United States Patent 5,439,686: Scope, Claim Coverage, and US Landscape
What does US 5,439,686 claim, in scope terms?
US 5,439,686 claims a nano-scale, disulfide-crosslinked polymer shell that contains a water-insoluble pharmacologically active agent and is suspended in an aqueous biocompatible liquid for in vivo delivery.
Core claim architecture (Claim 1 is the anchor):
- Payload: “substantially water insoluble pharmacologically active agent,”
- Containment: agent is “substantially completely contained within a polymeric shell,”
- Particle size constraint: largest cross-sectional dimension of shell ≤ ~10 microns,
- Shell chemistry: shell is a “biocompatible polymer” crosslinked by disulfide bonds,
- Formulation vehicle: polymer shell containing agent is suspended in biocompatible aqueous liquid,
- Use context: designed for in vivo delivery.
Dependent claim map (claims 2-16) narrows the payload class, dispersing medium, polymer identity, and processing method. Claim 17 covers a method using Claim 1 compositions.
Claim 1: What exact technical elements define infringement risk?
Claim 1 is the principal coverage and requires all limitations to be met.
Claim 1 limitations (all must be present)
- “A composition for in vivo delivery”
- Payload: “substantially water insoluble pharmacologically active agent”
- Containment: payload is solid or liquid and substantially completely contained within a polymeric shell
- Shell size: “largest cross-sectional dimension of said shell is no greater than about 10 microns”
- Shell polymer: “biocompatible polymer”
- Crosslinking method/chemistry: polymer is “substantially crosslinked by way of disulfide bonds”
- Aqueous suspension: the shell containing agent is suspended in a biocompatible aqueous liquid
Practical interpretation for product design
- The claim is broad on payload identity (it is “pharmacologically active” and insoluble), and broad on agent form (solid or liquid).
- The claim is tight on structural formulation:
- polymer-shell containment,
- disulfide-crosslinked shell,
- aqueous suspension,
- and shell size capped at about 10 microns.
Key business point: If a competitor’s platform uses a crosslinked polymer shell in aqueous suspension, but the crosslinking is not disulfide-based, or the shell is not actually crosslinked by disulfide bonds, they fall outside Claim 1’s defining chemistry.
How do dependent claims expand or narrow coverage? (Claims 2-16)
Claim 2: Payload class
Claim 2 specifies categories:
- pharmaceutically active agent
- diagnostic agent
- nutritional value agent
This makes Claim 2 an allowable taxonomy of what the “pharmacologically active agent” can be.
Claim 3: Example pharmaceutically active agents (broad but named list)
Claim 3 includes a long list such as:
- taxanes: taxol, taxotere
- camptothecins: campothecin
- analgesics/NSAIDs: aspirin, ibuprofen, piroxicam
- gastric/H2 antagonist: cimetidine
- water-insoluble steroids: “substantially water insoluble steroids”
- cytotoxics/anthracyclines and others: doxorubicin, daunorubicin, mitotane, ellipticine, diazepam
- volatile anesthetic examples: methoxyfluorane, isofluorane, enfluorane, halothane
- local anesthetic: benzocaine
- muscle relaxant: dantrolene
- “barbiturates”
- chemotherapy classes and others: “halonitrosoureas,” “anthrocylines,” “visadine,” “phenesterine,” “duanorubicin,” “enfluorane,” etc.
Business impact: this claim lists many drug exemplars but does not restrict to them; it supports broad interpretation that many hydrophobic drugs are contemplated payloads.
Claim 4: Diagnostic agents
- ultrasound contrast agents
- radiocontrast agents
- magnetic contrast agents
This extends claim logic to diagnostic payloads, not only therapeutics.
Claim 5: Nutritional payload
- amino acids, sugars, proteins, carbohydrates, fat-soluble vitamins, fat, or combinations
This is unusual in “drug patent” framing but increases the payload universe without changing the shell definition.
Claims 6-10: What do they say about dispersing media and dilution?
Claims 6-10 focus on the internal state of the payload within the shell and whether dilution occurs.
Claim 6: Payload dissolved in a biocompatible dispersing agent
If the agent is dissolved, the claim requires a biocompatible dispersing agent.
