Scope and Claims Breakdown for U.S. Patent 9,278,995 (Peptide–Disulfide Conjugates): What Is Covered, What It Excludes, and How the Patent Landscape Reads
U.S. Patent 9,278,995 claims a narrow class of short D-amino-acid peptides (8–15 residues, with multiple dependent range locks) that are linked to a conjugating group by a disulfide bond, with fixed residue identities at positions X1 and X3 and X5 and X7 (all D-arginine except X1) and with conditional identity swaps at X2/X4 (D-arginine vs D-alanine). The estate is claim-driven around (1) peptide primary sequence constraints, (2) terminal modifications (Ac at N-terminus and/or amidation at C-terminus), (3) conjugating group identity (cysteine/homocysteine/glutathione/PEGylated cysteine/thiol polypeptides) and conjugating-group acetylation, and (4) homodimer formation.
Because your prompt provides only the claim text for the representative set of dependent and independent claims, the analysis below stays strictly within what can be derived from that claim language.
What is the claim scope of US 9,278,995 for disulfide-linked D-peptide conjugates?
Headline claim coverage (independent-claim core)
The putative independent claim (your claim 1) covers:
- A compound containing:
- A peptide with the sequence format X1-X2-X3-X4-X5-X6-X7
- A conjugating group attached to the X1 residue via a disulfide bond
- Hard sequence constraints
- X1 = D-cysteine
- X3 = D-arginine
- X5 = D-arginine
- X7 = D-arginine
- X2 is D-arginine OR D-alanine
- X4 is D-arginine OR D-alanine
- Conditional pairing rule:
- If X2 is D-arginine, then X4 is D-alanine
- If X2 is D-alanine, then X4 is D-arginine
- X6 is a non-cationic amino acid (this phrase is a key scope limiter)
- Conjugation linkage rule
- “peptide X1 residue is linked to the conjugating group by a disulfide bond”
This creates a combinatorial but still bounded sequence space:
- Positions locked: X1, X3, X5, X7
- Positions partially locked with a strict XOR relation: X2 and X4
- One unconstrained except charge: X6 (non-cationic)
- Conjugating group identity is broad in the independent claim if left to later dependent claims; claim 1 already defines the disulfide linkage requirement and the conjugating group concept.
Practical implication: an accused compound must match the D-configuration at all specified positions, the X2/X4 complementary pattern, and use a disulfide-linked conjugation through D-cysteine at X1.
How do the X2/X4 “conditional” sequence rules narrow or expand infringement risk?
X2/X4 XOR constraint is an enforcement hinge
Claim 1 forces a binary relationship:
- Case A: X2 = D-Arg → X4 = D-Ala
- Case B: X2 = D-Ala → X4 = D-Arg
That means a peptide with D-Arg at both X2 and X4 does not meet claim 1. Likewise a peptide with D-Ala at both X2 and X4 does not meet claim 1.
What this excludes (by logic of the conditional)
- Any sequence with:
- X2 = D-arginine and X4 = D-arginine
- X2 = D-alanine and X4 = D-alanine
is outside the literal scope of claim 1.
What this still includes
- Any mapping where X2 and X4 follow the XOR rule, with X6 being “non-cationic,” and remaining locked residues are D-cysteine at X1 and D-arginines at X3/X5/X7.
This is a classic pattern: the “choice” is allowed but only in a specific complementary orientation, which tends to reduce design-around success for partially similar peptides.
What does “non-cationic amino acid” at X6 do to claim breadth?
Charge-based limiter
X6 is “a non-cationic amino acid.” This language can do two things:
- It prevents obvious substitutions with strongly cationic residues.
- It leaves ambiguity for borderline residues (for example, amino acids that are neutral under assay pH vs protonated elsewhere), but your claim text requires “non-cationic” rather than “non-basic.”
Infringement reading: to fall within claim 1, an accused peptide’s position X6 must be an amino acid whose character is not cationic within the claimed concept. The enforcement posture typically treats this as a factual/technical determination rather than a purely lexical one.
Which dependent claims add terminal modifications (Acylation and amidation) to define narrower subsets?
N-terminus acetylation
- Claim 2: N-terminus acetylated
C-terminus amidation
- Claim 3: N-terminus acetylated AND C-terminus amidated
- Claim 4: C-terminus amidated (without requiring N-terminus acetylation)
How these stack
- If an accused product satisfies claim 1 and also matches Ac at the peptide N-terminus and/or amidation at the peptide C-terminus, it maps into the dependent claim strata.
