Background: As of December 2022, 22 of the 40 biosimilar approvals in the United States, are used for the treatment of cancer or for the supportive care of patients with cancer. Our organization is a network of community oncology practices, representing 107 oncologists at 76 locations across 17 states. Because our network faces formulary selection and reimbursement challenges related to a diverse payor mix across multiple states, we sought to see the impact of utilizing regional clinical pharmacists (RCPs) to assist with selection of the most cost-effective biosimilar products. Methods: In October 2021, our network initiated an RCP-driven biosimilar substitution program, whereby the RCP acts as a liaison between providers and financial teams to evaluate existing drug orders and their financial impact. We previously presented data on the financial impact to payors and providers before and after implementation of the program from 4/1/2021 to 4/1/2022. This study evaluates the one-year results following program implementation. Additionally, outcomes related to biosimilar utilization as well as financial impacts to payors, patients, and providers were assessed. Payor savings is defined as the difference of the calculated 80% Medicare ASP+6 for the administered biosimilar compared to the originator; patient savings is defined as the difference of the calculated 20% Medicare ASP+6 co-insurance for the administered biosimilar compared to the originator; provider savings is defined as the difference between the invoiced cost of the biosimilar compared to the originator. Results: By the end of 2022, preferred product utilization was achieved for >90% of bevacizumab, trastuzumab, and rituximab orders. Use of the preferred pegfilgrastim product increased from <20% in 4/2021 to >60% by 12/2022. Use of filgrastim biosimilar product increased from <75% in 4/2021 to >90% by 4/2022, then decreased to 55% by 12/2022 due to trending ASP. Payor preference prevented biosimilar switching in approximately 34% of cases. Conclusions: Use of institution-preferred biosimilar products increased across all agents in this study after implementation of the RCP-driven biosimilar substitution program, except for filgrastim. Significant cost savings were noted for payors, patients, and providers. Barriers to switching to institution-preferred products included non-medical switching requirements by payors, patient assistance and compassionate use programs, and patient and/or provider preferences.