In Pharma Tech Solutions Inc. v. Lifescan Inc., et al., No. 2019-1163 (Fed. Cir. Nov. 22, 2019), the Federal Circuit affirmed the district court’s grant of Lifescan’s motion for summary judgment based on its finding that prosecution history estoppel barred Pharma Tech’s doctrine of equivalents infringement claim. The technology at issue involved blood glucose monitoring systems that required a user to insert a sample into a device that measured an electric current running through the sample and then converted the measurement into blood glucose level data.

 Pharma Tech’s patents covered a device that measured multiple electric currents from each sample, then converted each current reading into an analyte concentration measurement before comparing the different measurements to ensure accuracy and reliability. In contrast, the accused Lifescan device reported measurements as current over a given time rather than concentration and did not compare multiple readings of concentration levels to ensure accuracy.

Pharma Tech argued that the Lifescan device infringed under the doctrine of equivalents. During prosecution of the asserted patents, in response to anticipation and obviousness rejections, the applicant amended its claims to require both a conversion of current readings to analyte concentration and subsequent comparisons of those concentrations. As a result, the district court held that the claim amendments barred Pharma Tech’s claims of infringement under the doctrine of equivalents and granted Lifescan’s motion for summary judgment.

The Federal Circuit rejected Pharma Tech’s argument that its amendment bore no more than a “tangential relation” to the equivalent in question. The court held that Pharma Tech’s asserted equivalent was within the territory that its own inventors had surrendered during prosecution. Additionally, the court held that the “objectively apparent reason” for the claim amendments was to “distinguish the invention over prior art systems,” and thus were necessary for the application to achieve patentability. The court noted that even if Pharma Tech may have conceded more claim scope than was necessary, such concessions were irrelevant to the current argument at issue.

The Federal Circuit also rejected Pharma Tech’s argument for certain exceptions where amendment-based prosecution history estoppel does not apply when the amendment does not emphasize or rely on the added claim language. Instead, the court held that “the comparison of analyte concentration measurements was integral to the inventors’ . . . amendment.” Furthermore, the court held that the rationale for the amendments—avoiding prior art which did not convert current readings to analyte concentrations or compare the concentrations to each other—directly related to the accused equivalent. Rejecting all of Pharma Tech’s remaining arguments, the court upheld the district court’s findings and affirmed Lifescan’s motion for summary judgment.

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