Executive summary US Patent 5,739,176 covers in-situ formation of a solid, biodegradable implant inside the body by dissolving a water-insoluble biodegradable thermoplastic polymer in a biocompatible water-soluble organic solvent (or solvent mixture) that dissipates/diffuses into body fluid, causing the polymer to coagulate/solidify. The patent’s core claim scope is not limited to one polymer, one solvent, or one anatomical use. The estate is broad on polymer chemistry classes, solvent identity, solvent-mixture design, and implant-site functions (adhesion, scaffold, wound/bone/soft tissue/periodontal use). It also contains claims that extend into combination implants with biologically active agents. Key features for freedom-to-operate (FTO) analysis are: (1) whether the competitor uses an organic solvent that diffuses/dissipates into body fluid to trigger precipitation/solidification; (2) whether the polymer falls within the claimed thermoplastic biodegradable classes; and (3) whether the competitor’s formulation uses a two-solvent system where one solvent dissolves the polymer and a second is incapable/less capable so that the polymer solidifies upon solvent exchange.

US Patent 5,739,176: What claims does it cover for in-situ biodegradable implants formed by solvent diffusion/precipitation?

Core independent claim structure (method and composition)

The claims provided indicate a common technical thesis across method and composition:

Formulation step: dissolve a biocompatible, water-insoluble, biodegradable thermoplastic polymer in a biocompatible, water-soluble organic solvent to form a composition.
Delivery/placement: place the composition at an implant site in the body (including injection/needle delivery and application to tissue/wounds).
In situ solidification trigger: allow the organic solvent to dissipate/diffuse into body fluid, while the polymer coagulates/solidifies to create a biodegradable solid implant.
Criticality: proportions of polymer in solvent and polymer molecular weight are “effective” to produce both solvent dissipation/diffusion and coagulation.

Independent claim coverage is supported by:

A method-of-forming claim (your claim 1 / 19) and
A pharmaceutical composition claim (your claim 18 / 33 and dependent coverage).

Thermoplastic polymer classes in the independent scope

Within claim 1/18, the polymer is selected from specific buckets, including:

Copolymers made from biodegradable, water-insoluble monomer/polymer + biodegradable, water-soluble monomer/polymer, with enough water-insoluble fraction to keep the copolymer water-insoluble.
PEG-polylactide/polyglycolide/polycaprolactone (or terpolymers).
Lactide–glycolide or lactide–caprolactone copolymers (or terpolymers).
Lactide + carbonate copolymers.
Polyanhydrides.

In claim 36, the composition claim set expands beyond the limited list to other biodegradable polymer types (polyesters, polycarbonates, polyorthocarbonates, polyphosphazenes, etc.), then claim 37 narrows back to polylactides/polyglycolides/polycaprolactones and copolymers.

Practical claim consequence: competitors using PLA/PLGA/PCL-class biodegradable thermoplastics in solvent-exchange precipitation systems fall squarely inside at least the central independent claim polymer list, and often inside the broader dependent polymer enumerations.

Organic solvent scope and criticality

Claim 2 and 3 list numerous candidate solvents, and claim 6–8 define a solvent-mixture mechanism.

Claim 2 list includes (representative, as given):
N-methyl-2-pyrrolidone (NMP), 2-pyrrolidone, ethanol, propylene glycol, acetone, ethyl acetate, methyl acetate, methyl ethyl ketone, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), caprolactam, decylmethylsulfoxide, oleic acid, 1-dodecylazacycloheptan-2-one, plus mixtures.
Claim 3 narrows to: NMP, 2-pyrrolidone, DMSO, acetone, plus mixture.
Claim 6/7/8 allow a mixture design:
a first solvent dissolving the polymer + a second solvent that is incapable or less capable of dissolving the polymer, at a ratio such that polymer remains soluble pre-placement but coagulates upon solvent dissipation/diffusion after placement. Second solvent examples include water, ethanol, propylene glycol. First solvent examples overlap the longer lists (including NMP, 2-pyrrolidone, acetone, esters, ketones, DMF, DMSO, THF, caprolactam, decylmethylsulfoxide, oleic acid, and the specified cyclic amide/amphiphile).

Practical claim consequence for FTO: the patent is strongest against systems that use:

NMP, DMSO, acetone, DME-like polar solvents, DMF, and similar solvent identities; and
solvent mixtures where water/ethanol/propylene glycol is the nonsolvent (or weaker solvent) that drives precipitation/solidification in vivo.

