Anti-C1q Fab Fragments for Selective Complement Inhibition

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Solution Overview

Problem

Current complement inhibitors, including protein drugs and low molecular weight/small molecule inhibitors, suffer from issues such as poor tissue penetration, high toxicity, low potency, poor selectivity, and immunogenicity, making them ineffective for treating inflammatory and neurodegenerative diseases associated with complement activation.

Innovation Solution

Development of an antibody Fab fragment that binds to C1q, comprising specific heavy and light chain domains, which is designed for higher tissue penetration, reduced immunogenicity, and effective inhibition of the complement cascade.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If protein drugs or low molecular weight inhibitors are used as complement inhibitors, then complement activation can be inhibited, but tissue penetration is poor and toxicity is high

Engineering Contradiction:
Improvecomplement inhibition efficacyVSAvoidtoxicity and poor tissue penetration
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent segments the antibody structure by using only the Fab fragment (antigen-binding portion) rather than the complete antibody molecule. This segmentation removes the Fc region that mediates effector functions, thereby reducing immunogenicity and toxicity while preserving complement inhibition capability through the intact variable regions that bind C1q.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention extracts and utilizes only the essential antigen-binding Fab fragment from the complete antibody structure. By taking out the Fc portion responsible for unwanted immunogenic effects and isolating the Fab fragment that contains the C1q-binding capability, the patent achieves reduced toxicity while maintaining therapeutic efficacy.

Inventive Principle:
Principle #2Taking out (Extraction)

2Reliability

If complete antibodies are used to inhibit complement activation, then complement cascade inhibition is effective, but immunogenicity increases

Engineering Contradiction:
Improvecomplement cascade inhibitionVSAvoidimmunogenicity
Core Design Contradiction:
ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent segments the antibody into Fab and Fc portions, using only the Fab fragment for therapeutic application. This segmentation eliminates the Fc region that is primarily responsible for immunogenic responses, while the Fab fragment retains the ability to bind C1q and inhibit complement activation.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention extracts the immunogenic Fc portion from the complete antibody structure and utilizes only the non-immunogenic Fab fragment that contains the essential C1q-binding function. This extraction approach reduces immunogenicity while preserving the therapeutic mechanism of action.

Inventive Principle:
Principle #2Taking out (Extraction)

3Reliability

If conventional complement inhibitors are used, then complement activation is inhibited, but selectivity is poor leading to off-target effects

Engineering Contradiction:
Improvecomplement activation inhibitionVSAvoidpoor selectivity and off-target effects
Core Design Contradiction:
ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies local quality by engineering the Fab fragment with specific affinity and specificity for C1q through optimized variable regions. This localized optimization of binding characteristics at the antigen-binding site enhances selectivity for the complement system while minimizing off-target effects on other physiological pathways.

Inventive Principle:
Principle #3Local quality

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 antibody Fab fragment effectively inhibits complement activation, providing therapeutic benefits for neurodegenerative disorders and inflammatory conditions by reducing synapse loss and tissue damage, with improved tissue penetration and lower immunogenicity compared to existing inhibitors.

Implementation Method 1

an antibody Fab fragment that binds to C1q, comprising a heavy chain domain and a light chain domain

Methodology Applied
Scientific EffectAntigen-antibody binding:

Data Source

PatentEP3380518B1Anti-complement factor c1q fab fragments and uses thereof
Publication Date: 2026.03.25 ANNEXON INC
  • EP3380518B1 patent drawingFigure 1A
  • EP3380518B1 patent drawingFigure 1B
  • EP3380518B1 patent drawingFigure 2

AI summary

The present disclosure relates generally to anti-C1q antibody Fab fragments and methods of using the same.