DCT

1:26-cv-00986

Eli Lilly Co v. Rio Biopharma Inc

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:26-cv-00986, D. Del., 08/06/2026
  • Venue Allegations: Venue is alleged to be proper for Rio Biopharmaceuticals, Inc. as it is a Delaware corporation. For EMS S/A, a foreign corporation, venue is alleged to be proper in any judicial district.
  • Core Dispute: Plaintiff alleges that Defendants' submission of Abbreviated New Drug Applications (ANDAs) to the FDA for approval of generic versions of Mounjaro® and Zepbound® (tirzepatide) constitutes an act of infringement of ten U.S. patents covering the tirzepatide compound, its formulation, and methods of use.
  • Technical Context: The case concerns tirzepatide, a dual GIP and GLP-1 receptor co-agonist, which is a leading therapy for type 2 diabetes and chronic weight management.
  • Key Procedural History: This is a Hatch-Waxman action filed under 35 U.S.C. § 271(e)(2) following Plaintiff's receipt of Defendants' Paragraph IV certification notice letters. The letters assert that the asserted patents are invalid, unenforceable, and/or will not be infringed by Defendants' proposed generic products. The complaint was filed within 45 days of receiving the notice letters, which may trigger a 30-month statutory stay of FDA approval for Defendants' ANDAs. All asserted patents are listed in the FDA's Orange Book for Mounjaro® and/or Zepbound®.

Case Timeline

Date Event
2015-01-09 U.S. Patent No. 9,474,780 Priority Date
2016-10-25 U.S. Patent No. 9,474,780 Issues
2018-06-22 U.S. Patent Nos. 11,357,820; 11,918,623; 12,453,755; 12,453,756; 12,629,404 Priority Date
2018-07-23 U.S. Patent Nos. 12,295,987; 12,343,382; 12,453,758; 12,616,740 Priority Date
2022-05-13 Mounjaro® (tirzepatide) FDA Approval Date
2022-06-14 U.S. Patent No. 11,357,820 Issues
2023-11-08 Zepbound® (tirzepatide) FDA Approval Date
2024-03-05 U.S. Patent No. 11,918,623 Issues
2025-05-13 U.S. Patent No. 12,295,987 Issues
2025-07-01 U.S. Patent No. 12,343,382 Issues
2025-10-28 U.S. Patent Nos. 12,453,755; 12,453,756; 12,453,758 Issue
2026-05-05 U.S. Patent No. 12,616,740 Issues
2026-05-19 U.S. Patent No. 12,629,404 Issues
2026-07-09 Plaintiff receives Defendants' ANDA Notice Letters
2026-08-06 Complaint Filing Date

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

U.S. Patent No. 9,474,780 - "GIP and GLP-1 Co-agonist Compounds"

  • Issued: October 25, 2016

The Invention Explained

  • Problem Addressed: The patent describes the need for improved treatments for type 2 diabetes mellitus (T2D), noting that many patients remain inadequately controlled on existing therapies U.S. Patent No. 9,474,780, col. 1:12-18 It also notes the adverse side effects of GLP-1 analogues, such as nausea and vomiting, that limit dosing U.S. Patent No. 9,474,780, col. 1:36-40
  • The Patented Solution: The patent discloses novel peptide compounds that are dual agonists for both the GIP and GLP-1 receptors U.S. Patent No. 9,474,780, col. 1:4-8 By combining the activity of two different incretin hormones (GIP and GLP-1), the invention aims to provide enhanced glycemic control and potential for weight loss U.S. Patent No. 9,474,780, col. 2:25-33 The claimed compounds include specific amino acid substitutions and a fatty acid moiety to achieve a balanced receptor activity profile and a longer half-life suitable for less frequent administration U.S. Patent No. 9,474,780, col. 2:5-11
  • Technical Importance: The development of a single molecule that effectively agonizes both GIP and GLP-1 receptors represented a novel therapeutic approach for T2D, potentially offering superior efficacy compared to therapies targeting only a single incretin pathway.

