The Art and Science of Selecting a CD123-Specific Chimeric Antigen Receptor for Clinical Testing

Area of Science:

• Immunotherapy
• Oncology
• Molecular Biology

Background:

• Chimeric antigen receptor (CAR) T-cells offer a promising therapeutic strategy for refractory/recurrent acute myeloid leukemia (AML) by targeting the CD123 antigen.
• The development of effective CAR T-cell therapies requires careful optimization of CAR construct design, including the choice of costimulatory and hinge/transmembrane domains.

Purpose of the Study:

• To generate and evaluate novel CD123-specific CAR T-cell constructs for potential AML treatment.
• To compare the efficacy and safety of different CAR T-cell designs, including those with various costimulatory and hinge/transmembrane domains.
• To identify the optimal CAR T-cell construct for further clinical investigation.

Main Methods:

• Generation of five lentiviral vectors encoding CD123-specific CARs with different hinge/transmembrane (H/TM) and costimulatory domains (CD28, 4-1BB) combined with the zeta (z) signaling domain.
• Evaluation of CAR T-cell transduction efficiency, expansion, phenotype, and target cell recognition.
• Assessment of CAR construct performance, including baseline signaling, anti-AML activity, and effector function.

Main Results:

• Transduction efficiency, expansion, phenotype, and target cell recognition did not significantly differ among the generated CD123-CAR T-cells.
• Several CAR constructs were eliminated due to significant baseline signaling (8.41BBz), decreased anti-AML activity (716.8.28z), or no improved effector function (28.28.41BBz).
• The 28.28z CAR T-cells were selected for further development due to higher CAR expression on the cell surface compared to 8.28z CAR T-cells.

Conclusions:

• The 28.28z CAR T-cell construct demonstrates favorable characteristics for targeting CD123 in AML.
• Optimization of CAR design, particularly the selection of appropriate costimulatory and H/TM domains, is crucial for developing effective CAR T-cell therapies.
• A clinical study (NCT04318678) evaluating the 28.28z CAR T-cells in AML patients is now open for enrollment.