LAUSR

Importance Given the possible treatment modalities in psoriasis management, little is known about whether drug monitoring is associated with response rate. Objective To determine whether drug monitoring is associated with response to brodalumab therapy. Design A multicenter case series study of patients with psoriasis treated with brodalumab whose treatment with previous IL-17A inhibitor therapy failed. Patients were recruited from the Departments of Dermatology at Gentofte and Aarhus University Hospitals, Denmark, between 2018 and 2020. Patient visits were conducted after 4 and 12 weeks of therapy. Patients not achieving Psoriasis Area and Severity Index 75% improvement from baseline (PASI 75) after 12 weeks were discontinued and considered nonresponders. Patients maintaining PASI 75 response were followed up for up to 52 weeks. Exposure Treatment with brodalumab, 210 mg, at weeks 0, 1, 2, then every 2 weeks. Main Outcomes and Measures Outcome measures were PASI reductions vs brodalumab levels and antibrodalumab antibodies. Results Twenty patients with psoriasis (13 [65%] were male; median age, 50 years [range, 19-66 years]) were included. After 12 weeks of therapy, patients with quantifiable levels of brodalumab (≥0.05 μg/mL) experienced significantly higher PASI reductions than those without (median, 93%; range, 61%-100% vs median, -3; range, -49% to 94%, respectively; P = .006). After 12 weeks of therapy, 4 of 5 patients (80%) not achieving PASI 75 had subquantifiable drug levels (<0.05 μg/mL), although this finding was seen for only 3 of 14 PASI 75 responders (21%). None of 7 patients (35%) with subquantifiable drug levels after 12 weeks of therapy maintained response. No antibrodalumab antibodies were detected in any of the tested samples. Conclusions and Relevance Results of this case series study suggest that circulating brodalumab level is a factor associated with clinical treatment response. Monitoring patient levels of circulating brodalumab may aid clinical decision-making and help prevent ineffective therapy.