DCT

1:26-cv-01154

Mirum Pharma Inc v. Zenara Pharma Pvt Ltd

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: Mirum Pharmaceuticals, Inc. v. Zenara Pharma Private Limited, 1:26-cv-01154, D. Del., 09/14/2026
  • Venue Allegations: Plaintiffs allege venue is proper in the District of Delaware because Defendants conduct substantial business in the state, have purposefully availed themselves of its laws, and the consequences of the alleged infringement will be suffered there.
  • Core Dispute: Plaintiffs allege that Defendants' submission of an Abbreviated New Drug Application (ANDA) to the FDA for generic versions of Plaintiffs' LIVMARLI® (maralixibat) tablets constitutes an act of infringement of eight U.S. patents.
  • Technical Context: The technology involves methods of using and formulating an Apical Sodium-dependent Bile Acid Transporter (ASBTI) inhibitor for the treatment of rare pediatric cholestatic liver diseases, such as Alagille syndrome and progressive familial intrahepatic cholestasis.
  • Key Procedural History: The action was triggered by a Notice Letter, dated August 4, 2026, in which Defendant Zenara notified Plaintiffs of its ANDA filing containing a Paragraph IV certification, asserting that the patents-in-suit are invalid, unenforceable, and/or not infringed by its proposed generic products.

Case Timeline

Date Event
2010-05-26 Priority Date for ’053 Patent
2011-10-28 Priority Date for ’657 Patent, ’251 Patent, and ’267 Patent
2012-03-06 Priority Date for ’661 Patent
2019-02-12 Priority Date for ’647 Patent and ’745 Patent
2019-12-24 ’657 Patent Issued
2022-01-25 ’647 Patent Issued
2022-01-25 ’661 Patent Issued
2022-03-01 ’053 Patent Issued
2022-07-05 ’251 Patent Issued
2022-11-15 ’745 Patent Issued
2023-10-05 Priority Date for ’050 Patent
2025-05-13 ’050 Patent Issued
2025-07-08 ’267 Patent Issued
2026-08-04 Date of Defendant Zenara's Notice Letter
2026-09-14 Complaint Filing Date

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

U.S. Patent No. 10,512,657 - "Bile acid recycling inhibitors for treatment of pediatric cholestatic liver diseases"

  • Patent Identification: U.S. Patent No. 10,512,657, "Bile acid recycling inhibitors for treatment of pediatric cholestatic liver diseases," issued December 24, 2019 (the ’657 Patent). Compl. ¶38

The Invention Explained

  • Problem Addressed: The patent addresses the significant challenges in treating pediatric cholestatic liver diseases, which are rare, costly, and often require invasive procedures like liver transplantation due to a lack of safe and effective oral medications suitable for children ʼ657 Patent, col. 1:19-28
  • The Patented Solution: The invention provides a method for treating or ameliorating specific pediatric liver diseases, such as progressive familial intrahepatic cholestasis type 2 (PFIC2), by administering an Apical Sodium-dependent Bile Acid Transporter (ASBTI) inhibitor ʼ657 Patent, abstract This inhibitor, specifically the compound maralixibat, works by blocking the reabsorption of bile acids in the intestine, which in turn lowers the concentration of toxic bile acids in the liver and blood serum ʼ657 Patent, col. 17:35-51
  • Technical Importance: The invention provides a targeted, non-surgical oral therapy for a vulnerable pediatric population suffering from severe liver conditions for which treatment options are limited (ʼ657 Patent, col. 1:21-28).

Key Claims at a Glance

  • The complaint asserts independent claim 1 and dependent claims 2 and 3 Compl. ¶67 Compl. ¶75 Compl. ¶76
  • Independent Claim 1:
    • A method for treating or ameliorating progressive familial intrahepatic cholestasis type 2 (PFIC2) in a pediatric subject in need thereof;
    • comprising administering to the pediatric subject an Apical Sodium-dependent Bile Acid Transporter Inhibitor (ASBTI);
    • wherein the ASBTI is the specific compound maralixibat or a pharmaceutically acceptable salt thereof; and
    • wherein the ASBTI is effective for decreasing at least 20% of serum and/or hepatic bile acid levels in the pediatric subject as compared to bile acid levels prior to administration of the ASBTI.

