DCT
1:25-cv-01202
Pfizer Inc v. Prinston Pharmaceutical Inc
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Pfizer Inc. and related entities (Delaware, Netherlands, Puerto Rico)
- Defendant: Prinston Pharmaceutical Inc. (Delaware)
- Plaintiff’s Counsel: Morris, Nichols, Arsht & Tunnell LLP; Arnold & Porter Kaye Scholer LLP; DLA Piper LLP (US)
- Case Identification: 1:25-cv-01202, D. Del., 09/26/2025
- Venue Allegations: Plaintiff alleges venue is proper in Delaware based on Defendant's incorporation in the state, its commission of a tortious act of patent infringement leading to foreseeable harm in Delaware, and its intent to market and distribute the accused product in Delaware upon FDA approval.
- Core Dispute: Plaintiff alleges that Defendant’s filing of an Abbreviated New Drug Application (ANDA) to market a generic version of Plaintiff's Xeljanz® (tofacitinib) 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 that function as Janus kinase (JAK) inhibitors, used as immunosuppressive agents to treat various autoimmune diseases like rheumatoid arthritis.
- Key Procedural History: The action was initiated under the Hatch-Waxman Act following Defendant’s ANDA filing and Paragraph IV certification. The patent-in-suit is a reissue of U.S. Patent No. 6,627,754. The U.S. Patent and Trademark Office previously extended the patent's expiration date.
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. Patent No. RE41,783 (the patent-in-suit) Issued |
| 2016-12-14 | USPTO Issues Notice Extending RE'783 Patent Expiration Date |
| 2025-07-18 | Date of Prinston's Notice Letter Regarding ANDA Filing |
| 2025-07-22 | Approximate Date Pfizer Received Prinston's Notice Letter |
| 2025-09-26 | Complaint Filing Date |
| 2025-12-08 | Current Expiration Date of the RE'783 Patent |
| 2026-06-08 | Xeljanz NDA Exclusivity Expiration Date |
II. Technology and Patent(s)-in-Suit Analysis
- Patent Identification: U.S. Reissue Patent No. RE41,783, "Pyrrolo[2,3-d]pyrimidine Compounds," issued September 28, 2010.
U.S. Reissue Patent No. RE41,783 - Pyrrolo[2,3-d]pyrimidine Compounds
The Invention Explained
- Problem Addressed: The patent describes a need for effective immunosuppressive agents to treat autoimmune diseases (e.g., rheumatoid arthritis, psoriasis) and prevent organ transplant rejection (RE’783 Patent, col. 1:11-23). The background section identifies the Janus Kinase 3 (JAK3) signaling pathway, which is critical for lymphocyte maturation and function, as a novel therapeutic target for immunosuppression (RE’783 Patent, col. 1:26-42).
- The Patented Solution: The invention provides a class of chemical compounds, specifically pyrrolo[2,3-d]pyrimidines, that inhibit the activity of protein kinases such as JAK3 (RE’783 Patent, Abstract). By blocking the JAK3 signaling pathway, these compounds are intended to modulate immune activity and thereby treat T-cell proliferative disorders and autoimmune diseases (RE’783 Patent, col. 1:36-42).
- Technical Importance: This approach provided a targeted mechanism for immunosuppression by focusing on the JAK3 enzyme, which is expressed primarily in hematopoietic cells, suggesting the possibility of a more specific therapeutic effect compared to broader immunosuppressants (RE’783 Patent, col. 1:26-30).
Key Claims at a Glance
- The complaint asserts infringement of at least Claim 4 (Compl. ¶32).
- Claim 4, as reissued, is an independent claim directed to a specific compound or its salt:
- 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.
III. The Accused Instrumentality
Product Identification
- "Prinston Generic 10 mg Tofacitinib Tablets" (Compl. ¶2).
Functionality and Market Context
- The accused product is a proposed generic version of Pfizer's Xeljanz® tablets (Compl. ¶2, ¶26). The complaint alleges the product contains "tofacitinib citrate in an amount equivalent to 10 mg of tofacitinib base" (Compl. ¶14).
