US Patent 9,925,212: Scope, Claims, Expiration and Hyperkalemia Patent Landscape
US Patent 9,925,212 protects long-term treatment of hyperkalemia in chronic kidney disease patients with moderate-to-severe renal impairment. The independent claim is directed to patients with serum potassium of at least 5.5 mEq/L, eGFR of 15 to 44 mL/min/1.73 m², and daily treatment for more than eight weeks. The covered potassium binder is broad and can include patiromer, zirconium silicate products, zeolites and molecular sieves, subject to the claim limitations.
The patent is most commercially relevant to Veltassa, the patiromer product marketed by Vifor Pharma, and potentially to other chronic potassium-binding therapies. It is a method-of-treatment patent rather than a composition-of-matter patent. Its principal vulnerability is that the claimed renal outcomes may be challenged as inherent, obvious, insufficiently supported, or insufficiently tied to the administration of the potassium binder.
What does US Patent 9,925,212 cover?
The patent covers a treatment regimen with five central elements:
| Claim element |
Requirement |
| Disease |
Hyperkalemia in a chronic kidney disease patient |
| Baseline potassium |
Serum potassium of at least 5.5 mEq/L |
| Baseline renal function |
eGFR from 15 to 44 mL/min/1.73 m² |
| Treatment duration |
Daily administration for more than eight weeks |
| Active treatment |
An effective amount of a potassium-binding agent |
The patient may also be receiving a renin-angiotensin-aldosterone system, or RAAS, agent. RAAS therapy is optional, not mandatory. The claim therefore reaches patients receiving ACE inhibitors, angiotensin receptor blockers, mineralocorticoid receptor antagonists or related RAAS therapies, but it does not require concomitant RAAS treatment.
The polymer limitation is important. If the potassium-binding agent is a polymer, it must be a crosslinked cation-exchange polymer other than a polystyrene cation-exchange polymer. That exclusion removes traditional sodium polystyrene sulfonate and calcium polystyrene sulfonate products from the polymer branch of the claim.
How broad is independent claim 1?
Claim 1 is broad as to the identity of the potassium-binding agent but narrow as to patient selection and treatment duration.
The claim does not expressly require:
- A particular dose
- A particular formulation
- A particular counterion
- A specific reduction target for serum potassium
- A specific improvement in eGFR
- A specific RAAS drug
- Hospitalization or outpatient treatment
- A particular brand-name potassium binder
The claim does require the patient to satisfy the baseline potassium and eGFR ranges before treatment. A patient with eGFR below 15 or at least 45 mL/min/1.73 m² would fall outside the express scope of claim 1 unless another claim construction or doctrine expanded the relevant range.
The more-than-eight-week duration is also material. Acute or short-term administration does not meet claim 1. A two-day or one-week treatment could potentially implicate other patent claims in the family, but it would not satisfy the duration limitation in claim 1.
Which potassium binders may fall within US 9,925,212?
Patiromer
Patiromer is the strongest commercial fit. Veltassa contains patiromer sorbitex calcium, a nonabsorbed potassium-binding polymer. Patiromer is not a polystyrene cation-exchange resin and is generally described as a crosslinked polymeric potassium binder. A labeled or marketed use involving CKD patients with the claimed potassium and eGFR characteristics for chronic daily treatment would create a substantial claim-overlap risk.
The patent does not require the product to be called patiromer. Its language captures the treatment method if the administered product satisfies the polymer limitation and the patient and duration requirements.
Sodium zirconium cyclosilicate
Sodium zirconium cyclosilicate, marketed as Lokelma, is an inorganic crystalline potassium binder. It is not a crosslinked polymer. It may therefore be analyzed under the broader potassium-binding-agent language and the dependent claims directed to zirconium silicate, zeolite or molecular-sieve materials.
Whether a specific zirconium silicate product meets claims 19 through 25 depends on its technical identity and particle characteristics. A product can fall within the independent claim without meeting every particle-size limitation in claims 23 to 25.
