Microdose clinical trial by use of radioisotope and perspective of its possible utilization in drug development

Many promising PET tracers have been developed by the progress of molecular imaging research, and new era could be opened by clinical trials using investigational products labeled by RI. Guidance for microdose clinical trial issued by MHLW in June, 2008, is the regulatory basis to develop PET tracer under clinical trial by the pharmaceutical affairs law. In this review, the discussion from the aspect of regulatory science is highlighted, particularly, on the topics of guidance for microdose and exploratory IND study including sub-therapeutic dose (type II) and therapeutic dose (type III), the revised GMP for investigational product including RI-labeled product, and to ward guidance for microdose clinical trial for biological product. Finally, the US FDA guidance developing medical imaging drug including biological product is introduced, and then perspective of possible utilization of in vivo radiopharmaceutical agents in drug development is discussed. (author)