United States Patent 5,292,515: Scope, Claims Architecture, and US Patent Landscape
US Drug Patent 5,292,515 centers on a centrifugally cast, uniform-wall-thickness, hydrophilic, water-swellable, water-insoluble, non-biodegradable polymer cartridge that functions as a rate-limiting barrier for sustained drug release. It also claims the sealing plug process where the plug’s equilibrium water content exceeds the cartridge’s, plus implantation-by-perforation delivery device and kit structures.
What is actually claimed: method steps + article + device + implantation system
The patent claim set builds in layers:
1) Cartridge manufacturing method (Claims 1-7)
2) Drug delivery device and plug-seal method (Claims 8-20)
3) Cartridge article (Claim 21-25)
4) Delivery device apparatus (Claim 26-35)
5) Implantation method (Claims 36-40)
6) Implantation kit (Claims 41-42)
This structure matters because infringement risk is not only on the polymer chemistry and centrifugation step; it also includes shape constraints, surface smoothness, thickness uniformity, and plug equilibrium water content relation.
1) What does Claim 1 protect in the cartridge-manufacturing method?
Core process elements (Claim 1)
Claim 1 is a process claim requiring all of the following:
- Centrifugally casting a tube that contains a predetermined quantity of at least one
polymerizable hydrophilic liquid monomer, plus closure means to prevent monomer loss.
- Maintaining the tube axis parallel to ground during rotation.
- Rotating at a speed sufficient to cause radially outward displacement such that the monomer forms a
cylindrically-shaped liquid cartridge of predetermined configuration inside the tube.
- Applying polymerization conditions to convert the liquid cartridge into a solid hollow plastic cartridge with predetermined configuration.
- Recovering a cartridge with a specific material property profile:
- biocompatible
- non-biodegradable
- water-swellable
- water-insoluble
- hydrophilic
- uniform wall thickness
- smooth external and internal cylindrical surfaces
Key claim sensitivities
- The monomer is hydrophilic and polymerizable and is used as a liquid prior to polymerization.
- The “rate-limiting barrier” role is tied to the cartridge’s structure and properties, not to a membrane coating applied after casting.
- “Uniform wall thickness” and smooth internal/external surfaces are explicit in Claim 1’s recovered cartridge description.
Practical consequence
If a competitor uses a different geometry formation step (e.g., extrusion, molding, dip-coating) or cannot map their process to the centrifugation + radially outward displacement + recovered uniform-wall cartridge, Claim 1 becomes hard to land.
2) How tightly do dependent claims narrow the monomer chemistry and polymerization?
Monomer class and catalytic system (Claims 2-4)
- Claim 2: monomers are hydrophilic ethylenically unsaturated monomers plus an agent to effect catalysis.
- Claim 3: polymerization done in the presence of radiation and a radiation catalyst.
- Claim 4: polymerizable monomer contains benzoin methyl ether as an initiator; radiation is ultra-violet light.
This chain makes Claims 2-4 narrower than Claim 1:
- Claim 1 is broad on “at least one polymerizable hydrophilic liquid monomer.”
- Claim 2 requires ethylenic unsaturation and a catalysis agent.
- Claims 3-4 force a radiation/UV photoinitiator system and specify benzoin methyl ether.
Shape modification (Claims 5-6)
- Claim 5: outer portion proximal to closed end is subjected to a shaving step, imparting a smooth oval shape.
- Claim 6: the cartridge is a xerogel.
Hydrogel mapping (Claim 7)
- Claim 7: cartridge is a hydrogel.
Implication for landscape: the patent simultaneously covers:
- xerogel (low-water solid state)
- hydrogel (hydrated state)
- and the transformation path from centrifugally cast xerogel to hydrogel.
3) What does Claim 8 lock down in the drug-device preparation method?
Claim 8 moves from cartridge casting to forming a sealed reservoir drug delivery device by polymerizing a liquid monomer plug into the upper portion of the reservoir.
Claim 8 elements
A method for preparing a delivery device for sustained release comprising:
1) Introduce active agent (optionally with a pharmaceutically acceptable carrier) into a
cylindrically-shaped reservoir of the biocompatible non-biodegradable water-swellable, water-insoluble hydrophilic plastic cartridge, with smooth external and internal surfaces and uniform thickness.
2) Introduce at least one polymerizable liquid monomer into the upper portion to close the open end of the reservoir.
- The monomer’s polymerized-state equilibrium water content exceeds that of the cartridge.
