DCT

1:25-cv-00565

Pfizer Inc v. Alkem Laboratories Ltd

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:25-cv-00565, D. Del., 05/07/2025
  • Venue Allegations: Venue is alleged to be proper because the Defendant is a foreign corporation, which may be sued in any judicial district.
  • Core Dispute: Plaintiff alleges that Defendant’s filing of an Abbreviated New Drug Application (ANDA) to market generic versions of Pfizer's Xeljanz® XR tablets constitutes an act of infringement of a patent covering the active pharmaceutical ingredient.
  • Technical Context: The technology concerns pyrrolo[2,3-d]pyrimidine compounds, which function as Janus kinase (JAK) inhibitors for the treatment of various autoimmune diseases, including rheumatoid arthritis.
  • Key Procedural History: This action was triggered by Defendant's submission of ANDA No. 220395 with a Paragraph IV certification, alleging that the patent-in-suit is invalid, unenforceable, and/or not infringed. The asserted patent, RE41,783, is a reissue of U.S. Patent No. 6,627,754 and is listed in the FDA's "Orange Book" for Pfizer's Xeljanz® XR product. The USPTO previously extended the patent's expiration date.

Case Timeline

Date Event
1999-12-10 RE'783 Patent Priority Date (Provisional App. No. 60/170,179)
2003-09-30 Original U.S. Patent No. 6,627,754 Issued
2010-09-28 U.S. Reissued Patent No. RE41,783 Issued
2016-12-14 USPTO Issues Notice extending RE'783 patent expiration
2025-03-21 Date of Alkem's Notice Letter regarding its ANDA filing
2025-05-07 Complaint Filed

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

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

  • Patent Identification: U.S. Reissued Patent No. RE41,783, "Pyrrolo[2,3-d]pyrimidine Compounds," issued September 28, 2010 (RE'783 Patent). (Compl. ¶22).

The Invention Explained

  • Problem Addressed: The patent addresses the need for effective immunosuppressive agents to treat a range of conditions, including organ transplant rejection and autoimmune diseases such as rheumatoid arthritis and psoriasis (RE'783 Patent, col. 5:12-23). The background notes that the Janus Kinase 3 (JAK3) enzyme is an attractive therapeutic target because its expression is largely limited to hematopoietic (blood-forming) cells, suggesting that its inhibition could provide targeted immunosuppression (RE'783 Patent, col. 5:26-30).
  • The Patented Solution: The invention provides a class of chemical compounds based on a pyrrolo[2,3-d]pyrimidine core structure that are designed to inhibit protein kinases, particularly JAK3 (RE'783 Patent, Abstract; col. 5:12-16). By blocking signaling through the JAK3 pathway, these compounds are intended to modulate the immune system's activity, thereby treating the underlying causes of various T-cell proliferative and autoimmune disorders (RE'783 Patent, col. 5:35-42).
  • Technical Importance: The invention's focus on JAK3 represented an effort to develop a more specific mechanism for immunosuppression, potentially leading to therapies with fewer side effects than less targeted agents (RE'783 Patent, col. 5:35-42).
  • Analogy (Optional): The JAK3 pathway acts like a specific communication channel used by immune cells. The patented compounds are designed to act like a selective jammer for this channel, disrupting the signals that lead to an unwanted immune response without interfering with other essential cellular communications.

Key Claims at a Glance

  • The complaint asserts infringement of at least Claim 4 (Compl. ¶¶ 36, 39).
  • Independent Claim 4, as modified by patent reissue, recites a specific chemical compound:
    • The compound "3-{4-Methyl-3-[methyl-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-amino]-piperidin-1-yl}-3-oxo-propionitrile", which is the molecule known as tofacitinib (RE'783 Patent, col. 24:26-30).
    • Or a pharmaceutically acceptable salt thereof (RE'783 Patent, col. 24:26-30).
  • The complaint does not explicitly reserve the right to assert other claims, but its allegation of infringement of "at least claim 4" preserves this option.

III. The Accused Instrumentality

Product Identification

  • "Alkem Generic Tofacitinib XR Tablets," which are proposed generic copies of Pfizer's Xeljanz® XR in 11 mg and 22 mg extended-release formulations (Compl. ¶2).

