An antibody-drug conjugate (ADC) composed of a monoclonal antibody against the ganglioside GD3, a surface antigen expressed on many malignant melanoma cells, and linked to an as of yet not fully elucidated chemotherapeutic agent, with potential antineoplastic activity. Upon administration of the ADC PF-06688992, the antibody moiety targets and binds to GD3 expressed on melanoma cells. Upon internalization, the chemotherapeutic agent specifically kills the GD3-positive cells. GD3 represents a major surface marker on most human melanoma cells and is not expressed on most other types of normal, healthy cells.