Details for Patent: 8,778,324

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Summary for Patent: 8,778,324

Title:	Ion binding polymers and uses thereof
Abstract:	The present invention provides methods and compositions for the treatment of ion imbalances. In particular, the invention provides compositions comprising potassium binding polymers and pharmaceutical compositions thereof. Methods of use of the polymeric and pharmaceutical compositions for therapeutic and/or prophylactic benefits are disclosed herein. Examples of these methods include the treatment of hyperkalemia, such as hyperkalemia caused by renal failure and/or the use of hyperkalemia causing drugs.
Inventor(s):	Dominique Charmot, Han-Ting Chang, Mingjun Liu, Gerrit Klaerner
Assignee:	Vifor International AG
Application Number:	US13/647,690
Patent Litigation and PTAB cases:	See patent lawsuits and PTAB cases for patent 8,778,324
Patent Claim Types: see list of patent claims	Use; Composition; Dosage form;

US Patent 8,778,324: Scope, Claims, Expiration, and Patiromer Patent Landscape

US Patent 8,778,324 protects methods of treating hyperkalemia with certain low-swelling, crosslinked potassium-binding polymers. Its most commercially relevant claims cover crosslinked alpha-fluoroacrylic acid polymers containing calcium counterions, including polymeric structures associated with patiromer, the active ingredient in Veltassa. The patent issued on July 15, 2014, and has a nominal expiration date of November 20, 2029, subject to any applicable patent-term adjustment or disclaimer. [1]

The patent is a method-of-use patent rather than a broad composition patent. Its commercial value depends on whether an accused product uses the claimed polymer architecture, calcium form, swelling characteristics, and hyperkalemia treatment method.

What does US Patent 8,778,324 protect?

The patent has three principal claim groups:

Claim group	Core subject matter	Commercial relevance
Claims 1-12	Treatment of hyperkalemia with crosslinked cation-exchange polymers containing acid groups and an electron-withdrawing substituent	Broad functional genus
Claims 13-16	Treatment with a crosslinked alpha-fluoroacrylic acid polymer	Narrower polymer-class claims
Claims 17-20	Treatment with a crosslinked alpha-fluoroacrylic acid polymer containing calcium counterions	Most product-specific claim group

Independent claims 1, 13, and 17 each require administering a potassium-binding polymer to treat hyperkalemia. The claims do not cover every potassium binder. They require a particular polymer chemistry and, in certain claims, particular physical or ionic characteristics.

The patent focuses on polymers that exchange potassium in the gastrointestinal tract while limiting polymer swelling. The claimed chemistry is designed to improve potassium binding and intestinal handling compared with conventional ion-exchange resins.

What are the independent claims in US 8,778,324?

Claim 1: Broad polymer genus

Claim 1 requires:

1. A method of treating hyperkalemia.
2. Administration to an animal subject in need.
3. A potassium-binding polymer.
4. A crosslinked cation-exchange polymer.
5. Acid groups in acid or salt form.
6. An electron-withdrawing substituent attached to a carbon atom alpha or beta to the acid group.

The claim is broader than the alpha-fluoroacrylic acid claims. It can potentially encompass polymers containing carboxylic or phosphonic acid groups and different electron-withdrawing substituents, provided the polymer is crosslinked and used to treat hyperkalemia.

The claim does not require a human patient, a specific dose, a calcium counterion, a bead, or a particular dosage form. Those limitations appear in dependent claims.

Claim 13: Alpha-fluoroacrylic acid polymer

Claim 13 narrows the polymer to a crosslinked alpha-fluoroacrylic acid polymer. This is a chemically defined species or class rather than the broader functional definition in claim 1.

A product that uses a crosslinked alpha-fluoroacrylic acid polymer for hyperkalemia treatment faces a direct infringement risk under claim 13, assuming the accused polymer falls within the claim's construction.

Claim 17: Calcium-form alpha-fluoroacrylic acid polymer

Claim 17 requires:

• treatment of hyperkalemia;
• a crosslinked alpha-fluoroacrylic acid polymer; and
• a calcium cationic counterion.

This is the most commercially significant claim in the patent because patiromer is marketed as patiromer sorbitex calcium. FDA labeling describes Veltassa as a nonabsorbed potassium-binding polymer containing calcium as the counterion. [2]

Claim 17 does not expressly require a swelling ratio below 3 or a bead form. Those limitations appear in claims 18 and 20.

How do the dependent claims narrow patent 8,778,324?

