[Problems associated with molecular targeted drugs for cancer].

Molecular targeted drugs have been developed and have come to play a part in the standard treatment of cancers. However, issues such as the optimum dose, selection of patients, and verification of the molecular targets remain to be discussed, because unexpected clinical problems related to the clinical efficacy, adverse events, and development of resistance have appeared. Therefore, proof of principle (POP) studies and pharmacodynamic or pharmacogenomic research to explore new bio-markers for the drugs are essential for clinical progress. On the other hand, the higher cost of development and care must also be discussed as new problems.