US Patent 8,969,377: Scope, Claim Coverage, and US Landscape for the PEG-Linker Compound Family
US Patent 8,969,377 claims a family of compounds defined by a structured “NHE” moiety and a “Core” scaffold connected through a polyalkylene glycol linker (L), with multiple permissible substitutions on “Y” and specific constraints on R-group variables. Claim 1 is the main structural anchor. Claim 7 adds standard formulation coverage. The claim set is drafted to cover (i) the compounds and their pharmaceutically acceptable salts, (ii) embodiments where L is polyethylene glycol (PEG), and (iii) embodiments where the Core matches enumerated selections (claims 4-6), while leaving open variability in other positions through defined variable sets.
What does Claim 1 actually cover? (Core + NHE + PEG linker + defined Y attachment)
Claim 1 covers:
- A compound (or pharmaceutically acceptable salt)
- Having a specific chemical structure template labeled (X)
- With fixed constraints:
- n = 2
- R3 = hydrogen
- R7 = hydrogen
- With defined variable sets:
- R1 is either:
- H, or
- —SO2—NR7R8
- R2 is one of:
- H
- —NR7(CO)R8
- —SO2—NR7R8
- —NR7R8
- R8 is “a bond linking to L”
- L is a polyalkylene glycol linker (PAG)
- Core is a further scaffold with:
- X chosen from: bond, —O—, —NH—, NHC(═O)—, —NHC(═O)NH—, —NHSO2—
- Y chosen from: bond, optionally substituted C1-6 alkylene, optionally substituted benzene, pyridinyl, a polyethylene glycol linker, —(CH2)1-6O(CH2)1-6
Functional interpretation for freedom-to-operate (FTO)
Claim 1 is not a single exact molecule. It is a combinatorial structure definition with:
- A constrained “NHE” substructure (via R1/R2/R3/R7/R8 rules)
- A constrained linker class (polyalkylene glycol, with a dependent claim specifying PEG)
- A constrained “Core connection” grammar (via X and Y choices)
That drafting style typically yields broad coverage within the defined template while still anchoring novelty to the combination of:
1) the NHE substitution pattern, and
2) a glycol linker connection, and
3) the Core attachment options.
How broad is Claim 1 within the NHE variable space?
The “NHE” definition is the most important moving part. Under Claim 1:
Fixed:
- R3 = H
- R7 = H
- R8 is the attachment point to L
Variable options:
Consequence
Claim 1 permits multiple oxidation-state and substitution patterns at the NHE nitrogen(s), including:
- amine vs amide vs sulfonamide substitution at the R2 position
- optional sulfonamide at R1
- but with R7 fixed to H, which reduces the number of internal N-alkyl permutations compared with an unrestricted R7 variable.
What is the practical scope of L? (polyalkylene glycol)
Claim 1 requires L = polyalkylene glycol linker.
Dependent Claim 3 narrows this to:
- L is a polyethylene glycol linker (PEG).
Implication
In claim construction terms, Claim 1 covers a broader linker class than Claim 3:
- PEG ⊂ polyalkylene glycol (PAG), where PAG can include varied alkylene units beyond ethylene.
For landscape mapping and design-around assessment, Claim 1 is the controlling coverage for linker type, while Claim 3 carves out a more specific subset.
How do Core’s X and Y selections expand or limit coverage?
Within Claim 1, the “Core” portion includes two key selectors:
X selector (connectivity / heteroatom / carbonyl insertion)
X ∈ { bond; —O—; —NH—; NHC(═O)—; —NHC(═O)NH—; —NHSO2— }
This allows:
- direct bond
- ether linkages (O)
- amino linkages (NH)
- amide-type connectivity (NHC(═O)—)
- urea-type connectivity (—NHC(═O)NH—)
- sulfonamide-type connectivity (—NHSO2—)
Y selector (what the “Core attachment substituent” can be)
Y ∈ { bond; optionally substituted C1-6 alkylene; optionally substituted benzene; pyridinyl; polyethylene glycol linker; —(CH2)1-6O(CH2)1-6 }
This gives breadth in:
- aromatic vs heteroaromatic
- short aliphatic linkers
- internal PEG inclusion
- morpholine-like ether segment endpoints (via the —(CH2)1-6O(CH2)1-6 motif)
Practical scope effect
Claim 1 is broad across “Core” connectivity and substitution points while maintaining definitional constraints:
- X is limited to six specific bond/atom patterns
- Y is limited to six specific fragment classes
That structure grammar is typically enforceable by element-by-element comparison for literal infringement, while doctrine-of-equivalents disputes often turn on whether alternate linkers/bonds are insubstantially different from one of the enumerated classes.
What do Claims 2-6 add beyond Claim 1?
Your claim excerpt provides Claim 2-6 headings but omits the actual structural drawings/enumerations for Claims 2, 4, and 5. Still, the claim text indicates they are refinement claims.
Claim 2
- Claim 1 plus: “NHE has one of the following structures” (enumerated)
Scope effect: Claim 2 is a narrower subset of Claim 1 focused on specific NHE embodiments.
