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., 09/09/2026
  • Venue Allegations: Venue is alleged to be proper in the District of Delaware because Macleods Pharmaceuticals Limited is a foreign corporation that may be sued in any judicial district, and Macleods Pharma USA, Inc. is a Delaware corporation that resides in the district for venue purposes.
  • Core Dispute: Plaintiff alleges that Defendants' Abbreviated New Drug Applications (ANDAs) to market generic versions of Mounjaro® and Zepbound® (tirzepatide) constitute an act of infringement of nine U.S. patents covering tirzepatide compositions and methods of use.
  • Technical Context: The technology relates to tirzepatide, a dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist for treating type 2 diabetes and obesity.
  • Key Procedural History: This is a Hatch-Waxman action filed in response to Defendants' submission of ANDA Nos. 221768 and 221771, which included Paragraph IV certifications asserting that Plaintiff's Orange Book-listed patents are invalid, unenforceable, or will not be infringed by the proposed generic products.

Case Timeline

Date Event
2018-06-22 Earliest Priority Date for ’820, ’623, ’755, ’756, ’404 Patents
2018-07-23 Earliest Priority Date for ’987, ’382, ’758, ’740 Patents
2022-05-13 FDA grants approval for Mounjaro® (tirzepatide)
2022-06-14 U.S. Patent No. 11,357,820 issues
2023-11-08 FDA grants approval for Zepbound® (tirzepatide)
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, and 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
2026-06-26 Date of first Notice Letter from Macleods
2026-09-09 Complaint Filing Date

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

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

  • Patent Identification: U.S. Patent No. 11,357,820, "GIP/GLP1 Agonist Compositions," issued June 14, 2022 Compl. ¶26

The Invention Explained

  • Problem Addressed: The patent identifies a "desire for compositions of tirzepatide providing acceptable stability and acceptable patient injection site experience" '820 Patent, col. 2:9-14 It notes that some common pharmaceutical ingredients can cause painful stinging at the injection site '820 Patent, col. 3:10-24
  • The Patented Solution: The patent discloses a pharmaceutical composition for subcutaneous injection that combines the active ingredient, tirzepatide, with specific excipients—namely sodium chloride (NaCl) and dibasic sodium phosphate—to achieve a formulation that provides "commercially acceptable shelf-life stability, in-use stability, and is associated with acceptable patient injection site experience" '820 Patent, col. 2:1-4
  • Technical Importance: The invention provides a specific, stable, and patient-tolerated formulation necessary for the successful commercialization of tirzepatide, a GIP/GLP1 co-agonist peptide for treating diabetes and obesity '820 Patent, col. 1:12-19

Key Claims at a Glance

  • The complaint asserts infringement of at least Claim 1 '820 Patent, col. 9:36-42 Compl. ¶55
  • The essential elements of independent 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 ('Compl. ¶57).

U.S. Patent No. 11,918,623 - "GIP/GLP1 Agonist Compositions"

  • Patent Identification: U.S. Patent No. 11,918,623, "GIP/GLP1 Agonist Compositions," issued March 5, 2024 Compl. ¶28

The Invention Explained

  • Problem Addressed: The patent addresses the need for effective treatments for obesity, a "complex medical disorder resulting in excessive accumulation of adipose tissue mass" '623 Patent, col. 4:19-21 '623 Patent, col. 1:35-37 It also notes the general need for stable and well-tolerated tirzepatide compositions '623 Patent, col. 1:40-41
  • The Patented Solution: The patent claims a method of treating obesity by administering a specific pharmaceutical composition of tirzepatide. The claimed formulation includes tirzepatide, dibasic sodium phosphate, and NaCl within specified concentration ranges, and optionally includes phenol ('623 Patent, col. 10:40-56, Claim 1). This patent protects the specific use of a formulation for an indication.
  • Technical Importance: The patent provides intellectual property protection for the specific use of a tirzepatide formulation to treat obesity, a major public health concern '623 Patent, col. 1:35-37

Key Claims at a Glance

  • The complaint asserts infringement of at least Claim 1 '623 Patent, col. 10:40-56 Compl. ¶71
  • The essential elements of independent 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 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 Compl. ¶73

Multi-Patent Capsules

  • 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 using a specific four-step dose-escalation regimen for a GIP:GLP-1 peptide. The peptide must have a specific GIP:GLP-1 receptor agonist potency ratio, and the dosing schedule involves administering progressively larger doses (25%, 50%, 75% of the fourth dose) over set time intervals ('987 Patent, col. 18:8-25, Claim 1).
    • Asserted Claims: At least Claim 1 Compl. ¶89
    • Accused Features: The proposed labeling for Defendants' generic product is alleged to instruct and encourage this specific dosing regimen for treating type 2 diabetes Compl. ¶90

