US Patent 10,227,383 landscape and claim-scope analysis (IgG-binding disulfide/linked cysteine peptides)
Executive summary: U.S. Patent 10,227,383 claims short IgG-binding peptides (13–17 residues) built around a constrained sequence motif containing Cys–(2–4 residues)–H–(pattern including G–L–V–W–C), with optional covalent stabilization via internal disulfide (two cysteines) or via cross-linkers that connect a Cys-modified peptide to IgG. The claim set is broad in residue substitution (Xaa “other than cysteine” except where limited), medium in length (13–17), and high in functional constraint (must bind human and/or rabbit IgG). Dependent claims add narrower embodiments: specific sub-templates (SEQ ID NO: 1–17, 36, 37), specific cross-linkers (DSG/DSS and related imido/sulfhydryl-reactive linkers), and conjugate/product-by-process claims covering IgG-peptide conjugates and production by cross-linking.
What follows is a claim-by-claim scope and enforceability map focusing on likely infringement touchpoints, design-around pathways, and where third-party patent estates typically crowd (short peptides, antibody-binding mimetics, and cysteine cross-linking conjugates). This analysis is anchored only to the claim text provided.
What does US 10,227,383 claim for IgG-binding peptides and how broad is claim coverage?
Core independent claim: Claim 1 covers a peptide defined by:
- Sequence architecture (Formula I):
(X)1-3–C–(X)2–H–Xaa1–G–Xaa2–L–V–W–C–(X)1-3 (SEQ ID NO: 43)
- Length: 13 to 17 amino acid residues
- Residue constraints:
- Each X is any amino acid other than cysteine
- C is cysteine at two positions
- H is histidine
- Xaa1 is Lys or one of several acidic/special residues (includes cysteine option, Asp/Glu, 2-aminosuberic acid, diaminopropionic acid)
- G is glycine
- Xaa2 is Glu or Asn
- L is leucine, V is valine, W is tryptophan
- Functional requirement: peptide exhibits binding to human IgG and/or rabbit IgG
- Optional stabilization: cysteines “2 to 4 amino acids from N-terminus” and “2 to 4 amino acids from C-terminus” can be:
- linked via a linker, or
- (by implication in later claims) linked via disulfide or through cross-linking chemistry
Claim-1 risk profile for competitors
From an infringement perspective, Claim 1 is the hardest to design around because it requires:
- The specific motif containing H, G, L, V, W in the correct positions,
- Two cysteines at positions constrained by the “2–4 residues from each terminus” language, and
- IgG-binding activity to human and/or rabbit IgG.
That combination is still broad because:
- “X” positions allow nearly any residue except cysteine.
- Xaa1 and Xaa2 each allow limited sets, not single residues.
- Length variation (13–17) lets multiple register offsets.
Most likely infringement scenarios
- Testing/optimization peptides that preserve the motif and include cysteines positioned for cyclization (internal link) to retain binding affinity.
- Peptide mimetics used as immunoassay handles or as Fc/IgG-binding ligands with cysteine-enabled stabilization.
- Conjugates might fall outside Claim 1 if the product is “conjugate” rather than free peptide, but the conjugate claims depend on peptide embodiments that match Claim 1.
What specific sequence templates are enumerated in dependent claims (SEQ ID NO: 1–17, 36, 37) and what does that mean for enforceability?
Dependent claims 5–8 and 15–17 lock in particular exemplars. Even if not exhaustive, the listed sequences are strong evidence for:
- Written description enablement (the applicant demonstrated peptide variants),
- Claim construction anchors (courts often treat described examples as interpretive guideposts).