3) Polymerize the monomer to create a plug of water-swellable, water-insoluble polymer sealing the opening, forming a delivery device with predetermined sustained release.
Why the equilibrium water content relation is pivotal
The “sealant plug” is not described purely by chemistry; it is described by a water content gradient condition:
- Plug equilibrium water content > cartridge equilibrium water content.
This provides a material-performance limitation that competitors can potentially target by reversing the relation (plug lower water content than cartridge) or altering seal mechanism.
4) How do Claims 9-20 constrain shape and monomer mixture?
- Claim 9: cartridge has a smooth oval cylindrical shape.
- Claim 10: outer portion distal to plug is shaped to impart smooth oval shape.
- Claim 11-16: active agent is a drug; drug can be macromolecular (MW “upwards to about 25,000”), including:
- native and recombinant proteins
- hormonally active polypeptide
- LHRH polypeptide
- mammalian growth hormone or mammalian growth releasing hormone
- Claims 17-19: cartridge can be xerogel or hydrogel; Claim 19 adds hydrogel at equilibrium water content.
- Claim 20: polymerizable material for the plug can be a homogenous mixture of ethylenically-unsaturated monomer and a water-soluble pore-forming agent.
Scope effect: Claims 9-10 and 17-19 tie device form to xerogel/hydrogel and oval shaping. Claim 20 pushes toward pore formation through water-soluble porogens, affecting water uptake kinetics.
5) What article claims exist, and what do they cover (Claim 21-25)?
Claim 21 is an article claim for the cartridge:
Claim 21 cartridge characteristics
- biocompatible, non-biodegradable, water-swellable, water-insoluble, hydrophilic plastic cartridge
- useful as rate-limiting barrier in a drug delivery device implantable by perforation
- characterized by:
- oval cylindrical shape at its closed end
- smooth unscored internal and external cylindrical surfaces
- uniform thickness between surfaces
Dependent claims narrow state and polymer type
- Claim 22: cartridge is xerogel.
- Claim 23: cartridge is hydrated.
- Claim 24: cartridge is a polymer of 2-hydroxyethyl methacrylate.
- Claim 25: internal cylindrical surface area near open end has been
- scored
- treated with a mono- or polyhydric alcohol to enhance graft polymerization of polymerizable ethylenically unsaturated monomer.
Important tension inside the family
- Claim 21 says smooth unscored surfaces.
- Claim 25 states scoring at a specific internal area near the open end.
This reads as: the scoring in Claim 25 is localized, but it creates a potential interpretive boundary for literal conformity.
6) What does Claim 26 protect in the delivery device apparatus?
Claim 26 is a device apparatus claim with explicit structural and functional features:
Claim 26 device elements
- A biocompatible, non-biodegradable, water-swellable, water-insoluble, hydrophilic plastic cartridge with a cylindrically-shaped reservoir.
- Cartridge has:
- oval outer cylindrical shape at one end
- smooth internal and external cylindrical surfaces
- uniform cylindrical wall thickness
- Sealant means closing the open end:
- plug of biocompatible, non-biodegradable, water-swellable, water-insoluble, hydrophilic polymer
- plug equilibrium water content greater than the cartridge per se
- Active agent contained in reservoir amount sufficient for predetermined sustained release over extended period.
Dependent claim expansions
- Claims 27-28: active agent is drug; macromolecular MW upward to 25,000.
- Claims 29-30: cartridge and sealant plug in xerogel state or hydrogel state.
- Claims 31-34: protein and hormonally active polypeptide including LHRH; GH or GHRH.
- Claim 35: carrier admixed with active agent.
Scope effect: Claim 26 is broad in “sealant means” but narrows by equilibrium water content and by cartridge geometry and surface smoothness.
7) What does the implantation method and kit cover?
Implantation method (Claim 36)
A method for implantation into an animal comprising:
- perforating skin at a site with an instrument comprising:
- a hollow needle
- the delivery device of Claim 26
- injecting delivery device through needle and depositing subcutaneously
- withdrawing needle
Dependent claims (37-40)
- Active agent includes native/recombinant proteins (Claim 37)
- Active agent is LHRH polypeptide (Claim 38)
- Delivery device cartridge is xerogel state (Claim 39) or hydrated state (Claim 40)
Kit claim (Claim 41-42)
Kit for implantation by perforation comprising:
- delivery device of Claim 37
- delivery means to eject
- container means housing delivery device and delivery means in a sterile aqueous medium
Claim 42 adds a delivery mechanism:
- small rigid hollow tube of uniform internal diameter with a needle-like opening at one end
- telescoping solid rigid rod slidably communicating inside the tube
- delivery device positioned in tube near end of rod for slidable ejection
Landscape implication: these claims are tied to specific “implantation by perforation” workflows and mechanical delivery geometry. Competitors may design alternate implantation systems (different instrument interfaces or delivery mechanics) to reduce apparatus infringement.
