P1044 Mirikizumab Pharmacokinetics and Exposure-Response in a Phase 2 Study in Patients With Moderately to Severely Active Crohn’s Disease

Abstract

Abstract Background Mirikizumab (miri) is a humanized anti–interleukin-23-p19 monoclonal antibody approved for the treatment of ulcerative colitis (UC) and under development for Crohn’s disease (CD). This analysis characterises miri pharmacokinetics (PK) and the relationship between miri exposure and efficacy response using data from a phase 2 trial in adults with moderately to severely active CD. Methods AMAG was a randomised, double-blind, placebo-controlled trial conducted in 14 countries. Patients received placebo, miri 200 mg, 600 mg, or 1000 mg as induction regimens administered intravenously (IV) every 4 weeks (Q4W) through Week 12, followed by 36 weeks of maintenance treatment with continuous treatment of miri 200 mg, 600 mg, or 1000 mg IV or miri 300 mg administered subcutaneously (SC) Q4W. PK parameters were analysed by non-linear mixed-effects modelling. Covariate effects on miri exposure were evaluated using simulation-based estimations. Exposure-response (ER) for patients achieving endoscopic response by Simple Endoscopic Score for Crohn’s Disease (SES-CD) at Weeks 12 and 52 were assessed using logistic regression models. Results 186 patients were included. The estimated systemic clearance (CL), central volume of distribution (V), and SC bioavailability (F) were 0.022 L/hr, 3.31 L, and 33.4%, respectively. Lower baseline values for SES-CD (indicative of a less severe CD) were associated with reduced CL. Lower body weight and higher albumin levels were also associated with reduced CL. Higher body weight was associated with higher V and lower baseline body mass index correlated with higher SC F. Impacts on PK parameters were small relative to random variability and not considered clinically relevant. The model-based ER analyses for endoscopic response probability at Week 12 detected a significant treatment effect relative to placebo (p<0.001) and a significant ER (p=0.001) in a dose range of 200-1000 mg. The ER analyses indicated near maximal efficacy for IV dose between 600 mg and 1000 mg during the Induction Period. There was no significant relationship between miri exposure and the probability of achieving endoscopic response by SES-CD at Week 52, indicating exposures produced by the maintenance doses provided similar efficacy. Conclusion Miri PK characteristics in adults with active CD were consistent with miri UC studies. Overall, none of the covariates identified as being significantly correlated with miri PK parameters were considered clinically relevant. No patient factors evaluated in this analysis justify dose adjustment. These findings support the miri induction dose 900 mg IV Q4W and maintenance dose 300 mg SC Q4W selected for phase 3 CD study.