An antibody-drug conjugate (ADC) consisting of a monoclonal antibody directed against human cell surface antigen CD47 conjugated to an as of yet not fully elucidated toxin, with potential antineoplastic activity. Upon administration of SGN-CD47M, the anti-CD47 monoclonal antibody moiety targets and binds to CD47 on tumor cell surfaces; upon internalization, the toxin moiety kills tumor cells through a mechanism of action that has not been elucidated. CD47, also called integrin-associated protein (IAP), is a tumor-associated antigen (TAA) expressed on normal, healthy hematopoietic stem cells (HSCs) and overexpressed on the surface of a variety of cancer cells.