Claim 5: “consists of” enumerated peptide sequences (15 examples)
Claim 5 limits the peptide to one of the following amino acid sequences 1)–15) (from TABLE-US-00007):
- (SEQ ID NO: 1) DCAYHXaa1GELVWCT
- (SEQ ID NO: 2) GPDCAYHXaa1GELVWCTFH
- (SEQ ID NO: 3) RCAYHXaa1GELVWCS
- (SEQ ID NO: 4) GPRCAYHXaa1GELVWCSFH
- (SEQ ID NO: 5) SPDCAYHXaa1GELVWCTFH
- (SEQ ID NO: 6) GDDCAYHXaa1GELVWCTFH
- (SEQ ID NO: 7) GPSCAYHXaa1GELVWCTFH
- (SEQ ID NO: 8) GPDCAYHXaa1GELVWCSFH
- (SEQ ID NO: 9) GPDCAYHXaa1GELVWCTHH
- (SEQ ID NO: 10) GPDCAYHXaa1GELVWCTFY
- (SEQ ID NO: 11) SPDCAYHXaa1GELVWCTFY
- (SEQ ID NO: 12) SDDCAYHXaa1GELVWCTFY
- (SEQ ID NO: 13) RGNCAYHXaa1GQLVWCTYH
- (SEQ ID NO: 36) GXaa2DCAYHXaa1GELVWCTXaa2H
- (SEQ ID NO: 37) RRGPDCAYHXaa1GELVWCTFH
Variables:
- Xaa1 is constrained (Lys, Cys, Asp, Glu, 2-aminosuberic acid, diaminopropionic acid)
- In #14, Xaa2 is homocysteine (explicitly)
Practical implication: if a competitor product uses one of these enumerated sequences (or close variants with substitution outside allowed sets), Claim 5 may be directly asserted. Claim 1 could still reach beyond these exemplars.
Claim 6–7: formula (IV) and “consists of” four sequences
Claim 6 introduces Formula (IV):
D–C–Xaa3–Xaa4–H–Xaa1–G–Xaa2–L–V–W–C–T (SEQ ID NO: 46)
Claim 7 restricts peptides to four sequences (TABLE-US-00008):
- (SEQ ID NO: 14) DCTYHXaa1GNLVWCT
- (SEQ ID NO: 15) DCAYHXaa1GNLVWCT
- (SEQ ID NO: 16) DCTYHXaa1GELVWCT
- (SEQ ID NO: 17) DCAWHXaa1GELVWCT
These “consists of” sequences reduce design-around room if competitors optimize within this narrower scaffold.
Claim 8: internal cysteine linkage or linker representation
Claim 8 covers two embodiments:
- disulfide bond between the relevant N-terminal and C-terminal cysteines, or
- sulfide groups linked “via a linker” represented by a chemical structure (Str00008).
Practical implication: This is where product/process ambiguity matters. Competitors relying on linear peptides without internal covalent constraint may avoid Claim 8 (but still risk Claim 1 if Claim 1 itself covers unlinked cysteines and binding), depending on claim construction.
How do dependent claims on “cross-linking agents” expand infringement exposure?
Claim 12–14: modified Xaa1 with cross-linking agents (DSG/DSS and others)
Claim 12: Xaa1 modified with a cross-linking agent.
Claim 13: cross-linking agent selected from:
- DSG (disuccinimidyl glutarate)
- DSS (disuccinimidyl suberate)
- DMA (dimethyl adipimidate dihydrochloride)
- DMP (dimethyl pimelimidate dihydrochloride)
- DMS (dimethyl suberimidate dihydrochloride)
- DTBP (dimethyl 3,3'-dithiobispropionimidate dihydrochloride)
- DSP (dithiobis(succinimidyl propionate))
Claim 14 narrows further to DSG or DSS.
Claim 16–18: IgG conjugates and methods of producing them
- Claim 16: conjugate comprising peptide (Claim 12) and IgG, formed by cross-linking of modified peptide and IgG.
- Claim 17: pharmaceutical composition comprising peptide or IgG conjugate; conjugate formed by cross-linking reaction; Xaa1 modified with cross-linking agent.
- Claim 18: method for producing conjugate:
(a) modify Xaa1 with cross-linking agent
(b) mix modified peptide with IgG to cross-link.
Enforceability and litigation leverage
These dependent claims create a second infringement lane:
- If accused products are IgG conjugates (bioconjugates, assay reagents, Fc-targeting ligands, targeted carriers), Claim 16–18 let the patentee target the product and the production steps.
- Many bioscience supply chains use standard conjugation chemistries. If the conjugation agent matches DSG/DSS or enumerated alternatives, these claims become directly relevant.
