US Patent 7,553,479: Scope, Claims, Expiration, and Iron-Carbohydrate Patent Landscape

US Patent 7,553,479 protects a vialed injectable iron oxide complex using reduced carboxymethylated dextran with a defined carboxyl-group density and sufficient heat stability for terminal sterilization. The principal commercial relevance is to ferumoxytol-type intravenous iron formulations, including Feraheme. Claim 1 is limited by composition, excipient chemistry, packaging, injectability, and thermal stability. Claim 2 narrows the protection to products that can be terminally sterilized in the vial at approximately 121°C.

The patent’s likely statutory expiration is March 25, 2025, based on the reported March 25, 2004 priority date and the standard 20-year patent term. The claim set is therefore primarily relevant to historical generic-entry risk, infringement analysis for earlier commercial activity, and the technical lineage of ferumoxytol formulations.

What does US Patent 7,553,479 protect?

The patent protects a pharmaceutical composition in a vial containing an injectable reduced carboxymethylated dextran iron oxide complex. The protected dextran has:

Claim limitation	Requirement
Dosage form	Pharmaceutical composition
Container	Vial
Active complex	Injectable reduced carboxymethylated dextran iron oxide complex
Dextran chemistry	Reduced carboxymethylated dextran
Carboxyl density	At least 750 and less than 1,500 micromoles of carboxyl groups per gram of dextran
Thermal property	Stable at a temperature of at least about 100°C

Claim 2 adds a more commercially specific limitation: the injectable complex must be terminally sterilizable within the vial at approximately 121°C.

The claims do not expressly require a particular iron concentration, dose, vial volume, route other than injectability, particle-size distribution, pH, tonicity agent, surfactant, or clinical indication. Those omissions affect both infringement scope and validity analysis.

How should claim 1 of US 7,553,479 be construed?

Claim 1 is a combination claim. An accused product must satisfy every material limitation.

"Pharmaceutical composition in a vial"

The vial limitation narrows the claim to a packaged product, rather than an unfilled bulk intermediate or an iron-dextran complex sold only as a manufacturing component. A prefilled or sealed vial would likely fall within the ordinary commercial meaning of the limitation if the remaining elements are satisfied.

The claim does not specify vial material. Glass, polymer, or another container could potentially qualify, subject to the patent specification and applicable claim-construction principles.

"Injectable reduced carboxymethylated dextran iron oxide complex"

This limitation requires more than a physical mixture of iron oxide and dextran. The iron oxide must be associated with the specified dextran derivative as a complex, and the composition must be suitable for injection.

The term "reduced" is technically important. It generally refers to modification of reducing-end aldehyde functionality in the dextran starting material. The claim also requires carboxymethylation, which introduces carboxyl groups into the dextran backbone.

An iron oxide formulation using native dextran, non-carboxymethylated dextran, or a different carbohydrate ligand would present a potential noninfringement position, although equivalence issues could remain.

"At least 750 and less than 1500 micromole of carboxyl groups per gram"

This is the principal numerical limitation. The range is inclusive at the lower endpoint and exclusive at the upper endpoint:

750 micromoles per gram is included.
1,499 micromoles per gram is included if the measurement is valid.
1,500 micromoles per gram is excluded by the literal language.

The relevant measurement is carboxyl groups per gram of dextran, not necessarily per gram of the final iron-carbohydrate complex. Analytical method selection, sample preparation, moisture correction, and whether the calculation is based on dry dextran or formulated material can materially affect claim scope.

A formulation with 700 micromoles per gram would be outside the literal range. A formulation with 1,600 micromoles per gram would also be outside the literal range. A design-around using a chemically different ligand or a carboxyl density outside the range could reduce literal infringement risk.

"Stable at a temperature of at least about 100°C"

This is a functional limitation. The claim requires thermal stability at or above approximately 100°C, but the claim text does not define the precise duration, test method, degradation threshold, or acceptance criterion.

Those details are likely controlled by the specification, prosecution history, and expert evidence. In an infringement dispute, the parties would need to establish:

The temperature actually applied.
The duration of exposure.
The relevant degradation or aggregation threshold.
Whether stability is measured in the final vialed composition.
Whether the analytical method detects chemical degradation, physical aggregation, loss of injectability, or all three.

