Average Sales Price Erosion of Oncology Biologic Agents Following Biosimilar Entry Into The US Market

Abstract

Background: Biologic therapies are central in cancer management, but the high acquisition costs limit patient access. Biosimilars, which are equivalent in quality and safety to a reference biologic, are a cost-efficient alternative. Objective: To quantify the longitudinal impact of biosimilar market entry on the US Average Sales Price (ASP) of four reference oncology biologics and their biosimilars (rituximab, bevacizumab, trastuzumab, pegfilgrastim), including patterns of price erosion. Methods: ASP Pricing Files were retrieved from 2011Q2 to 2024Q4 to calculate the respective ASPs. The evolution of ASP, including erosion patterns, was assessed using three strategies. First, we calculated multiple metrics: differences in biosimilar-to-reference biologic ASP at biosimilar entry, biosimilar ASP percent decline since entry, cumulative percent increase in reference biologic ASP pre-biosimilar entry, average quarterly percent increase in reference biologic ASP pre-biosimilar entry, average quarterly percent decrease in reference biologic ASP post-biosimilar entry, and the ratio of reference biologic projected to actual ASP. Second, we visualized the ASP trends. Third, we determined the statistical significance of the observed ASP differences. Results: Three biosimilars were included for rituximab, four for bevacizumab, five for trastuzumab, and six for pegfilgrastim. At market entry, biosimilars showed ASPs 6.2%-23.2% lower than the reference biologic ASPs. Reductions from initial ASPs continued over time, with biosimilars' ASPs decreasing over time by 9.8%-92.2%. Prior to biosimilar market entry, reference biologic ASPs increased cumulatively by 37.9%-84.9%, with average quarterly increases of 0.92%-2.00%. This reversed post-biosimilar entry, with average quarterly decreases of 0.52%-10.00%. Projected ASPs, assuming no biosimilar entry, were higher than actual ASPs by 1.31-17.08 multiples. Pegfilgrastim exhibited a unique pattern, as biosimilars had and continued to have higher ASPs than reference biologic ASPs, with a 2.17-9.17 times increase in 2024Q2. Significant differences were observed in ASP trends for reference biologics pre- vs. post-biosimilar entry, except for trastuzumab; between reference biologics and biosimilars post-entry, except for pegfilgrastim; and among biosimilars. Conclusion: Biosimilar market entry has reduced ASPs of reference biologics and biosimilars, demonstrating their role in mitigating growth in total healthcare expenditures, particularly in the oncology setting. By lowering total treatment costs, biosimilars improve patient access and enhance the affordability of biologic therapy.