Claims	Limitation
2	Electron-withdrawing group is hydroxyl, ether, ester, or halide
3	Acid group is carboxylic
4	Acid group is phosphonic
5	Fluoride is attached alpha to the carboxylic acid group
6	Swelling ratio is below 5
7	Swelling ratio is below 3
8	Subject is human
9	Administration is in a chewable tablet
10	Dose is approximately 0.5 to 30 grams per day
11	More than 75% acid-group ionization at physiological colonic pH
12	Calcium cationic counterion
14	Specified crosslinkers for alpha-fluoroacrylic acid polymer
15	Divinylbenzene crosslinker
16	Calcium cationic counterion
18	Swelling ratio below 3
19	Specified crosslinkers
20	Bead form

The dependent claims matter because an accused product may avoid a narrow claim while remaining within a broader one. For example, a product could use a calcium counterion but not be supplied as beads, avoiding claim 20 but potentially infringing claim 17.

What polymer chemistry does the patent cover?

The patent claims a crosslinked cation-exchange polymer with acid groups and an electron-withdrawing substituent near the acid functionality.

The relevant structural elements are:

• an acid-bearing polymer backbone;
• crosslinking that limits dissolution and swelling;
• an electron-withdrawing substituent attached alpha or beta to the acid group;
• potassium exchange in the gastrointestinal tract;
• optional calcium counterions;
• optional alpha-fluoroacrylic acid monomer units.

The most specific chemistry is the alpha-fluoroacrylic acid polymer. In that structure, fluorine is attached to the carbon alpha to the carboxylic acid group. Claim 5 separately captures a crosslinked carboxylic polymer with alpha-fluoride substitution.

The crosslinkers identified in claims 14 and 19 include:

• divinylbenzene;
• ethylene bisacrylamide;
• N,N'-bis(vinylsulfonylacetyl)ethylenediamine;
• 1,3-bis(vinylsulfonyl)-2-propanol;
• vinylsulfone;
• N,N'-methylenebisacrylamide;
• polyvinyl ether; and
• polyallyl ether.

A formulation using a different crosslinker could avoid claims 14, 15, or 19 while still raising issues under claims 1, 13, or 17.

What products are most closely associated with the patent?

Veltassa and patiromer

Veltassa is the principal marketed product associated with this patent landscape. FDA approved Veltassa in October 2015 for the treatment of hyperkalemia in adults. [3] Its active ingredient is patiromer, supplied as patiromer sorbitex calcium for oral suspension.

Veltassa is a nonabsorbed polymer. It binds potassium in the gastrointestinal tract and exchanges potassium for calcium. The FDA label identifies hyperkalemia treatment as the approved use and instructs administration as an oral suspension. [2]

The patent claims do not require the Veltassa brand, sorbitol, or the exact commercial excipient system. They focus on the potassium-binding polymer and its use.

Patiromer versus sodium zirconium cyclosilicate

Patiromer and sodium zirconium cyclosilicate are competing potassium binders but have materially different patent-risk profiles.

Attribute	Patiromer	Sodium zirconium cyclosilicate
Brand	Veltassa	Lokelma
Active material	Patiromer sorbitex calcium	Sodium zirconium cyclosilicate
Polymer	Crosslinked organic ion-exchange polymer	Inorganic crystalline zirconium silicate
Counterion	Calcium	Sodium
Primary sponsor	Vifor Pharma and affiliates	AstraZeneca
Patent 8,778,324 relevance	Directly relevant to claimed polymer class	Generally outside claimed organic polymer structure
FDA approval	2015	2018

US 8,778,324 is not a direct barrier to sodium zirconium cyclosilicate because the latter is not a crosslinked alpha-fluoroacrylic acid polymer.

When does US Patent 8,778,324 expire?

The patent has a nominal expiration date of November 20, 2029, based on the earliest claimed priority framework and the 20-year patent term applicable to the family. [1]

Milestone	Date
Earliest priority date	November 20, 2008
Patent issued	July 15, 2014
Nominal expiration	November 20, 2029
FDA approval of Veltassa	October 2015

The effective date should be confirmed against the USPTO patent-term record and any terminal disclaimer. Patent expiration does not itself authorize launch if other unexpired Veltassa patents, regulatory exclusivities, or litigation restraints remain in force.

What is the Orange Book status of patent 8,778,324?

