Dexcom Inc v. Waveform Technologies Inc

1. Case Identification

• Case #: IPR2017-01051
• Patent #: 7,529,574
• Filed: March 8, 2017
• Petitioner(s): Dexcom, Inc.
• Patent Owner(s): Waveform Technologies, Inc.
• Challenged Claims: 1-19

2. Patent Overview

• Title: Method of Constructing a Biosensor
• Brief Description: The ’574 patent describes an indwelling analyte biosensor, such as for detecting glucose, intended for implantation. The sensor comprises a wire with an electrochemically active surface, at least two "nubs" of dielectric material extending from the surface to form a cavity, and a membrane system with an enzyme layer that surrounds the nubs and the active surface within the cavity.

3. Grounds for Unpatentability

Ground 1: Anticipation - Claims 1-5, 7-16, and 18-19 are anticipated by Wilson under 35 U.S.C. §102.

• Prior Art Relied Upon: Wilson (Patent 5,165,407).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that the Patent Owner’s broad construction of "nub" in co-pending litigation—to mean any "protruding structure" including the proximal and distal insulation portions of the sensor—causes the claims to read directly on Wilson. Wilson disclosed an implantable glucose sensor with a central wire (electrochemically active surface) coated in Teflon (dielectric material). A cavity was formed by cutting away a section of the Teflon, leaving proximal and distal portions of the insulation that Petitioner contended are "nubs" under the Patent Owner's construction. Wilson also disclosed applying an enzyme layer via a dip-coating process that surrounds these nubs and the active surface.
  • Key Aspects: The core of this argument was that by broadening the claim scope in litigation to read on Petitioner's accused device (which lacks the annular plates shown in the ’574 patent's figures), the Patent Owner had simultaneously broadened the scope to encompass the prior art Wilson sensor.

Ground 2: Obviousness - Claims 1-19 are obvious over Hagiwara under 35 U.S.C. §103.

• Prior Art Relied Upon: Hagiwara (Japanese Application # S57-110236).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner asserted that Hagiwara disclosed all elements of the claims across two described embodiments. Figure 1(A) of Hagiwara showed a wire sensor with a precious metal wire, an insulating layer forming proximal and distal dielectric nubs, and a cavity between them. While this embodiment did not include an enzyme layer, Figure 1(D) and the accompanying text explicitly taught incorporating a porous plastic layer with a fixed enzyme (e.g., glucose oxidase) to measure specific analytes. The membrane layers in Hagiwara were applied by a dip-coating procedure that encircled the nubs.
  • Motivation to Combine: Petitioner argued a POSITA would be motivated to combine the teachings of Hagiwara's embodiments. Hagiwara expressly taught that its base sensor (Fig. 1(A)) could be adapted to detect various analytes by incorporating an appropriate enzyme layer, as shown in the embodiment of Fig. 1(D). This modification was presented as a way to expand the sensor's functionality from measuring oxygen to measuring analytes like glucose, a predictable and explicitly suggested combination.
  • Expectation of Success: Success would be expected because Hagiwara described both the base sensor structure and the method for adding an enzyme layer as complementary parts of its invention, providing a clear path to the claimed configuration.

Ground 3: Obviousness - Claims 1-19 are obvious over Wilson in view of Hagiwara under 35 U.S.C. §103.

• Prior Art Relied Upon: Wilson (Patent 5,165,407) and Hagiwara (Japanese Application # S57-110236).

• Core Argument for this Ground:

  • Prior Art Mapping: This ground was presented as an alternative to the anticipation argument. Petitioner contended that Wilson disclosed all claim elements except for, arguably, an enzyme layer that clearly "surrounds" the nubs as a result of a dip-coating process. Hagiwara was introduced to cure any perceived deficiency, as it explicitly showed the results of dip-coating membranes over a similar side-window sensor, where the membranes extend beyond the sensor window and surround the proximal dielectric nub.
  • Motivation to Combine: Petitioner argued a POSITA would combine Wilson and Hagiwara to improve sensor manufacturing and performance. Both references disclosed side-window wire sensors and were analogous art. Wilson taught both "dropping" and "dip coating" as methods for applying an enzyme layer. A POSITA would have looked to a reference like Hagiwara for details on the dip-coating method, which was more scalable for mass production than precisely dropping fluid into a small cavity. Adopting Hagiwara's dip-coating technique, which covers the area beyond the sensing window, would be an obvious design choice to ensure the active surface is fully sealed, a predictable improvement.
  • Expectation of Success: A POSITA would expect success, as combining the known dip-coating method from Hagiwara with the sensor structure of Wilson was a simple substitution of one known enzyme application technique for another to achieve a predictable, more manufacturable result.

• Additional Grounds: Petitioner asserted additional obviousness challenges based on Wilson in view of Ryan, and Wilson in view of Ryan and Hagiwara. These grounds relied on similar arguments, introducing Ryan for its teachings on applying membrane layers via a dip-coating procedure onto Teflon-coated platinum wire sensors.

4. Key Claim Construction Positions

• "Nub": Petitioner argued that the Board should adopt the broad construction of "nubs" as "protruding structures," which the Patent Owner successfully advocated for in district court. This construction was not limited to the "annular plates" shown in the ’574 patent's preferred embodiment but also included the proximal and distal portions of dielectric insulation that remained after forming the sensor's active cavity. This broad construction was critical to Petitioner's arguments that the prior art met this limitation.
• "Surrounding... at least along said cavity": Based on the Patent Owner's litigation positions, Petitioner argued this phrase should be construed to mean that the enzyme layer must "encircle at least a portion of the nubs" from a cross-sectional perspective. This construction did not require the entire nub to be encased but was met if the enzyme layer covered the portion of the nub adjacent to the cavity, a feature Petitioner argued was disclosed by the dip-coating methods in the prior art.

5. Relief Requested

• Petitioner requested the institution of an inter partes review and the cancellation of claims 1-19 of the ’574 patent as unpatentable.