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Patent landscape, scope, and claims: |
United States Patent 5,840,722: Scope, Claim Structure, and Endothelin-Receptor Inhibition Landscape
US Patent 5,840,722 claims a method of inhibiting endothelin receptors through administration of a large, flexible chemical genus defined by Formula I. The scope is built around a “pharmacophore-by-substitution” strategy: the claims do not merely cover one molecule; they cover broad classes of substituted compounds with wide latitude in aromatic, heteroaromatic, cyclic, and linker elements, plus flexible substitution patterns.
What does US 5,840,722 claim, in plain claim scope terms?
Claim type and operative language
The claim is a method claim:
- “A method of inhibiting endothelin receptors”
- by administering to a patient a compound of Formula I
So infringement hinges on:
- the administered compound falling within Formula I (including all variable definitions), and
- the compound’s use to inhibit endothelin receptors (therapeutic use framing is explicit in the claim).
Formula I role
The claim turns entirely on whether the administered compound fits the variable definitions for substituents R (including R is formyl / carboxy / hydrolyzable carboxy equivalents) and the many substituent groups R2, X, R3, R4 (and R5), R6, Y, Z.
How broad is the chemical genus under Formula I?
The genus is extremely broad because the claim simultaneously permits:
- multiple terminal functional options for R (formyl or carboxylic acid or prodrug-like “hydrolyzable to COOH” forms),
- halogen and small alkyl/alkoxy/alkylthio substitution at multiple sites,
- wide substitution freedom on phenyl/naphthyl and on multi-ring heteroaromatics,
- several ring-linking topologies driven by:
- X (nitrogen or carbon where substitution creates small saturated/unsaturated ring closures via an ether-like replacement),
- R3 linking options to form 5- or 6-member rings,
- R4 and R5 ring-forming constraints (3-member ring with hetero-atom allowance),
- aliphatic and cyclic substituents ranging from C3–C12 cyclic/cyclic-unsaturated systems,
- Y and Z being sulfur or oxygen (or in one case a bond), which expands heteroatom patterning in the scaffold.
Key breadth drivers (where the claim expands coverage)
-
R definition is a terminal functional variant set
- R = formyl
- or CO2H
- or a radical hydrolyzable to COOH
This captures both acids and acid-labile prodrugs.
-
Global halogen/alkoxy/alkylthio latitude
- R2 allows halogen, C1-C4 alkyl, C1-C4 haloalkyl, C1-C4 alkoxy, C1-C4 haloalkoxy, C1-C4 alkylthio.
- Similar permissive sets recur for R3 and in multiple other substituent positions.
-
Multiple ring families
- Repeated inclusion of:
- phenyl and naphthyl,
- substituted phenyl derivatives with multiple substituents,
- heteroaromatic rings with 1 to 3 nitrogen atoms and/or O/S,
- cycloalkyl and cycloalkenyl groups with heteroatom inclusion.
-
Linker and ring-closure variables
- X can be nitrogen or carbon (CR14) where R14 is hydrogen or together with R3 forms a 3- or 4-member alkylene/alkenylene chain with one methylene replaced by oxygen.
- R3 is also allowed to be linked to R14 to form a 5- or 6-member ring.
- R4 and R5 can form a 3-member ring that can contain one oxygen or sulfur.
- These options broaden structural coverage beyond a single scaffold.
What is the variable-by-variable scope?
Terminal substituent R
- R is formyl, CO2H, or a radical hydrolyzable to COOH.
Infringement implication: if a prodrug hydrolyzes in vivo to the claimed acid, the compound can still fall within scope if the prodrug itself is a “compound of the formula I” under the definition.
R2
- Halogen
- C1-C4 alkyl
- C1-C4 haloalkyl
- C1-C4 alkoxy
- C1-C4 haloalkoxy
- C1-C4 alkylthio
X
- Nitrogen OR CR14
- R14 = hydrogen, OR
- R14 and R3 together form a 3- or 4-membered alkylene or alkenylene chain where one methylene is replaced by oxygen.
R3
- Allowed standalone substituents include:
- halogen
- C1-C4 alkyl
- C1-C4 haloalkyl
- C1-C4 alkoxy
- C1-C4 haloalkoxy
- C1-C4 alkylthio
- Or R3 can link to R14 to form a 5- or 6-membered ring (same general constraint family tied to the X/R14 framework).
R4
R4 is the most structurally expansive position because it allows many aromatic, cycloalkyl, and heteroatom-bearing cyclic/aryl systems, including multi-halogen substitution patterns.
