By Donald Zuhn --
On February 28th, the Federal Circuit, in Regents of the Univ. of California v. DakoCytomation California, Inc.: (a) affirmed the denial by the District Court for the Northern District of California of a preliminary injunction sought by the Regents of the University of California, Abbott Molecular Inc., and Abbott Laboratories Inc. (Appellants), (b) affirmed in part the District Court's grant of summary judgment of noninfringement as to U.S. Patent No. 6,596,479, (c) reversed in part the District Court's grant of summary judgment of noninfringement as to U.S. Patent No. 5,447,841, (d) affirmed the District Court's construction of "heterogeneous mixture of labeled unique sequence nucleic acid fragments," (e) reversed the District's Court's construction of "morphologically identifiable cell nucleus," and (f) reversed the District Court's determination that Appellants were estopped from asserting that Dako's products meet a limitation of the '841 patent under the doctrine of equivalents. The Federal Circuit remanded the case to the District Court.
The '841 and '479 patents, which are owned by the Regents of the University of California and are exclusively licensed by Abbott, are directed to improved methods for identifying and classifying chromosomes in order to detect chromosomal abnormalities. The improved methods of the '841 and '479 patents seek to overcome two problems that existed in the prior art: (1) the requirement of prior art methods that chromosomes be in the metaphase stage of the cell-division cycle (when the chromosomes are condensed and microscopically visible) as opposed to the interphase stage (when the chromosomes are not condensed and therefore not microscopically visible), and (2) the nonspecificity of prior art methods that use nucleic acid probes to detect particular chromosomal sequences, which leads to unacceptable false-positive results. This nonspecificity is caused by the hybridization of the nucleic acid probes to repetitive nucleotide sequences scattered throughout the chromosomes; in effect, the repetitive sequences "interfere" with the ability of the nucleic acid probes to hybridize only with particular chromosomal sequences.
The claimed methods of the '841 and '479 patents overcome the problems in the prior art by eliminating the "interference" caused by repetitive sequences. In the methods of the '841 patent, the interference is eliminated by blocking repetitive sequences, and in the methods of the '479 patent, the interference is eliminated by removing the repetitive sequences. In particular, in the methods of the '841 patent, "blocking nucleic acid . . . fragments which are substantially complementary to repetitive segments" are added to "labeled nucleic acid . . . fragments which are substantially complementary to nucleic acid segments within the chromosomal DNA for which detection is desired," and in the methods of the '479 patent, "a heterogeneous mixture of labeled unique sequence nucleic acid fragments which are substantially complementary to nucleic acid segments within the interphase chromosomal DNA for which detection is desired" is used.
In September of 2005, Appellants brought suit against Dako for patent infringement, and then in October of 2005 filed a motion for preliminary injunction seeking to enjoin Dako from manufacturing and selling its HER2 kit. Based on the District Court's construction of the limitations "morphologically identifiable chromosome or cell nucleus" and "heterogeneous mixture of labeled unique sequence nucleic acid fragments" of the '479 patent, and its conclusion that Dako's product did not meet the "blocking nucleic acid" limitation of the '841 patent under the doctrine of equivalents, the District Court determined that Appellants had failed to show a likelihood of success on the merits with respect to their infringement claims, and therefore denied Appellants' motion.
The District Court subsequently issued a second order, amending the basis for its denial of Appellants' preliminary injunction motion. In particular, the District Court maintained its rejection of Appellants' proposed construction of "heterogeneous mixture of labeled unique sequence nucleic acid fragments," but on the grounds that adopting such a construction would render the '479 patent invalid under the doctrine of obviousness-type double patenting (the District Court had previously determined that adopting Appellants' construction, which only appears in the '479 patent, would render the '479 patent invalid in view of the '841 patent, which the Court determined to be prior art to the '479 patent). Appellants appealed both orders to the Federal Circuit.
While these appeals were pending, Dako moved for summary judgment of noninfringement. Following a Markman hearing, the District Court granted summary judgment of noninfringement as to the '479 patent based on the Court's construction of the "heterogeneous mixture of labeled unique sequence nucleic acid fragments" limitation, and granted summary judgment of noninfringement as to the '841 patent based on the Court's conclusion that Appellants were barred from asserting that two of Dako's products met the "blocking nucleic acid" limitation under the doctrine of equivalents (the Court denied summary judgment as to the '841 patent for twenty other Dako products). Following the District Court's order, the parties filed a joint motion to certify for immediate appeal, which the District Court granted, and the Federal Circuit then granted permission to appeal the interlocutory order.
