United States Patent 8,551,995 (Drug) - Scope, Claims, and US Patent Landscape
US Drug Patent 8,551,995 claims a broad genus of substituted heteroaryl-alkyl/piperazine or related amide/amine derivatives defined by Formula (II) with wide structural latitude on aryl/heteroaryl substituents and allowed heteroatom substitution patterns. The independent claim is a Markush-style compound claim with extensive parameterized substitution ranges, followed by dependent claims that narrow to specific sub-formulas and a set of explicit exemplified compounds.
What is the claim architecture in US 8,551,995?
Claim 1: broad genus on “compound of Formula II”
Claim 1 is a compound claim covering:
- A compound of Formula (II) or a salt thereof
- Substitution variables include:
- R1: arylalkyl or heteroarylalkyl, optionally substituted with 1 to 4 Z1
- R2: aryl (C6-C14), heteroaryl (5-12 membered), heterocyclyl (3-15 membered) or amide, optionally substituted with 1 to 4 independent Z2
- R3: H, hydroxyl, alkoxy, or alkylamino
- R5: NH2 (fixed)
- Z1 and Z2: independently selected from a long list including halogens, CN, nitro, OR15, SR15, sulfonates, amide/urea-like carbonyl substituents, perfluoroalkyl/perfluoroalkoxy, methylenedioxy, and other carbonyl-containing groups
- n: independently 0-6 in certain substituent options
- R15, R16, R17: additional latitude on substituent identities (alkyl/aryl/heteroaryl/cycloalkyl/alkenyl/alkynyl classes, and substituted variants)
Practical read-through: Claim 1 is designed to control a core scaffold while leaving multiple “rings” and “handles” (arylalkyl/heteroarylalkyl on one side, heteroaryl/heterocycle or amide on the other side, with an amino group fixed as R5 = NH2) and with extensive options for electronegative and polar substituents via Z1/Z2 and the R15/R16/R17 families.
Claim 2: dependent narrowing to “Formula (IIa)”
Claim 2 narrows Claim 1 to a sub-class defined by Formula (IIa).
Claim 3: dependent narrowing via R6 and R7 cyclization
Claim 3 introduces a specific arrangement:
- R6 and R7 independently H, optionally substituted C1-C4 alkyl, C6-C14 aryl, 5-12 membered heteroaryl, 3-15 membered heterocyclyl
- R6 and R7 together with the nitrogen they attach to form an optionally substituted 3-15 membered heterocycle with 0-3 additional heteroatoms
This is a common tightening strategy: it converts variable substituents into a closed ring system.
Claims 4 and 5: functional narrowing
- Claim 4: R3 is H
- Claim 5: R2 is 3-15 membered heterocycle optionally substituted with 1-4 Z2
Claim 6: explicit compound list
Claim 6 recites a set of specific chemical entities (multiple members) that fall within the genus parameters. These are not merely “representative”; they are stated as claim-covering species under the dependent claim.
The list includes compounds with the repeated motifs:
- 6-amino-5-(substituted ethoxy)-pyridazine / pyrimidinyl-pyridazinyl systems
- Substitution involving (2,6-dichloro-3-fluoro-phenyl)-ethyl/ethoxy features
- Additional substituents such as piperazinyl, morpholinyl, piperidinyl, pyrazolyl, benzamide, carboxamide linkages, and aryl-piperazine variants
What does the Z1/Z2 substitution scope actually cover?
Z1 and Z2 are broadly defined electrophile/polar groups
Z1 and Z2 are independently selected from:
- Halogen
- CN
- NO2
- OR15, SR15
- S(O)2OR15
- NR15R16
- C1-C2 perfluoroalkyl
- C1-C2 perfluoroalkoxy
- 1,2-methylenedioxy
- Carbonyl-related substituents:
- C(O)OR15
- C(O)NR15R16
- OC(O)NR15R16
- NR15C(O)NR15R16 (multiple urea/carbamoyl patterns)
- C(NR16)NR15R16
- NR15C(NR15R16)NR15R16
- Sulfur oxidation states and sulfonamides:
- Additional placeholders:
- R17
- C(O)R17
- NR15S(O)2R17
- S(O)R17
- S(O)2R17
- R16, oxo, C(O)R16, C(O)(CH2)nOH, (CH2)nOR15, (CH2)nC(O)NR15R16
- With n = 0 to 6
Impact on landscape: Competitors designing around this patent cannot rely on avoiding halogens or nitro alone. The permitted list includes multiple polar and hydrogen-bond capable groups plus heavily fluorinated and sulfonyl motifs, creating a larger “design space” inside the claim boundaries.
Where is the claim “center of mass” (core chemical identity)?
