Low Generic Drug Penetration for Expensive Oral Molecular Targeted Agents: An Experience with Generic Imatinib in Japan.

Objective Generic imatinib has been available for more than a decade, but it remains underutilized in Japan. This study investigated the market trends of imatinib in Japan and explored the reasons for the predominant prescription of Gleevec®. Methods All-cause healthcare costs and sales data for generic drugs were obtained from publicly available sources. The actual market share of imatinib, which is not available from public sources, was provided by OHARA Pharmaceutical. The estimated cost reduction resulting from the prescription of the most inexpensive generic drugs was simulated according to the conditions forecasted by Japan's MHLW. Results A generic form of Gleevec® became available in 2014 at 50-55% of the original price. However, Gleevec® remained the market leader, holding 72% of the market share in fiscal year (FY) 2022, owing to the unique universal health insurance and high-cost reimbursement systems that alleviate the financial burden on patients. In October 2024, Japan implemented a Selective Treatment Fee (SENTEI RYOYOHI), which requires patients who opt for the brand-name Gleevec® over its generic counterpart to pay 25% of the cost difference between Gleevec® and the most expensive generic imatinib. Conclusion Although certain patients who opt to use Gleevec® rather than generic imatinib will experience an increase in medical costs, the Selective Care System is an effective solution to protect the endangered national healthcare system in Japan. Ensuring that both individual medical expenditures and net gross national medical expenditures are urgently needed.