Rademikibart monotherapy for moderate-to-severe atopic dermatitis in a 1-year, randomized phase II trial (S EASI DE CHINA): initial 2-week dosing, followed by 2-week or 4-week dosing

Abstract Background Rademikibart (CBP-201) is a potent, next-generation human monoclonal antibody optimized to bind with high affinity to interleukin-4 receptor subunit alpha. Objectives To evaluate rademikibart efficacy and safety, initially dosed every other week (Q2W), and Q2W or every fourth week (Q4W) from week 16, in Chinese adults/adolescents with moderate-to-severe atopic dermatitis (AD). Methods SEASIDE CHINA (NCT05017480) was a phase II randomized trial: stage 1 was a 16-week treatment period, and stage 2 comprised 36-week treatment and 8-week follow-up periods. The primary endpoint was the proportion of patients with a validated Investigator Global Assessment Scale for AD score of 0 or 1 (vIGA 0/1) and ≥ 2-point reduction from baseline at week 16. Overall, 330 patients were randomized 2 : 1 double-blind to receive subcutaneous rademikibart 600 mg on day 1 and 300 mg Q2W from week 2–14, or placebo. Predose at week 16, patients were assessed for minimal important change [≥ 50% improvement from baseline in Eczema Area and Severity Index score (EASI 50)] and rerandomized 1 : 1 double-blind to rademikibart 300 mg Q2W or Q4W. Results In stage 1, 29.0% of patients attained vIGA 0/1 and ≥ 2-point reduction with rademikibart Q2W (P < 0.001) at week 16, without plateauing, vs. 5.9% with placebo. Rapid, significant improvements were also observed with all other rating scales in stage 1, including ≥ 75% improvement from baseline in EASI (EASI 75) (58.6% vs. 22.6%) and ≥ 4-point reduction in Peak Pruritus Numeric Rating Scale (PP-NRS) (36.3% vs. 10.5%) with rademikibart Q2W vs. placebo, respectively, at week 16. In stage 2, week 16 EASI 50 responders from stage 1 continued to improve through week 52 when treated with rademikibart Q2W or Q4W, including vIGA response (Q2W 59.1%; Q4W 62.6%), EASI 75 (Q2W 84.6%; Q4W 84.8%), and ≥ 4-point reduction in PP-NRS (Q2W 60.4%; Q4W 70.3%). Most patients with improvements during rademikibart Q2W therapy at week 16 maintained these responses through week 52 in both the rademikibart Q2W and Q4W groups: vIGA (Q2W 78.0%; Q4W 87.1%), EASI 75 (Q2W 90.1%; Q4W 92.3%) and ≥ 4-point reduction in PP-NRS (Q2W 85.3%; Q4W 94.8%). Injection site reactions were grade 1 (mild). No serious treatment-emergent adverse events (TEAEs) were treatment related. Three patients discontinued rademikibart owing to TEAEs (AD flare, vitiligo, pregnancy). Conclusions Rademikibart Q2W induced rapid improvements in AD lesions and pruritus during the initial 16 weeks, which were maintained/improved further with rademikibart Q2W or Q4W across an additional 36 weeks. Rademikibart Q2W and Q4W were similarly efficacious and well tolerated. These findings are compatible with those from the published international phase II rademikibart trial, CBP-201-WW001.