CD123 / CD33

Class

Sequential dual-target CAR-T cell therapy

Pathway

T-cell-mediated cytotoxicity against CD33-expressing and CD123-expressing AML blasts

CD123 and CD33 are two surface proteins frequently overexpressed on the malignant blast cells of acute myeloid leukemia (AML). CD33 is a myeloid lineage marker also present on normal white blood cells and their precursors, while CD123 is the alpha subunit of the interleukin-3 receptor and is notably enriched on leukemic stem cells, the reservoir of cells thought to drive relapse. Chimeric antigen receptor (CAR) T-cell therapy re-engineers a patient's own T lymphocytes to recognize a chosen surface antigen and kill any cell displaying it, bypassing the need for conventional antigen presentation. Targeting either CD33 or CD123 alone with a CAR-T product risks disease relapse if leukemic cells downregulate or lose that single antigen, a phenomenon called antigen escape. A sequential dual-target approach uses CAR-T cells directed against both antigens, administered in a staged fashion, so that leukemic populations evading one target remain vulnerable to the other. Because both antigens are also expressed, to varying degrees, on healthy myeloid and progenitor cells, this strategy must balance broadening anti-leukemic coverage against the risk of depleting normal blood-forming cells. This mechanism is broadly relevant to relapsed or refractory AML, where clonal heterogeneity and stem-cell-driven regrowth are major obstacles to durable remission.