Key Claims at a Glance

  • The complaint asserts at least independent claim 1 Compl. ¶56
  • Claim 1 recites:
    • A compound of Formula: YX1EGTFTSDYSIX2LDKIAQKAX3VQWLIAGGPSSGAPPPS;
    • wherein X1 is Aib;
    • X2 is Aib;
    • K at position 20 is chemically modified through conjugation to the epsilon-amino group of the K side-chain with ([2-(2-Amino-ethoxy)-ethoxy]-acetyl)2-(yGlu)a-CO-(CH2)b-CO2H wherein a is 1 to 2 and b is 10 to 20;
    • X3 is Phe or 1-Nal;
    • and the C-terminal amino acid is optionally amidated as a C-terminal primary amide (SEQ ID NO: 11), or a pharmaceutically acceptable salt thereof.

U.S. Patent No. 11,357,820 - "GIP/GLP1 Agonist Compositions"

  • Issued: June 14, 2022

The Invention Explained

  • Problem Addressed: The patent addresses the need for a pharmaceutical composition of the GIP/GLP1 co-agonist peptide tirzepatide that provides acceptable shelf-life stability and is associated with an acceptable patient injection site experience '820 Patent, col. 1:21-25 The background notes that certain common excipients, such as citrate, have been associated with painful stinging at the injection site '820 Patent, col. 3:9-13
  • The Patented Solution: The patent discloses a specific aqueous formulation for tirzepatide intended for subcutaneous injection '820 Patent, col. 1:3-5 The solution comprises tirzepatide, sodium chloride (NaCl) as a tonicity-adjusting agent, and dibasic sodium phosphate as a buffer '820 Patent, col. 1:25-29 This particular combination of excipients is described as providing the desired stability while ensuring an "acceptable patient injection site experience" '820 Patent, col. 3:25-33
  • Technical Importance: Creating a stable, injectable formulation for a complex biologic that is also well-tolerated by patients (i.e., minimizes pain upon injection) is a critical and non-trivial step in pharmaceutical development, directly impacting patient compliance and a product's commercial success.

Key Claims at a Glance

  • The complaint asserts at least independent claim 1 Compl. ¶73
  • Claim 1 recites:
    • A pharmaceutical composition comprising tirzepatide, or a pharmaceutically acceptable salt thereof;
    • NaCl at a concentration from 6.2 mg/mL to 9.5 mg/mL; and
    • dibasic sodium phosphate.

Multi-Patent Capsules

  • Patent Identification: U.S. Patent No. 11,918,623 ("the '623 Patent"), "GIP/GLP1 Agonist Compositions," issued March 5, 2024.

  • Technology Synopsis: The patent claims a method of treating obesity by administering a specific pharmaceutical formulation of tirzepatide. The formulation is defined by concentration ranges for tirzepatide and several excipients, including dibasic sodium phosphate and NaCl '623 Patent, col. 9:40-52

  • Asserted Claims: Independent claim 1 Compl. ¶90

  • Accused Features: The proposed labeling for Defendants' Proposed ANDA No. 220816 Product, which allegedly instructs and encourages treating obesity with a pharmaceutical composition that infringes the claim Compl. ¶91

  • Patent Identification: U.S. Patent No. 12,295,987 ("the '987 Patent"), "Methods of Using a GIP/GLP1 Co-agonist for Diabetes," issued May 13, 2025.

  • Technology Synopsis: The patent claims a method of treating type 2 diabetes using a specific four-step dose-escalation regimen. The method involves administering a GIP:GLP-1 peptide with a defined potency ratio in four sequential doses, with the first three doses being specific percentages of the fourth dose '987 Patent, col. 21:1-19

  • Asserted Claims: Independent claim 1 Compl. ¶109

  • Accused Features: The proposed labeling for Defendants' Proposed ANDA No. 219641 Product, which allegedly instructs and encourages the claimed dose-titration method for treating type 2 diabetes Compl. ¶110

  • Patent Identification: U.S. Patent No. 12,343,382 ("the '382 Patent"), "Methods of Using a GIP/GLP1 Co-agonist for Therapy," issued July 1, 2025.

  • Technology Synopsis: The patent claims methods for treating type 2 diabetes and for improving weight management. The methods comprise administering specific weekly "escalation doses" followed by specific "maintenance doses" of tirzepatide '382 Patent, col. 25:61-27:8

  • Asserted Claims: Independent claims 1 and 11 (Compl. ¶¶128; Compl. ¶130).

