CD22 and plasma cell myeloma: The mean receptor numbers per cell line ranged between 2,800 and 6,194 which is within the range of clinically useful ADCs: 4,695 for CD22, the target of approved ADC inotuzumab ozogamicin19; 1000–10,000 for CD33, the target of gemtuzumab ozogamicin15,21; 1000–9000 for CD54, the target of the therapeutic antibody BI-505, on the surface of myeloma cells18,19.