Exposure–Response Analyses of Upadacitinib Efficacy in Phase II Trials in Rheumatoid Arthritis and Basis for Phase III Dose Selection

The relationships between upadacitinib, an oral selective Janus kinase 1 inhibitor, plasma exposures, and its efficacy (assessed by the American College of Rheumatology 20%/50%/70% responses over time) in moderate-to-severe active rheumatoid arthritis (RA) were characterized using data from 574 patients, on background methotrexate and inadequate response to methotrexate or anti-TNF therapy, from two phase II trials conducted with twice-daily dosing of an immediate-release formulation. The developed time-continuous Markov models were used to simulate efficacy of once-daily (q.d.). regimens of upadacitinib extended-release incorporating sources of uncertainty. Upadacitinib plasma concentrations associated with 15 and 30 mg extended-release q.d. doses were predicted to achieve that plateau of response across RA subpopulations. Results from these analyses provided the rationale that supported selection and de-risked evaluation of upadacitinib extended-release doses for the first time in >4,000 patients in five large phase III trials.