Clinical Utilization of Generic Drugs and Biosimilars for Ulcerative Colitis Treatment: Insights from a Nationwide Database Study in Japan.

Introduction: Limited data exist regarding the prevalence and clinical practice involving generic drugs and biosimilars for treating ulcerative colitis (UC) in Japan. We aimed to clarify the clinical usage of these generic drugs and biosimilars for UC treatment in Japan using a nationwide database. Methods: We collected data from 30,675 UC cases, along with their prescriptions for both generic drugs or biosimilars and their original counterparts, using a medical claim database provided by DeSC Healthcare, Inc. We calculated the prescription and penetration rates of generic drugs and biosimilars and demonstrated the transition of these rates. Additionally, the cumulative retention rates between infliximab originator and biosimilar were compared using the Kaplan-Meier method. Results: The prescription rate of generic mesalazine increased from approximately 10% in 2015 to over 30% in 2021. Although the prescription rate of generic molecular targeting drugs (MTDs) also increased from approximately 0.15% in 2014 to 2.5% in 2021, the increment was lower than that of generic mesalazine. The penetration rates of generic 5-aminosalicylic acid and tacrolimus ranged from over 30% to approximately 50%. Infliximab biosimilar achieved an approximate 20% penetration rate, whereas adalimumab achieved <5%. The cumulative retention rates did not differ between infliximab originator and biosimilar. Conclusions: The penetration rates of generics and biosimilars for UC treatment are relatively low compared with those for treatment in other fields and the goal of the Ministry of Health, Labor, and Welfare. Several countermeasures are necessary for the widespread use of generics and biosimilars, ultimately contributing to cost-effective and sustainable healthcare delivery.