This retrospective cohort study examined market dynamics and financial implications of biosimilar entry for bevacizumab, rituximab, and trastuzumab among 14,655 patients in commercial and Medicare Part B insurance, using claims data from July 2019 to December 2024.
Biosimilar-only use (59.4% of patients) was associated with $3,820 lower mean monthly payer costs and $39.50 lower mean monthly out-of-pocket costs vs. reference product-only use; reference product average sales price fell 3.8% annually and market share dropped ~30–31.5% per year after biosimilar entry.
Retrospective claims-based design limits causal inference; data restricted to commercially insured and Medicare Part B patients, excluding Medicaid and uninsured; biosimilar entry timing differed across the three agents, complicating pooled trend analysis.
Biosimilars for bevacizumab, rituximab, and trastuzumab meaningfully reduce costs for both payers and patients without evidence of compromised access. Clinicians and health systems should favor biosimilar initiation as the default to maximize affordability benefits.
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