Details for Patent: 8,337,824

Which drugs does patent 8,337,824 protect, and when does it expire?

Patent 8,337,824 protects VELTASSA and is included in one NDA.

This patent has ninety-one patent family members in twenty-six countries.

Summary for Patent: 8,337,824

Title:	Linear polyol stabilized polyfluoroacrylate compositions
Abstract:	The present invention is directed to compositions of a linear polyol and a salt of a crosslinked cation exchange polymer comprising a fluoro group and an acid group. These compositions are useful to bind potassium in the gastrointestinal tract.
Inventor(s):	Detlef Albrecht, Michael Burdick, Han-Ting Chang, Dominique Charmot, Ramakrishnan Chidambaram, Eric Connor, Sherin Halfon, I-Zu Huang, Mingjun Liu, Jonathan Mills, Werner Strüver
Assignee:	Vifor International AG
Application Number:	US12/545,810
Patent Litigation and PTAB cases:	See patent lawsuits and PTAB cases for patent 8,337,824
Patent Claim Types: see list of patent claims	Use; Composition; Formulation;

US Patent 8,337,824: Patiromer Stabilization Claims, Scope, Expiration and Patent Landscape

US Patent 8,337,824 covers stabilized crosslinked cation-exchange polymer compositions used to remove potassium from the gastrointestinal tract. The commercial technology is consistent with calcium-based patiromer formulations marketed as Veltassa. The patent’s central limitation is not merely the potassium-binding polymer. It is the combination of a defined crosslinked polymer, a linear sugar alcohol loaded by slurrying, and, in several claims, controlled fluoride release during storage.

The strongest commercial embodiment is a calcium-form patiromer bead containing sorbitol, approximately 10% to 35% sorbitol by weight, and approximately 10% to 25% water or moisture. Claims 26 through 33, 61 through 68, and 71 through 76 concentrate the estate around that formulation.

What technology does US Patent 8,337,824 protect?

The patent protects four linked technical features:

1. A crosslinked cation-exchange polymer salt.
2. A specified polymer architecture based on Formula 1 alone with Formula 2, Formula 3, or both.
3. Loading of a linear sugar alcohol by slurrying the polymer salt in a sugar-alcohol solution.
4. Stabilization against fluoride release during storage.

The patent also claims once-daily potassium removal methods and particular calcium-sorbitol bead formulations.

The claims are composition-heavy. A party generally must satisfy the structural, compositional, processing, and, where applicable, performance limitations to fall within the literal scope.

Core claim architecture

Claim group	Principal subject matter	Key limitations
Claims 1-6	Stabilized polymer-salt composition	Sugar alcohol loaded by slurrying; 10-35 wt.%; Formula 1/2/3 polymer
Claims 7-12	Composition defined through polymerization	Polymer made from specified monomers; post-polymerization salt conversion; slurry loading
Claims 13-18	Salt, sugar alcohol, moisture and fluoride limitations	Calcium or sodium; sorbitol or xylitol; fluoride thresholds
Claims 19-23	Potassium-removal methods	Gastrointestinal potassium removal; once-daily dosing; binding-performance limitations
Claims 24-33	Narrow calcium-sorbitol embodiments	Calcium salt, sorbitol, moisture, and specific Formula 1A/2A/3A ratios
Claims 34-60	Parallel process and composition species	Calcium, sorbitol, moisture, bead form, and monomer limitations
Claims 61-76	Bead-form embodiments	Sugar alcohol-loaded beads, fluoride control, calcium-sorbitol species
Claims 77-78	Dosing frequency	Once-daily or twice-daily administration

How broad are the independent claims?

Claims 1, 2, 7, 8, 19, 20, 21, 22, 23, 61 and 69 are the principal independent claims.

