A descriptive analysis of real-world oncology biosimilar use in Japan.

To describe patient and treatment characteristics associated with bevacizumab BS-Pfizer, rituximab BS-Pfizer and trastuzumab BS-Pfizer and their reference products in Japan. This retrospective observational study used an administrative claims database to identify patients with ≥1 biosimilar or reference product prescription from 2019 to 2022 for approved indications. Descriptive statistics were calculated. Overall, 14-39% of biosimilar-prescribed patients initiated therapy with reference products. Biosimilar utilization significantly increased from 2019 to 2022. The most-commonly prescribed concomitant class of therapy with biosimilars was antineoplastic therapy. Reference products were most frequently prescribed among the Japanese cohorts, but substantial and increasing proportions received biosimilars over time. Future studies should extend our initial insights to assess biosimilar clinical outcomes in Japanese settings.