DCT

1:18-cv-00380

Pfizer Inc v. Prinston Pharmaceutical Inc

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:18-cv-00380, D. Del., 03/09/2018
  • Venue Allegations: Venue is alleged to be proper as Defendant is incorporated in the state of Delaware. The complaint also notes that Defendant has not contested venue in a pending, related action.
  • Core Dispute: Plaintiff alleges that Defendant’s filing of an Abbreviated New Drug Application (ANDA) to market a generic version of the rheumatoid arthritis drug Xeljanz® constitutes an act of infringement of a patent covering a class of chemical compounds.
  • Technical Context: The technology relates to pyrrolo[2,3-d]pyrimidine compounds, which function as Janus Kinase (JAK) inhibitors and are used as immunosuppressive agents to treat autoimmune diseases.
  • Key Procedural History: The patent-in-suit is a reissue of an earlier patent. The complaint notes that this lawsuit arises from the same ANDA filing that prompted a prior action between the parties (1:17-cv-00213) involving different patents. The Defendant’s ANDA filing included a “Paragraph IV” certification alleging that the patent-in-suit is invalid or unenforceable and will not be infringed.

Case Timeline

Date Event
1999-12-10 Priority date for U.S. Reissue Patent No. RE41,783
2003-09-30 Issue date of original U.S. Patent No. 6,627,754
2010-09-28 Issue date of U.S. Reissue Patent No. RE41,783
2017-01-16 Date of Defendant’s prior Paragraph IV notice concerning other patents
2018-02-22 Date of Defendant’s notice letter regarding the '783 patent
2018-03-09 Complaint Filing Date

II. Technology and Patent(s)-in-Suit Analysis

U.S. Reissue Patent No. RE41,783 - "Pyrrolo[2,3-d]pyrimidine Compounds"

Issued September 28, 2010.

The Invention Explained

  • Problem Addressed: The patent addresses the need for effective immunosuppressive agents for treating T-cell proliferative disorders, such as organ transplant rejection and autoimmune diseases (e.g., rheumatoid arthritis, psoriasis, lupus). (RE41,783 Patent, col. 5:35-42).
  • The Patented Solution: The invention provides a specific class of chemical compounds based on a pyrrolo[2,3-d]pyrimidine core structure. These compounds are designed to inhibit the Janus Kinase 3 (JAK3) enzyme, which plays a critical role in the signaling pathways that lead to the maturation and function of B and T lymphocytes. By blocking this pathway, the compounds can modulate immune activity. (RE41,783 Patent, Abstract; col. 5:12-15, 5:26-36).
  • Technical Importance: Targeting JAK3 was a novel mechanism for immunosuppression, as JAK3 expression is largely limited to hematopoietic cells, suggesting a more targeted therapeutic effect with potentially fewer side effects than broader immunosuppressants. (RE41,783 Patent, col. 5:26-29).

Key Claims at a Glance

  • The complaint asserts infringement of at least independent claim 1. (Compl. ¶34).
  • Independent Claim 1 claims:
    • A compound of a specific core chemical structure (Formula I) or its pharmaceutically acceptable salt.
    • Wherein substituent "R¹" is a group of the formula "R⁴-(CH₂)y-R⁵".
    • Wherein "R⁵" is a substituted piperidinyl group or another specified chemical group (Formula II).
    • Wherein substituents "R²" and "R³" on the core structure are each hydrogen.
  • The complaint notes that Defendant’s Paragraph IV notice did not present a non-infringement argument for claims 1, 2, and 4, implying these claims are at issue. (Compl. ¶31).

III. The Accused Instrumentality

Product Identification

The accused instrumentalities are "Prinston Generic Tablets," for which Defendant seeks FDA approval via ANDA No. 209923. (Compl. ¶12).

Functionality and Market Context

  • The accused product is a generic version of Pfizer’s Xeljanz® drug. (Compl. ¶2). The active ingredient is tofacitinib citrate in an amount equivalent to 5 mg of tofacitinib base, formulated for twice-daily administration. (Compl. ¶¶18, 27).
  • The active ingredient, tofacitinib citrate, is an inhibitor of Janus kinases (JAKs) indicated for the treatment of moderately to severely active rheumatoid arthritis. (Compl. ¶17). The complaint alleges that upon approval, Defendant intends to commercialize and sell the generic tablets throughout the United States. (Compl. ¶¶13, 32, 36).

IV. Analysis of Infringement Allegations

The complaint alleges that the filing of ANDA No. 209923 is a technical act of infringement under 35 U.S.C. § 271(e)(2)(A), and that the future manufacture and sale of the proposed generic product will constitute direct infringement. (Compl. ¶¶34, 36).

