Curia IP Holdings v. Salix Pharmaceuticals — Rifaximin Polymorph Patent Case Terminated After 842 Days
Curia IP Holdings asserted four U.S. patents covering alpha and beta polymorphic forms of rifaximin against Salix Pharmaceuticals, Bausch Health, and Alfasigma entities in New Jersey, targeting XIFAXAN® 200 mg and 550 mg tablets. The case ran 842 days before termination, with the public record silent on settlement terms or adjudicated liability.
Four-patent rifaximin polymorph dispute closed in New Jersey after 842 days
Curia IP Holdings, LLC filed this infringement action on 25 October 2021 in the U.S. District Court for the District of New Jersey, asserting four issued U.S. patents — US9186355B2, US10961257B2, US10556915B2, and US10745415B2 — against a group of defendants that included Salix Pharmaceuticals, Inc., Bausch Health Companies, Inc., Alfasigma S.p.A., and Alfasigma USA, Inc. The patents-in-suit relate to mixtures comprising alpha (α) and beta (β) polymorphic forms of rifaximin, the active pharmaceutical ingredient in XIFAXAN® 200 mg and 550 mg tablets.
The case was closed on 14 February 2024, 842 days after filing, under the designation ‘Case Terminated.’ The public record does not specify whether termination followed a negotiated settlement, voluntary dismissal, or a procedural order, and no prejudice designation has been recorded. The absence of a verdict or judgment on the merits means neither party can be said to have prevailed on the infringement or validity questions raised in the amended complaint.
An 842-day duration for a multi-defendant, four-patent pharmaceutical infringement case is broadly consistent with pre-trial resolution timelines in the District of New Jersey, a venue that handles significant pharmaceutical patent dockets and where cases commonly resolve before trial. What drove resolution — whether licensing negotiations, claim construction rulings, or commercial factors — is not apparent from the public docket. The terms of any agreement, if one exists, remain confidential and undisclosed.
Filing to settlement in 842 days
842 days from filing to termination in New Jersey District Court
What ‘Case Terminated’ means for Curia, Salix, and Alfasigma
Case Terminated: what the record actually tells us
‘Case Terminated’ is a docket-level administrative designation, not a substantive legal outcome. It confirms the court has closed the matter but does not specify whether termination followed a consent order, voluntary dismissal, settlement agreement, or judicial ruling. In multi-party pharmaceutical disputes of this complexity, termination most commonly reflects a negotiated resolution, but that inference cannot be confirmed from the public record alone.
No merits adjudication on recordWith or without prejudice? The public record is silent
A dismissal with prejudice bars the plaintiff from refiling the same claims against the same defendants, functioning as a final judgment on the merits. A dismissal without prejudice preserves the right to refile. Because the basis of termination here does not specify prejudice status, it is not possible to determine whether Curia retains the right to pursue these defendants again on the same patents. Practitioners monitoring this portfolio should track any subsequent filings by Curia against these parties.
Prejudice status unconfirmedFour defendants — liability allocation remains undisclosed
The amended complaint named Salix Pharmaceuticals, Bausch Health Companies, Alfasigma S.p.A., and Alfasigma USA, Inc. as distinct defendants. Multi-defendant pharmaceutical cases typically involve differentiated roles — manufacturer, NDA holder, marketer — and any settlement would ordinarily address each party’s exposure separately. Because no settlement terms are public, the allocation of any consideration or licence rights among defendants is unknown.
Multi-defendant resolution opaqueFour rifaximin patents remain live assets post-termination
All four asserted patents — US9186355B2, US10961257B2, US10556915B2, and US10745415B2 — covering α/β rifaximin polymorph mixtures remain issued. Termination without a validity ruling or covenant-not-to-sue on the public record suggests these patents could be asserted again. Competitors and generic entrants in the rifaximin space should treat this portfolio as an active enforcement risk until expiry or invalidation proceedings conclude.
Portfolio enforcement risk persistsFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | Curia IP Holdings, LLC | Company | Patent assertion entity — holder of four U.S. rifaximin polymorph patents including US9186355B2Search in Eureka ↗ |
| Defendant | Salix Pharmaceuticals, Inc. | Company | Salix Pharmaceuticals (Bausch Health subsidiary), marketer of XIFAXAN® rifaximin tablets; co-defendants Alfasigma entities.Search in Eureka ↗ |
| Plaintiff counsel | Eric I. Abraham | Attorney | Counsel for Curia IP Holdings, LLCSearch in Eureka ↗ |
| Plaintiff counsel | William Murtha | Attorney | Counsel for Curia IP Holdings, LLCSearch in Eureka ↗ |
| Plaintiff counsel | Zhibin Li | Attorney | Counsel for Curia IP Holdings, LLCSearch in Eureka ↗ |
| Defendant counsel | Justin Taylor Quinn | Attorney | Counsel for Salix Pharmaceuticals, Inc.Search in Eureka ↗ |
| Defendant counsel | William P. Deni , Jr. | Attorney | Counsel for Salix Pharmaceuticals, Inc.Search in Eureka ↗ |
| Presiding judge | Judge / | Chief Judge | New Jersey District Court — Chief JudgeSearch in Eureka ↗ |
Stipulation of dismissal — official text
The quoted text is drawn from Curia’s Amended Complaint, not a court ruling or judgment. It establishes Curia’s pleaded theory — infringement of α/β rifaximin polymorph patents under 35 U.S.C. §§ 271 and 281-85 — but carries no adjudicative weight. The case terminated before any verdict on these allegations. Neither infringement nor validity of the four asserted patents was decided on the merits, meaning the complaint language does not bind the defendants and does not establish liability.