Polystyrene sulfonate products
Sodium polystyrene sulfonate and calcium polystyrene sulfonate are excluded when the agent is treated as a polymer. The exclusion is express: the polymer must be a crosslinked cation-exchange polymer other than a polystyrene cation-exchange polymer.
The exclusion does not necessarily eliminate every theoretical nonpolymeric formulation containing polystyrene-related material, but conventional polystyrene sulfonate therapy is the clearest category outside the polymer limitation.
What do claims 2 through 18 add?
Claims 2 through 18 add renal and biochemical outcomes. The principal limitations are:
| Claims |
Added outcome or duration |
| 2 |
Increase or stabilization of eGFR |
| 3 |
Decrease in serum creatinine |
| 4 |
Longer time to progression to end-stage renal disease |
| 5 |
Increased survival |
| 6 |
eGFR benefit maintained for more than 12 weeks |
| 7 |
eGFR benefit maintained for more than 24 weeks |
| 8-11 |
eGFR benefit maintained for at least 52 weeks |
| 11 |
eGFR increase of at least 4 mL/min/1.73 m² |
| 12 |
Potassium reduction after at least two days, maintained for at least 52 weeks |
| 13-16 |
eGFR stabilization or increase after at least three months |
| 15 and 18 |
Stabilization of urine albumin-to-creatinine ratio |
| 17 |
Potassium reduction after at least two days |
Claims 4 and 5 are commercially significant because they link treatment to disease progression and survival. They are also legally more exposed than the basic treatment claim. Long-term renal and survival outcomes can raise questions about whether the patent specification demonstrates that the potassium binder itself causes the claimed result, particularly where the patient is also receiving RAAS therapy or other CKD treatments.
Claims 11 and 16 require an eGFR increase of at least 4 mL/min/1.73 m². Claims 8 through 10 and 13 distinguish between stabilization and measurable increase. These distinctions can affect infringement proof because the patentee would need clinical records showing the relevant baseline, follow-up period and outcome.
What formulations and physical properties are protected?
Claims 19 through 25 extend the patent beyond outcome-based treatment limitations.
| Claim |
Subject matter |
| 19 |
Zeolite potassium-binding agent |
| 20 |
Zirconium silicate |
| 21 |
Molecular sieve |
| 22 |
Zirconium germanate |
| 23 |
Substantially spherical particles |
| 24 |
Mean particle diameter below 250 micrometers |
| 25 |
Less than 4 volume percent of particles below 10 micrometers |
These claims can reach product-specific formulations if the product has the required material identity and particle distribution. Claims 23 to 25 are particularly relevant to manufacturing and formulation design because they create physical-property limitations that may be assessed through particle-size analysis, microscopy, laser diffraction or other validated testing.
A competitor could attempt to avoid these dependent claims by using a different particle morphology, a larger mean particle size, a different fine-particle distribution or a potassium binder outside the listed chemical classes. Such design-arounds would not necessarily avoid claim 1.
When does US Patent 9,925,212 expire?
The patent issued on March 27, 2018. Its priority chain is associated with Relypsa’s hyperkalemia and potassium-binder development program. The nominal patent-term analysis points to an expiration date in the 2033 period, subject to patent-term adjustment, terminal disclaimers and the precise continuity record. The Orange Book term for the associated Veltassa patent listing should control commercial launch analysis.
The patent is not a biologic patent and is not subject to the 12-year reference-product exclusivity framework under the Public Health Service Act. It is a small-molecule and polymer-drug patent issue governed primarily by the Hatch-Waxman framework.
Exclusivity timeline
| Event |
Timing |
| Patent grant |
March 27, 2018 |
| FDA approval of Veltassa |
2015 |
| FDA approval of Lokelma |
2018 |
| Patent protection |
Generally extends into the 2033 period, subject to official term calculation |
| Biosimilar exclusivity |
Not applicable |
| Generic or 505(b)(2) risk |
Relevant, depending on the product and ANDA/505(b)(2) strategy |
FDA approval of Veltassa did not itself establish that every patent claim in the family would remain enforceable through the full commercial life of the product. Patent-term adjustment, terminal disclaimers and Orange Book delisting or listing decisions must be reviewed patent by patent.[1][2]
What is the Orange Book status of US Patent 9,925,212?
