Dexcom, Inc. v. WaveForm Technologies, Inc.

1. Case Identification

• 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 is directed to an indwelling analyte biosensor, such as a glucose sensor. The technology involves a wire-based sensor with an electrochemically active surface, at least two "nubs" of dielectric material that 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 of Claims 1-5, 7-16, and 18-19 by Wilson

• Prior Art Relied Upon: Wilson (Patent 5,165,407).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Wilson discloses every element of the challenged claims, especially under the broad claim construction for "nub" adopted by the Patent Owner in co-pending litigation. Wilson describes an implantable glucose sensor with a central wire (the electrochemically active surface) coated in insulative Teflon. A cavity is formed by cutting away a portion of the insulation, which leaves remaining insulation on either side that function as "nubs." Wilson further teaches applying a multi-layer membrane system, including an enzyme layer, using a dip-coating process that, as described, would cover and surround the nubs and the active surface.
  • Key Aspects: The core of this argument rested on the Patent Owner's own litigation-driven claim construction. By arguing for a broad definition of "nub" that reads out the "annular plates" shown in the ’574 patent's figures, the Patent Owner allegedly broadened the claims to cover the prior art structure disclosed in Wilson, which the ’574 patent itself purports to improve upon.

Ground 2: Obviousness of Claims 1-19 over Hagiwara

• Prior Art Relied Upon: Hagiwara (Japanese Unexamined Patent Application Publication No. S57-110236).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner asserted that Hagiwara discloses two key embodiments that render the claims obvious. Hagiwara’s Fig. 1(A) shows a side-window sensor structure with a precious metal wire, an insulating layer forming dielectric nubs, and a cavity, but without an enzyme layer (for sensing oxygen). Hagiwara’s Fig. 1(D) explicitly teaches adding a porous plastic layer containing an enzyme (e.g., glucose oxidase) to such a sensor to detect specific analytes like glucose.
  • Motivation to Combine (for §103 grounds): A POSITA would combine the teachings of Hagiwara’s embodiments because Hagiwara explicitly taught that its sensor could be adapted for different analytes by incorporating the appropriate enzyme layer. The motivation was to modify the base sensor of Fig. 1(A) to expand its functionality beyond oxygen sensing to other clinically relevant analytes, a purpose expressly described in the reference.
  • Expectation of Success (for §103 grounds): A POSITA would have a high expectation of success, as the combination was a simple addition of a known element (an enzyme layer) to an existing sensor for its intended purpose, as guided by Hagiwara's own disclosure.

Ground 3: Obviousness of Claims 1-19 over Wilson in view of Hagiwara

• Prior Art Relied Upon: Wilson (Patent 5,165,407) and Hagiwara.

• Core Argument for this Ground:

  • Prior Art Mapping: This ground was presented as an alternative to the anticipation argument. Petitioner argued that while Wilson teaches all the structural elements and a dip-coating process, Hagiwara provides a clearer illustration of the physical result of dip-coating a membrane across a sensor window, confirming that the layers would surround the dielectric nubs.
  • Motivation to Combine (for §103 grounds): If Wilson's description of dip-coating was found insufficient, a POSITA would look to analogous art like Hagiwara to implement the technique. Hagiwara and Wilson both describe side-window wire sensors and dip-coating. A POSITA would combine Wilson’s sensor structure with Hagiwara’s clear teaching on dip-coating effects to achieve a predictably coated, manufacturable sensor, as dip-coating was a known, scalable method superior to lab-scale techniques.
  • Key Aspects: This argument leveraged Hagiwara to cure any perceived deficiency in Wilson's disclosure regarding the "surrounding" limitation, arguing it was an obvious design choice to use a well-documented manufacturing process from analogous art.

• Additional Grounds: Petitioner asserted additional obviousness challenges based on Wilson in view of Ryan (The Analyst, November 1997) and a combination of Wilson, Ryan, and Hagiwara. These grounds relied on similar theories, using Ryan to further support the common knowledge and application of dip-coating techniques for creating enzyme layers on wire sensors.

4. Key Claim Construction Positions

• "Nub": This term was central to the petition. Petitioner argued that the Board should adopt the construction advanced by the Patent Owner in parallel district court litigation: "protruding structures." This broad construction is critical because it encompasses the remaining portions of an insulation layer after a cavity is cut, as shown in Wilson and Hagiwara, and is not limited to the distinct "annular plates" depicted as the preferred embodiment in the ’574 patent.
• "Surrounding said at least two nubs... at least along said cavity": Petitioner argued, based on the Patent Owner's litigation positions, that this phrase should be interpreted to mean "encircle at least a portion of the nubs." The petition contended that a standard dip-coating process, as taught by the prior art, would result in an enzyme layer that cross-sectionally encircles the dielectric nubs and the underlying wire, thereby meeting this limitation.

5. Relief Requested

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