OBJECTIVES: Understanding trends in biosimilar adoption by specialty may advance provider and patient education while optimizing cost savings and health outcomes. Previous evaluations focused on surveys of specialty providers; however, we sought to evaluate utilization of reference versus biosimilar products by specialty across the US over five years (2019-2023).

METHODS: We analyzed data from Trisus Medication Compare (The Craneware Group, Edinburgh, UK) between 1/1/2019-12/25/2023 to identify encounters in eleven specialties (dermatology, endocrinology, gastroenterology, hematology, infectious diseases, nephrology, neurology, oncology, ophthalmology, rheumatology, and solid organ transplant) with a reference or biosimilar product dispensation for filgrastim, pegfilgrastim, infliximab, rituximab, bevacizumab, trastuzumab, insulin glargine, epoetin alfa, and ranibizumab. Analyses included yearly use trends overall and by specialty, age, and state.

RESULTS: Dispensations from 1,782,569 patient encounters (reference, n=1,256,156; biosimilar, n=526,413) were included. Endocrinology (n=657,599), oncology (n=591,777), and gastroenterology (n=191,596) were most frequent; ophthalmology (n=1,824) and transplant (n=1,550) were infrequent. Biosimilar use was higher in non-academic centers (61.2% vs 55.7% with reference, p=0.0001) and outpatient settings (71.5% v. 52.1% with reference, p=0.0001). Biosimilar use was lower for pediatrics based on included indications (reference: 4.1%, biosimilar: 2.6%; p=0.0001), consistent across specialties. Biosimilar use increased annually overall (2019: 15.9%; 2020: 22.2%; 2021: 33.3%; 2022: 38.4%; 2023: 41.0%) and by specialty, except ophthalmology. Epoetin alfa use drove infectious diseases (76.5%), nephrology (62.4%), and hematology (55.4%) to have the highest biosimilar adoption rates, while ophthalmology (no use) and endocrinology (5.0%) had the lowest. Oregon, Montana, South Dakota, and Michigan had the highest biosimilar adoption rates (>45%), while New Hampshire, Alabama, and Mississippi had the lowest (<15%).

CONCLUSIONS: National data show increasing biosimilar adoption across specialty therapeutic areas, except ophthalmology, over a five-year period.