DCT

1:25-cv-00632

Pfizer Inc v. Macleods Pharma Ltd

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:25-cv-00632, D. Del., 05/21/2025
  • Venue Allegations: Venue is alleged to be proper in the District of Delaware because Defendant is a foreign corporation, which may be sued in any judicial district under 28 U.S.C. § 1391(c)(3). The complaint also alleges that Defendant’s act of filing its Abbreviated New Drug Application (ANDA) will lead to foreseeable harm to Plaintiff in Delaware.
  • Core Dispute: Plaintiff alleges that Defendant’s filing of an ANDA to market a generic version of the drug Xeljanz® (tofacitinib) constitutes an act of infringement of a patent covering the tofacitinib compound itself.
  • Technical Context: The technology concerns a specific small molecule compound, tofacitinib, which functions as a Janus kinase (JAK) inhibitor for the treatment of various autoimmune diseases, including rheumatoid arthritis.
  • Key Procedural History: This action was triggered by Defendant’s filing of ANDA No. 219530 with a "Paragraph IV" certification, asserting that the patent-in-suit is invalid or will not be infringed by its proposed generic product. The patent-in-suit, RE41,783, is a reissue of an earlier patent and is listed in the FDA’s "Orange Book" for Xeljanz®. The complaint notes that Defendant’s notice letter alleges invalidity of all claims but does not present a non-infringement argument.

Case Timeline

Date Event
1999-12-10 Earliest Priority Date for RE’783 Patent
2003-09-30 Issue Date of Original U.S. Patent No. 6,627,754
2010-09-28 Issue Date of Reissue Patent RE41,783
2016-12-14 USPTO issues notice extending RE’783 patent expiration date
2025-04-04 Date of Defendant's Paragraph IV Notice Letter to Plaintiff
2025-04-08 Approximate date Plaintiff received the Notice Letter
2025-05-21 Complaint Filing Date

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

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

The Invention Explained

  • Problem Addressed: The patent describes a need for new immunosuppressive agents to treat a range of conditions, including organ transplant rejection and autoimmune diseases like rheumatoid arthritis and psoriasis (’RE’783 Patent, col. 5:11-23). The background identifies the Janus Kinase 3 (JAK3) signaling pathway as a promising therapeutic target, noting that its expression is limited to hematopoietic (blood-forming) cells, which suggests that inhibiting it could provide a targeted immunomodulatory effect (’RE’783 Patent, col. 5:25-35).
  • The Patented Solution: The invention discloses a class of compounds, known as pyrrolo[2,3-d]pyrimidines, that function as inhibitors of protein kinases, particularly JAK3 (’RE’783 Patent, Abstract; col. 5:11-15). By blocking the JAK3 pathway, these compounds are designed to suppress the immune responses underlying the targeted diseases (’RE’783 Patent, col. 5:35-42).
  • Technical Importance: This approach provided a novel mechanism for immunosuppression by targeting a specific kinase (JAK3) critical for T-cell and B-cell function, offering a potentially more precise method for treating T-cell proliferative disorders than existing, less-targeted therapies (’RE’783 Patent, col. 5:35-42).

Key Claims at a Glance

  • The complaint asserts infringement of at least independent claim 4 (Compl. ¶35).
  • Claim 4 consists of a single element, claiming the specific chemical compound:
    • 3-{4-Methyl-3-[methyl-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-amino]-piperidin-1-yl}-3-oxo-propionitrile, or a pharmaceutically acceptable salt thereof.
  • The complaint does not explicitly reserve the right to assert other claims, but its pleading of infringement of "at least" claim 4 leaves that possibility open.

III. The Accused Instrumentality

Product Identification

  • The accused products are "Macleods Generic Tofacitinib Tablets," which are the subject of ANDA No. 219530 (Compl. ¶2). The product is further described as "Tofacitinib Tablet (Tofacitinib Citrate); Oral Eq 5mg Base and 10mg Base" (Compl. ¶28).