Across Claim 1’s parameterization and Claim 6’s enumerated species, the repeatedly appearing scaffold elements are:
-
A pyridazinyl (and related azine) core bearing:
- a fixed amino substituent (R5 = NH2)
- an ethoxy/alkoxy linkage to a (2,6-dichloro-3-fluoro-phenyl)-containing aryl segment
- additional ring substitution patterns involving phenyl/heteroaryl attachment or amide/carbamoyl motifs
-
Downstream, Claim 6 species show three major substitution “handles” that map into Claim 1’s variables:
- Amide/benzamide linkages to substituted anilines/heteroaryl amines
- Piperazine-type substitutions (N-methylpiperazine; morpholine-adducts; substituted piperazines)
- Pyrazolyl or heteroaryl amines appended to the azine system
What is explicitly covered by Claim 6 (enumerated compounds)?
Claim 6 lists the following compound names (verbatim as provided). These define concrete species within the claimed genus:
- 4-{6-Amino-5-[1-(2,6-dichloro-3-fluoro-phenyl)-ethoxy]-pyridazin-3-yl}-phenyl)-morpholin-4-yl-methanone
- (4-{6-Amino-5-[1-(2,6-dichloro-3-fluoro-phenyl)-ethoxy]-pyridazin-3-yl}-phenyl)-(4-methyl-piperazin-1-yl)-methanone
- (4-{6-Amino-5-[1-(2,6-dichloro-3-fluoro-phenyl)-ethoxy]-pyridazin-3-yl}-phenyl)-piperazin-1-yl-methanone
- 4-{6-Amino-5-[1-(2,6-dichloro-3-fluoro-phenyl)-ethoxy]-pyridazin-3-yl}-N-(2-diethylamino-ethyl)-benzamide
- 4-{6-Amino-5-[1-(2,6-dichloro-3-fluoro-phenyl)-ethoxy]-pyridazin-3-yl}-N,N-dimethyl-benzamide
- (4-{6-Amino-5-[1-(2,6-dichloro-3-fluoro-phenyl)-ethoxy]-pyridazin-3-yl}-phenyl)-(4-morpholin-4-yl-piperidin-1-yl)-methanone
- 4-[1-(2,6-Dichloro-3-fluoro-phenyl)ethoxy]-6-pyrimidin-5-yl-pyridazin-3-ylamine
- 4-[1-(2,6-Dichloro-3-fluoro-phenyl)-ethoxy]-6-[1-(tetrahydro-pyran-4-yl)-1H-pyrazol-4-yl]-pyridazin-3-ylamine
- 4-[1-(2,6-Dichloro-3-fluoro-phenyl)-ethoxy]-6-(1-piperidin-4-yl-1H-pyrazol-4-yl)-pyridazin-3-ylamine
- 4-[1-(2,6-Dichloro-3-fluoro-phenyl)-ethoxy]-6-(6-morpholin-4-yl-pyridin-3-yl)-pyridazin-3-ylamine
- 4-[1-(2,6-Dichloro-3-fluoro-phenyl)-ethoxy]-6-[6-(4-methyl-piperazin-1-yl)-pyridin-3-yl]-pyridazin-3-ylamine
- 4-[1-(2,6-Dichloro-3-fluoro-phenyl)-ethoxy]-6-[4-(4-methyl-piperazin-1-yl)-phenyl]-pyridazin-3-ylamine
- 6-Amino-5-[1-(2,6-dichloro-3-fluoro-phenyl)-ethoxy]-pyridazine-3-carboxylic acid pyridin-4-ylamide
- 6-Amino-5-[1-(2,6-dichloro-3-fluoro-phenyl)-ethoxy]-pyridazine-3-carboxylic acid methylamide
- 6-Amino-5-[1-(2,6-dichloro-3-fluoro-phenyl)-ethoxy]-pyridazine-3-carboxylic acid (tetrahydro-pyran-4-yl)-amide
- 6-Amino-5-[1-(2,6-dichloro-3-fluoro-phenyl)-ethoxy]-pyridazine-3-carboxylic acid pyridin-3-ylamide
- 6-Amino-5-[1-(2,6-dichloro-3-fluoro-phenyl)-ethoxy]-pyridazine-3-carboxylic acid pyrimidin-5-ylamide
Strategic effect: Species-level claim coverage locks down specific medicinal chemistry “end games” (benzamide and carboxamide variants; azine-linked amines; piperazine-adducts), while the genus claim keeps pressure on off-by-one modifications that preserve the scaffold.
How does this define risk for competitor design-arounds?
Design-around risk drivers
Competitors face tight constraints because the independent claim:
- Fixes R5 = NH2
- Allows extensive variation for:
- ring choice in R2 (aryl, heteroaryl, heterocycle, amide)
- arylalkyl/heteroarylalkyl in R1 with 1-4 Z1
- substituent classes in Z1/Z2 including polar and fluorinated groups
As a result, many “cosmetic” changes that remove only a single substituent class (for example switching from chloro to fluoro, or removing only a nitro) still likely remain within the Markush set for Z1/Z2.
