Schwarz Pharma, Inc. appealed the order of the United States District Court for the District of Minnesota entering summary judgment of noninfringement of U.S. Patent No. 4,743,450 in favor of Paddock Laboratories, Inc. Finding the district court did not err in its conclusion that prosecution history estoppel bars resort to the doctrine of equivalents, the Federal Circuit affirmed the noninfringement finding. 
| Schwartz Pharma and its corporate parent, Schwarz Pharma AG, are the exclusive licensees of U.S. Patent No. 4,743,450 ("the '450 patent"), owned by Warner-Lambert Co. The '450 patent relates to Angiotensin Converting Anzyme inhibitors combined with stabilizers for treating hypertension. This suit was initiated in response to Paddock's submission of an Abbreviated New Drug Application ("the ANDA") to the Federal Food, Drug, and Cosmetic Act for approval to market generic tablets containing moexipril hydrochloride ("MH") and magnesium oxide ("MgO"). At oral argument on Paddock's motion for summary judgment for noninfringement, the parties stipulated that Paddock's formulation did not literally infringe the '450 patent claims; thus, the only issue was whether there were genuine issues of material fact with respect to infringement under the doctrine of equivalents. The district court granted Paddock's motion for summary judgment that prosecution history estoppel, based upon the amendment, precluded infringement under the doctrine of equivalents. Specifically, independent claim 1 as filed recited "metal containing stabilizer" and independent claim 16 recited "an alkali or alkaline earth-metal salt" and both were later amended to recite "an alkali or alkaline each metal carbonate." Consequently, the district court held that the estoppel raised by that amendment precluded Paddock's formulation from infringing the claims. Affirming the lower court, the Federal Circuit first addressed Paddock's jurisdictional objection that Schwarz Pharma did not have standing to appeal without participation of patentee Warner-Lambert who did not appeal the order of the district court(although it participated in the suit at the lower court). Agreeing with Schwarz, the Federal Circuit held that the joinder of the patent owner in the initial processing is necessary to avoid "the possibility that the alleged infringer would be subject to multiple actions", but that the requirement is "one of prudential rather than constitutional standing." Thus, the court reasoned that "Warner-Lambert has already been joined in the infringement action, and, if not joined in the appeal, will continue to be bound by the judgment of the trial court and the [Federal Circuit]." Thus, Warner-Lambert's participation in the appeal was unnecessary. On the matter of whether the prosecution history precluded infringement under the doctrine of equivalents because the patentee "never claimed compositions or processes involving MgO," the court found that the specification disclosed more than Schwartz Pharma contended, and that the plain meaning of "metal containing stabilizer" and "alkali or alkaline earth metal salt" encompassed MgO. Thus, amendment of the independent claims to recite "alkaline earth metal carbonate" raised an estoppel for all foreseeable equivalents relinquished by the amendment. Indeed, the amendment was made in response to an obviousness rejection by the examiner and thus is presumed to have been made for reasons of patentability. Therefore, the Federal Circuit held that the presumption of surrender applied to MgO because it fell within the territory between the language of the original and the amended claims of the '450 patent. And, because MgO was known as a stabilizer in the field of pharmaceutical compositions, Scharz Pharma failed to rebut the presumption of surrender by demonstrating that MgO was not a foreseeable equivalent. |