The patent is relevant to the Veltassa Orange Book estate because it claims treatment of hyperkalemia using the polymer associated with the approved product. FDA Orange Book listings can include method-of-use patents when the patent claims an approved use and the sponsor submits an applicable use code. [4]

The practical significance of an Orange Book listing is procedural:

• an ANDA applicant may certify under Paragraph III that it will wait for patent expiration;
• it may file a Paragraph IV certification asserting that the patent is invalid, unenforceable, or not infringed;
• the NDA holder may file infringement litigation within 45 days;
• a timely suit can trigger a 30-month stay of ANDA approval under the Hatch-Waxman framework. [5]

The existence of a listing does not establish validity or infringement. Those questions depend on claim construction, the accused product, prosecution history, and the technical record.

What Paragraph IV risks apply to generic patiromer?

A generic patiromer applicant would face product-specific and method-of-use issues.

Product and polymer identity

The applicant must determine whether its active polymer is:

• an alpha-fluoroacrylic acid polymer;
• crosslinked with one of the listed or equivalent crosslinkers;
• supplied with a calcium counterion;
• within the claimed swelling-ratio limits; and
• used for the treatment of hyperkalemia.

A formulation that uses a different polymer composition may avoid claims 13 and 17 but could still fall within claim 1 if it has the required acid-group and electron-withdrawing-substituent arrangement.

Labeling risk

Claims 1, 13, and 17 are method claims. A generic applicant may attempt a section viii carve-out for patented uses, but that strategy is difficult where treatment of hyperkalemia is the core approved indication. A label that instructs use of the claimed polymer to treat hyperkalemia would strengthen an induced-infringement case.

Physical-property limitations

Claims 6, 7, and 18 depend on swelling ratio. These claims create analytical issues involving:

• the swelling medium;
• pH and ionic strength;
• equilibration time;
• particle size;
• calcium loading;
• measurement methodology; and
• whether the claim requires a batch-wide or representative value.

A generic product could dispute the test method or argue that its polymer exceeds the claimed threshold.

Which companies are challenging the Veltassa patent estate?

Public generic competition must be assessed at the ANDA and litigation level, not solely through patent databases. A Paragraph IV filing may remain confidential until litigation is filed or the applicant provides notice.

The key commercial parties in the relevant landscape are:

Company	Role
Vifor Pharma and related entities	Originator and principal Veltassa patent holder or licensing party
Fresenius Medical Care-related entities	Commercial and corporate affiliates associated with Vifor's renal business
Zydus	Generic pharmaceutical manufacturer with potential ANDA activity in the patiromer market
Lupin and other generic companies	Potential or reported participants in generic potassium-binder competition
AstraZeneca	Sponsor of competing Lokelma, not a direct 8,778,324 polymer target

A company-specific infringement conclusion cannot be drawn from the patent claims alone. The relevant question is whether the challenger has filed an ANDA, what certification it made, and whether the applicant's technical formulation falls within the claims.

What litigation and settlements affect patent 8,778,324?

The patent's litigation exposure should be separated into three categories:

1. Validity challenges, including anticipation, obviousness, written description, and enablement.
2. Infringement disputes, particularly over polymer structure, calcium form, and method-of-use labeling.
3. Settlement agreements, which may establish a licensed or delayed generic entry date without invalidating the patent.

A litigation docket naming Veltassa or patiromer does not necessarily mean that US 8,778,324 is the asserted patent. Patent-by-patent review of the complaint, claim charts, stipulations, and judgment is required.

No settlement date or authorized generic launch date should be inferred from the nominal November 2029 expiration date. Settlement terms may provide earlier entry, and separate patents may extend practical market protection beyond this patent.

How strong is the patent estate for patiromer?

US 8,778,324 has meaningful strength against products that replicate the central patiromer architecture.

Strengths

• Claims 13 and 17 target a defined polymer class.
• Claim 17 combines alpha-fluoroacrylic acid chemistry with calcium counterions.
• Method claims align with the approved hyperkalemia indication.
• Claims 18-20 provide narrower fallbacks for swelling ratio and bead form.
• The patent covers both a broad functional genus and narrower chemical embodiments.

Vulnerabilities

• Claim 1 uses broad functional language that may face written-description or enablement scrutiny depending on the full specification and prosecution record.
• The scope of "alpha-fluoroacrylic acid polymer" may require expert evidence.
• Swelling-ratio claims depend on test conditions.
• A non-calcium counterion could avoid claims 12, 16, and 17 while leaving claims 1 and 13 in play.
• A chemically distinct potassium-binding material may avoid the patent entirely.

The estate is strongest where a competing product uses the same alpha-fluoroacrylic acid backbone, calcium counterion, crosslinking strategy, and treatment indication.

What manufacturing and intellectual-property barriers remain?

The patent creates barriers beyond the chemical formula.

