United States Patent 7,459,151: Scope, Claim Construction, Expiration, and Sevelamer Patent Landscape

U.S. Patent No. 7,459,151 covers oral use of a crosslinked, water-insoluble polyallylamine polymer to remove phosphate from a patient or reduce serum phosphate. The claims are directed to a method of treatment rather than a composition, polymer-production process, dosage regimen, or disease-specific indication. The patent is associated with the sevelamer phosphate-binder technology used in Renagel and Renvela.

The patent’s principal commercial relevance was protection of sevelamer-based phosphate-binding therapy. Its term has expired, eliminating current U.S. infringement risk under the patent itself. Later patents directed to sevelamer formulations, manufacturing processes, dosage forms, and other product attributes must be analyzed separately.

What does U.S. Patent 7,459,151 cover?

The patent covers oral administration of a pharmaceutical composition containing a crosslinked, water-insoluble polyallylamine copolymer for phosphate removal or serum-phosphate reduction.

Its two independent claims are:

Independent claim	Protected activity	Therapeutic result
Claim 1	Oral administration to a patient of a therapeutically effective amount of the defined polymer composition	Removal of phosphate
Claim 11	Oral administration to a patient of a therapeutically effective amount of the defined polymer composition	Decrease in serum phosphate

Both independent claims require the same core polymer architecture. The principal differences are the claimed therapeutic result.

The patent does not claim every phosphate binder. A potentially infringing product must satisfy the claim limitations relating to:

Oral administration.
A patient in need of phosphate removal or serum-phosphate reduction.
A therapeutically effective amount.
A pharmaceutical composition.
A crosslinked, water-insoluble polyallylamine copolymer.
The specified repeat-unit structure.
A negatively charged counterion represented by X−.

How should the claims of Patent 7,459,151 be construed?

The polymer limitation

The central limitation is a “crosslinked, water insoluble polyallylamine copolymer.” This language narrows the claims to an insoluble, crosslinked polymer containing polyallylamine-derived repeat units. Soluble polyallylamine, non-crosslinked polyallylamine, and unrelated inorganic or organic phosphate binders fall outside the literal scope.

The structural formulae incorporated into the claims define the repeat-unit arrangement. Because the supplied claim text omits the actual drawings or embedded formulae, claim construction must rely on the issued patent specification and file history for the precise ratio and arrangement of the repeat units.

The term “copolymer” is important. It indicates that the claimed material is not merely a homopolymer in an arbitrary physical form. The claim requires a polymer containing the claimed repeat units together with crosslinking functionality.

The “consists of” limitation

The claims state that the copolymer “consists of a crosslinking agent and repeat units” represented by the specified formulae. “Consists of” is a closed transitional phrase under conventional U.S. patent interpretation.

That wording can exclude polymer constituents materially outside the listed components, subject to the established exception for impurities and components that do not materially affect the claimed invention. It creates a narrower limitation than “comprises.”

The closed language applies to the defined polyallylamine copolymer. It does not necessarily exclude conventional excipients, carriers, lubricants, coatings, or other ingredients from the overall pharmaceutical composition, because claims 5 through 7 expressly permit one or more carriers.

The counterion limitation

X− is defined as a negatively charged counterion. Dependent claims 8 through 10 and 18 through 20 narrow X− to chloride.

The chloride claims correspond to sevelamer hydrochloride-type material. The broader independent claims can encompass other negatively charged counterions if the polymer otherwise satisfies the structural, crosslinking, insolubility, and therapeutic-use limitations. Sevelamer carbonate uses carbonate-associated counterions and is commercially distinct from sevelamer hydrochloride, although both are based on crosslinked polyallylamine chemistry.

The therapeutic-use limitation

The claims require treatment of “a patient in need thereof.” A product administered for non-therapeutic laboratory use, industrial phosphate removal, or a purpose unrelated to patient treatment would not satisfy this limitation.

Claim 1 requires phosphate removal. Claim 11 requires a decrease in serum phosphate. The claims do not expressly limit treatment to chronic kidney disease, dialysis, hyperphosphatemia, or a specified renal stage. Those conditions are central to the commercial use of sevelamer, but the claim language is broader.

What do the dependent claims add?

The 20 claims form two parallel claim sets.

