Inhibition of Epstein-Barr-virus-transformed human chronic lymphocytic leukaemic B cells with monoclonal-antibody-adriamycin (doxorubicin) conjugates

The anthracyclin antineoplastic agent doxorubicin (Adriamycin) was linked by four different methods of linkage to DalB02, an IgG1κ murine monoclonal antibody (mAb) against surface-associated antigens on human chronic lymphocytic leukaemia (CLL) B cells. All the four conjugates fully retained the immunoreactivity of the parent DalB02. When the inhibitory effect of these conjugates was evaluated in vitro against the target D10–1 cells (a clone derived from an Epstein-Barr-virus-transformed human CLL B cell line that binds DalB02) it was observed that one conjugate was more potent than the free drug but the others were not. When131I-labelled unmodified DalB02 and the131I-labelled DalB02-containing conjugate that was found to be potent were injected i.v. into nude mice bearing a subcutaneous D10–1 xenograft, the percentages of the injected dose (%ID) of both131I-DalB02 and the131I-DalB02-containing conjugate that localized in the tumour were much higher than the %ID of the respective preparations that localized in normal tissues of D10–1-xenografted mice. The systemic toxicity of the conjugate was less than that of the free drug. At an equitoxic dose level, this conjugate was a more effective inhibitor of established D10–1 xenografts than the free drug.