Claim 7: Dispersing agent species list (very broad)
Examples include:
- natural oils: soybean oil, coconut oil, olive oil, safflower oil, cotton seed oil
- hydrocarbons: “aliphatic, cycloaliphatic or aromatic hydrocarbons having 4-30 carbon atoms”
- alcohols: “2-30 carbon atoms”
- esters: “2-30 carbon atoms”
- ethers: “2-30 carbon atoms”
- halogenated hydrocarbons: “1-30 carbon atoms” (optionally multiple halogens)
- ketones: “3-30 carbon atoms”
- polyalkylene glycol
- or combinations
This is a broad “hydrophobic solvent/dispersant” universe.
Claim 8: Payload suspended in a biocompatible dispersing agent
If the agent is suspended rather than dissolved, Claim 8 applies.
Claim 9: Dispersing agent list repeats breadth
Same universe as Claim 7.
Claim 10: “not diluted”
This adds another formulation nuance: agent within the shell is not diluted (as a limitation of Claim 10 only).
Business impact: Claim 1 already covers payload contained in disulfide-crosslinked shell suspended in aqueous liquid. Claims 6-10 create additional dependent pathways that protect formulations where the hydrophobic agent is dissolved or suspended in specific hydrophobic/dispersing agents, and in “not diluted” configurations.
Claims 11-13: What polymers qualify?
Claim 11: Crosslinked polymer includes covalently attached sulfhydryl groups or disulfide linkages (pre-crosslinking functionality)
- polymer may be naturally occurring or synthetic
- prior to crosslinking it has covalently attached sulfhydryl groups or disulfide linkages
This implies the crosslinking is formed from thiol chemistry (leading to disulfide crosslinks) or retains disulfide units.
Claim 12: Naturally occurring polymers
- proteins
- lipids
- polynucleic acids
- polysaccharides
Claim 13: Synthetic polymers with thiol/disulfide functionality
Includes synthetic polyamino acids containing cysteine/disulfide groups and multiple polymer families modified to carry free sulfhydryl groups and/or disulfide groups, including:
- polyvinyl alcohol modified to contain thiols/disulfides
- polyhydroxyethyl methacrylate modified with thiols/disulfides
- polyacrylic acid modified with thiols/disulfides
- polyethyloxazoline modified with thiols/disulfides
- polyacrylamide modified with thiols/disulfides
- polyvinyl pyrrolidinone modified with thiols/disulfides
- polyalkylene glycols modified with thiols/disulfides
Business impact: this is broad enough to cover many thiol-functionalized polymer shells used for “redox-responsive” or thiol-reactive networks, if the crosslinking results in disulfide-bonded shell structures.
Claims 14-16: Processing and specific embodiments
Claim 14: disulfide bonds formed by sonication
This is a process-specific dependent limitation. If a product makes disulfide crosslinks via sonication, it better fits this dependent claim.
Claim 15: shell polymer is albumin
If the disulfide-crosslinked polymer shell is albumin, Claim 15 is directly implicated.
Claim 16: aqueous suspension medium
- water
- buffered aqueous media
- saline, buffered saline
- solutions of amino acids/sugars/vitamins/carbohydrates
- combinations
This is consistent with conventional injectable vehicle constraints.
Claim 17: Method claim
Claim 17 is straightforward:
- “administering to said subject an effective amount of composition according to claim 1.”
Business impact: If Claim 1 is infringed by a formulation, Claim 17 can be asserted against therapeutic uses and clinical administration.
How broad is the patent’s “claim scope envelope” in US practice?
Primary infringement hinge: disulfide-crosslinked polymer shell
The single most decisive technical requirement is:
- shell is “substantially crosslinked by way of disulfide bonds.”
That requirement separates this patent from formulations built on:
- amide crosslinks,
- ester crosslinks,
- carbamate networks,
- ionic crosslinks (without disulfide),
- disulfide-free hydrogels,
- or polymeric micelles/aggregates without a crosslinked shell architecture.
Secondary hinge: “substantially completely contained” within the shell
If a formulation provides encapsulation but the payload is not “substantially completely contained” (for example, large fractions distributed freely in the aqueous phase), infringement becomes less clear relative to Claim 1’s containment language.
