CAR affinity modulates the sensitivity of CAR-T cells to PD-1/PD-L1-mediated inhibition

Area of Science:

• Immunotherapy
• Oncology
• Cellular Engineering

Background:

• Chimeric antigen receptor (CAR)-T cell therapy shows promise for solid tumors but faces challenges.
• T-cell inhibition via the PD-1/PD-L1 axis is a major hurdle for CAR-T cell efficacy in solid tumors.
• The impact of disrupting the PD-1/PD-L1 pathway on CAR-T cells is complex and yields controversial results.

Purpose of the Study:

• To investigate the hypothesis that CAR-antigen affinity modulates CAR-T cell susceptibility to PD-1/PD-L1-mediated inhibition.
• To systematically compare the behavior of low-affinity (LA) and high-affinity (HA) HER2-targeting CAR-T cells in preclinical models.
• To evaluate the effect of PD-1 knockout on CAR-T cell function and antitumor activity in relation to CAR affinity.

Main Methods:

• Systematic interrogation of LA and HA HER2-targeting CAR-T cells in various preclinical models.
• In vitro studies using tumor cell lines and supported lipid bilayers with varying PD-L1 densities to assess T-cell inhibition.
• CRISPR/Cas9-mediated knockout (KO) of PD-1 in CAR-T cells to evaluate functional and antitumor effects.

Main Results:

• LA CAR-T cells demonstrated increased sensitivity to PD-L1-mediated inhibition compared to HA CAR-T cells.
• PD-1 KO significantly enhanced LA CAR-T cell cytokine secretion, polyfunctionality in vitro, and antitumor effects in vivo.
• PD-1 KO also led to downregulation of T-cell exhaustion gene signatures in LA CAR-T cells, while HA CAR-T cells remained largely unaffected.
• CD28 and ICOS co-stimulated CAR-T cells showed less sensitivity to PD-L1 inhibition, even with LA, compared to 4-1BB co-stimulated CAR-T cells.

Conclusions:

• CAR-antigen affinity is a critical determinant of CAR-T cell sensitivity to PD-1/PD-L1-mediated immune suppression.
• Disrupting the PD-1/PD-L1 pathway, particularly via PD-1 KO, can reinvigorate exhausted LA CAR-T cells, enhancing their therapeutic potential.
• These findings offer insights for optimizing CAR-T therapies targeting solid tumors by considering CAR affinity and PD-1/PD-L1 pathway modulation.