Half-life-extended monoclonal antibody APG777 for atopic dermatitis: Design of the phase 2 APEX study

Introduction: Current treatments for moderate-to-severe atopic dermatitis (AD) include topical and systemic therapies. The latter includes monoclonal antibodies (mAbs) targeting the IL-13 pathway, which is implicated in AD pathophysiology. While currently available mAbs directed against the IL-13 pathway have demonstrated efficacy for AD, they require ongoing injections every 2 or 4 weeks. APG777 is a humanized anti-IL-13 mAb that binds IL-13 and blocks downstream signaling mediated by the IL-13Rα1/IL-4Rα complex. APG777 contains amino acid modifications designed to extend plasma half-life through increased FcRn-mediated antibody recycling. Results from a phase 1 study in healthy participants suggest a favorable safety and PK/PD profile for APG777, as well as a half-life of 77 days. Methods: APEX (NCT06395948) is a 2-part, multicenter, phase 2, randomized, double-blinded, placebo-controlled clinical trial evaluating the efficacy and safety of APG777 in adults with moderate-to-severe AD. Adults (≥18 years of age) are eligible to participate if they have a diagnosis of AD for ≥1 year prior to screening and exhibit moderate-to-severe AD (EASI ≥16, IGA ≥3, BSA ≥10%) at both screening and baseline visits. Part A of the study (proof-of-concept) is evaluating the efficacy and safety of one induction dose regimen of APG777 compared with placebo over 16 weeks; this is followed by a 36-week maintenance period. Part B (dose-regimen finding) will evaluate different dose regimens of APG777 compared with placebo over 16 weeks followed by a 36-week maintenance period. Participants completing the maintenance period of Part A or B of the study will be eligible to enroll in a separate long-term extension study or enter the post-treatment follow-up period (up to 52 weeks). The primary outcome measure for the study is the percentage change from Baseline to Week 16 in the Eczema Area and Severity Index (EASI). The APEX study is currently enrolling.