Claim 1

Claim 1 requires:

• A pharmaceutical composition.
• A crosslinked cation-exchange polymer salt.
• A linear sugar alcohol.
• Sugar-alcohol loading by slurrying in solution.
• A stabilizing amount of approximately 10% to 35% by weight.
• A polymer containing Formula 1 with Formula 2, Formula 3, or both.
• Formula 1 at least approximately 80 wt.% of the relevant structural units, or a Formula 1 mole fraction of at least approximately 0.87.

The claim is broad as to the sugar alcohol. It expressly covers arabitol, erythritol, glycerol, maltitol, mannitol, ribitol, sorbitol, xylitol, threitol, galactitol, isomalt, iditol and lactitol through dependent claim 14. It is also broad as to the counterion, with calcium, sodium, or combinations covered by claim 13.

The claim is narrower than a generic claim to any stabilized potassium binder because it requires the slurry-loading operation and a high proportion of the Formula 1 structural unit.

Claim 2

Claim 2 adds a functional storage limitation. The sugar alcohol must reduce fluoride-ion release compared with an otherwise identical composition without sugar alcohol, and the composition must contain no more than 1,000 ppm inorganic fluoride after storage.

This limitation creates two potential enforcement issues:

• The accused product may need testing to establish the comparative storage result.
• The patent owner may need to prove that the product meets the inorganic-fluoride threshold under the relevant storage conditions.

The limitation also creates a design-around opportunity if a competing formulation achieves stability through a different excipient or processing method and does not use the claimed slurry-loaded sugar alcohol.

Claims 7 and 8

Claims 7 and 8 define the invention through the manufacturing route. The crosslinked polymer must be the reaction product of specified monomers, must be converted to the polymer salt, and must then be slurried in a sugar-alcohol solution.

These claims are important because they reach manufacturing practice rather than only the final composition. A process that uses dry blending, spray coating, melt processing, or another loading mechanism may avoid literal infringement if the slurry limitation is not satisfied.

Claims 19 through 23

These claims cover therapeutic use rather than the composition alone. They require administration to remove potassium from the gastrointestinal tract.

Claim 20 requires once-daily administration where the daily potassium-binding capacity is at least 75% of the capacity achieved by administering the same polymer salt three times daily. Claim 23 requires approximately 5% more potassium extraction than an unstabilized comparator.

The performance language may be difficult to enforce without controlled testing. The claims also raise divided-infringement considerations where a manufacturer supplies the product but does not control the dosing instructions or patient administration.

What polymer is covered by the patent?

The claims use Markush structural definitions. Formula 1 contains an ion-exchange functionality represented by A1, which may be carboxylic, phosphonic or phosphoric. X1 is arylene. Formula 2 and Formula 3 introduce additional crosslinking or polymer-forming structural elements through X2, which may be alkylene, an ether moiety or an amide moiety.

The polymer must contain:

• Formula 1 plus Formula 2;
• Formula 1 plus Formula 3; or
• Formula 1 plus both Formula 2 and Formula 3.

Formula 1 must constitute at least approximately 80 wt.% of the relevant structural units, or its mole fraction must be at least approximately 0.87.

Claims 29, 33, 40 and 44 impose tighter compositional constraints. They require Formula 1A to constitute at least approximately 85 wt.% in one alternative and specify a Formula 2A-to-Formula 3A ratio. The claimed ranges are:

• Weight ratio of Formula 2A to Formula 3A: approximately 4:1 to 1:4.
• Mole ratio of Formula 2A to Formula 3A: approximately 0.2:1 to 7:1.

Because the formulas and structural drawings are not reproduced in the supplied claim text, the exact chemical identity of each Formula A species cannot be independently mapped from the text alone. The legal scope, however, is clear at the claim-category level: the patent targets a predominantly Formula 1 crosslinked ion-exchange polymer with controlled incorporation of the other monomer classes.

What formulations are protected by US 8,337,824?

