As cancer is resulted from molecular genetic defects, many drugs were designed to reach at the affected site that block the cancer growth by interfering with particular molecules included in carcinogenesis and they may be more effective than conventional treatments and less harmful to normal cells. these are called targeted anticancer therapy and classified into two classes: those that attack cell surface antigens or receptors which are monoclonal antibodies, or those that enter cells and occupy critical enzymes which is synthetic small molecules .