Pfizer Inc v. Viwit Pharmaceutical Co Ltd

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Pfizer Inc. (Delaware), Pfizer Products Inc. (Connecticut), PF Prism CV. (Netherlands), and C.P. Pharmaceuticals International C.V. (Netherlands)
  • Defendant: Viwit Pharmaceutical Co., Ltd. (China)
  • Plaintiff’s Counsel: Morris, Nichols, Arsht & Tunnell LLP
• Case Identification: Pfizer Inc. et al. v. Viwit Pharmaceutical Co., Ltd., 1:20-cv-00160, D. Del., 01/31/2020
• Venue Allegations: Plaintiff alleges that because Defendant is not resident in the United States, venue is proper in any judicial district.
• Core Dispute: Plaintiff alleges that Defendant’s submission of an Abbreviated New Drug Application (ANDA) to market a generic version of the smoking-cessation drug Chantix® constitutes an act of infringement of three patents covering the active compound, its specific salt forms, and methods of use.
• Technical Context: The technology relates to varenicline, a nicotinic receptor partial agonist, and its tartrate salt forms, which are used in pharmaceutical products for smoking cessation.
• Key Procedural History: The litigation was triggered by Defendant’s filing of ANDA No. 212879 with the FDA, which included a Paragraph IV certification asserting that Plaintiff’s patents are invalid, unenforceable, or will not be infringed by the proposed generic product. This submission is a statutory act of infringement under the Hatch-Waxman Act.

Case Timeline

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

U.S. Patent No. 6,410,550 - "Aryl fused azapolycyclic compounds"

• Issued: June 25, 2002

The Invention Explained

• Problem Addressed: The patent describes a need for novel compounds that bind to neuronal nicotinic acetylcholine receptor sites to modulate cholinergic function, which is useful for treating a wide range of conditions including chemical dependencies such as nicotine addiction (Compl. ¶1; ’550 Patent, col. 1:12-32).
• The Patented Solution: The invention discloses a class of chemical compounds, described as "aryl fused azapolycyclic compounds," having a specific chemical structure (Formula I) that are useful for treating neurological and psychological disorders by binding to these nicotinic receptors (’550 Patent, Abstract; col. 2:5-12). The patent claims the compounds themselves, pharmaceutical compositions containing them, and methods of their use.
• Technical Importance: The invention provided a novel chemical scaffold for targeting nicotinic receptors, offering a new therapeutic pathway for treating conditions associated with cholinergic dysfunction, including addiction (’550 Patent, col. 1:12-16).

Key Claims at a Glance

• The complaint asserts infringement of claims 1 and 8 (Compl. ¶28).
• Independent Claim 1: A compound of Formula I having a specified tetracyclic core structure with various substituent groups (R¹, R², and R³) defined by a Markush group of chemical moieties (’550 Patent, col. 2:5-12, col. 27:51-col. 28:28).
• Dependent Claim 8: A specific compound falling within the scope of Claim 1, namely 5,8,14-Triazatetracyclo[10.3.1.0².¹¹.0⁴.⁹]hexadeca-2(11),3,5,7,9-pentaene, or a pharmaceutically acceptable salt thereof (’550 Patent, col. 28:44-48). This is the chemical name for varenicline.

U.S. Patent No. 6,890,927 - "Tartrate Salts of 5,8,14-Triazatetracyclo[10.3.1.0².¹¹.0⁴.⁹]-Hexadeca-2(11),3,5,7,9-Pentaene and Pharmaceutical Compositions Thereof"

• Issued: May 10, 2005

The Invention Explained

• Problem Addressed: While the base compound varenicline was known, there was a need for a specific salt form with superior properties for pharmaceutical development, such as high solid-state stability and compatibility with formulation excipients, which are critical for creating a viable drug product (’927 Patent, col. 2:23-30).
• The Patented Solution: The invention identifies and characterizes specific tartrate salts of varenicline, particularly the L-tartrate salt. It further discloses distinct anhydrous and hydrated crystalline polymorphs (referred to as Forms A, B, and C) of the L-tartrate salt, which possess unique and advantageous physical properties for formulation and manufacturing (’927 Patent, Abstract; col. 3:36-50).
• Technical Importance: The creation of a stable, manufacturable salt form with predictable physical properties is a crucial step in pharmaceutical development, enabling the consistent and reliable delivery of an active pharmaceutical ingredient to patients (’927 Patent, col. 2:23-30).

Key Claims at a Glance

• The complaint asserts infringement of claims 1-3, 13-15, and 19-26 (Compl. ¶35).
• Independent Claim 1: The L-tartrate salt of 5,8,14-triazatetracyclo[10.3.1.0².¹¹.0⁴.⁹]-hexadeca-2(11),3,5,7,9-pentaene (’927 Patent, col. 52:51-54).
• Independent Claim 13: A pharmaceutical composition comprising a pharmaceutically acceptable carrier and the compound of claim 1 (’927 Patent, col. 53:54-56).
• Independent Claim 19: A method of treatment for nicotine dependency, addiction and withdrawal by administering the compound of claim 1 to a subject in need thereof (’927 Patent, col. 54:13-17).

