United States Patent 5,380,922: Scope, Claims, and Patent Landscape for a Hydroxynaphthoate Micronized Salt
US Drug Patent 5,380,922 claims a specific API salt and tightly defined solid-state morphology and powder-handling properties, paired with defined micronization and crystallization/quenching processes. The claim set is structured around (i) the hydroxynaphthoate salt identity and (ii) spherical accretions of microcrystals with quantitative particle and flow metrics that constrain infringement and enable design-around.
What exactly is claimed under 5,380,922?
Core product: a specific salt with constrained morphology
The independent claim (Claim 1) defines:
- Salt form: “1-Hydroxy-2-naphthalenecarboxylate salt” of
4-hydroxy-α-1-[[[6-(4-phenylbutoxy)hexyl]amino]methyl]-1,3-benzenedimethanol
- Solid form: “in the form of spherical accretions of microcrystals”
- Powder attributes: “free-flowing, friable and micronisable”
Claims 2–10 then narrow the asserted solid-state phenotype with quantitative ranges and structural description.
Key quantitative constraints (Claims 2–9)
These ranges control both literal infringement and validity risk (because they tie to measurable powder properties):
| Claim |
Parameter |
Claimed range |
| 2 |
Mean particle size |
70 to 300 μm |
| 3 |
Mean surface area |
4 to 12 m²/g |
| 4 |
Particle size distribution |
100 to 1000 μm |
| 5 |
Aerated bulk density |
0.2 to 0.5 g/mL |
| 6 |
Cohesivity |
0 to 20% |
| 7 |
Uniformity coefficient |
1 to 5 |
| 8 |
Angle of repose |
25° to 50° |
| 9 |
Compressibility |
5 to 25% |
Structural constraint (Claim 10)
Claim 10 adds a morphology requirement:
- “thin crystalline plates arranged radially about a central core or void”
within each spherical accretion.
This is not a purely functional statement; it is a microstructure claim that typically requires microscopy confirmation or equivalent characterization.
How is infringement strengthened by dependent claims 24–30?
The later dependent claims 24–30 pick narrower sub-ranges for several parameters:
| Claim |
Parameter |
Narrowed range / point |
| 24 |
Mean particle size (depends on Claim 2) |
100 to 200 μm |
| 25 |
Mean surface area (depends on Claim 3) |
6 to 10 m²/g |
| 26 |
Aerated bulk density (depends on Claim 15 per text) |
0.3 to 0.4 g/mL |
| 27 |
Cohesivity (depends on Claim 6) |
0 to 5% |
| 28 |
Uniformity coefficient (depends on Claim 7) |
about 3 |
| 29 |
Angle of repose (depends on Claim 8) |
40° to 50° |
| 30 |
Compressibility (depends on Claim 9) |
8 to 20% |
Practical effect: even if a competitor’s salt matches the identity (hydroxynaphthoate) and spherical accretions concept, infringement can still fail if powder metrics fall outside these ranges.
What process claims are asserted, and what do they require?
Micronization process (Claim 11)
Claim 11 covers micronizing the claimed spherical microcrystal accretion salt:
- Feed the hydroxynaphthoate salt “in the form of spherical accretions of microcrystals… free-flowing, friable and micronisable”
- Micronize in a microniser
- Collect micronized material
This claim is broad on micronization equipment but narrow on the feed form.
Crystallization / quenching process (Claims 12–22)
Claim 12 is the main synthetic/solid-form process:
- Quench a hot organic or hot aqueous organic solution of the hydroxynaphthoate salt with a cold organic or cold aqueous organic solvent
- Form spherical accretions of microcrystals
- Collect accretions
Claims 13–22 then constrain solvent class, temperature windows, and the mixture temperature ceiling.
Boiling point constraint (Claim 14, 31):
- Hot solvent boiling point 40 to 150°C (Claim 14)
- Narrowed: 60 to 120°C (Claim 31)
Hot solvent type (Claims 15, 16, 32, 33):
- From: lower C1–4 alkyl alcohol / ether / ester (Claim 15)
- Prefer: lower C1–4 alkyl alcohol (Claim 16)
- Narrow examples: methanol, ethanol, isopropanol (Claim 32)
- Narrow further: methanol (Claim 33)
Cold solvent freezing point constraint (Claims 17, 18, 34, 35):
- Freezing point -150 to -20°C (Claim 17)
- Solvent may be lower C1–4 alkyl alcohol / ether / ester (Claim 18)
- Examples: methanol, ethanol, isopropanol (Claim 35)
- Narrow examples: isopropanol (Claim 36)
- Another narrower example for freezing point: -130 to -150°C (Claim 34)
Temperature windows (Claims 20–22, plus dependent windows 37–39):
- Hot solution temperature: 30 to 80°C (Claim 20)
- Cold solvent temperature: -35 to +15°C (Claim 21)
- During quenching: mixture maintained below about +20°C (Claim 22)
- Narrowed: 40 to 70°C (Claim 37)
- Narrowed: -25 to +10°C (Claim 38)
- Narrowed: -10 to +20°C (Claim 39)
Route to form the hot hydroxynaphthoate solution (Claim 23)
Claim 23 ties the hot solution preparation to:
- Mixing 1-hydroxy-2-naphthoic acid and the 4-hydroxy-α-1-[[[6-(4-phenylbutoxy)hexyl]amino]methyl]-1,3-benzenedimethanol in a hot organic or hot aqueous organic solvent.
Practical effect: a competitor who uses a different preparation route that avoids the claimed intermediate solution preparation may still infringe process claims 12–22 if they still perform the same quench and get the same spherical accretion phenotype, but Claim 23 can raise enforcement leverage if asserted.
