Forecasted infliximab concentrations during induction predict time to remission and sustained disease control of inflammatory bowel disease

Background: Infliximab (IFX) exposure is established as a predictive factor of pharmacokinetic (PK) origin in inflammatory bowel disease (IBD), and expert consensus is to achieve adequate exposure during induction to achieve and sustain remission. Methods: We retrospectively evaluated the performance of a Bayesian PK tool in IBD patients starting IFX. Trough IFX serum levels collected immediately before the third (at week 6) and fourth (at week 14) infusions were evaluated from 307 IBD patients (median age=17 years, 50 % females, 83 % with Crohn's disease). Forecasted IFX concentration at the fourth infusion were estimated using serum IFX, antibodies to IFX, albumin and weight determined immediately before the third infusion using population PK calculator with Bayesian prior. The outcome variable was a clinical & biochemical remission status achieved (CRP levels below 3 mg/L in presence of clinical remission). Statistics consisted of Kaplan Meier analysis with calculation of Hazard ratio (HR), and logistic regression. Results: IFX concentration above 15 mu g/mL immediately before the third infusion associated with shorter time to clinical & biochemical remission than concentration below 15 mu g/mL without reaching significance (163 +/- 14 days vs 200 +/- 16 days, respectively; p=0.052). However, using PK parameters at the third infusion, forecasted IFX concentrations above 10 mu g/mL immediately before the fourth infusion were significantly associated with a higher rate (HR=1.6 95 %CI: 1.1 to 2.1 p<0.01) and shorter time to remission (148 +/- 18 days vs 200 +/- 13 days p<0.01). In the presence of IFX concentration above 15 mu g/mL at the third infusion, there was a significant 2.5-fold higher likelihood of sustained clinical & biochemical remission status during maintenance as compared to IFX concentrations below 15 mu g/mL (p<0.01). Forecasted IFX level above 10 <mu>g/mL at fourth infusion associated with significantly 3.9-fold higher likelihood of clinical & biochemical remission as compared to forecasted IFX concentrations below 10 mu g/mL (p<0.01). Conclusions: These data further support that optimized IFX concentrations during induction are associated with enhanced disease control in IBD.