BACKGROUND: Darolutamide, a structurally distinct androgen receptor inhibitor approved for the treatment of men with nonmetastatic castration-resistant prostate cancer (nmCRPC), has been shown to increase metastasis-free survival among men with nmCRPC compared with placebo. This treatment has a novel chemical structure that may also have safety, tolerability, and efficacy advantages for men with nmCRPC. OBJECTIVE: To estimate the projected budget impact of including darolutamide on a U.S. payer formulary as a treatment option for men with nmCRPC. METHODS: A budget impact model was developed to evaluate darolutamide for nmCRPC for a hypothetical 1-million-member plan over a 5-year period. Costs (drug acquisition, drug administration, and treatment-related adverse events [AEs]) were estimated for 2 scenarios: with and without darolutamide treatment for nmCRPC. The budget impact of darolutamide was calculated as the difference in costs for these 2 scenarios. An analysis for high-risk nmCRPC also was conducted. The model included treatments recommended by the National Comprehensive Cancer Network (e.g., apalutamide and enzalutamide) and potential comparators that are used but are not specifically indicated for nmCRPC. All treatments were assumed to be administered in combination with a weighted average androgen deprivation therapy comparator (consisting of luteinizing hormone-releasing hormone [LHRH] agonists, LHRH antagonists, and first-generation antiandrogens). Market share estimates were derived from interviews with physicians treating men with nmCRPC. The model includes grade 3-4 AEs, and the rates were obtained from clinical trial data. Costs were taken from publicly available sources and varied in a one-way sensitivity analysis. RESULTS: For a plan with 1 million lives, there were approximately 90 incident cases of nmCRPC (46 high risk) each year, with 332 (109 high risk) treatment-eligible cases by year 5. Darolutamide's market share increased from 3.6% in year 1 to 18% in year 5. Given the utilization of other agents, introducing darolutamide along with other targeted therapies was predicted to increase the total budget by $158,640 ($0.0132 per member per month [PMPM]) in year 1, which decreased over time to a cost savings of $149,240 ($0.0124 PMPM) by year 5. The scenario with darolutamide showed reduced AE costs each year. Similar results were observed for the high-risk nmCRPC population. CONCLUSIONS: Adding darolutamide to a U.S. payer formulary for the treatment of nmCRPC can result in a manageable increase in the budget that is partly offset by AE costs in the first 4 years, followed by a cost savings by year 5. DISCLOSURES: This study was conducted by RTI Health Solutions under the direction of Bayer U.S. and was funded by Bayer U.S., which was involved in the design of the study; collection, analysis, and interpretation of the data; writing of the report; and the decision to submit the report for publication. Miles and Purser (and/or their institutions) are employees of RTI Health Solutions and received research funding from Bayer U.S. to develop the budget impact model. Appukkuttan and Farej are employees of Bayer U.S. Wen was an employee of Bayer U.S. at the time of the study. This study was presented as a poster at the AMCP Virtual Learning Event, April 20-24, 2020.