Pfizer Inc v. Chugai Pharmaceutical Co Ltd

1. Case Identification

• Case #: IPR2017-01357
• Patent #: 7,332,289
• Filed: May 19, 2017
• Petitioner(s): Pfizer, Inc.
• Patent Owner(s): Chugai Pharmaceutical Co., Ltd.
• Challenged Claims: 1-8 and 13

2. Patent Overview

• Title: Method of Purifying Protein
• Brief Description: The ’289 patent discloses a four-step method for removing contaminant DNA from an antibody-containing sample. The method involves applying the sample to Protein A or G affinity chromatography, eluting the antibody with a low-conductivity acidic solution, neutralizing the eluate to form particles, and removing the particles to purify the sample.

3. Grounds for Unpatentability

Ground I: Anticipation of Claims 1-8 and 13 under 35 U.S.C. §102(b)

• Prior Art Relied Upon: Shadle (International Publication No. WO 95/22389).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Example IA in Shadle, which describes a process for purifying a humanized monoclonal antibody, expressly or inherently discloses every limitation of the challenged claims.
    • Step 1 (Affinity Chromatography): Shadle explicitly taught applying an antibody-containing medium to a "ProSep A affinity column," directly meeting this limitation.
    • Step 2 (Elution): Shadle disclosed eluting the antibody using a "25 mM citrate, pH 3.5" buffer. Petitioner asserted this meets the claim limitation of an "acidic aqueous solution of low conductivity having a molarity of 100 mM or less," as the pH is acidic and the 25 mM molarity is well below the 100 mM threshold. This mapping is supported by Petitioner’s proposed construction of "molarity."
    • Step 3 (Neutralization): Shadle taught adjusting the eluate to pH 5.5 by adding a Tris buffer. This pH falls within the claimed 4-8 range. While Shadle did not explicitly state the final molarity, Petitioner calculated it to be approximately 47.2 mM, which is inherently less than the claimed 100 mM limit. Petitioner also argued that particle formation is an inherent result of these neutralization conditions, a fact confirmed by the ’289 patent’s own specification, which states that neutralizing to a neutral pH "produces particles."
    • Step 4 (Removing Particles): Shadle explicitly disclosed filtering the neutralized sample through 0.1 and 0.2 micron filters. Petitioner contended that these filters would inevitably and necessarily remove the particles inherently formed in the previous step, thereby removing contaminant DNA.
  • Key Aspects: The core of the anticipation argument rested on the assertion that key parameters, specifically the molarity of the neutralized eluate and the formation of particles, were inherently present in the Shadle process even if not explicitly stated. Petitioner supported this by referencing calculations based on Shadle's disclosures and statements from the ’289 patent itself.

Ground II: Obviousness of Claims 1-8 and 13 under 35 U.S.C. §103

• Prior Art Relied Upon: Shadle (International Publication No. WO 95/22389).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner presented this ground as an alternative to anticipation, arguing that even if Shadle did not inherently disclose every limitation, it rendered all challenged claims obvious. The petition asserted that Shadle disclosed an antibody purification process that falls squarely within the scope of the claims and that no patentable difference existed between the prior art process and the claimed invention.
  • Motivation to Combine (for §103 grounds): As a single-reference obviousness challenge, the motivation was to apply the well-known, sequential purification steps disclosed in Shadle for their intended purpose: purifying an antibody and removing contaminants like DNA. A person of ordinary skill in the art (POSA), following Shadle’s teachings, would perform the steps of affinity chromatography, elution, neutralization, and filtration to achieve the predictable result of a purified antibody product with reduced DNA contamination.
  • Expectation of Success: A POSA would have had a reasonable expectation of success in carrying out the purification process of Shadle. Each step involved standard, well-understood laboratory techniques for protein purification, and combining them as taught in Shadle would be expected to yield a purified antibody, which is precisely the result Shadle described.

4. Key Claim Construction Positions

• "molarity": Petitioner argued that the claim term "molarity," particularly in the context of the "acidic aqueous solution" for elution, should be construed based on its plain and ordinary meaning: a measure of the concentration of the solute (e.g., citrate) within the solution. Crucially, Petitioner contended this construction should not include contributions from the antibody protein or contaminant DNA itself. This construction was vital for the argument that Shadle's 25 mM citrate buffer met the "100 mM or less" limitation, as adding the molarity of the protein or DNA could potentially exceed the claimed limit. Petitioner asserted this construction was consistent with the specification, which defines the acidic solution in terms of its own properties (pH, ionic strength, conductivity) without reference to the sample being purified.

5. Relief Requested

• Petitioner requested that the Board institute an inter partes review and cancel claims 1-8 and 13 of the ’289 patent as unpatentable under 35 U.S.C. §§ 102(b) and/or 103(a).