DCT

1:25-cv-00024

Salix Pharma Inc v. Mylan Pharma Inc

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:25-cv-00024, N.D.W. Va., 03/26/2025
  • Venue Allegations: Venue is alleged to be proper in the Northern District of West Virginia because the Defendant is a corporation organized and existing under the laws of West Virginia with its principal place of business in Morgantown, West Virginia, within the district.
  • Core Dispute: Plaintiffs allege that Defendant's Abbreviated New Drug Application ("ANDA") to market a generic version of Plaintiffs' Xifaxan® (rifaximin) tablets infringes three U.S. patents related to specific polymorphic forms and methods of treating Irritable Bowel Syndrome.
  • Technical Context: The dispute centers on rifaximin, a gastrointestinal-specific antibiotic used to treat conditions like Irritable Bowel Syndrome with Diarrhea (IBS-D), a prevalent and chronic disorder.
  • Key Procedural History: The litigation was triggered by a Notice Letter, sent pursuant to the Hatch-Waxman Act, in which Defendant notified Plaintiffs of its ANDA filing and its Paragraph IV certification asserting that the patents-in-suit are invalid, unenforceable, and/or not infringed. The patents are listed in the U.S. Food and Drug Administration's "Orange Book" as covering the branded Xifaxan® product.

Case Timeline

Date Event
2004-05-25 FDA approves NDA for Xifaxan® 200 mg tablets
2005-03-03 ’196 Patent Priority Date
2008-02-26 ’571 and ’912 Patents Priority Date
2010-03-24 FDA approves NDA for Xifaxan® 550 mg tablets
2012-06-05 ’196 Patent Issue Date
2023-01-31 ’912 Patent Issue Date
2023-10-10 ’571 Patent Issue Date
2025-02-11 Defendant sends ANDA Notice Letter to Plaintiffs
2025-03-26 Complaint Filing Date

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

U.S. Patent No. 11,779,571, "Methods for Treating Irritable Bowel Syndrome (IBS)," issued October 10, 2023

The Invention Explained

  • Problem Addressed: The patent background describes the use of rifaximin, a rifamycin class antibiotic, for its broad antibacterial activity in the gastrointestinal tract to treat various localized conditions, including irritable bowel syndrome (IBS) and infectious diarrhea (’571 Patent, col. 1:25-37). The implicit technical problem is identifying specific, effective, and durable treatment regimens for these complex conditions.
  • The Patented Solution: The invention provides methods for treating bowel diseases by administering a rifamycin class antibiotic, like rifaximin, according to a specific dosing schedule to achieve a "durability of antibiotic response" (’571 Patent, col. 2:46-53). This means that after a defined treatment course, patients continue to experience symptom relief, a key goal in managing chronic conditions like IBS. The patent focuses on a regimen of 550 mg of rifaximin administered three times a day (TID) (’571 Patent, col. 2:65-67).
  • Technical Importance: The claimed method aims to provide not just temporary relief but a lasting therapeutic effect from a short course of treatment, which is highly significant for improving the quality of life for patients with chronic gastrointestinal disorders (’571 Patent, col. 13:35-42).

Key Claims at a Glance

  • The complaint asserts "one or more claims" without specification (Compl. ¶30). The first independent claim is Claim 1.
  • Claim 1 Elements:
    • A method of treating bloating associated with diarrhea-predominant irritable bowel syndrome (dIBS)
    • in a female subject
    • said method comprising administering, 550 mg of rifaximin TID for 14 days to the female subject
  • The complaint does not explicitly reserve the right to assert dependent claims.

