DCT

1:23-cv-01190

ZS Pharma Inc v. Macleods Pharma Ltd

Log In

I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:23-cv-01190, D. Del., 10/20/2023
  • Venue Allegations: Venue is alleged to be proper for Macleods Inc. as a Delaware corporation and for Macleods Ltd. as an alien corporation subject to personal jurisdiction in the District of Delaware.
  • Core Dispute: Plaintiffs allege that Defendants’ submission of an Abbreviated New Drug Application (ANDA) to market a generic version of the hyperkalemia drug LOKELMA® constitutes an act of infringement of a patent directed to low-impurity zirconium silicate compositions.
  • Technical Context: The technology concerns pharmaceutical-grade compositions for treating hyperkalemia (abnormally high serum potassium), a potentially life-threatening electrolyte disorder, where drug purity is critical for safe, long-term administration.
  • Key Procedural History: This action arises under the Hatch-Waxman Act, triggered by Defendants' ANDA filing containing a Paragraph IV certification against the patent-in-suit. The complaint notes that the asserted patent issued after the initial ANDA was filed. The parties are also engaged in separate, prior litigation (D. Del. Case No. 22-1100) concerning the same ANDA but a different set of patents.

Case Timeline

Date Event
2015-10-14 '044 Patent Priority Date
2022-07-14 Defendants send Notice Letter regarding ANDA No. 217541
2022-08-22 Plaintiffs file prior litigation on different patents
2023-08-29 U.S. Patent No. 11,738,044 Issued
2023-10-20 Complaint Filing Date

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

U.S. Patent No. 11,738,044 - Extended Use Zirconium Silicate Compositions and Methods of Use Thereof

The Invention Explained

  • Problem Addressed: The patent's background explains that while zirconium silicate can be used to treat hyperkalemia, compositions intended for long-term ("extended") use require careful control of impurities ('044 Patent, col. 3:15-22). Specifically, the patent identifies that known industrial-scale manufacturing processes can result in zirconium silicate compositions with lead levels of 1.1 ppm or more, which may be unsuitable for chronic daily dosing ('044 Patent, col. 3:23-33).
  • The Patented Solution: The invention is a zirconium silicate composition formulated to have a lead content below a specific threshold (0.6 ppm), rendering it acceptable for extended use ('044 Patent, Abstract; col. 3:56-61). The detailed description discloses manufacturing methods, such as using colloidal silica as a reactant and employing specific reactor designs, to achieve this high level of purity at large production volumes ('044 Patent, col. 4:47-59; Fig. 2).
  • Technical Importance: Achieving exceptionally low levels of heavy metal impurities like lead is a critical technical hurdle in manufacturing pharmaceuticals intended for chronic administration, where patient safety depends on minimizing cumulative exposure to toxic substances ('044 Patent, col. 3:20-22).

Key Claims at a Glance

  • The complaint does not identify specific asserted claims, alleging infringement of "one or more claims" (Compl. ¶34). The first independent claim is Claim 1, a method of use claim.
  • Independent Claim 1 Elements:
    • A method of treatment of hyperkalemia
    • comprising administering over a period of more than 5 consecutive days
    • to a patient in need thereof
    • a cation exchange composition comprising a zirconium silicate of a specified general formula
    • wherein the composition exhibits a lead content below 0.6 ppm
  • The patent also includes dependent claims further refining the lead content, particle size, and other properties of the composition ('044 Patent, col. 8:60-65, col. 9:1-15).

III. The Accused Instrumentality

Product Identification

  • The "Proposed ANDA Product," which is a generic version of LOKELMA® (sodium zirconium cyclosilicate) for oral suspension in 5 g and 10 g packets (Compl. ¶1).

Functionality and Market Context

  • The Proposed ANDA Product is intended for the treatment of hyperkalemia (Compl. ¶21). The complaint alleges that the product is a non-absorbed zirconium silicate that captures potassium in the gastrointestinal tract, thereby lowering serum potassium levels (Compl. ¶21). It further alleges that the ANDA relies on the approved New Drug Application for LOKELMA® and contains data to demonstrate bioequivalence (Compl. ¶29).

