Pfizer, Inc. v. Chugai Pharmaceutical Co. Ltd.

1. Case Identification

• Case #: IPR2017-01358
• Patent #: Patent 7,927,815
• Filed: May 19, 2017
• Petitioner(s): Pfizer, Inc.
• Patent Owner(s): Chugai Pharmaceutical Co., Ltd.
• Challenged Claims: 1-7 and 12-13

2. Patent Overview

• Title: Protein Purification Method
• Brief Description: The ’815 patent discloses methods for removing DNA contaminants from a sample containing a physiologically active protein. The method comprises a three-step process: (1) converting the sample into an acidic aqueous solution with low conductivity and low molarity; (2) adjusting the pH to a near-neutral level to form particles; and (3) removing the particles to recover the purified protein.

3. Grounds for Unpatentability

Ground 1: Claims 1-7 and 12-13 are anticipated under 35 U.S.C. §102(b) by WO '389

• Prior Art Relied Upon: Shadle (International Publication No. WO 95/22389), referred to as WO ’389.
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that every limitation of the challenged claims is either expressly or inherently disclosed in a single purification process described in Example IA of WO ’389.
    • Step 1 (Acidic, Low-Conductivity Solution): Independent claims 1 and 13 require converting a protein sample into an acidic solution with a conductivity of ≤300 mS/m, a molarity of ≤100 mM, and a pH of 1.5 to 3.9. Petitioner asserted that Example IA of WO ’389 meets these limitations by eluting an antibody from a Protein A column using a buffer of "25 mM citrate, pH 3.5." The pH (3.5) and molarity (25 mM) are expressly within the claimed ranges. Petitioner contended, supported by expert declaration and experimental data, that this buffer composition inherently possesses a conductivity well below the 300 mS/m limit.
    • Step 2 (pH Adjustment & Particle Formation): The claims require adjusting the pH to 4-8, resulting in a sample molarity of ≤100 mM, to form particles. Petitioner argued WO ’389 discloses adjusting the eluate pH to 5.5 (within the 4-8 range) by adding a Tris buffer. Based on calculations, Petitioner asserted the resulting molarity of the adjusted sample is approximately 47.2 mM, which is less than the 100 mM limit. Petitioner contended that particle formation is an inherent and inevitable result of these claimed conditions, a fact confirmed by the ’815 patent’s own specification.
    • Step 3 (Removing Particles): The claims require removing the formed particles. WO ’389 explicitly discloses filtering the pH-adjusted sample through 0.1 and 0.2 micron filters. Petitioner argued this step expressly meets the claim limitation and would inherently remove the particles formed in the previous step, thereby removing contaminant DNA.
    • Dependent Claims: Petitioner mapped the limitations of dependent claims 2-7 and 12 to the WO '389 disclosure. For example, the 25 mM molarity of the WO '389 buffer anticipates claim 2 (≤50 mM), its use of citrate anticipates claim 4 (citric acid), and its explicit use of filtration anticipates claim 12.

Ground 2: Claims 1-7 and 12-13 are obvious under 35 U.S.C. §103 over WO '389

• Prior Art Relied Upon: Shadle (WO 95/22389).
• Core Argument for this Ground:
  • Prior Art Mapping: As an alternative to anticipation, Petitioner argued that even if not every limitation is explicitly or inherently disclosed, WO ’389 renders the claims obvious. The petition contended that the antibody purification process of WO '389's Example IA falls squarely within the scope of the challenged claims, disclosing all essential process steps and conditions.
  • Motivation to Combine: This is a single-reference obviousness challenge. Petitioner argued that because WO '389 discloses each of the claimed process steps, performing a known process (protein purification) using known techniques (pH adjustment, filtration) to achieve a predictable result (purified protein) is obvious. A person of ordinary skill in the art (POSA) would have been motivated to filter the solution after pH adjustment, as taught by WO '389, to remove any particulates or aggregates to protect subsequent chromatography columns, a standard practice in the field.
  • Expectation of Success: A POSA would have had a reasonable expectation of success that the 0.1 and 0.2 micron filters disclosed in WO '389 would function as intended to remove any particles formed during the process. The combination of familiar elements according to known methods would yield predictable results.

4. Key Claim Construction Positions

• Petitioner argued for the broadest reasonable construction of key claim terms, asserting they should be given their plain and ordinary meaning in light of the specification.
• A central contention focused on the terms "molarity," "conductivity," and "ionic strength." Petitioner argued these terms should be construed to refer only to the properties of the aqueous solution (i.e., the buffers and acids) used in the purification steps, without including contributions from the physiologically active protein or the contaminant DNA present in the sample.
• This construction was asserted to be critical, as it ensures the parameters disclosed in the prior art (e.g., 25 mM citrate buffer) fall within the claimed ranges. Petitioner supported this position by noting the ’815 patent specification defines the "acidic aqueous solution" in terms of its component acids and buffers, without mentioning protein or DNA concentrations. Further support was drawn from the patent owner’s own arguments during the prosecution of a European counterpart, where it allegedly argued that molarity calculations should relate to the components of the aqueous solution.

5. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1-7 and 12-13 of Patent 7,927,815 as unpatentable under 35 U.S.C. §102(b) and/or §103.