Mutant IgG4 Antibody Low pH Stability
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Solution Overview
Problem
Human IgG4 antibodies exhibit instability at low pH, leading to aggregate formation, which can cause adverse effects such as infusion reactions and complement activation, posing challenges in their use as pharmaceutical agents.
Innovation Solution
A mutant IgG4 antibody is developed by substituting specific amino acids in the heavy chain constant region, including arginine at position 409 with lysine, threonine, methionine, or leucine, and introducing mutations in the CH2 and CH3 domains to enhance stability and reduce aggregate formation at low pH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If IgG4 antibody is used as pharmaceutical agent, then complement activation and antibody-dependent cellular cytotoxicity are reduced, but stability at low pH deteriorates leading to aggregate formation
Solution Approach 1:
The patent applies parameter changes by substituting specific amino acid residues in the IgG4 constant region (e.g., positions 228, 235, 409) to alter the physical-chemical properties of the antibody. These substitutions change the local charge distribution and structural characteristics, enabling the antibody to maintain stability at low pH while preserving its reduced complement activation properties.
Solution Approach 2:
The patent applies local quality by making targeted amino acid substitutions at specific locations in the constant region rather than modifying the entire antibody structure. The substitutions at positions 228, 235, and 409 locally modify the hinge and CH3 domains to improve low pH stability without affecting the overall effector function profile of IgG4.
2Stability of the object's composition
If amino acid substitution is introduced to improve low pH stability, then aggregate formation is reduced, but antibody structure complexity increases
Solution Approach 1:
The patent uses parameter changes by substituting amino acids with chemically similar residues (e.g., arginine to lysine, both basic amino acids) to minimize structural disruption while achieving the desired stability improvement. This approach changes local parameters without fundamentally altering the overall antibody architecture.
Solution Approach 2:
The patent employs simple amino acid substitutions rather than complex structural modifications, using basic building blocks (20 standard amino acids) to achieve stability improvement. This approach is analogous to using simple, readily available components rather than complex engineered structures.
Data Source
AI summary
A highly stable mutant of human IgG4 antibody is provided. Such antibody is an antibody in which the CH3 domain of human IgG4 is substituted with the CH3 domain of human IgG1 and which exhibits inhibited aggregate formation, an antibody in which the CH3 and CH2 domains of human IgG4 are substituted with the CH3 and CH2 domains of human IgG1, respectively, or an antibody in which arginine at position 409 indicated in the EU index proposed by Kabat et al. of human IgG4 is substituted with lysine and which exhibits inhibited aggregate formation.