US Patent 10,335,432: Claim Scope, Veltassa Patent Protection, Exclusivity and Generic Entry Risk
US Patent 10,335,432 protects a method of treating hyperkalemia with a narrowly defined particulate potassium binder. The claims combine dose, pore structure, particle size, potassium exchange capacity, and limits on sub-3-micron fines. The patent is directed to patiromer-type particles and is commercially relevant to Veltassa, patiromer sorbitex calcium.
The strongest infringement position is likely against a product that uses the claimed particle specification at a daily dose of 3 to 9 grams. The principal validity and litigation issues are expected to concern claim construction, measurement methods for particle-size and potassium-exchange limitations, obviousness over earlier patiromer formulations, and whether an ANDA applicant’s commercial product satisfies every limitation.
What does US Patent 10,335,432 protect?
The patent claims a therapeutic method rather than a composition standing alone. Claim 1 requires all of the following:
| Claim limitation |
Required scope |
| Disease |
Treatment of hyperkalemia |
| Patient |
A subject in need of treatment |
| Daily amount |
Between 3 and 9 grams per day |
| Particle structure |
Uniform microporous structure |
| Pore diameter |
About 3 angstroms |
| Median particle size |
Greater than 3 microns |
| Potassium binding |
KEC of at least 1.7 mEq/g |
| Fine-particle limit |
Less than 7% of administered particles under 3 microns |
The claim is cumulative. A competing product that satisfies the dose and therapeutic use but fails the pore-size, potassium-exchange, or particle-fines limitation would not literally infringe claim 1.
The patent therefore does not broadly cover every potassium binder or every patiromer product. It covers administration of particles meeting a defined physical and functional profile.
How do dependent claims 2 through 5 narrow the patent?
Claims 2 through 5 create narrower fallback positions.
| Claim |
Additional limitation |
| 2 |
Less than 3% of total particles under 3 microns |
| 3 |
Less than 2.5% of total particles under 3 microns |
| 4 |
Less than 2% of total particles under 3 microns |
| 5 |
Particles are partially protonated |
Claims 2 to 4 progressively tighten the fines specification. Each depends on claim 1, so the accused product must first satisfy the broader claim 1 limitations. Claim 4 is the narrowest particle-size claim and would generally be the most difficult to prove infringed, but it may provide stronger differentiation from prior art.
Claim 5 adds a chemical-state limitation. Partial protonation is relevant to the ion-exchange behavior of the binder and may distinguish calcium-form or partially protonated polymer particles from fully converted or differently exchanged materials.
What technical features define the claimed particles?
Uniform microporous structure
The phrase "uniform microporous structure" points to a particulate ion-exchange material with controlled internal porosity. The pores must be sufficiently uniform to support the claimed potassium-binding performance. The claim does not define uniformity by a numerical distribution or a specific analytical technique.
That omission creates a potential construction issue. A court could consider whether uniformity is a meaningful structural limitation, a result-oriented description, or a term understood by a person skilled in polymeric ion-exchange materials.
Pore diameter of about 3 angstroms
A 3-angstrom pore is comparable to the hydrated or partially hydrated dimensions relevant to ion transport and selectivity. The word "about" introduces tolerance around the nominal value. The patent does not state in the supplied claim language whether pore diameter is measured by gas adsorption, molecular probe analysis, crystallographic analysis, or another technique.
The measurement protocol can become material in litigation. A product may produce different pore-size results depending on the analytical method and sample preparation.
Median particle size greater than 3 microns
The median particle size requirement is separate from the requirement that fewer than a specified percentage of particles be below 3 microns. A product could have a median above 3 microns while still containing too many fine particles to satisfy claim 1.
The claim is therefore directed to both central particle size and distribution control.
Potassium exchange capacity of at least 1.7 mEq/g
The KEC limitation is functional but quantitatively defined. It requires the particles to bind potassium at a capacity of at least 1.7 milliequivalents per gram.
The patent claim does not specify the test conditions in the text supplied. Relevant variables may include pH, competing ions, ionic strength, equilibrium time, particle hydration, moisture content, and whether the result is normalized to dry or as-is weight. These factors can affect whether a batch meets the 1.7 mEq/g threshold.
What is the likely commercial product relationship?
Patiromer is a nonabsorbed potassium-binding polymer used to reduce serum potassium in patients with hyperkalemia. Veltassa is patiromer sorbitex calcium, marketed by Vifor Pharma and its affiliates. The FDA approved Veltassa under NDA 205739 in 2015.[1]
The claimed particle characteristics are consistent with a product strategy based on:
- controlled microporosity;
- high potassium-exchange capacity;
- reduced fine-particle content;
- oral administration in a defined daily-dose range; and
- a partially protonated ion-exchange state.
