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Court Affirms Equivalents of “Mystery Swine Disease” Vaccine Patent

February 21, 2003

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Last Month at the Federal Circuit - March 2003

Judges: Clevenger (author), Mayer, and Rader

In Boehringer Ingelheim Vetmedica, Inc. v. Schering-Plough Corp., No. 02-1026 (Fed. Cir. Feb. 21, 2003), the Federal Circuit affirmed the district court’s judgment that U.S. Patent No. 5,476,778 (“the ’778 patent”) is infringed and not invalid.

The PTO issued Boehringer Ingelheim Vetmedica, Inc. (“Boehringer”) the ’778 patent for methods of growing, isolating, and attenuating the virus responsible for Porcine Reproductive Respiratory Syndrome (“PRRS”) after Boehringer discovered a simian (monkey) cell line could be used successfully as a host.

Boehringer filed suit against Schering- Plough Corporation and Schering Corporation (collectively “Schering”), alleging that Schering’s vaccine virus, which is grown on a similar simian cell line, infringed the method claimed by Boehringer’s ’778 patent. The district court denied Boehringer’s motion for a preliminary injunction when Boehringer was unable to show that Schering’s obviousness challenge lacked substantial merit or that irreparable harm would result.

Following the denial of various motions for SJ, the district court considered Schering’s inequitable-conduct defense separately and held no inequitable conduct during prosecution of the ’778 patent. At trial, the jury found that Schering had infringed the ‘778 patent by equivalence and that the patent was not obvious and, therefore, not invalid. The district court denied Schering’s motions for JMOL or new trial and entered judgment for Boehringer.

Schering appealed the denial of its motion for JMOL, asserting that the district court had incorrectly construed the claims and the jury’s verdict was not supported by substantial evidence. Boehringer cross-appealed, asserting an erroneous claim construction.

The Federal Circuit reviewed the interpretation of the term “isolating” in the context of the preamble claim language: “A method of growing and isolating swine infertility and respiratory syndrome virus, ATCC-VR2332, which comprises inoculating the virus on a full or partial sheet of simian cells . . . .” The Court noted that preamble language will limit the claim if it recites not merely a context to which the invention may be used, but the essence of the invention, without which performance of the recited steps is nothing but an academic exercise. In other words, the PRRS virus is “isolated” each time the virus is propagated into a fresh tissue culture bottle, not just when the virus is initially isolated from an infected pig. The Court concluded that the district court had properly recognized “isolating” as part of the definition of the claimed subject matter and was, therefore, a limitation of the claim.

The Federal Circuit disagreed with the district court’s construction that the claim language “until . . . CPE is observed” means “until there is a significant degree of CPE” (cytopathic effect). Rather, the Federal Circuit held that the limitation merely defines the minimum period for incubation of the inoculated cell sheet. Given the infringement analysis, however, this difference in construction was considered harmless error.

Concerning the finding of infringement, the Federal Circuit agreed that Schering’s VR2525 strain is equivalent to the claimed strain. Schering argued for no equivalence because, when administered to a pig, its virus will generate a protective immune response to PRRS, while a pig inoculated with Boehringer’s virus develops PRRS. According to Schering, this effect underscored differences in function, way, or result and precluded a finding of insubstantial differences between the strains. The Federal Circuit concluded, however, that what happens when the virus is administered to a pig is irrelevant to the assessment of whether the two viral strains are equivalent in the in vitro culture method defined by the claim. Therefore, the Federal Circuit agreed that substantial evidence supported the jury’s verdict of equivalence.

The second issue of equivalence concerned the phrase “until . . . CPE is observed.” The Federal Circuit relied upon expert testimony that Schering’s practice of incubating a viral culture for a defined period of time performs the same function, way, and result to support the jury’s verdict of equivalence.

Finally, the Federal Circuit agreed with the district court’s analysis of the obviousness issue. Noting that a showing of obviousness requires a motivation or suggestion to combine or modify prior art references, coupled with a reasonable expectation of success, the Court concluded that the jury was entitled to conclude that such a showing had not been made. In particular, the Court pointed to references reporting failure of attempts to isolate PRRS viruses with monkey-kidney cells, thus negating an expectation of success.