Primary escape hatches inside the claim text
Only changes that remove one of the fixed or structurally defined components are more likely to exit:
- Removing or changing the amino function corresponding to R5 = NH2
- Changing the scaffold so that the connection pattern no longer maps to Formula (II)
- Moving substituents outside the enumerated classes for R1/R2/R3 or outside the Z1/Z2 list
- Eliminating the possibility that substituents are encompassed by R15/R16/R17 ranges
What is the US patent landscape around 8,551,995?
Landscape coverage limits from the provided record
A complete landscape (family members, continuations, priority chain, related US publications, granted claims in siblings, and citation map) cannot be produced from the claim text alone. The only authoritative US-landscape facts that can be stated from the provided input are the scope mechanics of this patent’s claims and the exact species listed in Claim 6.
Actionable landscape framing (based on claim mechanics)
Even without family-level bibliographic data, the claim set indicates a typical life-cycle structure:
- Genus claim (Claim 1): broad coverage to block many analogs
- Sub-genus claim (Claim 2 and Claim 3): narrower embodiments with specific heterocycle formation
- Further tightening (Claims 4-5): constraints on R3 and R2 type
- Species exemplars (Claim 6): concrete medicinal chemistry structures likely drawn from the patent’s examples
For enforcement and FTO analysis, this means the patent can be asserted at multiple claim levels:
- broadest coverage at Claim 1 where structure matches Formula (II)
- secondary support at sub-genus and specific compound claims if a challenger argues non-coverage or prosecution history estoppel
Competitive implication
Any competitive series that keeps:
- the azinyl amino core (R5 = NH2)
- the substituted ethoxy aryl motif and
- uses one of the enumerated amide/amine/piperazine-adduct patterns
faces higher likelihood of falling within the literal parameter sets of Claim 1 and Claim 6.
Key claim-to-structure mapping table
| Patent element |
Where it appears |
What it controls |
What to watch in competitor structures |
| R5 = NH2 |
Claim 1 |
Fixed amino group location/class within Formula (II) |
Removal or conversion to non-amino (e.g., carbonyl) can change coverage |
| R1 arylalkyl/heteroarylalkyl + Z1 substitutions |
Claim 1 |
Allowed substitution pattern on one substituent “arm” |
Many halogen/polar/fluoro substitutions remain inside Z1 |
| R2 aryl/heteroaryl/heterocycle/amide + Z2 substitutions |
Claim 1; Claim 5 narrows |
Second “arm” ring system and substitution |
Designs using 3-15 membered heterocycles can still map to Claim 5 |
| R3 H/hydroxyl/alkoxy/alkylamino |
Claim 1; Claim 4 narrows to H |
Side-chain functionality |
If R3 must be H for validity, competitor can target non-H analogs, but Claim 1 may still cover them |
| n = 0-6 in certain Z substituents |
Claim 1 |
Chain length allowed for alkylated carbonyl and ether linkages |
Long chain variants up to n=6 remain potential coverage |
| Claim 6 species list |
Claim 6 |
Specific marketed or example-like structures |
Direct hits map to dependent coverage |
Key Takeaways
- US 8,551,995 is built around a Markush-style genus (Claim 1) with fixed amino functionality (R5 = NH2) and wide ring and substituent latitude via R1/R2 and Z1/Z2 parameter sets.
- Dependent claims (2-5) provide incremental tightening (Formula IIa; R6/R7 cyclization; R3 = H; R2 as heterocycle), increasing enforcement options.
- Claim 6 locks coverage on 17 enumerated concrete compounds built on a repeated motif: 6-amino-5-(substituted ethoxy)-pyridazine/azine frameworks coupled to benzamide/carboxamide/amine and piperazine-like substituents.
- For design-around, the claim’s breadth comes from the breadth of Z1/Z2 and R15/R16/R17 sets, not from a narrow single substituent. Avoiding only one functional class is unlikely to be sufficient.
FAQs
1) Does 8,551,995 protect only the explicitly listed compounds in Claim 6?
No. Claim 1 protects a broad genus of Formula (II) compounds and salts; Claim 6 adds specifically enumerated species within that genus.
2) Which feature looks most “fixed” in Claim 1?
The amino group specified as R5 = NH2 is explicitly fixed, while other substituents vary through R1/R2/R3 and Z1/Z2 enumerations.
3) Can competitors escape by changing halogens?
Not reliably. Halogens are included in Z1/Z2, and many other polar and fluorinated groups are also included, so multiple halogen substitutions remain within scope.
4) Is R2 limited to aryl groups?
No. Claim 1 includes aryl, heteroaryl, heterocyclyl, and amide options for R2, and Claim 5 further specifies R2 as a 3-15 membered heterocycle when asserted.
5) What gives claim enforcement leverage besides the genus claim?
Dependent claims provide narrower embodiments and Claim 6 provides specific, concrete structures, enabling enforcement across a spectrum of literal matches.
References
[1] US Patent 8,551,995 (provided claim text and claim list as supplied in the prompt).
