United States Patent 5,614,520: Scope, Claim Architecture, and Landscape Implications
US Drug Patent 5,614,520 claims 2-arylthiazole derivatives and pharmaceutically acceptable salts, framed as a genus with broad substituent definitions on both the aryl moiety (Ar) and the heterocycle substituent pattern (X and Y, plus X/Y-compatible constraints). It also claims pharmaceutical compositions and a gout/hyperuricemia treatment method using a uric-acid lowering effective amount.
This is a classic early-generation medicinal chemistry patent: wide structural coverage, heavy reliance on Markush-style definitions, and multiple layered “proviso” constraints meant to reduce overlap while preserving a large design space.
What does US 5,614,520 claim, in plain structural terms?
Core scaffold
Claim 1 is directed to a compound of formula (I):
- 2-arylthiazole derivative
- pharmaceutically acceptable salt allowed
- Ar can be either:
- an unsubstituted/substituted furyl group, or
- a group defined by formula (II) with substituents R1, R2, R3 (and additional substituent options described below)
The claim then defines:
- substituent pattern on the thiazole framework through X and Y
- additional substitution permissibility limits through multiple provisos
Substituent universe for Ar (formula II)
Claim 1 expands R1, R2, R3 as:
- hydrogen, halogen, or nitro/cyano/formyl for the simpler case of R1/R2/R3
- or broader groups:
- OR
- S(O)nR (sulfoxide/sulfone depending on n)
- NRR1 (tertiary/secondary amino options with heterocycle possibilities)
- or COR" (carbonyl with R" alkyl/aryl/aralkyl)
And it imposes constraints that at least one of R1, R2, R3 is other than hydrogen, plus multiple interaction rules when hetero-substituted groups appear.
How broad is Claim 1’s Markush coverage?
Claim 1 is a high-coverage genus with layered restrictions
Claim 1 includes:
- multiple admissible substituent classes for R1/R2/R3
- permissive size definitions (C1-10, C1-14, C1-5, etc.)
- multiple “at least one” and “not both” provisos governing halogen/hydrogen coexistence and OR compatibility
The overall structure gives a large combinatorial scope:
- Ar selection: furyl or formula (II)
- R1/R2/R3: each can be from a wide enumerated set
- X and Y: each is independently defined within limits, with a key exclusion on simultaneous carboxyl-like functionality
Key constraints that narrow but do not collapse the genus
Claim 1 contains the following structural narrowing rules (highly relevant for freedom-to-operate and design-around):
- At least one of R1, R2, R3 is not hydrogen.
- If any of R1/R2/R3 is halogen or alkoxy or alkylamino or nitro, then at least one of the other two is not hydrogen.
- If one of R1/R2/R3 is a halogen and another is hydrogen, then the remaining group must be not halogen or be alkoxy/alkylamino/acylamino.
- If any of R1/R2/R3 is OR, then the remaining groups cannot present the prohibited hydrogen/OR combinations:
- the one paired with OR cannot be hydrogen
- and the other cannot make the two remaining groups both OR simultaneously
- Nor do all of R1–R3 represent halogen at the same time.
- X and Y cannot both be carboxyl, alkoxycarbonyl, carbamoyl, or aminocarbonyl at the same time.
This means Claim 1 covers compounds where X/Y represent at least one non-carboxyl-like functionality, and where Ar substitution patterns avoid certain “extreme” combinations.
What are the dependent claim layers doing?
Dependent claims progressively lock in narrower substitution subsets while preserving method and composition coverage.
Claim 2 (tightens Ar substitutions)
Claim 2 narrows:
- Ar must be formula (II)
- R1 is specifically halogen or nitro/cyano/formyl
- R2 is specifically drawn from:
- R3 is hydrogen or halogen
This reduces the admissible R2 and R3 patterns relative to Claim 1.
Claim 3 (tightens X and Y)
- X is narrowed to carboxyl or alkoxycarbonyl/carbamoyl/aminocarbonyl
- Y is narrowed to hydrogen or C1-4 alkyl
Claim 4 (tightens exact aryl meta substitutions and X/Y)
- R1 is m-nitro or m-cyano
- R2 is from OR / S(O)nR / NRR'
- R3 is hydrogen
- X is carboxyl or alkoxycarbonyl/carbamoyl/aminocarbonyl
- Y is hydrogen or C1-4 alkyl
Claim 5 and Claim 6 (m-halogen series)
- Claim 5: m-halogen on R1; R2 from OR/S(O)nR/NRR'; R3 hydrogen/halogen.
