A Checkpoint Reversal Receptor Mediates Bipartite Activation and Enhances CAR T-cell Function.

Area of Science:

• Immunology
• Cancer Biology
• Biotechnology

Background:

• Chimeric antigen receptor T cell (CART) therapy faces challenges in solid tumors due to immune inhibition.
• Effector cytokines upregulate the PD-L1 immune checkpoint in primary glioblastoma, limiting CART efficacy.
• Balancing CART function, persistence, and inflammation is critical for therapeutic success.

Purpose of the Study:

• To engineer PD-1 checkpoint reversal receptors (CPR) to counteract PD-L1 mediated inhibition in solid tumors.
• To evaluate the efficacy of CPR coexpressed with HER2-specific CARs (CPR/CART) in enhancing antitumor activity.
• To investigate the role of CPR costimulatory endodomains (CD28 or 41BB) in modulating T cell activation and memory differentiation.

Main Methods:

• Engineered bicistronic vectors to coexpress HER2-specific CARs with CPR containing CD28 or 41BB costimulatory endodomains.
• Assessed T cell activation, cytokine release, immune synapse formation, and metabolic parameters in vitro.
• Evaluated antitumor function of CPR/CART in xenograft models of glioblastoma and metastatic osteosarcoma.

Main Results:

• Both CPR28 and CPR41BB effectively counteracted PD-1 signaling in vitro.
• CPR41BB coexpressed with a first-generation CAR (CARζ/CPR41BB) promoted central memory differentiation after repeat antigenic stimulation.
• CARζ/CPR41BB T cells demonstrated superior antitumor function in glioblastoma and osteosarcoma xenograft models, with robust immune synapse formation and favorable metabolic parameters.

Conclusions:

• A CPR molecule with 41BB costimulation can curtail PD-1 inhibition and optimize T cell activation.
• This strategy enhances CART efficacy against solid tumors by improving function and persistence.
• Leveraging tumor-intrinsic signals like PD-1/PD-L1 in CART design offers a promising approach to improve solid tumor therapy.