Plasmid Name
pHC-IgG1-HexaBody(E345K/E430G)
Mutation Set
E345K / E430G
Selection Marker
Ampicillin
Promoter
CMV
Fc Engineering Overview
The Human IgG1 (HexaBody: E345K/E430G) Fc variant introduces a next-generation complement-enhancing double mutation in the CH3 domain designed to induce antigen-dependent Fc-Fc hexamerization on target cell membranes. This structural arrangement drives ultra-potent C1q recruitment and complement-dependent cytotoxicity (CDC) through avidity-driven membrane attack complex (MAC) assembly while preserving baseline FcγR binding and FcRn-mediated stability.
Functional Profile
| Property | Effect |
|---|---|
| FcγRI/II/III binding | Normal / WT Baseline |
| ADCC & ADCP | Normal / WT Baseline |
| CDC | Ultra-Enhanced ↑↑↑↑ (Avidity-driven MAC assembly) |
| FcRn binding | Normal / WT Baseline |
| Serum half-life | Normal / WT Baseline |
| Effector potency | Ultra-Potent CDC Enhancement (Selective C1q recruitment boost) |
Mechanism of Action
The HexaBody Fc variant introduces two structural substitutions—Glu345 to Lys and Glu430 to Gly—within the CH3-CH3 intermolecular contact interface:
- E345K Substitution: Introduces a positive charge that promotes favorable electrostatic interactions between adjacent Fc monomers.
- E430G Substitution: Increases local main-chain flexibility, lowering the thermodynamic barrier for self-assembly.
Upon target antigen binding, these modifications drive the cooperative clustering of six antibody monomers into ordered hexameric rings at the cell surface. This arrangement creates a high-avidity docking platform that perfectly matches the hexameric head structure of C1q, triggering massive complement activation without requiring fluid-phase aggregation.
Phenotypic Effects
- Ultra-potent activation of complement-dependent cytotoxicity (CDC).
- Massive enhancement of C1q recruitment via high-avidity hexameric interface geometry.
- Preserves baseline FcγR binding and cellular effector functions (ADCC/ADCP).
- Maintains normal FcRn-mediated recycling and systemic pharmacokinetics.
- Excellent biophysical stability and monomeric profile in solution prior to antigen binding.
Applications
- Therapeutic antibodies targeting low-to-moderate density cell-surface tumor antigens.
- Enhancement of CDC-depleting mechanisms for oncology targets (e.g., CD20, CD19, CD38).
- Infectious disease therapeutics requiring rapid, complement-mediated pathogen or host-cell destruction.
- Benchmark scaffold for studying cell-surface Fc-Fc clustering and complement cascade kinetics.
Plasmid Map & Feature Annotation
Insert Structure: VH – CH1 – hinge – CH2(wild-type) – CH3(E345K/E430G)
- VH: Variable heavy domain
- CH1: Constant heavy 1
- Hinge: Native IgG1 hinge
- CH2 (wild-type): Native IgG1 CH2 domain (retains N297 glycosylation)
- CH3 (E345K/E430G): Hexamerization-inducing double mutation
Product Note: The canonical HexaBody module (E345K/E430G) represents a paradigm shift in Fc engineering. Rather than altering direct contact residues for C1q within CH2, HexaBody enhances C1q avidity by organizing monomeric IgGs into ordered cell-surface arrays upon antigen engagement. This preserves native solution-state monomeric stability while achieving CDC potencies orders of magnitude above wild-type IgG1.
Fusion BioLabs Complement Modulated Family Comparison Matrix
| Variant | Mechanism | Complement Effect | Primary Application & Notes |
|---|---|---|---|
| human IgG1 (WT) Wild-Type |
Native C1q binding | ★★☆☆☆ | Baseline Control. Standard physiological C1q binding and CDC baseline for comparative assays. |
| human IgG1 (HexaBody-Extended) E345K / E430G / E431K |
On-cell hexamerization | ★★★★★+ | Hyper-CDC Enhancer. Triple mutation maximizing Fc-Fc intermolecular interactions; yields ultra-potent C1q avidity against ultra-low density antigen targets. |
| human IgG1 (HexaBody) E345K / E430G |
On-cell hexamerization | ★★★★★ | This Product. Canonical CDC-Boosting Fc. Enhances cell-surface hexamer assembly upon antigen binding to drastically boost C1q recruitment and membrane attack complex (MAC) formation. |
| human IgG1 (SEHF) S267E / H268F |
C1q binding loop enhancement | ★★★★☆ | High-Potency CDC Enhancer. Optimizes local electrostatic and structural interactions with C1q to boost complement lysis without requiring hexamerization. |
| human IgG1 (WS) K326W / E333S |
C1q binding loop enhancement | ★★★☆☆ | Strong CDC Enhancer. Synergistic double mutation in CH2 that significantly increases C1q binding affinity and complement killing. |
| human IgG1 (K322A) K322A |
C1q contact site ablation | ★☆☆☆☆ | Selective Human IgG1 CDC-Null. Abolishes C1q binding and CDC while maintaining native FcγR engagement (ADCC+/ADCP+). |
| human IgG2 (K322A) K322A |
C1q contact site ablation | ★☆☆☆☆ | Completely Silent Human IgG2 Control. Eliminates residual IgG2 C1q binding to yield a fully inert neutralizer (ADCCnull/ADCPnull/CDCnull). |
| mouse IgG2a (CompNull) L235E + E318A / K320A / K322A |
Complement binding triad ablation | ★☆☆☆☆ | Murine CDC-Null Control. Completely abolishes complement activation in murine models while preserving mouse FcγR engagement for syngeneic in vivo studies. |
Storage & Handling
- Store plasmid at −20°C.
- Avoid repeated freeze–thaw cycles.
- Use sterile technique when handling.
- Suitable for transient or stable mammalian expression.
References
- de Jong RN, Beurskens FJ, Verploegen S, Strumane K, van Kampen MD, Voorhorst M, Horstman W, Engelberts PJ, Oostindie SC, Wang G, Heck AJ, Schuurman J, Parren PW. A Novel Platform for the Potentiation of Therapeutic Antibodies Based on Antigen-Dependent Formation of IgG Hexamers at the Cell Surface. PLoS Biol. 2016 Jan 6;14(1):e1002344.