U.S. Patent No. 11,564,912, "Methods for Treating Irritable Bowel Syndrome (IBS)," issued January 31, 2023

The Invention Explained

  • Problem Addressed: As a related patent, the ’912 Patent addresses the same technical problem: establishing effective treatment protocols for bowel diseases like IBS using rifaximin that provide durable symptom relief (’912 Patent, col. 1:41-54).
  • The Patented Solution: The invention discloses methods for treating IBS symptoms by administering a therapeutically effective amount of rifaximin. Like its related patent, it focuses on achieving a durable response after the treatment period concludes, specifically identifying a 550 mg TID regimen as a solution (’912 Patent, col. 2:46-53; col. 2:65-67). The specification details clinical trial results that underpin these methods (’912 Patent, col. 23:7-24:4).
  • Technical Importance: This patented method provides a specific, clinically-tested protocol that offers a durable therapeutic benefit for IBS, a condition often characterized by relapsing and remitting symptoms.

Key Claims at a Glance

  • The complaint asserts "one or more claims" without specification (Compl. ¶42). The first independent claim is Claim 1.
  • Claim 1 Elements:
    • A method of treating one or more symptoms of irritable bowel syndrome (IBS)
    • in a female subject
    • said method comprising administering, 550 mg of rifaximin TID for 14 days to the female subject
  • The complaint does not explicitly reserve the right to assert dependent claims.

U.S. Patent No. 8,193,196, "Polymorphous Forms of Rifaximin, Processes for their Production and Use thereof in the Medicinal Preparations," issued June 5, 2012

  • Technology Synopsis: This patent addresses the fact that a single drug compound can exist in different crystalline structures, or polymorphs, which can affect its physical properties and bioavailability (’196 Patent, col. 1:47-64). The invention discloses specific polymorphous forms of rifaximin, identified as forms δ and ε, and methods for their production, which allows for the creation of a drug product with predictable and controlled characteristics (’196 Patent, col. 2:2-9).
  • Asserted Claims: The complaint asserts "one or more claims" (Compl. ¶54). The patent contains independent claims 1, 7, 10, 12, 17, and 23, covering both processes and compositions.
  • Accused Features: The accused feature is Defendant's generic rifaximin drug product itself, which Plaintiffs allege is a composition comprising a polymorphic form of rifaximin covered by the ’196 Patent (Compl. ¶53-54).

III. The Accused Instrumentality

  • Product Identification: Defendant's generic rifaximin 550 mg tablets, for which Defendant submitted ANDA No. 219687 to the FDA for approval (the "ANDA Product") (Compl. ¶2).
  • Functionality and Market Context: The ANDA Product is a generic version of Plaintiffs' Xifaxan® 550 mg tablets and seeks approval for the same indications, including the treatment of IBS-D in adults (Compl. ¶1, ¶22). As an ANDA product, it is intended to be a therapeutic equivalent to the branded drug. The filing represents a commercial effort by a generic manufacturer to enter the market for a branded pharmaceutical product prior to the expiration of patents listed in the FDA's Orange Book (Compl. ¶7, ¶19).

No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

The complaint does not contain a claim chart or detailed infringement contentions. The infringement allegations are based on the act of filing the ANDA under 35 U.S.C. § 271(e)(2) and the anticipated commercial manufacture, use, and sale of the ANDA Product upon approval.

  • ’571 Patent Infringement Allegations
Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A method of treating bloating associated with diarrhea-predominant irritable bowel syndrome (dIBS)... Defendant's ANDA seeks approval for its product to be used for the treatment of IBS-D, which includes the symptom of bloating. ¶22, ¶29 col. 2:46-48
...in a female subject... Defendant's ANDA product, upon approval, will be prescribed and administered to human patients, including females, for the treatment of IBS-D. ¶31 col. 46:1-3
...said method comprising administering, 550 mg of rifaximin TID for 14 days to the female subject... Defendant's ANDA Product is a 550 mg tablet of rifaximin, and its proposed labeling will allegedly instruct for administration in a manner that meets the claimed dosing regimen. ¶21, ¶33 col. 2:65-67
  • ’912 Patent Infringement Allegations
Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A method of treating one or more symptoms of irritable bowel syndrome (IBS)... Defendant's ANDA seeks approval for its product to be used for the treatment of IBS-D, which is a form of IBS. ¶22, ¶41 col. 2:46-48
...in a female subject... Defendant's ANDA product, if approved, will be prescribed to human patients, which includes the sub-population of females. ¶43 col. 46:1-3
...said method comprising administering, 550 mg of rifaximin TID for 14 days to the female subject... Defendant's ANDA Product consists of 550 mg rifaximin tablets, and Defendant will allegedly induce infringement through product labeling that instructs for the claimed method of administration. ¶21, ¶45 col. 2:65-67
  • Identified Points of Contention:
    • Scope Questions: A primary question for the method patents (’571 and ’912) will be whether the proposed label for Defendant's ANDA Product will instruct physicians and patients to perform every step of the asserted claims. For example, does the proposed label specifically direct a 14-day course of treatment at a three-times-daily ("TID") dosage for the treatment of IBS-D, and does it do so in a way that specifically encourages its use in the claimed "female subject" population?
    • Technical Questions: For the ’196 Patent, the central dispute will be a factual one of material composition: does Defendant's ANDA Product actually contain the specific crystalline polymorphs of rifaximin (form δ or ε) as claimed? This question cannot be answered from the complaint and will require expert testing and analysis of Defendant's product during discovery.

