DCT

1:24-cv-04607

Salix Pharma Inc v. Amneal Pharma Of New York LLC

Log In
Key Events
Complaint

I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 3:24-cv-04607, D.N.J., 04/05/2024
  • Venue Allegations: Venue is alleged as proper in the District of New Jersey based on Defendants having principal places of business in the district, engaging in regular business contacts there, and having previously consented to venue in prior litigations in the same court.
  • Core Dispute: Plaintiffs allege that Defendants' submission of an Abbreviated New Drug Application (ANDA) to the FDA seeking approval to market a generic version of Plaintiffs’ Xifaxan® (rifaximin) tablets constitutes an act of patent infringement under the Hatch-Waxman Act.
  • Technical Context: The dispute centers on the antibiotic drug rifaximin, including specific crystalline forms (polymorphs) and methods of its use for treating gastrointestinal conditions such as irritable bowel syndrome with diarrhea (IBS-D).
  • Key Procedural History: The lawsuit was initiated in response to a Paragraph IV Notice Letter dated February 27, 2024, in which Defendants asserted that the patents-in-suit are invalid, unenforceable, and/or not infringed by their proposed generic product. The complaint was filed within the statutory 45-day period following receipt of this notice.

Case Timeline

Date Event
2005-03-03 Priority Date for ’196, ’949, ’904, ’968, ’763 Patents
2008-02-26 Priority Date for ’571, ’912, ’384 Patents
2012-06-05 Issue Date for U.S. Patent No. 8,193,196
2013-08-27 Issue Date for U.S. Patent No. 8,518,949
2014-06-03 Issue Date for U.S. Patent No. 8,741,904
2016-03-01 Issue Date for U.S. Patent No. 9,271,968
2019-10-29 Issue Date for U.S. Patent No. 10,456,384
2020-07-07 Issue Date for U.S. Patent No. 10,703,763
2023-01-31 Issue Date for U.S. Patent No. 11,564,912
2023-10-10 Issue Date for U.S. Patent No. 11,779,571
2024-02-27 Defendant's Paragraph IV Notice Letter
2024-04-05 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 complaint does not provide sufficient detail for analysis of the specific claims or technical disclosure of the ’571 Patent. The complaint alleges the patent claims "methods of treating diarrhea-associated irritable bowel syndrome with rifaximin" (Compl. ¶62).

U.S. Patent No. 11,564,912 - Methods for Treating Irritable Bowel Syndrome (IBS)

  • Issued January 31, 2023.

The Invention Explained

  • Problem Addressed: The patent background describes rifaximin as a rifamycin class antibiotic with broad antibacterial activity against gastrointestinal bacteria that cause conditions such as irritable bowel syndrome (IBS) ('912 Patent, col. 1:20-29). The implicit problem is the effective treatment of such conditions.
  • The Patented Solution: The invention provides methods of treating IBS symptoms specifically in female subjects by administering 550 mg of rifaximin three times a day (TID) ('912 Patent, Abstract). The specification describes that such treatment can result in a "durability of response" where subjects experience adequate relief of symptoms even after the treatment course is completed ('912 Patent, col. 2:37-41).
  • Technical Importance: This approach provides a defined treatment regimen for IBS in a specific patient sub-population (females), offering the potential for lasting symptomatic relief from a short course of antibiotic therapy.

Key Claims at a Glance

  • The complaint asserts infringement of one or more claims of the ’912 Patent without specifying which ones (Compl. ¶75). Independent claim 1 is representative of the invention's scope.
  • Essential elements of Independent Claim 1:
    • A method of treating one or more symptoms of irritable bowel syndrome (IBS)
    • in a female subject
    • comprising administering, for between 14 days and 24 months
    • 550 mg of rifaximin TID to the female subject

U.S. Patent No. 10,456,384 - Methods for Treating Irritable Bowel Syndrome (IBS)

  • Issued October 29, 2019.

