Population Pharmacokinetic and Exposure–Response Modeling to Inform Risankizumab Dose Selection in Patients With Ulcerative Colitis

Data from phase IIb/III and phase III studies were used to characterize the population pharmacokinetics of risankizumab and its exposure-response relationships for efficacy and safety in ulcerative colitis (UC) patients. A two-compartment model with first-order absorption and elimination accurately described risankizumab pharmacokinetics. Although certain covariates, namely, body weight, serum albumin, fecal calprotectin, sex, corticosteroid use, advanced therapy inadequate response, and pancolitis, were statistically correlated with risankizumab clearance, their impact on exposure was not clinically meaningful for efficacy or safety. Phase II exposure-response analyses demonstrated that the 1,200 mg intravenous (IV) induction dose at Weeks 0, 4, and 8 achieved near maximal response for all efficacy end points, with suboptimal efficacy from the 600 mg and little added benefit from the 1,800 mg regimens, justifying 1,200 mg IV as the induction dose in the phase III study. Phase III exposure-response analyses for efficacy during induction showed statistically significant exposure-response relationships at Week 12 following 1,200 mg IV at Weeks 0, 4, and 8, in line with phase IIb results. Exposure-response analyses for maintenance demonstrated modest improvement in Week 52 efficacy when increasing the subcutaneous dose from 180 mg to 360 mg with largely overlapping confidence intervals. Exposure-response analyses for safety indicated no apparent exposure-dependent safety events over the induction or maintenance treatment. Based on these results, the recommended dosing regimen for risankizumab in UC patients is 1,200 mg IV at Weeks 0, 4, and 8, followed by 180 mg or 360 mg subcutaneously at Week 12 and every 8 weeks thereafter.