Moving Beyond Boundaries: Utilization of Longitudinal Exposure–Response Model for Bounded Outcome Score to Inform Decision Making in the Accelerated Drug Development Paradigm

The study utilized a model-informed drug development approach to evaluate the efficacy of ritlecitinib, a JAK3/TEC family kinases inhibitor, in treating alopecia areata, using data from 1,268 patients across phase 2b and 3 trials. The longitudinal exposure-response model effectively described the Severity of Alopecia Tool (SALT) score profile, identifying disease severity as the sole covariate impacting efficacy. It demonstrated that temporary treatment interruptions of up to 6 weeks do not significantly affect efficacy, while longer interruptions could lead to substantial hair regrowth loss. The study found that a 50 mg once-daily dose was effective, with higher doses approaching maximum efficacy. The model's predictive performance was validated, supporting dose selection and trial strategies, and offering a framework applicable to other conditions measured on a bounded scale.