Claims	Added limitation
1 and 11	Broad method claims
2 and 12	Epichlorohydrin crosslinking agent
3 and 13	Crosslinking agent at about 2% to about 20% by weight
4 and 14	Epichlorohydrin plus 2% to about 20% crosslinker
5, 6, 7 and 15, 16, 17	One or more carriers
8, 9, 10 and 18, 19, 20	Chloride counterion

The most commercially relevant subcombination is found in claims 4 and 14, together with claims 7 and 17 or the chloride claims. These claims require:

A crosslinked, water-insoluble polyallylamine copolymer.
Epichlorohydrin as the crosslinking agent.
About 2% to about 20% crosslinking agent by polymer weight.
Optional carriers.
In some claims, chloride as the counterion.
Oral treatment for phosphate removal or serum-phosphate reduction.

The numerical range is an approximate range. A formulation outside the stated range could avoid literal infringement of claims 3, 4, 13, and 14, but could remain relevant to the broader independent claims if all other limitations are met.

Which commercial products are most closely related to Patent 7,459,151?

Renagel and sevelamer hydrochloride

Renagel is sevelamer hydrochloride, a nonabsorbed phosphate binder developed by GelTex Pharmaceuticals and commercialized by Genzyme, later part of Sanofi. It was approved by the FDA in 1998 for control of serum phosphorus in patients with chronic kidney disease on dialysis.

Sevelamer hydrochloride is a crosslinked polyallylamine polymer containing chloride-associated amine groups. It is the closest commercial product to the chloride-specific claims.

Renvela and sevelamer carbonate

Renvela is sevelamer carbonate. The FDA approved Renvela in 2007. The product was developed as a carbonate-counterion alternative to sevelamer hydrochloride and is available in tablets and powder for oral suspension.

Renvela is closely related to the patent’s broad polymer and therapeutic-use claims, but the chloride-dependent claims do not read literally on a carbonate-counterion product. The broader claims remain the more relevant claims for sevelamer carbonate analysis, subject to the precise structural disclosure and claim construction.

Product	Active polymer	Counterion	FDA approval	Relationship to Patent 7,459,151
Renagel	Sevelamer	Hydrochloride	1998	Strongest relationship to chloride claims
Renvela	Sevelamer	Carbonate	2007	Relevant to broad claims; generally outside chloride-only claims
Generic sevelamer hydrochloride	Sevelamer	Hydrochloride	Multiple ANDA approvals	Historically relevant to claims 1-10
Generic sevelamer carbonate	Sevelamer	Carbonate	Multiple ANDA approvals	Historically relevant to broad claims and later formulation patents

When did Patent 7,459,151 lose exclusivity?

Patent 7,459,151 is no longer an enforceable U.S. patent. Its statutory term expired before 2025. The precise expiration date should be taken from the USPTO Patent Center record, including any patent-term adjustment, terminal disclaimer, or other term event recorded for the patent.

The patent’s expiration means:

It cannot support a new U.S. patent-infringement action.
A generic applicant no longer needs to defeat this patent through a Paragraph IV certification.
The patent cannot block manufacture, sale, or approval of sevelamer products by itself.
Later patents covering formulations, manufacturing processes, or dosage forms may still create separate exposure.

Patent expiration does not erase historical infringement claims that accrued while the patent was enforceable. It also does not invalidate later-issued patents in the same product family.

What was the Orange Book status of Patent 7,459,151?

Patent 7,459,151 was associated with the Renvela and/or sevelamer product patent landscape through FDA Orange Book listing activity. Orange Book listing is product-specific and does not itself establish that every claim of a patent covers every formulation of the listed drug.

The listing question must be evaluated against:

The specific NDA.
The drug strength and dosage form.
The patent-use code.
The date of listing and delisting.
Whether FDA accepted the patent as a drug-substance, drug-product, or method-of-use patent.

For an ANDA applicant, an Orange Book-listed patent historically could require one of four certifications:

Certification	Meaning
Paragraph I	No patent information listed
Paragraph II	Patent has expired
Paragraph III	Applicant will wait until patent expiration
Paragraph IV	Patent is invalid, unenforceable, or not infringed

After expiration, Patent 7,459,151 is ordinarily handled through a Paragraph II certification for a newly filed ANDA, although the applicant must evaluate the current Orange Book record and any remaining listed patents.

Were there Paragraph IV challenges to sevelamer products?

Generic sevelamer applicants faced Orange Book patents covering Renvela, Renagel, formulations, dosage forms, and related manufacturing technology. Paragraph IV disputes were directed at the live patents in the applicable Orange Book listings, not only at Patent 7,459,151.

The commercial disputes typically involved:

Sevelamer carbonate tablets.
Sevelamer carbonate powder for oral suspension.
Sevelamer hydrochloride tablets.
Powder-processing and particle-size limitations.
Excipient systems and tablet properties.
Method-of-use claims for phosphate control.

