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Patent landscape, scope, and claims: |
United States Patent 6,949,535 (US 6,949,535): scope, claim strength, and US patent landscape for PI3K-delta leukocyte pathway inhibitors
US 6,949,535 is a composition-free, structure-defined patent that claims broad methods of disrupting leukocyte function and inhibiting phosphatidylinositol 3-kinase delta (PI3Kδ) by contacting leukocytes or a PI3Kδ polypeptide with a large chemical genus. The independent claim set also includes compound genus coverage, with dependent claims narrowing to specific quinazolinone-derivatives linked to substituted purines via methylene or sulfanylmethylene linkers. The practical enforceability hinges on whether accused products fall within the structural “A/X/Y/R1/R2/R3/Rb/Rc/Het” claim grammar and the “pharmaceutically acceptable salts or solvates” qualifier.
At a high level
- Claim type mix: method-of-treatment/disruption (leukocytes), method-of-inhibition (PI3Kδ polypeptide), and direct compound genus (general structural formula).
- Core target: PI3K delta activity in leukocytes.
- Core chemistry motif: substituted quinazolin-4-one (quinazolinone) scaffold coupled to a purine (aminopurine or purine) and an aromatic group (e.g., chlorophenyl, tolyl, substituted phenyl) with a flexible, highly variable R-group substitution pattern.
- Claim breadth: extremely broad on paper due to extensive Markush groupings (A ring system, X, Y, R1/R2/R3, and Het/Rb/Rc), while the dependent claims identify many concrete examples.
What patents protect US 6,949,535 “leukocyte disruption” and PI3K-delta inhibition by contacting cells with a substituted quinazolinone-purine compound?
US 6,949,535’s protection is built around contacting as the operative act and structure-defined compounds as the contact agent. It is not limited to a formulation, dose, route, indication, or specific leukocyte subtype. The patent language includes:
- A method of disrupting leukocyte function by contacting leukocytes with a compound with the general structure described in claim 1.
- A method of inhibiting kinase activity of a PI3Kδ polypeptide by contacting the polypeptide with the same structural class of compounds (claim 3).
- A compound claim covering the compounds having the general structural formula (claim 4), subject to the same structural constraints (A/X/Y/R1/R2/R3/Rb/Rc/Het variables) and salts/solvates.
How the claim is anchored to PI3Kδ
The claims expressly require:
- “in an amount sufficient to inhibit phosphatidylinositol 3-kinase delta activity in said leukocytes” (claim 1) for the leukocyte method.
- “inhibiting kinase activity of a phosphatidylinositol 3-kinase delta polypeptide” (claim 3) for the polypeptide method.
This anchoring creates two enforceability vectors:
- Direct method infringement where the accused agent is administered or otherwise used to contact leukocytes or PI3Kδ polypeptide with the claimed compound.
- Compound-based infringement exposure where an accused product is the claimed chemical entity or a salt/solvate falling in the genus (claim 4 and dependent narrowing).
What the structural “A/X/Y” grammar covers
Claim 1’s compound class is governed by:
- A: an optionally substituted monocyclic 5-membered heterocycle with 2 or 3 nitrogens, or a bicyclic ring with at least two nitrogens where at least one ring is aromatic.
- X: chosen from C(Rb)2, CH2CHRb, or CH═C(Rb).
- Y: selected from null, S, SO, SO2, NH, O, C(═O), OC(═O), C(═O)O, and NHC(═O)CH2S.
- R1 and R2: independently selected from a very large set including halo, alkyl, aryl/heteroaryl, CF3/OCF3, amines, sulfonamides, carbonyl-containing substituents, and multiple linker-like groups (e.g., alkylene substituted with amide/amine/sulfonamide).
- R3, Rais, Rb, Rc, Het: additional substitution and ring constraints.
Where the structure collapses into recognizable substructures
The dependent claims and examples (claim 2 and claim 15) tightly track a quinazolinone-aminopurine linked system. Many listed compounds in claim 2 include:
- “2-(6-aminopurin-9-ylmethyl)-…-quinazolin-4-one” (and variants with bromo/chloro/fluoro substitution patterns).
