US Patent 11,851,504: Scope, Claim-Charting Boundaries, and US Landscape for Hydrogenated Dextran-Fe Oxyhydroxide Complexes
What is US Drug Patent 11,851,504 claiming at its core?
US 11,851,504 claims an iron oligosaccharide complex made by stably associating a hydrogenated oligosaccharide with ferric oxyhydroxide, where the oligosaccharide is derived from dextran (hydrogenated dextran). The complex is defined by three functional/structural pillars:
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Oligosaccharide identity and micro-composition
- Hydrogenated oligosaccharide derived from dextran
- Low molecular weight: Mw < 3,000 Da (independent claim 1), with multiple preferred windows (claims 6-11)
- Narrower distribution and low residual extremes:
- 90 wt% below 3,500 Da; 10 wt% highest fraction below 4,500 Da (claim 6)
- “Dimer saccharide” content capped (claims 13-15)
- “Monomer saccharide” content capped (claim 16)
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Complex composition
- Ferric oxyhydroxide in stable association with the hydrogenated oligosaccharide (claims 1, 22-23)
- Iron content is constrained in dependent composition claims (claims 12, 18-20)
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Performance durability benchmark
- The iron complex has an in vitro half-life (hydrolysis of Fe3+) of ≥ 18.3 hours (claims 1, 22-23)
- Half-life is tested by a defined assay using optical absorbance at 287.3 nm under 0.24 M HCl and 0.9% NaCl acidic solution (claim 2)
- Additional ranges push durability higher (claim 24 and recaptured in 25-26)
This patent is tightly framed around “stable association” durability under acidic hydrolysis conditions and specific dextran-derived hydrogenated oligomer quality (molecular weight distribution plus low monomer/dimer impurities).
How broad are the independent claims (and what exactly narrows the scope)?
Claim 1 (independent): General scaffold
Claim 1 defines:
- Compound: hydrogenated oligosaccharide in stable association with ferric oxyhydroxide
- Hydrogenated oligosaccharide: Mw < 3,000 Da
- Derived from dextran
- In vitro half-life ≥ 18.3 hours
- (Half-life definition is later specified in claim 2)
Key implication for scope: Claim 1 reads on any hydrogenated dextran oligomer below 3,000 Da that forms the ferric oxyhydroxide complex meeting the ≥18.3-hour hydrolysis durability. It is not limited by:
- specific anomeric linkage in the independent claim (linkage appears in claim 22)
- iron loading percentage (only in dependent claim 12)
- specific apparent molecular weight (MP) window (claims 3-5)
- explicit “alpha 1,6-glucosidic” linkage (claim 22)
Claim 22 (independent-style “narrower compound set”): Linkage + MW + MP
Claim 22 specifies:
- α1,6-glucosidic bonds joining monomer units
- Hydrogenated dextran oligomer Mw 850-1,150 Da
- In vitro half-life ≥ 18.3 hours
- MP 130,000-160,000 Da
Scope effect: Adds structural specificity (α1,6 linkage) and a narrower oligomer MW window plus a narrower complex MP range.
Claim 23 (independent-style “alias + derived-from limitation”): Hydrogenated dextran
Claim 23 states:
- Hydrogenated dextran oligosaccharide (explicitly “hydrogenated dextran oligosaccharide”)
- Mw < 3,000 Da
- in vitro half-life ≥ 18.3 hours
Scope effect: Claim 23 looks like a recapture that is narrower than claim 1 only by the “derived from dextran” statement being made explicit. Functionally, it tracks the same MW and half-life requirements.
What do the dependent claims add (claim gating variables)?
1) Assay and half-life measurement method (claim 2)
Claim 2 narrows infringement-to-lab-conditions by defining:
- half-life measured by rate of hydrolysis of Fe3+ in:
- 0.24 M HCl
- 0.9% NaCl acidic solution
- measurement: optical absorbance at 287.3 nm
- half-life definition: time when absorbance is half of the value at t = 0
Practical scope effect: A product can be “durable” in a colloquial sense but may fail to meet the specific A287.3 nm hydrolysis half-life criterion under these exact acid matrices.
2) Apparent molecular weight (MP) gating (claims 3-5)
These claims impose a “complex size” window:
- Claim 3: MP 120,000-180,000 Da
- Claim 4: MP 130,000-180,000 Da
- Claim 5: MP 130,000-160,000 Da
Scope effect: Even if half-life and oligomer MW requirements are met, MP outside these windows can avoid dependent-claim coverage (though claim 1 could still capture if MP is not required).
