This study examines the impact of biosimilar competition on out-of-pocket (OOP) costs for patients using biologic drugs. The research analyzed claims data from 1.7 million outpatient visits of 190,364 individuals using seven biologics between 2009 and 2022. The study found that annual OOP costs did not decrease after biosimilar competition began, and OOP costs were similar for biosimilars and their reference biologics. While biosimilar claims were more likely to have nonzero OOP costs, they had 8% lower mean nonzero OOP costs compared to reference biologics. These findings varied by drug, with some drugs showing lower OOP costs after biosimilar entry, while others did not. The study highlights that biosimilar competition has not consistently led to lower OOP costs for commercially insured patients, suggesting the need for targeted policy interventions to ensure that savings from biosimilar competition translate into improved affordability for patients. The study also notes that savings from biosimilar competition may not directly impact OOP costs due to factors such as insurance benefit design, reimbursement rates, and billing rules. The findings suggest that while biosimilars have contributed to overall healthcare cost savings, they may not always reduce the OOP costs for patients using biologics. The study underscores the importance of ensuring that biosimilar competition leads to better affordability and access for patients who need these medications.This study examines the impact of biosimilar competition on out-of-pocket (OOP) costs for patients using biologic drugs. The research analyzed claims data from 1.7 million outpatient visits of 190,364 individuals using seven biologics between 2009 and 2022. The study found that annual OOP costs did not decrease after biosimilar competition began, and OOP costs were similar for biosimilars and their reference biologics. While biosimilar claims were more likely to have nonzero OOP costs, they had 8% lower mean nonzero OOP costs compared to reference biologics. These findings varied by drug, with some drugs showing lower OOP costs after biosimilar entry, while others did not. The study highlights that biosimilar competition has not consistently led to lower OOP costs for commercially insured patients, suggesting the need for targeted policy interventions to ensure that savings from biosimilar competition translate into improved affordability for patients. The study also notes that savings from biosimilar competition may not directly impact OOP costs due to factors such as insurance benefit design, reimbursement rates, and billing rules. The findings suggest that while biosimilars have contributed to overall healthcare cost savings, they may not always reduce the OOP costs for patients using biologics. The study underscores the importance of ensuring that biosimilar competition leads to better affordability and access for patients who need these medications.