1:25-cv-09344
Salix Pharma Inc v. Alkem Laboratories Ltd
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Salix Pharmaceuticals, Inc., et al. (California, Delaware, Italy, Ireland)
- Defendant: Alkem Laboratories Ltd. (India)
- Plaintiff’s Counsel: Morgan, Lewis & Bockius LLP
- Case Identification: 3:25-cv-09344, D.N.J., 06/10/2025
- Venue Allegations: Venue is asserted on the basis that Defendant is a foreign corporation organized under the laws of India and may therefore be sued in any U.S. judicial district.
- Core Dispute: Plaintiff alleges that Defendant’s filing of an Abbreviated New Drug Application (ANDA) for a generic version of the drug Xifaxan® (rifaximin) constitutes an act of infringement of three U.S. patents related to specific polymorphic forms of rifaximin and methods of its use for treating Irritable Bowel Syndrome (IBS).
- Technical Context: The dispute centers on rifaximin, a minimally-absorbed oral antibiotic used to treat gastrointestinal conditions, which represents a significant pharmaceutical market for branded drugs facing generic competition under the Hatch-Waxman Act.
- Key Procedural History: The litigation was initiated under the Hatch-Waxman framework following Defendant’s notification to Plaintiff, via a Paragraph IV certification letter, of its ANDA submission to the FDA seeking approval to market a generic rifaximin product prior to the expiration of the patents-in-suit.
Case Timeline
| Date | Event |
|---|---|
| 2005-03-03 | ’196 Patent Priority Date |
| 2008-02-26 | ’571 and ’912 Patents Priority Date |
| 2010-03-24 | FDA Approval of 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 |
| 2025-04-28 | Alkem sends Paragraph IV Notice Letter to Salix |
| 2025-06-10 | 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)"
The Invention Explained
- Problem Addressed: The patent's background section describes the need for effective treatments for bowel diseases such as Irritable Bowel Syndrome (IBS), a condition with symptoms including cramping, pain, and diarrhea. (Compl. ¶18; ’571 Patent, col. 1:40-54).
- The Patented Solution: The invention provides a specific method for treating symptoms of diarrhea-predominant IBS (dIBS), particularly bloating in female subjects. The solution involves administering a 550 mg dose of the antibiotic rifaximin three times daily (TID) for a fixed 14-day period, which is described as providing a durable therapeutic response even after the treatment course is completed. (’571 Patent, col. 2:56-62, col. 6:45-53).
- Technical Importance: This method purports to offer a significant clinical advantage by providing lasting symptom relief from a chronic condition through a short, defined course of antibiotic therapy, rather than requiring continuous, long-term medication. (’571 Patent, col. 2:40-44).
Key Claims at a Glance
- The complaint asserts infringement of one or more claims without specifying them (Compl. ¶32). Independent claim 1 is representative:
- 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,
- thereby treating bloating associated with dIBS in 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)"
The Invention Explained
- Problem Addressed: Similar to the ’571 patent, this patent addresses the need for effective treatments for the symptoms of IBS, which can include diarrhea, constipation, pain, and abdominal discomfort. (Compl. ¶19; ’912 Patent, col. 1:40-54).
- The Patented Solution: The patent describes methods of treating IBS symptoms in female subjects by administering 550 mg of rifaximin three times a day for 14 days. A key aspect of the patented solution is the "durability of response," wherein a patient who responds to the 14-day treatment experiences continued relief after the antibiotic is discontinued. (’912 Patent, Abstract; col. 2:40-44).
- Technical Importance: The invention claims to provide a method for achieving sustained remission of IBS symptoms with a short, acute course of treatment, potentially altering the management paradigm for a chronic gastrointestinal disorder. (’912 Patent, col. 2:40-44).
Key Claims at a Glance
- The complaint asserts infringement of one or more claims without specifying them (Compl. ¶44). Independent claim 1 is representative:
- 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,
- thereby treating one or more symptoms of IBS in 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"
Technology Synopsis
This patent addresses the technical problem that the same active pharmaceutical ingredient can exist in different crystalline structures, or polymorphs, which can affect its stability, solubility, and bioavailability. (’196 Patent, col. 1:53-64). The invention discloses the discovery and characterization of specific rifaximin polymorphs, designated as forms δ and ε, and methods to reliably produce them, thereby ensuring consistent properties for the final drug product. (’196 Patent, Abstract; col. 2:38-46).
Asserted Claims
The complaint asserts infringement of one or more claims without specifying them (Compl. ¶56). Claim 17, directed to polymorphic form δ, is representative.
Accused Features
The complaint alleges that Defendant’s ANDA Product is a composition comprising a polymorphic form of rifaximin that infringes the claims of the ’196 Patent. (Compl. ¶55).
III. The Accused Instrumentality
Product Identification
Defendant Alkem’s generic rifaximin 550 mg tablets, for which it seeks FDA approval under Abbreviated New Drug Application No. 220451 (the "ANDA Product"). (Compl. ¶2).
Functionality and Market Context
The ANDA Product is a generic equivalent of Plaintiff's Xifaxan® 550 mg tablets. (Compl. ¶1). Alkem is seeking FDA approval to market its product for the treatment of irritable bowel syndrome with diarrhea ('IBS-D') in adults, placing it in direct competition with Plaintiff's branded product. (Compl. ¶24). The filing of the ANDA signifies Defendant's intent to enter the market for this widely-prescribed gastrointestinal antibiotic. (Compl. ¶¶8-9).
No probative visual evidence provided in complaint.
IV. Analysis of Infringement Allegations
The complaint does not provide specific claim charts or detailed infringement theories. The following summaries are based on the asserted claims and the general allegations in the complaint.