3) Oligosaccharide MW distribution and impurity caps (claims 6-16)
This family drives tight control of the dextran-derived oligomer quality:
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Claim 6:
- Mw 500-3,000 Da
- Mn > 500 Da
- 90 wt% < 3,500 Da
- top 10 wt% fraction Mw < 4,500 Da
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Claim 7:
-
Claim 8:
-
Claim 9:
- top 10 wt% fraction Mw < 3,200 Da
-
Claim 10:
-
Claim 11:
Impurities:
- Claim 13:
- dimer saccharide ≤ 2.9 wt%
- Claim 14:
- dimer saccharide ≤ 2.5 wt%
- Claim 15:
- dimer saccharide ≤ 2.3 wt%
- Claim 16:
- monomer saccharide ≤ 0.5 wt%
Scope effect: These are material-spec claims. The patent protects not just a complex but a manufacturing endpoint (distribution and residual monomer/dimer levels) that may differ from competitors’ starting dextran cut profiles and hydrogenation/processing results.
4) Iron loading (claims 12 and 18-20)
- Claim 12: iron content in compound 10-50 wt%
- Claim 18: composition iron content 1-50% w/v
- Claim 19: 1-20% w/v
- Claim 20: 10% w/v
Scope effect: If infringement analysis depends on product formulation (not merely active ingredient), these claims are important. Claim 1 can still be infringed by a compound regardless of formulation iron concentration, but composition claims are gated.
5) Dosage form: aqueous liquid composition (claim 21)
- Claim 21: aqueous liquid with compound dissolved or dispersed
How do the half-life “tier” claims expand the protection boundary?
Claims 24-26 add a ladder of durability thresholds:
- Claim 24 (dependent on claim 1): in vitro half-life recited as:
- ≥ 20.9 hours OR
- ≥ 21.6 hours OR
- ≥ 21.7 hours OR
- ≥ 22.5 hours OR
- ≥ 25.5 hours
- Claim 25: same tiering recited for claim 22 compound category
- Claim 26: same tiering recited for claim 23 category
Scope effect: These “or” half-life bands are meaningful for validity and enforcement. If an accused product sits around 18.3-20.8 hours, it may clear a durability-tier dependent claim while still falling inside the base 18.3+ independent claim.
What is the effective claim “matrix” (variables you must satisfy to infringe)?
Below is the practical infringement matrix derived from the claims you provided.
Core compound definition (Claim 1 baseline)
| Variable |
Required scope in Claim 1 |
| Component A |
Hydrogenated oligosaccharide |
| Component B |
Stable association with ferric oxyhydroxide |
| Oligosaccharide origin |
Derived from dextran |
| Oligosaccharide molecular weight |
Mw < 3,000 Da |
| Durability benchmark |
in vitro half-life ≥ 18.3 hours |
Additional dependent gates (by claim family)
| Dependent gate |
Claim numbers |
What it constrains |
| Half-life assay method |
Claim 2 |
acid media, A287.3 nm, definition of t1/2 |
| Complex apparent MW (MP) |
Claims 3-5 |
120k-180k; 130k-180k; 130k-160k |
| Linkage type + oligomer MW + MP |
Claim 22 |
α1,6 linkage; Mw 850-1,150; MP 130k-160k |
| “Explicit” hydrogenated dextran |
Claim 23 |
repeats identity requirement |
| Durability tiers |
Claims 24-26 |
20.9+ up to 25.5+ hours |
| Oligomer distribution |
Claim 6-11 |
Mn, 90/10 fractions, Mw caps and typical ~1,000 Da |
| Low dimer/monomer impurities |
Claims 13-16 |
dimer ≤2.9/2.5/2.3 wt%; monomer ≤0.5 wt% |
| Iron fraction in compound |
Claim 12 |
10-50 wt% |
| Iron concentration in composition |
Claims 18-20 |
1-50% w/v; 1-20% w/v; 10% w/v |
| Aqueous liquid formulation |
Claim 21 |
dissolved or dispersed in water |
Where does the claim structure leave “design-around” room?
Because claim 1 is broad on oligomer identity (still requires dextran-derived hydrogenated oligosaccharide under 3,000 Da) and broad on MP (not required), “design-around” is mainly achievable by breaking one of the core pillars:
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Half-life below 18.3 hours
- Most direct for compound-category avoidance.
- Also vulnerable to assay definition in claim 2 (acid matrices and A287.3 nm endpoint).
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Oligosaccharide MW above 3,000 Da
- Claim 1 cannot cover Mw ≥ 3,000 Da.
