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Patent landscape, scope, and claims: |
United States Patent 6,509,013: Scope, Claim Architecture, and US Patent Landscape
US Drug Patent 6,509,013 is directed to pharmaceutical compositions that combine (i) a pharmaceutically acceptable carrier with (ii) at least one water-insoluble, crosslinked polymer whose repeat units are defined by a general structural formula (and copolymers with a second repeat unit), where substituents (R or R1/R2/R3) include a broad set of alkyl, aryl, amino, quaternary ammonium, and functional groups, and where (iii) the polymer can be crosslinked using specified crosslinkers, including epichlorohydrin and multiple bifunctional or reactive agents. The claims also specify crosslinker loading ranges and include ionic features through exchangeable anions (X−).
The claim set is not limited to a single drug or active ingredient other than the polymer itself. Instead, it broadly covers a polymeric excipient-like system designed to be water-insoluble, crosslinked, and capable of holding exchangeable counterions.
What does the patent claim cover at a compositional level?
Core composition elements
Across independent and dependent claims, the composition has the same three-part structure:
-
Carrier
- A “pharmaceutically acceptable carrier or diluent” (e.g., claim 30).
-
Polymer phase
- “At least one water insoluble, crosslinked polymer” (claims 1, 9, 31, 35, 38).
- Polymer is defined by repeat unit(s) represented by formula(s) (text provided shows placeholders for structural formulas).
-
Crosslinking
- Polymer is crosslinked with a specified “crosslinking agent” (claims 2-4, 6-8, 10-12, 14-16, 19-21, 23-25, 26-29, 32-34, 37).
Polymer repeat unit scope (R and copolymers)
The claim language spans:
- Homopolymer/copolymer repeat unit variants: “a repeat unit having the formula or a copolymer thereof” (claims 1, 9, 31).
- Substituent classes for R (claim 1):
- H or an alkyl/alkylamino/aryl group
- optionally substituted with a broad functional set:
- quaternary ammonium
- primary/secondary alkyl amine
- primary/secondary aryl amine
- hydroxy, alkoxy
- carboxamide, sulfonamide
- halogen
- alkyl, aryl
- hydrazine, guanidine, urea
- carboxylic acid ester group
- or combinations.
Ionic features: exchangeable anions
Several claims explicitly include:
- “each X− is an exchangeable negatively charged counterion” (claims 5, 13, 17, 26, 31).
This clause ties the polymer architecture to ion-exchange behavior rather than purely neutral hydrophobic polymers.
How broad are the crosslinking-agent limitations?
Crosslinkers are enumerated
The patent enumerates a crosslinker set repeatedly (e.g., claims 3, 7, 11, 15, 20, 24, 28, 33):
- Epichlorohydrin
- Diglycidyl ethers:
- 1,4-butanedioldiglycidyl ether
- 1,2-ethanedioldiglycidyl ether
- Halogenated alkanes:
- 1,3-dichloropropane
- 1,2-dichloroethane
- 1,3-dibromopropane
- 1,2-dibromoethane
- Acid chloride / diesters / anhydrides:
- succinyl dichloride
- dimethylsuccinate
- pyromellitic dianhydride
- Isocyanate / acid chloride:
- toluene diisocyanate
- acryloyl chloride
Crosslinker loading ranges
Claims impose weight-percentage ranges for the crosslinker “present in said composition” (terminology suggests the crosslinker is included as a component during polymer formation or in the composition):
- Broad window: 0.5% to 75% by weight
- claims 2, 6, 10, 19, 23, 32, 33 (via dependent structure), 27/31 variants.
- Narrower preferred window: 2% to 20% by weight
- claims 4, 8, 12, 16, 21, 25, 34, etc.
- A different dependent set uses 1% to 75%:
- claim 14 (note it is not the same as claim 2’s 0.5% lower bound).