U.S. Patent No. 11,229,647 - "Methods for treating cholestasis"

  • Patent Identification: U.S. Patent No. 11,229,647, "Methods for treating cholestasis," issued January 25, 2022 (the ’647 Patent). Compl. ¶42

The Invention Explained

  • Problem Addressed: The patent identifies the need for effective treatments for cholestasis, a condition of impaired bile secretion, particularly in pediatric patients with Alagille Syndrome (ALGS) where bile acid accumulation can lead to progressive liver damage ʼ647 Patent, col. 2:28-48 '647 Patent, col. 17:15-23
  • The Patented Solution: The invention discloses a specific method for treating ALGS in pediatric patients by administering the ASBTI inhibitor maralixibat chloride within a defined dosage range ʼ647 Patent, abstract This provides a precise therapeutic window for using the drug in this specific patient group ʼ647 Patent, col. 1:59-67
  • Technical Importance: By defining a specific dosage range for maralixibat in pediatric ALGS patients, the invention provides critical clinical guidance intended to maximize therapeutic benefit while managing safety.

Key Claims at a Glance

  • The complaint asserts independent claims 1 and 12 Compl. ¶88
  • Independent Claim 1:
    • A method for treating Alagille Syndrome (ALGS) in a pediatric subject in need of such treatment;
    • comprising administering to the subject maralixibat chloride, having a specific chemical structure, or a pharmaceutically acceptable alternative salt thereof;
    • wherein the maralixibat chloride is administered in an amount of from about 400 µg/kg/day to about 800 µg/kg/day.
  • Independent Claim 12:
    • A method for treating Alagille Syndrome (ALGS) in a pediatric subject in need of such treatment;
    • comprising administering to the subject maralixibat chloride, having a specific chemical structure, or a pharmaceutically acceptable alternative salt thereof;
    • wherein the maralixibat chloride is administered in an amount of about 400 µg/kg/day.
  • The complaint reserves the right to assert additional claims Compl. ¶88

U.S. Patent No. 11,229,661 - "Bile acid recycling inhibitors for treatment of pediatric cholestatic liver diseases"

  • Patent Identification: U.S. Patent No. 11,229,661, "Bile acid recycling inhibitors for treatment of pediatric cholestatic liver diseases," issued January 25, 2022 (the ’661 Patent). Compl. ¶45
  • Technology Synopsis: This patent claims methods for treating or ameliorating pediatric disorders characterized by a non-truncating BSEP mutation, such as PFIC2 or benign recurrent intrahepatic cholestasis 2 (BRIC2). The method involves administering an ASBTI inhibitor, such as maralixibat, to a pediatric subject with such a condition ʼ661 Patent, abstract '661 Patent, col. 1:17-39
  • Asserted Claims: Independent claim 1 Compl. ¶109
  • Accused Features: The use of Zenara’s generic maralixibat tablets for treating or ameliorating a pediatric disorder characterized by a non-truncating BSEP mutation, as allegedly instructed by Defendants’ proposed labeling Compl. ¶117

U.S. Patent No. 11,260,053 - "Bile acid recycling inhibitors and satiogens for treatment of diabetes, obesity, and inflammatory gastrointestinal conditions"

  • Patent Identification: U.S. Patent No. 11,260,053, "Bile acid recycling inhibitors and satiogens for treatment of diabetes, obesity, and inflammatory gastrointestinal conditions," issued March 1, 2022 (the ’053 Patent). Compl. ¶49
  • Technology Synopsis: This patent describes a method for increasing the concentration of bile acids and salts in the distal gastrointestinal tract of an individual. The method comprises administering an ASBTI, which inhibits bile salt recycling, thereby increasing their concentration in the distal ileum, colon, or rectum ’053 Patent, abstract
  • Asserted Claims: Independent claim 1 Compl. ¶129
  • Accused Features: The use of Zenara's ANDA Products, which allegedly decrease the reabsorption of bile acids from the terminal ileum, thereby increasing their concentration in the distal gastrointestinal tract Compl. ¶131 Compl. ¶134