On appeal, Appellants argued that the District Court had erred in: (1) construing the limitation "heterogeneous mixture of labeled unique sequence nucleic acid fragments," (2) applying prosecution history estoppel to the "blocking nucleic acid" limitation, and (3) construing the limitation "morphologically identifiable cell nucleus." With respect to the first issue, Appellants argued that the District Court erred in construing the limitation to mean that the heterogeneous mixture excludes repetitive sequences (Dako's kits contain repetitive sequences). Appellants based their argument on the doctrine of claim differentiation (some of the patent's dependent claims require repetitive sequences) and the District Court's improper reliance on the prosecution history (Appellants asserted that the term "unique sequence" was added during prosecution to clarify that the claimed method was related to the detection -- and not necessarily use -- of unique sequences).
Despite finding that the District Court erred in first concluding that the '841 patent was prior art to the '479 patent and then concluding that the '479 patent would be rendered invalid due to obviousness-type double patenting, the Federal Circuit affirmed the District Court's construction of the heterogeneous mixture limitation as well as the District Court's determination that some of Dako's kits contain repetitive sequences, and therefore, do not infringe the '479 patent. The basis of the Federal Circuit's affirmance was Appellants' ability to overcome an enablement rejection (the examiner argued that a mixture containing repetitive sequences would not work due to nonspecific hybridization) by limiting the heterogeneous mixture's composition to unique sequences. As for Appellants' claim differentiation argument, the Federal Circuit noted that "the presumption created by the doctrine of claim differentiation is 'not a hard and fast rule and will be overcome by a contrary construction dictated by the written description or prosecution history.'"
With respect to the "blocking nucleic acid" limitation, Appellants argued that the District Court erred in barring them from asserting that the peptide nucleic acids (PNAs) used in Dako's kits were an equivalent of the blocking nucleic acids recited in the claims (the parties had stipulated that the "nucleic acid" portion of the term was limited to DNA and RNA). In particular, Appellants asserted that since the "blocking nucleic acid" limitation was never narrowed during prosecution, the District Court improperly applied the doctrine of prosecution history.
The Federal Circuit concluded first that "[b]ecause 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." The CAFC then concluded that Appellants "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," and therefore, determined that the District Court erred in finding that Appellants were estopped from asserting that Dako's products infringe under the doctrine of equivalents. The Federal Circuit based its conclusion on the fact that when the patentees amended the claims to add the "blocking nucleic acid" limitation, they "argued that that the invention was new and nonobvious because it used the blocking method in connection with in situ hybridization for the detection of unique sequences" (emphasis added). Thus, the CAFC concluded that Appellants' narrowing amendment focused on the "blocking" aspect and not on the "nucleic acid" aspect of the limitation. The Federal Circuit, therefore, reversed the District Court's determination that Appellants were barred from asserting that Dako's PNA-containing kits infringed under the doctrine of equivalents.
Finally, with respect to the "morphologically identifiable cell nucleus" limitation, Appellants argued that the District Court erred in construing the term to mean "a single cell nucleus that contains the full complement of chromosomal DNA." Appellants asserted that the limitation "merely requires that the nucleus be 'capable of being identified by its form or function' and does not require the full set of DNA." The Federal Circuit agreed with Appellants, stating that "[s]ignificantly, nowhere in the prosecution history, or the specification for that matter, do we 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." The CAFC, therefore, determined that the District Court erred in construing this limitation.
Judge Prost dissented with respect to the portion of the majority opinion that holds that the doctrine of equivalents is not precluded by prosecution history estoppel because the tangential exception applies, writing that the majority's finding "is contrary to this court's precedent and to the proper application of prosecution history estoppel as set forth by the Supreme Court." Citing Norian Corp. v. Styker Corp., Judge Prost noted that:
[I]t frequently happens that patentees surrender more through amendment than may have been absolutely necessary to avoid particular prior art. In such cases, we have held the patentees to the scope of what they ultimately claim, and we have not allowed them to assert that claims should be interpreted as if they had surrendered only what they had to.
Observing that the patentees narrowed the scope of the claims from any method of eliminating interference from repetitive sequences to just the use of "blocking nucleic acid," 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 a method of disabling the hybridization capacity of repetitive sequences by blocking with a "blocking nucleic acid," but instead could have amended the claims to a method of disabling repetitive sequences by blocking.
Judge Prost concluded that:
To overcome the presumption of prosecution history estoppel "[t]he patentee must show that at the time of the amendment one skilled in the art could not reasonably be expected to have drafted a claim that would have literally encompassed the alleged equivalent." Here, the appellants could reasonably have been expected to have drafted a claim that encompassed blocking repetitive sequences using PNA. The appellants should, therefore, be estopped from asserting that PNA is an equivalent to "blocking nucleic acid" in the '841 patent.
Regents of the Univ. of California v. DakoCytomation California, Inc. (Fed. Cir. 2008)
Panel: Circuit Judges Mayer, Lourie, and Prost
Opinion by Circuit Judge Lourie; opinion dissenting-in-part by Circuit Judge Prost
Additional information regarding this case can be found at Patently-O.
Comments