Functionality and Market Context

  • The accused instrumentality is a proposed generic drug product for which Alkem seeks FDA approval via ANDA No. 220395 (Compl. ¶2). The basis of an ANDA filing is that the proposed generic product is bioequivalent to an existing, approved brand-name drug (Compl. ¶2).
  • Alkem's Notice Letter describes the product as "Tofacitinib Citrate Tablets, Extended Release Eq 11 mg base and 22 mg base," indicating the active pharmaceutical ingredient is tofacitinib citrate (Compl. ¶29).
  • The statutory act of infringement alleged is the filing of the ANDA itself, which seeks approval to market the generic drug before the expiration of the RE'783 patent (Compl. ¶36).

IV. Analysis of Infringement Allegations

No probative visual evidence provided in complaint.

  • Claim Chart Summary: The infringement allegation centers on the chemical identity of the active ingredient in Alkem's proposed product.
Claim Element (from Independent Claim 4) Alleged Infringing Functionality Complaint Citation Patent Citation
"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 alleges that Alkem's filing of ANDA No. 220395 seeks approval to market and sell generic tablets whose active ingredient is tofacitinib citrate, which is a pharmaceutically acceptable salt of the claimed compound. ¶¶ 2, 29, 38 col. 24:26-30
  • Identified Points of Contention:
    • Scope Questions: The complaint states that Alkem's Paragraph IV certification did not include a non-infringement argument, suggesting Alkem may not contest that its product falls within the literal scope of Claim 4 (Compl. ¶33). The primary dispute in the case is therefore expected to concern patent validity rather than infringement.
    • Technical Questions: A foundational question is whether the "tofacitinib citrate" in Alkem's proposed product is a "pharmaceutically acceptable salt" of the compound recited in Claim 4. The patent specification explicitly lists "citrate" and "acid citrate" as anions that can form such salts, which may support a finding of literal infringement (RE'783 Patent, col. 6:7).

V. Key Claim Terms for Construction

  • The Term: "pharmaceutically acceptable salt thereof"

  • Context and Importance: The construction of this term is central to the infringement analysis, as Alkem's proposed product contains tofacitinib in its citrate salt form (Compl. ¶29). The case for literal infringement depends on "tofacitinib citrate" qualifying as a "pharmaceutically acceptable salt" of the base compound claimed in Claim 4.

  • Intrinsic Evidence for Interpretation:

    • Evidence for a Broader Interpretation: The patent specification provides a non-exclusive list of anions suitable for forming such salts, stating they are "those which form non-toxic acid addition salts, i.e., salts containing pharmacologically acceptable anions, such as the hydrochloride... citrate, acid citrate..." (RE'783 Patent, col. 6:3-7). This language provides direct, explicit support for construing the term to include the citrate salt found in the accused product.
    • Evidence for a Narrower Interpretation: The complaint and the attached patent do not provide information that would support a narrower interpretation of this term. An argument for a narrower scope would likely need to rely on extrinsic evidence or a disclaimer made during patent prosecution, neither of which is referenced in the complaint.

VI. Other Allegations

  • Indirect Infringement: The complaint does not contain separate counts for indirect infringement. However, the prayer for relief requests an injunction against "inducing or contributing to any of the foregoing" infringing activities, preserving the ability to pursue these theories (Compl., Prayer for Relief ¶C).
  • Willful Infringement: The complaint does not contain an explicit allegation of willful infringement or a request for enhanced damages. It does allege that Alkem had "knowledge of the RE’783 patent when it submitted ANDA No. 220395" (Compl. ¶37). The prayer for relief also requests that the court find the case "exceptional" under 35 U.S.C. § 285, which would entitle Pfizer to an award of attorneys' fees (Compl., Prayer for Relief ¶D).

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

  • A core issue will be one of patent validity: The complaint indicates that Alkem's defense will center on its allegation that the RE'783 patent is "invalid, unenforceable, and/or not infringed," with a specific focus on invalidity, as no non-infringement argument was reportedly made (Compl. ¶¶ 31-33). The case will likely turn on whether Alkem can meet its burden of proving by clear and convincing evidence that Claim 4 is invalid on grounds such as obviousness or lack of adequate written description.

  • A key, though likely secondary, question is one of chemical identity: Does the tofacitinib citrate in Alkem's proposed generic product fall within the literal scope of Claim 4? Given the RE'783 patent’s explicit disclosure of "citrate" as a pharmaceutically acceptable salt, this issue may not be heavily contested, shifting the focus of the litigation almost entirely to the patent's validity.