United States Patent 8,147,873: Scope, Claims, Patiromer Relevance and Patent Landscape
US Patent 8,147,873 protects pharmaceutical compositions containing a cation-exchange polymer made from crosslinked alpha-fluoroacrylic acid. The patent requires the polymer to be crosslinked with divinylbenzene and present in bead form. Its dependent claims limit the composition to oral or intestinal administration.
The claimed technology is associated with patiromer, the potassium-binding polymer marketed as Veltassa. The patent is composition-focused. It does not broadly claim every alpha-fluoroacrylic acid polymer, every potassium binder, or every patiromer manufacturing process.
What does US Patent 8,147,873 claim?
The patent has four claims supplied in the question. Claim 1 is the controlling independent claim.
| Claim |
Subject matter |
Legal effect |
| 1 |
Pharmaceutical composition containing an excipient and a cation-exchange, crosslinked alpha-fluoroacrylic acid polymer or salt; polymer crosslinked with divinylbenzene and in bead form |
Core composition claim |
| 2 |
Claim 1 composition suitable for oral or intestinal administration |
Administration-route limitation |
| 3 |
Claim 2 composition suitable for oral administration |
Oral-use limitation |
| 4 |
Claim 2 composition suitable for intestinal administration |
Intestinal-use limitation |
A product must satisfy every limitation of an asserted claim for literal infringement. A composition lacking the divinylbenzene crosslinker, lacking bead form, or using a polymer outside the alpha-fluoroacrylic acid scope would present a noninfringement position under the claim language.
What polymer technology is protected by the patent?
The patent covers a cation-exchange polymer based on alpha-fluoroacrylic acid, crosslinked with divinylbenzene and formed into beads.
Alpha-fluoroacrylic acid polymer
Alpha-fluoroacrylic acid polymers contain acidic carboxyl groups capable of exchanging ions. In a pharmaceutical application, the polymer can bind positively charged ions in the gastrointestinal tract. Patiromer uses this general mechanism to bind potassium.
The claim does not expressly require potassium binding. The claimed polymer could therefore cover compositions directed to cation exchange more generally, provided the claimed structural and formulation limitations are met.
Divinylbenzene crosslinking
Divinylbenzene creates a crosslinked, insoluble polymer network. Crosslinking affects:
- swelling in gastrointestinal fluids;
- ion-exchange capacity;
- mechanical stability;
- particle integrity;
- residence and transit through the intestinal tract; and
- the polymer’s ability to remain nonabsorbed.
The crosslinker is an express claim limitation. A competing product using a different crosslinking agent may avoid literal infringement, although the doctrine of equivalents could become relevant depending on prosecution history and claim construction.
Bead form
The bead limitation narrows the claim to particulate polymer structures. It distinguishes the claimed composition from a soluble polymer, a nonparticulate gel, a film, or an unstructured powder if the relevant court construes "bead form" as requiring a discrete spherical or substantially spherical particle.
Particle morphology can become important in litigation. Evidence may include microscopy, particle-size distribution, manufacturing records, formulation specifications, and technical declarations.
How broad is claim 1?
Claim 1 is narrower than a generic polymer composition claim but broader than a claim limited to patiromer, a specific counterion, a named dose, or a particular commercial formulation.
The claim requires the following elements:
- A pharmaceutical composition.
- A pharmaceutically acceptable excipient.
- A cation-exchange polymer.
- An alpha-fluoroacrylic acid polymer.
- Crosslinking with divinylbenzene.
- Bead form.
- The polymer or a salt thereof.
The claim does not expressly require:
- calcium as the counterion;
- sorbitol;
- a particular potassium-binding capacity;
- a specific bead diameter;
- a named disease;
- a particular dose;
- a specific dosage schedule;
- a particular container or sachet;
- a specific manufacturing process; or
- FDA-approved labeling.
This structure gives the claim meaningful reach across oral polymeric ion-exchange formulations, while leaving potential design-around routes based on polymer chemistry, crosslinking chemistry, particle morphology, or formulation architecture.