R4 = any of the following broad classes (as described in the claim):
-
C1-C10 alkyl (which may carry 1–5 halogens)
- and/or additional radicals selected from:
- C1-C4 alkoxy
- C1-C4 alkylthio
- cyano
- C1-C8 alkylcarbonyl
- C1-C8 alkoxycarbonyl
- phenyl / phenoxy / phenylcarbonyl
- and phenyl variants can carry:
- 1–5 halogens and/or 1–3 of:
- C1-C4 alkyl
- C1-C4 haloalkyl
- C1-C4 alkoxy
- C1-C4 haloalkoxy
- C1-C4 alkylthio
-
C1-C4 alkyl (with up to 1–5 halogens) carrying a substituted heteroaromatic radical:
- a 5-member heteroaromatic ring containing 1–3 nitrogen atoms and/or one S or O
- that heteroaromatic ring can carry:
- 1–4 halogens
- and/or 1–2 groups selected from the same C1-C4 alkyl/haloalkyl/alkoxy/haloalkoxy/alkylthio set
- and/or phenyl substituent latitude (as stated)
-
C3-C12 cycloalkyl or C3-C12 cycloalkenyl
- allowed to contain one oxygen or sulfur atom
- with up to 1–5 halogens
- plus substituent radicals from the same C1-C4 group set and “carbonyl/aryl” sets (phenyl/phenoxy/phenylcarbonyl; alkyl/alkoxycarbonyl etc.)
-
C3-C8 alkenyl or C3-C6 alkynyl
- also up to 1–5 halogens
- plus the same substitution set (C1-C4 alkyl, alkoxy, alkylthio, cyano, alkylcarbonyl, alkoxycarbonyl, phenyl/phenoxy/phenylcarbonyl with phenyl further substituted)
-
Five- or six-member heteroaromatic ring with:
- 1–3 nitrogen atoms and/or one S or O
- 1–4 halogens
- and/or 1–2 of:
- C1-C4 alkyl
- C1-C4 haloalkyl
- C1-C4 alkoxy
- C1-C4 haloalkoxy
- C1-C4 alkylthio
- phenyl/phenoxy/phenylcarbonyl
- phenyl within that definition can further carry:
- 1–5 halogens and/or 1–3 of:
- C1-C4 alkyl
- C1-C4 haloalkyl
- C1-C4 alkoxy
- C1-C4 haloalkoxy
- C1-C4 alkylthio
-
Phenyl or naphthyl, substituted by:
- one or more of: halogen, nitro, cyano, hydroxyl, C1-C4 alkyl, C1-C4 haloalkyl, C1-C4 alkoxy, C1-C4 haloalkoxy, phenoxy, C1-C4 alkylthio, amino C1-C4 alkylamino, C1-C4 dialkylamino.
-
R4 and R5 together form with adjacent carbon a 3-member ring:
- can contain one oxygen or sulfur
- and can carry 1–3 of: C1-C4 alkyl, halogen, C1-C4 haloalkyl, C1-C4 alkoxy, C1-C4 haloalkoxy, C1-C4 alkylthio.
R4 versus R5
The claim explicitly provides alternative frameworks:
- R4 is hydrogen, C1-C4 alkyl, C3-C8 cycloalkyl, C4-C4 haloalkyl, C4-C4 alkoxyalkyl, C1-C4 alkylthioalkyl, phenyl
- or R5 linked to R4 to form a 3- to 8-member ring.
R6
- R6 = C1-C? sufyl-alkyl (as written: “C1 sufyl-alkyl”; construed as sulfur-containing alkyl)
- or C3 alkenyl
- or C3 alkynyl
- or C3-C8 cycloalkyl
- each radical can be substituted by:
- halogen
- nitro
- cyano
- C1-C4 alkoxy
- C3-C6 alkenyloxy
- C3-C6 alkynyloxy
- C1-C4 alkylthio
- C1-C4 haloalkoxy
- C1-C4 alkylcarbonyl
- C4-C4 alkoxycarbonyl (as written)
- C1-C4 alkylamino / di-C1-C4 alkylamino
- phenyl / phenoxy / phenyl (substituted; claim states phenyl may be substituted 1 to 3 times by the standard halogen/nitro/cyano/alkyl/haloalkyl/alkoxy/haloalkoxy/alkylthio set)
- and R6 can include a substituted phenyl/naphthyl option with the same substituent families.
Y and Z
- Y = sulfur or oxygen or a single bond
- Z = sulfur or oxygen
Infringement implication: scaffold heteroatom patterning is broad enough to cover multiple electronic/solvation variants while remaining within the same claimed family.
How does this translate into therapeutic and competitive coverage in endothelin inhibition?
The claim is a method claim for endothelin receptor inhibition. While the claim text you provided does not list explicit receptor subtypes (ETA vs ETB) or therapeutic indications, the operative mechanism requirement is tight: it requires the administering compound to be used to inhibit endothelin receptors.
From a patent landscape standpoint, this matters because:
- if competing products are structurally within the Formula I genus, they can be stopped on method use, even if specific indications differ,
- if competitors use different scaffolds (outside the genus), the method claim does not block them unless another patent covers their structure or use.
What is the likely “scope perimeter” (what it covers vs what it does not)?
What it covers well
This claim is strongest where competitors share:
- a prodrug/acid pair concept for terminal R (formyl/CO2H/hydrolyzable-to-COOH),
- similar small halogen/C1-C4 substitution patterns,
- aromatic/heteroaromatic substitution density consistent with the claim’s “1–5 halogens” and “1–3/1–4 alkyl/alkoxy/alkylthio” allowances,
- similar scaffold heteroatom placements via Y/Z (O/S or bond).
