The humanized CD40 antibody SGN-40 demonstrates pre-clinical activity that is enhanced by lenalidomide in chronic lymphocytic leukaemia

Antibody-based therapies, such as rituximab and alemtuzumab, have contributed significantly to the treatment of Chronic Lymphocytic leukaemia (CLL). The CD40 antigen is expressed predominantly on B-cells and represents a potential target for immune-based therapies. SGN-40 is a humanized IgG1 monoclonal antibody currently in Phase I/II clinical trials for indolent lymphomas, diffuse large B cell lymphomas and Multiple Myeloma. Its biological effect on CLL cells has not been studied. The present study demonstrated that SGN-40 mediated modest apoptosis in a subset of patients with secondary cross-linking but did not mediate complement-dependent cytotoxicity. SGN-40 also mediated antibody-dependent cellular cytotoxicity (ADCC) predominantly through natural killer (NK) cells. Previous studies by our group and others have demonstrated that lenalidomide upregulates CD40 expression on primary B CLL cells and activates NK-cells. We therefore examined for the combinatorial effect of lenalidomide and SGN-40 and demonstrated that both enhanced direct apoptosis and ADCC against primary CLL B cells. These data together provide justification for clinical trials of SGN-40 and lenalidomide in combination for CLL therapy.