Much progress has been made during the last few decades in the treatment of malignancies. Many types of cancer cells comprising the tumor mass carry molecular markers that are not expressed or are expressed at much lower levels in normal cells. These findings provide new leads to drug design and development of therapeutic strategies involving monoclonal antibodies (mAbs) or related antibody drugs to treat malignancies. This article reviews recent advances in this targeting approach with a focus on the evolution and current use of prospective antibody drugs as effective ways to treat cancer. Additionally, the development of prospective antibody-drug conjugates will also be briefly described.