V. Key Claim Terms for Construction

The complaint does not provide sufficient detail for a definitive analysis of claim construction disputes. However, based on the asserted claims, certain terms may become focal points.

  • The Term: "female subject" (in Claim 1 of both the ’571 and ’912 Patents)
  • Context and Importance: This term sharply limits the scope of the method claims to a specific patient sub-population. The infringement analysis for inducement will depend on whether Defendant's proposed product label specifically instructs or encourages use in females, or if its instructions are for a general adult population. Practitioners may focus on this term as a potential avenue for a non-infringement defense if Defendant's label can be shown not to specifically target female patients.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The complaint does not provide evidence for a broader interpretation. A defendant might argue that while the claim is directed to females, the specification's description of the invention is broader, discussing treatment of bowel diseases generally (’912 Patent, col. 2:41-43), potentially raising questions about the basis for the gender-specific limitation.
    • Evidence for a Narrower Interpretation: The plain language of the claims explicitly recites "in a female subject," which is a clear and unambiguous limitation (’571 Patent, col. 42:43-46; ’912 Patent, col. 46:1-3). Plaintiffs will likely argue that this limitation was intentionally added and is entitled to its full scope, regardless of broader disclosures in the specification.

VI. Other Allegations

  • Indirect Infringement: The core of the complaint rests on indirect infringement. Plaintiffs allege that Defendant will actively induce infringement by marketing its ANDA Product with instructions that will encourage physicians to prescribe and patients to use the drug in accordance with the patented methods (Compl. ¶33, ¶45, ¶57). Contributory infringement is also alleged, based on the assertion that the ANDA product is especially made for an infringing use and is not a staple article of commerce (Compl. ¶34, ¶46, ¶58).
  • Willful Infringement: The complaint does not contain an explicit count for willful infringement. However, it alleges that Defendant was aware of the patents through their listing in the Orange Book and through the Notice Letter (Compl. ¶37, ¶49, ¶61). It further alleges that Defendant's assertions of non-infringement and invalidity "are devoid of an objective good faith basis" and requests that the case be declared "exceptional" for the purpose of awarding attorneys' fees (Compl. ¶24, p. 12, ¶v).

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

  • A central issue will be one of induced infringement: For the ’571 and ’912 method patents, will the specific language of Defendant's proposed product label be found to instruct or encourage physicians and patients to perform all the limitations of the asserted claims, particularly with respect to the dosing regimen and the specified "female subject" population?
  • A key evidentiary question will be one of physical composition: For the ’196 polymorph patent, does Defendant's generic product actually contain the specific crystalline forms of rifaximin claimed in the patent? This will be a purely factual determination based on scientific evidence developed during litigation.
  • A foundational question will be one of claim validity: Can the asserted method claims, which are narrowly defined by patient gender, survive challenges of obviousness? The analysis may turn on whether limiting a known drug treatment to a specific demographic sub-population, without an unexpected result tied to that demographic, is sufficient to render the invention non-obvious over the prior art.