Implant-site functional use coverage

Claim 9–15 provide explicit implant-site functions:

Adhesion between tissues or implant and tissue (claim 9).
Subdermal injection for tissue build-up (claim 10).
Wound placement to inhibit scar formation (claim 11).
Bone defect/filler (claim 12).
Soft tissue defect scaffold (claim 13).
Cavities including periodontal, oral, vaginal, rectal, nasal (claim 14).
Periodontal pocket treatment for periodontal disease (claim 15).
Eye cul-de-sac (claim 17).

Practical claim consequence: even if a competitor targets a specific indication, the independent claim is not indication-limited. Dependent claims show breadth of intended anatomical placement and can create additional coverage hooks for enforcement.

Needle delivery and administration form

Claim 5: delivering the composition in-situ through a needle.

This matters because some competitors attempt to design around by using alternate administration devices (sprays, patches, preformed depots). Needle delivery is explicitly within scope.

What polymers and solvent systems trigger infringement risk under 5,739,176?

Risk-critical formulation mechanism: solvent exchange causes coagulation

The claims consistently require:

polymer is water-insoluble yet dissolved in an organic solvent that dissipates/diffuses into body fluid; and
polymer then coagulates/solidifies in situ.

This is the main mechanism competitors must route around. If a competitor uses:

a solvent that does not appreciably dissipate/diffuse into body fluid in the claimed sense, or
polymer solidification driven by a different trigger (e.g., ionotropic gelation, crosslinking chemistry, thermal setting in vivo, photopolymerization, enzymatic crosslinking), then the claim basis weakens. If the competitor still relies on solvent diffusion/precipitation, risk increases.

Polymer “home territory”

Claim 1’s polymer list centers on:

PLA/PLGA/PCL-type biodegradable thermoplastic copolymers (including PEG-block/PEG-containing copolymers),
lactide-based copolymers including lactide-carbonate,
polyanhydrides.

These polymers dominate many in-situ forming depots and solvent-exchange systems.

Solvent identity hotspots

From claim 2 and 3, infringement risk increases for formulations using:

NMP
2-pyrrolidone
DMSO
acetone
and, through the broader list, DMF, THF, acetone/esters/ketones, and polar amides/lactams.

From the solvent-mixture dependent claims (6–8), additional risk increases when the mixture uses:

first solvent: NMP/2-pyrrolidone/acetone/DMSO/DMF/THF-type,
second solvent: water/ethanol/propylene glycol.

How do the dependent claims expand scope to biologically active agent combination products?

Agent loading and release mechanisms

Claim 4 adds that an effective amount of a biologically active agent can be combined with the polymer/solvent system so that the implant releases the agent by:

diffusion, erosion, or a combination during biodegradation.

Agent breadth

Claims 16 and 29–33 provide very broad agent categories:

anti-inflammatory, antimicrobial, antibiotic, etc. (claim 16),
an extremely expansive list in claim 29,
then narrowing by agent type:
- protein/peptide drug (claim 30, 40),
- antigen/vaccine (claim 31, 41),
- uncharged molecule or activated form (claim 32, 42),
- specific example: tetracycline (claim 43).

Practical claim consequence: even if the competitor’s polymer/solvent system is strong design-around territory, adding drug payload may still keep them inside the combination claims, depending on the exact agent and how “released by diffusion/erosion” is characterized.

What does claim 6’s “two-solvent mixture” language mean for design-arounds?

Mechanistic limitation

Claim 6 requires:

a first solvent dissolving the thermoplastic polymer,
a second solvent that is incapable or less capable than the first solvent of dissolving the polymer,
at a ratio where polymer is still soluble pre-placement,
then coagulates/solidifies when placed and the first solvent dissipates/diffuses into body fluid.

Claim 19 parallel language provides essentially the same concept with a slightly different ordering.

Design-around strategy implicit in the claim

Systems that solidify without relying on solvent quality contrast (good vs poor solvent during placement) may avoid this limitation. But if the competitor uses a solvent mixture to achieve in situ precipitation, this claim becomes a direct fit.

How long is the exclusivity window for US 5,739,176 and when would generic risk start?

No expiration or exclusivity timing analysis can be completed from the information provided because the filing date, priority date, maintenance status, and prosecution/publication timeline are not included.

What is the Orange Book status of 5,739,176?

No Orange Book status can be determined from the provided information.

What patent landscape surrounds 5,739,176 (related patents, continuation families, and overlapping claim themes)?

A surrounding landscape cannot be produced accurately from the provided inputs because the patent family members, application/priority identifiers, assignee history, and citation network are not supplied.

Which companies are likely using similar solvent-exchange biodegradable implant technologies and what are the FTO implications?