The narrowest and most commercially relevant formulation is:

• Calcium counterion.
• Patiromer-type crosslinked cation-exchange polymer.
• Sorbitol as the linear sugar alcohol.
• Sorbitol loaded by slurrying.
• Sorbitol concentration of approximately 10% to 35%.
• Water or moisture at approximately 10% to 25%.
• Bead form.
• Formula 1A content of at least approximately 85%, or Formula 1A mole fraction of at least approximately 0.87.
• Controlled Formula 2A-to-Formula 3A ratio.
• Reduced fluoride release during storage.

Claims 26 through 33 and 65 through 68 are particularly important for calcium-sorbitol products. Claims 61 through 76 extend comparable coverage to bead-form compositions.

Formulation coverage matrix

Feature	Covered by claims
Calcium salt	13, 24, 26, 31, 35, 37, 42, 46, 50, 54, 58, 63, 65, 71, 73
Sodium salt	13, 45, 53
Sorbitol	15, 25, 26, 36, 37, 42, 48-50, 57-58, 64-65, 72-73
Xylitol	15, 48, 56
10-35 wt.% sugar alcohol	1, 7, 61
10-25 wt.% moisture or water	16, 27, 30, 32-34, 38, 41, 43-44, 62, 67-68, 70, 75-76
Bead form	52, 60-61, 69
Fluoride threshold	2, 8, 17, 18, 69
Once-daily use	20, 21, 77
Twice-daily use	78

How does fluoride stabilization affect infringement risk?

Fluoride control is a central technical distinction. The claims require the sugar alcohol to reduce release of fluoride ion from the polymer during storage. Claims 17 and 18 provide specific testing conditions:

• Less than approximately 1,000 ppm inorganic fluoride after six weeks at approximately 40°C.
• Less than approximately 500 ppm inorganic fluoride after six weeks at approximately 25°C.

A competing product using the same polymer but no sugar alcohol may avoid claims requiring sugar-alcohol stabilization. A product using sorbitol but incorporating it through a non-slurry process may present a separate noninfringement position, although the ultimate result would depend on claim construction and process evidence.

The claims also create an invalidity pressure point. The relevant questions would include whether the fluoride-release limitation is adequately supported, whether the claimed storage results are enabled across the full Markush scope, and whether the slurry-loading process produces a patentably distinct and predictable stabilization effect over prior art.

When does US Patent 8,337,824 lose exclusivity?

US Patent 8,337,824 issued on December 25, 2012, from a Relypsa-related patent family directed to stabilized crosslinked cation-exchange polymer compositions. The underlying priority and filing history control the statutory term. For a pre-1995 or post-1995 US application, the ordinary term is generally 20 years from the applicable earliest nonprovisional filing date, subject to patent-term adjustment, patent-term extension, terminal disclaimers and other USPTO calculations (USPTO, n.d.-a).

The patent is generally associated with an expiration period in the late 2020s. A precise enforceability date requires the USPTO patent-term-adjustment calculation and any terminal-disclaimer record. Patent expiration should therefore be analyzed separately from FDA regulatory exclusivity.

The patent’s commercial importance may continue after the basic composition patent expires if related continuation patents, formulation patents, manufacturing patents or Orange Book-listed method-of-use patents remain enforceable.

What is the Orange Book status of the patent?

Veltassa is patiromer calcium, approved by FDA under NDA 205739 in 2015 for treatment of hyperkalemia (FDA, 2015). Patiromer is a nonabsorbed potassium-binding polymer administered orally.

The Orange Book, rather than the patent document alone, determines whether a patent is listed against the NDA and whether an ANDA applicant must address that listing through certification. Orange Book-listed patents may cover:

• The active pharmaceutical ingredient or polymer composition.
• The calcium-sorbitol formulation.
• Manufacturing or stabilization features.
• Methods of treating hyperkalemia.

A Paragraph IV certification alleging that a listed patent is invalid, unenforceable or not infringed can trigger patent litigation under the Hatch-Waxman Act. The filing of an ANDA with a Paragraph IV certification generally gives the NDA holder an opportunity to sue within the statutory period, potentially producing a 30-month stay of approval under applicable conditions (FDA, n.d.; 21 U.S.C. § 355(j)(2)(A)(vii)(IV)).

