DCT

1:23-cv-01188

ZS Pharma, Inc. v. Ascent Pharma Inc.

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 1:23-cv-01188, D. Del., 10/20/2023
  • Venue Allegations: Plaintiffs allege venue is proper for Ascent because it has confirmed it will not contest venue in the District for this litigation. Venue is alleged to be proper for Hetero because it is a foreign corporation subject to personal jurisdiction in the District.
  • Core Dispute: Plaintiffs allege that Defendants' filing 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 covering specific low-impurity compositions and their long-term use.
  • Technical Context: The technology concerns zirconium silicate compositions, a type of potassium binder, specifically formulated with a very low lead content to make them safe for extended use in managing chronic hyperkalemia (elevated blood potassium).
  • Key Procedural History: This action arises under the Hatch-Waxman Act, where the filing of ANDA No. 217578 is the statutory act of infringement. The complaint notes that the asserted patent issued after the Defendants filed their ANDA, but cites Federal Circuit precedent (Vanda Pharms.) for the proposition that infringement liability can still attach. The complaint also references a prior, ongoing lawsuit (Civil Action No. 22-1099-GBW) between the same parties involving the same ANDA but asserting different patents.

Case Timeline

Date Event
2015-10-14 ’044 Patent Priority Date
2022-07-18 Date of ANDA Notice Letter for previously asserted patents
2022-08-22 Plaintiffs file initial lawsuit on other patents
2023-08-29 ’044 Patent Issue Date
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, issued August 29, 2023

The Invention Explained

  • Problem Addressed: The patent background describes hyperkalemia as a serious condition where elevated potassium levels can lead to fatal cardiac arrhythmias. It notes that existing treatments, such as Kayexalate®, are not suitable for chronic, long-term use due to side effects like intestinal obstruction and the need to induce diarrhea (’044 Patent, col. 2:22-37, 2:46-53). Further, the patent identifies a need for zirconium silicate compositions that are safe for long-term administration, which requires careful control of impurities, particularly lead (’044 Patent, col. 3:15-23).
  • The Patented Solution: The invention is a method of treating hyperkalemia by administering a zirconium silicate composition that has a lead content below a specific, low threshold (e.g., below 0.6 ppm) (’044 Patent, Abstract; col. 3:55-60). This low lead content is intended to make the composition safe for "extended use" (’044 Patent, col. 1:19-24). The specification also details manufacturing processes, such as using colloidal silica instead of sodium silicate as a reactant, to achieve this high purity at an industrial scale (’044 Patent, col. 7:1-9, Example 3).
  • Technical Importance: The development of an oral potassium-binding agent safe for chronic use addresses a need for managing patients with ongoing conditions that cause hyperkalemia, such as renal insufficiency or congestive heart failure, for whom acute-only treatments are inadequate (’044 Patent, col. 2:61-65).

Key Claims at a Glance

  • The complaint asserts "one or more claims" of the ’044 Patent without specifying them (Compl. ¶40). The patent contains one independent claim.
  • Independent Claim 1:
    • A method of treatment of hyperkalemia comprising administering a specific cation exchange composition (zirconium silicate) to a patient in need thereof.
    • The administration occurs "over a period of more than 5 consecutive days."
    • The composition "exhibits a lead content below 0.6 ppm."

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, as described in ANDA No. 217578 (Compl. ¶1, ¶10).

Functionality and Market Context

  • The Proposed ANDA Product is intended to be a generic equivalent of LOKELMA® (Compl. ¶35). LOKELMA® is described as a non-absorbed zirconium silicate that works in the gastrointestinal tract to "preferentially capture potassium in exchange for hydrogen and sodium, thereby lowering serum potassium levels" (Compl. ¶26).
  • The complaint alleges that sodium zirconium cyclosilicate is the active ingredient in the Proposed ANDA Product (Compl. ¶33). The complaint includes a screenshot from Defendant Hetero's website listing Defendant Ascent as its U.S. manufacturing facility, which Plaintiffs use to support the allegation that Defendants operate as a single, vertically integrated entity for the production of generic pharmaceuticals (Compl. ¶8, p. 3). The screenshot from Hetero's website lists "Ascent Pharmaceuticals Inc" in "Central Islip, New York - USA" as one of its "state-of-the-art facilities" (Compl. p. 3).

