FcγRs Modulate the Anti-tumor Activity of Antibodies Targeting the PD-1/PD-L1 Axis

Area of Science:

• Immunology
• Oncology
• Pharmacology

Background:

• Immune checkpoint inhibitors, particularly monoclonal antibodies (Abs) targeting the programmed cell death protein 1 (PD-1) pathway, offer significant clinical benefits in various cancers.
• The fragment crystallizable (Fc) domain of antibodies plays a critical role in mediating effector functions and influencing therapeutic efficacy.

Purpose of the Study:

• To investigate the specific contribution of Fc domains in anti-PD-1 and anti-PD-ligand 1 (L1) monoclonal antibodies for optimal anti-tumor activity.
• To determine the distinct mechanisms and Fc gamma receptor (FcγR) dependencies underlying the in vivo efficacy of anti-PD-1 versus anti-PD-L1 Abs.

Main Methods:

• Comparative analysis of anti-PD-1 and anti-PD-L1 monoclonal antibodies with varying Fc domain functionalities.
• In vivo studies to assess anti-tumor activity and FcγR dependency.
• Flow cytometry and immune cell subset analysis within the tumor microenvironment.

Main Results:

• Anti-PD-1 antibodies demonstrated FcγR independence in vivo; FcγR-binding capacity was found to impair their anti-tumor activity.
• Anti-PD-L1 antibodies exhibited enhanced anti-tumor efficacy when FcγR-activating binding was engineered into the molecules.
• FcγR engagement by anti-PD-L1 antibodies modulated myeloid cell subsets within the tumor microenvironment.

Conclusions:

• The Fc domain's role in anti-tumor activity differs significantly between anti-PD-1 and anti-PD-L1 antibodies, highlighting distinct FcγR dependencies.
• Optimizing Fc domain interactions with FcγRs can enhance the therapeutic potential of anti-PD-L1-based immunotherapies.
• Understanding these Fc-mediated mechanisms is crucial for designing next-generation immune checkpoint inhibitors.