Chemo-Click: Receptor-Controlled and Bioorthogonal Chemokine Ligation for Real-Time Imaging of Drug-Resistant Leukemic B Cells.

Drug resistance in B cell leukemia is characterized by the coexpression of CXCR5 and CXCR3 chemokine receptors, making it a valuable biomarker for patient stratification. Herein, we report a novel platform of activatable chemokines to selectively image drug-resistant leukemic B cells for the first time. The C-terminal derivatization of the human chemokines CXCL13 and CXCL10 with bioorthogonal tetrazine-BODIPY and BCN groups retained binding and internalization via their cognate CXCR5 and CXCR3 receptors and enabled rapid fluorescence labeling of CXCR5+ CXCR3+ resistant B cells─but not drug-susceptible leukemic cells─via intracellular chemokine ligation. This modular chemical approach offers a versatile strategy for real-time immunophenotyping of cell populations with distinct chemokine profiles and will accelerate the design of new precision medicine tools to advance personalized therapies in blood tumors.