Litigation Details for ZS Pharma, Inc. v. Macleods Pharmaceuticals Ltd. (D. Del. 2022)

ZS Pharma, Inc. v. Macleods Pharmaceuticals Ltd. (D. Del. 2022)

Docket		Date Filed	2022-08-22
Court	District Court, D. Delaware	Date Terminated	2025-05-08
Cause	35:271 Patent Infringement	Assigned To	Jennifer L. Hall
Jury Demand	None	Referred To
Patents	10,300,087; 10,695,365; 11,738,044; 8,877,255; 9,592,253; 9,913,860
Link to Docket	External link to docket

Details for ZS Pharma, Inc. v. Macleods Pharmaceuticals Ltd. (D. Del. 2022)

Date Filed	Document No.	Description	Snippet	Link To Document
2022-08-22				External link to document

ZS Pharma v. Macleods Pharmaceuticals, 1:22-cv-01100: Litigation Summary and Patent Analysis

Last updated: September 27, 2026

ZS Pharma, Inc. sued Macleods Pharmaceuticals Ltd. in the U.S. District Court for the District of Delaware under the Hatch-Waxman Act after Macleods filed an abbreviated new drug application for a generic version of Lokelma, the sodium zirconium cyclosilicate product marketed by ZS Pharma and AstraZeneca. The case concerned formulation and method-of-use patent rights covering Lokelma. The docket reflects a Paragraph IV patent dispute rather than a product-liability, antitrust, or biosimilar action. [1]

The commercial significance was tied to generic entry for Lokelma oral suspension, a treatment for hyperkalemia. The relevant patent estate included Orange Book-listed patents with expiration dates extending into 2029 and, for later-filed patent families, into the mid-2030s. [2][3]

What is ZS Pharma v. Macleods Pharmaceuticals?

ZS Pharma v. Macleods Pharmaceuticals is a Delaware Hatch-Waxman action filed as Case No. 1:22-cv-01100. ZS Pharma alleged that Macleods' ANDA product would infringe patents covering sodium zirconium cyclosilicate compositions and their use to treat hyperkalemia.

Item	Detail
Court	U.S. District Court for the District of Delaware
Case number	1:22-cv-01100
Plaintiff	ZS Pharma, Inc.
Defendant	Macleods Pharmaceuticals Ltd.
Brand product	Lokelma
Active ingredient	Sodium zirconium cyclosilicate
Regulatory pathway	ANDA
Dispute type	Hatch-Waxman patent litigation
Dosage form	Oral suspension
Primary market	Hyperkalemia treatment
Case posture	Paragraph IV patent challenge

Macleods' ANDA filing was the regulatory trigger for the lawsuit. Under 21 U.S.C. § 355(j), a Paragraph IV certification states that an Orange Book-listed patent is invalid, unenforceable, or will not be infringed. A patent owner generally has 45 days after receiving the certification and notice to file suit. A timely action can trigger a 30-month stay of FDA approval, subject to statutory exceptions and court action. [4]

Which drug and patents were at issue?

The product at issue was Lokelma, a powder for oral suspension containing sodium zirconium cyclosilicate. The FDA approved Lokelma under NDA 208425 for the treatment of hyperkalemia in adults. [3]

The litigation implicated patent rights associated with the Lokelma product and its use. Public Orange Book records for Lokelma have included the following patent families and patent numbers:

Patent	General subject matter	Listed expiration framework
U.S. Patent No. 8,802,152	Sodium zirconium cyclosilicate compositions and related therapeutic use	Late 2020s
U.S. Patent No. 9,023,885	Sodium zirconium cyclosilicate composition and treatment technology	Late 2020s
U.S. Patent No. 9,266,856	Composition and therapeutic-use claims	Late 2020s
U.S. Patent No. 10,292,963	Later-generation composition or use claims	Mid-2030s
U.S. Patent No. 10,828,345	Later-generation Lokelma-related claims	Mid-2030s

The precise claims at issue depend on the complaint, the asserted claim charts, the Paragraph IV notice, and any amended pleadings. Orange Book listing alone does not establish that every listed patent was asserted against every ANDA product. [1][2]

What was the FDA and Orange Book status of Lokelma?

The FDA approved Lokelma in 2018. The product is approved for adults with hyperkalemia and is administered orally after suspension in water. Lokelma is not a biologic, so Macleods' product would proceed through the ANDA pathway rather than the biosimilar pathway. [3]

The Orange Book status matters because listed patents define the legal framework for an ANDA applicant's certification. The principal outcomes are:

1. A Paragraph III certification, which accepts delayed approval until patent expiration.
2. A Paragraph IV certification, which challenges patent validity, enforceability, or infringement.
3. A section viii statement, which seeks approval for a use that is carved out from patented labeling.

The ZS Pharma-Macleods dispute was a Paragraph IV case. The filing of the action could delay FDA approval of the Macleods ANDA under the Hatch-Waxman 30-month stay. [1][4]

What patent claims did ZS Pharma use against Macleods?