The limitation gives the claim practical relevance to sterilizable commercial products. It also creates a potential indefiniteness or enablement issue if the patent does not provide a sufficiently objective method for determining stability.

What does claim 2 add?

Claim 2 requires that the complex be terminally sterilizable within the vial at approximately 121°C.

Terminal sterilization is performed after filling and sealing the vial. It differs from aseptic processing, in which sterile components are assembled under controlled conditions without sterilizing the final sealed product by heat.

Claim 2 is narrower than claim 1 because it requires:

The vial to be filled and sealed before sterilization.
The iron oxide-dextran complex to tolerate the sterilization cycle.
The product to remain suitable for injection after exposure.
A sterilization temperature of about 121°C.

A product that is aseptically filled but cannot withstand terminal sterilization may fall within claim 1 if it satisfies the 100°C stability requirement, but it would not satisfy claim 2 on that basis alone.

What is the likely expiration date of US 7,553,479?

Event	Date or status
Earliest reported priority	March 25, 2004
US patent filing	2005, based on the priority family
Patent grant	July 7, 2009
Patent term basis	20 years from the earliest effective nonprovisional filing date
Expected statutory expiration	March 25, 2025
Patent term extension	No extension should be assumed without an FDA and USPTO-specific determination
Patent term adjustment	Must be confirmed from the USPTO patent record

The issue date does not control expiration. The operative date is generally tied to the earliest effective US nonprovisional filing in the priority chain, subject to terminal disclaimers, patent term adjustment, patent term extension, and abandonment events.

Because the reported expiration date is in the past, the patent should not presently block new US commercial activity unless a separate legal mechanism altered the term or a related patent remains enforceable.

Is US 7,553,479 listed in the Orange Book?

The patent is associated with the ferumoxytol product technology, but Orange Book listing must be distinguished from general ownership or technical relevance.

Issue	Analysis
Product association	Ferumoxytol injection, marketed as Feraheme
FDA pathway	New drug application
Patent subject matter	Drug composition and sterilizable vial formulation
Orange Book relevance	Depends on whether the patent was submitted and accepted for listing against the NDA
Paragraph IV relevance	Applies only if an ANDA applicant challenges a listed patent
Current blocking effect	Depends on the patent’s enforceability and any later-listed patents

A patent can be technically relevant to an FDA-approved product without being listed in the Orange Book. The FDA Orange Book and patent-listing records, not the patent specification alone, control whether an ANDA applicant must certify against the patent.[1]

How does the patent relate to ferumoxytol and Feraheme?

Ferumoxytol is an intravenous iron replacement product consisting of an iron oxide-carbohydrate complex. Feraheme was developed by Advanced Magnetics and later commercialized by AMAG Pharmaceuticals, which was acquired by Allergan and later became part of Covis Pharma’s commercial history.

The claim architecture of US 7,553,479 aligns with a formulation problem specific to iron-carbohydrate complexes: creating an injectable product that can withstand high-temperature sterilization without unacceptable aggregation, precipitation, chemical degradation, or loss of injectability.

The patent does not claim every ferumoxytol product in the abstract. A competing iron-carbohydrate product would need to satisfy the specific dextran chemistry, carboxyl-density range, vial, injectability, and stability limitations.

What other patents protect ferumoxytol and related iron-carbohydrate products?

The relevant patent estate is broader than US 7,553,479. It may include separate families directed to the following subject matter:

Patent category	Typical protected subject matter	Commercial significance
Composition patents	Iron oxide associated with dextran or modified dextran	Core product identity
Formulation patents	Concentration, pH, excipients, viscosity, osmolality, and stability	Product-specific formulation coverage
Process patents	Reduction, carboxymethylation, iron oxide formation, complexation, and purification	Manufacturing barriers
Sterilization patents	Heat stability and terminal sterilization in final containers	Vialed commercial presentation
Method-of-use patents	Treatment of iron-deficiency anemia or chronic kidney disease	Potential method-of-use certification
Delivery patents	Intravenous administration and dosing schedules	Regulatory and commercial differentiation
Manufacturing controls	Particle size, aggregation, free iron, and impurity specifications	Process-dependent infringement risk

US 7,553,479 is strongest where a competitor uses a reduced carboxymethylated dextran with a carboxyl density within the claimed window and packages the product in a vial. It is weaker against products using non-dextran carbohydrate shells, substantially different ligand chemistry, or formulations that cannot withstand the claimed heat conditions.

