Functional avidity of anti-B7H3 CAR-T constructs predicts antigen density thresholds for triggering effector function

Area of Science:

• Immunology
• Cancer Biology
• Cellular Engineering

Background:

• Solid cancer treatments using Chimeric Antigen receptor T cell (CAR-T) therapies face challenges with T cell expansion and survival within the tumor microenvironment.
• The B7H3 antigen is a promising target for CAR-T therapy due to its broad applicability in various solid cancers.

Purpose of the Study:

• To investigate the relationship between antibody/antigen affinity, cellular avidity, and the efficacy of CAR-T cells targeting the B7H3 antigen.
• To assess the impact of CAR-T cell interaction dynamics on anti-tumoral responses in solid cancer models.

Main Methods:

• Evaluation of three clinical candidate binders for B7H3-targeting CAR-T cells.
• Assessment of cellular avidity, cytotoxicity duration in tumoroid re-stimulation assays, and in vivo anti-tumoral responses.
• Utilizing BEHAV3D video microscopy for single-cell resolution analysis of CAR-T and tumor cell interactions.

Main Results:

• A threshold avidity for CAR-T/tumor cell interaction and B7H3 expression level was identified, correlating with enhanced CAR-T functionality.
• Longer cumulative interaction times between CD8+ CAR-T cells and tumor targets were associated with increased CAR-T cell expansion and sustained tumor control.
• Lower expression of checkpoint receptors did not correlate with improved anti-tumor function.

Conclusions:

• CAR-T cell design for targeting B7H3-expressing solid tumors can be optimized by considering avidity thresholds and interaction dynamics.
• These findings offer insights for developing effective anti-B7H3 CAR-T cells, particularly for targeting tumors with heterogeneous antigen expression and preventing relapse.