The main steps in the development of anticancer agents.

The development of new anticancer agents is a long-term process, which involves the acquisition of new compounds, screening for antitumor activity, production and formulation, animal toxicology and finally, evaluation of toxicity and antitumor activity of the compound in man (Table I). In this paper, the main steps in the early development of new cytotoxic agents up to phase II clinical studies will be discussed. However, clinical phase III-IV trails, where the efficacy of the drug has been proven, should be dealt with separately.