The supplied record does not establish the current Orange Book listing status of US 8,337,824, any delisting, or the existence of a specific Paragraph IV challenge against this patent. Those issues must be distinguished from the patent’s technical scope.

Which companies are associated with the commercial patent estate?

Relypsa developed patiromer and commercialized Veltassa in the United States. Vifor Pharma acquired Relypsa in 2016 for approximately $1.53 billion, bringing the patiromer product and related intellectual-property portfolio into the Vifor organization (Vifor Pharma, 2016). CSL completed its acquisition of Vifor Pharma in 2022, making CSL the parent company of the Vifor business (CSL, 2022).

The relevant commercial chain is therefore:

Period	Company relationship
Development and initial commercialization	Relypsa
2016 acquisition	Vifor Pharma acquired Relypsa
2022 corporate transaction	CSL acquired Vifor Pharma
Product	Veltassa, patiromer calcium

Patent ownership for a particular patent must be confirmed from USPTO assignment records because corporate acquisition, licensing, security interests and subsidiary ownership can produce different recorded owners and exclusive licensees.

What is the competitive patent landscape for potassium binders?

The principal pharmaceutical competitors are Veltassa and Lokelma. Veltassa contains patiromer, a crosslinked polymer that exchanges calcium for potassium. Lokelma contains sodium zirconium cyclosilicate, an inorganic crystalline potassium-trapping material. Kayexalate and generic sodium polystyrene sulfonate are older ion-exchange products.

Product	Active technology	Primary commercial sponsor	Patent-risk profile
Veltassa	Patiromer calcium polymer with sorbitol and water	CSL Vifor	Polymer, formulation, stabilization, manufacturing and method patents
Lokelma	Sodium zirconium cyclosilicate	AstraZeneca	Inorganic composition, formulation, manufacturing and use patents
Kayexalate/generic SPS	Sodium polystyrene sulfonate	Multiple manufacturers	Older composition with lower barrier to generic competition
Generic patiromer	Patiromer calcium	Potential ANDA applicants	Must address listed patents and regulatory requirements

There is no biosimilar pathway for patiromer because it is a nonbiologic small-molecule/polymer drug product. Competition would proceed through the ANDA pathway for an equivalent drug product, not through a biosimilar application.

What generic entry risks exist?

A generic applicant could pursue several strategies:

1. Use the same polymer but alter the sugar alcohol.
2. Use sorbitol but load it through a different process.
3. Use a different counterion, subject to pharmaceutical and regulatory requirements.
4. Modify the Formula 2A-to-Formula 3A ratio.
5. Eliminate or reduce the claimed moisture range.
6. Use a different polymer architecture outside the Formula 1 predominance thresholds.
7. Develop a non-polymeric potassium binder.

The most difficult design-around path would be a calcium-sorbitol patiromer product that reproduces the claimed polymer composition, slurry-loading process, moisture range and bead structure. The most credible freedom-to-operate routes would focus on non-sorbitol stabilization, a different loading process, a different polymer composition, or a product that does not meet the fluoride limitations.

How strong is the patent estate?

US 8,337,824 has meaningful claim breadth at the formulation level but is not a blanket patent on all patiromer products. Its strength comes from the combination of:

• Specific polymer composition.
• High Formula 1 content.
• Sugar-alcohol loading by slurry.
• Quantified sugar-alcohol concentration.
• Fluoride-release control.
• Calcium-sorbitol embodiments.
• Moisture and bead-form limitations.
• Once-daily treatment claims.

Its main vulnerabilities are claim-construction and proof issues surrounding:

• The omitted structural formulas.
• The meaning of “loaded.”
• The scope of “slurrying in a solution.”
• The comparative fluoride-release test.
• The calculation of structural-unit ratios from monomer feed.
• Enablement across broad sugar-alcohol and polymer Markush classes.
• Whether therapeutic-performance limitations are sufficiently reproducible.

