|
Patent landscape, scope, and claims: |
United States Patent 4,452,745: Scope, Claims, and Competitive Landscape
US Drug Patent 4,452,745 claims a family of substituted fluorene derivatives defined by a tight structural scaffold with defined substituent positions, limited ring/alkyl variability, and a full set of pharmaceutically acceptable salts and lower alkyl quaternary ammonium salts. Claim 23 locks to a specific compound name (“9-(3-isopropylaminopropyl)-9-aminocarbonylfluorene”), while dependent claims narrow to specific substituent classes and multiple example salt forms (hydrochloride and hydrobromide).
What does the claimed chemical space cover?
Core scaffold and substituent logic
The independent claim (Claim 1) defines a compound of a formula (as rendered in the claim) with substituent sets R1, R2, R3, and R6/R7, plus a defined parameter set A and n:
- R1: hydroxy, cyano, or CONR4R5
- R4/R5: each independently hydrogen or C1-C6 alkyl
- R2 and R3: independently drawn from
- hydrogen
- C1-C6 alkyl
- CH2-C2-C5 alkenyl
- phenyl-C1-C3 alkyl
- or, when taken together with the nitrogen they attach to, form a cyclic group of a defined formula where:
- R8 is hydrogen or C1-C4 alkyl
- A: CH2, O, or NH
- y: zero or one
- n: 3, 4, or 5
- R6 and R7: independently hydrogen, C1-C4 alkyl, or halogen
- Claim also covers:
- pharmaceutically acceptable salts of the compounds
- and lower alkyl quaternary ammonium salts (Claim 27)
Explicit constraint tying R1 to R2
Claim 1 includes a critical conditional narrowing:
- R2 is hydrogen when R1 is hydroxy
This eliminates combinations where hydroxy at R1 coincides with a non-hydrogen R2.
Headline breadth
Claim 1 is broad along several axes (R1 class, R2/R3 substituent types, n, and R6/R7). The breadth is constrained by:
- conditional substitution rule on R2 when R1 is hydroxy
- limited ranges: n = 3-5, R6/R7 = H/C1-C4 alkyl/halogen, R4/R5 limited to H or C1-C6 alkyl
- limited A and y (A in {CH2, O, NH}; y in {0,1})
How do the dependent claims narrow the scope and operationalize it commercially?
Master narrowing in Claim 2
Claim 2 narrows Claim 1 to a large but more specific subset:
- R1 remains {hydroxy, cyano, CONR4R5 with R4/R5 = H or C1-C6 alkyl}
- n = 3 or 4
- R6 and R7 = hydrogen
- R2/R3 substituent scope is restricted (relative to Claim 1) in two ways:
- R2/R3 allowed are fewer classes (hydrogen, C1-C6 alkyl, CH2-C2-C5 alkenyl, phenyl-C1-C3 alkyl)
- cyclic “taken together” option is constrained to:
- C4-C5 alkylene or --CH2CH2-O-CH2CH2--
This is a classic “commercial embodiment band” claim: wide enough to catch analogs, narrow enough to be defensible on distinct structure.
Further narrowing cascade: Claims 3-8
- Claim 3: “R1 hydroxy; R2 hydrogen; R3 C1-C6 alkyl”
- Claim 4: “R3 C1-C3 alkyl”
- Claims 5-8 lock R3 to specific alkyls:
- Claim 5: R3 = methyl
- Claim 6: R3 = ethyl
- Claim 7: R3 = n-propyl
- Claim 8: R3 = iso-propyl
This creates a direct track of first-generation analogs and provides strong coverage for stereochemically indifferent alkyl variants.
Cyano track: Claims 9-12
- Claim 9: “R1 cyano”
- Claim 10: “R3 C1-C6 alkyl”
- Claim 11: “R3 C1-C3 alkyl”
- Claim 12: “R3 iso-propyl”
This pairs with the hydroxy track to map the substitution options around R3.