A Paragraph IV certification against one patent does not eliminate other patents. Generic launch timing therefore depended on the entire listed patent set, settlement terms, pediatric exclusivity, regulatory exclusivity, and the applicant’s formulation.

What later patents created barriers around sevelamer?

The sevelamer estate extended beyond the polymer-and-use claims in Patent 7,459,151. The main patent categories were:

Core polymer patents

Earlier patents described crosslinked polyallylamine polymers and their use as phosphate binders. These patents established the foundational technology behind sevelamer hydrochloride and related polymers.

Counterion and product patents

Separate patent activity addressed sevelamer carbonate and other counterion forms. These patents could distinguish carbonate products from hydrochloride products even when the underlying polymer backbone was similar.

Formulation patents

Later patents focused on:

Powder for oral suspension.
Tablet composition.
Disintegration and dissolution properties.
Taste masking.
Stability.
Particle-size distribution.
Bulk density.
Reduced pill burden.
Excipient selection.

A generic product can avoid a broad expired method patent and still face infringement allegations under a later formulation patent.

Manufacturing patents

Manufacturing claims can cover:

Crosslinking conditions.
Epichlorohydrin level.
Reaction order.
Washing and purification.
Drying.
Milling.
Particle-size control.
Conversion between counterion forms.

These patents are commercially significant because process changes can affect binding capacity, tabletability, suspension behavior, and regulatory comparability.

Method-of-use patents

Method patents may cover:

Treatment of hyperphosphatemia.
Use in dialysis patients.
Administration with meals.
Dose titration.
Treatment of specific renal populations.
Combination with other phosphate binders.

Patent 7,459,151 is a method-of-use patent, but its language is not limited to a narrow renal-disease subgroup or a specified dosing schedule.

How strong is the patent estate represented by Patent 7,459,151?

The patent had meaningful historical scope but limited present commercial value because it has expired.

Factor	Assessment
Chemical breadth	Moderate. Limited to crosslinked, water-insoluble polyallylamine copolymers
Therapeutic breadth	Broad. Covers phosphate removal and serum-phosphate reduction without a narrow disease limitation
Dosage limitation	None stated
Route limitation	Oral administration required
Counterion scope	Broad independent claims; chloride-specific dependent claims
Crosslinker limitation	Epichlorohydrin appears only in dependent claims
Formulation scope	Broad composition language, with carriers expressly permitted in dependent claims
Current enforceability	None after expiration
Historical generic relevance	High for sevelamer products
Current blocking value	None for this patent alone

The absence of a specific dose, tablet size, administration schedule, or renal-disease diagnosis made the independent claims potentially broad against sevelamer products. The requirement for a specific polymer class and oral phosphate-binding use limited their application to competing binders outside the polyallylamine platform.

What generic launch risks exist after expiration?

Patent 7,459,151 no longer creates a standalone launch barrier. Current generic launch risk instead depends on the product-specific patent and regulatory record.

Sevelamer hydrochloride

The primary risks are later formulation or manufacturing patents, regulatory requirements for demonstrating pharmaceutical equivalence, and commercial competition from existing generic suppliers. A product using chloride-counterion sevelamer is more closely aligned with claims 8 through 10 and 18 through 20, but those claims are expired.

Sevelamer carbonate

The principal issues are formulation and product-performance patents, particularly for powder and tablet products. A carbonate product generally avoids the chloride-only claims but may still have historically implicated the broad independent claims and later carbonate-specific patents.

Label strategy

Because the core commercial use is phosphate control, a skinny-label strategy may have limited practical value where the approved generic indication substantially overlaps the branded indication. Method-of-use analysis must be performed against each unexpired Orange Book patent and its use code.

Which companies have been involved in sevelamer competition?

The principal entities associated with the sevelamer market include:

Genzyme Corporation, the original developer and commercializer.
Sanofi, following its acquisition of Genzyme.
GelTex Pharmaceuticals, the original technology company.
Teva Pharmaceutical Industries.
Dr. Reddy’s Laboratories.
Amneal Pharmaceuticals.
Impax Laboratories and related commercial entities.
Other ANDA applicants and generic suppliers.

The relevant competitive distinction is no longer ownership of Patent 7,459,151. It is control of approved formulations, supply reliability, manufacturing economics, and any surviving formulation or process patents.

What is the revenue exposure associated with this patent?

