PTAB

IPR2016-01680

Dexcom Inc v. AgaMatrix Inc

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Key Events
Petition

1. Case Identification

2. Patent Overview

  • Title: Compound Material Analyte Sensor
  • Brief Description: The ’433 patent describes an implantable analyte sensor, such as for detecting blood glucose, constructed with a two-layer design. The sensor uses a structurally flexible core made of a strong, inexpensive metal, which is covered by a layer of an electrochemically active noble metal.

3. Grounds for Unpatentability

Ground 1: Anticipation over Hagiwara - Claims 1-3, 6, and 9-11 are anticipated by Hagiwara under 35 U.S.C. §102.

  • Prior Art Relied Upon: Hagiwara (Japanese Application # S57-110236).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued Hagiwara disclosed every limitation of the challenged claims. Hagiwara described a flexible polarography sensor for insertion into a blood vessel. Although Hagiwara’s Fig. 1(B) showed a solid precious metal wire, it expressly taught that a base metal wire with a precious metal plating could be used as a substitute. This combination of teachings disclosed a “structurally flexible core” (the base metal wire) covered by a “layer of electrochemically active metal” (the precious metal plating). Furthermore, Hagiwara disclosed that features from its various embodiments, including the enzyme layer shown in Fig. 1(D), were interchangeable. A POSITA would understand that the enzyme layer from Fig. 1(D) could be applied to the plated wire embodiment, thereby meeting the limitation of a surrounding “membrane system comprising an enzyme.”
    • Key Aspects: The core of the anticipation argument relied on Hagiwara’s explicit teaching that its different sensor configurations were interchangeable, allowing the combination of a plated-wire construction with an enzyme membrane layer from different figures within the same reference.

Ground 2: Obviousness over Wilson and Rosenblatt - Claims 1-3, 5, 6, and 9-11 are obvious over Wilson in view of Rosenblatt.

  • Prior Art Relied Upon: Wilson (a 1992 journal article, "Progress toward the Development of an Implantable Sensor for Glucose") and Rosenblatt (Patent 2,719,797).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner asserted Wilson disclosed a flexible, implantable glucose sensor made from a platinum-iridium wire, which met most claim limitations but not the specific two-part, plated-core structure. Rosenblatt addressed the high cost of solid platinum-group metals in electrodes by teaching a process for coating a less expensive, inert base metal like tantalum with a thin layer of platinum. The combination of Wilson and Rosenblatt yielded the claimed invention: a sensor with a structurally flexible tantalum core (per Rosenblatt) covered by a continuous layer of electrochemically active platinum, surrounded by the enzyme and membrane layers taught by Wilson.
    • Motivation to Combine: A POSITA would combine these references to reduce the cost of the sensor in Wilson. Rosenblatt directly addressed the problem of expensive platinum electrodes and provided a solution—a platinum-coated tantalum core—that was a well-known, cost-effective substitute. This represented a simple substitution of one known material for another to achieve a predictable result (a cheaper, effective sensor).
    • Expectation of Success: The combination involved applying a known coating technique (Rosenblatt) to a known sensor design (Wilson) to solve a known problem (high cost). A POSITA would have had a high expectation of success, as plated electrodes were well-known in the art long before the ’433 patent’s priority date.

Ground 3: Obviousness over Gross and Gross PCT - Claims 1-3, 6, 9-11, 14, and 15 are obvious over Gross in view of Gross PCT.

  • Prior Art Relied Upon: Gross (Patent 6,275,717) and Gross PCT (WO 96/14026).

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner argued Gross disclosed a sensor needle with a stainless steel core (shaft 111) covered by a coating of platinum black (layer 112) with an embedded glucose oxidase enzyme. This met the limitations of a flexible core with an electrochemically active layer. While Gross taught embedding the enzyme directly into the platinum layer, Gross PCT (explicitly incorporated by reference into Gross) disclosed an alternative design where a separate glucose oxidase enzyme layer (27) surrounded the sensor needle. The combination therefore disclosed the claimed structure.
    • Motivation to Combine: The motivation was exceptionally strong, as Gross PCT was written by the same inventors as Gross and was explicitly incorporated by reference, directing a POSITA to its teachings. Using a separate enzyme layer as taught in Gross PCT, rather than an embedded enzyme as taught in Gross, was presented as a simple design choice between two known, functional alternatives for constructing a glucose sensor.
    • Expectation of Success: As both references described working glucose sensors and Gross explicitly directed the reader to Gross PCT, a POSITA would have reasonably expected that applying the separate enzyme layer configuration from Gross PCT to the stainless steel sensor of Gross would result in a functional and predictable device.

  • Additional Grounds: Petitioner asserted additional obviousness challenges, including combinations of Hagiwara with Rosenblatt (to teach a tantalum core) and Hagiwara with Heller (to teach a polyimide insulating layer), based on similar substitution and combination rationales.

4. Key Claim Construction Positions

  • "Structurally Flexible": Petitioner proposed this term be construed to mean "capable of being bent or flexed." This construction was argued to be consistent with the patent’s specification, which listed tantalum and nitinol as examples of flexible materials. Petitioner contended this construction was critical because prior art references like Gross used materials such as stainless steel for the sensor core, which, at the small diameters used in the art, would be considered "structurally flexible" under this plain-meaning construction.

5. Key Technical Contentions (Beyond Claim Construction)

  • Flexibility of Stainless Steel: To support the argument that the stainless steel core in Gross was "structurally flexible," Petitioner submitted experimental evidence. The experiment, detailed in an expert declaration, demonstrated that a stainless steel wire with a diameter (305 microns) comparable to that disclosed in Gross could undergo significant, reversible flexure under a small load. This evidence was intended to show that a POSITA would have considered the stainless steel sensor core in Gross to be flexible, thereby meeting the claim limitation.

6. Relief Requested

  • Petitioner requested the institution of an inter partes review (IPR) and the cancellation of claims 1-3, 5, 6, 8-11, 14, and 15 of the ’433 patent as unpatentable.