Functional interpretation for freedom-to-operate
Because crosslinker identity is enumerated, a design that uses a different crosslinking chemistry could avoid literal inclusion. However, because many common crosslinkers (epichlorohydrin, diglycidyl ethers, dichlorides, succinyl dichloride, isocyanates, anhydrides, acryloyl chloride) appear, the practical risk is high if competitors use these conventional crosslinking agents on similar amine-containing water-insoluble polymer backbones.
What is the claim architecture and how does it ladder from broad to specific?
Independent claims
From the provided claim set, independent claims include:
- Claim 1 (composition consisting essentially of carrier + polymer characterized by the repeat unit formula and R substituent scope)
- Claim 9 (pharmaceutical composition including carrier + polymer defined similarly)
- Claim 17 (composition where both R1 and R2 plus ionic counterion X− are explicitly included)
- Claim 22 (composition with R groups limited to alkyl with C1-C20 constraint plus functional options)
- Claim 26 (composition where R1/R2/R3 are independently defined with alkyl C1-C20, aminoalkyl, or aryl with C1-C12 constraint)
- Claim 30 (composition with “hydrophilic, water insoluble, cross-linked aliphatic amine polymer” + pharmaceutically acceptable carrier)
- Claim 31 (composition “consisting essentially of” carrier + crosslinked water-insoluble polymer with repeat unit formula, R options, and X− exchangeable anion)
- Claim 35 (composition consisting essentially of carrier + “crosslinked, water insoluble, polyallylamine polymer”)
- Claim 38 (composition with crosslinked water insoluble polyallylamine homopolymer and repeat unit structural formula with n integer)
Dependent claim patterns
The dependent claims consistently do three things:
- Add crosslinker type (claims 3, 7, 11, 15, 20, 24, 28, 33).
- Add crosslinker loading range (claims 4, 8, 12, 16, 21, 25, 34).
- Add copolymer specifics / explicit ionic exchange (claims 5, 13, 17, 26).
This structure increases the chance that many commercial formulations will fall into one of the enumerated downstream claim variations, even if they miss the broad “R can be anything with these optional substitutions” interpretation.
Where does the patent narrow into polyallylamine-specific coverage?
Polyallylamine track
Claims 35 through 38 create a separate narrower lane:
- Claim 35: “consisting essentially of a carrier and a crosslinked, water insoluble, polyallylamine polymer.”
- Claim 36: polyallylamine can be a homopolymer.
- Claim 37: polymer is crosslinked with epichlorohydrin.
- Claim 38: crosslinked, water insoluble polyallylamine homopolymer with repeat units represented by a structural formula (n integer).
This track is less abstract than the R-substituted generic repeat unit track. For enforcement, it supports straightforward claim construction tied to polyallylamine and epichlorohydrin crosslinking.
What is the likely polymer class in plain terms?
Although structural formulas are not rendered in the text provided, the repeated presence of:
- amine and quaternary ammonium substituents
- exchangeable negative counterions (X−)
- water insoluble but hydrophilic crosslinked network language (claim 30)
- polyallylamine homopolymer variant (claims 35-38)
indicates the patent covers crosslinked, insoluble amine-containing polymer networks that can participate in ionic exchange. The crosslinkers listed are conventional for creating water-insoluble networks from amine-containing monomers/polymers.
How does claim “consisting essentially of” affect scope?
Multiple claims use “consisting essentially of,” including:
- claim 1
- claim 31
- claim 35
In practical patent-landscape terms, this drafting generally:
- permits additional components that do not materially change basic and novel characteristics
- restricts inclusion of additional active ingredients or alternative polymer systems if they materially depart from the defined polymer-carrier composition concept.
Because the independent “consisting essentially of” claims already require a carrier and the specific polymer system, competitors who add other polymer types or substitute polymer structures may still face literal exposure if the added elements do not materially change the claimed composition’s basic characteristics. Conversely, formulation strategies that replace the polymer chemistry or eliminate exchangeable counterion functionality reduce risk.
Where does the overlap between generic claims and polyallylamine claims matter?
There is a high-likelihood overlap because:
- polyallylamine is an amine-containing polymer
- claim 35-38 define a subset within the amine-polymer scope described generically in claims 1/9/17/31.