The particle-size limitations may have commercial significance beyond patentability. Reducing sub-3-micron particles can affect handling, powder dispersion, mouthfeel, dust generation, and tolerability. Those attributes can make the manufacturing process and particle-classification system important competitive assets.
What patents protect Veltassa and patiromer?
US Patent 10,335,432 should be analyzed as one patent in a broader patiromer portfolio. The Veltassa estate has included patents directed to patiromer compositions, formulations, particle properties, treatment methods, and manufacturing characteristics. Relevant patent families have included US Patent Nos. 8,877,294, 9,206,121, 9,364,573, 9,561,197, 9,925,252, and 10,335,432, among others.[2]
The commercial protection is layered:
| Protection category |
Typical subject matter |
| Core composition |
Patiromer polymer and ion-exchange forms |
| Formulation |
Sorbitol-containing oral powder and dosing presentation |
| Particle engineering |
Size distribution, porosity, and fines control |
| Method of use |
Treatment of hyperkalemia and potassium reduction |
| Manufacturing |
Polymer preparation, conversion, washing, drying, and classification |
| Regulatory listing |
Patents submitted for the approved drug under the Orange Book |
The precise scope of each patent depends on its issued claims, terminal disclaimers, patent-term adjustment, and Orange Book listing data. A patent number alone does not establish that every claim covers the marketed product.
What is the Orange Book status of US Patent 10,335,432?
US Patent 10,335,432 is associated with the Veltassa/patiromer patent estate and has been treated as a product-protection patent for the FDA-approved patiromer product. Orange Book-listed patents can require an ANDA applicant to make a Paragraph IV certification if the applicant seeks approval before the listed patent expires.[3]
For a listed method-of-use patent, an ANDA applicant may also use a section viii statement to carve out a patented indication if the remaining label omits the protected use. That strategy is less effective when the patent claims a broad treatment method corresponding to the principal approved use.
The legal effect of listing depends on:
- whether the patent is currently listed for NDA 205739;
- whether the listed claims cover the approved product or use;
- the expiration date recorded by FDA;
- the type of certification filed by an ANDA applicant; and
- whether the NDA holder brings suit within the 45-day period after receiving a Paragraph IV notice.
When does US Patent 10,335,432 lose exclusivity?
The patent’s effective expiration must be determined from the USPTO patent record, including the earliest effective nonprovisional filing date, patent-term adjustment, terminal disclaimers, and any patent-term extension. The claims supplied by the requester do not contain the data necessary to calculate a legally operative expiration date.
The patent should not be treated as having an automatic 20-year term measured from its issue date. US patent term generally runs 20 years from the earliest effective nonprovisional filing date, subject to statutory adjustments under 35 U.S.C. §§ 154 and 156.[4]
For commercial planning, the relevant date is the later of:
- the patent’s enforceable expiration date; or
- the date on which an ANDA applicant can lawfully launch after resolving listed-patent litigation and regulatory exclusivity.
FDA regulatory exclusivity and patent exclusivity are separate. Veltassa’s original five-year new chemical entity exclusivity has expired. Any remaining barrier is primarily patent-based rather than NCE-based.[1]
What Paragraph IV challenges and generic entry risks exist?
An ANDA applicant challenging this patent would likely focus on four positions.
Noninfringement
The applicant could design or characterize its product to fall outside one or more numerical limitations, such as:
- a daily dose outside the 3-to-9 gram range;
- a median particle size at or below 3 microns;
- KEC below 1.7 mEq/g under the relevant test;
- at least 7% of particles below 3 microns; or
- a non-partially protonated exchange form.
A dosing workaround may be difficult if the approved generic label necessarily directs administration within the claimed range.
Anticipation
An anticipation challenge would require one earlier reference to disclose every limitation in combination. The most difficult combination is likely the specific fine-particle threshold, KEC minimum, pore diameter, and daily dose.
Obviousness
An obviousness challenge could combine earlier patiromer disclosures with conventional particle-classification and ion-exchange optimization techniques. The patent owner would likely argue that the claimed combination produced a predictable clinical or manufacturing advantage, including reduced fines and adequate potassium-binding performance.
Indefiniteness and written description
Potential disputes could concern:
- the meaning of "uniform microporous structure";
- the tolerance represented by "about 3 angstroms";
- the measurement method for KEC;
- the basis for calculating particles under 3 microns; and
- the meaning of "partially protonated."
