United States Patent 6,403,567: Scope of Claims and US Patent Landscape
US Patent 6,403,567 claims adenosine derivatives defined by a tight core scaffold and broad substituent options on a substituted pyrazole-linked group, paired with narrow method-of-use language aimed at “coronary steal” cardiac imaging via heart stress.
What is the claim coverage of US 6,403,567 at the molecular level?
Claim 1 (core Markush) defines a specific adenosine architecture
Claim 1 recites “a compound having the formula” with fixed portions and modular variation. The explicit substituent constraints in the claim are:
- R1 = —CH2OH
- R2 = H
- R4 = H
- R3 is selected from:
- CO2R20
- —CONR7R8
- aryl
- aryl is optionally substituted with 1 to 2 substituents independently from: halo, C1-6 alkyl, CF3, OR20
- R7 is selected from:
- H
- C1-8 alkyl
- aryl
- aryl substitution: the alkyl/aryl is “optionally substituted with one substituent” from: halo, aryl, CF3, CN, OR20
- each optional aryl substituent is optionally substituted with at least one substituent from: halo, alkyl, CF3, CN, OR20
- R8 is:
- R20 is:
Claim 1 scope in plain terms
The patent locks the adenosine substitution pattern to R1 = hydroxymethyl and removes variation at R2 and R4 (both hydrogen). The only meaningful chemical freedom is at R3 (carboxylate, amide, or aryl), and the amide N-substitution (R7/R8) and aryl substitution patterns.
This is a Markush claim with a defined core and a broad-enough R3/R7/R8/R20 parameter set to cover:
- ester-like prodrugs (via CO2R20 where R20 can be H or C1-8 alkyl),
- amide-linked analogs (via —CONR7R8 with N-substituents allowed),
- and aryl-substituted variants with limited aryl substitution count (1 to 2 substituents on the aryl defined within R3).
How do dependent claims narrow the chemical set?
Claims 2 to 6 progressively tighten the Markush parameters.
Claim 2 tightening
Claim 2 restricts R3 and limits substituent ranges:
- R3 limited to:
- CO2R20
- —CONR7R8
- aryl optionally substituted with 1 substituent from: halo, C1-3 alkyl, CF3, OR20
- R7 limited to:
- H
- C1-8 alkyl with one optional substituent from: halo, CF3, CN, OR20
- R8 limited to:
- R20 limited to:
Claim 3 tightening
- R3 aryl optional substitution reduced to 1 substituent from: halo, C1-3 alkyl, OR20
- R7:
- H or C1-3 alkyl
- optionally substituted with one substituent from: halo, CF3, CN, OR20
- R8 fixed to H
- R20: H or C1-4 alkyl
Claim 4 tightening (more constrained)
- R3 aryl optional substitution: 1 substituent from: halo, C1-3 alkyl, OR20
- R7: H or C1-3 alkyl
- R8 fixed to H
- R20: H or C1-4 alkyl
Claim 5 specific example
- R7 = methyl (with the structural constraints of claim 4)
Claim 6 specific prodrug/carboxylate selection
- R3 = —CO2Et (ethyl ester carboxylate form)
What specific compounds are explicitly enumerated?
Claim 7 (explicit list)
Claim 7 enumerates six specific named embodiments (all within the claim 1 scaffold):
- 2-(4-methylaminocarbonylpyrazol-1-yl)adenosine
- 2-(4-ethoxycarbonylpyrazol-1-yl)adenosine
- 2-[4-(4-chlorophenyl)pyrazol-1-yl]adenosine
- 2-[4-(4-methoxyphenyl)pyrazol-1-yl]adenosine
- 2-[4-(4-methylphenyl)pyrazol-1-yl]adenosine
- 2-(4-carboxypyrazol-1-yl)adenosine
This list anchors the practical chemical interpretation of the Markush variables:
- “pyrazol-1-yl” at the 2-position of adenosine
- R3 types map cleanly onto carboxylate/carboxy, amide, and aryl variants on the pyrazole ring.
Claim 8 (formula constrained)
Claim 8 defines a narrower formula subset:
- R1 = —CH2OH
- R2 = H
- R4 = H
- R3 = —CONR7R8
- R7 = methyl
- R8 = hydrogen
That is an explicit reduction to the methylamide (N-methyl, N-H absent because R8 = H means the amide has NH).
What product coverage exists via composition claims?
Claim 9 and 10
- Claim 9: “A pharmaceutical composition” comprising:
- a compound of claim 1
- and one or more pharmaceutically acceptable excipients
- Claim 10: composition of claim 9 “in the form of a solution”
This provides standard formulation coverage without specifying additional excipient identities or concentrations.
What is the method-of-use scope, and how narrow is it?
Claim 11: coronary vasodilation plus coronary steal for imaging
Claim 11 is a method of:
- stimulating coronary vasodilation in a mammal
- by administering a therapeutically effective amount of a claim 1 compound
- “sufficient to stress the heart and induce a coronary steal situation for the purposes of imaging the heart.”
This is not a general cardiovascular indication. It is tied to:
- mechanistic physiological effect: “coronary steal”
- operational use: “for the purposes of imaging the heart”
- system context: “stress the heart”
Claim 12: dosage range
- about 0.01 to about 100 mg/kg (weight of the mammal)
Claim 13: mammal limitation
What is the effective scope intersection: composition + method?
