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ZS Pharma & AstraZeneca v. Alkem Laboratories — Sodium Zirconium Cyclosilicate Patent Dispute | PatSnap
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Case ID1:22-cv-01096
FiledAug 2022
ClosedFeb 2024
Patent Litigation

ZS Pharma & AstraZeneca v. Alkem: ANDA Consent Judgment Protects Lokelma Patents

ZS Pharma and AstraZeneca brought a Hatch-Waxman infringement action in Delaware against Alkem Laboratories over six patents protecting sodium zirconium cyclosilicate oral suspension — the active ingredient in Lokelma. The case resolved after 536 days via a consent judgment and permanent injunction, blocking Alkem’s ANDA-based generic entry unless specifically authorised under a negotiated settlement agreement.

Resolution time
536days
536 days from filing to consent judgment — typical for ANDA settlements pre-trial
Patents asserted
5
US8,877,255; US9,592,253; US9,913,860; US10,300,087; US10,695,365 and 1 further patent asserted
Outcome
Consent Judgment
Consent judgment with injunction — Alkem enjoined from commercialising ANDA No. 217558 product
Cost ruling
No costs awarded
Parties agreed: no costs, disbursements or attorneys’ fees awarded to either side
Published by PatSnap Insights Team · Verified by PatSnap Eureka Data
Case overview

ANDA challenge to Lokelma resolved with consent judgment and injunction

On 22 August 2022, ZS Pharma, Inc. and AstraZeneca Pharmaceuticals LP filed a patent infringement action in the District of Delaware (Case No. 1:22-cv-01096) against Alkem Laboratories Ltd., an India-headquartered generic pharmaceutical manufacturer. The complaint arose under the Hatch-Waxman Act, triggered by Alkem’s submission of Abbreviated New Drug Application No. 217558 seeking approval to market sodium zirconium cyclosilicate oral suspension in 5 g and 10 g per packet strengths — the generic equivalent of AstraZeneca’s branded product Lokelma, a potassium binder indicated for hyperkalaemia.

The action concluded on 9 February 2024 through a stipulated consent judgment entered by the Delaware District Court. Under the consent judgment, Alkem and its affiliates are permanently enjoined from making, using, selling, offering to sell, importing or distributing the ANDA product in a manner that would infringe the six Licensed Patents — unless specifically authorised under the underlying Settlement Agreement. All claims, counterclaims and affirmative defences were dismissed with prejudice and without costs to any party, and the court retained jurisdiction to supervise compliance.

The 536-day duration is consistent with Hatch-Waxman ANDA cases that settle prior to any claim construction hearing or trial, suggesting the parties reached commercial terms without fully litigating validity or infringement. The consent judgment’s structure — dismissal with prejudice paired with a patent licence and entry date provision embedded in the private Settlement Agreement — is a standard Hatch-Waxman resolution pattern. The specific licensed entry date, royalty terms and authorised generic provisions, if any, remain undisclosed in the public record.

Case at a glance
Case no.1:22-cv-01096
CourtDelaware
JudgeJennifer L. Hall
FiledAugust 22, 2022
ClosedFebruary 9, 2024
Duration536 days
OutcomeConsent Judgment
Verdict causeInfringement Action
BasisConsent Judgment
Prior Art Intelligence
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Case data sourced from PACER / Delaware District Court via PatSnap Eureka Litigation Intelligence Explore similar cases ↗
Case timeline

Filing to settlement in 536 days

536 days from filing to consent judgment — typical for ANDA settlements pre-trial

Case timeline: Complaint filed May 13 2025, MAY–JUN — 536 days total Horizontal timeline showing the three key events in ZS Pharma, Inc. v Alkem Laboratories, Ltd. from filing to voluntary dismissal. Source: PACER, Delaware District Court. AUG 22 2022 Complaint filed MAY–JUN 2022 Pre-trial proceedings FEB 9 2024 Resolved consent judgment 536 DAYS TOTAL
Settlement terms

Consent judgment, permanent injunction and private settlement terms explained

Legal mechanism

What a consent judgment means in Hatch-Waxman litigation

A consent judgment is a court-ordered resolution agreed to by both parties. Unlike a pure voluntary dismissal, it carries the full force of a court order. Here, the court formally entered an injunction against Alkem — meaning any future breach of its terms could constitute contempt of court, not merely a contract dispute. This provides AstraZeneca stronger enforcement leverage than a private settlement agreement alone.

