Added Therapeutic Benefits of Top-Selling Drugs in Japan: A Cross-Sectional Study Using Health Technology Assessment

It is unclear whether Japanese top-selling drugs have meaningful added therapeutic benefits to justify their high sales. This question is relevant as Japan's healthcare costs are rising consistently, particularly due to increasing drug prices. This cross-sectional study evaluated the added therapeutic benefits of Japan's top-selling drugs in 2021 using ratings from established health technology assessment (HTA) agencies in Canada, France, and Germany. Drug characteristics and benefit ratings were obtained from public databases and HTA agencies, following the established method. Overall, added therapeutic benefit ratings were categorized as binary (high or low). Of 51 identified top-selling drugs in Japan, 43 (86%) had at least one rating from three agencies. Notably, 20 (47%) received low added therapeutic benefit ratings even in our optimistic scenario. Low ratings were more common among small-molecule drugs 15/20 (75%), while high ratings were predominant among biologics 14/23 (61%). Oncology drugs represented the largest category in both high 9/23 (39%) and low 5/20 (25%) groups. Interestingly, 9 drugs (9/16; 56%) approved between 2011 and 2021 received low ratings, compared to 41% (11/27) of those approved before 2011. Additionally, 70% of high-benefit drugs received at least one expedited review, whereas this was 35% for low-benefit drugs. Our findings revealed that many top-selling drugs in Japan had low added therapeutic benefits. Utilizing HTA evaluation frameworks provides valuable insights, particularly in prioritizing drugs based on added therapeutic benefits. While full implementation of such a system in Japan requires further consideration, strengthening HTA processes could help ensure sustainable healthcare costs.