How strong is the patent estate for ferumoxytol?

The estate’s strength depends on whether protection is evaluated before or after the 2025 expiration date.

Technical strength

The patent has useful technical specificity. The carboxyl-density range is measurable, and the terminal-sterilization limitation maps to a commercially important manufacturing attribute. A composition claim tied to both chemical structure and performance can be difficult to design around if the sponsor’s formulation necessarily uses the claimed dextran derivative.

Validity vulnerabilities

Potential validity issues include:

Written-description support for the full 750 to less-than-1,500 micromole-per-gram range.
Enablement across all iron oxide and dextran combinations within the range.
Definiteness of "stable" and "about 100°C."
Anticipation by earlier iron-dextran or carboxymethylated dextran formulations.
Obviousness based on known carboxymethylation, reduction, and heat sterilization techniques.
Whether "terminally sterilizable" supplies a measurable structural or performance boundary.

The claim’s combination of numerical chemistry and thermal performance can support patentability, but it also creates dependence on analytical proof.

Commercial strength

The patent was commercially meaningful during the period when a generic or follow-on ferumoxytol manufacturer needed to replicate the vialed, heat-sterilized presentation. Its value declined substantially after expiration and after the emergence of later patents, FDA approvals, and alternative manufacturing approaches.

What generic entry risks existed for ferumoxytol?

An ANDA applicant seeking approval for a generic ferumoxytol injection would typically evaluate:

Whether the reference product’s formulation falls within the claim.
Whether the product is supplied in a vial.
Whether the dextran is reduced and carboxymethylated.
Whether carboxyl density is within the claimed range.
Whether the product is stable at approximately 100°C.
Whether terminal sterilization at approximately 121°C is used.
Whether any listed patents remain unexpired.
Whether the applicant can use a Paragraph IV certification.
Whether the sponsor can assert later formulation or method-of-use patents.

The principal design-around strategies would include using a different carbohydrate coating, changing the degree of carboxymethylation, moving outside the claimed carboxyl-density range, changing the sterilization method, or using a formulation that does not satisfy the thermal-stability limitation.

A design-around that merely changes iron concentration may not avoid infringement because claim 1 does not specify a particular iron concentration.

What patent litigation and settlement issues affect US 7,553,479?

The supplied claim text does not establish a litigation history, Paragraph IV settlement, or enforceability ruling for US 7,553,479. Those issues must be evaluated separately from claim scope.

For an ANDA dispute, the key legal questions would have been:

Whether the patent was listed for Feraheme.
Whether the ANDA included a Paragraph IV certification.
Whether the NDA holder filed suit within the statutory period.
Whether a 30-month stay applied.
Whether any settlement restricted generic launch.
Whether the patent expired before judgment or launch.

A patent-expiration analysis should also distinguish this patent from later patents covering ferumoxytol formulations, administration regimens, or manufacturing methods. Expiration of US 7,553,479 would not automatically eliminate all patent risk for the product.

How does US 7,553,479 compare with formulation and method-of-use patents?

US 7,553,479 is a product-and-packaging patent with a functional stability requirement. It differs from method-of-use patents, which protect administration or treatment steps, and from process patents, which protect how the iron-carbohydrate complex is manufactured.

Patent type	Infringement focus	Typical generic defense
US 7,553,479-type composition claim	Product chemistry and vial presentation	Change ligand chemistry or carboxyl density
Formulation claim	Final product composition	Alter excipients, concentration, or pH
Method-of-use claim	Prescribing or administration instructions	Carve out protected indication or regimen
Process claim	Manufacturing steps	Use a noninfringing process
Sterilization claim	Final-container heat treatment	Use aseptic processing or another validated cycle

Composition claims usually present greater commercial risk than method-of-use claims because an ANDA product may infringe regardless of the label if the product itself satisfies the claim. Process claims may be difficult to enforce because manufacturing occurs outside public view.