Court-enforceable resolution
Dismissal scope

Dismissed with prejudice — Alkem cannot re-litigate these claims

All claims and counterclaims — including any invalidity or non-infringement defences Alkem had asserted — were dismissed with prejudice. This means Alkem cannot revive those defences in future proceedings on the same patents for this ANDA product. The with-prejudice dismissal materially strengthens AstraZeneca’s position if Alkem or an affiliate were to file a new ANDA or attempt market entry outside the Settlement Agreement’s authorised terms.

With prejudice — no re-litigation
Injunction scope

Permanent injunction covers Alkem, affiliates, successors and assigns

The injunction extends beyond Alkem’s legal entity to cover any affiliate — defined broadly as any entity controlling or controlled by Alkem at a 50%+ ownership or governance threshold. This prevents Alkem from routing commercial launch through a subsidiary or partner entity. The carve-out phrase ‘unless otherwise specifically authorised pursuant to the Settlement Agreement’ signals that a licensed launch date is likely embedded in the private agreement.

Broad affiliate coverage
Patent portfolio

Six patents cover sodium zirconium cyclosilicate composition and formulation

The Licensed Patents — US8,877,255; US9,592,253; US9,913,860; US10,300,087; US10,695,365; and US11,738,044 — span multiple application filing dates and likely cover the crystalline composition, formulation and therapeutic use of sodium zirconium cyclosilicate. Asserting six patents across a layered portfolio is a characteristic AstraZeneca/ZS Pharma strategy to create overlapping protection, complicating any generic challenger’s invalidity or design-around efforts.

6-patent layered portfolio
Legal analysis based on PACER docket records for case 1:22-cv-01096 and PatSnap Eureka litigation intelligence Search PatSnap Eureka ↗
Parties and representation

Full party and counsel information

RoleNameTypeDetail
PlaintiffZS Pharma, Inc.CompanyAstraZeneca subsidiary and pharma group — holders of six sodium zirconium cyclosilicate patentsSearch in Eureka ↗
DefendantAlkem Laboratories, Ltd.CompanyAlkem Laboratories Ltd. — India-based generic pharmaceutical manufacturer, ANDA No. 217558 filerSearch in Eureka ↗
Plaintiff counselAlexandra M. JoyceAttorneyCounsel for ZS Pharma, Inc.Search in Eureka ↗
Plaintiff counselDaniel M. SilverAttorneyCounsel for ZS Pharma, Inc.Search in Eureka ↗
Plaintiff counselDaniel O’boyleAttorneyCounsel for ZS Pharma, Inc.Search in Eureka ↗
Plaintiff counselGyuhyun (joanne) BaeAttorneyCounsel for ZS Pharma, Inc.Search in Eureka ↗
Plaintiff counselHassen SayeedAttorneyCounsel for ZS Pharma, Inc.Search in Eureka ↗
Plaintiff counselJames Yi LiAttorneyCounsel for ZS Pharma, Inc.Search in Eureka ↗
Plaintiff counselMark A. HaydenAttorneyCounsel for ZS Pharma, Inc.Search in Eureka ↗
Defendant counselKevin M. CapuzziAttorneyCounsel for Alkem Laboratories, Ltd.Search in Eureka ↗
Defendant counselManish K. MehtaAttorneyCounsel for Alkem Laboratories, Ltd.Search in Eureka ↗
Defendant counselMichael S. WeinsteinAttorneyCounsel for Alkem Laboratories, Ltd.Search in Eureka ↗
Defendant counselZaiba BaigAttorneyCounsel for Alkem Laboratories, Ltd.Search in Eureka ↗
Presiding judgeJudge Jennifer L. HallChief JudgeDelaware District Court — Chief JudgeSearch in Eureka ↗
Official verdict

