US Patent 7,381,428: Claim Scope, Exclusivity, Generic Risk and Lanthanum Carbonate Patent Landscape

US Patent 7,381,428 protects a narrow stabilized lanthanum carbonate formulation and methods of using or preparing it for hyperphosphatemia. Its central limitation is the combination of hydrated lanthanum carbonate with specified sugar excipients, within defined concentration ranges, that prevents detectable conversion to lanthanum hydroxycarbonate after severe heat-and-humidity exposure. The patent does not broadly cover lanthanum carbonate, Fosrenol, or every lanthanum carbonate formulation.

The commercial relevance is concentrated in formulation composition, excipient selection, hydrate state, and XRPD stability. It does not create biosimilar risk because lanthanum carbonate is a small-molecule inorganic drug, not a biologic.

What does US Patent 7,381,428 claim?

The patent has two independent method claims:

Claim	Independent subject matter	Required commercial activity
1	Method of treating hyperphosphatemia	Administering the stabilized lanthanum carbonate composition
7	Method of stabilizing a lanthanum carbonate pharmaceutical composition	Admixing lanthanum carbonate with specified mono- or disaccharides

Claims 2-6 depend from claim 1. Claims 8-12 depend from claim 7. The dependent claims repeat the same formulation limitations in the two independent claim groups.

The core composition must contain:

Lanthanum carbonate having the formula La2(CO3)3.xH2O.
A hydration value, x, from 0 to 10.
Elemental lanthanum at approximately 13.4%-33.3% by weight of the total composition, based on the ranges stated in the claims.
Dextrates, mannitol, sorbitol, or a mixture of those excipients.
The sugar excipient at 20%-80% by weight.
No observed lanthanum hydroxycarbonate in the XRPD pattern after exposure to 60°C and 95% relative humidity for at least seven days.

The claim text supplied contains a range written as "from 13.4-13.9% to 32.2-33.3%." That wording appears to combine hydrate-dependent elemental-lanthanum subranges. The examples explain the apparent structure: approximately 4-5 moles of water in the lanthanum carbonate changes the elemental-lanthanum percentage even when the nominal lanthanum carbonate weight percentage remains constant.

How broad is the independent treatment claim?

Claim 1 is narrower than a conventional composition-of-matter claim because it requires a treatment method and a specific stability result.

Required claim elements

A potential claim 1 infringement theory would generally need to establish:

Treatment of hyperphosphatemia.
Administration of the accused lanthanum carbonate product.
Lanthanum carbonate in the specified hydrated or anhydrous formula range.
Elemental lanthanum within the claimed percentage range.
Dextrates, mannitol, sorbitol, or an applicable mixture.
Sugar excipient concentration of 20%-80%.
Absence of detectable lanthanum hydroxycarbonate by the stated XRPD protocol after seven days at 60°C and 95% relative humidity.

The claim does not expressly require a tablet, chewable tablet, powder, suspension, or particular dose. A product in another oral dosage form could fall within the claim if it satisfies the compositional and stability limitations.

The claim also does not require a specific particle size, compression force, coating, dissolution profile, dose strength, packaging system, or manufacturing process. Those characteristics may affect whether the XRPD stability limitation is met, but they are not independently recited limitations.

What technical problem does the patent address?

Lanthanum carbonate can undergo decarboxylation under elevated temperature and humidity, producing lanthanum hydroxycarbonate. The claimed formulation uses sugar-based excipients to limit that transformation before administration.

The technical distinction is therefore not the phosphate-binding mechanism itself. Lanthanum carbonate binds dietary phosphate in the gastrointestinal tract, reducing phosphate absorption in patients with chronic kidney disease. The claimed distinction is preservation of the intended lanthanum carbonate solid form during storage.

The XRPD requirement is central. A composition can contain the listed excipient and still fall outside the claim if lanthanum hydroxycarbonate is observed after the specified stress test. Conversely, a formulation may face infringement risk if it uses a different manufacturing process but produces the claimed composition and stability result.

How do the dependent claims narrow the patent?

Claims 2 and 8: dextrates

These claims limit the sugar excipient to dextrates. Dextrates are the preferred excipient in the first and third disclosed examples.

A formulation using mannitol or sorbitol would not literally meet claims 2 or 8, although it could remain within independent claim 1 or claim 7 if all other limitations are met.

Claims 3 and 9: sorbitol

These claims limit the excipient to sorbitol. Sorbitol is used in the second disclosed formulation and is combined with glyceryl dibehenate.