U.S. Patent No. 11,376,251 - "Bile acid recycling inhibitors for treatment of pediatric cholestatic liver diseases"

  • Patent Identification: U.S. Patent No. 11,376,251, "Bile acid recycling inhibitors for treatment of pediatric cholestatic liver diseases," issued July 5, 2022 (the ’251 Patent). Compl. ¶52
  • Technology Synopsis: The patent covers methods for treating Alagille syndrome (ALGS) in pediatric subjects by administering a pharmaceutical composition containing an ASBTI inhibitor like maralixibat. The claims also specifically cover methods for treating or ameliorating pruritus (itching) in pediatric subjects suffering from ALGS ’251 Patent, abstract '251 Patent, claims 1, 19
  • Asserted Claims: Independent claims 1, 14, and 19 Compl. ¶146
  • Accused Features: The use of Zenara’s ANDA Products as instructed by the proposed labeling for treating ALGS and for treating pruritus in pediatric subjects with ALGS Compl. ¶¶154-155

U.S. Patent No. 11,497,745 - "Methods for treating cholestasis"

  • Patent Identification: U.S. Patent No. 11,497,745, "Methods for treating cholestasis," issued November 15, 2022 (the ’745 Patent). Compl. ¶56
  • Technology Synopsis: Similar to the ’647 Patent, this invention claims a method for treating ALGS in a pediatric subject by administering maralixibat. It claims a specific dosage range of "from 360 µg/kg/day to 880 µg/kg/day" ’745 Patent, claim 1 ’745 Patent, abstract
  • Asserted Claims: Independent claim 1 Compl. ¶167
  • Accused Features: The use of Zenara's ANDA Products as instructed by the proposed labeling to treat ALGS by administering maralixibat in an amount that falls within the claimed dosage range Compl. ¶176

U.S. Patent No. 12,350,267 - "Bile acid recycling inhibitors for treatment of pediatric cholestatic liver diseases"

  • Patent Identification: U.S. Patent No. 12,350,267, "Bile acid recycling inhibitors for treatment of pediatric cholestatic liver diseases," issued July 8, 2025 (the ’267 Patent). Compl. ¶59
  • Technology Synopsis: This patent covers methods for treating or ameliorating progressive familial intrahepatic cholestasis (PFIC) or pruritus associated with PFIC in a pediatric subject. The method involves administering a pharmaceutical composition comprising an ASBTI, such as maralixibat ’267 Patent, abstract '267 Patent, claims 1, 2
  • Asserted Claims: Independent claims 1, 2, and 20 Compl. ¶188
  • Accused Features: The use of Zenara’s ANDA Products as instructed by the proposed labeling for treating PFIC and associated pruritus in pediatric patients Compl. ¶¶196-197

U.S. Patent No. 12,296,050 - "Pharmaceutical compositions comprising maralixibat and uses thereof"

  • Patent Identification: U.S. Patent No. 12,296,050, "Pharmaceutical compositions comprising maralixibat and uses thereof," issued May 13, 2025 (the ’050 Patent). Compl. ¶63
  • Technology Synopsis: This is a formulation patent claiming a pharmaceutical composition that includes maralixibat and specific categories of excipients (diluent, glidant, lubricant, disintegrant) within defined weight-by-weight percentage ranges ’050 Patent, claim 1 The invention aims to create a stable and effective solid oral dosage form.
  • Asserted Claims: Independent claims 1 and 17 Compl. ¶218 Compl. ¶219
  • Accused Features: The complaint alleges on information and belief that Zenara's ANDA Products will infringe because their formulation will meet the claimed composition, though it notes Zenara has not disclosed the complete formulation Compl. ¶¶211-217

