“According to the Federal Circuit, the goal of prosecution history estoppel is to prevent patentees from recapturing subject matter surrendered from the literal scope of the claim during prosecution.”
On November 22, the U.S. Court of Appeals for the Federal Circuit (CAFC) affirmed a decision of the District of Nevada granting summary judgment of noninfringement under the doctrine of equivalents.
Pharma Tech Solutions, Inc. (Pharma Tech) sued LifeScan, Inc. (LifeScan) for infringement of U.S. Patent Nos. 6,153,069 (the ‘069 patent) and 6,413,411 (the ‘411 patent). The patents are directed toward home use, blood glucose monitoring systems for individuals with diabetes. Previous monitoring systems determined blood glucose concentration from the Cottrell current drawn and measured from a patient’s oxidized blood sample. The specification of the ‘069 and ‘411 patents claims to improve on these systems by “eliminating several of the critical operator dependent variables that adversely affect the accuracy and reliability” of the previous systems. The invention performs multiple Cottrell current measurements (opposed to just the one) and converts these into analyte concentrations. It then compares the results for better accuracy, notifying the user if the results fall outside of an acceptable range of each other to indicate a system error.
LifeScan’s OneTouch Ultra system is the product accused of infringing the patents. The meter measures current from two different electrodes and conducts a “Current Difference Test” to compare the results. Upon passing the test the meter calculates the final current, which translates into the blood glucose reading. The meter does not convert multiple Cottrell current readings into analyte concentration measurements, nor does it compare them, so LifeScan’s system does not literally infringe the ‘069 claim. However, Pharma Tech asserted that the patent infringes under the doctrine of equivalents, because “an analyte measurement can be expressed at a current at a given time or as a concentration.”
To begin, the CAFC reviewed the prosecution history of the ‘069 patent (and extended this review to the related ‘411 patent). Claim 4 was initially rejected by a patent examiner at the United States Patent and Trademark Office (USPTO) in view of the prior art: U.S. Patent No. 5,385,846 (the Kuhn patent); U.S. Patent No. 5,288,636 (the Pollmann patent); and U.S. Patent No. 5,108,564 (the Szuminsky patent). It was then amended, with the amendments requiring: 1) at least two Cottrell current readings; 2) conversion of those readings to analyte concentration measurements; and 3) linear comparison of the analyte concentration measurements. In a second office action the claims were rejected as anticipated by U.S. Patent No. 5,508,171 (the Walling patent) and as obvious over Walling in view of the Szuminsky patent or U.S. Patent No 5,243,516 (the White patent). After a third office action rejection, the inventors filed a response distinguishing the prior art based on their “converting” and “comparing” limitations. They emphasized that a system that involves taking different Cottrell current readings, converting them into two different analyte concentration measurements, and then comparing the two analyte concentration measurements has not been taught by the prior art. The examiner then issued a notice of allowability for the ‘069 patent, and the ‘411 continuation issued subsequently.
Nevada District Court Findings
In the present suit involving the doctrine of equivalents, Pharma Tech defined the relevant equivalent to its invention as “the functionality of a system that: a) measures current at two different times; b) compares the current to ensure they are within a prescribed percentage and; c) converts the current readings into a glucose concentration. LifeScan argued that when the inventors amended their claims during prosecution of their patent to require conversion of the Cottrell readings to analyte concentration, they surrendered claim scope covering systems and methods that do not compare analyte concentrations. Additionally, they argued that Pharma Tech’s arguments during prosecution in distinguishing the prior art disclaimed meters that don’t perform the claimed conversion and comparison steps. The district court held that amendment-based prosecution history estoppel barred Pharma Tech’s infringement claims.
The CAFC Sides with LifeScan
According to the Federal Circuit, the goal of prosecution history estoppel is to prevent patentees from recapturing subject matter surrendered from the literal scope of the claim during prosecution and can occur in two ways: 1) By making a narrowing amendment to the claim; or 2) By surrendering claim scope through argument to the patent examiner. Pharma Tech relied on an exception to the presumption that it disclaimed the “territory” between the original and amended claims, arguing that the rationale for its amendment had no more than a tangential relation to the equivalent in question. The CAFC agreed with the district court and held that both amendment-based and argument-based prosecution history estoppel bar the infringement claims under the doctrine of equivalents. Under amendment-based estoppel, the CAFC found that Pharma Tech’s asserted equivalent was within the surrendered territory of the ‘069 patent. Additionally, according to the CAFC, under argument-based estoppel Pharma Tech’s arguments to the patent examiner surrendered systems that do not convert Cottrell readings to analyte concentrations for comparison. In order to distinguish the invention over the prior art and thus be granted a patent, Pharma Tech relied on its converting and comparing limitations added by amendment. Thus, the CAFC found that there were reasons more than tangentially related to the equivalent at issue, such as achieving patentability. All other arguments made by Pharma Tech were found to be unpersuasive by the court.
Ultimately, the CAFC found that because LifeScan’s meter does not convert diffusion limiting current readings to analyte concentration measurements and then compare the measurements to detect errors, and because Pharma Tech is barred in its infringement argument by prosecution history estoppel, LifeScan did not infringe Pharma Tech’s ‘069 or ‘411 patents.