Polymer manufacturing

A commercial process must control:

• monomer purity;
• polymerization conversion;
• crosslink density;
• particle-size distribution;
• residual monomer;
• calcium exchange capacity;
• swelling behavior; and
• batch consistency.

Even if a process avoids the literal wording of a crosslinker claim, a product may encounter equivalence arguments if it produces substantially the same polymer structure and function.

Formulation

The claims reach certain dosage forms and physical presentations, including chewable tablets and beads. Veltassa is marketed as packets for oral suspension rather than as a conventional swallowed tablet. A future formulation could face separate formulation patents or claim issues even if it avoids the original presentation.

Regulatory development

Because patiromer is a nonabsorbed polymer, bioequivalence may not be established through conventional plasma pharmacokinetics alone. FDA product-specific requirements may examine binding performance, composition, particle characteristics, and comparative in vitro or clinical behavior. [2, 6]

How does patent 8,778,324 affect generic launch scenarios?

Launch scenario	Principal risk
Launch after November 2029	Residual risk from other unexpired Veltassa patents
Paragraph III certification	Delayed approval until the listed patent expires
Paragraph IV certification	Litigation, possible 30-month stay, and technical claim dispute
Section viii carve-out	Limited utility because hyperkalemia treatment is the core indication
Non-infringing polymer redesign	Requires avoiding both alpha-fluoroacrylic acid claims and the broader genus in claim 1
Authorized generic or settlement launch	Timing controlled by contract, litigation outcome, and other patents

A successful design-around would likely require more than changing the dosage form. The most consequential redesign variables are the acid-bearing monomer, electron-withdrawing substituent, crosslink chemistry, counterion, and method-of-use labeling.

Key takeaways

• US Patent 8,778,324 is a method-of-use patent directed to potassium-binding polymers for hyperkalemia.
• Claims 13 and 17 are the most relevant claims for patiromer-type products.
• Claim 17 specifically covers a crosslinked alpha-fluoroacrylic acid polymer with a calcium counterion.
• The nominal patent expiration date is November 20, 2029.
• The patent does not directly cover sodium zirconium cyclosilicate or other inorganic potassium binders.
• A generic patiromer applicant faces risks involving polymer identity, calcium form, swelling ratio, crosslinker selection, and hyperkalemia labeling.
• Avoiding claims 14, 15, 18, or 20 would not necessarily avoid claims 1, 13, or 17.
• Patent 8,778,324 should be evaluated together with the complete Veltassa Orange Book estate, prosecution history, FDA product-specific guidance, and any active ANDA litigation.

FAQs

Does US 8,778,324 cover patiromer?

It is directly relevant to patiromer-type products because its claims cover crosslinked alpha-fluoroacrylic acid polymers and, in claim 17, the calcium-counterion form associated with patiromer.

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

Changing the counterion may avoid claims requiring calcium, including claim 17, but it would not automatically avoid claims 1 or 13. The polymer backbone and treatment method would still require analysis.

Does the patent cover Veltassa chewable tablets?

Claim 9 covers administration in a chewable tablet, but Veltassa is approved and marketed as an oral suspension. The claim does not establish that every Veltassa formulation is a chewable tablet.

Is US 8,778,324 a composition-of-matter patent?

No. Its principal claims are method claims requiring treatment of hyperkalemia with a defined potassium-binding polymer.

Can a company launch a generic patiromer product in 2029?

Potentially, but the answer depends on the precise expiration date, any patent-term adjustment, Orange Book listings, litigation outcomes, settlements, regulatory approval, and other unexpired patents covering Veltassa or patiromer formulations.

References

1. United States Patent and Trademark Office. (2014). U.S. Patent No. 8,778,324, Potassium binding polymers.
2. U.S. Food and Drug Administration. (2024). Veltassa (patiromer) prescribing information.
3. U.S. Food and Drug Administration. (2015). FDA approves Veltassa to treat high potassium levels.
4. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
5. 21 U.S.C. § 355(j). Abbreviated applications for new drugs.
6. U.S. Food and Drug Administration. (2024). Product-specific guidance for patiromer for oral suspension.

Drugs Protected by US Patent 8,778,324

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate

International Family Members for US Patent 8,778,324

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	1732523		300924	Netherlands
European Patent Office	2269589		CA 2018 00003	Denmark
European Patent Office	1732523		300925	Netherlands
European Patent Office	1732523		122018000011	Germany
European Patent Office	1732523		2018C/004	Belgium
European Patent Office	1732523		C01732523/01	Switzerland