- Claim 6: m-halogen on R1; R2 from OR/S(O)nR/NRR'; R3 hydrogen/halogen; plus X in aminocarbonyl set and Y = C1-4 alkyl
Claim 7 and Claim 8 (literal sub-genus examples with explicit R groups)
These claims introduce two additional explicit families:
- Claim 7: formula (I-a) with:
- R1-a = C2-8 alkoxy OR morpholino OR 4-N-methylpiperazine-1-yl OR piperidino OR benzoyl (optionally methyl/chloro/methoxy substituted)
- R2-a = nitro/cyano/hydrogen depending on the specific R1-a option
- Claim 8: formula (I-b) with:
- R1-b = OR or SR (R = C2-8 alkyl/morpholino/4-N-methylpiperazine-1-yl/piperidino)
- R2-b = nitro/trifluoromethyl/cyano
- Yb = hydrogen or methyl
- plus an additional case where R1-b is a phenyl-substituted cyclic group (defined via an additional formula)
Claim 9 and Claim 10 (small final narrowing set and alternative formula variant)
- Claim 9: when X = carboxyl, Y = hydrogen or C1-4 alkyl
- Claim 10: a modified formulation of claim 1 with:
- X explicitly required to be carboxyl or alkoxycarbonyl/carbamoyl/aminocarbonyl
- y instead of Y, with the same hydrogen vs C1-4 alkyl pattern
- it also includes an expanded description for R2/R3 admissibility and carbonyl options
What else is claimed besides the molecules?
Compositions
- Claim 11: pharmaceutical composition comprising an effective amount of the Claim 1 compound.
- Claim 12: composition where Ar and R1/R2/R3 include the enumerated subsets and X is the aminocarbonyl-like set.
- Claim 13: when X = carboxyl, Y = hydrogen or C1-4 alkyl.
- Claim 14: composition comprising an effective amount of the Claim 10 compound.
Method of treatment
- Claim 15: method for treating gout or hyperuricemia by administering a uric acid-lowering effective amount of the composition of Claim 11.
From a landscape perspective, Claim 15 is a key linkage: it creates a therapeutic method “hook” that can remain enforceable even if some molecule-level features vary, depending on how substituent differences are evaluated under claim construction.
What is the enforceable “scope map” by functional handles (X/Y and Ar substitution)?
Handle 1: X and Y
Claim 1’s most meaningful narrowing is:
- each of X and Y can be hydrogen or various carbonyl/amine-derived substituents
- X and Y cannot simultaneously be carboxyl or carboxyl-like defined groups (carboxyl, alkoxycarbonyl, carbamoyl, aminocarbonyl) at the same time
Claim 3/4/6/9/10 further stabilize these patterns, typically forcing:
- X to be a carboxyl-like group
- Y to be hydrogen or C1-4 alkyl
Handle 2: Ar substitution pattern (R1/R2/R3)
Claim 1’s provisos constrain:
- OR placement relative to other substituents (no “OR + OR with hydrogen” combinations)
- halogen distributions (not all halogens, and not halogen plus hydrogen with the third halogen)
- nitro triggers enforce non-hydrogen at adjacent positions by at least one other non-hydrogen substituent
Claim 2/4/5/6 encode additional fixed positional substitution limitations (m-nitro, m-cyano, m-halogen).
Where does the patent likely sit in the prior-art/landscape structure?
Even without test data or the full specification, the claim structure signals the likely landscape role:
- Genus claim on 2-arylthiazoles with broad substituent options.
- Compositional claims and therapeutic gout/hyperuricemia method.
- A set of dependent claims that correspond to specific substituent motifs (nitro/cyano/formyl/halogens on aryl, with X carboxyl-like groups and Y hydrogen or C1-4 alkyl).
In practical patent landscaping:
- this type of claim tends to be a “broad plate” that can block many close analogs unless a competitor changes:
- the thiazole core positioning,
- the aryl/heteroaryl identity, or
- the X/Y functional pattern so that it violates the “simultaneous carboxyl-like” constraint or the OR/halogen provisos.