Carbonyl (CONR4R5) track: Claims 13-15 and R3-dependent narrowing
- Claim 13: “R1 = CONR4R5”
- Claim 14: “R4 and R5 both hydrogen”
- Claim 15: “R6 and R7 both hydrogen”
Then Claim 16 adds:
- Claim 16: “R3 C1-C6 alkyl”
Then:
- Claim 17: “R2 hydrogen”
- Claim 18: “R3 C1-C3 alkyl”
- Claim 19: “n = 3”
- Claims 20-22 refine R3 further:
- Claim 20: “R3 methyl or ethyl”
- Claim 21: “R3 n-propyl”
- Claim 22: “R3 iso-propyl”
Named compound claim: Claim 23 (anchor to a specific marketed-ready entity)
- Claim 23: “9-(3-isopropylaminopropyl)-9-aminocarbonylfluorene”
This claim anchors the patent landscape around a concrete chemical identity. In competitive terms, Claim 23 is the highest-evidence point in the claim set because it ties the formula language to a single unambiguous structure name.
What salts and salt forms are explicitly claimed?
Acid addition salts (explicit)
- Claim 24: “pharmaceutically acceptable acid addition salt”
- Claim 25: hydrochloride
- “9-(3-isopropylaminopropyl)-9-aminocarbonylfluorene hydrochloride”
- Claim 26: hydrobromide
- “9-(3-isopropylaminopropyl)-9-aminocarbonylfluorene hydrobromide”
Quaternary ammonium salts (explicit)
- Claim 27: “C1-C6 alkyl quaternary ammonium salt”
- This signals that at least some members of the formula set can be present in quaternized ammonium form with lower alkyls.
Quaternary and acid salts under Claim 2
- Claim 2 explicitly includes:
- “pharmaceutically acceptable acid addition salts and lower alkyl quaternary ammonium salts thereof.”
How are n values handled across the claim set?
Claim 1 includes n = 3, 4, or 5, but dependent claims strategically cover n bands:
- Claim 2: n = 3 or 4
- Claim 28: “n = 4”
- Claim 29: “n = 5”
So the landscape contains:
- A “core” coverage for n = 3 and 4 through Claim 2
- Specific “reach” into n = 5 via Claim 29
What is the practical claim coverage map for analogs?
Coverage map by R1 class
| R1 class in claim |
Required additional constraints |
Dependent claim examples |
| Hydroxy |
Claim 1: if R1 is hydroxy then R2 = H |
Claims 3-8 specify R2 = H, R3 in {methyl, ethyl, n-propyl, iso-propyl} and constrain n indirectly via Claim 2 (n = 3 or 4) |
| Cyano |
Claim 1 allows cyano; Claim 9-12 focus on R3 alkyl and iso-propyl |
Claims 9-12: R3 = iso-propyl after narrowing to C1-C3 |
| Amidocarbonyl (CONR4R5) |
Claim 13; then Claim 14 fixes R4 = R5 = H; Claim 17 fixes R2 = H; Claim 18 limits R3 to C1-C3 |
Claim 23 provides named anchor: “9-(3-isopropylaminopropyl)-9-aminocarbonylfluorene” and salt variants |
“Named entity” impact
- Because Claim 23 is an explicit named compound, any competitor attempting a design-around must also track whether their structure falls outside the named scaffold and its exact substituent set, rather than relying on broad functional equivalence.
Salts as enforceable footholds
- Salt forms are explicitly included, at minimum:
- hydrochloride
- hydrobromide
- Quaternary ammonium salts are included broadly (C1-C6), so prodrug-like salt switching or formulation salt selection does not inherently avoid coverage.
What does this imply for the patent landscape (US enforcement posture)?
Within the provided text, there is no supporting data on:
- prosecution history,
- priority date,
- publication/issuance schedule,
- related family members,
- claim construction outcomes,
- or co-owned compound sets.
So the enforceable landscape that can be concluded from the claims themselves is limited to structure-based coverage for the listed substituent permutations and the specific named compound and its salts.
Landscape characterization from the claim architecture alone
- The claims are not limited to a single therapeutic indication within the text you provided; they are compound claims focusing on substitution patterns.
- The structure language is detailed enough to create multiple “entry points” for infringement analysis:
- general formula coverage in Claim 1,
- narrower “compound class” coverage in Claim 2,
- R1-specific tracks (hydroxy, cyano, CONR4R5),
- R3-specific analog ladder (methyl through iso-propyl),
- named compound anchor (Claim 23),
- salt forms (Claims 24-26),
- quaternary ammonium salts (Claims 2 and 27),
- n-specific reach (Claims 28-29).