Claim-by-Claim Scope Map (US 5,292,515)
| Claim No. |
Claim Category |
What it requires (high-level) |
| 1 |
Method |
Centrifugal casting of hydrophilic liquid monomer into uniform-wall hollow cartridge; polymerized solid cartridge; water-swellable, water-insoluble, hydrophilic, non-biodegradable, biocompatible |
| 2 |
Method dep. |
Hydrophilic ethylenically unsaturated monomers + catalysis agent |
| 3 |
Method dep. |
Radiation polymerization + radiation catalyst |
| 4 |
Method dep. |
Benzoin methyl ether initiator; UV light |
| 5 |
Method dep. |
Shaving step to impart smooth oval shape near closed end |
| 6 |
Method dep. |
Cartridge in xerogel state |
| 7 |
Method dep. |
Cartridge in hydrogel state |
| 8 |
Method |
Load drug in cartridge reservoir; polymerize monomer plug to seal; plug equilibrium water content > cartridge equilibrium water content |
| 9-10 |
Method dep. |
Smooth oval shape; shaping distal from plug |
| 11-16 |
Method dep. |
Drug is macromolecular (up to 25,000+ MW); includes native/recombinant proteins; hormonally active polypeptides; LHRH and GH/GHRH examples |
| 17-19 |
Method dep. |
Cartridge xerogel or hydrogel at equilibrium water content |
| 20 |
Method dep. |
Plug monomer mixture with ethylenically unsaturated monomer + water-soluble pore-forming agent |
| 21 |
Article |
Cartridge product: oval cylindrical closed end, smooth unscored internal/external cylindrical surfaces, uniform thickness; implantable by perforation |
| 22-23 |
Article dep. |
Xerogel state; hydrated state |
| 24 |
Article dep. |
Polymer is 2-hydroxyethyl methacrylate |
| 25 |
Article dep. |
Internal surface area near open end is scored and treated with mono/polyhydric alcohol to enhance graft polymerization |
| 26 |
Delivery device |
Cartridge + sealant plug with plug equilibrium water content > cartridge; oval end; smooth surfaces; uniform wall thickness; sustained release |
| 27-28 |
Device dep. |
Drug and macromolecular MW range |
| 29-30 |
Device dep. |
Xerogel or hydrogel state for cartridge and sealant |
| 31-34 |
Device dep. |
Proteins, hormonally active polypeptides; LHRH; GH/GHRH |
| 35 |
Device dep. |
Pharmaceutically acceptable carrier included |
| 36 |
Implantation method |
Perforate skin; use hollow needle instrument carrying device; inject subcutaneously; withdraw needle |
| 37-38 |
Implantation dep. |
Active agent proteins; LHRH |
| 39-40 |
Implantation dep. |
Cartridge xerogel or hydrated state |
| 41-42 |
Kit |
Device + ejection delivery means + sterile aqueous container; mechanical ejection with hollow tube + telescoping rod |
How the patent’s claim language narrows real-world design options
A. Structure and state constraints
The patent repeatedly requires:
- hydrophilic
- water-swellable
- water-insoluble
- non-biodegradable
- uniform wall thickness
- smooth (unscored, at least generically in Claim 21)
- oval geometry at ends (Claims 5, 9-10, 21, 26, 9-10)
A competitor using:
- biodegradable polymers,
- water-soluble polymers,
- non-uniform wall thickness,
- roughened or textured surfaces,
- or non-oval end geometries
faces higher risk against literal claim scope.
B. Sealant performance relation
The plug is constrained by:
- equilibrium water content greater than the cartridge (Claims 8 and 26)
If competitors create a plug with equal or lower equilibrium water content, they can attempt to fall outside that limitation.
C. Polymerization modality constraints in dependent claims
Only Claims 3-4 force UV and benzoin methyl ether. Independent Claim 1 remains broader.
D. Drug payload claims focus on macromolecular proteins
Claims 11-16, 28, 31-34, 37-38 lock onto macromolecular drugs up to 25,000+ MW and specific endocrine peptides/proteins as examples. Generic protein payloads likely map, but literal claim coverage for a specific drug depends on matching these categories.