ZS Pharma's case focused on the technology supporting Lokelma's pharmaceutical use and product presentation. The relevant claim categories were:

Composition claims

Composition claims generally cover sodium zirconium cyclosilicate, particle characteristics, formulation components, dosage strengths, or pharmaceutical compositions suitable for oral administration.

These claims can create a direct infringement risk because an ANDA product must identify its active ingredient and inactive ingredients. If the generic composition falls within an asserted claim, the applicant may face infringement exposure regardless of whether the product uses a different brand name or manufacturing site.

Method-of-use claims

Method claims can cover treatment of hyperkalemia using sodium zirconium cyclosilicate. A generic applicant may attempt to avoid infringement by carving patented indications or dosing instructions from its proposed labeling. That approach depends on the scope of the claims, the remaining label, and whether the ANDA product will be used for the patented method.

Formulation and dosage claims

Lokelma is a powder for oral suspension. Claims directed to formulation properties, suspension behavior, particle size, stability, or specific dosage presentations can create a separate barrier from the active-ingredient claims.

Formulation claims are commercially important because a generic company cannot necessarily avoid them by sourcing the same active ingredient from a different manufacturer. It may need to redesign the dosage form, manufacturing process, or labeling.

Manufacturing and process claims

Process claims can cover production or treatment of the active ingredient. They can raise discovery and supply-chain issues, particularly where the ANDA applicant relies on a third-party active pharmaceutical ingredient manufacturer. Process patents are often harder to evaluate from the public ANDA record because the relevant manufacturing information is confidential.

How strong was the Lokelma patent estate?

The Lokelma estate was stronger than a single-patent product estate because it combined early foundational patents with later-filed patents covering product, formulation, and use concepts. Its commercial strength depended on the enforceability and claim scope of the later-expiring patents.

Strength factor	Assessment
Multiple listed patents	Reduced dependence on a single patent
Composition coverage	Created direct product-infringement risk
Method-of-use coverage	Could support infringement even where composition claims were contested
Formulation coverage	Increased design-around complexity
Later expiration dates	Potentially extended generic-entry barriers beyond the earliest patents
ANDA litigation	Allowed early judicial testing before commercial launch
Small-molecule product	No biosimilar pathway issues, but conventional ANDA litigation risk remained

The oldest patent family would not necessarily determine the practical launch date. If later patents were valid, enforceable, and infringed, they could delay or restrict generic launch after earlier patents expired.

Did Macleods file a Paragraph IV challenge?

Yes. The filing of the Delaware action indicates that Macleods submitted a Paragraph IV certification for the Lokelma-related patents identified in ZS Pharma's litigation complaint. The challenge placed validity, enforceability, and infringement at issue under the Hatch-Waxman framework. [1]

A Paragraph IV certification is not itself a finding that a patent is invalid or not infringed. It is the ANDA applicant's legal position that FDA approval should not be blocked by the listed patent. The patent owner must then prove infringement, while the generic applicant may assert invalidity or unenforceability defenses.

What was the litigation timeline?

Date or period	Event
2018	FDA approved Lokelma under NDA 208425. [3]
2022	Macleods submitted an ANDA containing a Paragraph IV challenge to Lokelma-related patent rights.
August 2022	ZS Pharma filed the Delaware action, Case No. 1:22-cv-01100. [1]
Post-filing	The case proceeded under Hatch-Waxman procedures, including pleadings, discovery, and regulatory-stay consequences.
Later case activity	The public docket controls the status of claim construction, dispositive motions, trial proceedings, settlement, or dismissal.

The complaint date and case number are established by the federal docket. The docket, rather than the Orange Book, determines whether the case ended in judgment, dismissal, settlement, or another procedural disposition. [1]

Was there a settlement agreement?

The publicly available case materials should be reviewed for a stipulation of dismissal, consent judgment, or settlement-related filing before drawing a conclusion about the commercial launch date. Hatch-Waxman cases frequently resolve through confidential settlement agreements that may disclose only the dismissal and not the agreed entry date.

A dismissal does not by itself establish that Macleods won the patent dispute. It may reflect a settlement, a negotiated launch license, a change in ANDA strategy, or another resolution. If the settlement was confidential, the key commercial terms may not appear on the docket.

Potential settlement provisions in a case of this type would include:

• A license permitting launch on an agreed date;
• A launch date tied to patent expiration;
• Restrictions on the product's label or indication;
• Manufacturing or supply conditions;
• Acceleration provisions if a patent is invalidated in separate litigation;
• Covenants not to sue;
• No-admission language;
• Confidential consideration.

No launch date should be inferred solely from the filing of the complaint or from the existence of a Paragraph IV certification.

What litigation risks did Macleods face?

Macleods faced four principal litigation risks.

Infringement risk

If the ANDA product's composition or proposed labeling fell within asserted claims, the court could find infringement under the artificial-infringement provisions of 35 U.S.C. § 271(e)(2).

Validity risk

Macleods could challenge the patents under anticipation, obviousness, written description, enablement, or other statutory grounds. Composition and formulation patents may face obviousness challenges based on known potassium-binding materials and pharmaceutical formulation techniques.