What does claim 2 add?
Claim 2 requires the composition to be suitable for oral or intestinal administration. It is dependent on claim 1 and therefore retains every limitation of claim 1.
The phrase "oral or intestinal administration" is functionally framed. It does not necessarily require a particular dosage form. A powder, suspension, sachet formulation, capsule, or other composition may qualify if it is suitable for the stated route and otherwise meets claim 1.
The intestinal limitation is commercially important because patiromer acts locally in the gastrointestinal tract and is not intended to be systemically absorbed.
What do claims 3 and 4 protect?
Claim 3 covers the claim 2 composition when suitable for oral administration. Claim 4 covers the composition when suitable for intestinal administration.
The claims provide overlapping fallback positions:
- Claim 1 captures the composition without an express route limitation.
- Claim 2 adds oral or intestinal suitability.
- Claim 3 focuses on oral administration.
- Claim 4 focuses on intestinal administration.
Claims 3 and 4 are not method-of-treatment claims. They do not expressly require administering the composition to a patient or treating hyperkalemia. They are composition claims with route-related limitations.
Is US 8,147,873 a patiromer patent?
Yes. The claimed polymer technology corresponds to the technology used in patiromer, the active polymer in Veltassa.
Veltassa is a nonabsorbed potassium binder approved by the FDA for the treatment of hyperkalemia in adults. The product is supplied as an oral powder that is mixed with water and administered orally. Its therapeutic activity results from potassium binding in the gastrointestinal tract. The FDA-approved product contains patiromer, supplied as a calcium-sorbitol complex. [1]
The patent claim language is not limited by the trade name Veltassa. A competing product can raise infringement risk if it uses the same claimed polymer architecture even under a different trade name or with a different pharmaceutical excipient.
What is the FDA and Orange Book status?
FDA status
The FDA approved Veltassa under NDA 205739 in October 2015. The product is an oral potassium-binding polymer for hyperkalemia. [1]
The approval is not a biologic approval. Patiromer is a nonbiologic polymeric drug product regulated through the drug framework rather than the biosimilar pathway.
Orange Book status
Patiromer-related patents have been listed in the FDA Orange Book for Veltassa. The relevant listed patents have included composition, formulation, and use-related protection associated with the product. Orange Book listing status can change through patent delisting, expiration, FDA updates, or changes to the reference product record. [2]
US 8,147,873 is important because its claims can reach the composition supplied in an approved oral patiromer product. Orange Book listing alone does not establish infringement or validity. It gives an approved-product patent a basis for a statutory stay if an ANDA applicant files an appropriate Paragraph IV certification and the NDA holder brings timely litigation.
When does US 8,147,873 lose exclusivity?
The patent issued on April 3, 2012. Its enforceable term is governed by the 20-year patent-term calculation from the earliest applicable nonprovisional filing date, adjusted for any patent-term adjustment and subject to terminal-disclaimer effects if applicable. [3]
The patent therefore does not expire merely 20 years after the issue date. The relevant calculation requires review of:
- the earliest effective nonprovisional filing date;
- priority claims;
- patent-term adjustment;
- terminal disclaimers;
- any patent-term extension;
- reexamination or reissue history; and
- current USPTO bibliographic records.
The statutory exclusivity date should be distinguished from FDA regulatory exclusivity. FDA exclusivity for Veltassa and patent exclusivity are separate rights. FDA approval exclusivity may end before, after, or independently of the patent term.
What other patents may protect patiromer?
Patiromer’s patent estate has historically included more than one category of protection.
Core polymer patents
These cover the alpha-fluoroacrylic acid polymer, crosslinking chemistry, ion-exchange functionality, or related compositions. US 8,147,873 falls principally in this category.
Formulation patents
Formulation claims may cover:
- calcium-sorbitol counterion systems;
- oral powder formulations;
- excipient combinations;
- stability characteristics;
- moisture control;
- particle-size properties;
- sachet presentations; and
- dose forms suitable for suspension in water.
