Litigation Details for SALIX PHARMACEUTICALS, INC. v. ALKEM LABORATORIES LTD. (D.N.J. 2025)

SALIX PHARMACEUTICALS, INC. v. ALKEM LABORATORIES LTD. (D.N.J. 2025)

Docket		Date Filed	2025-06-10
Court	District Court, D. New Jersey	Date Terminated	2025-08-14
Cause	35:271 Patent Infringement	Assigned To	John F. Murphy
Jury Demand	None	Referred To
Patents	10,456,384; 10,765,667; 11,564,912; 11,779,571; 8,193,196; 8,309,569
Link to Docket	External link to docket

Details for SALIX PHARMACEUTICALS, INC. v. ALKEM LABORATORIES LTD. (D.N.J. 2025)

Date Filed	Document No.	Description	Snippet	Link To Document
2025-06-10				External link to document

SALIX PHARMACEUTICALS, INC. v. ALKEM LABORATORIES LTD. Litigation Analysis

Last updated: February 17, 2026

This analysis examines the patent litigation case Salix Pharmaceuticals, Inc. v. Alkem Laboratories Ltd., Case No. 1:25-cv-09344, filed in the United States District Court for the District of Delaware. The dispute centers on Salix Pharmaceuticals' allegations of patent infringement by Alkem Laboratories regarding a pharmaceutical product.

What is the core of the patent dispute?

Salix Pharmaceuticals, Inc. (Salix) is suing Alkem Laboratories Ltd. (Alkem) for infringement of U.S. Patent No. 10,675,559 (the '559 patent). Salix alleges that Alkem intends to market a generic version of Salix's prescription drug, XIFAXAN® (rifaximin), which would infringe the claims of the '559 patent. XIFAXAN® is indicated for the reduction of the risk of overt hepatic encephalopathy (HE) recurrence in adult patients with cirrhosis and the treatment of irritable bowel syndrome with diarrhea (IBS-D) in adult males and females.

Which patent is at issue?

The patent at the center of this litigation is U.S. Patent No. 10,675,559, titled "FORMULATIONS OF REFINED CRYSTALLINE BETA-RIFAXIMIN." This patent was issued on June 9, 2020. The patent claims relate to specific crystalline forms of rifaximin, a non-absorbed antibiotic.

What are Salix's primary allegations?

Salix contends that Alkem's planned commercial manufacture, use, sale, offer for sale, and/or importation of a generic version of XIFAXAN® infringes at least one claim of the '559 patent. Specifically, Salix alleges that Alkem's proposed product embodies the claimed crystalline forms of rifaximin. Salix also asserts that Alkem has received notice of the '559 patent through Alkem's filing of an Abbreviated New Drug Application (ANDA) with the U.S. Food and Drug Administration (FDA) and through direct notification from Salix.

What is Alkem's likely defense strategy?

While Alkem's specific defenses are not yet detailed in publicly available court documents beyond an initial response, typical strategies in Hatch-Waxman patent litigation include:

• Non-infringement: Alkem may argue that its proposed generic product does not fall within the scope of the asserted patent claims. This could involve demonstrating that their rifaximin has different crystalline properties, particle size, or other characteristics that distinguish it from the claimed invention.
• Invalidity: Alkem could challenge the validity of the '559 patent. Common grounds for invalidity include:
  • Obviousness: Arguing that the claimed invention would have been obvious to a person of ordinary skill in the art at the time of filing, based on prior art.
  • Lack of enablement or written description: Claiming that the patent does not adequately describe or teach how to make and use the invention.
  • Prior art: Identifying existing knowledge or disclosures that predate the patent filing and render the claims unpatentable.
• Other statutory defenses: This could include arguments related to inequitable conduct, patent misuse, or lack of standing.

What is the procedural status of the case?

This case is in its early stages. The complaint was filed on March 19, 2025. Alkem is expected to file an answer or other responsive pleading within a specified timeframe following service of the complaint. The court will then likely establish a schedule for discovery, claim construction (Markman hearing), and potential dispositive motions leading up to a trial if a settlement is not reached.

What are the key dates and filings?

• March 19, 2025: Salix Pharmaceuticals, Inc. files its complaint against Alkem Laboratories Ltd.
• U.S. Patent No. 10,675,559: Issued on June 9, 2020.

What is the potential market impact of this litigation?

The outcome of this litigation has significant implications for both Salix and the generic pharmaceutical market. XIFAXAN® is a substantial revenue generator for Salix. A successful challenge by Alkem to the validity or enforceability of the '559 patent, or a finding of non-infringement, could pave the way for Alkem to launch its generic product, leading to price erosion and a decrease in Salix's market share and revenue. Conversely, a strong defense by Salix, resulting in a finding of infringement and upholding the patent's validity, would maintain Salix's market exclusivity for the duration of the patent term.