As a result, even if a competitor argues they fall outside the generic structural formula language, the polyallylamine lane can still capture epichlorohydrin-crosslinked polyallylamine systems.
US patent landscape: what this claim set implies for freedom-to-operate
1) Likely crowded technical area
The combination of:
- crosslinked water-insoluble amine polymers
- ion-exchange via exchangeable anions
- epichlorohydrin and related crosslinkers
is a classic polymer formulation space. The patent’s breadth suggests it sits within a field where many earlier and later filings likely exist covering:
- crosslinked polyamines
- ion-exchange resins and formulations
- pharmaceutical use of crosslinked polyamine polymers
2) Direct exposure is highest when three conditions align
For a product to sit close to literal risk under 6,509,013:
- it uses a carrier + water-insoluble crosslinked amine polymer (or polyallylamine homopolymer)
- it is crosslinked with one of the enumerated agents
- it contains amine functionality and exchangeable anions (where claims include X−), or fits the generic amine substituent scaffolding
3) Exposure decreases when polymer chemistry is redesigned
Risk drops when:
- the crosslinker chemistry is not in the enumerated list
- the polymer is water soluble, not water insoluble
- the polymer backbone is not an amine-containing scaffold or lacks exchangeable anion features
- polyallylamine is replaced by a non-polyallylamine architecture, and the generic repeat unit formula is also avoided
4) Claim durability
The claim set’s repetitive use of:
- explicit crosslinker lists
- numeric crosslinker weight ranges
- multiple layers of R substituent breadth
creates multiple “entry points” for enforcement. This structure often increases the chance that an accused product will meet at least one dependent-claim combination (for example, epichlorohydrin crosslinking within 2-20% weight).
Infringement mapping: which claim elements are the hardest to design around?
Most design-critical elements
- Crosslinker identity
- Epichlorohydrin and several common crosslinkers are in the enumerated set.
- Water insolubility + crosslinked network
- If the polymer is soluble or not crosslinked in a qualifying way, the claims are harder to satisfy.
- Repeat unit / amine substitution framework
- R options are broad, but the polymer must match the structural formula framework.
- Exchangeable anions
- When X− is explicitly claimed, polymer must hold exchangeable negatively charged counterions.
Lower design-critical elements
- R substitution variation
- Claims allow many functional substituents.
- C1-C20 / aryl constraints in certain claims
- These appear in dependent-independent variants (claims 22, 26), so they narrow scope only for those claim paths.
Key Takeaways
- US 6,509,013 is a broad polymer-composition patent built around carrier + water-insoluble, crosslinked amine-containing polymers with exchangeable anions.
- Crosslinker coverage is enumerated and commercially common (epichlorohydrin, diglycidyl ethers, dichloro/dibromo alkanes, succinyl dichloride, dimethylsuccinate, toluene diisocyanate, acryloyl chloride, pyromellitic dianhydride).
- Crosslinker loading ranges are explicit (notably 0.5% to 75% and 2% to 20%, plus a variant 1% to 75%).
- There is a dedicated polyallylamine lane that includes epichlorohydrin crosslinking (claims 35-38), increasing the enforcement likelihood against polyamine resin-style compositions.
FAQs
1) Does US 6,509,013 require a specific drug active ingredient?
No. The claims define a polymer-carrier composition; the polymer chemistry and crosslinking define the claimed subject matter.
2) Which crosslinker is explicitly called out in the polyallylamine-specific claims?
Epichlorohydrin (claim 37).
3) What crosslinker weight ranges are used most often?
The most recurring ranges are 0.5% to 75% by weight and 2% to 20% by weight.
4) How does the patent handle ion-exchange capability?
Several claims require exchangeable negatively charged counterions (X−).
5) Are polyallylamine compositions included even if they differ from the generic repeat-unit formula?
Yes. The polyallylamine-specific independent claims (claims 35 and 38) provide a separate coverage track tied to polyallylamine homopolymers and crosslinked structures.
References
[1] United States Patent No. 6,509,013. Claims provided in the prompt.
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