Summary judgment of noninfringement reversed: challenge to reliability of expert testimony waivedSeptember 25, 2007

In a decision Friday, the Federal Circuit reversed a district court's grant of summary judgment of noninfringement. The court held the district court improperly made a factual determination regarding the reliability of an expert's test used to establish infringement. Based on statements made during summary judgment briefing and argument, the defendants could not argue the tests were unreliable for summary judgment purposes. When the test results were considered, there was a genuine issue of fact that precluded summary judgment.

The court affirmed the district court's claim construction, however, remanding the case for further proceedings.

More on In re Gabapentin Patent Litig. after the jump.

The case involved a patent for a drug called gabapentin that can be used to treat epilepsy as well as other cerebral disorders. Warner-Lambert's trade name for gabapentin is Neurontin®. During the manufacture and storage of gabapentin it is common for a contaminant, lactam, to form. Lactam is toxic and can induce seizures.

Warner-Lambert (which merged with Pfizer in 2001) holds a patent on a method of making and storing gabapentin that avoids lactam contamination. The two key limitations for purposes of the appeal were (1) that the pharmaceutical preparation should have a concentration of "less than 20 ppm of an anion of a mineral acid," and (2) that the preparation should contain "one or more pharmaceutically acceptable adjuvants" where the specification had identified eight adjuvants that promoted the formation of lactam.

Several companies made applications to the FDA in order to sell generic versions of gabapentin using the patented lactam-free method, and Warner-Lambert filed suit. The defendants, claiming that their processes did not meet the "less than 20 ppm" limitation or the adjuvant limitation, filed a motion for summary judgment. The district court heard testimony from experts on both sides and determined that a pH based test offered by Warner-Lambert was not sufficiently reliable to establish infringement and granted summary judgment in favor of the defendants. Warner-Lambert appealed this decision. The defendants cross-appealed claiming that they also did not infringe the patent because the district court did not properly interpret the two limitations noted above.

The Federal Circuit first dealt with exclusion of the expert testimony and the resultant summary judgment. The district court had determined that the test was unreliable because it had a margin of error of ± 5 ppm. The court took note of the fact that, even assuming the high end of the margin of error (+5), the tested compounds contained 17 ppm and were within the claim limitation. The court concluded that "drawing all reasonable inferences in favor of Warner-Lambert as the nonmovant, we conclude that Warner-Lambert adduced sufficient evidence to create a genuine issue of material fact whether Teva's samples met the 20 ppm claim limitation."

Further, the court held that to the extent the defendants were arguing that Warner-Lamber's expert's methodology was flawed, the argument was waived for summary judgment purposes. As described by the court:

In moving for summary judgment of noninfringement based on Warner Lambert’s inability to meet its burden of proof, appellees informed the district court that:

It is important to note for the record that Defendants strongly dispute the capability of pH testing to make any scientifically meaningful distinctions between gabapentin samples at the trace levels of acidity relevant to the '482 patent. However, for purposes of this motion, Defendants have placed that dispute to one side (as they must), and focused on the undisputed limitations on the precision of such comparative pH measurements.

Indeed, at the summary judgment hearing, appellees expressly stated that:

Teva’s experts vehemently dispute the validity of the data [Dr. Bartlett] relied on, but I want to ignore that dispute. Those factual issues are in dispute, but should not be part of this motion, and we, you can ignore them.

Thus, appellees limited their summary judgment motion to the issue of the undisputed limits of the test’s precision, viz., the ± 5 ppm margin of error, which we have considered. As such, appellees waived any argument challenging the validity, including challenges to the accuracy or reliability, of the pH testing method for purposes of summary judgment.

The court next turned to two alternatives grounds proposed by the defendants to affirm the judgment centering around claim construction issues. The first issue dealt with the district court's interpretation of the limitation "anion of a mineral acid" and the second dealt with the definition of the term "adjuvant."

The defendants argued that the district court erred when it interpreted "anion of a mineral acid" to mean "anion derived from a mineral acid." The defendants argued that the language of the claims should have included any anions in the solution and that their product did not infringe the patent under this interpretation. The court rejected this argument because do to so would ignore the phrase "of a mineral acid," which was not consistent with the rule that "claims are interpreted with an eye toward giving effect to all terms in the claim." Additionally, the court held that the district court's interpretation of the claim was consistent with the language in the specification.

The defendants also argued that the district court erred when it determined that an adjuvant must be "intimately mixed with gabapentin." The defendants claimed that an adjuvant could also be "located in the capsule shell or tablet coating." Given this interpretation, the defendants argued that they did not infringe as the shells and coatings of their gabapentin contained some of the adjuvants listed in the specification. The court rejected this argument, finding that it was inconsistent with the claim language and specification. Accordingly, the court reversed the grant of summary judgment.

To read the full opinion in In re Gabapentin Patent Litig., click here.

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