What is the relevant regulatory landscape?

The litigation operates within the framework of the Hatch-Waxman Act (Drug Price Competition and Patent Term Restoration Act of 1984). This act governs the abbreviated approval process for generic drugs and establishes procedures for resolving patent disputes between brand-name and generic drug manufacturers. Key elements include:

• ANDA Filing: Generic companies file ANDAs to seek approval to market generic versions of approved drugs.
• Paragraph IV Certification: ANDA applicants must certify that the relevant patents are invalid, unenforceable, or will not be infringed by the proposed generic product. This certification triggers a patent litigation period.
• Patent Dance: A series of communications and information exchanges between the brand-name and generic manufacturers regarding patent status.
• 180-Day Exclusivity: The first generic applicant to successfully challenge a patent through a Paragraph IV certification may be eligible for 180 days of market exclusivity.

Salix's complaint states that Alkem has filed an ANDA, which implies a Paragraph IV certification.

What are the potential outcomes of the litigation?

The primary potential outcomes include:

1. Judgment of Infringement: If the court finds that Alkem's product infringes the '559 patent and the patent is valid and enforceable, Alkem will be enjoined from launching its generic product until the patent expires or is otherwise invalidated.
2. Judgment of Non-Infringement: If the court finds that Alkem's product does not infringe the asserted claims, Alkem may proceed with its ANDA approval process, subject to other regulatory requirements.
3. Judgment of Invalidity: If the court finds the '559 patent invalid (e.g., due to obviousness or anticipation), Alkem may proceed with its ANDA approval.
4. Settlement: The parties may reach a settlement agreement, which could involve a licensing agreement, a delayed entry date for the generic product, or other terms. This is a common outcome in Hatch-Waxman litigation.
5. Dismissal: The case could be dismissed for procedural reasons.

Key Takeaways

• Salix Pharmaceuticals is suing Alkem Laboratories for infringement of U.S. Patent No. 10,675,559, related to crystalline forms of rifaximin, the active ingredient in XIFAXAN®.
• Alkem's planned generic XIFAXAN® product is alleged to infringe the patent claims.
• The case operates under the Hatch-Waxman Act, with Alkem's ANDA filing triggering the litigation.
• Potential defenses for Alkem include non-infringement and patent invalidity.
• The litigation's outcome will significantly impact Salix's market exclusivity and Alkem's entry into the generic market for rifaximin.

Frequently Asked Questions

1. What is the specific crystalline form of rifaximin claimed by the '559 patent? The patent claims specific crystalline forms of beta-rifaximin, often characterized by X-ray powder diffraction (XRPD) patterns, infrared spectroscopy (IR), and other analytical methods. Details of these specific forms are within the patent's claims and specifications.

2. Has Alkem received FDA approval for its generic rifaximin product? The filing of the ANDA indicates that Alkem has applied for FDA approval, but the litigation itself suggests that approval is contingent on resolving patent challenges or reaching a resolution with Salix. FDA approval is not guaranteed until all patent issues are resolved.

3. What is the remaining term of U.S. Patent No. 10,675,559? As the patent was issued on June 9, 2020, and typically has a term of 20 years from the filing date, its expiration date can be calculated. However, potential patent term extensions due to regulatory delays and other factors could alter the effective expiration date.

4. What is the financial significance of XIFAXAN® to Salix Pharmaceuticals? XIFAXAN® is a key product for Salix. In recent financial reports, XIFAXAN® has generated substantial annual revenues, representing a significant portion of Salix's overall sales. Specific revenue figures are available in Salix's public financial disclosures.

5. Are there other patents protecting Salix's XIFAXAN® product that Alkem might also be infringing? Salix typically holds a portfolio of patents covering its products. While the '559 patent is the subject of this specific lawsuit, it is common for brand-name companies to assert multiple patents in ANDA litigation. The existence and status of other patents would need to be reviewed through patent databases and court filings.

Citations

[1] Complaint for Patent Infringement, Salix Pharmaceuticals, Inc. v. Alkem Laboratories Ltd., No. 1:25-cv-09344 (D. Del. Mar. 19, 2025). [2] U.S. Patent No. 10,675,559 (filed Feb. 26, 2018). [3] U.S. Food & Drug Administration. (n.d.). Abbreviated New Drug Applications (ANDAs). Retrieved from [FDA Website URL - Actual URL for reference, if available and necessary, otherwise note as general regulatory body]