Crystal structure of a novel asymmetrically engineered Fc variant with improved affinity for FcγRs

Area of Science:

• Immunology
• Structural Biology
• Biochemistry

Background:

• Optimizing Fc and Fc gamma receptor (FcγR) interactions is crucial for enhancing the efficacy of anticancer monoclonal antibodies (mAbs).
• Existing Fc engineering strategies like afucosylation and symmetric substitutions show limitations in improving FcγR binding and thermal stability.
• Asymmetric Fc engineering offers a novel approach to fine-tune Fc-FcγR interactions and enhance antibody potency.

Purpose of the Study:

• To elucidate the structural mechanism behind improved FcγR binding achieved by asymmetric Fc engineering.
• To analyze the crystal structure of a novel asymmetrically engineered Fc (asym-mAb23) in complex with FcγRIIIa.
• To understand how asymmetric substitutions contribute to enhanced Fc-FcγR interactions.

Main Methods:

• Crystallography
• Structural analysis
• Biochemical assays to assess binding affinity.

Main Results:

• The crystal structure of asym-mAb23 complexed with FcγRIIIa was determined.
• Asym-mAb23 demonstrated significantly enhanced binding affinity for FcγRIIIa and FcγRIIa compared to previously reported Fc variants.
• Structural analysis revealed specific features of asymmetric engineering and the contribution of individual substitutions to improved Fc-FcγR interaction.

Conclusions:

• Asymmetric Fc engineering provides a powerful strategy to enhance FcγR binding and improve the potency of therapeutic antibodies.
• The elucidated structural mechanism provides a foundation for designing next-generation, highly potent asymmetric Fc variants.
• This structural insight can guide the development of more effective anticancer mAbs.