  • 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: This patent covers methods for treating type 2 diabetes and improving weight management by administering an "escalation dose" (2.5 mg, 7.5 mg, or 12.5 mg) for at least two weeks, followed by a "maintenance dose" (5.0 mg, 10.0 mg, or 15.0 mg) ('382 Patent, col. 23:16-24:10, Claims 1 and 11).
    • Asserted Claims: At least Claims 1 and 11 Compl. ¶¶108, 110
    • Accused Features: The proposed labeling for Defendants' products is alleged to instruct and encourage these specific escalation and maintenance dosing regimens Compl. ¶¶109, 111

  • U.S. Patent No. 12,453,755: "GIP/GLP1 Agonist Compositions," issued October 28, 2025 Compl. ¶34

    • Technology Synopsis: This patent claims a method of treating diabetes by administering a pharmaceutical composition containing tirzepatide, dibasic sodium phosphate, and NaCl within defined concentration ranges. It also optionally includes phenol '755 Patent, Claim 1 It is a method-of-use patent for a specific formulation.
    • Asserted Claims: At least Claim 1 Compl. ¶131
    • Accused Features: The proposed labeling for Defendants' generic Mounjaro product is alleged to instruct and encourage this method of treatment Compl. ¶132

  • U.S. Patent No. 12,453,756: "GIP/GLP1 Agonist Compositions," issued October 28, 2025 Compl. ¶36

    • Technology Synopsis: The patent claims a pharmaceutical composition comprising tirzepatide and a specific concentration range of NaCl, wherein the composition has a pH between 6.5 and 7.5 '756 Patent, Claim 1 This patent focuses on the combination of the active ingredient, a tonicity agent (NaCl), and a specific pH range.
    • Asserted Claims: At least Claim 1 Compl. ¶149
    • Accused Features: Defendants' proposed generic products are alleged to be pharmaceutical compositions that meet these claim elements Compl. ¶150

  • 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: This patent claims a method for improving weight management using a specific four-step dose-escalation regimen of a GIP:GLP-1 peptide with a defined potency ratio. The method is analogous to that in the '987 patent but is directed to weight management instead of diabetes '758 Patent, Claim 1
    • Asserted Claims: At least Claim 1 Compl. ¶166
    • Accused Features: The proposed labeling for Defendants' generic Zepbound product is alleged to instruct and encourage this specific dosing regimen for 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 Compl. ¶40

    • Technology Synopsis: The patent claims methods of treating type 2 diabetes and obesity by administering tirzepatide using a specific dose-escalation protocol: a 2.5 mg starting dose for four weeks, followed by 2.5 mg incremental increases to a maintenance dose of 5, 10, or 15 mg, with each increase administered for at least four weeks '740 Patent, Claims 1 and 6
    • Asserted Claims: At least Claims 1 and 6 Compl. ¶¶185, 187
    • Accused Features: The proposed labeling for Defendants' products is alleged to instruct and encourage this specific dose-escalation regimen Compl. ¶¶186, 188

  • 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 "free of preservative" and comprises tirzepatide, a specific concentration range of NaCl, and has a pH of 6.5 to 7.5 '404 Patent, Claim 1 This composition is designed for single-use applications.
    • Asserted Claims: At least Claim 1 Compl. ¶208
    • Accused Features: Defendants' proposed generic products are alleged to be pharmaceutical compositions that meet these claim elements Compl. ¶209

III. The Accused Instrumentality

  • Product Identification: Defendants' "Proposed ANDA Products" are generic versions of Mounjaro® (tirzepatide) and Zepbound® (tirzepatide) submitted to the FDA under ANDA Nos. 221768 and 221771 Compl. ¶1
  • Functionality and Market Context: The proposed products are sterile, injectable solutions containing tirzepatide as the active pharmaceutical ingredient Compl. ¶¶22-23 Compl. ¶49 They are intended for subcutaneous administration via autoinjectors and KwikPens in various strengths Compl. ¶1 The complaint alleges these products are bioequivalent to Lilly's Mounjaro® and Zepbound® products Compl. ¶50 The infringement action is based on the statutory act of filing the ANDAs with Paragraph IV certifications seeking to market these products before the expiration of Plaintiff's patents Compl. ¶1 Compl. ¶45 Compl. ¶61

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. 1:4-7
NaCl at a concentration from 6.2 mg/mL to 9.5 mg/mL; The Proposed ANDA Products are alleged to contain sodium chloride (NaCl) within the claimed concentration range. ¶56 col. 2:15-18
and dibasic sodium phosphate. The Proposed ANDA Products are alleged to contain dibasic sodium phosphate or an equivalent thereof. ¶56 col. 2:41-43