Tertiary hinge: shell size cap (≤ about 10 microns)
- The claim does not demand nanometer scale; it allows up to about 10 microns.
- A competitor producing larger microparticles may avoid the size limitation if “largest cross-sectional dimension” exceeds the cap.
Vehicle is aqueous suspension
This targets injectable-style suspensions rather than solid implants or lyophilized solids (though an aqueous suspension at the point of administration would still be within the claim logic).
Patent landscape: competitive positioning against US 5,439,686
Where this patent likely sits in the technology map
The claim language aligns with a class of technologies that:
- use thiol/disulfide chemistry to stabilize polymeric carriers,
- form disulfide-crosslinked albumin or thiol-functional polymer shells,
- and encapsulate hydrophobic drugs in an aqueous injectable.
This places the patent in an area that overlaps with:
- albumin-based nanoparticle or microparticle drug delivery,
- thiolated polymer crosslinking via disulfide formation,
- redox or glutathione-responsive disulfide linkers for intracellular release,
- and solvent-in-water suspension systems for hydrophobic payloads.
What this means for freedom-to-operate (FTO) design
A design that attempts to avoid the patent typically needs to break at least one of these claim-defining elements:
- Use a non-disulfide crosslinking mechanism for the shell network.
- Avoid a polymeric shell that is “substantially completely” containing the agent.
- Use shell dimensions exceeding the “about 10 microns” maximum (if scale-up is feasible).
- Avoid making disulfide crosslinks by sonication if targeting Claim 14 explicitly (but note Claim 1 still remains unless disulfide chemistry is eliminated).
- Avoid albumin-shell embodiment if matching Claim 15 specifically (but again Claim 1 remains unless disulfide crosslinking is removed).
How to interpret “landscape” risk
Because Claim 1 is formulation-centric and chemistry-centric, the landscape risk is usually highest when a competitor product:
- uses thiol-functional polymers that are crosslinked into disulfide-bond networks,
- forms carriers with a defined shell containing hydrophobic drug payload,
- and disperses those carriers in aqueous injectable vehicles.
Lower risk arises if competitors use:
- liposomes or micelles without disulfide-crosslinked shell structure,
- covalently crosslinked shells without disulfide,
- or physical adsorption without a disulfide crosslinked polymer network.
Key takeaways
What matters most for infringement and competitive strategy
- Claim 1 is the deal-maker: a biocompatible polymer shell crosslinked by disulfide bonds that substantially completely contains a substantially water-insoluble agent and is suspended in aqueous liquid.
- Size is capped: shell largest cross-sectional dimension is ≤ about 10 microns.
- Payload breadth is wide: pharmaceutics, diagnostics, and nutritional agents are all covered, with many specific drug examples listed in Claim 3.
- Dependent claims add protection paths for hydrophobic solvent/dispersant-containing shells, thiol/disulfide-functional polymer classes, sonication-made disulfides, and albumin shells.
- Landscape risk concentrates around disulfide-crosslinked polymer shell carrier systems; risk drops when the shell network is formed without disulfide crosslinks or when containment/size requirements are not met.
FAQs
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Is US 5,439,686 limited to nanocarriers?
No. Claim 1 allows shell largest cross-sectional dimension up to about 10 microns.
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Does the patent require a specific payload drug?
No. It covers “substantially water insoluble pharmacologically active agents,” with Claim 3 providing non-exclusive example drug categories.
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What is the most important chemistry limitation?
The polymeric shell must be substantially crosslinked by disulfide bonds.
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Does Claim 1 require the payload to be dissolved or suspended inside the shell?
Claim 1 covers payload as “solid or liquid” and contained in the shell. Claims 6-10 further narrow dissolved vs suspended configurations and dispersing agents.
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Is there a method claim tied to administration?
Yes. Claim 17 is a delivery method claim based on administering an effective amount of the Claim 1 composition.
References (APA)
[1] US Patent 5,439,686. (n.d.). Composition and method for in vivo delivery of substantially water insoluble pharmacologically active agents using disulfide crosslinked polymeric shells.
