Dacetuzumab, a humanized mAb targeting the CD40 antigen, is in development by Seattle Genetics Inc and licensee Genentech Inc for the potential treatment of hematological malignancies. The CD40 antigen is a highly expressed cell surface transmembrane protein that is present in normal B-cells. Experiments using blocking antibodies for the CD40 ligand demonstrated that CD40 signaling may play a role in the development and maintenance of B-cell hematological malignancies and some solid tumors. In vitro, dacetuzumab exhibited antitumor activity against several B-cell lymphoma and multiple myeloma (MM) cell lines, and induced direct apoptosis as well as the engagement of effective antibody-dependent cell-mediated cytotoxicity. In vivo, dacetuzumab demonstrated enhanced antitumor efficacy in combination with other mAbs and chemotherapeutic agents; many of these combinations are now being tested clinically. Early clinical trials have evaluated the pharmacokinetics, safety and efficacy of dacetuzumab monotherapy in patients with relapsed/refractory B-cell lymphomas or MM. Targeting CD40 with dacetuzumab resulted in modest antitumor activity in B-cell lymphomas and, to a lesser extent, in MM. In particular, patients with diffuse large B-cell lymphoma responded well to dacetuzumab; the drug is being pursued for this indication in phase II trials.