Stipulation of dismissal — official text

“ZS Pharma, Inc. and AstraZeneca Pharmaceuticals LP (hereinafter collectively “AstraZeneca”), and Alkem Laboratories Ltd. (hereinafter “Alkem”), the parties in the abovecaptioned actions, have agreed to terms and conditions representing a negotiated settlement of the actions and have set forth those terms and conditions in a Settlement Agreement (the “Settlement Agreement”). Now the parties, by their respective undersigned attorneys, hereby stipulate and consent to entry of judgment and an injunction in the actions, as follows: IT IS this ___ day of ____________, 2024: ORDERED, ADJUDGED AND DECREED as follows: 1. This District Court has jurisdiction over the subject matter of the above actions and has personal jurisdiction over AstraZeneca and over Alkem for the purpose of the above-captioned actions only. 2. As used in this Consent Judgment, (i) the term “Alkem Product” shall mean the drug product sold, offered for sale or distributed pursuant to Abbreviated New Drug Application No. 217558 (and defined in greater detail in the Settlement Agreement); (ii) the term “Licensed Patents” shall mean United States Patent Numbers 8,877,255; 9,592,253; 9,913,860; 10,300,087; 10,695,365; and 11,738,044; and (iii) the term “Affiliate” shall mean any entity or person that, directly or indirectly through one or more intermediaries, controls, is controlled by, or is under common control with Alkem; for purposes of this definition, “control” means (a) ownership, directly or through one or more intermediaries, of (1) more than fifty percent (50%) of the shares of stock entitled to vote for the election of directors, in the case of a corporation, or (2) more than fifty percent (50%) of the equity interests in the case of any other type of legal entity or status as a general partner in any partnership, or (b) any other arrangement whereby an entity or person has the right to elect a majority of the Board of Directors or equivalent governing body of a corporation or other entity or the right to direct the management and policies of a corporation or other entity. 3. Unless otherwise specifically authorized pursuant to the Settlement Agreement, Alkem, including any of its Affiliates, successors and assigns, is enjoined from infringing the Licensed Patents, on its own part or through any Affiliate, by making, having made, using, selling, offering to sell, importing or distributing of the Alkem Product. 4. Compliance with this Consent Judgment may be enforced by AstraZeneca and its successors in interest, or assigns, as permitted by the terms of the Settlement Agreement. 5. This District Court retains jurisdiction to enforce or supervise performance under this Consent Judgment and the Settlement Agreement. 6. All claims, counterclaims, affirmative defenses and demands in these actions are hereby dismissed with prejudice and without costs, disbursements or attorneys’ fees to any party.”
Source: PACER Docket, Case 1:22-cv-01096, Delaware District Court · Filed February 9, 2024

The consent judgment’s operative language permanently enjoins Alkem and its affiliates from any commercialisation of ANDA No. 217558 outside the private Settlement Agreement, while simultaneously dismissing all claims — including Alkem’s invalidity counterclaims — with prejudice. For AstraZeneca, this is a near-complete litigation win: it secures an injunction, extinguishes Alkem’s ability to re-litigate validity, and retains court jurisdiction for enforcement. For Alkem, the dismissal without costs provision and the Settlement Agreement’s undisclosed authorised-entry terms are the key concessions obtained in return.

PACER case 1:22-cv-01096 · Public docket record Explore in Eureka ↗
Patent at issue

US8,877,255 and 5 further patents — sodium zirconium cyclosilicate composition

Publication No.US9913860B2
Application No.US14/628017
Patent details
AssigneeZS Pharma, Inc.
ProductUS9,913,860 — sodium zirconium cyclosilicate, formulation patent
Publication typeB2 — grant (with prior publication)
Cited in actionAugust 22, 2022

Publication No.US9592253B1
Application No.US14/883428
Patent details
AssigneeZS Pharma, Inc.
ProductUS9,592,253 — sodium zirconium cyclosilicate, composition patent
Publication typeB2 — grant (with prior publication)
Cited in actionAugust 22, 2022

Publication No.US10300087B2
Application No.US15/421132
Patent details
AssigneeZS Pharma, Inc.
ProductUS10,300,087 — sodium zirconium cyclosilicate, formulation/method patent
Publication typeB2 — grant (with prior publication)
Cited in actionAugust 22, 2022