The Invention Explained

  • Problem Addressed: The technical problem addressed is identical to that of the ’912 Patent: the effective treatment of IBS caused by gastrointestinal bacteria, but with a focus on a different patient demographic ('384 Patent, col. 1:20-29).
  • The Patented Solution: The patented solution is a method for treating IBS in subjects who are 65 years of age or older by administering 550 mg of rifaximin TID ('384 Patent, Abstract). The specification includes clinical data suggesting that older subjects and males were predictors of a positive response to rifaximin treatment ('384 Patent, col. 24:1-6).
  • Technical Importance: The invention identifies a specific patient demographic (older subjects) that may particularly benefit from this treatment regimen, providing targeted therapeutic guidance.

Key Claims at a Glance

  • The complaint asserts infringement of one or more claims of the ’384 Patent without specifying them (Compl. ¶87). Independent claim 1 is representative.
  • Essential elements of Independent Claim 1:
    • A method of treating one or more symptoms of irritable bowel syndrome (IBS)
    • in a subject 65 years of age or older
    • comprising administering, for between 14 days and 24 months
    • 550 mg of rifaximin TID to the subject

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 existence of specific crystalline polymorphic forms of rifaximin, identified as forms δ and ε. The invention recognizes that different polymorphs can have different physical properties, such as systemic absorption, which is critical for a gastrointestinal-targeted antibiotic. The patent claims the specific polymorphous forms themselves, characterized by their powder X-ray diffraction patterns, as well as compositions containing them. (’196 Patent, col. 3:24-44; Fig. 1-2).
  • Asserted Claims: Unspecified in the complaint (Compl. ¶99).
  • Accused Features: The complaint alleges that Amneal’s ANDA Product comprises a polymorphic form of rifaximin covered by the patent's claims (Compl. ¶98).

U.S. Patent No. 8,518,949, U.S. Patent No. 8,741,904, U.S. Patent No. 9,271,968, and U.S. Patent No. 10,703,763 - Polymorphous Forms of Rifaximin, Processes for their Production and Use thereof in the Medicinal Preparations

  • Issued between August 27, 2013, and July 7, 2020.
  • Technology Synopsis: These patents are related to the ’196 Patent and concern specific polymorphic forms of the antibiotic rifaximin. The patents claim compositions and methods of treating bacterial activity in the gastrointestinal tract using compositions that comprise these specific polymorphic forms of rifaximin. (’763 Patent, Abstract; ’904 Patent, Abstract).
  • Asserted Claims: Unspecified in the complaint (Compl. ¶¶ 110, 122, 134, 146).
  • Accused Features: The complaint alleges that Amneal's ANDA Product is or contains a composition comprising a polymorphic form of rifaximin as claimed in these patents (Compl. ¶¶ 110, 122, 134, 146).

III. The Accused Instrumentality

Product Identification

  • The accused instrumentality is Amneal’s proposed generic rifaximin 550 mg tablets, for which Amneal seeks marketing approval via Abbreviated New Drug Application (ANDA) No. 218862 (Compl. ¶53).

Functionality and Market Context

  • The ANDA Product is an antibacterial drug intended for the treatment of irritable bowel syndrome with diarrhea (IBS-D) in adults (Compl. ¶55). The complaint alleges that, upon FDA approval, Amneal will manufacture, market, and sell this product as a generic version of Salix’s Xifaxan® 550 mg tablets throughout the United States (Compl. ¶¶ 12-13, 54). The central act of infringement alleged under 35 U.S.C. § 271(e)(2)(A) is the submission of the ANDA itself to obtain approval for this commercial activity prior to the expiration of the patents-in-suit (Compl. ¶61).

No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

U.S. Patent No. 11,564,912 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) The complaint alleges that Amneal's ANDA Product, if approved, will be prescribed and administered to relieve the signs and symptoms of IBS with diarrhea. ¶76 col. 18:45-46
in a female subject The product is for use in "human patients," a group that includes females. The complaint alleges Amneal will induce this use. ¶76, ¶78 col. 18:46
comprising administering... 550 mg of rifaximin TID The accused ANDA Product is a 550 mg rifaximin tablet. The complaint alleges Amneal seeks approval for uses that will infringe. ¶53, ¶76 col. 18:48-49