IV. Analysis of Infringement Allegations

The complaint does not contain a claim chart. The infringement allegations are made on "information and belief" and are not detailed with specific factual evidence.

’044 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
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 formula (I)... The complaint alleges that Defendants' proposed product label will instruct healthcare providers to prescribe the product for the treatment of hyperkalemia, which will result in the performance of the claimed method of administration. ¶37, ¶42, ¶43 col. 10:35-66
wherein the composition exhibits a lead content below 0.6 ppm. The complaint alleges that the Proposed ANDA Product contains sodium zirconium cyclosilicate "as patented by the '044 Patent" and that its use constitutes infringement, implying the composition meets the claimed lead content limitation. ¶34, ¶40 col. 3:55-60

Identified Points of Contention

  • Evidentiary Question: What factual evidence will support the allegation that Defendants' Proposed ANDA Product actually "exhibits a lead content below 0.6 ppm"? The complaint makes this allegation conclusorily, and proof of this fact will be a central issue for infringement.
  • Scope Question: Does the proposed product labeling for the generic drug, which forms the basis for the inducement claim, instruct administration "over a period of more than 5 consecutive days" as specifically required by the claim? Infringement will depend on the precise instructions for use.

V. Key Claim Terms for Construction

  • The Term: "lead content"
  • Context and Importance: This term is the central feature distinguishing the invention from prior art compositions, purportedly making it safe for long-term use. The method of measuring this "content" could be dispositive. Practitioners may focus on this term because the patent discloses a very specific measurement protocol, potentially limiting the claim's scope.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: The plain language of independent claim 1 does not specify a measurement method, which a party could argue allows for any standard, scientifically acceptable technique for measuring lead content in a pharmaceutical composition.
    • Evidence for a Narrower Interpretation: The patent specification describes a specific and detailed protocol for measuring lead content: "Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)" following a closed-vessel microwave digestion process (’044 Patent, col. 6:5-15). Furthermore, dependent claim 13 explicitly adds the limitation that the lead content "is determined using inductively coupled plasma-mass spectrometry (ICP-MS)" (’044 Patent, col. 10:17-20). A party could argue this demonstrates that the inventors defined "lead content" by this specific methodology for the entire patent.

VI. Other Allegations

  • Indirect Infringement: The complaint explicitly alleges both induced and contributory infringement. The inducement allegation is based on the claim that Defendants' proposed product labeling "will instruct healthcare providers to prescribe the Proposed ANDA Product in the manner set forth in the label" (Compl. ¶37, ¶42, ¶43). The contributory infringement allegation is based on the assertion that the product is not a staple article of commerce and is especially made or adapted for an infringing use (Compl. ¶44).
  • Willful Infringement: The complaint does not contain a specific count for "willful infringement." It does allege that Defendants "have or will have knowledge" of infringement upon receiving FDA approval and that the product is "especially made to infringe" (Compl. ¶44). These allegations primarily support the claims for indirect infringement but could be used to support a future willfulness argument based on post-suit conduct.

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

  • A central issue will be one of evidentiary proof: will discovery demonstrate that the Defendants' proposed generic product, as manufactured at commercial scale, actually possesses a "lead content below 0.6 ppm"? The case may turn on factual disputes over the chemical composition of the accused product.
  • A second core issue will be one of induced infringement: will the final FDA-approved product label for Defendants' generic drug include instructions that direct administration for a duration that meets the "more than 5 consecutive days" limitation of the method claim? The absence of such instructions could defeat the inducement claim.
  • A key legal question will be one of claim construction: is the term "lead content" in the independent claim implicitly limited by the specific ICP-MS measurement protocol detailed in the specification and recited in a dependent claim? The answer will define the precise standard against which the accused product must be measured.