'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 for Proposed ANDA No. 221771 allegedly instructs and encourages treating obesity by administering the product. ¶72 col. 2:55-58
wherein the tirzepatide concentration is from about 5 mg/mL to about 30 mg/mL; The proposed product is alleged to have a tirzepatide concentration within this range. ¶72 col. 2:45-47
dibasic sodium phosphate is from about 0.67 to about 2.68 mg/mL; The proposed product is alleged to have a dibasic sodium phosphate concentration within this range, or an equivalent thereof. ¶72 col. 2:50-54
NaCl at a concentration from about 6.2 mg/mL to about 9.5 mg/mL; The proposed product is alleged to have a NaCl concentration within this range. ¶72 col. 1:26-28
and optionally comprising from about 3.0 mg/mL to about 7.0 mg/mL phenol. The proposed product is alleged to optionally comprise phenol within this range. ¶72 col. 2:61-64
  • Identified Points of Contention:
    • Scope Questions: The term "about," which precedes most numerical limitations in the asserted claims, will be a central focus of claim construction. The court will need to determine how much variance from the specified numbers is permissible. Furthermore, the complaint's use of "or equivalent thereof" with respect to certain excipients (e.g., dibasic sodium phosphate) suggests a potential dispute under the doctrine of equivalents if the Defendants' formulation uses a different but functionally similar compound (Compl. ¶56; Compl. ¶72).
    • Technical Questions: For the method-of-use patents ('623, '987, '382, '755, '758, '740), the key evidentiary question will be whether the specific language in the Defendants' proposed product labels actively encourages or instructs physicians and patients to perform the patented methods, thereby meeting the standard for inducement of infringement. The complaint alleges this will occur but does not provide the proposed label text (Compl. ¶¶72, 90, 109, 132, 167, 186).

V. Key Claim Terms for Construction

  • The Term: "about"

    • Context and Importance: This term qualifies nearly all numerical values in the asserted claims, including concentrations of active ingredients and excipients, as well as dosage amounts. Its construction is critical because in an ANDA case, even small differences between the claimed formulation and the generic formulation can be dispositive of literal infringement. Practitioners may focus on this term to determine the boundaries of the claimed ranges.
    • Intrinsic Evidence for a Broader Interpretation: The repeated use of "about" throughout the specifications suggests the inventors did not intend for the numerical values to be absolute and recognized that some variation is acceptable ('820 Patent, col. 2:15-16).
    • Evidence for a Narrower Interpretation: The specifications provide tables with precise exemplary formulations (e.g., NaCl at "8.2" mg/mL) that do not use the term "about," which could be used to argue that the inventors knew how to be precise when they intended to be '820 Patent, Table 1 A defendant may argue that in the context of a highly regulated field like pharmaceuticals, "about" should be construed narrowly to cover only standard manufacturing and measurement tolerances.

  • The Term: "dibasic sodium phosphate"

    • Context and Importance: This term identifies a key buffering agent in several asserted composition and method claims. The complaint alleges the accused products contain "dibasic sodium phosphate or equivalent thereof" (Compl. ¶56; Compl. ¶72). This phrasing anticipates a potential dispute over chemical identity versus functional equivalence.
    • Intrinsic Evidence for a Broader Interpretation: The patents teach that the purpose of the buffer is to maintain a specific pH range, typically 6.5 to 7.5 '820 Patent, col. 3:4-9 A plaintiff may argue that "dibasic sodium phosphate" should be construed to include other phosphate-based buffering systems that achieve the same function and result (the target pH) in the final composition.
    • Evidence for a Narrower Interpretation: The term "dibasic sodium phosphate" is a specific chemical compound (Na₂HPO₄). A defendant may argue that the claim language is precise and does not extend to other phosphate salts or buffer systems, which the patentee could have claimed but did not.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges induced infringement for all seven method patents ('623, '987, '382, '755, '758, '740, '404). The allegations are based on the assertion that Defendants' proposed product labeling will instruct and encourage healthcare providers and patients to administer the generic products in accordance with the patented methods (e.g., Compl. ¶¶80-82; Compl. ¶¶99-101; Compl. ¶¶120-124).
  • Willful Infringement: While not pleaded as a separate count, the complaint establishes a basis for willfulness by alleging pre-suit knowledge. Plaintiff alleges Defendants were aware of the asserted patents because they are listed in the FDA's Orange Book for Mounjaro® and Zepbound® and because Defendants themselves identified the patents in their Paragraph IV Notice Letters to Lilly Compl. ¶¶63, 79, 98, 119, 139, 158, 175, 196, 217

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

  • A core issue will be one of definitional scope: can the term "about," which qualifies nearly every numerical limitation, be construed to cover the precise concentrations and dosages in Defendants' ANDA products? The case may turn on whether any minor deviations fall within the literal scope of the claims or must be argued under the doctrine of equivalents.
  • A key evidentiary question will be one of label-driven inducement: for the seven method-of-use patents, does the specific language in Defendants' proposed product labels actively "instruct and encourage" the patented dosing regimens, or does it provide sufficient latitude for physicians to practice non-infringing methods?
  • A central technical dispute may be one of chemical versus functional equivalence: if Defendants' formulations use different but functionally similar excipients, such as an alternative phosphate buffer, the court will need to decide whether "dibasic sodium phosphate" is limited to its precise chemical identity or if it covers "equivalents thereof" as suggested by the complaint's language.