DCT

1:26-cv-00984

Eli Lilly & Co v. Macleods Pharma Ltd

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:26-cv-00984, D. Del., 08/06/2026
  • Venue Allegations: Venue is alleged to be proper as to Macleods Pharmaceuticals Limited because it is a foreign corporation, and as to Macleods Pharma USA, Inc. because it is a Delaware corporation and therefore resides in the district.
  • Core Dispute: Plaintiff alleges that Defendants' submission of Abbreviated New Drug Applications (ANDAs) to the FDA for generic versions of the drugs Mounjaro® and Zepbound® constitutes an act of infringement of nine U.S. patents covering pharmaceutical compositions of the active ingredient tirzepatide and methods of its use.
  • Technical Context: The technology relates to GIP/GLP-1 co-agonist peptide compositions, specifically tirzepatide, used for treating type 2 diabetes, obesity, and related metabolic conditions, a class of drugs with significant market presence.
  • Key Procedural History: The action arises under the Hatch-Waxman Act, triggered by Defendants' submission of ANDA Nos. 221768 and 221771 with Paragraph IV certifications asserting that Plaintiff's patents are invalid, unenforceable, or will not be infringed by the proposed generic products. All asserted patents are listed in the FDA's Orange Book for Mounjaro® and/or Zepbound®.

Case Timeline

Date Event
2018-06-22 Earliest Priority Date for '820 Patent and '623 Patent
2018-07-23 Earliest Priority Date for '987 Patent
2022-05-13 FDA grants approval for Mounjaro® (tirzepatide)
2022-06-14 '820 Patent Issued
2023-11-08 FDA grants approval for Zepbound® (tirzepatide)
2024-03-05 '623 Patent Issued
2025-05-13 '987 Patent Issued
2025-07-01 '382 Patent Issued
2025-10-28 '755 Patent Issued
2025-10-28 '756 Patent Issued
2025-10-28 '758 Patent Issued
2026-05-05 '740 Patent Issued
2026-05-19 '404 Patent Issued
2026-06-26 Date of first of Defendants' Notice Letters
2026-08-06 Complaint Filing Date

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

U.S. Patent No. 11,357,820 - "GIP/GLP1 AGONIST COMPOSITIONS," Issued June 14, 2022

The Invention Explained

  • Problem Addressed: The patent describes the need for a pharmaceutical composition of tirzepatide, a GIP/GLP1 co-agonist peptide, that is suitable for subcutaneous injection and provides an "acceptable patient injection site experience" Compl. ¶26 '820 Patent, col. 4:5-22 Specifically, it notes that certain agents used in injectable formulations, such as NaCl and citrate, can be associated with painful stinging at the injection site '820 Patent, col. 4:8-12
  • The Patented Solution: The invention is a specific aqueous pharmaceutical composition that includes tirzepatide, dibasic sodium phosphate as a buffer, and an agent selected from NaCl or propylene glycol to ensure stability and patient comfort '820 Patent, abstract '820 Patent, col. 1:20-30 This combination is described as providing both desired shelf-life stability and an acceptable patient experience upon injection '820 Patent, col. 4:45-52
  • Technical Importance: For a chronically administered injectable drug like tirzepatide, creating a formulation that is both stable for storage and minimally painful upon injection is crucial for patient compliance and commercial viability.

Key Claims at a Glance

  • The complaint asserts at least independent claim 1 Compl. ¶55
  • The essential elements of Claim 1 are:
    • 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.
  • The complaint alleges infringement of "one or more claims of the '820 Patent, including at least claim 1" Compl. ¶57

U.S. Patent No. 11,918,623 - "GIP/GLP1 AGONIST COMPOSITIONS," Issued March 5, 2024

The Invention Explained

  • Problem Addressed: As a continuation-in-part of the application leading to the '820 Patent, this patent addresses the same fundamental problem: developing a stable and patient-tolerable formulation of tirzepatide '623 Patent, col. 1:3-12 It also frames this problem in the context of treating diabetes and obesity '623 Patent, col. 1:31-41
  • The Patented Solution: The patent claims a method of treating obesity by administering a specific pharmaceutical composition containing tirzepatide. The composition includes defined concentration ranges for tirzepatide, dibasic sodium phosphate, NaCl, and optionally phenol as a preservative '623 Patent, claim 1
  • Technical Importance: The invention protects a specific method of using a defined tirzepatide formulation to treat obesity, a condition with significant unmet medical needs.

