Fc Domain Variants for Higher C1q Binding and CDC Activity

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Solution Overview

Problem

Current therapeutic antibodies, such as rituximab, face challenges with low complement-dependent cytotoxicity (CDC) due to suboptimal binding affinity to C1q, which limits their efficacy in cancer treatment, and also have issues with FcRn binding affinity affecting blood half-life and protein A binding affinity impacting production processes.

Innovation Solution

Development of novel human antibody Fc domain variants with specific amino acid substitutions, enhancing C1q binding affinity and maintaining FcRn and protein A binding affinities, thereby improving CDC activity and overall therapeutic efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If IgG3 is used to increase C1q binding affinity and CDC activity, then CDC activity is improved, but FcRn binding affinity decreases leading to shorter blood half-life

Engineering Contradiction:

ImproveCDC activityVSAvoidblood half-life

Core Design Contradiction:

ReliabilityVSDuration of action of stationary object

Solution Approach 1:

The patent applies parameter changes by introducing specific amino acid substitutions (K326N, N392K, I422V, H268Y, R435H, F436Y) at defined positions in the Fc domain to modify binding affinity characteristics. These parameter changes enable the antibody to achieve high C1q binding affinity while maintaining FcRn binding affinity, thus resolving the contradiction between CDC activity and blood half-life.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If IgG3 is used to enhance C1q binding affinity, then CDC activity is improved, but protein A binding affinity decreases impacting production

Engineering Contradiction:

ImproveCDC activityVSAvoidproduction efficiency

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent uses parameter changes by strategically substituting amino acids at specific positions (K326N, N392K, I422V, H268Y, R435H, F436Y) in the Fc domain to maintain protein A binding affinity while enhancing C1q binding affinity. This enables effective production through protein A chromatography while achieving high CDC activity.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If conventional Fc domain is used, then manufacturing simplicity is maintained, but C1q binding affinity is insufficient limiting therapeutic efficacy

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidC1q binding affinity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies parameter changes by introducing specific amino acid substitutions (K326N, N392K, I422V, H268Y, R435H, F436Y) at defined positions in the Fc domain to significantly enhance C1q binding affinity while maintaining compatibility with conventional manufacturing processes and protein A chromatography purification.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The Fc domain variants exhibit significantly increased C1q binding affinity, leading to enhanced CDC activity, improved therapeutic efficiency, and sustained blood half-life, while retaining FcRn and protein A binding capabilities.

Implementation Method 1

the Fc domain of the antibody plays a crucial role in complement molecule recruitment and complement-dependent cytotoxicity (CDC)... directly binds to a C1q molecule that constitutes the C1 complex to activate protease (C1r 2 s 2 ) of the C1 complex

Methodology Applied

Scientific EffectBinding affinity:

Implementation Method 2

IgG3 has a disadvantage of having much lower FcRn binding affinity, which is required for the antibody half-life in the blood

Methodology Applied

Scientific EffectBinding affinity:

Implementation Method 3

much lower protein A binding affinity than IgG1, which is required for a process of producing antibody drugs and Fc-fusion proteins

Methodology Applied

Scientific EffectBinding affinity:

Implementation Method 4

a complement pathway is activated, ultimately forming a membrane attack complex on the target cell surface, resulting in the death of the target cell

Methodology Applied

Scientific EffectComplement activation:

Implementation Method 5

the Fc domain of the antibody is responsible for the major therapeutic effect of therapeutic antibodies by inducing the effector functions of ADCC by binding to FcyRIIIa

Methodology Applied

Scientific EffectReceptor binding:

Data Source

PatentEP4671271A1FC variants with improved human c1q binding affinity

Publication Date: 2025.12.31 KOREA UNIV RES & BUSINESS FOUND

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AI summary

The present invention relates to a glycosylated Fc variant with improved selective binding affinity to FcγRIIIa. Compared to conventional antibodies approved as antibody therapeutic agents, novel human antibody Fc domain variants of the present invention have reduced binding affinity to FcγRIIb, which is an immuno-inhibitory receptor, have improved binding affinity to FcγRIIIa (an increase in the A/I ratio), which is an immuno-activating receptor, thereby having a remarkably improved ability to induce ADCC, and have the effect of maximizing the immune action mechanism of therapeutic protein drugs, and thus can be effectively used in antibody drugs.