Relationship between serum trough levels and efficacy of brodalumab from a post hoc exploratory analysis of a Japanese study in patients with plaque psoriasis

Previous clinical studies have shown that efficacy and serum brodalumab levels are dose dependent in patients with psoriasis receiving the same dose of brodalumab during the study. This study aimed to investigate the association between dosage, serum levels, and efficacy of brodalumab in Japanese patients with plaque psoriasis with dosage variations during the study. This was a post hoc exploratory analysis of a 108‐week, multicenter, open‐label extension study, which changed into a post‐marketing surveillance study following brodalumab approval in Japan. Eligible patients with plaque psoriasis (n = 129) received brodalumab 140 mg every 4 weeks on Day 1; dosage change at physician’s discretion from 140 mg every 8 weeks to 210 mg every 2 weeks was permitted; patients switched to 210 mg every 2 weeks during the post‐marketing surveillance study. Exploratory endpoints included serum brodalumab levels at Weeks 28 and 108, its association with Psoriasis Area and Severity Index score, and Psoriasis Area and Severity Index score in patients receiving brodalumab 210 mg every 2 weeks at end of study. Median brodalumab trough levels were significantly higher (P < 0.05) at higher vs. lower dosages at Weeks 28 (n = 126) and 108 (n = 111) except for 140 mg every 2 weeks vs. 210 mg every 2 weeks at Week 108 and higher in patients with lower Psoriasis Area and Severity Index scores—significantly different only for Psoriasis Area and Severity Index score 0 vs. >2 at Week 28 (P = 0.0153). Of 100 patients receiving 210 mg every 2 weeks at end of study, 89% had a Psoriasis Area and Severity Index score ≤2. In patients with plaque psoriasis, brodalumab efficacy may depend upon sustained serum trough levels and can be restored by using the approved dose.