A generic applicant may avoid one formulation patent while still encountering a separate composition patent.
Method-of-use patents
Patiromer method claims can cover treatment of hyperkalemia, reduction of serum potassium, or administration schedules. Such claims may be narrower than composition claims because they depend on the claimed disease, patient population, dose, or treatment method.
Manufacturing patents
Manufacturing claims may address:
- polymerization conditions;
- divinylbenzene crosslinking;
- bead formation;
- particle-size control;
- ion exchange and salt conversion;
- washing and purification;
- drying; and
- control of residual monomers or solvents.
A generic product can face manufacturing-process risk even when its final composition is designed to avoid a composition patent. Process patents generally require evidence concerning how the accused product is made.
How strong is the patent estate?
The strength of US 8,147,873 is moderate to strong against a product that uses the same polymer chemistry and bead architecture. The principal strength is the combination of structural limitations. The principal weakness is that the claim is narrow enough to permit technical design-around arguments.
| Issue |
Assessment |
| Polymer identity |
Strong if the accused product uses the claimed alpha-fluoroacrylic acid polymer |
| Crosslinker |
Strong limitation, but creates a design-around route |
| Bead morphology |
Fact-intensive and potentially contestable |
| Excipient limitation |
Broad because most drug products contain pharmaceutical excipients |
| Oral-use protection |
Relevant to Veltassa-type products |
| Potassium-specific scope |
Broader than potassium because claim 1 is not expressly limited to potassium |
| Manufacturing coverage |
Limited in the supplied claims because they do not recite a process |
| Validity exposure |
Depends on prior art addressing the specific polymer, divinylbenzene crosslinking, bead form, and pharmaceutical use |
Potential validity challenges would likely focus on anticipation, obviousness, written description, enablement, and claim construction. Prior art would need to be evaluated against the combined limitations, not against isolated disclosures of ion-exchange resins or acrylic polymers.
Which companies could challenge the patent?
Potential challengers would be generic drug manufacturers pursuing an ANDA for patiromer or a therapeutically equivalent product. The most relevant pathway would be an ANDA with a Paragraph IV certification asserting that the patent is invalid, unenforceable, or not infringed.
A Paragraph IV filing can trigger patent litigation under Hatch-Waxman. If the NDA holder files suit within the statutory period, FDA approval may be stayed for up to 30 months, subject to statutory exceptions and court developments. [4]
No biosimilar challenge is expected for patiromer because the product is not regulated as a biologic. The relevant competitive threat is generic or follow-on polymeric drug competition, not a biosimilar.
What generic entry risks exist?
Generic entry risk depends on three variables:
- Whether the ANDA product uses the same claimed polymer structure.
- Whether the relevant patent remains enforceable when the ANDA is filed.
- Whether the applicant can obtain approval after certification and litigation.
Scenario 1: Same polymer and same bead structure
This presents the highest infringement risk. A generic product using a divinylbenzene-crosslinked alpha-fluoroacrylic acid polymer in bead form would closely track claim 1.
Scenario 2: Same polymer but different crosslinker
This creates a stronger noninfringement position because divinylbenzene is expressly required. Other patents could still create risk.
Scenario 3: Same functional use but different polymer
A different cation-exchange polymer may avoid claim 1. The product could still encounter method-of-use, formulation, or manufacturing patents.
Scenario 4: Different particle morphology
A product not supplied in bead form may avoid literal infringement, but the technical meaning of "bead form" and any doctrine-of-equivalents argument would be central.
How does patiromer compare with other potassium binders?
| Product |
Active technology |
Regulatory category |
Main competitive distinction |
| Veltassa |
Patiromer, crosslinked polymer |
Small-molecule drug product |
Calcium-based potassium exchange; oral powder |
| Lokelma |
Sodium zirconium cyclosilicate |
Small-molecule drug product |
Inorganic crystalline ion trap |
| Kayexalate |
Sodium polystyrene sulfonate |
Older ion-exchange resin |
Established resin with different chemistry |
| Generic sodium polystyrene sulfonate |
Polystyrene sulfonate resin |
Generic drug |
Lower-cost alternative with different polymer structure |
Veltassa and Lokelma compete commercially but have materially different patent estates. Lokelma does not use the alpha-fluoroacrylic acid polymer claimed in US 8,147,873. Kayexalate and sodium polystyrene sulfonate products also use different resin chemistry.