Key Claims at a Glance

  • The complaint asserts at least independent claim 1 Compl. ¶71
  • The essential elements of Claim 1 are:
    • A method of treating obesity comprising administering to a human in need thereof an effective dose of a pharmaceutical composition comprising tirzepatide, or a pharmaceutically acceptable salt thereof,
    • wherein the tirzepatide concentration is from about 5 mg/mL to about 30 mg/mL;
    • dibasic sodium phosphate is from about 0.67 to about 2.68 mg/mL;
    • NaCl at a concentration from about 6.2 mg/mL to about 9.5 mg/mL; and
    • optionally comprising from about 3.0 mg/mL to about 7.0 mg/mL phenol.
  • The complaint alleges infringement of "one or more claims of the '623 Patent, including at least claim 1" Compl. ¶72

U.S. Patent No. 12,295,987 - "Methods of Using a GIP/GLP1 Co-agonist for Diabetes," Issued May 13, 2025

  • Patent Identification: U.S. Patent No. 12,295,987, "Methods of Using a GIP/GLP1 Co-agonist for Diabetes," Issued May 13, 2025 Compl. ¶30
  • Technology Synopsis: The patent claims a method of treating type 2 diabetes by administering a GIP:GLP-1 peptide with a specific agonist potency ratio. The method involves a specific four-dose titration schedule, where the first dose is about 25% of the fourth dose, the second is 50%, and the third is 75% Compl. ¶89
  • Asserted Claims: At least independent claim 1 Compl. ¶90
  • Accused Features: Defendants' proposed product labeling allegedly instructs and encourages treating type 2 diabetes using the claimed peptide and dosing regimen Compl. ¶90

U.S. Patent No. 12,343,382 - "Methods of Using a GIP/GLP1 Co-agonist for Therapy," Issued July 1, 2025

  • Patent Identification: U.S. Patent No. 12,343,382, "Methods of Using a GIP/GLP1 Co-agonist for Therapy," Issued July 1, 2025 Compl. ¶32
  • Technology Synopsis: The patent covers methods for treating type 2 diabetes and for improving weight management. The methods involve administering specific "escalation" doses (e.g., 2.5 mg, 7.5 mg, 12.5 mg) followed by specific "maintenance" doses (e.g., 5.0 mg, 10.0 mg, 15.0 mg) of tirzepatide Compl. ¶108 Compl. ¶110
  • Asserted Claims: At least independent claims 1 and 11 Compl. ¶109 Compl. ¶111
  • Accused Features: Defendants' proposed labeling for their generic products allegedly instructs and encourages the use of the claimed dose escalation and maintenance schedules for treating type 2 diabetes and improving weight management Compl. ¶109 Compl. ¶111

U.S. Patent No. 12,453,755 - "GIP/GLP1 Agonist Compositions," Issued October 28, 2025

  • Patent Identification: U.S. Patent No. 12,453,755, "GIP/GLP1 Agonist Compositions," Issued October 28, 2025 Compl. ¶34
  • Technology Synopsis: This patent claims a method for treating diabetes by administering a pharmaceutical composition with specific concentration ranges for tirzepatide, dibasic sodium phosphate, NaCl, and optional phenol Compl. ¶131 The claimed composition is similar to that in the '623 Patent.
  • Asserted Claims: At least independent claim 1 Compl. ¶132
  • Accused Features: Defendants' proposed labeling allegedly instructs and encourages treating diabetes by administering a composition matching the one claimed Compl. ¶132

U.S. Patent No. 12,453,756 - "GIP/GLP1 Agonist Compositions," Issued October 28, 2025

  • Patent Identification: U.S. Patent No. 12,453,756, "GIP/GLP1 Agonist Compositions," Issued October 28, 2025 Compl. ¶36
  • Technology Synopsis: This patent claims a pharmaceutical composition comprising tirzepatide and a specific concentration range of NaCl, where the composition has a pH of about 6.5 to 7.5 Compl. ¶149
  • Asserted Claims: At least independent claim 1 Compl. ¶150
  • Accused Features: Defendants' Proposed ANDA Products are alleged to be pharmaceutical compositions that meet the claimed elements, including the tirzepatide, NaCl concentration, and pH range Compl. ¶150

U.S. Patent No. 12,453,758 - "Methods of Using a GIP/GLP1 Co-agonist for Diabetes," Issued October 28, 2025

  • Patent Identification: U.S. Patent No. 12,453,758, "Methods of Using a GIP/GLP1 Co-agonist for Diabetes," Issued October 28, 2025 Compl. ¶38
  • Technology Synopsis: The patent claims a method for improving weight management using a GIP:GLP-1 peptide with a specific agonist potency ratio. The method specifies a four-dose titration schedule similar to that in the '987 Patent Compl. ¶166
  • Asserted Claims: At least independent claim 1 Compl. ¶167
  • Accused Features: Defendants' proposed labeling allegedly instructs and encourages the claimed dosing regimen for improving weight management Compl. ¶167