The patent is associated with the Veltassa patent estate and is relevant to Orange Book-based generic certification analysis. Veltassa is approved under NDA 205739. An ANDA applicant seeking approval for a patiromer product must evaluate listed patents and may submit a Paragraph IV certification asserting that a listed patent is invalid, unenforceable or not infringed.[1]
The practical significance depends on:
- Whether the patent is currently listed against the relevant NDA.
- The use code assigned to the patent.
- Whether the proposed ANDA labeling would include the claimed CKD population and chronic treatment regimen.
- Whether the ANDA product is patiromer or a different potassium-binding active ingredient.
- Whether the applicant seeks approval before the patent’s listed expiration date.
A Paragraph IV certification can trigger Hatch-Waxman litigation if the patent holder files suit within 45 days of receiving notice. A 30-month stay may delay approval, subject to statutory exceptions and court orders.[3]
Which companies face the greatest patent risk?
Vifor and Veltassa
Vifor is the principal commercial stakeholder for patiromer. The patent is strategically important because it can reach the chronic-treatment population most relevant to Veltassa: CKD patients with persistent hyperkalemia who may require continued RAAS therapy.
AstraZeneca and Lokelma
AstraZeneca’s Lokelma is a competing chronic potassium binder. The zirconium silicate and molecular-sieve dependent claims create potential overlap at the method-of-use level, although Lokelma has its own composition, formulation and method-of-use patent estate.
The commercial risk is not identical to patiromer risk. Lokelma is an inorganic zirconium silicate product, so the polymer exclusion is less relevant. Claims 20 and 21 are more important for a Lokelma analysis than the polymer language in claim 1.
Generic patiromer developers
A generic patiromer applicant would face the most direct exposure. If the proposed labeling covers chronic use in CKD patients with the claimed potassium and eGFR levels, the applicant could receive a Paragraph IV challenge involving this patent and other Veltassa patents.
A generic applicant could attempt a label carve-out excluding the patented population or duration. That strategy would face practical and regulatory limits if the excluded use is central to the reference product’s approved labeling or if physicians would continue to use the generic for the patented method.
What patent litigation and settlement issues matter?
The key litigation questions are claim construction, written description, enablement, anticipation, obviousness and infringement by proposed labeling.
Claim construction issues
Likely disputes include:
- Meaning of “effective amount”
- Meaning of “daily”
- Scope of “more than 8 weeks”
- Whether eGFR must remain within the claimed range throughout treatment or only before treatment
- Meaning of “observing” an eGFR increase or stabilization
- Scope of “crosslinked cation exchange polymer”
- Whether zirconium silicate products are covered by claims 1, 20 or both
- Whether a patient’s concurrent RAAS treatment affects infringement
Validity issues
Potential defenses include:
- Prior clinical studies showing chronic potassium-binder treatment in comparable CKD patients
- Obviousness based on combining known potassium binders with known CKD populations
- Lack of written-description support for the full breadth of agents and outcomes
- Enablement across multiple chemical classes, including zeolites, zirconium silicates and zirconium germanates
- Inherent-result arguments concerning potassium reduction or renal stabilization
- Lack of reliable causation for survival and end-stage renal disease progression claims
Settlement agreements
A settlement could establish an agreed generic entry date, a licensed launch date, or a carve-out from particular methods of use. The patent itself does not establish any settlement terms. Any commercial entry date must be confirmed from the relevant ANDA litigation docket and settlement documents.
How strong is the patent estate?
US 9,925,212 is strongest against a product that meets all of the following conditions:
- It is used in CKD patients with eGFR of 15 to 44.
- Baseline serum potassium is at least 5.5 mEq/L.
- The product is administered daily for more than eight weeks.
- The product is a non-polystyrene crosslinked polymer or a listed inorganic binder.
- The proposed labeling or actual use supports chronic hyperkalemia treatment.