No company mapping can be produced reliably from the provided information alone.

How strong is the patent estate for enforcement based on the given claim set?

Strength indicators

Broad independent mechanism (solvent diffusion into body fluid causing polymer coagulation/solidification).
Broad polymer classes including PLA/PLGA/PCL-type thermoplastics and polyanhydrides.
Broad solvent identity lists explicitly naming multiple common solvent systems.
Broad anatomical applicability and delivery mode (needle).
Broad payload enablement for biologically active agents.

Strength limits embedded in the claim language

The polymer must be biodegradable and water-insoluble but dissolved in the defined solvent prior to placement.
The solvent must be capable of dissipating or diffusing into body fluid upon placement, implying an in vivo solvent exchange/precipitation mechanism.
The claim ties coagulation/solidification to polymer molecular weight and polymer/solvent proportion being effective. This creates a factual/technical infringement burden for competitors that significantly alter concentration or molecular weight distributions.

Feature chart: claim coverage vs common in-situ implant technologies

Technology approach	Matches 5,739,176’s “solvent diffusion triggers coagulation” theme?	Likely fit vs claims provided
PLA/PLGA dissolved in NMP (or DMSO/acetone) then injected; solvent exchanges into tissue fluid causing polymer precipitation	Yes	High risk (claims 1/18 + solvent lists; claims 2–3, 6–8)
Two-solvent system: polymer dissolved in strong solvent, diluted with water/ethanol/propylene glycol prior to placement to reduce solubility	Yes	High risk (claims 6–8; claim 19 parallel)
Preformed biodegradable scaffold/implant (manufactured solid depot) placed directly without solvent exchange precipitation	No	Lower risk to the in-situ formation mechanism (independent mechanism not met)
Thermally setting hydrogel/implant crosslinks via pH/ionic strength	No	Lower risk (different trigger)
Photocrosslinkable systems	No	Lower risk (different trigger)
Polymer solidifies via chemical crosslinking after placement (enzymatic/chemical)	No to partial	Lower risk unless solvent diffusion and coagulation are still core mechanism
In situ implants where solvent is non-diffusing or volatile removed differently	Partial	Depends on whether solvent “dissipates/diffuses” into body fluid and triggers coagulation

Key Takeaways

US 5,739,176 is built around solvent-exchange in-situ forming depots: dissolving a water-insoluble biodegradable thermoplastic in a biocompatible water-soluble organic solvent (or solvent mixture), then relying on solvent dissipation/diffusion into body fluid to drive polymer coagulation/solidification.
The claim set is broad across:
- PLA/PLGA/PCL-like polymers and other biodegradable thermoplastics/polyanhydrides,
- many named solvents (notably NMP, DMSO, acetone, 2-pyrrolidone, plus others),
- two-solvent systems using water/ethanol/propylene glycol as the poorer solvent,
- multiple anatomical implant functions and needle delivery.
Combination claims add coverage for biologically active agents with release via diffusion and/or erosion, with agent categories kept very broad.
FTO analysis driven by the exact competitor mechanism should focus on whether the product uses the same physical trigger (solvent diffusion/precipitation causing polymer solidification) and whether the polymer and solvent fall inside the enumerated or functionally equivalent scopes.

FAQs

What polymer-solvent pairs are most directly covered by 5,739,176?
PLA/PLGA/PCL-type biodegradable thermoplastics dissolved in solvents like NMP, 2-pyrrolidone, DMSO, and acetone, including solvent mixtures with weaker/non-solvent components such as water, ethanol, or propylene glycol.
Does 5,739,176 cover in-situ implants delivered by needle?
Yes. The method claims explicitly include delivery through a needle.
Are biologically active agent payloads covered?
Yes. Dependent claims add broad biologically active agents and specify release by diffusion, erosion, or combinations.
Is the patent limited to one therapeutic indication or one body site?
No. Claims list multiple implant sites and functions, including wounds, bone defects, soft tissue scaffolds, periodontal pockets, and eye cul-de-sac.
What is the most important design-around lever against 5,739,176?
Avoiding the claimed solvent diffusion/dissipation triggering polymer coagulation/solidification mechanism, or using polymer and solvent systems that do not meet the claimed solubility-to-solidification conditions.

References

(No sources cited because only claim text was provided and no bibliographic identifiers, assignee details, family data, or external patent databases were included in the input.)

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	0436667	⤷ Start Trial	91193	Luxembourg	⤷ Start Trial
European Patent Office	0436667	⤷ Start Trial	C300204	Netherlands	⤷ Start Trial
Austria	151257	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,739,176

Summary for Patent: 5,739,176