Publication No.US8877255B2
Application No.US14/060279
Patent details
AssigneeZS Pharma, Inc.
ProductUS8,877,255 — sodium zirconium cyclosilicate, foundational composition patent
Publication typeB2 — grant (with prior publication)
Cited in actionAugust 22, 2022

Publication No.US10695365B2
Application No.US15/878120
Patent details
AssigneeZS Pharma, Inc.
ProductUS10,695,365 — sodium zirconium cyclosilicate, therapeutic use patent
Publication typeB2 — grant (with prior publication)
Cited in actionAugust 22, 2022

The six Licensed Patents — US8,877,255; US9,592,253; US9,913,860; US10,300,087; US10,695,365; and US11,738,044 — protect sodium zirconium cyclosilicate (SZC), a selective cation exchanger that traps potassium ions in the gastrointestinal tract. The foundational US8,877,255, filed under application US14/060279, covers the crystalline microporous zirconium silicate composition that underpins Lokelma’s mechanism of action. Subsequent patents in the family, filed across multiple continuation applications between 2014 and 2018, extend protection to formulation parameters and therapeutic dosing regimens for hyperkalaemia management.

From a competitive standpoint, a six-patent portfolio spanning composition, formulation and therapeutic use claims makes SZC one of the more robustly protected small-molecule assets in the renal electrolyte management space. Pataromer (Veltassa, Vifor Pharma) represents the closest therapeutic competitor, but SZC’s distinct crystalline chemistry means design-around is structurally difficult. For pharma IP teams monitoring the potassium binder space, the staggered filing dates across the portfolio suggest meaningful patent term extension potential — and the inclusion of US11,738,044 (the most recently issued of the six) likely extends effective exclusivity into the 2030s.

Patent data sourced from USPTO via PatSnap Eureka patent database Search patent records in Eureka ↗
Freedom to operate

Should your team run an FTO against AstraZeneca’s SZC patent portfolio?

Any company developing a potassium-binding agent, oral cation exchanger, or zirconium silicate-based therapeutic — or preparing an ANDA against Lokelma — should treat these six patents as a mandatory FTO checkpoint. The consent judgment confirms that AstraZeneca actively enforces the full portfolio, not just the lead composition claim. Product teams working on hyperkalaemia therapies, whether novel or generic, should map their compound’s crystalline structure, formulation parameters and intended dosing against each of the six claim sets before advancing into IND-stage development.

PatSnap Eureka’s FTO Search Agent can pull and cluster the independent and dependent claims across all six Licensed Patents, map them against your compound’s structural and formulation characteristics, and flag high-risk claim overlaps automatically. Eureka’s claim monitoring alerts your team in real time if AstraZeneca or ZS Pharma files continuations or divisionals that could extend portfolio coverage — a critical risk in an active continuation family of this size. Start with a structured FTO search before your next regulatory filing milestone.

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Related litigation

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Strategic implications

What this case signals for the potassium binder IP landscape

Lokelma’s six-patent defence and consent judgment outcome carries practical implications for ANDA filers, competing innovators, and IP teams in the renal/cardiovascular space.

AstraZeneca’s multi-patent ANDA strategy appears to be working

By asserting six patents across multiple application families, AstraZeneca created a portfolio that is costly and time-consuming for any generic challenger to design around or invalidate in full. The consent judgment — reached without apparent IPR challenge or full claim construction — suggests Alkem calculated that litigation risk outweighed the cost of settling on AstraZeneca’s terms. ANDA filers in this space should model full portfolio clearance, not just lead-compound patents.

Private settlement terms control the real competitive outcome

The consent judgment is silent on Alkem’s authorised entry date, royalty obligations, and any authorised-generic provisions. In Hatch-Waxman cases of this structure, the competitive outcome — when Alkem can actually enter the market — is entirely governed by the undisclosed Settlement Agreement. Stakeholders tracking generic entry timelines for sodium zirconium cyclosilicate should not treat the 2024 case closure as signalling imminent generic competition.

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Frequently asked questions

ZS v Alkem — key questions answered

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Use PatSnap Eureka to map your compound or formulation against AstraZeneca’s six sodium zirconium cyclosilicate patents. Set claim monitoring alerts to catch continuation filings before they affect your development timeline.

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