Patent Baristas

The University of California and Abbott appealed after the district court turned down their attempt to stop Dako from making and selling its HER2 FISH pharmDXTM kit, allegedly infringing U.S. Patents 5,447,841 and 6,596,479.   The Regents of the University Of California, Abbott Labs v. Dakocytomation California (06-1334, -1452; 07-1202)

The inventions claimed in the patents are improved methods for identifying and classifying chromosomes to detect chromosomal abnormalities associated with genetic disorders, degenerative diseases, and exposure to agents known to cause degenerative diseases, such as cancer.

There are three general types of chromosomal abnormalities: extra or missing individual chromosomes, extra or missing portions of a chromosome, or chromosomal rearrangements. Procedures in the prior art required that chromosomes be in the metaphase phase of the cell cycle because it was not possible to visualize nonmetaphase, or interphase chromosomes due to their dispersed condition in the cell nucleus, which is extremely difficult and time consuming, and almost impossible for tumor cells.

Other prior art techniques used probes comprised of DNA and RNA fragments for gene mapping and were limited by the nonspecificity of that technique — due to repetitive nucleotide sequences that were present throughout the chromosomes. Labeled probes would not only hybridize with the target chromosomal DNA, but with repetitive sequences as well, thereby producing false-positive results.

Abbott’s new technique allowed detection of chromosomal abnormalities in both metaphase and interphase cells using standard clinical and laboratory equipment.

In denying a preliminary injunction, the court concluded that appellants failed to show a likelihood of success on the merits of their infringement claim under the ’479 patent based on its claim construction of two claim limitations, of “morphologically identifiable chromosome or cell nucleus” and “heterogeneous mixture of labeled unique sequence nucleic acid fragments.” The court also based its conclusion on appellants’ failure to show a likelihood of success that the accused product met the “blocking nucleic acid” limitation of the ’841 patent under the doctrine of equivalents.

While an appeal was pending, the district court amended its basis for rejecting appellants’ proposed construction of the term “heterogeneous mixture of labeled unique sequence nucleic acid fragments.” The court amended “its previous order to the extent it improperly cite[d] 35 U.S.C. § 102 as the basis for questioning the validity of the claims of the ’479 patent” in light of the ’841 patent, and instead stated that the ’479 patent would likely be rendered invalid under the doctrine of nonstatutory (obviousness) double patenting.

After the district court held a Markman hearing, the court granted summary judgment of noninfringement of the ’479 patent as to all of the accused products based on its construction of the “heterogeneous mixture” limitation. The court further granted summary judgment of noninfringement on the ’841 patent, concluding that Abbott was barred from asserting infringement of the “blocking nucleic acid” limitation under the doctrine of equivalents. The court also denied summary judgment on the ’841 patent as to the remaining twenty accused products. The court did not address whether Dako’s products met the “morphologically identifiable” limitation — a claim limitation that was at issue in the preliminary injunction motion.

Abbott argued that the district court erred in its construction of the claim limitation “heterogeneous mixture of labeled unique sequence nucleic acid fragments” to mean “heterogeneous mixture of labeled nucleic acid fragments that includes only unique sequence fragments,” whereas Dako’s kits contain repetitive sequences. Abbott said that the court erred by interpreting that language to mean that the heterogeneous mixture excludes repetitive sequences.

According to Dako, the claim language supports a construction that excludes repetitive sequences because the specification supports that construction in statements and embodiments and in light of the prosecution history of the ’479 patent. In addition, Dako argues that the doctrine of claim differentiation is not an absolute rule. Where construction of an independent claim leads to a clear conclusion inconsistent with a dependent claim, the doctrine of claim differentiation must yield.

The CAFC held:

Although the district court erred in its reasoning as set forth above, we nonetheless will affirm the court’s construction of the heterogeneous mixture limitation. The court correctly evaluated the prosecution history and determined the proper claim construction. We also agree with the court’s conclusion set forth in its summary judgment decision that the patentees disclaimed embodiments that include repetitive sequences during the prosecution of the ’479 patent. Thus, the district court was correct in concluding that the accused products, which employ a mixture that includes repetitive sequences, do not infringe the ’479 patent.