From a freedom-to-operate lens, US 6,403,567 has layered coverage:
- Compound claim (1): broad structural parameter space, but anchored to a fixed adenosine core substitution (R1 and R2/R4 constraints).
- Specific embodiments (7, 8): explicit inclusion of named analogs.
- Composition claim (9, 10): covers pharmaceutical formulations and solutions containing claim 1 compounds.
- Method claims (11-13): targets use for coronary steal imaging in humans, with dose range.
The method claims can be infringed without a particular formulation, provided the compound and use scenario match claim 11.
What does this imply for competitors: who is inside vs outside the claim set?
Inside the claim set (likely targets)
Products likely fall inside if they:
- are adenosine derivatives with R1 = —CH2OH
- have R2 = H and R4 = H
- carry a pyrazole-linked substituent at the adenosine 2-position consistent with the claim formula
- use an R3 moiety that is CO2R20, amide (CONR7R8), or aryl (optionally substituted under the aryl rules)
- for method infringement: are administered to humans to provoke coronary steal during imaging.
Likely outside the claim set (structural reasons)
Claim 1 excludes or limits:
- alternative adenosine substitutions at positions corresponding to R2 and R4 (both are fixed to hydrogen)
- aryl substitution patterns beyond the allowed count and substituent sets
- amide substitution if R7/R8 are outside allowed sets (e.g., R8 not H or C1-8 alkyl).
US patent landscape: where this claim sits relative to typical competing IP
US 6,403,567’s landscape posture is best read by its structure and use language.
1) Likely “core compound” family coverage
A patent that:
- locks the adenosine core substitution pattern (R1/R2/R4),
- then varies pyrazole-linked group chemistry (R3),
- and enumerates representative examples (claim 7),
typically functions as a compound family claim rather than a mere discovery of a known agent.
2) Likely “clinical use” differentiation
The method claim is not simply “vasodilation” or “cardiac imaging,” but explicitly:
- imaging-driven coronary steal,
- heart stress requirement,
- human administration.
That language tends to carve a narrower operational space than broad vasodilator claims.
3) How later entrants might design around
Potential design-arounds usually focus on one of three pressure points:
- chemical scope: alter substitutions such that R3/R7/R8/R20 fall outside,
- core scaffold: change fixed adenosine positions (the R2/R4 hydrogen requirement is a common target),
- method: avoid the “coronary steal situation for the purposes of imaging the heart” framing, or change clinical protocol such that the physiological effect and purpose do not align with claim language.
Claim chart view: key infringement gates
For product and method exposure, the gate conditions in US 6,403,567 are concentrated.
Compound gate (claim 1)
A product must meet the full set:
- fixed adenosine core: R1 = —CH2OH; R2 = H; R4 = H
- R3 type and substitution limits: CO2R20, CONR7R8, or aryl with 1 to 2 substituents from defined sets
- amide/aryl limits: R7 and R8 allowed sets
- ester/alkoxy limits: R20 = H or C1-8 alkyl
Method gate (claim 11)
A clinical protocol must match:
- administer a claim 1 compound
- stimulate coronary vasodilation
- “stress the heart”
- induce “coronary steal situation”
- “for purposes of imaging the heart”
- in humans (claim 13)
What is the practical scope of enforcement: where it is strongest
Enforcement strength is highest where:
- the same compound appears in marketed or trial regimens and the protocol is explicitly coronary steal imaging,
- formulation is a “solution” product that uses a claim 1 compound (composition claim 10),
- the compound is one of the named analogs in claim 7 or the narrowed methylamide subset in claim 8.
Key Takeaways
- US 6,403,567 is built on a fixed adenosine core (R1 = —CH2OH; R2 and R4 = H) with Markush variation centered on a pyrazole-linked substituent (R3) and amide N-substitution (R7/R8), plus ester-like R20.
- The patent’s chemical breadth is meaningful (CO2R20, amide, and aryl options with enumerated substituent limits), but the core scaffold constraints are tight.
- Coverage includes both compound (claim 1), pharmaceutical composition (claim 9-10), and imaging method (claim 11-13).
- The method claims are operationally narrow: they require coronary steal under heart stress conditions for imaging in a human patient population.
FAQs
1) Does the claim cover any adenosine derivative?
No. Claim 1 fixes key positions: R1 must be —CH2OH and R2 and R4 must be hydrogen. Altering those positions is outside claim coverage.
2) Are aryl-substituted variants covered broadly?
Claim 1 covers R3 aryl with optional substitution of 1 to 2 substituents chosen from a defined set (halo, C1-6 alkyl, CF3, OR20). Dependent claims further reduce aryl substitution count.
3) Does the patent cover amide analogs with variable N-substitution?
Yes. Through R3 = —CONR7R8, claim 1 allows R7 to be H, C1-8 alkyl, or aryl (with additional substitution constraints) and R8 to be H or C1-8 alkyl. Dependent claims narrow these ranges.
4) What is required to infringe the method claim?
A human imaging protocol must use a claim 1 compound in an amount sufficient to “stress the heart” and induce a “coronary steal situation” for imaging.
5) What does the composition claim add over the compound claim?
Claims 9-10 cover pharmaceutical compositions containing a claim 1 compound, including solution formulations. Compound-only manufacture and direct use may still trigger method claims, but formulation adds an additional enforcement lane.
- United States Patent 6,403,567 (publication and claim text as provided).