What creates carve-out risk
Where competitors differ materially:
- by removing the Formula I structural framework such that their compound does not satisfy the allowed positions for R2/X/R3/R4/R6/Y/Z, or
- by using a terminal group that is not formyl / CO2H / hydrolyzable-to-COOH, or
- by using aromatic or cyclic motifs outside the permitted ring/heteroatom ranges stated in the claim.
Given the large genus, carve-outs likely require scaffold redesign, not just minor substituent swapping.
Patent landscape impact: what this claim structure means for freedom-to-operate
Landscape pattern created by broad genus definitions
A genus claim of this breadth typically behaves like a “net” for many close analogs. In practical landscape terms:
- many candidate endothelin inhibitors synthesized as substitution derivatives can fall within scope,
- downstream competitors often need non-overlapping scaffold patents or design-around by excluding key variable constraints.
Enforcement leverage of method claims
A method claim can be asserted:
- against prescribing and administration practices if the administered active is within the claimed genus,
- even when commercial products are marketed for standard endothelin indications, because the claim already frames the purpose as endothelin receptor inhibition.
What competitors usually do under this kind of claim? (Operational strategies)
Given the variable definitions, typical design-around strategies in this space (based on how these claims are drafted) include:
-
Terminal group redesign
- avoid having the functional equivalent that maps to formyl / CO2H / hydrolyzable-to-COOH at the same scaffold position.
-
Break the scaffold constraints
- choose a core structure that does not support the permitted X ring-closure logic, the R3-to-R14 linkage pattern, or the Y/Z heteroatom/bond definition.
-
Alter ring system category
- select an aryl/heteroaryl/cyclic system outside the explicit ranges:
- 5-member vs 6-member heteroaromatics with specific N/O/S count constraints,
- avoid the ring-closure that depends on R4/R5 forming a 3-member hetero-embedded ring or the stated 3- to 8-member topology via R4-R5 linkage.
-
Avoid the substitution lattice
- not just “different substituents,” but substituents that cannot be mapped into the exact allowed families (halogen/alkoxy/alkylthio/alkylcarbonyl/alkoxycarbonyl/phenylcarbonyl/heteroatom-bearing rings with defined nitrogen and oxygen/sulfur counts).
How to read claim breadth quantitatively
Because the claim is written as a nested set of permitted alternatives, the practical consequence is a very large number of potential structures. The claim grants latitude across:
- terminal functionality (3 buckets: formyl, CO2H, hydrolyzable-to-COOH),
- substituent families at multiple positions (halogen and C1-C4 alkyl/haloalkyl/alkoxy/haloalkoxy/alkylthio repeated),
- aromatic/heteroaromatic and cyclic “allowed containers,” and
- ring closure and heteroatom placement (X/R14 linking, R4/R5 forming 3-member heterorings, and Y/Z as O/S/bond).
This is characteristic of early broad filings where the patentee expects later examples to refine narrower embodiments, while the genus claim seeks maximal coverage.
Key Takeaways
- US 5,840,722 is a method-of-use patent that covers endothelin receptor inhibition via administration of a Formula I compound.
- The claim defines an extremely broad chemical genus, driven by wide variable ranges for terminal R, C1-C4 halo/alkoxy/alkylthio substitutions, multiple aromatic and heteroaromatic ring categories, and heteroatom/bond options via Y/Z.
- The scope perimeter is defined by whether an accused active maps into the specific variable constraints for R2, X, R3, R4/R5, R6, Y, Z, including ring-closure logic and terminal group definition.
- For freedom-to-operate, the claim creates strong risk for close substitution derivatives, and it pushes design-around toward scaffold-level changes (especially terminal group and structural linkage constraints), not just minor substituent edits.
FAQs
1) Does US 5,840,722 cover specific endothelin receptor subtype (ETA vs ETB)?
Your provided claim text frames the method as “inhibiting endothelin receptors” without specifying ETA or ETB subtype within the excerpt.
2) Is this a compound patent or a method patent?
It is a method of treatment claim requiring administration of a Formula I compound to inhibit endothelin receptors.
3) Can prodrugs be covered?
Yes. The claim permits R as a radical hydrolyzable to COOH, which is prodrug-like language for a carboxylic acid equivalent.
4) How many structural positions are variable in Formula I?
At least these are variable as defined: R, R2, X, R3, R4 (with R5 link logic), R6, Y, Z.
5) What is the fastest way to assess whether a competitor product falls within this claim?
Determine whether the product’s structure satisfies the claim’s exact variable mapping for the Formula I scaffold, especially:
- terminal R definition,
- the X/R14/R3 linkage and oxygen-in-chain rules,
- the R4/R5 ring-closure constraints,
- and the Y/Z O/S (or bond) definition.
References
- US Patent 5,840,722.
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