How to evaluate claim coverage against competitor molecules (practical check list)
Step-by-step infringement screening against Claim 1
- Confirm the compound is a 2-arylthiazole derivative (core identity).
- Identify Ar:
- furyl or formula (II) must match
- Map R1/R2/R3 on formula (II):
- verify each is within allowed groups
- verify at least one of R1/R2/R3 is not hydrogen
- check all provisos:
- halogen/hydrogen mix rules
- OR placement rules
- “not all halogens” rule
- Map X and Y:
- verify each is within allowed sets
- verify the constraint: not both carboxyl-like groups simultaneously
- Confirm salt eligibility (phys pharm salt).
Dependent claim “tight lanes”
If a candidate structure fails Claim 1 due to one proviso, it may still be captured by a narrower dependent claim only if it exactly matches that dependent subset:
- Claim 3/4/6/9/10: X locked and Y restricted
- Claim 4/5/6: R1 positional meta substituent classes, with R3 restrictions
Method and composition
If a compound hits the molecule claims, the following typically follow:
- composition (Claims 11-14)
- method (Claim 15) where dosing is “uric acid-lowering effective amount” for gout/hyperuricemia.
Patent-landscape positioning: what types of later patents get blocked or pushed?
Given the claim breadth, US 5,614,520 most strongly impacts later filings that:
- keep the 2-arylthiazole scaffold,
- vary only within the stated Ar substituent universe and X/Y functional classes, and
- still present X/Y combinations that avoid the prohibited simultaneous carboxyl-like pairing (meaning competitors must sometimes actively design around).
Later patents that may survive despite similarity generally do one of:
- change the core away from the 2-arylthiazole formula (I)/(I-a)/(I-b) definition,
- change the Ar frame so that it is not a furyl or not formula (II),
- choose X/Y combinations that violate the Claim 1 simultaneous carboxyl-like constraint,
- adopt OR/halogen patterns that fail the provisos.
Key Takeaways
- US 5,614,520 is a broad genus claim on 2-arylthiazole derivatives with extensive Markush coverage on Ar (R1/R2/R3) and thiazole substituents (X and Y).
- The enforceable narrowing comes from provisos: at least one Ar substituent must be non-hydrogen; halogen and OR placements cannot form specific forbidden combinations; X and Y cannot both be carboxyl-like groups.
- Dependent claims lock therapeutically relevant subsets (notably X carboxyl-like groups with Y hydrogen or C1-4 alkyl, and aryl meta nitro/cyano/halogen patterns).
- The patent extends beyond molecules into:
- pharmaceutical compositions (Claims 11-14)
- gout/hyperuricemia treatment method via “uric acid-lowering effective amount” (Claim 15).
- In landscape terms, the patent is likely a blocking reference for analogs that preserve the scaffold and functional patterns while only varying substituents inside the same Markush envelope.
FAQs
1) Does US 5,614,520 claim salts?
Yes. Claim 1 explicitly covers the 2-arylthiazole derivative and “a pharmaceutically acceptable salt thereof.” This extends coverage to salt forms without changing the core structure.
2) What is the single most important structural limitation in Claim 1?
The X/Y constraint: both X and Y cannot represent carboxyl, alkoxycarbonyl, carbamoyl, or aminocarbonyl group at the same time (Claim 1).
3) Are OR-substituted aryl patterns fully allowed?
No. Claim 1 includes provisos that restrict OR combinations relative to hydrogen and the other R groups. If any of R1/R2/R3 is OR, then specific forbidden pairings with hydrogen and OR-by-both remaining groups are excluded.
4) Does the patent include therapeutic claims for gout/hyperuricemia?
Yes. Claim 15 is a method claim for treating gout or hyperuricemia using a uric acid-lowering effective amount of the composition in Claim 11.
5) Where do dependent claims most concentrate the narrowing?
On specific Ar substitution sets (e.g., m-nitro/m-cyano/m-halogen patterns) and on tight X/Y selections, especially those where X is carboxyl-like and Y is hydrogen or C1-4 alkyl (Claims 3, 4, 6, 9, 10).
References (APA)
[1] U.S. Patent 5,614,520. (n.d.). 2-arylthiazole derivatives and uses thereof.