U.S. Patent No. 7,265,119 - "Tartrate Salts of 5,8,14-Triazatetracyclo[10.3.1.0².¹¹.0⁴.⁹]-Hexadeca-2(11),3,5,7,9-Pentaene and Pharmaceutical Compositions Thereof"

• Issued: September 4, 2007

Technology Synopsis

This patent, related to the ’927 patent, is also directed to specific tartrate salt forms of varenicline. It addresses the same technical problem of identifying a stable, formulatable salt and provides claims directed to specific crystalline polymorphs defined by their characteristic powder X-ray diffraction (PXRD) patterns, which are important for ensuring consistency in a pharmaceutical product (’119 Patent, col. 2:26-34; col. 4:1-17).

Asserted Claims & Accused Features

• Asserted Claims: Claims 4-9, 11-12, and 14-15 (Compl. ¶42). Independent claim 4 claims an anhydrous L-tartrate salt of varenicline characterized by specific PXRD peaks (’119 Patent, col. 32:9-16).
• Accused Features: The complaint alleges that Defendant’s varenicline tartrate ANDA product is covered by one or more claims of the ’119 patent (Compl. ¶39).

III. The Accused Instrumentality

Product Identification

• Defendant’s proposed generic drug, identified as "Viwit's varenicline tartrate tablets, in 0.5mg and 1mg dosages" ("Viwit's ANDA Product") (Compl. ¶21).

Functionality and Market Context

• The accused product is a generic copy of Plaintiff’s Chantix®, a "nicotinic receptor partial agonist indicated for use as an aid to smoking cessation treatment" (Compl. ¶19, ¶21). The act of infringement alleged is statutory, arising from Viwit's submission of ANDA No. 212879 to the FDA seeking approval to manufacture and sell this product in the U.S. prior to the expiration of the patents-in-suit (Compl. ¶21, ¶26). The complaint characterizes Chantix® as a "breakthrough" product, suggesting significant market value for both the branded and generic versions (Compl. ¶1).

No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

The complaint does not provide technical evidence or a detailed infringement theory, such as a claim chart exhibit. Instead, it alleges that in its Notice Letter, Defendant "does not dispute" that its ANDA Product infringes numerous asserted claims.

’550 Patent Infringement Allegations

’927 Patent Infringement Allegations

• Identified Points of Contention:
  • Scope Questions: Because the complaint alleges that infringement of many key claims is "not dispute[d]," a central issue will likely shift from infringement to validity (Compl. ¶22, ¶28, ¶35, ¶42). The case may turn on whether Defendant can prove by clear and convincing evidence that the asserted claims are invalid.
  • Technical Questions: For any claims where infringement is disputed (e.g., claims in the ’119 patent not mentioned as undisputed), a key question will be one of physical characterization: does the specific crystalline form of varenicline tartrate in Defendant's ANDA product meet the PXRD peak limitations recited in those claims?

V. Key Claim Terms for Construction

The complaint does not provide sufficient detail for analysis of most claim terms. However, based on the technology, the following term will likely be critical.

• The Term: "L-tartrate salt" (’927 Patent, Claim 1)
• Context and Importance: The patentability of the invention claimed in the ’927 and ’119 patents hinges on the specific salt form of the underlying varenicline compound. The definition of "L-tartrate salt," particularly whether it is limited to the specific crystalline polymorphs disclosed in the specification, will be central to both infringement and validity analyses. Practitioners may focus on this term because different salt forms and polymorphs can have distinct physical properties and may not be equivalent.
• Intrinsic Evidence for Interpretation:
  • Evidence for a Broader Interpretation: The plain language of independent claim 1 of the ’927 patent recites "The L-tartrate salt" without limitation to a specific crystalline form, which may support a construction covering any form of the L-tartrate salt (’927 Patent, col. 52:51-52).
  • Evidence for a Narrower Interpretation: The specification heavily emphasizes the discovery and characterization of three specific polymorphs (Forms A, B, and C), providing detailed PXRD and other analytical data (’927 Patent, col. 3:36-50, Tables I-VI). A defendant may argue that the claims should be limited to these disclosed and characterized forms, especially in the context of validity arguments regarding what was new and non-obvious over the prior art.

VI. Other Allegations

• Indirect Infringement: The complaint alleges that if Viwit commercializes its ANDA Product, it will induce and contribute to infringement (Compl. ¶27, ¶34, ¶41). This is premised on the product's label instructing users (patients and doctors) on how to use the drug for smoking cessation, which would cause direct infringement of the asserted method of use claims (e.g., ’927 Patent, Claim 19).

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

• A core issue will be one of patent validity: given that infringement of the base compound and its L-tartrate salt form is allegedly "not dispute[d]," the central battleground will likely be Defendant’s attempt to prove, by clear and convincing evidence, that Plaintiff's patent claims are invalid, as asserted in its Paragraph IV certification.
• A key evidentiary question for any disputed polymorph claims will be one of physical identity: does the crystalline form of the varenicline tartrate in Defendant’s ANDA product exhibit the specific powder X-ray diffraction peaks required by claims in the ’927 and ’119 patents, or is there a technical distinction that avoids infringement?