Key vulnerability for competitors
Design-around by changing the linker chemistry is plausible only if it avoids:
- the enumerated cross-linkers, and
- the specific “modified Xaa1” linkage logic.
If competitors use a different reactive handle at a different residue (not Xaa1), they can reduce risk, but must still match the underlying peptide motif for Claim 1 coverage.
What product forms are explicitly claimed: labeled peptides, peptide bound with a drug, and peptide-IgG conjugates?
Claim 9: labeled peptide
Claim 9 adds labeling, which tends to be broad in many jurisdictions because “labeling agent” is often undefined in claims (scope then hinges on written definition in specification, which is not provided here). Still, the claim is dependent on Claim 1, so the peptide must already match the IgG-binding scaffold.
Claim 10: peptide bound with a drug
This expands to drug-peptide complexes, potentially relevant to:
- prodrugs,
- conjugated payload delivery systems where peptide mediates IgG binding.
Claim 17: pharmaceutical composition
This is commercial-focused: it lets the patentee assert on formulations and not only on conjugates.
What does Claim 15 claim (a second independent “IgG-binding” peptide scaffold) and how does it compare to Claim 1?
Claim 15 is another independent peptide claim (13 amino acid length) with Formula (V):
D–C–Xaa2–Xaa3–Xaa4–Xaa1–G–Xaa5–L–Xaa6–W–C–T (SEQ ID NO: 47)
Constraints:
- Length: 13 residues
- Binding: binds human IgG and/or rabbit IgG
- Residue allowances:
- Xaa2: A/S/T
- Xaa3: W or Y
- Xaa4: H or R or S
- Xaa1: Lys/Cys/Asp/Glu/2-aminosuberic acid/diaminopropionic acid
- Xaa5: Glu/Asn/Arg/Asp
- Xaa6: I or V
How Claim 15 changes the freedom-to-operate map
Compared with Claim 1:
- Claim 15 hard-codes more specific positions (not just “X” generic).
- It shifts the motif to a different register: it starts with D-C and ends with -C-T, with W and C still present.
- It drops the explicit “(X)1-3 … (X)1-3” variability and instead uses per-position allowed amino sets.
For competitors, this means dual scaffold risk:
- A peptide may miss Claim 1 because its terminal spacing does not meet cysteine placement rules or motif offsets,
- yet still land in Claim 15 if its exact 13-residue pattern matches.
What design-arounds are most credible based on the claim text?
The claim text indicates infringement is governed by a mix of:
- sequence pattern requirements,
- cysteine placement and covalent linkage features (depending on dependent claim strategy),
- and functional IgG binding.
1) Remove one of the cysteine residues or break the spacing
- Claim 1 and 15 require cysteines at least at two positions.
- If a competitor designs a non-cysteine ligand (or uses different thiol chemistry), they can avoid cysteine-based linkage embodiments (Claim 8, crosslinking based on cysteine or cysteine-modified Xaa1 logic), but must still avoid functional binding coverage if Claim 1 is construed to include unlinked cysteines.
2) Keep cysteines but change fixed motif residues (H, G, L, V, W)
- Claim 1 fixes H, G, L, V, W.
- Changing any of these likely breaks capture.
3) Change length and terminal spacing
- Claim 1 allows 13–17 residues, but cysteine “2 to 4 amino acids from N-terminus” and “2 to 4 amino acids from C-terminus” is restrictive.
- Claim 15 locks 13 residues.
4) Use alternative cross-linking chemistry not in the enumerated set
- Claim 13 enumerates cross-linkers.
- Claim 14 narrows to DSG/DSS.
- A competitor could use a different cross-linking reagent and a different modification site, aiming to avoid Claim 12–14 and product claims tied to “formed through a cross-linking reaction” of modified peptide and IgG.
5) Avoid the “Xaa1 modified with a cross-linking agent” structure
Even if cross-linking occurs, the claim depends on Xaa1 being modified. A competitor that attaches to a different residue or terminus likely avoids dependent claim capture, though Claim 16 and 17 still tie to conjugates formed through cross-linking of modified peptide and IgG.
How strong is the patent estate for likely infringement: independent claims vs dependent “scaffold lists” and conjugate/process claims?