What is the scope boundary and where are the likely “design-around” pressure points?
1) Identity boundary: hydroxynaphthoate salt
All product/process claims are anchored to the 1-hydroxy-2-naphthalenecarboxylate (hydroxynaphthoate) salt of the specified benzenedimethanol derivative.
- Substituting a different counterion is the cleanest design-around conceptually.
- Changing the cation (the benzenedimethanol derivative) is also a clean break, but typically not an option if the competitor targets the same drug.
2) Morphology boundary: spherical accretions of microcrystals
The claims repeatedly require:
- spherical accretions of microcrystals
- each with microstructure described as thin plates radially arranged around a central core/void (Claim 10)
If a competitor produces a different polymorph or agglomeration type (needles, granules, platelets without the radially arranged plate-on-core architecture), they can avoid literal infringement even if particle sizes are similar.
3) Powder property boundary: the numeric windows
Claims 2–9 and 24–30 create measurable barriers:
- Mean particle size: 70–300 μm (and narrower 100–200 μm)
- Mean surface area: 4–12 m²/g (and narrower 6–10 m²/g)
- Bulk density, cohesivity, uniformity coefficient, angle of repose, compressibility
Enforcement often turns on which characterization method and which sample represents the infringing product lot. The claim set is drafted to limit ambiguity by requiring specific property ranges.
4) Process boundary: hot/cold solvent quench with constrained temperatures
For infringement on process claims 12–22, a challenger must show:
- use of hot organic or hot aqueous organic solution
- quench with cold organic or cold aqueous organic solvent
- quenching temperature controls below +20°C during quench
- hot solvent boiling point and cold solvent freezing point constraints
A competitor using a different crystallization control strategy, such as anti-solvent addition at different temperature profiles, vapor-phase processes, or solvent systems outside the defined boiling/freezing windows, may be positioned to argue non-literal infringement.
How the claim architecture maps to enforceable “centers of gravity”
Product enforceability is strongest on Claims 1–10 + 2–9
- Claim 1 sets the foundation: salt identity + spherical accretions + flowability/friability/micronisability
- Claims 2–9 add numeric boundaries that narrow scope enough to create enforceable distinctions
- Claim 10 adds microstructure architecture
Process enforceability is strongest on Claims 12–22
- Claim 12 is broad on quenching solvents being organic or aqueous organic, but restricted by the phenotype it creates
- Claims 14–22 narrow the solvent boiling point, freezing point, and temperature ceilings into a tight operating envelope
Micronization is enforceable only if the starting material matches the phenotype
- Claim 11 requires the starting hydroxynaphthoate salt to be in the spherical accretion microcrystal form and described powder attributes.
What does the “patent landscape” look like around this asset?
A full landscape requires bibliographic family mapping, prosecution history, and citing/competing patents across jurisdictions. None of that bibliographic information is provided here, and generating it would risk fabricating facts.
What can be stated from the claim text alone is the likely competitive relevance model:
- This patent targets a salt form plus a specific particle engineering approach (spherical accretions of microcrystals with defined powder metrics).
- The commercial threat is less about chemistry and more about formulation manufacturing. Competitors can potentially sell a different salt form or a different solid-state morphology, or manufacture a different particle phenotype through different crystallization/quenching conditions.
- The micronization step is downstream. If competitors purchase alternative solid form or produce non-matching microcrystal accretions, they can avoid Claim 11 even if they micronize later.
Key Takeaways
- US 5,380,922 is a salt + solid-state phenotype patent centered on a 1-hydroxy-2-naphthalenecarboxylate (hydroxynaphthoate) salt of a specified benzenedimethanol derivative.
- Enforcement hinges on producing spherical accretions of microcrystals that are free-flowing, friable, micronisable, with quantified powder properties (particle size, surface area, bulk density, cohesivity, uniformity coefficient, angle of repose, compressibility).
- Claim 10 adds a microstructural requirement: thin crystalline plates radially arranged around a central core or void.
- Process risk is concentrated in hot/cold solvent quenching with explicit boiling point, freezing point, and temperature constraints, plus the phenotype outcome (spherical accretions).
- The most direct design-arounds are: change the counterion, avoid the spherical accretion phenotype/microstructure, or use quenching/solvent/temperature regimes outside the claimed windows.
FAQs
1) Does Claim 1 require specific particle size ranges?
No. Claim 1 requires spherical accretions of microcrystals that are free-flowing, friable, and micronisable. Specific numeric particle size constraints appear in dependent Claims 2–4 (and narrower ranges in later dependents).
2) Which claim most directly ties to microstructure rather than powder metrics?
Claim 10, which requires thin crystalline plates arranged radially about a central core or void.
3) If a competitor makes the same salt but produces different morphology, is infringement likely?
Claim 1 requires spherical accretions of microcrystals, and Claim 10 requires a specific radial plate-on-core/void architecture. Different morphology can avoid literal infringement even if other properties overlap.
4) Are micronization claims independent of how the salt was prepared?
Claim 11 depends on the feed being the claimed spherical accretion microcrystal hydroxynaphthoate salt with the stated powder attributes. If the purchased material does not match the phenotype, Claim 11 can fail.
5) Which parameters are the tightest practical control points for manufacturing?
The numeric powder property ranges in Claims 2–9 and the solvent/temperature constraints in Claims 14–22 (boiling point, freezing point, quench mixture temperature below about +20°C).
References (APA)
[1] United States Patent 5,380,922.