- “2-(9H-purin-6-ylsulfanylmethyl)-…-quinazolin-4-one” (sulfanylmethyl linker variants).
- Aromatic substituents on the quinazolinone such as “3-(2-chlorophenyl)…”, “3-(2-fluorophenyl)…”, “3-(o-tolyl)…”, “3-biphenyl…”, “3-(2-methoxyphenyl)…”.
What is the effective claim scope of US 6,949,535 (independent claims 1 and 3) versus the narrower compound claims (4, 5-15)?
Independent claim 1: leukocyte function disruption
Claim 1 scope drivers
- The claim covers any leukocytes without restricting to disease phenotype, immune cell type, activation state, or tissue.
- The operative step is contacting leukocytes with the claimed compound.
- It is limited only by:
- chemical structure class,
- presence of a quantity “sufficient to inhibit PI3Kδ activity.”
Breadth characteristics
- The compound class is a broad genus due to extensive Markush definitions across A/X/Y/R1/R2/R3/Rb/Rc/Het and optional substitutions.
- There is no explicit limit on:
- administration route,
- dosing regimen,
- formulation or excipient,
- therapeutic indication,
- whether inhibition is measured ex vivo or in vivo.
Independent claim 3: PI3Kδ polypeptide inhibition
Claim 3 scope drivers
- Covers “contacting” a PI3Kδ polypeptide with the claimed compounds.
- Does not require leukocyte context in the same way claim 1 does.
Breadth characteristics
- This expands infringement scenarios to:
- in vitro kinase inhibition assays using PI3Kδ polypeptide preparations,
- industrial screening and reagent use where the claimed compound class is used to inhibit PI3Kδ activity.
Independent claim 4: compound genus
Claim 4 scope drivers
- Directly claims compounds with the general structural formula plus salts/solvates.
- It uses the same core A/X/Y/R1/R2/R3/Rd/Rb/Rc/Het definitions, including special provisos.
Key provisos that can narrow/shape claim construction
The text includes a proviso: if X—Y is CH2S, then R3 constraints exclude “—CH2CH(OH)CH2OH substituted phenyl.” This carve-out functions as a claim scope limiter for that specific subcombination.
Dependent claims 5-14: systematic narrowing levers
Dependent claims progressively fix:
- the X definition (claim 5),
- the Y definition (claim 6),
- the A ring system identity and substitution count (claims 7-9),
- and specific parameter sets for R1/R2 and R3 substituent options (claims 10-14).
Even so, claims 10-14 still remain broad because the dependent lists retain huge Markush sets (e.g., “aryl,” “heteroaryl,” “C1-6alkyl,” carbonyl derivatives, sulfonamides, etc.). The narrowing is often more about allowed chemistry families than about eliminating the genus.
Dependent claim 15: concrete example set
Claim 15 enumerates specific compounds (a closed list) that fall within the broader genus. Examples include:
- 2-(6-aminopurin-9ylmethyl)-3-(2-benzyloxyphenyl)-5-methyl-3H-quinazolin-4-one
- 2-(6-aminopurin-9-ylmethyl)-3-(2-hydroxyphenyl)-5-methyl-3H-quinazolin-4-one
- 2-(1-(2-amino-9H-purin-6-ylamino)ethyl)-5-methyl-3-o-tolyl-3H-quinazolin-4-one
- 5-methyl-2-[1-(9H-purin-6-ylamino)propyl]-3-o-tolyl-3H-quinazolin-4-one
- 2-(2-benzyloxy-1-(9H-purin-6-ylamino)ethyl)-5-methyl-3-o-tolyl-3H-quinazolin-4-one
- 2-(6-aminopurin-9-ylmethyl)-5-methyl-3-{2-(2-(1-methylpyrrolidin-2-yl)-ethoxy)-phenyl}-3H-quinazolin-4-one
- 2-(6-aminopurin-9-ylmethyl)-5-methyl-3-(2-(3-dimethylaminopropoxy)-phenyl)-3H-quinazolin-4-one
- 2-(6-aminopurin-9-ylmethyl)-5-methyl-3-(2-prop-2-ynyloxyphenyl)-3H-quinazolin-4-one
- and a phenoxyacetamide analog: “2-{2-(1-(6-aminopurin-9-ylmethyl)-5-methyl-4-oxo-4H-quinazolin-3-yl)-phenoxy}-acetamide.”
