Clinical trials and approval of anti-cancer agents.

Nowadays, drug development requires large-scale studies to show the real clinical benefit for the patients, which means recruiting a sufficient number of patients, even internationally. As global studies enable simultaneous delivery of new drugs and sharing of safety information around the world, multinational studies now account for around 20% of Japanese clinical studies. Until recently, drug development has been centered in Western countries, but interest in Asian regions has increased. In this environment, one important factor in drug development is ethnicity. Various cancers show regional patterns in their incidence, and some (such as liver cancer and gastric cancer) show high incidences in Asian countries. Ethnic factors including genetic differences, such as the CYP drug-metabolizing enzymes in the liver and gene mutations, may result in different drug responses in terms of efficacy and safety. Examples of ethnic differences in drug responses were seen with gefitinib, which showed a different efficacy data, and with sunitinib, showing a clearly different toxicity profile between the West and Asia. Therefore, ethnic differences need to be taken into account in the early phase of drug development, and Asian countries need to be involved early in clinical development. Asian collaboration among physicians and networks of specialists is also important, and there is good potential for successful establishment of the infrastructure needed for collaborative clinical trials. Establishment of a so-called third development center in Asian countries that will complement the USA and European centers is highly desired.