Pfizer v. Alkem Laboratories: Xeljanz Tofacitinib Suit Dismissed Without Prejudice
Pfizer filed a patent infringement action against Alkem Laboratories in Delaware asserting reissue patent USRE041783E covering tofacitinib — the active ingredient in Xeljanz. The case was voluntarily dismissed without prejudice just 64 days after filing, before Alkem served any answer or dispositive motion.
Pfizer’s Xeljanz ANDA suit ends at the starting blocks
On 30 December 2024, Pfizer Inc. — together with co-plaintiffs C.P. Pharmaceuticals International C.V., PF PRISM C.V., PBG Puerto Rico LLC, and PF PRISM IMB B.V. — filed suit in the District of Delaware against Alkem Laboratories Ltd., an Indian generic pharmaceutical manufacturer. The complaint asserted infringement of reissue patent USRE041783E, which covers tofacitinib, the JAK inhibitor sold under Pfizer’s Xeljanz brand in 5 mg and 10 mg tablet formulations. The action was triggered by Alkem’s ANDA filing seeking approval to market a generic tofacitinib tablet in the United States.
Just 64 days after filing, on 4 March 2025, Pfizer filed a Notice of Dismissal under Federal Rule of Civil Procedure 41(a)(1)(A)(i), dismissing all claims without prejudice. Critically, Alkem had not yet served an answer or a motion for summary judgment at the time of dismissal. This procedural posture meant Pfizer could file the notice unilaterally — without court approval or Alkem’s consent — and the dismissal carries no res judicata effect, leaving the door open for Pfizer to re-file the same claims.
A dismissal of this speed and timing — before any substantive briefing — typically signals a commercial or regulatory development outside the courtroom, such as an agreement in principle, a licensing arrangement, a consent judgment negotiation, or a strategic recalibration. The public record is silent on the precise driver. What is clear is that the 30-month FDA stay under Hatch-Waxman may have been a key tactical consideration, and Pfizer’s ability to re-file preserves its enforcement leverage over USRE041783E.
Filing to Dismissed without Prejudice in 64 days
64 days — resolved before defendant filed any responsive pleading
Dismissed without prejudice: what Rule 41(a)(1)(A)(i) means for both parties
Rule 41(a)(1)(A)(i) allows unilateral dismissal before any answer
Because Alkem had not yet served an answer or summary judgment motion, Pfizer could file a Notice of Dismissal unilaterally — no court order or defendant consent required. The dismissal is automatic upon filing. This is one of the few moments in litigation where the plaintiff holds complete procedural control, and Pfizer exercised it with precision before any substantive record was created.
No court order requiredWithout prejudice preserves Pfizer’s right to re-file
A dismissal without prejudice does not adjudicate the merits. Pfizer retains the right to bring the same patent infringement claims against Alkem again. This contrasts sharply with a dismissal with prejudice, which would bar re-filing. The public record here expressly states ‘without prejudice,’ so there is no ambiguity — Pfizer’s enforcement rights under USRE041783E remain intact against Alkem’s generic product.
Merits not adjudicatedAlkem faces no judgment — but uncertainty remains
Alkem escapes this action without any adverse ruling, and no infringement finding has been made. However, because the dismissal is without prejudice, Alkem cannot treat the case closure as a green light for market entry. Pfizer could re-file under USRE041783E at any time before the patent expires. Alkem’s ANDA pathway and any Hatch-Waxman launch strategy should account for this residual litigation risk.
No preclusion for AlkemOff-patent negotiations or settlement likely in progress
The speed of dismissal — 64 days, before any pleadings exchange — is consistent with parties reaching an out-of-court arrangement shortly after filing. Common scenarios include a consent judgment, licensing deal, or agreed launch date. Neither party has made a public disclosure. For the broader tofacitinib generic landscape, the outcome suggests Pfizer continues to actively manage USRE041783E enforcement and may be pursuing individualised settlements with each ANDA filer.
Likely off-court resolutionFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | Pfizer, Inc. | Company | Global biopharmaceutical company — holder of USRE041783E (tofacitinib / Xeljanz)Search in Eureka ↗ |
| Defendant | Alkem Laboratories, Ltd. | Company | Indian generic pharmaceutical manufacturer seeking US approval for generic tofacitinib tabletsSearch in Eureka ↗ |
| Plaintiff counsel | Megan Elizabeth Dellinger | Attorney | Counsel for Pfizer, Inc.Search in Eureka ↗ |
| Plaintiff law firm | Morris, Nichols, Arsht & Tunnell LLP | Law Firm | Representing Pfizer, Inc.Search in Eureka ↗ |
| Presiding judge | Judge Colm F. Connolly | Judge | Delaware District CourtSearch in Eureka ↗ |
Official order — verbatim text
The Notice of Dismissal invokes Rule 41(a)(1)(A)(i) and expressly confirms Alkem had not served an answer or summary judgment motion — the two procedural prerequisites for unilateral dismissal. The ‘without prejudice’ designation is legally significant: no claim preclusion attaches, meaning Pfizer’s infringement allegations under USRE041783E survive and can be re-asserted. The phrasing does not indicate any agreed terms, payment, or admission by either party, leaving the commercial rationale entirely outside the public record.