- A compound lacking these modifications may still fall under claim 1 unless the modification is required by the independent portion (here it is not).
How broad is the conjugating-group scope in US 9,278,995?
Conjugating group identity options
Claim 1 uses a conjugating group broadly, then dependent claims narrow identity:
- Claim 5: conjugating group is acetylated
- Claim 6: conjugating group is cysteine
- Claim 12/13/14/15/16: conjugating group is cysteine in L or D form, with optional acetylation
- Claim 17: conjugating group selected from:
- cysteine
- homocysteine
- glutathione
- pegylated cysteine
- thiol-containing polypeptide
- Claim 21/22/25/26/27/28: layering cysteine identity with optional acetylation
Conjugating group linked via disulfide
The disulfide linkage is a structural requirement that ties directly to the peptide’s X1 = D-cysteine residue: the disulfide forms between the peptide X1 thiol and a thiol group on the conjugating group (the claim doesn’t spell out the conjugating thiol atom, but it requires “linked … by a disulfide bond”).
Design-around leverage is limited if the product must preserve disulfide linkage geometry through D-cysteine X1. Moving to non-disulfide chemistries (thioether, maleimide thioether, amide, or other covalent linkages) is the cleanest conceptual carve-out, but it is outside what your claim text alone can confirm.
What do the homodimer claims do to scope and manufacturing exposure?
Homodimer as an additional compound state
- Claim 7: compound is a homodimer
- Claim 18/20: homodimer in the cysteine-conjugating-group and/or X2/X4 cases
- Claim 34: homodimer in the X2/D-alanine and X4/D-arginine case
If a product is a monomeric disulfide conjugate rather than a homodimeric species, it may not satisfy these dependent claims. Whether claim 1 covers monomer vs dimer depends on the “homodimer” being an added limitation only in dependent claims, not in claim 1 as stated. So the homodimer language functions as a narrower patent pocket rather than a requirement for all embodiments.
How do the peptide-length dependent claims constrain the sequence space?
8–15 residues range
- Claim 8: peptide length 8 to 15 residues
Tighter bands
- Claim 9: 8 to 11 residues
- Claim 10: 8 to 9 residues
This matters because the independent claim uses the X1–X7 motif (7 positions explicitly defined), while additional residues could exist if the peptide is longer than 7. The dependent range claims make that length explicit.
“Consists of the amino acid sequence” lock
- Claim 11: peptide consists of the amino acid sequence having the formula X1-X2-X3-X4-X5-X6-X7
So claim 11 excludes additional residues beyond the seven-position formula, again narrowing.
What do the SEQ ID NO-based claims (e.g., SEQ ID NO:28 and SEQ ID NO:3) imply about claim target embodiments?
Your claim set includes specific formula-based embodiments:
- Claim 37: compound comprising Ac-c(C)rrarar-NH2 (SEQ ID NO:28)
- Claim 38: same with the C acetylated
- Claim 40: compound comprising Ac-c(C)arrrar-NH2 (SEQ ID NO:3) with C acetylated
Even without the full mapping of each residue to X1–X7, these claims strongly indicate that the patent estate is anchored on at least two named short D-peptide structures with:
- Ac at N-terminus
- amidated C-terminus (“NH2” at the end)
- a cysteine-containing segment “c(C)” suggesting the disulfide-linked cysteine/conjugation motif
These SEQ ID claims typically create a higher litigation value pocket because they map a “known” embodiment more directly into infringement content.
What is the practical infringement checklist for US 9,278,995 based on your claims?
A product most likely falls within the claim 1 core if it has all of the following:
- D-peptide with a defined seven-position pattern X1–X7
- X1 is D-cysteine (the disulfide linkage site)
- X3, X5, X7 are D-arginine
- X2 and X4 are D-arginine/D-alanine with XOR complementarity
- X6 is non-cationic
- disulfide-bond connection between the peptide’s X1 cysteine and the conjugating group
- Dependent-claim mapping depends on:
- peptide length (8–15; 8–11; 8–9)
- whether the peptide consists solely of the X1–X7 sequence
- N-terminus acetylation
- C-terminus amidation
- conjugating group identity (cysteine/homocysteine/glutathione/PEGylated cysteine/thiol-polypeptide)
- conjugating group acetylation
- homodimer state
How strong is the patent “scope” based on internal claim architecture (sequence vs linkage vs modification)?
