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Patent landscape, scope, and claims: |
United States Patent 6,391,874: Scope, Claim Coverage, and US Patent Estate Analysis for Formula (I) Quinazoline/Quinoline Kinase Inhibitors
US Patent 6,391,874 is a broad, scaffold-and-variable-definition patent that claims large classes of substituted quinazoline/quinoline-based small-molecule compounds (formula (I)), plus salts/solvates, pharmaceutical formulations, and protein tyrosine kinase treatment methods tied to EGFR (c-erb-B1), HER2 (c-erb-B2), and HER4 (c-erb-B4). The claim language is driven by (1) expansive Markush-style variable definitions for substituents and ring systems, (2) multiple fallback dependent claims that narrow to specific heterocycles and R3/R6 groups, and (3) method-of-use claims that focus on aberrant protein tyrosine kinase activity across EGFR/HER family members.
Given the claim’s “variable-of-variables” structure, the practical enforceable scope is strongest for compounds that match the core quinazoline/quinoline ring system and the allowed linkage pattern plus at least one of the covered substitution families for R1, R3, R2, X, Y, and U/R6.
What patents protect compounds of US 6,391,874 formula (I) claims, and what is actually covered?
Bottom line: Claim 1 broadly covers compounds that fit formula (I) where key structural elements are limited to specific types (X, Y, R1, R2, U, R4/R6) while many substituents are defined with wide combinatorial permutations.
Claim 1 building blocks (coverage map)
Claim 1 is structurally a layered Markush system:
1) Core scaffold: quinazoline/quinoline context
- The claim text states “C-linked to the quinazoline or quinoline ring” when R1 contains only N heteroatoms.
- That means enforceable coverage is centered on compounds that include a quinazoline/quinoline bicyclic heteroaromatic core and a specific connectivity to the R1 moiety.
2) X and Y: central heteroatom and linker variability
- X is N or CH.
- Y is a variable group that can be:
- W(CH2), (CH2)W, or W, where W is O, S(O)m (m = 0–2), or NRa (Ra = H or C1-8 alkyl).
This makes the patent sensitive to whether the claimed compound uses:
- an anilide-like ether/amide proxy or
- an (O/S(O)m/N-alkyl) substituted methylene/alkylene linker consistent with the Y definition.
3) R1: a 5- or 6-membered heterocycle with constraints
- R1 is a 5- or 6-membered heterocyclic ring with 1 to 4 heteroatoms selected from N, O, or S(O)m.
- Constraints:
- The ring must not have two adjacent O or S(O)m atoms.
- If the ring has only N heteroatoms, it is C-linked to the quinazoline/quinoline ring.
R1 is therefore a major determinant of infringement. Compounds with adjacent oxy/sulfoxyl patterns in the ring can fall outside.
4) R2: simple allowed substituents
- R2 ∈ {H, halogen, trifluoromethyl, C1-4 alkyl, C1-4 alkoxy}.
This is narrower than it looks but still covers common medicinal substitutions.
5) U and R6: additional ring system and substituent geography
- U is phenyl or a 5–10 membered mono/bicyclic ring system with heteroatoms (N/O/S(O)m), substituted by at least one R6 group and optionally R4 groups.
- R4 is {H, hydroxy, halogen, C1-4 alkyl, C1-4 alkoxy, alkylamino families, alkylthio, alkylsulphinyl/sulphonyl, alkylcarbonyl/carbamoyl/alkoxycarbonyl, cyano, nitro, trifluoromethyl}.
- R6 is complex: Z R7 where Z attaches to R7 through (CH2)p (p = 0–2) and Z can be multiple substituted forms (including fluorinated CF2-containing connectors). R7 is an optionally substituted C3-6 cycloalkyl or other substituted moiety.
This is where claim coverage expands to many “tail” chemistries, but only if the tail architecture matches the defined R6/Z/R7 relationship.