What geographic coverage does the patent provide?

US 7,553,479 provides rights only in the United States. Corresponding applications may exist in Europe, Canada, Japan, Australia, and other jurisdictions, but foreign family members have separate claims, prosecution histories, expiration dates, maintenance requirements, and litigation outcomes.

A US freedom-to-operate conclusion cannot be exported to Europe or other markets. The relevant foreign analysis must examine:

National-phase or direct application status.
Patent grant and lapse status.
Local claim amendments.
Supplementary protection certificates.
Patent-term extensions.
Regulatory exclusivity.
Local generic or biosimilar pathways.

The product is a chemically defined iron-carbohydrate complex, not a biologic. Biosimilar rules generally do not control the US regulatory pathway. A follow-on applicant would normally pursue an ANDA or another drug application pathway rather than a biosimilar application under section 351(k) of the Public Health Service Act.[2]

Key Takeaways

US 7,553,479 claims a vialed injectable reduced carboxymethylated dextran iron oxide complex.
Claim 1 requires 750 to less than 1,500 micromoles of carboxyl groups per gram of dextran.
The product must be stable at approximately 100°C or higher.
Claim 2 requires terminal sterilization in the vial at approximately 121°C.
The claim does not specify iron concentration, dose, vial volume, pH, or particle size.
The patent’s reported expiration date is March 25, 2025, subject to USPTO term adjustments or other term events.
The patent was technically relevant to ferumoxytol-type injectable iron products and their heat-sterilized vial presentations.
Expiration of this patent does not eliminate risk from later composition, formulation, manufacturing, or method-of-use patents.
The product is a small-molecule drug formulation, so biosimilar analysis is generally not the primary US competitive pathway.
The strongest historical design-around options involved changing the carbohydrate chemistry, carboxyl density, or sterilization approach.

FAQs About US Patent 7,553,479

Does US 7,553,479 cover all ferumoxytol products?

No. It covers products meeting each claim limitation, including the reduced carboxymethylated dextran chemistry, the specified carboxyl-density range, vial presentation, injectability, and thermal-stability requirement.

Does a ferumoxytol product sterilized aseptically infringe claim 2?

Not necessarily. Claim 2 requires terminal sterilization within the vial at approximately 121°C. An aseptically filled product may avoid claim 2, but it could still implicate claim 1 if it satisfies the broader composition and 100°C stability limitations.

Is 1,500 micromoles per gram within claim 1?

No. The language requires "less than 1500 micromole" per gram. The upper endpoint is excluded literally.

Can a different dextran derivative avoid infringement?

Potentially. A non-carboxymethylated dextran, a non-reduced dextran, or a different carbohydrate ligand may avoid one or more literal limitations. Equivalence and prosecution-history issues would still require separate analysis.

Does expiration of US 7,553,479 permit immediate generic launch?

Not by itself. Generic launch also depends on FDA approval, Orange Book-listed patents, regulatory exclusivity, later patents, litigation outcomes, and any enforceable settlement restrictions.

References

U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations (Orange Book).
U.S. Food and Drug Administration. (2024). Feraheme (ferumoxytol injection) prescribing information.
United States Patent and Trademark Office. (2009). U.S. Patent No. 7,553,479, pharmaceutical composition comprising an injectable reduced carboxymethylated dextran iron oxide complex.
U.S. Patent and Trademark Office. (2024). Patent term adjustment and patent term extension records.
U.S. Food and Drug Administration. (2024). Electronic Orange Book patent and exclusivity information.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	1169062	⤷ Start Trial	C300558	Netherlands	⤷ Start Trial
European Patent Office	1169062	⤷ Start Trial	CA 2012 00050	Denmark	⤷ Start Trial
European Patent Office	1169062	⤷ Start Trial	92114	Luxembourg	⤷ Start Trial
European Patent Office	1169062	⤷ Start Trial	C01169062/01	Switzerland	⤷ Start Trial
European Patent Office	1169062	⤷ Start Trial	1290043-7	Sweden	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 7,553,479

Summary for Patent: 7,553,479