  • Accused Features: The proposed labeling for Defendants' Proposed ANDA Products, which allegedly instructs and encourages the claimed dosing regimens for treating type 2 diabetes and improving weight management (Compl. ¶¶129; Compl. ¶131).

  • Patent Identification: U.S. Patent No. 12,453,755 ("the '755 Patent"), "GIP/GLP1 Agonist Compositions," issued October 28, 2025.

  • Technology Synopsis: The patent claims a method of treating diabetes by administering a specific pharmaceutical formulation of tirzepatide. The formulation is defined by concentration ranges for tirzepatide and its excipients, including dibasic sodium phosphate, NaCl, and phenol '755 Patent, col. 9:43-54

  • Asserted Claims: Independent claim 1 Compl. ¶151

  • Accused Features: The proposed labeling for Defendants' Proposed ANDA No. 219641 Product, which allegedly instructs for the treatment of diabetes using a pharmaceutical composition that infringes the claim Compl. ¶152

  • Patent Identification: U.S. Patent No. 12,453,756 ("the '756 Patent"), "GIP/GLP1 Agonist Compositions," issued October 28, 2025.

  • Technology Synopsis: The patent claims a pharmaceutical composition of tirzepatide defined by a specific concentration range for NaCl and a specific pH range '756 Patent, col. 9:28-34

  • Asserted Claims: Independent claim 1 Compl. ¶170

  • Accused Features: Defendants' Proposed ANDA Products themselves, which are alleged to be pharmaceutical compositions that meet the limitations of the claim Compl. ¶171

  • Patent Identification: U.S. Patent No. 12,453,758 ("the '758 Patent"), "Methods of Using a GIP/GLP1 Co-agonist for Diabetes," issued October 28, 2025.

  • Technology Synopsis: The patent claims a method for improving weight management in a patient by administering a GIP:GLP-1 peptide with a specific potency ratio. The method involves a four-step dose-escalation regimen where the first three doses are defined percentages of the fourth dose '758 Patent, col. 37:55-38:1

  • Asserted Claims: Independent claim 1 Compl. ¶187

  • Accused Features: The proposed labeling for Defendants' Proposed ANDA No. 220816 Product, which allegedly instructs and encourages the claimed dosing regimen for improving weight management Compl. ¶188

  • Patent Identification: U.S. Patent No. 12,616,740 ("the '740 Patent"), "Methods of Using a GIP/GLP-1 Co-agonist for Therapy," issued May 5, 2026.

  • Technology Synopsis: The patent claims methods for treating type 2 diabetes and obesity by administering tirzepatide in a specific once-weekly dosing regimen. The regimen involves a 2.5 mg starting dose for four weeks, followed by 2.5 mg incremental increases to reach a maintenance dose of 5, 10, or 15 mg '740 Patent, col. 63:6-26

  • Asserted Claims: Independent claims 1 and 6 (Compl. ¶¶206; Compl. ¶208).

  • Accused Features: The proposed labeling for Defendants' Proposed ANDA Products, which allegedly instructs and encourages the claimed dosing regimens for treating type 2 diabetes and obesity (Compl. ¶¶207; Compl. ¶209).

  • Patent Identification: U.S. Patent No. 12,629,404 ("the '404 Patent"), "GIP/GLP1 Agonist Compositions," issued May 19, 2026.

  • Technology Synopsis: The patent claims a pharmaceutical composition of tirzepatide that is defined by being "free of preservative" and having specific NaCl concentration and pH ranges '404 Patent, col. 9:48-55

  • Asserted Claims: Independent claim 1 Compl. ¶229

  • Accused Features: Defendants' Proposed ANDA Products themselves, which are alleged to be pharmaceutical compositions that meet the limitations of the claim Compl. ¶230

III. The Accused Instrumentality

Product Identification

Defendants' proposed generic versions of Mounjaro® and Zepbound® autoinjectors, which are the subjects of Abbreviated New Drug Application (ANDA) Nos. 219641 and 220816 (collectively, the "Proposed ANDA Products") Compl. ¶1