US9186355B2 and three further patents — rifaximin α/β polymorph mixtures
The four asserted patents — US9186355B2, US10961257B2, US10556915B2, and US10745415B2 — cover mixtures of alpha (α) and beta (β) polymorphic forms of rifaximin, a minimally absorbed antibiotic used to treat traveller’s diarrhoea and hepatic encephalopathy. Polymorph patents protect specific crystalline or amorphous physical forms of a drug compound; because the same chemical entity can exhibit different polymorphic forms with distinct stability, bioavailability, and manufacturability profiles, these patents can extend commercial exclusivity well beyond the primary compound patent.
For XIFAXAN®, one of Bausch Health’s highest-revenue products, the polymorphic composition of the rifaximin tablets is commercially critical. A portfolio of four patents covering α/β mixtures creates layered protection that complicates generic entry and licensing negotiations. Curia, as an IP holding entity rather than a manufacturer, asserting this portfolio against the full supply chain — including Alfasigma, the reported manufacturer — suggests these patents were acquired specifically for enforcement value in the rifaximin commercial ecosystem.
Should your rifaximin product be cleared against US9186355B2 and related patents?
Any company developing, manufacturing, or distributing rifaximin-based formulations — including generic XIFAXAN® applicants, 505(b)(2) developers, or suppliers to branded manufacturers — should conduct a freedom-to-operate analysis against all four Curia patents. The α/β polymorph claim scope may capture formulations that were not originally targeted by the primary compound patent, and the multi-patent portfolio creates overlapping claim risk that a single patent clearance would not address.
PatSnap Eureka’s FTO Search Agent can map the claim language of US9186355B2, US10961257B2, US10556915B2, and US10745415B2 against your product’s polymorphic composition, identify relevant prior art, and flag expiry timelines. Claim monitoring alerts can notify your team if Curia or any subsequent assignee files continuation claims or new assertions in this space — critical intelligence for any rifaximin market entrant.
Run a freedom-to-operate analysis on US9186355B2 to assess your product’s exposure
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What this case signals for the rifaximin and pharmaceutical polymorph IP landscape
A four-patent assault on XIFAXAN® by a specialised IP holding entity highlights the ongoing polymorph patent risk in branded pharmaceutical markets.
Pharmaceutical polymorph patents remain a viable enforcement vector
Curia’s ability to sustain a four-patent infringement action against the XIFAXAN® supply chain — spanning manufacturer, NDA holder, and distributors — for over 840 days without early dismissal signals that polymorph-specific patent claims continue to withstand initial scrutiny in district courts. Companies in the rifaximin space should audit polymorph coverage in their FTO analyses.
New Jersey remains a strategically active venue for pharma patent disputes
The District of New Jersey is one of the most active jurisdictions for pharmaceutical patent litigation, including Hatch-Waxman and non-ANDA infringement actions. Filing here against Salix and Bausch Health — both with significant New Jersey commercial ties — is consistent with a deliberate venue strategy by plaintiff-side IP holders seeking a patent-experienced bench.
Curia v Salix — key questions answered
Curia asserted four U.S. patents: US9186355B2, US10961257B2, US10556915B2, and US10745415B2. All four cover mixtures of alpha (α) and beta (β) polymorphic forms of rifaximin, the active ingredient in XIFAXAN® 200 mg and 550 mg tablets.
The case was closed on 14 February 2024 under the designation ‘Case Terminated,’ 842 days after filing. The public record does not specify the basis — whether settlement, voluntary dismissal, or court order — and no prejudice designation has been recorded.
The amended complaint named Salix Pharmaceuticals, Inc., Bausch Health Companies, Inc., Alfasigma S.p.A., and Alfasigma USA, Inc. Salix is a Bausch Health subsidiary and the NDA holder for XIFAXAN®; Alfasigma entities are associated with rifaximin manufacturing.
Polymorph patents protect specific crystalline forms of a drug compound. For rifaximin, α/β mixture patents can extend commercial exclusivity beyond the primary compound patent by covering the precise polymorphic composition found in XIFAXAN® tablets, creating barriers for generic manufacturers who must match or avoid that composition.
No. ‘Case Terminated’ is an administrative closure designation. No court ruled on the validity or infringement of the four asserted patents. All four remain issued U.S. patents and could potentially be asserted again, subject to any confidential agreement between the parties that is not reflected in the public record.
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