopped from asserting that PNA is an equivalent to “blocking nucleic acid” in the context of the ’841 patent.