RE41,783 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A compound of the formula I...or a pharmaceutically acceptable salt thereof Defendant’s ANDA No. 209923 seeks approval to market generic tablets containing tofacitinib citrate. Tofacitinib citrate is the citrate salt of tofacitinib. ¶¶2, 27 col. 5:44-48
wherein... R² and R³ are each hydrogen The chemical structure of tofacitinib, the active ingredient in Defendant's proposed product, contains hydrogen atoms at the corresponding R² and R³ positions of the pyrrolo[2,3-d]pyrimidine core. ¶19 col. 6:15-25
wherein R¹ is a group of the formula R⁴-(CH₂)y-R⁵...; wherein R⁵ is a piperidinyl substituted by one to five carboxy, cyano, amino... The complaint alleges that the tofacitinib molecule in Defendant's product contains a substituent group at the R¹ position that meets the definition recited in the claim. The chemical name for tofacitinib includes a substituted piperidine moiety. ¶19 col. 5:49-65

No probative visual evidence provided in complaint.

Identified Points of Contention

  • Scope Questions: A primary question will be whether the specific chemical structure of tofacitinib falls within the scope of independent claim 1. Tofacitinib's structure is "[Core]-NH-CH₃-[Substituted Piperidine]". The plain language of claim 1 defines the substituent "R¹" as "R⁴-(CH₂)y-R⁵" and does not appear to explicitly recite the "methylamino" linker present in the accused compound. The court will need to determine if Pfizer's infringement theory for claim 1 is viable.
  • Technical Questions: While the complaint focuses its infringement count on "at least claim 1," it also references claim 4. (Compl. ¶31). Claim 4, which depends from a group of specific compounds listed in claim 3, explicitly recites the chemical name for tofacitinib ("3-{4-Methyl-3-[methyl-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-amino]-piperidin-1-yl}-3-oxo-propionitrile"). (RE41,783 Patent, col. 24:26-30). This raises the question of whether the case will ultimately focus on the validity of this more specific claim, where infringement appears to be less disputable, rather than the potentially problematic scope of claim 1.

V. Key Claim Terms for Construction

  • The Term: "R¹" (as defined in claim 1)
  • Context and Importance: The definition of the substituent "R¹" is central to the infringement analysis for claim 1. The dispute will likely center on whether the language "R¹ is a group of the formula R⁴-(CH₂)y-R⁵..." can be construed to read on the specific substituent found in tofacitinib, which is attached to the core via a methylamino group. Practitioners may focus on this term because of the apparent structural mismatch between the claim language and the accused compound.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: A party arguing for a broad interpretation might point to the patent's overall disclosure of pyrrolo[2,3-d]pyrimidine compounds as JAK3 inhibitors and argue that one of ordinary skill in the art would understand claim 1 to cover the class of compounds, including exemplified species like tofacitinib, despite any potential ambiguity in the claim's text.
    • Evidence for a Narrower Interpretation: A party arguing for a narrow interpretation would point to the plain language of claim 1, which defines "R¹" with a specific formula that does not explicitly include an amino linker. This party could contrast this with the more specific structure for "R¹" defined in claim 2 ("wherein R¹ is a group of the formula [piperidinyl structure]") and the specific compound named in claims 3 and 4, arguing that the patentee knew how to claim these structures precisely and chose different, more limited language for claim 1. (RE41,783 Patent, col. 22:50-54; col. 24:3-30).

VI. Other Allegations

  • Indirect Infringement: The prayer for relief seeks an injunction against "inducing or contributing to any of the foregoing," which suggests an allegation of indirect infringement. (Compl., Prayer for Relief D). In an ANDA context, this is typically based on the proposed product labeling that would instruct physicians and patients to use the drug in an infringing manner.
  • Willful Infringement: The complaint alleges that Defendant had knowledge of the '783 patent when it submitted its ANDA. (Compl. ¶35). This allegation, combined with the prayer for relief seeking a judgment that the case is "exceptional" under 35 U.S.C. § 285, forms the basis for a potential claim of willful infringement. (Compl., Prayer for Relief D).

VII. Analyst’s Conclusion: Key Questions for the Case

  1. A core issue will be one of claim scope and interpretation: Can the definition of the substituent "R¹" in claim 1, which lacks an explicit amino linker, be construed to cover the tofacitinib molecule, or is there a fatal defect in the claim language that precludes a finding of infringement for that claim?
  2. A second key issue will be strategic focus: Given the potential interpretation challenge with claim 1, the case may ultimately turn not on that claim, but on the question of validity. Defendant has alleged the '783 patent is invalid. (Compl. ¶30). The dispositive battle may therefore be over the validity of the more specific claims (e.g., claims 3 and 4) that explicitly recite the accused tofacitinib compound, making a non-infringement defense for those claims difficult.