Sullivan, SeanLi, Kevin Haokun2025-08-012025-08-012025Li_washington_0250O_28377.pdfhttps://hdl.handle.net/1773/53300Thesis (Master's)--University of Washington, 2025Background: The recent expansion of Food and Drug Administration (FDA)-approved treatment options for moderate-to-severe atopic dermatitis (AD) has notably improved clinical management options. With the availability of these novel therapies, data on frequency of therapy switching and differences in healthcare resource utilization (HCRU) and costs between switchers and non-switchers are limited.Objective: To evaluate the frequency of treatment switching from first- to second-line systemic targeted therapies and compare HCRU and costs between switchers and non-switchers among commercially insured US patients with moderate-to-severe AD. Methods: We conducted a retrospective cohort study using MarketScan health insurance claims data. Adult patients with AD initiating a first systemic targeted therapy (index date) between January 1, 2022 and December 31, 2022 were identified and followed for at least one year from index date. Two cohorts were classified based on whether switching occurred over follow-up, which was defined as discontinuation of first systemic targeted therapy and initiation of second systemic targeted therapy. All-cause and AD-related HCRU outcomes, including hospitalizations, emergency department (ED) visits, and outpatient services, were compared between switchers and non-switchers during the follow-up period. Total healthcare costs were also evaluated, categorized by medical and drug costs. Statistical significance was defined as a two-sided p-value of < 0.05. Results: After a year following the initiation of first-line systemic targeted therapy, 466 (5.8%) switched to second-line systemic targeted therapy among the 8,063 patients with moderate-to-severe AD included in this study. Nearly all switchers (96.4%) had at least one AD-related outpatient service compared to 82.8% for non-switchers (p < 0.0001), and the mean number of visits was higher among switchers compared to non-switchers (5.12 vs. 3.20, p < 0.0001). AD-related hospitalizations and ED visits were rare. Mean total AD-related healthcare costs also were significantly higher among switchers compared to non-switchers ($63,245 vs. $53,004; p < 0.0001), with drug costs accounting for approximately 99% of AD-related healthcare expenditures in both groups. Discussion: We found a small proportion (5.8%) of patients switched from first- to second-line systemic targeted therapy after a median follow-up of approximately one year. Patients who switched therapies incurred significantly higher AD-related outpatient service use and total healthcare costs compared to non-switchers, which may potentially reflect either worsening disease severity or inadequate response or intolerability to first-line therapy. These findings emphasize the increased importance of personalized considerations for the selection of first-line systemic targeted therapy for patients with moderate-to-severe AD to reduce downstream economic burden. As additional therapies become available, future research exploring reasons for treatment switching and patient factors influencing response will be critical to guide clinical and formulary decision-making in this evolving treatment landscape.application/pdfen-USnoneatopic dermatitishealth economics and outcomes researchhealthcare resource utilizationswitchingsystemic targeted therapiesHealth care managementPharmaceutical sciencesThesis