Strength drivers
- Linkage type is fixed: disulfide bond through peptide X1 D-cysteine
- Multiple stereochemical locks: D-configuration at key positions
- Sequence logic is enforced: X2/X4 XOR pattern
- Charge-based limiter: X6 non-cationic
- Terminal chemistry is optional via dependencies: gives flexibility for enforcement if product matches partial sets.
Potential breadth limits
- If a competitor uses:
- a different linkage chemistry than disulfide,
- a different stereochemical configuration at X1/X3/X5/X7,
- an X2/X4 pattern that violates the XOR rule,
- cationic residue at X6,
then literal infringement is structurally blocked.
Your prompt does not include the full spec, claim construction history, continuation family status, or prosecution record, so only the claim text can be assessed.
Patent landscape: what other patents would typically coexist around a disulfide-linked D-peptide conjugate?
Because the only provided artifact is the text of U.S. Patent 9,278,995 claims, the landscape below is limited to claim-architecture-driven “neighbor” classes rather than enumerated US patent numbers.
Neighbor claim categories likely surrounding the same technology
- Other disulfide-linked peptide conjugates
- different peptide motifs (different X1–X7 composition)
- different conjugating groups (thiol-bearing moieties)
- Terminal modification patents
- acetylated N-terminus versions
- amidated C-terminus versions
- Homodimer vs monomer composition patents
- salt forms and aggregation state claims
- PEGylation variants
- pegylated cysteine and variants
- Charge/biocompatibility adjustments
- amino acid selection at positions equivalent to X6
Why this matters for freedom-to-operate
US 9,278,995 is likely one of a set. In practice, if a product hits the same peptide backbone and linkage chemistry, it may also sit adjacent to other patents that claim:
- alternative peptide sequences within the same stereochemical pattern,
- alternative conjugating moieties within thiol/disulfide logic,
- formulation/administration aspects (not present in your claims but common in the family).
Where are the design-around pressure points?
Based solely on claim constraints:
- Break the disulfide linkage requirement
- Replace disulfide with thioether, amide, or other covalent chemistry.
- Remove or alter the D-cysteine at X1
- Since X1 is the disulfide linkage site, altering it can defeat claim 1.
- Violate the X2/X4 XOR pattern
- Use D-arginine at both X2 and X4, or D-alanine at both, to escape literal scope.
- Use a cationic amino acid at X6
- If X6 is basic/cationic, claim 1 fails.
- Avoid the exact terminal modifications
- This mostly affects dependent claims (Ac at N-terminus and/or amidation), not necessarily claim 1.
What patent “coverage pockets” exist in this claim set for litigation leverage?
From the dependent structure, there are enforcement pockets that can be separately asserted:
- Core structural pocket (claim 1): disulfide-linked D-peptide conjugates with locked residues and X2/X4 XOR.
- N-acetylation pocket (claim 2).
- C-amidation pockets (claims 3 and 4).
- Conjugating group identity pockets:
- cysteine (claims 6, 12–16)
- cysteine L vs D (claims 13–16)
- cysteine acetylation state (claims 14, 16, 22, 26, 28, etc.)
- other thiol moieties (claim 17: homocysteine, glutathione, pegylated cysteine, thiol-containing polypeptide)
- Homodimer pockets (claims 7, 18, 20, 34).
- Length-constrained pockets (claims 8–11).
- SEQ ID embodiment pockets (claims 37–38 and 40).
Key Takeaways
- US 9,278,995 claim scope centers on a disulfide-linked conjugate where the peptide has D-cysteine at X1 and D-arginine at X3/X5/X7, plus an X2/X4 XOR rule between D-arginine and D-alanine.
- X6 is limited by charge (“non-cationic amino acid”), adding a functional discriminator.
- Terminal chemistry (N-acetylation and C-amidation) and conjugating group acetylation are layered via dependent claims, creating multiple narrower infringement pockets.
- Homodimer and peptide length constraints add further pockets; they are likely not required for claim 1 if only stated in dependent form.
- The cleanest design-around conceptually is to change linkage chemistry away from disulfide or to break one of the hard sequence/X2-X4 pairing requirements.
FAQs
- If a compound matches the peptide sequence but uses a thioether instead of a disulfide, does it fall under this patent?
- How does the XOR condition on X2/X4 affect peptide substitutions at those positions?
- Do N-terminal acetylation and C-terminal amidation define the independent claim or only dependent variants?
- What conjugating groups are explicitly covered when the conjugating group is not cysteine?
- How do the “peptide length” and “consists of X1–X7” limitations change claim coverage for longer analogs?
References
- United States Patent No. 9,278,995 (claims as provided in prompt).
