Charles River Laboratories Inc v. Seikagaku Corp

1. Case Identification

• Case #: IPR2025-00440
• Patent #: 11,236,318
• Filed: January 16, 2025
• Petitioner(s): Charles River Laboratories, Inc.
• Patent Owner(s): Seikagaku Corporation
• Challenged Claims: 21

2. Patent Overview

• Title: Recombinantly-Produced Factor C Proteins for Endotoxin Detection
• Brief Description: The ’318 patent relates to recombinantly-produced Factor C proteins from the Limulus polyphemus species of horseshoe crab. These enzymes are used for detecting harmful bacterial endotoxins in medical products and are defined by a functional characteristic of "residual activity" in the presence of certain inhibitory ions.

3. Grounds for Unpatentability

Ground 1: Obviousness over Mizumura and the ’498 PCT - Claim 21 is obvious over Mizumura in view of the ’498 PCT.

• Prior Art Relied Upon: Mizumura (Application # 2015/0307864) and the ’498 PCT (WO 2018/074498).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Mizumura, which is the publication of the ’318 patent’s own priority application, taught all elements of claim 21 except for the specific gene and amino acid sequence for Factor C from the Limulus polyphemus species. Mizumura’s examples focused on Factor C from the Tachypleus tridentatus species but disclosed its recombinant production in HEK293 cells and its resulting "residual activity" falling within the claimed ranges. The ’498 PCT, published by the same Patent Owner, supplied the missing element by disclosing the first successful sequencing and functional recombinant production of Limulus polyphemus Factor C.
  • Motivation to Combine: A POSITA would combine Mizumura's methods with the sequence information from the ’498 PCT. The field was actively seeking to replace natively-sourced Factor C from Limulus polyphemus (used in the standard LAL test) with a more reliable recombinant version to overcome known limitations. Mizumura demonstrated a successful method for a related species, and the ’498 PCT provided the specific sequence needed to apply that method to the commercially important Limulus polyphemus species.
  • Expectation of Success: A POSITA would have a reasonable expectation of success because the ’498 PCT explicitly described the successful expression of functional Limulus polyphemus Factor C. Further, the ’318 patent’s lead inventor testified in a related prosecution that a POSITA would expect similar functional properties between the different horseshoe crab species once the specific sequence was known.

Ground 2: Obviousness over Mizumura and McClymont - Claim 21 is obvious over Mizumura in view of McClymont.

• Prior Art Relied Upon: Mizumura (Application # 2015/0307864) and McClymont (a 2017 Ph.D. thesis).
• Core Argument for this Ground:
  • Prior Art Mapping: This ground presented an argument parallel to Ground 1. Petitioner asserted Mizumura provided the foundational teachings for producing recombinant Factor C in HEK293 cells with the claimed functional activity. The McClymont thesis served as an alternative reference to the ’498 PCT, independently disclosing the full gene coding and amino acid sequence for Limulus polyphemus Factor C.
  • Motivation to Combine: The motivation was identical to that in Ground 1. A POSITA would have been driven to use the newly available sequence information from McClymont to create a recombinant version of the well-established Limulus polyphemus Factor C, applying the proven methods disclosed in Mizumura.
  • Expectation of Success: A POSITA would have reasonably expected success for the same reasons as in Ground 1. With the specific genetic blueprint from McClymont and a detailed production method from Mizumura, creating the claimed protein was a predictable extension of the prior art.

4. Key Technical Contentions (Beyond Claim Construction)

• Invalid Priority Claim: Petitioner’s central technical contention was that the ’318 patent is not entitled to its claimed December 2013 priority date. The argument was based on the assertion that the priority documents failed to meet the written description and enablement requirements of 35 U.S.C. §112 for claim 21.
• Lack of Possession and Enablement: Petitioner argued the priority documents provided no working examples, sequences, or structural details for Factor C from the claimed Limulus polyphemus species. All examples concerned a different species (Tachypleus tridentatus). Because the full sequence of Limulus polyphemus Factor C was unknown and uncharacterized as of the priority date, and its sequencing was later admitted by the inventors to be a significant, non-trivial achievement, the inventors could not have possessed or enabled the full scope of the claimed invention in 2013.
• Consequence: This lack of support allegedly reset the patent’s effective filing date to its actual filing date of April 30, 2019, thus making Mizumura, the ’498 PCT, and McClymont available as prior art under 35 U.S.C. §102.

5. Arguments Regarding Discretionary Denial

• §325(d) Denial Inappropriate: Petitioner argued that discretionary denial would be improper because the petition raises new art and arguments. The prior art references were not considered during prosecution. Petitioner contended the Examiner made a material error by failing to properly analyze the ’318 patent’s claim to priority, which would have revealed the lack of written description support and allowed the intervening prior art to be applied.
• §314(a) Denial Inappropriate: Petitioner stated that there was no co-pending district court litigation involving the ’318 patent, making discretionary denial under Fintiv inapplicable.

6. Relief Requested

• Petitioner requests institution of IPR and cancellation of claim 21 of the ’318 patent as unpatentable.