What is the commercial exposure?
The commercial exposure is concentrated in the hyperkalemia market. Veltassa competes with Lokelma and legacy sodium polystyrene sulfonate products. Revenue exposure from US 8,147,873 depends on whether the patent is listed for the relevant product, whether it remains enforceable, and whether competing products fall within the claim.
The patent is more commercially significant for a patiromer generic than for a competing potassium binder based on unrelated chemistry. A rival product using zirconium silicate or polystyrene sulfonate would generally compete clinically without practicing the claimed alpha-fluoroacrylic acid polymer composition.
What geographic protection exists?
US 8,147,873 provides protection only in the United States. Related applications or national-phase patents may protect corresponding polymer compositions in Europe, Canada, Japan, and other jurisdictions, but foreign claim scope, expiration, opposition history, and enforceability must be analyzed separately.
The US patent does not create global exclusivity. Manufacturing outside the United States may still create US infringement exposure if the patented product is imported, offered for sale, or sold in the United States. US law also has specific rules governing importation and activities directed to regulatory submissions. [5]
Key Takeaways
- US 8,147,873 is a composition patent directed to a divinylbenzene-crosslinked alpha-fluoroacrylic acid cation-exchange polymer in bead form.
- The claims are consistent with the patiromer technology used in Veltassa.
- Claim 1 is the commercial core and does not expressly limit the composition to potassium binding, calcium, sorbitol, or hyperkalemia treatment.
- Claims 2 through 4 add oral and intestinal administration limitations.
- The main design-around routes are a different polymer, a different crosslinker, or a non-bead particle architecture.
- The patent is relevant to ANDA Paragraph IV risk but not to biosimilar litigation.
- Formulation, method-of-use, and manufacturing patents may create additional barriers even if a challenger avoids claim 1.
- The applicable patent expiration date must be calculated from the patent family’s effective nonprovisional filing date and adjusted for USPTO term credits and any terminal disclaimer.
- Veltassa competes with Lokelma and sodium polystyrene sulfonate products, but those products use different active technologies.
FAQs
Is US 8,147,873 limited to patiromer calcium?
No. The supplied claims do not expressly require calcium as the counterion. They cover the claimed polymer or a salt of that polymer, subject to the remaining limitations.
Does the patent cover all crosslinked acrylic acid ion-exchange resins?
No. It requires an alpha-fluoroacrylic acid polymer, divinylbenzene crosslinking, and bead form. Conventional polystyrene sulfonate resins and other acrylic acid polymers do not automatically fall within the claims.
Can a generic avoid the patent by selling a tablet instead of a powder?
Not necessarily. Dosage-form changes alone may not avoid claim 1 if the tablet contains the claimed polymer in bead form and includes a pharmaceutically acceptable excipient.
Does the intestinal-administration claim require a separate treatment step?
No. Claim 4, as supplied, is a composition claim. It requires suitability for intestinal administration but does not expressly recite administering the composition to a patient.
Is a foreign patiromer patent equivalent to US 8,147,873?
Not automatically. Foreign counterpart claims may differ because of prosecution amendments, national prior art, claim construction, validity rules, and local patent-term calculations.
References
- U.S. Food and Drug Administration. (2015). Veltassa (patiromer) prescribing information.
- U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book.
- United States Patent and Trademark Office. (n.d.). Patent term adjustment and patent term calculation guidance.
- Drug Price Competition and Patent Term Restoration Act, 21 U.S.C. §§ 355(j), 271(e).
- Patent Act, 35 U.S.C. §§ 271, 281-285.