U.S. Patent No. 10,456,384 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) The complaint alleges that Amneal's ANDA Product, if approved, will be prescribed and administered to relieve the signs and symptoms of IBS with diarrhea. ¶88 col. 45:15-16
in a subject 65 years of age or older The product is for use in "adults," a group that includes subjects 65 years of age or older. The complaint alleges Amneal will induce this use. ¶55, ¶88, ¶90 col. 45:16-17
comprising administering... 550 mg of rifaximin TID The accused ANDA Product is a 550 mg rifaximin tablet. The complaint alleges Amneal seeks approval for uses that will infringe. ¶53, ¶88 col. 45:18-20
  • Identified Points of Contention:
    • Scope Questions: A central dispute for the method claims ('912 and '384 Patents) may be whether seeking approval to market a drug for "adults" with IBS-D is sufficient to establish specific intent to induce infringement in the claimed sub-populations of "female subjects" or "subjects 65 years of age or older." The analysis will depend on the content of Amneal's proposed product label, which is not detailed in the complaint.
    • Technical Questions: For the composition of matter patents ('196, '763, etc.), the dispute will raise a fundamental technical question: does the active pharmaceutical ingredient in Amneal's ANDA Product possess the specific crystalline polymorphic structure defined by the powder X-ray diffraction peaks recited in the patent claims? This will require expert analysis of test data for Amneal's product.

V. Key Claim Terms for Construction

  • The Term: "treating one or more symptoms of irritable bowel syndrome (IBS)" (from claims of the '912 and '384 Patents)
  • Context and Importance: This term defines the scope of the claimed method. Its construction is critical because the infringement analysis for inducement will turn on whether Amneal’s proposed product label instructs or encourages physicians to perform this specific "treating" activity. Practitioners may focus on this term because its definition could determine whether a general instruction to relieve IBS symptoms meets the claim limitation.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The specifications provide a non-exhaustive list of IBS symptoms, including "cramping, pain, diarrhea, constipation, lumpy stool, watery stool, frequent stool production, abdominal pain, abdominal discomfort, and/or urgency" ('384 Patent, col. 2:58-61). This language may support an interpretation where ameliorating any one of these symptoms constitutes "treating."
    • Evidence for a Narrower Interpretation: The patents extensively discuss clinical trials where "adequate relief" was a defined endpoint, measured by a "yes" response from a subject to a specific question ('384 Patent, col. 2:50-58). A party could argue that "treating" requires achieving this specific, defined level of "adequate relief" rather than any subjective improvement in symptoms.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges induced and contributory infringement for all asserted patents. The factual basis for inducement is that Amneal, with knowledge of the patents, will market its ANDA Product with a label and instructions that will inevitably encourage and aid physicians to prescribe, and patients to use, the drug in an infringing manner (e.g., Compl. ¶¶ 65-67, 77-79, 89-91). Knowledge is alleged based on Amneal's reference to the patents in its Notice Letter and their listing in the FDA's Orange Book (e.g., Compl. ¶¶ 70, 82, 94).
  • Willful Infringement: The complaint alleges that Amneal's infringing acts will be performed with knowledge of the patents-in-suit and with intent to encourage infringement prior to their expiration (e.g., Compl. ¶¶ 69, 81, 93). Plaintiffs also state that "Amneal's statements...are devoid of an objective good faith basis in either facts or the law" and that the case is "exceptional," which forms the basis for a potential claim for enhanced damages and attorneys' fees (Compl. ¶57; Prayer for Relief, ¶vi).

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

  • A core issue will be one of induced infringement: for the method patents directed to specific patient sub-populations ('912 Patent for females, '384 Patent for subjects ≥65), can specific intent to induce infringement be established from a product label directed to "adults," or is a more targeted instruction required? The outcome may depend heavily on the precise language of Amneal’s proposed label and marketing materials.
  • A key evidentiary question for the composition patents (e.g., '196, '763) will be one of technical identity: does the rifaximin in Amneal’s proposed product exhibit the specific polymorphic forms defined by the X-ray diffraction data in the asserted claims? This question will be resolved through expert testimony and comparative analytical testing of the accused product.
  • The case will also present a question of claim scope: can the term "treating," as used in the method claims, be broadly construed to cover any administration of the drug for IBS-D symptoms, or will the court limit its meaning to the achievement of specific clinical endpoints detailed in the patents' specifications? This construction will be central to determining whether Amneal’s proposed label induces infringement.