Federal Circuit holds claims for infringement under the doctrine of equivalents barred by prosecution history estoppel

Pharma Tech Solutions, Inc., Decision IT Corp., v. LifeScan, Inc., LifeScan Scotland, LTD., Johnson and Johnson, Appeal 2019-1163, decided November 22, 2019. pharma-tech-solutions-v-lifescan

Procedural Background

Pharma Tech Solutions, Inc. sued LifeScan, Inc. for infringement of US Patent Nos. 6,153,069 and 6,413,411, both directed to blood glucose monitoring systems.

As originally presented, the claims of the ‘069 patent extended to any test strip with two working electrodes.  During prosecution, the claims were amended to require obtaining at least two readings, converting the readings to analyte concentration measurements and comparing the plurality of analyte measurements.   These amendments were argued to differentiate the claims from the prior art in three responses, ultimately leading to the allowance of the ‘069 patent.

After dropping its literal infringement claim, LifeScan moved for summary judgement on the doctrine of equivalents infringement claims, asserting that when Pharma Tech amended their claims to require conversion of the readings to analyte concentration measurements, and comparison of those analyte concentration measurements, Pharma Tech surrendered any claim scope covering systems and methods that do not compare analyte concentration measurements.  LifeScan further argued that Pharma Tech’s arguments distinguishing the prior art on the basis of these amendments constituted clear and ambiguous disclaimers of meters that do not perform the claimed conversion and comparison steps.

For their part, Pharma Tech argued that their amendment to include “conversion” and “comparison” steps was only tangential to the real purpose of the amendment, which was to require a linear comparison of multiple measurements.

The district court rejected Pharma Tech’s arguments, and held that Pharma Tech’s claims were barred by both amendment and argument based estoppel.

Amendment-based prosecution history estoppel

In Festo, The Supreme Court recognized that a “patentee’s decision to narrow his claims through amendment may be presumed to be a general disclaimer of the territory between the original claim and the amended claim.”  Festo Corp., Shoketsu Kinzoku Kogyo Kabushiki Co., 535 US 722, 740 (2002).  This presumption can be overcome if patentee can show:  (1) the equivalent was “unforeseeable at the time of the application;” (2) the rationale underlying the amendment bears no more than a tangential relation to the equivalent in question; or (3) some other reason suggesting that the patentee could not reasonably have been expected to have described the insubstantial substitute in question.  Id. at 740-41.

Argument-based prosecution history estoppel

In order for argument-based prosecution history estoppel to apply, the “prosecution history must evince a “clear and unmistakable surrender of subject matter.” Conoco, Inc. v. Energy & Envtl. Int’l, LC, 460 F.3d 1349, 1363 (Fed. Cir. 2006).  Further, “clear assertions made during prosecution in support of patentability, whether or not actually required to secure allowance of the claim, may also create an estoppel…[t]he relevant inquiry is whether a competitor would reasonably believe that the applicant had surrendered the relevant subject matter.”  PODS, Inc. v. Porta Stor, Inc., 484 F.3d 1359, 1368 (Fed. Cir. 2007)

“The inventors’ clear statements not only establish argument-based estoppel, but also negate Pharma-Tech’s reliance on the tangential relation exception”

The Federal Circuit affirmed the district court, and in resolving the argument-based estoppel issue, held that Pharma Tech had clearly and unmistakably surrendered systems that do not convert and compare analyte concentration measurements:

Here, the inventors clearly and unambiguously distinguished their invention over the prior art based on the converting and comparing limitations added by the October 1997 amendment.  We thus agree with the district court that the inventor’s remarks … make clear that the amendment was made to achieve patentability – and for reasons more than tangentially related to the equivalent at issue.  The objectively apparent reason for the October 1997 amendment was to distinguish the invention over prior art systems that measured and displayed a diffusion limiting current reading.  Slip opinion, page 15-16.

Rejection of Pharma Tech’s arguments

Pharma Tech argued that the claim limitations of “converting” and “comparing” were already known in the art, and so, the amendments to add them must have been made for some other reason than to garner patentability.  Citing, Pioneer Magnetics, Inc. v. Micro Linear Corp., 330 F.3d 1352, 1356 (Fed. Cir. 2003).  In response, the Federal Circuit stated:

That the October 1997 amendment may have ceded more claim scope than necessary to overcome prior art does not mean that the tangential relation exception applies here.  Indeed, we have held that “[t]he fact that the inventors may have thought after the fact that they could have relied on other distinctions in order to defend their claims is irrelevant” to discerning the objective reason for their amendment.  Int’l Rectifier Corp. v. IXYS Corp., 515 F.3d 1353, 1359 (Fed. Cir. 2008) (“Amendments are not construed to cede only that which is necessary to overcome the prior art.”)

Pharma Tech then tried to analogize their fact pattern to other cases where the Court held that amendment-based prosecution history estoppel did not apply.  In each, the Court held that the remarks accompanying the amendment did not emphasize or rely on the added claim language to distinguish the prior art in a manner relevant to the asserted equivalent.  For example, Pharma Tech argued that Insituform Technologies, Inc. v. CAT Contracting, Inc., 385 F.3d 1360 (Fed. Cir. 2004) was analogous.  The Court disagreed, stating:

This court held that Insituform’s amendment narrowing the claim to a one-cup vacuum process located near a resin source was merely tangentially related to an equivalent multiple-cup vacuum process because the rationale underlying the amendment “was to avoid the need to use a large compressor when the vacuum is created a significant distance from the resin source.”  Id. at 691.  Insituform noted “no indication in the prosecution history of any relationship between the narrowing amendment and a multiple cup process.”  Id.

After differentiating several others, the Court held:

Here, by contrast, the rationale for the October 1997 amendment – avoiding prior art that does not convert a plurality of current readings or compare a plurality of analyte concentration measurements – directly relates to the accused equivalent, a system which also does not convert a plurality of current readings or compare a plurality of analyte concentration measurements.  Slip opinion, page 20.