Claims 4 and 10: dextrate formulation

The claimed formulation contains:

Ingredient	Weight percentage
Lanthanum carbonate	26.5%
Dextrates	69.3%
Colloidal silicon dioxide	2.0%
Talc	1.7%
Magnesium stearate	0.5%
Total	100.0%

The lanthanum carbonate has approximately 4-5 moles of water. This claim is narrower than claim 1 because it requires the stated excipients and exact percentages.

Claims 5 and 11: sorbitol formulation

Ingredient	Weight percentage
Lanthanum carbonate	63.6%
Sorbitol	30.4%
Glyceryl dibehenate	3.0%
Colloidal silicon dioxide	2.0%
Talc	1.0%
Total	100.0%

This formulation has a materially higher lanthanum carbonate loading and uses glyceryl dibehenate as a lubricant or processing aid.

Claims 6 and 12: higher-dextrate formulation

Ingredient	Weight percentage
Lanthanum carbonate	45.8%
Dextrates	51.1%
Colloidal silicon dioxide	2.1%
Magnesium stearate	1.0%
Total	100.0%

This formulation does not recite talc and has a lower dextrate percentage than claims 4 and 10.

What is the importance of the XRPD limitation?

The XRPD limitation is both a technical and litigation constraint.

The claim does not merely require a formulation that is intended to be stable. It requires that lanthanum hydroxycarbonate not be observed after a defined stress condition. A patent owner would likely need analytical evidence showing:

The identity and hydration state of the starting lanthanum carbonate.
The composition before stressing.
The temperature and relative humidity conditions.
The duration of exposure.
XRPD instrument parameters.
Detection limits and reference patterns.
Whether the absence of a hydroxycarbonate peak is reproducible.

A generic manufacturer could challenge infringement by showing that its product forms detectable lanthanum hydroxycarbonate under the claimed test. It could also challenge validity by arguing that the XRPD limitation is indefinite, not adequately enabled, or insufficiently reproducible. The strength of that defense would depend on the patent specification and prosecution history, not the claims alone.

The XRPD test also creates product-development risk. Small differences in hydrate level, excipient grade, granulation, residual moisture, particle size, compression, and packaging could change the result.

Does the patent cover all Fosrenol or lanthanum carbonate products?

No. The claims are not directed to all lanthanum carbonate products.

They do not cover a formulation that:

Uses calcium carbonate, sevelamer, ferric citrate, sucroferric oxyhydroxide, or another phosphate binder.
Uses lanthanum carbonate but no dextrates, mannitol, sorbitol, or qualifying mixture.
Uses one of those excipients below 20% or above 80% by weight.
Falls outside the claimed elemental-lanthanum range.
Produces observable lanthanum hydroxycarbonate under the specified XRPD test.
Contains a different active ingredient instead of lanthanum carbonate.
Is used for a non-hyperphosphatemia indication, subject to any applicable equivalents theory.

A competing lanthanum carbonate product could avoid literal infringement through a different excipient system, a different concentration, an alternative hydrate profile, or a demonstrably different solid-state stability result.

What patents protect lanthanum carbonate products beyond US 7,381,428?

The relevant patent landscape is broader than this single formulation patent. Commercial protection for a lanthanum carbonate product can include:

Patent category	Typical protected subject matter	Relevance to a generic
Active ingredient or salt patents	Lanthanum carbonate and related chemical forms	Usually limited if expired
Solid-state patents	Hydrate, polymorph, particle-size or crystallinity characteristics	Can affect API sourcing and formulation
Formulation patents	Stabilized tablets, excipients, granulation and moisture control	Directly relevant to finished-product design
Method-of-use patents	Treatment of hyperphosphatemia or renal disease	Relevant to labeling and induced-infringement risk
Manufacturing patents	Preparation, purification, drying and blending of lanthanum carbonate	Relevant to API suppliers
Packaging patents	Moisture-barrier packaging and storage systems	May provide design-around options
Regulatory exclusivity	New-drug, pediatric or other FDA exclusivity	Separate from patent rights

US 7,381,428 is principally a formulation and stability patent. It does not, based on the supplied claims, claim a manufacturing route for producing lanthanum carbonate or a broad method of phosphate binding.

What is the Orange Book status of US 7,381,428?