III. The Accused Instrumentality

Product Identification

The accused instrumentalities are Defendant Zenara's generic Maralixibat Chloride tablets in 10 mg, 15 mg, 20 mg, and 30 mg dosage strengths, for which Zenara submitted Abbreviated New Drug Application (ANDA) No. 221420 to the FDA Compl. ¶2 These are referred to as "Zenara's ANDA Products" Compl. ¶2

Functionality and Market Context

Zenara's ANDA Products are generic versions of Plaintiffs' LIVMARLI® (maralixibat) tablets and are intended for the same therapeutic uses Compl. ¶1 The complaint alleges that Zenara's proposed product label, which generally must be the same as the brand-name label, will instruct physicians and patients to use the generic tablets for treating cholestatic pruritus in patients with Alagille syndrome (ALGS) and for treating cholestatic pruritus in patients with progressive familial intrahepatic cholestasis (PFIC) Compl. ¶4 Compl. ¶71 By filing the ANDA with a Paragraph IV certification, Zenara seeks to gain FDA approval to market its generic products before the expiration of Plaintiffs' patents covering LIVMARLI® Compl. ¶1 Compl. ¶6 No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

’657 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A method for treating or ameliorating progressive familial intrahepatic cholestasis type 2 (PFIC2) in a pediatric subject in need thereof, The proposed labeling for Zenara's ANDA Products allegedly instructs and encourages use for treating pediatric PFIC, which includes the PFIC2 subtype. ¶75 col. 23:23-25
comprising administering to the pediatric subject an Apical Sodium-dependent Bile Acid Transporter Inhibitor (ASBTI), wherein the ASBTI is [maralixibat structure] or a pharmaceutically acceptable salt thereof, Zenara's ANDA Products contain maralixibat, which is the claimed ASBTI. ¶75 col. 145:25-50
wherein the ASBTI is effective for decreasing at least 20% of serum and/or hepatic bile acid levels in the pediatric subject as compared to bile acid levels prior to administration of the ASBTI. The use of Zenara's ANDA Products as directed by the proposed labeling allegedly meets the claimed efficacy requirement of decreasing bile acid levels by at least 20%. ¶75 col. 146:58-62

’647 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A method for treating Alagille Syndrome (ALGS) in a pediatric subject in need of such treatment The proposed labeling for Zenara's ANDA Products allegedly instructs and encourages use for treating ALGS in pediatric patients. ¶97 col. 17:15-17
comprising administering to the subject [maralixibat chloride structure], or a pharmaceutically acceptable alternative salt thereof, Zenara's ANDA Products contain maralixibat chloride, which is the claimed compound. ¶97 col. 137:5-20
wherein the maralixibat chloride is administered in an amount of from about 400 µg/kg/day to about 800 µg/kg/day. The proposed labeling for Zenara's ANDA Products allegedly instructs and encourages administration of maralixibat chloride in an amount that falls within the claimed dosage range. ¶97 col. 137:21-23

Identified Points of Contention

  • Evidentiary Questions: For the ’050 formulation patent, a primary dispute will concern access to information. Plaintiffs allege infringement "on information and belief" and note that Zenara's "Offer of Confidential Access" was inadequate to confirm the exact composition of the ANDA products Compl. ¶¶211-217 The infringement analysis for this patent will depend entirely on whether discovery reveals Zenara's formulation reads on the specific excipient and concentration limitations of the claims.
  • Scope Questions: In this Hatch-Waxman context, a core question for the method-of-use patents (e.g., ’657 and ’647) is whether the proposed label for Zenara’s ANDA Products will be found to induce infringement. This will involve an analysis of whether the label's language necessarily encourages, recommends, or promotes a use that falls within the scope of the patent claims, including the specified diseases (PFIC2, ALGS), patient populations ("pediatric subject"), and dosages.
  • Technical Questions: For the method patents, a potential point of contention may be whether the therapeutic outcomes described on the proposed label meet the functional limitations of the claims, such as the '657 Patent's requirement of "decreasing at least 20% of serum and/or hepatic bile acid levels." The parties may dispute whether the clinical data supporting the label is sufficient to establish this claimed effect for all intended uses.