USRE041783E — tofacitinib JAK inhibitor, Xeljanz 5 mg & 10 mg tablets
USRE041783E is a US reissue patent — a regranted patent issued by the USPTO to correct errors or refine the claim scope of an original patent. The underlying application number US12/577790 places its origins in the late 2000s, consistent with the development timeline of tofacitinib, a first-in-class Janus kinase (JAK) inhibitor. The patent covers tofacitinib, the active pharmaceutical ingredient in Pfizer’s Xeljanz, approved for rheumatoid arthritis, psoriatic arthritis, and ulcerative colitis in 5 mg and 10 mg oral tablet formulations.
Reissue patents carry strategic weight in pharmaceutical enforcement because the reissuance process can produce claims that differ materially from the original grant — potentially broadening or clarifying scope in ways that affect generic design-around strategies. For ANDA filers in the tofacitinib space, USRE041783E represents a key patent to analyse in any Paragraph IV certification strategy. Pfizer’s willingness to file suit on this patent against an Indian generic manufacturer underscores its centrality to Xeljanz’s commercial exclusivity defence in the US market.
Should you run an FTO against USRE041783E before launching generic tofacitinib?
Any pharmaceutical company with a pending ANDA referencing tofacitinib tablets — or any R&D team developing JAK inhibitor formulations that could overlap with Xeljanz’s composition or dosing claims — should treat USRE041783E as a priority FTO target. The reissue status means claim language may differ from the original patent, and a standard prior art search alone is insufficient. Formulation scientists, regulatory teams, and IP counsel should align on the full reissue claim scope before finalising ANDA strategy or launch timelines.
PatSnap Eureka’s FTO Search Agent can map the full claim landscape of USRE041783E against your product specifications, flag reissue-specific claim amendments, and surface related Pfizer continuation or divisional filings that may extend coverage beyond the core compound. Eureka also tracks live litigation status across all ANDA filers asserting tofacitinib patents, enabling your team to benchmark Pfizer’s enforcement posture and identify any consent judgments that may signal negotiated market entry precedents.
Run a freedom-to-operate analysis on USRE041783E to assess your product’s exposure
Run FTO in Eureka →Similar JAK inhibitor ANDA patent cases in US District Courts
Related tofacitinib and JAK inhibitor ANDA infringement actions filed in Delaware and other US district courts against generic pharmaceutical manufacturers.
What this case signals for the JAK inhibitor generic IP landscape
Pfizer’s swift voluntary dismissal without prejudice is a tactical move, not a concession — and it carries clear implications for ANDA filers and generic manufacturers in the JAK inhibitor space.
USRE041783E remains a live enforcement risk for all tofacitinib ANDA filers
Dismissal without prejudice means Pfizer can — and historically does — re-file against the same generic challenger. Any company with a pending or approved ANDA referencing tofacitinib should treat USRE041783E as an active patent threat and conduct ongoing FTO monitoring, not assume the case closure represents a cleared path to market.
Pre-answer dismissals in Hatch-Waxman cases typically signal a deal, not a defeat
When a branded pharma plaintiff voluntarily dismisses a Hatch-Waxman suit within weeks of filing — before any answer — the litigation record typically reflects a settlement, licensing agreement, or negotiated launch date. IP teams tracking Pfizer’s enforcement posture on Xeljanz should monitor for subsequent consent judgments or ANDA approval notices that may reveal the underlying terms.
Pfizer v Alkem — key questions answered
Pfizer filed a voluntary Notice of Dismissal under Rule 41(a)(1)(A)(i) before Alkem served any answer or summary judgment motion. The dismissal is without prejudice, meaning Pfizer retains the right to re-file. The public record does not disclose the commercial reason, but pre-answer dismissals in Hatch-Waxman cases are commonly associated with out-of-court agreements, licensing arrangements, or negotiated launch dates.
USRE041783E is a US reissue patent covering tofacitinib, the active ingredient in Pfizer’s Xeljanz (5 mg and 10 mg tablets). Reissue patents are regranted by the USPTO and may carry amended claim scope compared to the original grant. This patent is a key asset in Pfizer’s exclusivity defence for Xeljanz against generic ANDA filers seeking US market approval.
Not necessarily. A dismissal without prejudice carries no preclusive effect — Pfizer can re-file the same infringement claims under USRE041783E at any time before patent expiry. Alkem’s ANDA approval status and any applicable 30-month stay under Hatch-Waxman remain independent considerations. Alkem should not treat this case closure as a cleared path to market without independent legal analysis.
Rule 41(a)(1)(A)(i) of the Federal Rules of Civil Procedure allows a plaintiff to dismiss an action without a court order by filing a notice of dismissal, provided the defendant has not yet served an answer or a motion for summary judgment. In this case, Alkem had not yet responded, giving Pfizer the unilateral right to exit the litigation. The rule’s availability before any substantive proceedings is why such dismissals often reflect off-record commercial developments rather than merits concessions.
The plaintiffs include Pfizer Inc., C.P. Pharmaceuticals International C.V., PF PRISM C.V., PBG Puerto Rico LLC, and PF PRISM IMB B.V. — entities spanning the US, Netherlands, and Puerto Rico. This multi-entity structure is common in global pharmaceutical IP portfolios and typically reflects a distributed ownership or licensing structure for the patent. It can affect which entities hold standing to sue and who can grant licences, and is worth mapping for any party seeking to challenge or licence USRE041783E.
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