Functionality and Market Context

The Proposed ANDA Products contain tirzepatide as the active pharmaceutical ingredient Compl. ¶50 They are intended to be generic equivalents to Lilly's branded Mounjaro® and Zepbound® products and are seeking approval for the same indications, including to improve glycemic control in adults with type 2 diabetes and to aid in chronic weight management Compl. ¶1 The products are formulated as sterile solutions for subcutaneous use in various strengths from 2.5 mg/0.5 mL to 15 mg/0.5 mL Compl. ¶1 The complaint alleges that the Defendants' ANDA filings contain data to demonstrate bioequivalence to Lilly's products Compl. ¶51 The complaint provides a visual representation of the chemical structure of tirzepatide, which it alleges is the active ingredient in the Proposed ANDA Products Compl. p. 11

IV. Analysis of Infringement Allegations

U.S. Patent No. 9,474,780 Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A compound of Formula: YX1EGTFTSDYSIX2LDKIAQKAX3VQWLIAGGPSSGAPPPS...or a pharmaceutically acceptable salt thereof. The Proposed ANDA Products contain tirzepatide, which is alleged to be a compound with the structural formula corresponding to the claim. ¶57 col. 4:51-64
wherein X1 is Aib; X2 is Aib; The tirzepatide in the Proposed ANDA Products has Aib at positions 2 and 13. ¶57 col. 4:52-53
K at position 20 is chemically modified through conjugation to the epsilon-amino group of the K side-chain with ([2-(2-Amino-ethoxy)-ethoxy]-acetyl)2-(yGlu)a-CO-(CH2)b-CO2H wherein a is 1 to 2 and b is 10 to 20; The tirzepatide in the Proposed ANDA Products has the specified chemical modification at the lysine (K) at position 20. ¶57 col. 3:60-67
X3 is Phe or 1-Nal; The complaint does not specify whether X3 is Phe or 1-Nal in the accused product but implies it is one of the two. ¶56 col. 4:60-61
and the C-terminal amino acid is optionally amidated as a C-terminal primary amide (SEQ ID NO: 11) The tirzepatide in the Proposed ANDA Products has an amidated C-terminus. ¶57 col. 4:62-64
  • Identified Points of Contention:
    • Scope Questions: The primary question for the court will likely be one of validity, as the complaint alleges direct structural identity between the accused compound (tirzepatide) and the claimed formula. However, a potential infringement dispute could arise over whether any minor variations in Defendants' manufacturing process result in a compound that falls outside the literal scope of the claims, raising questions for analysis under the doctrine of equivalents.
    • Technical Questions: Does the specific side-chain in Defendants' tirzepatide have variables "a" and "b" that fall within the claimed ranges of "1 to 2" and "10 to 20", respectively? The complaint alleges structural correspondence, but this could become a point of factual dispute requiring detailed chemical analysis.

U.S. Patent No. 11,357,820 Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A pharmaceutical composition comprising tirzepatide, or a pharmaceutically acceptable salt thereof; Defendants' Proposed ANDA Products are pharmaceutical compositions that comprise tirzepatide. ¶74 col. 10:1-3
NaCl at a concentration from 6.2 mg/mL to 9.5 mg/mL; The Proposed ANDA Products are alleged to contain NaCl at a concentration within the claimed range. ¶74 col. 10:4-5
and dibasic sodium phosphate. The Proposed ANDA Products are alleged to contain dibasic sodium phosphate. ¶74 col. 10:6-6
  • Identified Points of Contention:
    • Scope Questions: A central question may be the interpretation of "dibasic sodium phosphate." The court may need to determine if this term is limited to a specific form (e.g., heptahydrate, as mentioned in the description of Lilly's own product) or if it covers any form of the chemical, which could be dispositive if Defendants use a different salt form '820 Patent, col. 1:7 Compl. ¶7
    • Technical Questions: The infringement analysis will depend on the precise formulation of the Proposed ANDA Products. A key evidentiary question for the court will be whether the concentration of NaCl in Defendants' formulation, as disclosed in their ANDA, falls squarely within the claimed range of "from 6.2 mg/mL to 9.5 mg/mL."