Key Takeaways

• US 8,337,824 is directed to stabilized crosslinked cation-exchange polymer compositions associated with patiromer technology.
• The core invention combines a predominantly Formula 1 polymer, a linear sugar alcohol, and slurry loading.
• Sorbitol, calcium, water or moisture, bead form and controlled fluoride release define the commercially important embodiments.
• Claims 2, 8, 17, 18 and 69 are especially important for fluoride-stability analysis.
• Claims 19 through 23 and 77 through 78 cover gastrointestinal potassium removal and dosing frequency.
• The patent is generally relevant to the late-2020s exclusivity period, subject to the USPTO term-adjustment and terminal-disclaimer record.
• Generic applicants would face the greatest risk with a calcium-sorbitol patiromer product using the same polymer and slurry-loading process.
• Patiromer has no biosimilar pathway. Generic competition would use the ANDA and Paragraph IV framework.
• The patent is one component of a broader Veltassa estate that may include related formulation, manufacturing and method-of-use patents.
• Current Orange Book listing, ownership, litigation and settlement status must be determined from the FDA and USPTO records applicable to the relevant NDA and patent family.

Frequently Asked Questions

Is US 8,337,824 a patent on patiromer itself?

No. It claims particular stabilized crosslinked cation-exchange polymer compositions and related potassium-removal methods. A patiromer product falls within the patent only if it satisfies the applicable polymer, sugar-alcohol, slurry-loading and other claim limitations.

Does the patent require sorbitol?

No. The independent claims are broader. Dependent claims identify sorbitol, xylitol and other linear sugar alcohols. Sorbitol becomes central in the narrower commercial embodiments.

Does dry blending sorbitol with the polymer infringe?

Not necessarily. The claims repeatedly require loading by slurrying the polymer salt in a sugar-alcohol solution. A dry-blending process could provide a noninfringement position, although product-composition and equivalents issues would remain relevant.

Does US 8,337,824 cover Lokelma?

No. Lokelma is sodium zirconium cyclosilicate, a different active technology. The polymer and structural-unit limitations in US 8,337,824 do not read directly on that inorganic potassium binder.

Can a generic applicant avoid the patent by using sodium instead of calcium?

Potentially, but not automatically. Claims 13, 45 and 53 expressly include sodium or sodium-calcium combinations. The complete claim set and any related patents must be analyzed before relying on a counterion change as a design-around.

References

1. AstraZeneca. (n.d.). Lokelma (sodium zirconium cyclosilicate) prescribing information.
2. CSL Limited. (2022). CSL completes acquisition of Vifor Pharma.
3. Food and Drug Administration. (2015). FDA approves Veltassa to treat hyperkalemia.
4. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book.
5. U.S. Patent and Trademark Office. (2012). U.S. Patent No. 8,337,824, stabilized compositions of crosslinked cation exchange polymers.
6. U.S. Patent and Trademark Office. (n.d.-a). Patent term adjustment and patent term extension.
7. Vifor Pharma. (2016). Vifor Pharma completes acquisition of Relypsa.

Drugs Protected by US Patent 8,337,824

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Vifor Pharma	VELTASSA	patiromer sorbitex calcium	POWDER;ORAL	205739-004	Oct 2, 2023		RX	Yes	No	8,337,824			Y		TREATMENT OF HYPERKALEMIA
Vifor Pharma	VELTASSA	patiromer sorbitex calcium	POWDER;ORAL	205739-001	Oct 21, 2015		RX	Yes	No	8,337,824			Y		TREATMENT OF HYPERKALEMIA
Vifor Pharma	VELTASSA	patiromer sorbitex calcium	POWDER;ORAL	205739-002	Oct 21, 2015		RX	Yes	Yes	8,337,824			Y		TREATMENT OF HYPERKALEMIA

International Family Members for US Patent 8,337,824

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	2365988		PA2018004	Lithuania
European Patent Office	2365988		CA 2018 00006	Denmark
European Patent Office	2365988		122018000012	Germany