V. Key Claim Terms for Construction

"treating or ameliorating"

  • The Term: "treating or ameliorating" (’657 Patent, claim 1)
  • Context and Importance: The definition of this term is fundamental to all asserted method-of-use claims. Its construction will determine the type and degree of therapeutic effect that must be instructed by the accused product's label to constitute infringement.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The patent specification provides a broad definition, stating the term includes "inhibiting the disease or condition, ... arresting the development of the disease or condition, relieving the disease or condition, ... or causing regression of the disease or condition" ’657 Patent, col. 83:11-23 This language may support an interpretation that does not require a complete cure or a specific threshold of symptom reduction.
    • Evidence for a Narrower Interpretation: A party may argue that the term should be interpreted in light of the clinical outcomes described in the patent's examples, potentially tying "treating" to achieving a statistically significant clinical endpoint. The patent also defines "effective amount" as an amount sufficient to achieve a "desired result," which could be argued to imply a higher standard of efficacy than merely inhibiting or slowing progression ’657 Patent, col. 85:15-25

"about"

  • The Term: "about" (e.g., ’647 Patent, claim 1, "about 400 µg/kg/day to about 800 µg/kg/day")
  • Context and Importance: The term "about" precedes the numerical dosage ranges in several key claims. Its interpretation is critical for determining the boundaries of the claimed dosage, and thus whether the dosage information on the accused product's label falls within the claim scope.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: Plaintiffs may argue that "about" should be given its ordinary meaning in the pharmaceutical arts, accounting for normal manufacturing and clinical variability. The specification uses "about" extensively when discussing dosages, suggesting it is intended to provide some flexibility around the stated numbers ’647 Patent, col. 82:25-68
    • Evidence for a Narrower Interpretation: A defendant may argue that the precision of the data in the patent's figures and examples warrants a narrow interpretation of "about." The patent defines "about" as encompassing a value that is "within 10% of the described value" ’657 Patent, col. 83:54-56 This explicit definition could be used to argue against any broader interpretation.

VI. Other Allegations

Indirect Infringement

Plaintiffs allege that Defendants will induce infringement of the method-of-use patents Compl. ¶81 Compl. ¶102 The basis for this allegation is that Defendants, with knowledge of the patents, will market their generic product with a proposed label that instructs and encourages physicians and patients to perform the patented methods of treatment Compl. ¶75 Compl. ¶97 It is also alleged that Zenara's ANDA Products lack substantial non-infringing uses Compl. ¶82 Compl. ¶103

Willful Infringement

Plaintiffs allege that Defendants' infringement has been and will be willful Compl. ¶84 Compl. ¶105 The complaint bases this on Defendants' alleged pre-suit knowledge of the asserted patents, evidenced by the patents' listing in the FDA's Orange Book and by Defendants' submission of a Paragraph IV certification specifically challenging those patents Compl. ¶29 Compl. ¶83 Compl. ¶104 Plaintiffs assert this conduct makes the case "exceptional," potentially warranting enhanced damages and attorneys' fees Compl. ¶84 Compl. ¶105

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

  • A core issue will be one of label-based infringement: Will the court find that the language on Defendant Zenara’s proposed product label—presumed to be substantially similar to the FDA-approved label for LIVMARLI®—actively encourages or instructs a method of use that meets all limitations of the asserted claims, including specific patient populations (e.g., "pediatric subject" with "PFIC2"), dosage ranges, and functional outcomes?
  • A second key issue will be evidentiary and compositional: For the ’050 formulation patent, the dispute hinges on a question of fact that can only be resolved through discovery. Does Zenara’s confidential ANDA formulation contain the specific excipients in the specific weight-percent ranges required by the patent’s claims, or does it utilize a different, non-infringing formulation?
  • Finally, the case will likely involve a significant dispute over patent validity. Although not fully detailed in the complaint, Zenara's Paragraph IV notice asserts the patents are invalid and/or unenforceable Compl. ¶5 A central question will be whether Zenara can demonstrate, by clear and convincing evidence, that the claimed methods and formulations were obvious or anticipated by prior art, particularly in the context of a dense patent portfolio covering a single therapeutic molecule.