U.S. Patent No. 12,616,740 - "Methods of Using a GIP/GLP1 Co-agonist for Therapy," Issued May 5, 2026

  • Patent Identification: U.S. Patent No. 12,616,740, "Methods of Using a GIP/GLP1 Co-agonist for Therapy," Issued May 5, 2026 Compl. ¶40
  • Technology Synopsis: The patent claims methods for treating type 2 diabetes and obesity by administering tirzepatide in a specific once-weekly dose escalation regimen: starting at 2.5 mg for four weeks, increasing by 2.5 mg increments, with each increased dose administered for at least four weeks, up to a maintenance dose of 5, 10, or 15 mg Compl. ¶185 Compl. ¶187
  • Asserted Claims: At least independent claims 1 and 6 Compl. ¶186 Compl. ¶188
  • Accused Features: Defendants' proposed labeling allegedly instructs and encourages the use of the claimed dose escalation regimen for treating diabetes and obesity Compl. ¶186 Compl. ¶188

U.S. Patent No. 12,629,404 - "GIP/GLP1 Agonist Compositions," Issued May 19, 2026

  • Patent Identification: U.S. Patent No. 12,629,404, "GIP/GLP1 Agonist Compositions," Issued May 19, 2026 Compl. ¶42
  • Technology Synopsis: This patent claims a pharmaceutical composition that is explicitly "free of preservative" and comprises tirzepatide, a specific concentration range of NaCl, and has a pH of about 6.5 to 7.5 Compl. ¶208
  • Asserted Claims: At least independent claim 1 Compl. ¶209
  • Accused Features: Defendants' Proposed ANDA Products are alleged to be pharmaceutical compositions that meet the claimed elements, including being preservative-free Compl. ¶209

III. The Accused Instrumentality

Product Identification

  • Defendants' "Proposed ANDA Products" are generic versions of Mounjaro® (tirzepatide) and Zepbound® (tirzepatide) in various dosage strengths, formulated in autoinjectors and KwikPens Compl. ¶1

Functionality and Market Context

  • The Proposed ANDA Products are described as sterile, injectable solutions containing tirzepatide as the active pharmaceutical ingredient Compl. ¶23 Compl. ¶49 Tirzepatide is a GIP and GLP-1 receptor agonist used as an adjunct to diet and exercise for several indications, including improving glycemic control in type 2 diabetes, long-term weight management, and treating obstructive sleep apnea Compl. ¶1 Compl. ¶2 Compl. ¶22
  • The complaint alleges that Defendants' ANDAs rely on Lilly's original New Drug Applications (NDAs) and contain data demonstrating bioequivalence to Mounjaro® and Zepbound® Compl. ¶50 The products are intended to be marketed as direct competitors to Lilly's branded drugs upon FDA approval Compl. ¶2
  • No probative visual evidence provided in complaint.

IV. Analysis of Infringement Allegations

'820 Patent 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. ¶56 col. 1:20-23
NaCl at a concentration from 6.2 mg/mL to 9.5 mg/mL; The Proposed ANDA Products allegedly contain NaCl within the claimed concentration range. ¶56 col. 2:4-7
and dibasic sodium phosphate. The Proposed ANDA Products allegedly contain dibasic sodium phosphate or an equivalent thereof. ¶56 col. 1:20-23
  • Identified Points of Contention:
    • Scope Question: The complaint alleges the accused products contain "dibasic sodium phosphate or equivalent thereof" (Compl. ¶56). Claim 1 of the '820 Patent, however, recites only "dibasic sodium phosphate" '820 Patent, claim 1 This raises the question of whether Defendants' formulation uses a different phosphate buffer, which would make infringement analysis dependent on the doctrine of equivalents rather than literal infringement.
    • Factual Question: The infringement analysis will depend on whether the precise concentration of NaCl in Defendants' final, as-marketed product falls within the claimed range of 6.2 mg/mL to 9.5 mg/mL.