Freedom-to-operate view: where design-arounds are most likely (based strictly on claim boundaries)
Without additional patent documents, the only defensible “avoidance” logic is to remain outside at least one hard claim constraint. The most structurally “pinning” constraints in the claim set are:
- R1 substituent class
- Hydroxy track requires R2 = hydrogen (Claim 1 logic; Claim 3 restates it).
- Cyano and CONR4R5 tracks have separate dependent ladders, including R4=R5=H for CONR4R5 (Claim 14).
- R6 and R7 must be hydrogen in Claim 2 and subsequent tracks
- Competitors whose analogs place substituents at those positions may avoid Claim 2-based coverage while still risking Claim 1.
- n value
- Claim 2 covers n = 3 or 4; Claim 29 covers n = 5. A competitor must analyze whether their preferred analog falls into none of these n values under the independent claim as well.
- salt status
- Acid addition salts are explicitly claimed, at least for the hydrochloride and hydrobromide of the named compound. For other members in the formula, “pharmaceutically acceptable salts” remain within the claim language.
Key claim set summary (what matters for enforcement and competitive mapping)
Independent claim coverage
- Broad formula claim with:
- R1 in {hydroxy, cyano, CONR4R5}
- R2/R3 defined by alkyl/alkenyl/phenyl-alkyl or cyclic take-together option
- A in {CH2, O, NH}
- y in {0,1}
- n in {3,4,5}
- R6/R7 in {H, C1-C4 alkyl, halogen}
- salts and quaternary ammonium salts
Narrow dependent claims that create “targetable” subsets
- Claim 2: restricts to n = 3 or 4, R6 = R7 = H, and narrows “taken together” ring variants
- Claims 3-8: hydroxy track with R2 = H and R3 in {methyl, ethyl, n-propyl, iso-propyl} via ladder
- Claims 9-12: cyano track with R3 limited down to iso-propyl
- Claims 13-22: carbonyl track with R4 = R5 = H, R6 = R7 = H, R2 = H, R3 = C1-C3 alkyl, with n = 3 in Claim 19 and R3 refined through Claims 20-22
- Claim 23: named compound anchor
- Claims 24-26: hydrochloride and hydrobromide for the named compound
- Claims 27: quaternary ammonium salts
- Claims 28-29: additional n-specific coverage
Key Takeaways
- US 4,452,745 is a structure-driven claim set covering substituted fluorene derivatives with defined substitution parameters R1/R2/R3/R6/R7, plus n = 3 to 5 and A in {CH2, O, NH}.
- The claim architecture builds enforcement options: a broad independent formula (Claim 1), a narrower class rail (Claim 2), R1-specific analog tracks, and an explicit named anchor compound in Claim 23.
- Salt coverage is built in: the named compound’s hydrochloride and hydrobromide are explicitly claimed, and lower alkyl quaternary ammonium salts are covered.
- The strongest competitive “watch points” for analog design are the hard constraints: R2 = H when R1 is hydroxy, R6/R7 = H in Claim 2 and the CONR4R5 track, n coverage including n = 5, and the carbonyl track’s R4 = R5 = H limitation.
FAQs
-
Which single claim most directly identifies the target compound for competitors?
Claim 23: “9-(3-isopropylaminopropyl)-9-aminocarbonylfluorene.”
-
Are salt forms explicitly claimed for the named compound?
Yes. Claim 25 covers the hydrochloride and Claim 26 covers the hydrobromide (both tied to the named compound).
-
Does the patent cover quaternary ammonium forms?
Yes. Claim 27 covers C1-C6 alkyl quaternary ammonium salts, and Claim 2 also includes lower alkyl quaternary ammonium salts.
-
What is the most restrictive conditional rule in Claim 1?
If R1 is hydroxy, then R2 is hydrogen.
-
How is the parameter n treated across the family of claims?
Claim 1 includes n = 3, 4, or 5; Claim 2 covers n = 3 or 4; Claim 29 separately covers n = 5.
References
[1] United States Patent No. 4,452,745 (claims as provided in the prompt).
More… ↓
⤷ Start Trial
|