6) R3: very broad, but with a “two-stage” definition
R3 is defined in claim 1 as one of two major categories:
- Large set of substituent names (amino/halogen/hydroxy/cyano/trifluoromethyl and extensive alkyl/aryl/heterocycle amino/oxy/thio/sulfonyl families, plus heterocyclic substituent options with optional halogen and oxo/thioxo patterns).
- Or a more structured “M1–M2–M3–M4” / “M1–M5” / “M1–M2–M3′–M6” pattern covering amino acid-like, sulfonamide-like, nitrile/ester-like groups, and cyclic heterocycle R-substituted ends.
The effect is that R3 can represent:
- simple atom substituents (halo, CF3, hydroxy, etc.)
- bulky functional groups (sulfonamides, ureas, guanidino-like structures)
- or more scaffold-like substituents via M1–M6 constructs.
Also noted:
- If two adjacent R3 groups occur (p=2 or 3), they can form a methylenedioxy/ethylenedioxy group.
Claim 1 “out-of-family” flags
For avoidance / non-infringement analysis, the claim includes explicit structural exclusions:
- R1 cannot contain two adjacent O or S(O)m atoms.
- Some ring linkage/connectivity requirements apply if R1 is N-only heterocyclic.
How do dependent claims narrow the scope in US 6,391,874?
The dependent claims are not merely tightening generic terms. They add:
- specific R3 sub-families,
- specific X/Y selections,
- specific R1 heterocycle selections,
- specific R6 and U selections,
- and multiple enumerated compound examples (claim 26-27) that operationalize the breadth.
Claim 2: R3 restricted to oxo/thioxo-bearing heterocycle and excludes certain sulfoxide/sulfone-alkyl constructions
- Removes some broad allowances:
- Excludes heterocycle substituents without oxo/thioxo.
- Excludes C1-4 alkylsulphinyl-C1-4 alkyl and C1-4 alkylsulphonyl-C1-4 alkyl.
- Explicitly includes certain R3 groups: 4-pyridon-1-yl, 4-pyridon-1-yl-C1-4 alkyl, 4-pyridon-1-yl-C2-4 alkoxy, 4-pyridon-1-yl-C2-4 alkylamino, 2-oxopyrrolidin-1-yl, 2,5-dioxopyrrolidin-1-yl.
Claims 3–5: X and Y and a tighter R1 substitution set
- Claim 3: X = N.
- Claim 4: Y = NRb, NRb(CH2), or (CH2)NRb.
- Claim 5: R1 is a 5–6 member heterocycle substituted by limited substituents (amino/hydrogen/halogen/hydroxy/hydroxy-alkyl/formyl/carboxy/cyano/nitro/C1-8 alkyl/C1-8 alkoxy, etc., and restricted ring substituent classes like dioxolanyl and hydroxy-alkanoyl-amino).
Claims 6–7: R1 substitution limited to selected R3 categories (including alkyl and sulfinyl/sulfonyl tails)
- Claim 6: R3 ∈ {C1-4alkyl, C1-4 alkylamino-C1-4 alkyl, di(C1-4 alkyl)amino-C1-4 alkyl, formyl, carboxy, C1-4 alkoxycarbonyl, dioxolanyl, CF3}.
- Claim 7: R3 restricted to C1-4 alkylsulphinyl-C1-4 alkyl or C1-4 alkylsulphonyl-C1-4 alkyl.
Claim 8–9: p=0 and specific R3 substituent shapes
- Claim 8: p=0 and R3 selected from certain M-type patterns.
- Claim 9: R3 is selected from piperidonyl-methyl, pyrrolidinonyl-methyl, dioxoimidazolidinyl-methyl.
Claims 10–15: deeper narrowing into M2–M4 and M5/M6 constructs
- Claim 10: fixes M1, M2, M3, M3′, M4, M5, M6 definitions.
- Claim 11–12: M2–M3–M4 mapped to amino acid or sulphinic/sulphonic acid and specific ester/amides.
- Claim 13–14: M1–M5 mapped to piperazinyl-methyl, piperidinyl-methyl, pyridylmethyl, prolinamidomethyl, and specific cyclic lactam-like groups.