The supplied claims do not establish whether US 7,381,428 is currently listed in the FDA Orange Book, whether it was previously listed, or whether any listing was delisted or expired. Orange Book status must be determined from the FDA patent-listing record and the relevant Fosrenol reference-product entries, not from the claim text.[2]

For an abbreviated new drug application, the business impact depends on whether the patent is:

Listed against the reference drug.
Still within its enforceable term.
Associated with a method-of-use code.
Subject to a valid Paragraph IV certification.
Covered by a settlement or license.
Removed from the Orange Book or marked expired.

An Orange Book listing does not itself prove validity or enforceability. It creates a regulatory framework for patent certifications and potential statutory litigation.

When does US 7,381,428 lose exclusivity?

Patent expiration cannot be calculated reliably from the claims supplied. The relevant date depends on the patent's earliest effective nonprovisional priority date, any terminal disclaimer, patent-term adjustment, patent-term extension, and other USPTO continuity information.[1]

The statutory framework generally provides a patent term measured from the earliest effective nonprovisional filing date, subject to adjustments and extensions.[3] FDA regulatory exclusivity is separate. Fosrenol's approval date and any applicable regulatory exclusivity do not by themselves determine the patent term.[4]

A current freedom-to-operate analysis should treat the following as separate questions:

Whether the patent term has expired.
Whether any patent-term extension applies.
Whether a terminal disclaimer limits the term.
Whether the patent remains listed in the Orange Book.
Whether related continuation, divisional or foreign patents remain active.
Whether a settlement agreement restricts launch timing.

What Paragraph IV challenges could target this patent?

A Paragraph IV challenge could attack either the patent's validity or noninfringement.

Potential noninfringement positions

A generic applicant could certify that its product does not infringe because:

It uses an excipient outside the claimed group.
The sugar excipient concentration is outside 20%-80%.
Elemental lanthanum is outside the claimed range.
The hydrate state is outside the asserted range.
The XRPD test shows lanthanum hydroxycarbonate after stress.
The proposed labeling does not direct treatment within the claimed method.
The product does not contain one of the claimed exact formulations.

Potential invalidity positions

Potential validity challenges could include:

Anticipation by an earlier lanthanum carbonate formulation.
Obviousness based on combining known lanthanum carbonate with conventional tablet excipients.
Lack of written description for the full composition and concentration ranges.
Lack of enablement across the full hydrate and excipient ranges.
Indefiniteness of the elemental-lanthanum range or the phrase "substantial decarboxylation."
Indefiniteness or reproducibility problems associated with "not observed" in XRPD.
Double patenting, if related claims overlap with another patent family.

The best Paragraph IV strategy would likely combine a formulation design-around with a technical noninfringement position. A validity-only challenge would face greater uncertainty because the specification may contain experimental evidence supporting the excipient effect.

What generic entry risks exist for lanthanum carbonate?

The formulation claims create a targeted risk rather than a field-wide barrier.

Generic strategy	Risk under US 7,381,428	Commercial assessment
Copy the disclosed dextrate tablet	High if the patent is enforceable and listed	Weak design-around
Copy the disclosed sorbitol formulation	High	Weak design-around
Use mannitol within the claimed range	Potentially high under claim 1 or 7	Requires XRPD and range analysis
Use a different sugar or polyol	Lower literal-infringement risk	May require stability work
Reduce sugar below 20%	Lower literal-infringement risk	Could compromise stability
Use a non-sugar stabilizer	Lower literal-infringement risk	Requires formulation redevelopment
Use alternative packaging only	Uncertain	Packaging may not prevent composition claim coverage
Demonstrate hydroxycarbonate formation after stress	Supports noninfringement	Requires validated analytical testing
Use a different dosage form with the same composition	Risk remains	Dosage form is not a required limitation

The most important design-around variable is the stabilizing excipient system. A formulation using a nonclaimed excipient may avoid literal infringement, but it must still satisfy FDA quality, dissolution, bioequivalence and stability requirements.

How does this patent compare with competing phosphate-binder estates?

Lanthanum carbonate competes with several nonbiologic phosphate binders:

Product or active ingredient	Product type	Main patent-risk profile
Fosrenol, lanthanum carbonate	Chewable tablet, oral powder	Lanthanum formulation, solid-state and method patents
Renvela, sevelamer carbonate	Polymer phosphate binder	Polymer chemistry and formulation patents
Renagel, sevelamer hydrochloride	Polymer phosphate binder	Polymer and formulation patents
Auryxia, ferric citrate	Iron-based phosphate binder	Composition, formulation and method-of-use patents
Velphoro, sucroferric oxyhydroxide	Iron-based complex	Complex composition and formulation patents
Calcium acetate products	Inorganic salt	Generally lower formulation complexity

US 7,381,428 is narrower than a polymer or complex-inorganic patent estate because its claims focus on one active ingredient and a defined stabilization mechanism. It is potentially easier to design around, but its analytical limitation can complicate development if a candidate formulation falls near the claimed ranges.