'623 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A method of treating obesity comprising administering to a human in need thereof an effective dose of a pharmaceutical composition comprising tirzepatide... Defendants' proposed labeling allegedly "instructs and encourages treating obesity by administering to a human in need thereof" the claimed composition. ¶72 col. 3:5-7
wherein the tirzepatide concentration is from about 5 mg/mL to about 30 mg/mL; The proposed product composition allegedly has a tirzepatide concentration within this range. ¶72 col. 2:20-22
dibasic sodium phosphate is from about 0.67 to about 2.68 mg/mL; The proposed product composition allegedly has a dibasic sodium phosphate concentration within this range, or an equivalent. ¶72 col. 2:2-4
NaCl at a concentration from about 6.2 mg/mL to about 9.5 mg/mL; The proposed product composition allegedly has a NaCl concentration within this range. ¶72 col. 1:66-67
and optionally comprising from about 3.0 mg/mL to about 7.0 mg/mL phenol. The proposed product composition allegedly contains phenol within this optional range. ¶72 col. 2:40-42
  • Identified Points of Contention:
    • Technical Question: As a method claim, infringement hinges on induced infringement. The central issue will be whether the language in Defendants' proposed product label is specific enough to encourage, recommend, or promote the administration of the product for the purpose of "treating obesity" as claimed.
    • Scope Questions: The claim uses the term "about" for all concentration ranges. The construction of "about" will be critical in determining the scope of the claims and whether Defendants' formulation, if its concentrations are close to but outside the specified numbers, literally infringes. Similar to the '820 Patent, the allegation of an "equivalent" to dibasic sodium phosphate suggests a potential dispute under the doctrine of equivalents Compl. ¶72

V. Key Claim Terms for Construction

  • Term 1 ('820 Patent): dibasic sodium phosphate

    • Context and Importance: This term is a key excipient in the claimed formulation. The complaint's allegation that the accused products contain "dibasic sodium phosphate or equivalent thereof" suggests the Defendants may use a different but functionally similar buffering agent (Compl. ¶56). The construction of this term, and its potential equivalents, is therefore central to the infringement analysis.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The specification describes the role of dibasic sodium phosphate as a component of a "buffer solution" to maintain a desired pH, a functional description that could support arguments for the equivalence of other phosphate-based buffering agents that achieve the same pH stability ('820 Patent, col. 4:31-33).
      • Evidence for a Narrower Interpretation: The patent claims, abstract, and examples consistently and specifically name "dibasic sodium phosphate" without listing alternative buffers '820 Patent, abstract '820 Patent, claim 1 This specificity may support an argument that the inventors intended to limit the claim to this exact compound.

  • Term 2 ('623 Patent): about

    • Context and Importance: This term precedes every concentration range in claim 1 of the '623 patent. Its interpretation will determine the literal scope of the claimed ranges. Practitioners may focus on this term because if the accused product's formulation falls near, but not exactly within, the recited numerical limits, the meaning of "about" will be dispositive for literal infringement.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The specification repeatedly uses "about" when describing concentrations, which may indicate that the inventors intended the numerical values to be approximations rather than strict limits '623 Patent, col. 2:2-4 '623 Patent, col. 2:40-42
      • Evidence for a Narrower Interpretation: The patent provides tables with specific, precise concentration values for exemplary formulations (e.g., NaCl at 8.8 mg/mL) ('623 Patent, Table 5). This data could be used to argue that the scope of "about" should be narrowly construed in light of the precision demonstrated in the patent's own examples.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges both induced and contributory infringement for the asserted patents.
    • Inducement: The inducement theory is based on the allegation that Defendants' proposed product labeling will instruct and encourage healthcare providers and patients to administer the generic products in a manner that directly infringes the method-of-use claims (e.g., for treating obesity or using specific dosing schedules) (Compl. ¶¶64, 80-82, 99-101).
    • Contributory: The contributory infringement theory is based on the allegation that the Proposed ANDA Products are especially made for use in the patented methods and are not suitable for substantial non-infringing uses (Compl. ¶¶65, 83, 102).
  • Willful Infringement: The complaint does not use the term "willful," but it lays a foundation for such a claim by alleging pre-suit knowledge. It asserts that Defendants were aware of the patents because they are listed in the FDA's Orange Book and because Defendants themselves included the patents in their Paragraph IV certification notice letters sent to Lilly (Compl. ¶¶63, 79, 98).

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

  1. A core issue will be one of compositional infringement: Do Defendants' proposed generic products contain the exact formulation claimed in patents like the '820 and '404 Patents, or will the dispute center on whether different excipients used by the Defendants are "equivalents" under the doctrine of equivalents?
  2. A central question will be one of induced infringement: For the numerous method-of-use patents, does the language in Defendants' proposed drug label provide sufficiently explicit instructions and encouragement to cause healthcare providers and patients to practice the specific dosing regimens for treating diabetes and obesity as claimed in the patents?
  3. A key legal question will be one of claim scope: How broadly will the court construe the term "about" as it applies to the concentration ranges in the composition and method claims, and will this construction be broad enough to capture Defendants' specific formulations?
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