Patent-specific revenue exposure is historical because the patent has expired. The underlying products generated substantial commercial revenue in the phosphate-binder market, but Patent 7,459,151 cannot now preserve that revenue through exclusivity.

Revenue analysis should separate:

Renagel revenue from sevelamer hydrochloride.
Renvela revenue from sevelamer carbonate.
Authorized generic or licensed generic revenue.
Revenue protected by other live patents.
Revenue exposed to generic substitution after regulatory and patent barriers ended.

The economic value of the patent during its enforceable term came from broad method coverage across sevelamer products. Its current value is primarily historical, litigation-related, and relevant to freedom-to-operate analysis for past conduct.

Key Takeaways

Patent 7,459,151 covers oral treatment using a crosslinked, water-insoluble polyallylamine copolymer to remove phosphate or reduce serum phosphate.
Claims 1 and 11 are the two independent method claims.
Dependent claims narrow the polymer to epichlorohydrin crosslinking, a 2% to 20% crosslinker range, carriers, and chloride counterions.
The patent is closely associated with sevelamer hydrochloride and is also relevant to the broader sevelamer product class.
The claims do not require a specific dose, tablet strength, dialysis status, renal diagnosis, or dosing schedule.
The patent has expired and cannot independently block current U.S. generic launch.
Later patents covering sevelamer carbonate, formulations, particle size, manufacturing, and dosage forms created the more important historical Paragraph IV and launch issues.
Orange Book analysis must be performed by NDA, dosage form, patent-use code, and current listing status.
Current commercial risk lies in surviving product and process patents, regulatory requirements, supply economics, and generic competition, not in Patent 7,459,151 itself.

FAQs About U.S. Patent 7,459,151

Does Patent 7,459,151 cover Renagel?

Historically, yes. Renagel contains sevelamer hydrochloride, which is closely aligned with the patent’s chloride-counterion and crosslinked polyallylamine limitations. The patent is expired.

Does Patent 7,459,151 cover Renvela?

The broad claims are relevant to sevelamer carbonate because they do not expressly require chloride. The chloride-specific dependent claims do not literally cover carbonate-counterion sevelamer.

Is sevelamer a biologic subject to biosimilar approval?

No. Sevelamer is a nonabsorbed synthetic polymer drug, not a biologic. Generic versions are approved through the ANDA pathway rather than the biosimilar pathway.

Does patent expiration eliminate FDA exclusivity?

No. Patent expiration and FDA regulatory exclusivity are separate concepts. For sevelamer products, approval status, Orange Book listings, pediatric exclusivity, and product-specific patents must be reviewed independently.

Can a company still be sued under Patent 7,459,151?

A company may face claims concerning alleged infringement that occurred before expiration, subject to applicable limitation periods and other defenses. The expired patent cannot support a new claim based solely on post-expiration conduct.

References

U.S. Patent and Trademark Office. (2008). U.S. Patent No. 7,459,151, methods for removing phosphate from a patient. U.S. Department of Commerce.
U.S. Food and Drug Administration. (1998). Renagel (sevelamer hydrochloride) prescribing information. Center for Drug Evaluation and Research.
U.S. Food and Drug Administration. (2007). Renvela (sevelamer carbonate) prescribing information. Center for Drug Evaluation and Research.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. Center for Drug Evaluation and Research.
U.S. Food and Drug Administration. (2024). Orange Book: Approved drug products with therapeutic equivalence evaluations. Center for Drug Evaluation and Research.
U.S. Patent and Trademark Office. (2024). Patent Center: U.S. Patent No. 7,459,151. U.S. Department of Commerce.
U.S. Food and Drug Administration. (2023). Approved drug product labeling for sevelamer hydrochloride and sevelamer carbonate. Center for Drug Evaluation and Research.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	0716606	⤷ Start Trial	CA 2002 00003	Denmark	⤷ Start Trial
European Patent Office	0716606	⤷ Start Trial	SPC/GB02/011 200210	United Kingdom	⤷ Start Trial
European Patent Office	0716606	⤷ Start Trial	SPC004/2002	Ireland	⤷ Start Trial
European Patent Office	0716606	⤷ Start Trial	C00716606/01	Switzerland	⤷ Start Trial
European Patent Office	0716606	⤷ Start Trial	CA 2009 00048	Denmark	⤷ Start Trial
European Patent Office	0716606	⤷ Start Trial	C300428	Netherlands	⤷ Start Trial
European Patent Office	0716606	⤷ Start Trial	91629	Luxembourg	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 7,459,151

Summary for Patent: 7,459,151