The claim’s numerical limitations are stronger when the specification supplies validated methods and reproducible test conditions.
How does Veltassa compare with Lokelma?
| Product |
Active material |
Sponsor |
Regulatory status |
Patent-risk profile |
| Veltassa |
Patiromer sorbitex calcium |
Vifor/Fresenius affiliates |
FDA-approved |
Particle, composition, formulation, and method patents |
| Lokelma |
Sodium zirconium cyclosilicate |
AstraZeneca |
FDA-approved |
Distinct inorganic crystal composition and use patents |
| Sodium polystyrene sulfonate |
Sodium polystyrene sulfonate |
Multiple manufacturers |
Older approved products |
Mature generic market with less comparable particle-specific protection |
US Patent 10,335,432 does not directly block Lokelma because Lokelma uses a different active material. It is more relevant to generic patiromer development and to any product using the same or a substantially equivalent particle-engineering platform.
What manufacturing and geographic barriers matter?
The patent claims create potential process barriers even though claim 1 is written as a treatment method. A manufacturer must reliably produce particles with:
- controlled pore diameter;
- a median size above 3 microns;
- low sub-3-micron content;
- KEC of at least 1.7 mEq/g; and
- the required protonation state.
Particle classification, milling, sieving, drying, washing, and ion conversion can affect each parameter. A generic developer may need to alter process conditions to avoid infringement, then demonstrate bioequivalence and product quality under FDA requirements.
The patent is limited to the United States. Separate patents and applications may create different freedom-to-operate positions in Europe, Canada, Japan, and other markets. US claim scope does not establish protection outside the United States.
How strong is the patent estate?
The patent has moderate-to-strong commercial value if the marketed product satisfies the claimed particle specifications and if the patent remains enforceable through the relevant generic-entry date. Its strengths are:
- multiple objective numerical limitations;
- a direct connection to the approved hyperkalemia indication;
- dependent claims with progressively narrower particle-fines thresholds; and
- technical limitations that may be difficult to design around without affecting product performance.
Its weaknesses are:
- dependence on analytical methods not specified in the supplied claims;
- potentially contestable terms such as "uniform" and "about";
- possible obviousness arguments based on routine particle engineering; and
- method-claim vulnerability if a generic label avoids the claimed administration instructions.
Key Takeaways
- US Patent 10,335,432 claims a hyperkalemia-treatment method using tightly specified patiromer-type particles.
- Claim 1 requires a 3-to-9 gram daily dose, approximately 3-angstrom pores, median particle size above 3 microns, KEC of at least 1.7 mEq/g, and fewer than 7% of particles below 3 microns.
- Claims 2 to 4 narrow the fine-particle threshold to below 3%, 2.5%, and 2%, respectively.
- Claim 5 adds partial protonation.
- The patent is commercially relevant to the Veltassa/patiromer patent estate.
- The main generic risks are literal infringement, Paragraph IV litigation, and difficulty reproducing the claimed particle profile while maintaining bioequivalence and product quality.
- The legally operative expiration date requires USPTO term data, including patent-term adjustment and any terminal disclaimer.
- The patent does not directly cover Lokelma because sodium zirconium cyclosilicate is chemically distinct from patiromer.
FAQs
Is US Patent 10,335,432 a composition patent?
No. The supplied claims are method claims. They protect administering qualifying particles to treat hyperkalemia rather than claiming the particles in isolation.
Can a generic avoid the patent by using a different dose?
Potentially, but only if the approved generic label and actual use fall outside the claimed 3-to-9 gram daily range. Dose changes may create separate regulatory and clinical problems.
Does the patent cover all patiromer products?
No. Coverage depends on whether the product satisfies every limitation, including pore diameter, KEC, median particle size, fine-particle percentage, and, for claim 5, partial protonation.
Is a biosimilar pathway relevant to patiromer?
No. Patiromer is a nonbiologic polymeric drug product. A competing product would generally proceed through an abbreviated new drug application or another small-molecule regulatory pathway, not the biosimilar pathway under the Public Health Service Act.
Which patent issue is most important in a Paragraph IV case?
The central issue is likely whether the ANDA product meets the claimed particle specifications under validated testing methods. The parties would also contest obviousness and the construction of "uniform microporous structure," "about 3 angstroms," and "partially protonated."
References
- U.S. Food and Drug Administration. (2015). Veltassa (patiromer sorbitex calcium) prescribing information.
- U.S. Patent and Trademark Office. (2019). U.S. Patent No. 10,335,432, Patiromer compositions and methods of use thereof.
- U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, 44th ed.
- 35 U.S.C. §§ 154, 156 (2024).
