Mutant IgG4 Antibody Stabilizing CD32b Binding
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Solution Overview
Problem
Current therapeutic antibodies based on IgG1 are limited by their effector functions and stability issues, particularly for autoimmune diseases and allergies, where IgG4's half-molecule formation and Fab arm exchange lead to reduced therapeutic efficacy.
Innovation Solution
A mutant human IgG4 with a lysine at position 409 (409K) exhibits increased binding affinity and activation potential for CD32b/c receptors, enhancing therapeutic effects in autoimmune diseases and allergies by stabilizing the molecule and preventing half-molecule formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If IgG1 is used as the therapeutic antibody backbone, then effector functions are provided, but stability issues and unwanted immune activation occur
Solution Approach 1:
The patent changes the isotype parameter from IgG1 to IgG4, which fundamentally alters the effector function profile. IgG4 lacks complement activation and has reduced FcγR binding, thereby eliminating unwanted immune activation while maintaining stability. The mutation R409K further optimizes this isotype selection by enhancing CD32b/c binding affinity specifically.
Solution Approach 2:
The patent converts the typically harmful half-molecule formation and Fab arm exchange of IgG4 into a benefit by showing that these features, when combined with the R409K mutation, actually prevent unwanted immune activation while maintaining sufficient stability for therapeutic use. The mutation stabilizes the IgG4 structure enough to prevent excessive dissociation into half-molecules.
2Object-generated harmful factors
If IgG4 is used to avoid effector functions, then unwanted immune activation is reduced, but binding affinity to CD32b/c and therapeutic efficacy are decreased
Solution Approach 1:
The patent introduces a specific amino acid substitution (R409K) in the Fc region of IgG4 that changes the binding parameters to CD32b/c receptors. This mutation increases binding affinity by approximately 10-fold compared to wild-type IgG4, thereby restoring therapeutic efficacy while maintaining the desirable property of reduced unwanted immune activation.
Solution Approach 2:
The mutation is localized to a specific region (position 409 in the Fc region) of the IgG4 molecule, specifically optimizing the interaction with CD32b/c receptors without affecting other regions of the antibody. This localized change allows selective enhancement of desired binding while preserving the overall IgG4 profile of reduced effector functions.
3Object-generated harmful factors
If IgG4 is used to reduce effector functions, then complement-mediated lysis and antibody-dependent cytotoxicity are eliminated, but half-molecule formation reduces therapeutic effect
Solution Approach 1:
The R409K mutation changes the structural parameters of IgG4 to reduce half-molecule formation. The lysine substitution at position 409 appears to stabilize the Fc region, reducing the tendency of IgG4 to dissociate into half-molecules, thereby maintaining therapeutic efficacy while preserving the elimination of complement-mediated lysis and antibody-dependent cytotoxicity.
Data Source
AI summary
The present invention relates to polypeptides comprising a mutant human IgG4, which mutant human IgG4 is capable of increasing the binding to and activation of immunoreceptor tyrosine-based inhibitory motif (ITIM)-containing FcγRIIb/c (CD32b), but not FcγRIIa (CD32a). More specifically, the invention relates to polypeptides comprising at least one human IgG4 with a lysine at position 409 (409K), using the EU index according to Kabat et al., which IgG4 is capable of binding to human CD32b/c with a statistically significant (p=0.05) higher binding affinity than a wild-type human IgG1 and than a wild-type human IgG4, for use in the prevention and/or treatment of an autoimmune disease or allergy, as further defined in the claims.