Based on claim architecture alone:
- Independent claim 1 is the broadest capture lever for free peptides and likely the central infringement target.
- Independent claim 15 adds a second scaffold with tighter positional constraints.
- “Consists of” lists (Claim 5 and Claim 7) increase litigation traction because enumerated sequences support factual showings of direct infringement.
- Conjugate and method claims (16–18) increase leverage against product commercialization and manufacturing.
Net effect: the estate is structured to cover both:
- peptide ligands (sequence + function), and
- IgG conjugates (chemistry + product + method),
which reduces exit routes for competitors who otherwise might only be making free peptides.
What patent landscape issues typically co-exist for IgG-binding peptide ligands (and where would challenges likely cluster)?
Without bibliographic data for family members, continuation filings, prosecution history, or other patents, the analysis focuses on claim-driven overlap patterns commonly seen in this category:
- Short IgG/Fc-binding peptides often cluster around constrained motifs and cysteine-enabled stabilization for activity and manufacturability.
- Disulfide/cyclized peptides create overlap between “internal stabilization” patents and “IgG-binding” patents.
- Bioconjugation method claims often overlap across reagent classes: NHS-ester cross-linking, imidoesters, thioether/disulfide formation, and heterobifunctional handles.
- Assay and delivery uses drive composition and method-of-use patents layered on top of generic ligand patents.
Where US 10,227,383 creates leverage:
- cross-linker specificity in dependent claims (DSG/DSS and related list),
- conjugate and composition claims that can reach end-user products.
Where validity challenges typically cluster (claim-text based):
- functional claiming (“exhibits binding to human IgG and/or rabbit IgG”) can be attacked as indefinite if the patent does not define an objective test method. (That is not assessed here because specification details are not provided.)
- broad residue permutations paired with a binding function can raise written description or enablement issues if the specification does not support the full breadth across all allowed substitutions and lengths.
Key takeaways
- US 10,227,383 claims two IgG-binding peptide scaffolds: Claim 1 (13–17 residues) and Claim 15 (13 residues), both anchored on conserved residues including H, G, L, V, W and cysteines.
- Dependent claims materially expand coverage into:
- enumerated peptide sequences (“consists of” lists in Claims 5 and 7),
- internal cysteine stabilization (Claim 8),
- IgG conjugates via cross-linking chemistry (Claims 12–18), including enumerated cross-linkers such as DSG and DSS.
- The strongest infringement pathways for commercial actors are likely:
- selling or using peptide-IgG conjugates made with DSG/DSS or enumerated cross-linkers (Claims 16–18),
- using peptide sequences that match enumerated examples (Claims 5 and 7), plus demonstrating IgG-binding.
- Credible design-arounds center on breaking at least one of the essential constraints: cysteine placement/motif residues, cysteine-based internal linking, or use of the enumerated cross-linkers and residue-targeted modification logic.
FAQs
1) What specific residues are mandatory for the IgG-binding motif in Claim 1?
Histidine (H), glycine (G), leucine (L), valine (V), and tryptophan (W) are fixed in their positions within Formula (I), with cysteines at two defined locations.
2) Does the patent require the peptide to be cyclized/disulfide-linked?
Claim 1 includes an optional “linked via a linker” feature for cysteines, while Claim 8 expressly covers disulfide linkage between the relevant cysteines or cysteine linkage via a linker. The degree of requirement depends on whether a specific dependent claim is asserted.
3) Which cross-linkers are explicitly claimed for attaching the peptide to IgG?
Claim 13 enumerates DSG, DSS, DMA, DMP, DMS, DTBP, and DSP; Claim 14 narrows to DSG or DSS.
4) Are “labeled peptides” covered even if the label changes properties?
Claim 9 depends on Claim 1, so the peptide must still match the IgG-binding scaffold; the claim adds labeling without changing the core sequence/function requirements.
5) What length constraints distinguish Claim 1 from Claim 15?
Claim 1 covers peptides 13–17 residues; Claim 15 covers peptides of 13 residues only.
References (APA)
No external sources cited because the prompt provides only the claim text for US 10,227,383 and does not include any docket, publication, family, prosecution history, or related document identifiers.
