A critical appraisal of Japan's new drug approval process: a case study of FLT3-ITD inhibitor quizartinib.

In the last two decades, simultaneous global development of novel drugs become more common by conducting multiregional clinical trials. However, regulatory authorities of different regions often make different decisions on the approvals of the same new drugs. We would like to discuss the appropriateness of Japanese regulatory approach through a case study of quizartinib, a novel anti-leukemia drug developed in Japan. The pivotal clinical trial "QuANTUM-R" conducted in 19 countries showed a modest increase in median overall survival with quizartinib than the conventional chemotherapy. However, because several critical defects in this trial were pointed out by the United States Food and Drug Administration (US FDA) and the European Medicines Agency (EMA), quizartinib has not been approved in the US and Europe to date. On the contrary, the regulatory authority of Japan gave a notice of approval to quizartinib as a "standard of care", and the country becomes the sole country that granted market authorization. In our paper, we provide more detailed discussion about the methodology for scientific evaluation of the new drug.