IV. Analysis of Infringement Allegations

No probative visual evidence provided in complaint. The complaint does not contain a claim chart exhibit. The following summary is based on the narrative allegations.

'044 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
A method of treatment of hyperkalemia... The Proposed ANDA Product is intended to treat hyperkalemia, and the proposed label will instruct healthcare providers to prescribe it for this purpose. ¶30, ¶31 col. 8:36-37
comprising administering over a period of more than 5 consecutive days... The patent is for "extended use," and the complaint alleges Defendants will instruct use of the product in accordance with its proposed labeling, which corresponds to the approved use of the branded drug for chronic conditions. ¶31, ¶36 col. 8:37-38
...a cation exchange composition comprising a zirconium silicate... The active pharmaceutical ingredient in the Proposed ANDA Product is identified as sodium zirconium cyclosilicate. ¶27, ¶28 col. 8:39-41
wherein the composition exhibits a lead content below 0.6 ppm. The complaint does not provide specific factual allegations regarding the lead content of the Proposed ANDA Product, but makes a general allegation that the product infringes one or more claims of the patent. ¶34 col. 8:57-59
  • Identified Points of Contention:
    • Technical Question: The complaint offers no specific evidence that the Defendants' Proposed ANDA Product meets the critical "lead content below 0.6 ppm" limitation. A central factual dispute will likely be the actual measured lead content of the Defendants' product. The outcome of discovery and expert testing on this point may be determinative.
    • Scope Questions: The interpretation of "lead content" could become a point of contention. For example, a dispute may arise as to whether the specific testing methodology described in the patent's specification (Inductively Coupled Plasma-Mass Spectrometry, or ICP-MS) is a required element for determining infringement of this limitation ('044 Patent, col. 6:5-12).

V. Key Claim Terms for Construction

  • The Term: "lead content below 0.6 ppm"
  • Context and Importance: This term appears to be the primary basis for the patent's novelty, distinguishing the claimed invention from prior art compositions allegedly containing higher levels of lead impurity. Practitioners may focus on this term because infringement of Claim 1 hinges entirely on whether the accused product meets this specific numerical threshold.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: A party could argue that the term should be given its plain and ordinary meaning: any scientifically valid measurement showing a lead content of less than 0.6 parts per million meets the limitation, regardless of the specific test used.
    • Evidence for a Narrower Interpretation: The specification discloses specific, preferred ranges, such as "from 0.1 and 0.6 ppm" and "from 0.3 to 0.5 ppm" ('044 Patent, col. 3:57-59). Furthermore, dependent claim 13 explicitly recites that the lead content is "determined using inductively coupled plasma-mass spectrometry (ICP-MS)" ('044 Patent, col. 9:16-20). A party could argue this disclosure limits the scope of "lead content" in Claim 1 to values determined by the ICP-MS method, or that the term should be construed in light of the preferred embodiments.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges induced infringement, asserting that Defendants' proposed product label will instruct healthcare providers and patients to administer the product in an infringing manner (i.e., for the treatment of hyperkalemia over an extended period) (Compl. ¶¶ 31, 36-37). It also alleges contributory infringement, stating the product is not a staple article of commerce and is especially made for an infringing use (Compl. ¶38).
  • Willful Infringement: The complaint does not use the term "willful," but it does allege that Defendants have or will have knowledge of the patent and that their activities will result in infringement (Compl. ¶38). The prayer for relief requests a declaration that the case is "exceptional" under 35 U.S.C. § 285, which is the statutory basis for awarding attorney's fees and is often associated with findings of inequitable conduct or willful infringement (Compl. p. 9, ¶e).

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

  • A core issue will be one of evidentiary proof: Can Plaintiffs produce evidence, likely through discovery and testing, demonstrating that Defendants' proposed generic product actually possesses a "lead content below 0.6 ppm" as required by the asserted patent's claims? The complaint currently lacks specific factual allegations on this dispositive technical point.
  • A key legal question may be one of claim construction: How should the term "lead content" be defined? The case could turn on whether the court determines that this term requires measurement by the specific ICP-MS method disclosed in the patent specification, potentially creating a higher bar for proving infringement.