E. Implantation system claims are instrument-specific
Claims 36 and 41-42 target perforation-based insertion and a delivery structure featuring:
- hollow needle for injection through tissue
- optional mechanical ejection kit components with telescoping rod
US Patent Landscape: likely “hot zones” for freedom-to-operate (FTO)
Because the user provided the claim text but not the assignee or filing data, the landscape below is organized by technical design-around and infringement sensitivity, mapped to claim elements that typically appear across polymer-limiting-barrier drug delivery patents.
1) Hot-zone patents most likely to overlap (by feature)
In a typical sustained-release polymer barrier landscape, overlap clusters around:
- Centrifugally cast or otherwise formed uniform wall hydrophilic gels used as rate-limiting barriers
(overlap risk highest for Claim 1’s process + Claim 21’s article attributes)
- Hydrophilic, water-swellable, water-insoluble, non-biodegradable materials configured into implantable reservoirs
(overlap risk highest for Claim 21/26 property set)
- Multi-part seals where the sealant water content differs from barrier
(overlap risk highest for Claim 8/26 equilibrium water content relation)
- Shape and surface finish requirements (oval ends, smooth internal/external surfaces)
(overlap risk highest for Claim 21/26)
- Implantation by perforation with a hollow needle and kit ejection mechanisms
(overlap risk highest for Claim 36/41-42)
2) Common design-around vectors against this patent
These are the most direct non-infringing pathways relative to claim language:
- Replace centrifugation-based casting with another formation method that avoids the radially outward displacement inside a rotating tube
- Use a barrier polymer that is:
- biodegradable, or
- water-insoluble but not water-swellable, or
- not hydrophilic, or
- has non-uniform thickness
- Alter the sealant so that its equilibrium water content is not higher than the cartridge’s
- Avoid oval-ended geometry or smoothness constraints by using different end geometry and surface profile (if claim construction requires strict “smooth unscored”)
- Use a non-perforation implantation workflow or non-hollow-needle delivery pathway, and avoid the kit’s telescoping-rod ejection architecture
3) Where infringement risk concentrates operationally
If a product development process touches all of the following simultaneously, it tends to concentrate risk:
- barrier manufactured to match Claim 1 and Claim 21 (structure + properties)
- reservoir drug loaded and sealed by polymerizing a monomer plug to satisfy the equilibrium water content relation (Claim 8/26)
- device shaped and finished to satisfy oval and smooth/unscored constraints (Claim 21/26)
- implantation done via perforation with hollow needle or kit ejection mechanism (Claim 36/41-42)
Key Takeaways
- US 5,292,515’s main claim thread ties centrifugally cast uniform-wall hydrophilic hydrogels/xerogels to sustained drug release as a rate-limiting barrier.
- The seal is structurally and materially defined by a water-content gradient: the sealant plug equilibrium water content must exceed the cartridge’s (Claims 8 and 26).
- The patent constrains device geometry to oval ends and requires smooth internal/external cylindrical surfaces with uniform wall thickness (Claims 21 and 26).
- Dependent claims add specific chemistry and initiation (UV + benzoin methyl ether) and allow monomer mixtures with pore-formers (Claim 20).
- The claim set extends beyond polymer and device structure into implantation-by-perforation mechanics (Claim 36) and a defined kit delivery mechanism (Claims 41-42).
FAQs
1) Is US 5,292,515 limited to a specific polymer chemistry?
No. The independent process claim (Claim 1) covers “at least one polymerizable hydrophilic liquid monomer.” A specific polymer is named in Claim 24 as 2-hydroxyethyl methacrylate.
2) What is the most distinctive technical limitation across the device claims?
The sealant plug’s equilibrium water content must be greater than that of the cartridge (Claims 8 and 26).
3) Does the patent require the cartridge to be hydrated?
It covers both xerogel and hydrogel states (Claims 6-7, 17-19, 22-23, 29-30), and dependent claims specify hydrated/equilibrium water content states.
4) Do the claims cover implantation procedures and not only polymer structures?
Yes. Claim 36 covers implantation using a hollow needle and perforation, and Claims 41-42 cover a kit with defined ejection mechanics.
5) Do the claims cover macromolecular drug payloads like proteins?
Yes. Dependent claims identify macromolecular compositions up to about 25,000+ MW, including native and recombinant proteins, and examples like LHRH and growth hormone/GHRH polypeptides.
References (APA)
[1] United States Patent and Trademark Office. (n.d.). US Patent 5,292,515.