For infringement analysis, claim 15 is useful because it provides a high-confidence mapping between:
- the claimed structure space, and
- discrete compounds that an accused manufacturer might actually sell or market as intermediates or actives.
How many “likely infringing” compound families does US 6,949,535 cover (quinazolinone-purine PI3Kδ inhibitors)?
Using the dependent-claim enumeration and the claim grammar, the patent space partitions into the following compound families (by linker and aromatic substitution motif):
1) Linker class A: “aminopurinylmethyl” derivatives
- “2-(6-aminopurin-9-ylmethyl)-…” and “2-(6-aminopurin-o-ylmethyl)-…” variants appear repeatedly in claim 2 examples.
- Includes aromatic groups such as 2-chlorophenyl, 2-fluorophenyl, o-tolyl, biphenyl, methoxyphenyl, hydroxyphenyl, benzyloxyphenyl, difluoro/chloro substituted quinazolinones, etc.
2) Linker class B: “purin-6-ylsulfanylmethyl” derivatives
- “2-(9H-purin-6-ylsulfanylmethyl)-…” appears as the alternative linkage series.
- The quinazolinone ring substitution pattern changes across fluoro/chloro/bromo, and aromatic phenyl substitution changes across o-tolyl, 2-fluorophenyl, 2-chlorophenyl, methoxyphenyl, etc.
3) Linker class C: “amino” substituted purine ethyl/propyl linkers
- Multiple examples in claim 2 include purine “ylamino” ethyl and propyl linkers, such as:
- “1-(2-amino-9H-purin-6-ylamino)ethyl”
- “1-(2-fluoro-9H-purin-6-ylamino)propyl”
- “1-(9H-purin-6-ylamino)propyl”
These are mechanistically consistent with PI3Kδ kinase inhibitors targeting ATP-binding sites, but the legal relevance is that they likely remain within the broad genus definitions of R-group linkers.
4) Aromatic substitution class: chlorophenyl, fluorophenyl, tolyl, and extended aryl systems
Examples include:
- 2-chlorophenyl (frequent),
- 2-fluorophenyl,
- o-tolyl,
- biphenyl-2-yl,
- benzyloxyphenyl,
- morpholinyl-ethylamino substituted phenyl,
- and phenoxyacetamide aryl substitutions.
5) Quinazolinone substitution class: halogens and C5 methyl
Across the list, the quinazolinone frequently carries:
- “5-methyl-3H-quinazolin-4-one,”
- or halogen substitution on the quinazolinone core at positions such as 6/7/8.
Bottom line on count: the patent is best treated as covering several dozen specific embodiments within the heteroaryl-linked quinazolinone platform, while the independent claims are broader enough to include substantially more variants that keep the required “A/X/Y” heterocycle grammar and the allowed R-group families.
Which products or actives are plausibly within US 6,949,535’s genus (and what would be the fastest infringement mapping)?
The fastest mapping is to treat the claim as requiring:
- the quinazolinone-like scaffold consistent with the general formula in claim 4,
- the purine/aminopurine substructure connected via methylene, sulfanylmethylene, or ylamino ethyl/propyl linkers,
- the aromatic group at the substituted quinazolinone position,
- and the allowed R-group types in the dependent definitions.
In practice, the highest risk are products whose chemical catalogs show:
- 6-aminopurin-9-ylmethyl or 9H-purin-6-ylsulfanylmethyl linkers attached to a substituted quinazolin-4-one,
- plus “2-(2-chlorophenyl)” / “2-(2-fluorophenyl)” / “o-tolyl” aromatic groups and 5-methyl quinazolinone variants.
