CXCR4 and neoplasm: The lead ADC presents a novel MoA that: 1) limits tumour and leucocyte mobilization, 2) reduces antigen-dependent ADC clearance (as shown by the enhanced exposure in HuCXCR4KI mice) and 3) mitigates toxicity to quiescent CXCR4+ normal tissues, including HSC/LSK progenitors.