V. Key Claim Terms for Construction

For the '780 Patent:

  • The Term: "A compound of Formula: YX1EGTFTSDYSIX2LDKIAQKAX3VQWLIAGGPSSGAPPPS..."
  • Context and Importance: This term defines the entire chemical structure of the active ingredient. Its construction is dispositive for infringement. Practitioners may focus on this term because any deviation in the accused compound from this precise formula, including the specific amino acids, modifications, and side-chain structure, could form the basis of a non-infringement argument.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The claim language "or a pharmaceutically acceptable salt thereof" suggests the claim is not limited to the exact molecule but also covers its various salt forms, broadening the potential scope U.S. Patent No. 9,474,780, col. 10:55-57
    • Evidence for a Narrower Interpretation: Example 1 of the patent provides a detailed synthesis of a specific embodiment, tirzepatide, which has a defined structure where "a" is 1 and "b" is 18 U.S. Patent No. 9,474,780, col. 18:22-29 A party could argue that the invention is properly limited to the specific structures disclosed and enabled, not hypothetical variations within the claimed ranges.

For the '820 Patent:

  • The Term: "dibasic sodium phosphate"
  • Context and Importance: This term identifies a key buffering agent in the claimed formulation. Its definition is critical because if it is construed narrowly to a specific hydrate form, Defendants could potentially design around the patent by using a different form. Practitioners may focus on this term because pharmaceutical claims often succeed or fail on such precise definitions of excipients.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The claim itself simply recites "dibasic sodium phosphate" without specifying a hydrate form, which may support a construction covering any chemical form that functions as dibasic sodium phosphate '820 Patent, col. 10:6
    • Evidence for a Narrower Interpretation: The detailed description, when discussing Lilly's own product formulation, specifies "sodium phosphate dibasic heptahydrate" Compl. ¶7 While not from the patent itself, this real-world product information, if incorporated into the patent's context, might be used to argue that the inventors contemplated a specific hydrated form. The specification of the '820 Patent also mentions "dibasic sodium phosphate 7H2O" in a table detailing a sample formulation, which may support a narrower interpretation '820 Patent, Table 3, col. 5

VI. Other Allegations

  • Indirect Infringement: The complaint alleges active inducement of infringement for the method patents, stating that Defendants' proposed product labeling will instruct and encourage physicians and patients to administer the Proposed ANDA Products in a manner that directly infringes the claimed methods of treatment and dosing regimens (Compl. ¶¶66; Compl. ¶83; Compl. ¶100; Compl. ¶119; Compl. ¶140; Compl. ¶161; Compl. ¶180; Compl. ¶197; Compl. ¶218; Compl. ¶239). The complaint also alleges contributory infringement, asserting that Defendants know their products are especially made or adapted for use in the patented methods and are not suitable for substantial noninfringing use (Compl. ¶¶67; Compl. ¶84; Compl. ¶103; Compl. ¶122; Compl. ¶145; Compl. ¶164; Compl. ¶181; Compl. ¶200; Compl. ¶223; Compl. ¶240).
  • Willful Infringement: The complaint does not use the word "willful." However, it alleges that Defendants had knowledge of the asserted patents prior to litigation, at least due to their listing in the FDA's Orange Book and their inclusion in Defendants' own notice letters (Compl. ¶¶65; Compl. ¶82; Compl. ¶99; Compl. ¶118; Compl. ¶139; Compl. ¶160; Compl. ¶179; Compl. ¶196; Compl. ¶217; Compl. ¶238). These allegations of pre-suit knowledge may serve as a basis for a later claim of willfulness or a request for enhanced damages.

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

  • A primary issue will be one of claim scope and formulation: For the composition patents, can Plaintiff prove that the precise concentrations and forms of the excipients (e.g., NaCl, dibasic sodium phosphate) in Defendants' proposed generic products fall within the literal scope of the patent claims, or will the analysis turn on functional equivalence?
  • A central question of inducement will drive the method-of-use patent analysis: Will Defendants' proposed product labeling be found to contain instructions that actively encourage or teach medical professionals and patients to perform the specific dose-escalation and administration steps required by Plaintiff's method claims?
  • The litigation will also serve as a forum to test the validity of the asserted patents, a question initiated by Defendants' Paragraph IV certifications. The court will be tasked with evaluating whether the claimed compound, compositions, and methods are novel and non-obvious over the prior art, which will be a central battleground of the case.
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