Antigen-induced chimeric antigen receptor multimerization amplifies on-tumor cytotoxicity

Area of Science:

• Immunology
• Structural Biology
• Biochemistry

Background:

• Receptor dimerization/oligomerization is crucial for cellular communication and signal transduction.
• Cell-surface antigen-induced multimerization (AIM) is a known mechanism but underexplored in chimeric antigen receptor (CAR) engineering.
• T cell-based therapies, particularly for multiple myeloma, can benefit from enhanced activation mechanisms.

Purpose of the Study:

• To elucidate the structural and functional model of antigen-induced multimerization in CAR engineering.
• To investigate the role of BCMA-induced multimerization of ciltacabtagene autoleucel (cilta-cel) CAR in enhancing T cell-mediated cytotoxicity.
• To provide a framework for utilizing the AIM approach in designing next-generation CARs.

Main Methods:

• Co-development of ciltacabtagene autoleucel (cilta-cel) CAR with tandem BCMA-targeted nanobodies.
• Crystallographic analysis of BCMA-nanobody complexes.
• Analytical ultracentrifugation and small-angle X-ray scattering to characterize molecular interactions.

Main Results:

• Atomic details of BCMA-nanobody hetero-multimerization were revealed.
• Interdependent BCMA apposition and CAR juxtaposition in solution were characterized.
• BCMA-induced nanobody CAR multimerization significantly enhanced T cell cytotoxicity, immune synapse formation, and cytokine release against myeloma cells.

Conclusions:

• BCMA-induced cilta-cel CAR multimerization amplifies T cell-mediated cytotoxicity against multiple myeloma.
• The study provides a structural and functional model for antigen-induced multimerization in CARs.
• The AIM approach offers a promising strategy for next-generation CAR design.