ABSTRACT
Introduction Developing effective anticancer agents with a reasonable safety margin was difficult in the past. Many agents have entered clinical trials in cancer patients, particularly since the 1980s. However, most agents that have been developed since this time have failed at various stages of development due to unacceptable toxicity in preclinical studies or early clinical trials or to lack of efficacy on clinical endpoints, or because the toxicity appeared too difficult to manage in a larger patient population. With the emergence of targeted anticancer agents in the clinical development arena, it has become necessary to reconsider the way in which anticancer drug development is conducted. Targeted agents have necessitated a re-evaluation of the drug development template used in the development of conventional anticancer chemotherapy in the past.