The estate is weaker where:
- The product is used only acutely.
- The target population has eGFR outside the claimed range.
- The applicant carves out the CKD population or chronic duration.
- The product is a conventional polystyrene sulfonate.
- Clinical data do not demonstrate the claimed renal outcomes.
- The product’s chemical and particle characteristics do not meet the dependent claims.
The patent is therefore a meaningful use-patent barrier but not a complete substitute for composition, formulation, manufacturing and polymorph patents. A generic or competing innovator would need a family-level freedom-to-operate review, not an analysis limited to US 9,925,212.
What generic launch scenarios exist?
| Scenario |
Commercial consequence |
| No Paragraph IV challenge |
Generic approval waits for patent or regulatory barriers to expire |
| Paragraph IV with litigation |
Approval may be delayed by litigation and a statutory stay |
| Successful invalidity or noninfringement challenge |
Earlier launch becomes possible |
| Label carve-out |
Approval may proceed for unpatented uses, subject to FDA and infringement limits |
| At-risk launch |
Generic launches before final resolution, exposing the applicant to damages and injunction risk |
| Licensed settlement |
Entry occurs on the negotiated date and terms |
Patiromer is the highest-risk target because the patent’s patient and duration limitations align with its chronic use. Lokelma faces a different analysis centered on zirconium silicate, molecular-sieve claims and AstraZeneca’s separate patent portfolio.
Key Takeaways
- US 9,925,212 is a method-of-treatment patent for chronic hyperkalemia management in CKD patients.
- Claim 1 requires serum potassium of at least 5.5 mEq/L, eGFR of 15 to 44 mL/min/1.73 m² and daily treatment for more than eight weeks.
- Patiromer is the clearest commercial product within the patent’s risk profile.
- Zirconium silicate, zeolite and molecular-sieve products may implicate dependent claims 19 through 22.
- Conventional polystyrene cation-exchange polymers are expressly excluded from the polymer limitation.
- Claims 2 through 18 add eGFR, serum creatinine, albuminuria, survival and disease-progression outcomes.
- Claims 23 through 25 create formulation and manufacturing risks based on particle morphology and size distribution.
- The patent is associated with the Veltassa Orange Book and Hatch-Waxman risk analysis.
- The patent’s nominal term extends into the 2033 period, subject to the official USPTO and Orange Book term records.
- A generic patiromer applicant would face the most direct Paragraph IV exposure.
FAQs
Does US 9,925,212 cover all potassium binders?
No. It covers the claimed treatment method when the patient, baseline laboratory values, treatment duration and agent limitations are satisfied. Conventional polystyrene cation-exchange polymers are excluded from the polymer limitation.
Does a patient need to receive a RAAS inhibitor to infringe?
No. RAAS treatment is optional under claim 1. A patient may fall within the claim without receiving an ACE inhibitor, ARB or mineralocorticoid receptor antagonist.
Does a short-term hospital treatment infringe US 9,925,212?
Generally, not claim 1, because claim 1 requires daily administration for more than eight weeks. Short-term treatment may implicate other patents or claims, but it does not satisfy the express duration limitation.
Can an ANDA applicant avoid the patent with a label carve-out?
Potentially, but only if the proposed labeling genuinely excludes the patented method and the remaining labeling does not induce or encourage infringement. FDA approval and patent noninfringement are separate questions.
Is this patent a biosimilar barrier?
No. Veltassa and Lokelma are not biologic reference products for purposes of the biosimilar pathway. The relevant competitive pathways are generally ANDA, 505(b)(2), or a new NDA, depending on the product and regulatory strategy.
References
- U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
- U.S. Food and Drug Administration. (2015). Veltassa (patiromer) prescribing information.
- U.S. Code, 21 U.S.C. § 355(j). Abbreviated new drug applications and patent certifications.
- U.S. Patent and Trademark Office. (2018). U.S. Patent No. 9,925,212, Methods of treating hyperkalemia.
- U.S. Food and Drug Administration. (2018). Lokelma (sodium zirconium cyclosilicate) prescribing information.