- Functionally, tofacitinib citrate is identified as an inhibitor of Janus kinases indicated for the treatment of various autoimmune conditions, including rheumatoid arthritis, psoriatic arthritis, and ulcerative colitis (Compl. ¶16).
- The complaint alleges that Defendant submitted its ANDA seeking FDA approval to commercially manufacture, use, and sell this product in the United States prior to the expiration of the RE’783 Patent (Compl. ¶2, ¶28).
No probative visual evidence provided in complaint.
IV. Analysis of Infringement Allegations
| 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 Defendant's proposed product contains tofacitinib citrate. The chemical name provided for tofacitinib base matches the compound structure recited in the claim. | ¶15, ¶27, ¶32 | col. 24:26-30 |
Identified Points of Contention
- Identity Question: The central infringement question is one of chemical identity. The complaint alleges that Prinston's proposed generic product contains the precise chemical compound, tofacitinib (as a citrate salt), that is recited in Claim 4. In ANDA litigation, where the generic product is intended to be a bioequivalent copy of the branded drug, disputes over non-infringement are less common than disputes over patent validity.
- Scope Question: A potential, though likely secondary, issue is whether the term "pharmaceutically acceptable salt thereof" covers the citrate salt form allegedly used in Prinston’s product. The complaint proceeds on the basis that it does (Compl. ¶14-15).
V. Key Claim Terms for Construction
The asserted claim is directed to a specific chemical compound, which typically leaves little room for claim construction disputes. However, one phrase may be relevant.
- The Term: "pharmaceutically acceptable salt thereof"
- Context and Importance: The infringement allegation is predicated on Prinston's proposed "Tofacitinib Citrate Tablets" (Compl. ¶27) falling within the scope of Claim 4. The definition of this term is therefore critical to determining whether the citrate salt version of the compound is covered by the claim.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The patent specification provides a non-exhaustive list of acids that can be used to form such salts, stating that they include "citrate, acid citrate, tartrate," among many others (RE’783 Patent, col. 4:6-8). This language may be cited to support the view that a citrate salt was expressly contemplated by the inventors.
- Evidence for a Narrower Interpretation: The complaint and the patent-in-suit do not, on their face, provide explicit evidence that would support a narrower interpretation excluding citrate salts. Any such argument would likely have to rely on extrinsic evidence or prosecution history, which is not detailed in the complaint.
VI. Other Allegations
Indirect Infringement
- The complaint does not contain separate counts for indirect infringement. The prayer for relief includes a request to enjoin Defendant from "inducing or contributing to any of the foregoing" infringing acts (Compl., Prayer for Relief ¶C). However, the complaint does not provide sufficient detail for analysis of the factual basis for knowledge or specific intent to induce.
Willful Infringement
- The complaint alleges that "Prinston had knowledge of the RE’783 patent when it submitted ANDA No. 209923 to the FDA" (Compl. ¶33). This knowledge is predicated on the patent's listing in the FDA's Orange Book (Compl. ¶18) and the statutory requirement for Defendant to provide a Paragraph IV certification against that patent (Compl. ¶29). The complaint also seeks a judgment that the case is exceptional under 35 U.S.C. § 285 (Compl., Prayer for Relief ¶D).
VII. Analyst’s Conclusion: Key Questions for the Case
- A core issue will be one of chemical identity: does the active pharmaceutical ingredient in Prinston’s proposed generic product, tofacitinib citrate, constitute the specific chemical entity defined in Claim 4, which recites the tofacitinib base compound "or a pharmaceutically acceptable salt thereof"?
- The dispositive question in the case will likely be one of patent validity. While the infringement allegation appears straightforward for a generic copy, Prinston’s Paragraph IV certification asserts that the RE'783 patent is "invalid, unenforceable and/or not infringed" (Compl. ¶29). The resolution of the case will therefore likely depend on the court's determination of the validity of Claim 4 in light of prior art or other invalidity challenges raised by the defendant.