U.S. Patent No. 11,779,571 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) in a female subject... | Defendant's ANDA seeks approval for its product for the treatment of IBS-D in adults, a patient population that includes females experiencing bloating symptoms. (Compl. ¶¶24, 33). | ¶¶24, 33 | col. 4:5-7 |
| ...comprising administering, 550 mg of rifaximin TID for 14 days to the female subject... | The ANDA Product is a 550 mg rifaximin tablet, and the complaint alleges that Defendant's proposed product labeling will induce physicians and patients to administer it according to the claimed dosage and duration. (Compl. ¶¶2, 33, 36). | ¶¶2, 36 | col. 6:45-53 |
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) in a female subject... | Defendant's ANDA seeks approval for treating IBS-D, which necessarily involves treating IBS symptoms in adult patients, including females. (Compl. ¶¶24, 45). | ¶¶24, 45 | col. 2:45-55 |
| ...said method comprising administering, 550 mg of rifaximin TID for 14 days to the female subject... | The ANDA Product is a 550 mg tablet, and Plaintiff alleges Defendant will induce infringement through product labeling that instructs or encourages the claimed dosing regimen. (Compl. ¶¶2, 45, 48). | ¶¶2, 48 | col. 6:45-53 |
Identified Points of Contention
- Scope Questions: For the ’571 and ’912 Patents, a primary question will be whether the language of Defendant's final, FDA-approved product label will actively encourage, or induce, the specific treatment method claimed (550 mg TID for 14 days), especially as it relates to female patients. For the ’196 Patent, the key question is whether the term "polymorphic form δ" (or ε), defined by specific X-ray diffraction peaks, reads on the crystalline structure of the rifaximin in Defendant's ANDA product.
- Technical Questions: The central technical question for the ’196 Patent will be a factual one of chemical identity. Resolution will depend on analytical data (e.g., XRPD) from Defendant's ANDA product to determine if it exhibits the characteristic peaks of the claimed polymorphs. The complaint does not provide sufficient detail for analysis of the specific polymorph contained in the ANDA product.
V. Key Claim Terms for Construction
The Term: "polymorphic form δ" (’196 Patent)
Context and Importance
The definition of this term is dispositive for infringement of the ’196 Patent. The dispute will center on whether the crystalline structure in Defendant's product meets the precise definition of "form δ" as claimed in the patent, which is defined by a series of characteristic peaks in an X-ray powder diffractogram.
Intrinsic Evidence for Interpretation
- Evidence for a Broader Interpretation: The specification describes the form by referencing its most characteristic peaks, which a court could interpret to mean that the presence of these key peaks, even with minor instrumental variations, is sufficient to fall within the claim scope. (’196 Patent, col. 5:46-50, Claim 17).
- Evidence for a Narrower Interpretation: The patent provides a specific X-ray diffractogram in Figure 1 and lists numerous peak locations to ±0.2 degrees 2θ. (’196 Patent, col. 6:6-10). A court might construe the claim to require the presence of all, or substantially all, of these enumerated peaks at the specified locations, making the definition highly specific and narrow.
The Term: "thereby treating" (’571 and ’912 Patents)
Context and Importance
This term appears in the final clause of the method claims. Practitioners may focus on this term because its construction could determine whether the claim requires only the administration of the drug according to the specified regimen or if it also requires the achievement of a specific clinical outcome (i.e., actual treatment of symptoms).
Intrinsic Evidence for Interpretation
- Evidence for a Broader Interpretation: The specification defines "ameliorate" and "improvement" in broad terms, suggesting that "treating" could encompass any detectable, positive change. (’912 Patent, col. 11:7-24). This may support an interpretation where proper administration of the drug satisfies the limitation.
- Evidence for a Narrower Interpretation: The patents heavily emphasize the "durability of response" as a key feature of the invention. (’912 Patent, col. 2:40-44). This context may support an argument that "thereby treating" requires not just administration, but the achievement of the durable, post-treatment relief described as the core of the invention.
VI. Other Allegations
Indirect Infringement
The complaint alleges induced infringement for all three patents. The theory is that Defendant, with knowledge of the patents from their Orange Book listing, intends for its generic product to be used in an infringing manner, and its proposed product label and instructions will encourage and facilitate that infringing use by physicians and patients. (Compl. ¶¶36-39, 48-51, 59-63).
Willful Infringement
Willfulness is alleged for all three patents. The complaint asserts that Defendant knew of the patents-in-suit and their coverage of the Xifaxan® product, and that its Paragraph IV certification and ANDA filing were done in "conscious disregard" of Plaintiff's patent rights. (Compl. ¶¶35, 47, 60). Plaintiff further alleges the case is 'exceptional,' suggesting Defendant's invalidity and non-infringement positions lack an objective good faith basis. (Compl. ¶26).
VII. Analyst’s Conclusion: Key Questions for the Case
- A central issue for the method-of-use patents ('571 and '912) will be one of induced infringement: will the final, FDA-approved label for Alkem's generic product contain instructions or indications that actively encourage physicians and patients to perform the specific dosing regimen (550 mg TID for 14 days) required by the asserted claims, particularly for female subjects?
- For the composition patent ('196), the case will turn on a key technical question of identity: does the crystalline form of rifaximin in Alkem's ANDA product, as established by analytical evidence, meet the specific structural limitations defining the patented polymorphs, or does it represent a different, non-infringing form?
- A significant secondary question will be objective reasonableness: did Alkem possess a good-faith, objectively reasonable basis for its non-infringement and invalidity positions outlined in its Paragraph IV certification, or was its ANDA filing an act of willful infringement potentially rendering the case exceptional under 35 U.S.C. § 285?