Straight to Phase <scp>III</scp> : Model‐Informed Approach Speeds Depemokimab Clinical Development in Interleukin‐5‐Driven Diseases

IL-5, a key mediator of type 2 inflammation, underlies various diseases, including severe asthma, CRSwNP, EGPA, and HES. Reduction in blood eosinophil count (BEC), a biomarker of IL-5 activity, is commonly used to evaluate the efficacy of anti-IL-5 biologic therapies. Model-informed drug development (MIDD) and quantitative decision making (QDM) were used to shorten the clinical development of depemokimab (an ultra-long-acting anti-IL-5 biologic). A Bayesian nonlinear mixed effects dose-time response model predicted the depemokimab dose in severe asthma achieving comparable BEC reductions to those observed in mepolizumab (an approved anti-IL-5 biologic) Phase III MUSCA and MENSA trials. Prespecified QDM go/no-go criteria were applied to assess success probability. Phase IIb efficacy-based trial simulations were conducted using negative binomial distribution to simulate individual annualized exacerbation rate. A depemokimab PK/PD (BEC) model predicted Phase III trial doses in CRSwNP/EGPA/HES. Single depemokimab doses were well-described by the Bayesian model; a single depemokimab dose ≥ 60 mg had probability ≥ 80% of exceeding Minimum (78%; MUSCA) and ≥ 10% probability of exceeding Target (84%; MENSA) values for trough BEC reduction from baseline vs. placebo. Clinical trial simulations demonstrated < 3% probability of more precise estimation of the Phase III dosing regimen with a conventional efficacy-based dose-ranging study. Depemokimab 100 mg for severe asthma/CRSwNP and 200 mg for EGPA/HES, administered subcutaneously every 26 weeks, were selected for Phase III trials. MIDD and QDM shortened the depemokimab development program by 2-3 years, emphasizing the potential of this approach for progressing new therapies from Phase I directly to Phase III.