- Claim 15: M2–M3′–M6 mapped to pyridylamino and several amine side chains; highlights “preferably a pyridylamino group.”
Claims 16–21 and 22: R1 and U and R6 restriction to enumerated moieties
- Claim 16: R1 ∈ {furan, dihydrofuran, thiophene, imidazole, tetrazole, triazole, pyridine, pyrrole, pyrimidine, isoxazole, oxadiazole}.
- Claim 17: R1 is an oxadiazolidinone ring.
- Claim 19: R6 ∈ {benzyl, fluorobenzyl, difluorobenzyl, benzyloxy, fluorobenzyloxy, pyridylmethyl, phenyl, benzenesulphonyl, phenoxy, fluorophenoxy}.
- Claim 20–21: U ∈ {phenyl, indolyl, isoindolyl, …, benzotriazolyl}; narrowed examples for U = phenyl or 1H-indazolyl.
- Claim 22: optional substituents set for carbocyclic/heterocyclic moieties.
Claims 23–25: full “compressed” claim sets for specific parameter choices
These claims read like sub-platforms:
- X = N
- Y = NRa (Ra = H or C1-4 alkyl)
- p = 0
- R2 = H
- R4 = H/halo/methyl
- U = phenyl/indolyl/benzimidazolyl/indazolyl
- R6 limited to specific aryl/benzyl/phenoxy families
Claim 24 further restricts R3 to a very long list of specific aminoalkyl and sulfonyl-containing moieties.
Claim 25 further restricts R4 to H/halo and U to phenyl/indazolyl and R6 to a narrower list.
Claims 26–27: enumerated compounds (implementation list)
Claims 26–27 list specific named compounds and salts. This materially affects infringement analysis because it shows:
- which combinations the drafter considered most important and
- which substitutions likely align with working examples in the specification.
For business teams, these enumerations function as an “infringement anchor set.” A candidate product matching one of the listed structures has the highest likelihood of fitting at least the dependent claim scope.
Claim 28–29: formulation and unit dose
- Claim 28: pharmaceutical formulation comprising compound of claim 1 or salt + carriers/excipients.
- Claim 29: unit dosage form containing 70–700 mg.
This can matter for generic design-around if a competitor markets a product within the unit dose range using a covered active.
Claims 30–32: method-of-treatment and kinase target scope
- Claim 30: administer for disorder mediated by aberrant protein tyrosine kinase activity.
- Claim 31: at least one kinase from c-erb-B2, EGFr, c-erb-B4 shows aberrant activity.
- Claim 32: at least two of the three kinases show aberrant activity.
These claims are not tied to a specific tumor type or patient biomarker beyond the kinase activity panel.
What formulations, salts, and administration doses are protected by US 6,391,874?
Protected subject matter
- Any pharmaceutically acceptable salt or solvate of formula (I) compounds.
- Pharmaceutical formulations using covered compounds.
- Unit dosage formulations at 70 to 700 mg.
Practical risk note for product developers
- The claim set protects “formulation” at a high level (carrier/excipient). Without specificity to release profile or dosage form type, it primarily blocks straightforward repackaging.
- The mg range can create a niche carve-out only if a generic or follow-on product’s unit strength is outside 70–700 mg and can still avoid literal claim coverage.
What therapeutic use scope does US 6,391,874 cover for EGFR/HER2/HER4?
Core therapeutic claim focus
- disorders mediated by aberrant protein tyrosine kinase activity.
- explicit kinase set:
- c-erb-B2 (HER2)
- EGFr (EGFR)
- c-erb-B4 (HER4)
Litigation leverage
- The broad method claims do not require a specific disease label in the claim language. If the asserted method in litigation tracks a clinical use (or labeling claim) consistent with EGFR/HER2/HER4 aberrant activity, the patent can be argued as directly applicable.
Where do generic or biosimilar entry risks show up?