Claim 3
- L is a polyethylene glycol linker (PEG)
Scope effect: Claim 3 is a subset of Claim 1 focused on PEG specifically.
Claim 4
- Claim 1 plus: “Core is selected from the group consisting of” (enumerated)
Scope effect: Claim 4 limits Core to enumerated choices, likely matching specific X/Y combinations or specific Core sub-structures.
Claim 5
- Claim 1 plus: compound is selected from a group consisting of (enumerated compounds)
Scope effect: Claim 5 likely captures a named list of specific exemplified molecules or specific members of the formula.
Claim 6
- “pharmaceutically acceptable salt of claim 1 is selected from” (enumerated salts)
Scope effect: Claim 6 narrows to defined salt types.
What does Claim 7 cover? (formulation)
Claim 7:
- “A pharmaceutical composition comprising:
- a compound of claim 1 (or salt),
- and a pharmaceutically acceptable carrier, diluent or excipient.”
Scope effect
Claim 7 is standard composition-of-matter coverage. It does not materially expand chemical scope beyond Claim 1, but it can provide additional enforceability against formulation products using the claimed compound(s).
What is the likely claim “center of gravity” for infringement analysis?
Across the claim set, infringement analysis will typically focus on whether the accused compound matches:
-
NHE substitution rules
- R7 = H
- R3 = H
- R8 links to L
- R1 and R2 fall within the listed sets
-
Linker identity
- L is polyalkylene glycol (Claim 1)
- L is PEG specifically (Claim 3)
-
Core connectivity grammar
- X ∈ {bond, O, NH, amide-like, urea-like, sulfonamide-like}
- Y ∈ {bond, optional C1-6 alkylene, optionally substituted benzene, pyridinyl, PEG linker, —(CH2)1-6O(CH2)1-6}
If an accused compound uses a linker that is not a polyalkylene glycol, or it uses a non-enumerated bond/connectivity at the “Core X” site, Claim 1 literal coverage becomes difficult.
How to read the patent landscape risk from this claim structure (US-focused)
Because Claim 1 is formula-defined, landscape risk in the US typically falls into three buckets:
1) “Same scaffold, same PEG-linker class, same NHE rules”
If another applicant developed the same or very similar compound family with:
- PEG/PAG linker,
- same NHE rules (especially R7 = H and the R1/R2 option sets),
- and Core X/Y in enumerated sets,
risk of literal overlap is high.
2) “Different linker, same core”
If L is replaced with:
- non-glycol linkers (e.g., hydrocarbon chains),
- non-polyalkylene glycol linkers,
then Claim 1’s linker gate may avoid literal infringement, but formulation claim 7 still tracks the same claimed compound. That means no enforceable formulation claim applies unless the active matches Claim 1.
3) “Same linker, different Core connectivity”
If Core uses a bond pattern not in the X selector set (for example, a different carbonyl placement, different heteroatom, or different sulfone/sulfonamide arrangement), literal coverage can collapse quickly because the “X” selector is enumerated and not described as “any linkage.”
What is known from the information provided about validity and enforcement posture?
Your prompt provides only the claim text, not:
- prosecution history,
- claim construction history,
- cited prior art,
- patent family members,
- assignee and priority dates,
- expiration or adjustment status.
Given the operating constraints, no landscape inference about validity, term, or citation patterns can be made from claims alone.
Accordingly, the only defensible landscape read is structural: the claims define a particular chemical grammar that competitors must match (or intentionally avoid) at the element level.
Key takeaways
- Claim 1 is the broadest chemical claim and defines a structured compound family by fixed variables (n = 2, R3 = H, R7 = H) and enumerated variable sets for R1, R2, Core X/Y, and L (polyalkylene glycol).
- Claim 3 narrows linker identity to PEG, so Claim 1 covers broader PAG linkers while Claim 3 captures PEG-specific members.
- Core coverage is grammar-based: infringement turns on whether the accused compound matches the enumerated Core X (bond/ether/amino/amide/urea/sulfonamide types) and Core Y fragment classes.
- Claim 7 covers formulations only to the extent they use a compound within Claim 1 (or its salts).
- Landscape risk in the US will track whether competitors design around L class and the enumerated Core X/Y selections rather than only matching generic “PEG-linker” concepts.
FAQs
1) Is Claim 1 a single compound or a family?
It is a family defined by a structural template with enumerated options for R1, R2, Core X/Y, and L as polyalkylene glycol.
2) Does Claim 1 require polyethylene glycol specifically?
No. Claim 1 requires polyalkylene glycol in general; PEG is explicitly required only in Claim 3.
3) Which variables are fixed in Claim 1?
n = 2, R3 = hydrogen, and R7 = hydrogen.
4) Can competitors avoid infringement by changing the linker?
Changing L from polyalkylene glycol to a non-PAG linker can remove literal coverage under Claim 1; Claim 7 then also typically falls away because it requires a Claim 1 compound.
5) What does Claim 7 add beyond the compound claims?
It adds pharmaceutical composition coverage using a Claim 1 compound or salt with standard carriers/diluents/excipients.
References
[1] US Patent 8,969,377 (claim text provided in prompt).
