PTAB

PGR2025-00023

Charles River Laboratories Inc v. Seikagaku Corp

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Key Events
Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Methods for Producing and Using Recombinant Endotoxin Assays
  • Brief Description: The ’109 patent relates to methods for producing an endotoxin detection assay by recombinantly generating three proteins—Factor C, Factor B, and Pro-clotting enzyme. These proteins, naturally found in horseshoe crabs, form an enzymatic clotting cascade in the presence of endotoxin.

3. Grounds for Unpatentability

Ground 1: Claims 1-10 Fail to Meet the Written Description Requirement of §112

  • Prior Art Relied Upon: The ’109 patent’s specification and its priority documents (represented by U.S. Patent Application No. 14/650,767, the “’767 application”).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that the challenged claims define a vast genus of methods for producing the endotoxin assay, conservatively estimated to cover at least 3,456 possible combinations of protein sources, expression systems, and recovery methods. However, the specification (via the ’767 application) fails to describe a single species or example falling within the scope of the claimed genus. Specifically, claims 1 and 10 require expressing Factor B and Pro-clotting enzyme in a mammalian host cell, but the specification only describes producing these proteins in an insect cell (Sf9) system, which it explicitly distinguishes from mammalian systems.
    • Key Aspects: The petition asserted that the inventors did not possess the full scope of the claimed invention as of the December 10, 2013, priority date. The specification provides no common structural features that would allow a person of ordinary skill in the art (POSA) to visualize or recognize all members of the claimed genus. Furthermore, it fails to provide any examples using proteins from the Limulus polyphemus species of horseshoe crab, as the genetic and protein sequence information for that species was not known or disclosed at the time.

Ground 2: Claims 1-10 Fail to Meet the Enablement Requirement of §112

  • Prior Art Relied Upon: The ’109 patent’s specification and its priority documents (represented by the ’767 application).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner contended that the specification does not teach a POSA how to make and use the full scope of the claimed invention without undue experimentation. Given the thousands of possible combinations encompassed by the claims and the lack of guidance, a POSA would be forced to undertake a "research assignment" involving extensive trial-and-error to identify functional assay combinations. The specification provides no working examples of producing Factor B and Pro-clotting enzyme in any mammalian cell line, as required by the claims.
    • Key Aspects: The petition highlighted the unpredictable nature of recombinant protein expression and function. The inventors’ own later patent filings admitted the difficulty in characterizing proteins from the Limulus polyphemus species. The complete absence of guidance on how to produce the required proteins in the claimed mammalian systems, or how to combine proteins from different species and host cells, would require a POSA to engage in an extraordinary and undue level of experimentation.

Ground 3: Claims 1-10 are Anticipated by the ’629 Publication under §102

  • Prior Art Relied Upon: ’629 publication (Application # 2019/0241629).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground was presented as an alternative argument: if the Patent Owner asserts the claims are enabled by the specification as filed in 2023 (relying on advancements in the art), then the claims are not entitled to the 2013 priority date and are anticipated by the intervening ’629 publication. Petitioner argued that the ’629 publication, which published in 2019, discloses every limitation of the challenged claims. It explicitly describes a method for producing a three-factor endotoxin assay using recombinant Factor C, Factor B, and Pro-clotting enzyme derived from the Limulus polyphemus species.
    • Key Aspects: The ’629 publication teaches expressing these proteins in a CHO mammalian cell system, obtaining them from the culture supernatant, and combining them to create a functional assay that detects endotoxin. Petitioner provided an element-by-element mapping showing how the ’629 publication discloses all steps and components recited in independent claims 1 and 10, as well as the additional limitations of dependent claims 2-9.

4. Arguments Regarding Discretionary Denial

  • Petitioner argued that discretionary denial under §325(d) would be improper. The §112 written description and enablement arguments were never raised or considered by the Examiner during prosecution. The anticipation ground is also new, as the ’629 publication was never applied against the claims because the Examiner did not challenge the patent’s entitlement to its earliest priority date.
  • Petitioner further asserted there is no co-pending litigation involving the ’109 patent that would warrant discretionary denial under the Fintiv factors.

5. Relief Requested

  • Petitioner requests institution of Post-Grant Review (PGR) and cancellation of claims 1-10 of the ’109 patent as unpatentable.