What manufacturing and intellectual-property barriers remain?

The principal manufacturing barrier is control of moisture and hydrate state. Lanthanum carbonate with approximately four to five water equivalents must be blended with high levels of dextrates or sorbitol while maintaining consistent content uniformity and physical stability.

Key process variables include:

API hydration before blending.
Relative humidity during granulation and compression.
Excipient water activity.
Drying temperature.
Milling and particle-size distribution.
Lubricant concentration.
Tablet compression.
Container-closure moisture transmission.
Stability-indicating XRPD testing.

A manufacturer can potentially avoid the composition claims while still encountering separate API, manufacturing, formulation, or regulatory patents in the broader lanthanum carbonate family. Geographic coverage also varies. US 7,381,428 has no direct legal effect outside the United States, although corresponding foreign applications may create parallel risks in Europe, Japan, Canada, Australia and other markets.

What licensing and settlement issues affect lanthanum carbonate entry?

The claims supplied do not identify a license, covenant not to sue, reverse-payment settlement, authorized-generic arrangement or launch date. Such agreements cannot be inferred from patent language.

For commercial diligence, the relevant agreements would include:

Licenses from the patent owner or its successor.
Authorized-generic arrangements with the Fosrenol rights holder.
Paragraph IV litigation settlements.
Supply agreements for lanthanum carbonate API.
Technology-transfer agreements covering the stabilized formulation.
Co-promotion or regional commercialization agreements.

A license to the patent may not resolve risk from continuation patents or separate Orange Book-listed patents. The scope of each agreement must be mapped against the specific claims and territories.

Key Takeaways

US 7,381,428 is a narrow formulation and method patent centered on preventing lanthanum carbonate decarboxylation.
The principal limitations are the lanthanum hydrate range, elemental-lanthanum concentration, 20%-80% sugar excipient range and XRPD stability result.
Dextrates and sorbitol are expressly claimed; mannitol is included in the independent claims.
Claims 4-6 and 10-12 protect three highly specific formulations.
The patent does not broadly cover every lanthanum carbonate product or every phosphate-binder therapy.
A generic formulation using a different stabilizer, concentration, hydrate state or solid-state outcome may have a credible design-around position.
XRPD testing is likely to be central to both infringement and validity disputes.
Orange Book status, patent expiration, Paragraph IV history, litigation and settlement rights cannot be established from the claims text alone.
No biosimilar pathway applies because lanthanum carbonate is a small-molecule inorganic active ingredient.
Related formulation, API, manufacturing, method-of-use and foreign patents must be reviewed separately before launch.

Frequently Asked Questions

Is US 7,381,428 a composition patent or a method patent?

It is drafted as a method patent. Claims 1-6 cover treatment of hyperphosphatemia, while claims 7-12 cover stabilizing a lanthanum carbonate pharmaceutical composition.

Does a sorbitol-based lanthanum carbonate tablet automatically infringe?

No. It must also satisfy the claimed lanthanum concentration, sugar concentration, hydrate and XRPD stability limitations. Claims 3, 5, 9 and 11 create higher risk for formulations matching those limitations.

Can a generic use mannitol instead of dextrates?

Potentially. Mannitol is expressly included in the independent claims, so replacing dextrates with mannitol does not automatically avoid the patent. The full claim limitations must be assessed.

Does moisture-barrier packaging alone avoid the patent?

Not necessarily. The claims focus on the composition and its XRPD stability after stress. Packaging may affect the result but is not itself a complete design-around.

Are lanthanum carbonate products subject to biosimilar approval?

No. Lanthanum carbonate is not a biologic. A generic sponsor would generally pursue an abbreviated new drug application rather than a biosimilar application, subject to FDA requirements and any applicable listed-patent certifications.

References

United States Patent and Trademark Office. (n.d.). Patent Center. https://patentcenter.uspto.gov/
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.accessdata.fda.gov/scripts/cder/ob/
35 U.S.C. §§ 154, 156, 271, 282.
U.S. Food and Drug Administration. (n.d.). Fosrenol: Prescribing information. https://www.accessdata.fda.gov/-drugsatfda_docs/label/

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	056609	⤷ Start Trial
Austria	9809	⤷ Start Trial
Austria	E460169	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 7,381,428

Summary for Patent: 7,381,428