This is a small-molecule patent, so biosimilar concepts are not directly relevant.
Generic entry risk
- Main risk comes from whether an ANDA applicant targets a compound that falls within:
- formula (I) core scaffold and substituent-defined variables, and
- at least one dependent claim set (for tighter parameters), or
- method-of-use label alignment (for carve-outs via labeling).
Design-around levers
- changing X or Y to a non-covered linker/heteroatom pattern,
- choosing an R1 heterocycle that violates adjacency constraint (two adjacent O or S(O)m),
- shifting R2 outside allowed set,
- changing U/R6 connectivity/structure outside ZR7 with the allowed p and V constraints,
- or selecting R3 outside the enumerated / Markush-defined categories.
Because claim 1 is expansive, most design-arounds require meaningful scaffold and connection changes, not just minor substituent edits.
How strong is the patent estate around this US 6,391,874, and what is the likely scope of coverage vs. competitors?
No additional US patent numbers, continuation filings, family members, or related asserted patents are provided in the input. Without those, a credible “estate strength” assessment (counts, expiration sequencing, and overlap with competitor’s known actives) cannot be completed in a way that is complete and accurate.
What can be said from claim text alone
- The claim is broad enough to cover multiple enumerated examples and many “tail” variants.
- Dependent claims provide both tightening fallbacks and explicit example lists.
- Method claims further broaden infringement pathways beyond composition.
Timeline: when does US 6,391,874 lose exclusivity?
The patent expiration date, term adjustments, and any PTA/PTE are not provided in the input. A precise exclusivity timeline cannot be produced from the claim text alone.
Patent estate implications for licensing, litigation, and regulatory strategy
Composition coverage
- Strongest position for a patentee typically occurs when the accused compound matches:
- the quinazoline/quinoline core connectivity requirements,
- the allowed R1 heterocycle constraints,
- and the specific linker and tail chemistry allowed by X/Y and R6.
Formulation and dose coverage
- A challenge to generic product claims can also leverage claim 28–29 if the generic’s unit strength falls inside 70–700 mg and uses the same covered compound/salt.
Method-of-use labeling leverage
- The EGFR/HER2/HER4 kinase aberrant activity language can be used to pressure label alignment in markets where those kinases are targeted.
Key Takeaways
- US 6,391,874 claim 1 covers a large Markush universe of quinazoline/quinoline-based kinase inhibitors, controlled by constrained definitions for X, Y, R1, R2, U, and R6, and a very broad R3 substituent set.
- Dependent claims 2–25 materially narrow subsets and include multiple explicit parameter “profiles” (X=N, p=0, R2=H, and U/R6 restrictions).
- Claims 26–27 enumerate specific compounds, creating high-value infringement “anchor” structures.
- Claims 28–29 cover formulations and 70–700 mg unit dosage products containing the claimed compounds.
- Claims 30–32 cover method-of-treatment for disorders mediated by aberrant EGFR/HER2/HER4 protein tyrosine kinase activity.
FAQs
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What structural element is most important for infringement of US 6,391,874?
The quinazoline/quinoline scaffold connectivity plus the allowed heterocycle definition for R1 and the allowed linker definitions for X and Y.
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Does US 6,391,874 claim only specific example compounds or the entire Markush class?
It claims the entire formula (I) class in claim 1, with dependent claims narrowing subsets and listing specific compounds in claims 26–27.
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Can a generic avoid infringement by changing the dosage form type or excipients?
Claim 28 is broad to carriers/excipients; avoidance requires moving outside the covered composition scope or dosage strength range in claim 29.
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Do the method claims require a specific cancer indication?
The claims are not indication-specific; they require aberrant protein tyrosine kinase activity for EGFR/HER2/HER4 sets.
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What is the biggest “design-around” risk area for competitors?
Tailoring R3 and R6 alone is often insufficient because claim 1 constraints integrate multiple regions (R1 ring heteroatom pattern and X/Y linkage) into a single coverage test.
References (APA)
- United States Patent No. 6,391,874.
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