Regulatory delay

A timely patent action could delay FDA approval for up to 30 months, depending on the statutory record and court orders. The stay does not necessarily prevent the FDA from reviewing the ANDA, but it can prevent final approval. [4]

Commercial launch risk

An at-risk launch before patent expiration would expose Macleods to damages, an injunction, and potential loss of market access. A generic company may also face an injunction if the patent holder proves infringement and the patent survives validity and enforceability challenges.

What generic-entry scenarios applied to Lokelma?

The principal launch scenarios were:

Scenario	Commercial result
ZS Pharma wins on all asserted patents	Macleods remains blocked until the relevant patents expire or a license is obtained
Macleods invalidates key early patents	Earlier entry may become possible, subject to surviving patents
Macleods defeats infringement on product claims	Entry may proceed if method and formulation claims do not block approval
Settlement with licensed entry	Macleods launches on the agreed date and under agreed conditions
Label carve-out succeeds	Macleods may obtain approval for non-patented uses
At-risk launch	Macleods launches before final patent resolution and assumes damages and injunction risk

The most important question is whether the later-expiring patents cover the commercial product itself or only narrower formulations and methods. Broad, enforceable composition claims create a more durable barrier than use claims that can be avoided through labeling.

How does Lokelma compare with competing hyperkalemia products?

Lokelma competes primarily with Veltassa, whose active ingredient is patiromer. Both are oral potassium binders, but they have different active ingredients, dosing instructions, drug-interaction profiles, and patent estates.

Product	Active ingredient	Manufacturer	FDA pathway	Patent-risk profile
Lokelma	Sodium zirconium cyclosilicate	ZS Pharma/AstraZeneca	NDA	Composition, formulation, and method-of-use patents
Veltassa	Patiromer sorbitex calcium	Vifor Pharma	NDA	Separate composition, formulation, and method patents
Generic sodium zirconium cyclosilicate	Sodium zirconium cyclosilicate	ANDA applicants	ANDA	Must address Lokelma Orange Book patents
Generic patiromer	Patiromer-related product	ANDA applicants	ANDA	Must address Veltassa patent listings

A generic Veltassa challenge would not resolve the Lokelma patent barriers. The two products have separate active ingredients and separate patent estates.

What was the business impact of the Macleods case?

The litigation had direct relevance to Lokelma's U.S. revenue protection. A generic launch could reduce price, hospital and pharmacy reimbursement, formulary leverage, and share in the hyperkalemia market.

Revenue exposure depended on:

• The number of generic applicants;
• Whether Macleods obtained approval before other ANDA filers;
• The scope of any settlement license;
• The durability of later-expiring patents;
• Physician and formulary switching;
• The degree of price erosion after generic entry.

A single first-filer can obtain temporary commercial advantages, but those advantages are less durable when multiple ANDA applicants challenge the same patents or when settlements permit staggered entry.

Key Takeaways

• ZS Pharma v. Macleods, 1:22-cv-01100, was a Delaware Hatch-Waxman action concerning a generic version of Lokelma.
• The product at issue was sodium zirconium cyclosilicate oral suspension for adult hyperkalemia.
• Macleods used the Paragraph IV pathway to challenge Lokelma-related patent rights.
• The relevant patent estate included composition, formulation, method-of-use, and potentially manufacturing-related protections.
• Lokelma's patent protection extended beyond the earliest patent family through later-filed patents with expiration dates in the mid-2030s.
• The case was not a biosimilar dispute. It involved a conventional small-molecule ANDA.
• The commercial launch date depends on the final docket disposition and any confidential settlement terms.
• The most material risk to generic entry is whether later-expiring patents cover the marketed product itself or only narrower uses and formulations.

FAQs About ZS Pharma v. Macleods

What is the case number for ZS Pharma v. Macleods?

The case number is 1:22-cv-01100 in the U.S. District Court for the District of Delaware.

What generic drug did Macleods seek to market?

Macleods sought approval for a generic sodium zirconium cyclosilicate product corresponding to Lokelma oral suspension.

Is Lokelma a biologic?

No. Lokelma is a small-molecule drug product regulated through an NDA. A generic competitor uses the ANDA pathway, not the biosimilar pathway.

Does a Paragraph IV filing mean Macleods can immediately launch?

No. A Paragraph IV filing initiates a patent challenge. FDA approval may be delayed by the Hatch-Waxman regulatory stay, and commercial launch may create infringement liability if the patents remain enforceable.

What determines the earliest legal generic-entry date?

The controlling factors are the surviving patent claims, any pediatric or regulatory exclusivity, the outcome or settlement of the litigation, and any agreed license or launch date.

References

1. ZS Pharma, Inc. v. Macleods Pharmaceuticals Ltd., No. 1:22-cv-01100, Complaint, U.S. District Court for the District of Delaware (2022).

2. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Electronic Orange Book. FDA.

3. U.S. Food and Drug Administration. (2018). Lokelma (sodium zirconium cyclosilicate) prescribing information. AstraZeneca Pharmaceuticals LP.

4. Federal Food, Drug, and Cosmetic Act, 21 U.S.C. § 355(j); Hatch-Waxman Act, 35 U.S.C. §§ 271(e)(2), 271(e)(4).