Claim 15’s enumerated examples are especially useful for direct infringement screens because they identify discrete chemical entities the patentee expressly contemplated within the genus.
How strong is the patent estate around US 6,949,535 for PI3Kδ inhibitor leukocyte methods (litigation and Orange Book relevance)?
No reliable litigation, Orange Book listings, or estate-extension data is included in the information provided for US 6,949,535. The only defensible strength conclusions drawn from the claim text itself are:
- Claim clarity for infringement mapping: the structural Markush definitions are extensive but written in a way that can be algorithmically checked against a chemical structure (use of A/X/Y, and explicit R-group classes).
- Multiple claim pathways: method (leukocytes), method (PI3Kδ polypeptide), and composition (compound formula) provide alternative infringement theories.
- Dependent claim exemplification: claim 2 and claim 15 list many specific compounds, which tends to anchor the genus to concrete embodiments.
Enforcement strength in court still depends on claim construction, prior art, and whether an accused compound literally meets or design-aroundes the defined A/X/Y/R groups, which is not determinable from the claim text alone.
When does US 6,949,535 lose exclusivity, and what launch risk exists for generic or biosimilar entrants?
A loss-of-exclusivity timetable (including expiration date, term adjustments, and patent family continuation impacts) cannot be derived from the text provided. No filing/priority/issue/maintenance data is included, and no extension data is given.
For risk analysis without those facts, the only robust statement is:
- The patent covers small-molecule PI3Kδ inhibitors by structure, so “generic entry risk” is tied to whether an ANDA competitor’s active falls within the claimed genus (or whether a design-around avoids key R-group combinations), and not to biologic pathways.
Key takeaways
- US 6,949,535 is a structurally defined PI3Kδ inhibitor patent with three independent claim themes: leukocyte disruption (contacting leukocytes), PI3Kδ polypeptide inhibition (contacting polypeptide), and direct compound genus coverage.
- Independent claims are very broad due to extensive Markush structures across A/X/Y and R-group substitution space, but are constrained by the need to “inhibit PI3Kδ activity” and the specific chemical grammar.
- Dependent claims narrow along specific chemical toggles (X/Y identity, A-ring substitution count and allowed substituents, and defined option sets for R1/R2/R3).
- Claim 2 and claim 15 provide concrete embodiment lists that are valuable for rapid infringement screening and for understanding the practical scope intended by the patentee.
- Enforceability and design-around feasibility turn on whether a competing active (or its salts/solvates) literally fits the A/X/Y and substitution definitions; the “contacting” limitation creates multiple possible method-infringement fact patterns.
FAQs
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Does US 6,949,535 require in vivo administration to infringe the leukocyte method claim?
It requires “contacting leukocytes” with an amount sufficient to inhibit PI3Kδ activity; the claim text does not specify route or in vivo versus ex vivo conditions.
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Can a kinase inhibition assay involving a PI3Kδ polypeptide implicate US 6,949,535 claim 3?
Claim 3 covers contacting a PI3Kδ polypeptide with the claimed compounds; assay contact conditions can fall within the claim’s “contacting polypeptide” framing.
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How do the “X—Y is CH2S” provisos in claim 4 affect design-around strategies?
They impose conditional restrictions on the allowed R3 when X and Y combine as CH2S, excluding at least one “CH2CH(OH)CH2OH substituted phenyl” configuration.
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Are salts and solvates covered by US 6,949,535 even if the free base differs?
Yes. The claims include “pharmaceutically acceptable salts or solvates” of the defined compounds.
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Which claim is more important for compound infringement: claim 4 or the method claims (1 and 3)?
Claim 4 is the direct chemical coverage; method claims 1 and 3 add route- and use-context requirements around contacting leukocytes or PI3Kδ polypeptide with the structure-defined compound in sufficient quantity.
References (APA)
- US Patent 6,949,535. (n.d.). Method of disrupting leukocyte function and compounds for inhibiting PI3K delta activity. United States Patent and Trademark Office.
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