Pfizer Inc v. Chugai Pharmaceutical Co Ltd

1. Case Identification

• Case #: IPR2017-01358
• 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 a three-step method for removing contaminant DNA from a sample containing a physiologically active protein. The method involves converting the sample into an acidic, low-conductivity solution; adjusting the pH to form particles containing the DNA; and then removing those particles.

3. Grounds for Unpatentability

Ground 1: Anticipation over Shadle - Claims 1-7 and 12-13 are anticipated under 35 U.S.C. § 102(b) over Shadle.

• Prior Art Relied Upon: Shadle (International Publication No. WO 95/22389, hereafter “WO ’389”).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Example IA in WO ’389, which details the purification of a humanized antibody, expressly or inherently discloses every limitation of the challenged claims. For independent claim 1, Petitioner mapped the three-step process:
    • Step 1 (Acidic Conversion): WO ’389 described eluting an antibody from a Protein A column using a “25 mM citrate, pH 3.5” buffer. Petitioner asserted this explicitly met the claimed molarity limit (100 mM or less) and pH range (1.5 to 3.9). Based on expert testing that replicated the buffer, Petitioner argued the conductivity was inherently below the claimed limit of 300 mS/m.
    • Step 2 (pH Adjustment): WO ’389 disclosed adjusting the eluate pH to 5.5 by adding Tris base. This pH is within the claimed 4 to 8 range. Petitioner calculated the resulting solution molarity to be approximately 47.2 mM, which is inherently less than the claimed 100 mM limit. Petitioner contended that particle formation is an inherent and inevitable result of performing this pH and molarity adjustment, a fact supported by the ’815 patent’s own specification.
    • Step 3 (Particle Removal): WO ’389 explicitly disclosed filtering the pH-adjusted sample through 0.1 and 0.2 micron filters. Petitioner argued these filters would inherently remove the particles formed in the previous step, thereby removing contaminant DNA.
  • Key Aspects: The argument relied heavily on calculations and experimental data to show that the molarity and conductivity limitations, while not all explicitly stated in WO ’389, were necessarily and inherently present in the disclosed process.

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

• Prior Art Relied Upon: Shadle (WO ’389).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that, in the alternative to anticipation, WO ’389 rendered the challenged claims obvious. WO ’389 disclosed an antibody purification process that addressed the same problem—removing contaminants like DNA—using nearly identical steps. A person of ordinary skill in the art (POSA) would have understood from WO ’389’s teachings that converting an antibody sample into an acidic, low conductivity solution, followed by pH neutralization and filtration, was a known method for purification.
  • Motivation to Combine (for §103 grounds): This ground was based on a single reference. The motivation presented was for a POSA to perform the final filtration step as taught in WO ’389. A POSA would understand that particles and aggregates often form during pH adjustments in protein purification. They would have been motivated to remove these particles to protect downstream equipment, such as chromatography columns, from fouling, which was a well-known and standard practice.
  • Expectation of Success (for §103 grounds): A POSA would have had a reasonable expectation of success because using filters to remove particulates was a routine and predictable purification step. The process disclosed in WO ’389 used familiar techniques that would predictably yield a purified protein with reduced DNA contamination, as explicitly stated in the reference.

4. Key Claim Construction Positions

• Petitioner argued for the plain and ordinary meaning of the claim terms “molarity,” “conductivity,” and “ionic strength.”
• Critically, Petitioner contended that these terms, under the broadest reasonable construction, referred only to the properties of the aqueous solution (i.e., the buffers and other solutes) used in the process. The construction explicitly excluded any contributions from the physiologically active protein or the contaminant DNA itself when determining whether the claimed numerical ranges were met. Petitioner argued this construction was supported by the patent’s specification and admissions made by the Patent Owner during prosecution of a European counterpart application.

5. Relief Requested

• Petitioner requested institution of an inter partes review and cancellation of claims 1-7 and 12-13 of the ’815 patent as unpatentable.