Functionality and Market Context

  • The proposed product is a generic version of Plaintiff's Xeljanz® tablets (Compl. ¶2, ¶27). Its active ingredient, tofacitinib citrate, is an inhibitor of Janus kinases and is intended for the same therapeutic uses as Xeljanz®, such as the treatment of rheumatoid arthritis, psoriatic arthritis, and ulcerative colitis (Compl. ¶15, ¶17). Defendant's filing of the ANDA is the statutorily defined act of infringement that gives rise to this lawsuit under the Hatch-Waxman Act, as it represents a request for FDA approval to market the generic drug before the expiration of the ’RE’783 Patent (Compl. ¶35). No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

The complaint does not contain a claim chart or detailed infringement contentions. Instead, it advances a direct infringement theory based on Defendant's filing of its ANDA under 35 U.S.C. § 271(e)(2). The core of the allegation is that Defendant’s proposed generic product, as described in ANDA No. 219530, contains tofacitinib citrate (Compl. ¶28). The compound tofacitinib is the specific molecule claimed in claim 4 of the ’RE’783 Patent (’RE’783 Patent, col. 24:26-30). Therefore, Plaintiff alleges that the commercial manufacture, use, or sale of Defendant's product would directly infringe claim 4 (Compl. ¶37).

Critically, the complaint alleges that Defendant's Paragraph IV notice letter "alleges that all claims of the RE’783 patent are invalid" but "does not contain a noninfringement argument" (Compl. ¶32). This suggests the central dispute will be over the patent's validity rather than infringement.

  • Identified Points of Contention:
    • Scope Questions: A primary question for the court will be whether there is any viable non-infringement position, notwithstanding its apparent absence from Defendant's initial notice letter. The infringement analysis appears to be a straightforward question of identity: is the active pharmaceutical ingredient in Defendant’s proposed product the same compound recited in claim 4?
    • Technical Questions: The dispute does not appear to raise complex technical questions regarding infringement. The central technical issue is the chemical identity of the compound in Defendant's ANDA product compared to the claimed compound. Given that an ANDA filer must show its product is bioequivalent to the reference drug (Xeljanz®), which contains tofacitinib, a material difference is not anticipated based on the complaint's allegations.

V. Key Claim Terms for Construction

  • The Term: "a pharmaceutically acceptable salt thereof"
  • Context and Importance: This term, appearing at the end of claim 4, is important because Plaintiff's commercial product (Xeljanz®) and Defendant's proposed generic product are both formulated with tofacitinib citrate, a salt form of the base compound (Compl. ¶15, ¶16, ¶28). The construction of this term will determine whether the claim explicitly covers the accused salt form. Practitioners may focus on this term because, while the base compound is identical, infringement hinges on the salt form also falling within the claim's scope.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The patent specification provides a detailed, non-limiting list of acids that can be used to form such salts. This list explicitly includes "citrate" and "acid citrate," providing strong intrinsic evidence that the citrate salt form was contemplated by the inventors and is covered by the claim. (’RE’783 Patent, col. 6:5-11).
    • Evidence for a Narrower Interpretation: The patent's specification does not appear to contain language that would support a narrower construction of this term that excludes the citrate salt. A defendant would face a significant challenge in arguing for a narrower scope in light of the explicit disclosure.

VI. Other Allegations

  • Indirect Infringement: While the formal counts in the complaint allege direct infringement, the prayer for relief seeks to enjoin Defendant from "inducing or contributing to" infringement (Compl. Prayer for Relief ¶C). The complaint alleges facts that could potentially support such a claim, such as the intent for the generic product to be prescribed by physicians and dispensed by pharmacies for use by patients in the United States (Compl. ¶11).
  • Willful Infringement: The complaint does not use the term "willful." However, it alleges that Defendant "had knowledge of the RE’783 patent when it submitted ANDA No. 219530 to the FDA" (Compl. ¶36) and was sent a notice letter regarding the patent (Compl. ¶27). These allegations of pre-suit knowledge could be used to support a future claim for enhanced damages or a finding that this is an "exceptional case" warranting attorneys' fees under 35 U.S.C. § 285, which Plaintiff requests (Compl. Prayer for Relief ¶D).

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

  • A core issue will be one of patent validity: as Defendant has reportedly conceded infringement by omitting non-infringement arguments from its notice letter, the case will likely turn entirely on whether Defendant can prove by clear and convincing evidence that claim 4 of the ’RE’783 patent is invalid on grounds such as anticipation or obviousness.
  • A secondary procedural and legal question will be the basis for an exceptional case finding: should Plaintiff prevail on both validity and infringement, a key question will be whether Defendant’s litigation conduct or the circumstances of its ANDA filing rise to the level of an "exceptional case" that would justify an award of attorneys' fees.