Molecular targeted therapy: a strategy of disillusions or optimism?

Cytotoxic drugs were designed to kill tumor cells, whereas agents of molecular targeted therapy inhibit various molecular functions of the tumor cell. Consequently, their toxicity profiles also differ. Molecular targeted agents, except for monoclonal antibodies, are enumerated here in three classes: compounds active extracellularly, extra/intracellularly, and intracellularly. Although no major breakthrough has occurred in the drug treatment of neoplastic diseases yet, such compounds as trastuzumab, cetuximab, bevacizumab, gefitinib, erlotinib, imatinib, and bortezomib have shown considerable clinical promise. Major obstacles to the further development of molecular targeted compounds are described. The use of different endpoints, positron emission tomography for evaluation, and predictive genetic markers are recommended. Combination therapy with cytotoxic drugs and studies in an adjuvant setting are also recommended. It is concluded that cautious optimism about the future of molecular targeted therapy is reasonable.