DCT

1:25-cv-00617

Pfizer Inc v. Somerset Therap LLC

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Key Events
Complaint

I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:25-cv-00617, D. Del., 05/16/2025
  • Venue Allegations: Venue is alleged to be proper in Delaware based on Defendant's incorporation in the state and its anticipated future marketing, distribution, and sales activities within the district upon FDA approval.
  • Core Dispute: Plaintiff alleges that Defendant’s filing of an Abbreviated New Drug Application (ANDA) to market a generic version of the drug Xeljanz® constitutes an act of patent infringement.
  • Technical Context: The technology concerns a specific pyrrolo[2,3-d]pyrimidine compound, tofacitinib, which functions as a Janus Kinase (JAK) inhibitor for the treatment of various autoimmune diseases.
  • Key Procedural History: This action was initiated under the Hatch-Waxman Act following Defendant's submission of ANDA No. 220137 with a Paragraph IV certification, alleging that Plaintiff's patent is invalid, unenforceable, or will not be infringed. The patent-in-suit, RE41,783, is a reissue of U.S. Patent No. 6,627,754 and is listed in the FDA's "Orange Book" for Xeljanz®. The patent's expiration date has been extended by the USPTO to December 8, 2025.

Case Timeline

Date Event
1999-12-10 RE'783 Patent Priority Date
2003-09-30 Original U.S. Patent No. 6,627,754 Issued
2010-09-28 U.S. Reissue Patent No. RE41,783 Issued
2016-12-14 USPTO determination extending patent term to Dec. 8, 2025
2025-04-03 Date of Somerset's ANDA Notice Letter
2025-05-16 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 identifies a need for effective immunosuppressive agents to treat a range of conditions, including organ transplant rejection and autoimmune diseases like rheumatoid arthritis and psoriasis, where modulating immune system activity would be desirable (RE'783 Patent, col. 1:12-24). The invention focuses on inhibiting protein kinases, and specifically targets the Janus Kinase 3 (JAK3) enzyme (RE'783 Patent, col. 1:12-16).
  • The Patented Solution: The patent discloses a class of chemical compounds, known as pyrrolo[2,3-d]pyrimidines, that are described as inhibitors of JAK3 (RE'783 Patent, col. 1:12-16). The specification explains that because JAK3 expression is primarily limited to hematopoietic (blood-forming) cells and is essential for lymphocyte maturation and function, blocking its signaling pathway is a targeted way to achieve immunosuppression (RE'783 Patent, col. 1:25-42).
  • Technical Importance: This approach provided a specific molecular target (JAK3) for developing treatments for T-cell proliferative disorders, offering a distinct mechanism of action for modulating the immune response (RE'783 Patent, col. 1:39-42).

Key Claims at a Glance

  • The complaint asserts at least dependent claim 4 (Compl. ¶34). Claim 4 depends from claim 3, which in turn depends from independent claim 1.
  • Claim 4 recites a 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's phrasing "at least claim 4" suggests it may assert additional claims later in the litigation (Compl. ¶34).

III. The Accused Instrumentality

Product Identification

  • "Somerset Generic Tofacitinib Tablets" proposed in ANDA No. 220137 (Compl. ¶¶2, 26).

Functionality and Market Context

  • The accused products are generic versions of Pfizer's Xeljanz® tablets, containing tofacitinib citrate in 5 mg and 10 mg dosages for twice-daily administration (Compl. ¶¶2, 14, 27).
  • The active ingredient, tofacitinib, is an inhibitor of Janus kinases, indicated for the treatment of conditions such as rheumatoid arthritis, psoriatic arthritis, and ulcerative colitis (Compl. ¶16).
  • The act of infringement alleged is statutory, arising from Somerset's filing of an ANDA seeking FDA approval to market and sell these tablets prior to the expiration of the RE'783 patent (Compl. ¶34). The complaint alleges that Somerset's own notice letter states an intent to "engage in the commercial manufacture, use or sale" of the tablets before the patent expires (Compl. ¶28).

IV. Analysis of Infringement Allegations

No probative visual evidence provided in complaint.

The complaint alleges that the product Somerset seeks to market is a generic version of Xeljanz®, whose active ingredient is tofacitinib (Compl. ¶¶2, 14). The chemical name for tofacitinib corresponds to the compound identified in asserted claim 4 of the RE'783 patent (Compl. ¶15).

RE'783 Patent Infringement Allegations

Claim Element (from Dependent 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 Somerset’s ANDA seeks approval to market generic tofacitinib tablets. The active ingredient of these tablets is tofacitinib, which corresponds to the chemical structure recited in the claim, or its citrate salt. ¶¶2, 14, 15, 34 col. 24:26-30
  • Identified Points of Contention:
    • Validity vs. Infringement: The complaint states that while Somerset's Paragraph IV certification asserts noninfringement, invalidity, and unenforceability, its accompanying detailed statement "does not contain a noninfringement argument" (Compl. ¶¶29, 31). This suggests that the core of the dispute may not be whether the accused product meets the claim limitations, but rather whether the asserted claim is valid and enforceable.

V. Key Claim Terms for Construction

  • The Term: "pharmaceutically acceptable salt thereof"
  • Context and Importance: This term is critical because Somerset's accused product contains "tofacitinib citrate," which is a salt form of the base compound recited in claim 4 (Compl. ¶14). The infringement analysis depends on the citrate salt falling within the scope of a "pharmaceutically acceptable salt." Practitioners may focus on this term to confirm that the specific formulation of the accused product is covered by the claim language.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The patent specification provides an explicit, non-limiting list of acids that can be used to form such salts, which "include, but are not limited to...the hydrochloride, hydrobromide, hydroiodide, nitrate, sulfate, bisulfate, phosphate, acid phosphate, acetate, lactate, citrate, acid citrate, tartrate..." (RE'783 Patent, col. 4:3-9). This language appears to expressly include the citrate salt form.
    • Evidence for a Narrower Interpretation: The complaint and patent do not appear to provide a basis for a significantly narrower interpretation that would exclude a common salt like citrate. An argument for a narrower construction would need to identify limiting language elsewhere in the specification or prosecution history that is not apparent from the provided documents.

VI. Other Allegations

  • Indirect Infringement: The complaint does not contain a formal count for indirect infringement. The primary allegations are for direct infringement under 35 U.S.C. § 271(a) and the statutory act of infringement under § 271(e)(2)(A) for filing the ANDA (Compl. ¶¶34, 36). However, the prayer for relief requests an injunction against "inducing or contributing to any of the foregoing" (Compl., Prayer for Relief C).
  • Willful Infringement: The complaint does not use the word "willful." It does allege that Somerset had "knowledge of the RE'783 patent when it submitted ANDA No. 220137 to the FDA," a predicate for willfulness (Compl. ¶35). Furthermore, the prayer for relief seeks a judgment that this is an "exceptional case" 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 central question will be one of patent validity. As the complaint suggests Somerset has not advanced a non-infringement position for its generic tofacitinib product, the case will likely depend on whether Somerset can prove by clear and convincing evidence that claim 4 of the RE’783 patent is invalid or unenforceable, as it asserted in its Paragraph IV certification.
  • A key procedural question will be whether Somerset's actions in filing its ANDA, allegedly with pre-suit knowledge of the patent, are sufficient to deem this an exceptional case under 35 U.S.C. § 285. The resolution of this issue will determine whether the prevailing party may recover its attorneys' fees.