- Dependent windows (claim 6 and below) add further boundaries but are not necessary for claim 1 coverage.
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Non-dextran-derived hydrogenated oligosaccharide
- Claim 1 requires “derived from dextran.”
- Claim 23 repeats this identity explicitly.
If those three are intact, the dependent claims still offer potential product-specific exits (MP windows, dimer/monomer caps, iron loading), but those are more likely to affect coverage strength rather than complete claim avoidance where claim 1 is still satisfied.
Patent landscape: what is being protected in the US market segment?
With only the claims text provided, the landscape can be characterized at the technology-issue level rather than naming specific US family members. The patent occupies a recognizable niche:
- Oral or parenteral iron complex chemistry built on:
- ferric oxyhydroxide
- carbohydrate-derived stabilizers
- engineered molecular-weight and impurity profiles of the carbohydrate component
- performance measured by acid hydrolysis durability via A287.3 nm
How this positions relative to adjacent intellectual property themes
US 11,851,504’s claim language points to three likely “clusters” where other patents often exist (without asserting specific case numbers):
- Stable ferric oxyhydroxide-carbohydrate complexes
- Carbohydrate molecular-weight tailoring and hydrogenation processing
- Durability assays and acceptance criteria under acidic hydrolysis
For a business decision, the most actionable takeaway is that this patent’s protected space is not just “iron + carbohydrate.” It is “iron + specific hydrogenated dextran oligomer quality + complex durability under defined acid hydrolysis conditions.”
Claim scope translated to enforcement value
Enforcement leverage
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Half-life threshold (18.3 hours) plus assay method (claim 2) create a measurable gate for both:
- infringement testing of candidate actives
- invalidity analyses that may attack the evidence linking specific MW/distribution to durability
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Impurity caps (monomer/dimer) can be powerful because they tie infringement to spec-sheet quality attributes, not just bulk MW.
Licensing leverage
- The tiered half-life bands (20.9+ to 25.5+) can support:
- differentiated licensing for “ultra-stable” products
- settlement frameworks where a competitor meets or misses certain durability thresholds
Key Takeaways
- US 11,851,504 protects hydrogenated dextran-derived oligosaccharides (MW < 3,000 Da) stably associated with ferric oxyhydroxide, with in vitro Fe3+ hydrolysis half-life ≥ 18.3 hours as the central performance requirement.
- Claim 2 locks in the hydrolysis half-life assay: 0.24 M HCl and 0.9% NaCl acidic solution, monitored by A287.3 nm and half-absorbance time definition.
- Dependent claims materially narrow the protected space via MP windows (120k-180k; 130k-160k), MW distribution limits, low monomer/dimer impurity ceilings, and iron loading.
- The design-around surface is primarily through: (i) lowering half-life below 18.3 hours, (ii) using hydrogenated dextran oligomers outside <3,000 Da, or (iii) using a carbohydrate stabilizer that is not dextran-derived.
- The landscape protection is focused on a stable ferric oxyhydroxide-carbohydrate durability platform where carbohydrate quality attributes and acid hydrolysis durability metrics define patent coverage.
FAQs
1) Does claim 1 require a specific apparent molecular weight (MP) for the iron complex?
No. Claim 1 does not require MP. MP limits are introduced in dependent claims (claims 3-5 and claim 22).
2) What test defines the “in vitro half-life” for the complex?
Claim 2 specifies hydrolysis of Fe3+ in 0.24 M HCl and 0.9% NaCl acidic solution, measured by optical absorbance at 287.3 nm, with half-life defined as the time when absorbance is half of the value at t = 0.
3) Is the dextran origin requirement only in claim 1 or also in later claims?
Both. Claim 1 requires the hydrogenated oligosaccharide is derived from dextran, and claim 23 repeats that requirement by explicitly calling it a hydrogenated dextran oligosaccharide.
4) Which dependent claims add impurity limits that can matter for infringement analysis?
Claims 13-16 cap dimer saccharide (≤2.9%, ≤2.5%, ≤2.3% by weight) and cap monomer saccharide (≤0.5% by weight).
5) Can a competitor avoid dependent-claim coverage while still risking claim 1 exposure?
Yes. Dependent claims add MP, linkage, impurity, and iron loading gates. A product can miss those while still potentially satisfying claim 1’s core criteria (dextran-derived hydrogenated oligosaccharide with Mw <3,000 Da and half-life ≥18.3 hours).
References
[1] US Patent 11,851,504 (claims as provided by user).
