Ajinomoto Co Inc v. Abtis Co Ltd

1. Case Identification

• Case #: IPR2025-00283
• Patent #: 11,896,675
• Filed: December 24, 2024
• Petitioner(s): Ajinomoto Co., Inc.
• Patent Owner(s): Abtis Co., Ltd.
• Challenged Claims: 1-13

2. Patent Overview

• Title: Site-Specific Antibody Conjugation and Antibody-Drug Conjugate as Specific Embodiment Thereof
• Brief Description: The ’675 patent relates to methods for creating modified antibodies for use in antibody-drug conjugates (ADCs). The invention specifically involves modifying a lysine residue at position 248 of an antibody's heavy chain to include a terminal bio-orthogonal click chemistry functional group.

3. Grounds for Unpatentability

Ground 1: Anticipation Over ’959 Publication - Claims 1-13 are anticipated by the ’959 Publication.

• Prior Art Relied Upon: The ’959 Publication (CA 3132959A1).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that the ’675 patent is not entitled to its claimed priority date because its priority applications fail to provide adequate written description for a negative limitation in claim 1. This break in the priority chain renders the ’959 Publication—a Canadian application from the same patent family published before the ’675 patent’s effective filing date—as invalidating prior art under 35 U.S.C. §102. Petitioner contended that the ’959 Publication’s specification is essentially identical to that of the ’675 patent and discloses every element of claims 1-13, including examples of modifying trastuzumab at position 248 with a bio-orthogonal click-chemistry functional group (e.g., norbornene).

Ground 2: Anticipation Over PepTalk Poster - Claims 1, 4, and 8-10 are anticipated by the PepTalk Poster.

• Prior Art Relied Upon: PepTalk Poster (a 2019 poster presentation by Yamada et al.).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner asserted that the PepTalk Poster, which describes its AJICAP™ technology for preparing ADCs, was publicly disseminated before the patent's priority date and qualifies as a printed publication. The poster explicitly disclosed the site-specific conjugation of an antibody (trastuzumab, a human IgG1) at lysine 248. It showed the attachment of bio-orthogonal click-chemistry functional groups, such as azide, and depicted a final structure with two modified heavy chains. This disclosure was argued to meet every limitation of independent claim 1 and dependent claims 4, 8, 9, and 10.

Ground 3: Obviousness Over PepTalk Poster, Yamada, and Matsuda - Claims 1-13 are obvious over the PepTalk Poster in view of Yamada and Matsuda.

• Prior Art Relied Upon: PepTalk Poster, Yamada (WO 2018/199337), and Matsuda (WO 2019/240288).

• Core Argument for this Ground:

  • Prior Art Mapping: Petitioner argued that to the extent the PepTalk Poster does not explicitly disclose certain structures recited in the dependent claims (e.g., claims 2, 3, 5-7, 11), these structures were well-known in the art and disclosed by Yamada and Matsuda. Specifically, Yamada taught various linker structures, including those with heteroatoms and specific alkylene chains that fall within the scope of claims 5-7 and 11. Matsuda provided further examples of modified lysines with different linkers (e.g., C6 cycloalkylene), demonstrating that the specific linkers claimed were merely known options for ADC design.
  • Motivation to Combine: A POSITA would combine the site-specific conjugation platform of the PepTalk Poster with the known linker chemistries from Yamada and Matsuda to optimize ADC properties. This represented the mere substitution of one known element (a linker) for another to yield a predictable result.
  • Expectation of Success: A POSITA would have had a reasonable expectation of success, as the references all operate in the same field of site-specific ADC modification and demonstrate that various linkers and functional groups could be predictably attached to antibodies.

• Additional Grounds: Petitioner asserted additional challenges, including the anticipation of claims 1, 4, and 8-10 by the PepTalk Presentation (a luncheon presentation containing similar information to the Poster); obviousness over the PepTalk Presentation in view of Yamada and Matsuda; anticipation of claims 1, 4, and 8-10 by Yamada alone; and obviousness over Yamada in view of Matsuda.

4. Key Claim Construction Positions

• "antibody": Petitioner argued this term should be construed broadly as defined in the patent's specification to encompass any immunoglobulin molecule or fragment thereof, including recombinant, fusion, and chimeric proteins, not limited to a specific type like IgG.
• "terminal": Based on its use in the specification and its ordinary meaning, Petitioner contended that "terminal" should be construed to mean the last or final group at one end of a chemical structure. This construction is critical to interpreting the negative limitation of claim 1, which excludes certain terminal bio-reactive functional groups.

5. Key Technical Contentions (Beyond Claim Construction)

• Lack of Written Description and Broken Priority Chain: A central contention underlying several grounds is that the ’675 patent is not entitled to its claimed priority date of March 8, 2019. Petitioner argued the priority applications lack written description support for the negative limitation of claim 1 ("wherein the modified lysine residue does not comprise a terminal bio-reactive functional group selected from..."). Because the priority documents are allegedly silent on excluding this specific subgenus of functional groups, the limitation was arbitrarily added, breaking the priority chain and establishing an effective filing date of January 16, 2023.

6. Arguments Regarding Discretionary Denial

• Petitioner argued that the petition should not be denied under §325(d). The primary references, PepTalk Poster, PepTalk Presentation, and Matsuda, were never presented to or considered by the USPTO during prosecution. Although Yamada was of record, Petitioner contended the examiner materially misinterpreted its disclosure, incorrectly concluding that it did not teach the negative limitation of claim 1. This alleged error led to the improper allowance of the claims.

7. Relief Requested

• Petitioner requests institution of an inter partes review and cancellation of claims 1-13 of the ’675 patent as unpatentable.