The cost of delay: foregone public expenditure savings from delayed adalimumab biosimilar listing in Australia’s pharmaceutical benefits scheme

BACKGROUND: Adalimumab is among the highest-expenditure biologics under Australia's Pharmaceutical Benefits Scheme (PBS). Although the Pharmaceutical Benefits Advisory Committee recommended listing adalimumab biosimilars in 2018, reimbursement did not begin until April 2021. The public savings forgone through this delay have not been quantified. This study aimed to estimate the PBS savings achievable had biosimilars been listed earlier. RESEARCH DESIGN AND METHODS: We conducted a retrospective policy evaluation using nationwide PBS dispensing data across all nine subsidized indications from January 2016 to December 2025. Observed monthly expenditure was compared with a counterfactual assuming biosimilar listing in April 2019, with prices modeled on anniversary reductions, the first-new-brand statutory reduction, and subsequent price-disclosure cycles. A conservative price-reduction scenario was tested in sensitivity analyses. RESULTS: Earlier adalimumab biosimilar listing was estimated to generate cumulative savings of AU$334.6 million (~US$223.9 million;12.7% reduction). Savings remained substantial (AU$184.0 million; ~US$123.1 million; 7.0% reduction) under the conservative scenario. The greatest savings occurred in the highest-volume indications, with rheumatoid arthritis (30.6%) and Crohn's disease (25.2%) together exceeding half the total. CONCLUSIONS: Delayed listing produced substantial forgone savings. Timely translation of regulatory approval into reimbursement, alongside reimbursement design, jointly determine the public value of biosimilar competition.