Bridging Gaps in Oncology: Comparative Analysis of Development and Approval Pathways for Anticancer Drugs and Companion Diagnostic in the United States and Japan.

Companion diagnostics (CDxs) are essential in personalized medicine for oncology, where specific genetic mutations drive treatment decisions. Some differences remain in the regulatory frameworks and approval processes for CDx between the United States (U.S.) and Japan. Data were collected from public databases for CDxs and anticancer drugs approved between January 1, 2014, and August 15, 2024, in both countries. The analysis included both initial drug approvals and supplemental approvals to examine the characteristics of approved CDxs and anticancer drugs, identify regional differences, compare development and approval timelines of CDxs and associated anticancer drugs in both countries, and assess the factors influencing approval timelines. CDx approval has increased significantly in both countries since 2014, driven by next-generation sequencing technologies, with 96 anticancer drug indications approved with CDx in the U.S. and 61 in Japan. In the U.S., drug approvals often preceded CDx approvals, influenced by post-marketing commitments (PMCs), whereas Japan tended to approve CDxs and drugs almost simultaneously. The median gap between CDx and drug approvals in the U.S. was 0 days (interquartile range (IQR): 0-391), indicating a broader range and often longer delay compared to 18 days (IQR: -52 to 0) in Japan, with a statistically significant difference between the two countries (p < 0.0001). Logistic regression analysis revealed orphan drug designation was significantly associated with CDx-related PMC in the U.S. (p = 0.042). These results highlight the need for greater regulatory harmonization between the U.S. and Japan to streamline approval processes and improve patient access to personalized treatments.