In CADENCE PHARMACEUTICALS INC. v. EXELA PHARMSCI INC., Appeal No. 2014-1184, the Federal Circuit affirmed a judgment of infringement under the doctrine of equivalents, over arguments of vitiation.
The district court found that Exela infringed Cadence’s patent under the doctrine of equivalents (“DOE”). On appeal, Exela argued that the district court’s scope of equivalents would vitiate a limitation of the claim. The Federal Circuit nevertheless affirmed the infringement judgment and noted that vitiation is not an exception or threshold determination that forecloses DOE. Instead, the determination of DOE depends on a proper assessment of the language of the claimed limitation and the substantiality of whatever differences may exist in the accused structure. Exela also argued that the district court erred in finding infringement because the phrase “optionally,” used in one of the steps in the claims, actually indicates a mandatory step due to statements made in the prosecution history. But the Federal Circuit concluded that the arguments made in the prosecution history did not amount to a clear and unmistakable disavowal of the unambiguous recitation of “optionally.”