Application of a precision-dosing model to a real-world cohort of patients on infliximab maintenance therapy: Drug usage and cost analysis.

Precision-dosing models forecast infliximab doses to achieve targeted trough concentrations in patients with inflammatory bowel disease (IBD). These models have shown to reduce non-response and improve patient outcomes. We compared infliximab doses determined by iDOSE® precision-dosing with standard dosing, and the associated drug costs, in patients with IBD. In this retrospective study, IBD patients treated with infliximab every eight weeks at 5 mg/kg were included. An infliximab dose was named dose X if three previous infliximab doses, laboratory values including trough infliximab concentrations and the patient's weight were recorded. The actual dose X was compared to an iDOSE®-predicted dose X. Net drug use and costs were evaluated. 174 patients - 56% male, median age 36 (IQR 29-47) years; 135 Crohn's disease and 31 ulcerative colitis were included with 417 dose X recordings. Median prior infliximab therapy was 2 (0-4) years. Comparing actual dose X with predicted dose X, 52% and 32% of doses were subtherapeutic when aiming for trough concentrations of 5-10 and 3-7 μg/ml respectively. Treatment costs increased by 102% and 29% for the two trough ranges respectively. On multivariate regression analysis, subtherapeutic infliximab concentrations were associated with ulcerative colitis compared with Crohn's disease [OR: 9.81, 95% CI: 1.28-75.40, p = 0.028] and pre-dose X infliximab trough concentration [OR: 0.07, 95% CI: 0.03-0.15, p<0.001]. Over half of maintenance infliximab drug doses were too low to achieve infliximab blood concentrations of ≥5 μg/ml. While applying precision-dosing may improve patient outcomes, drug costs could be considerably greater. This article is protected by copyright. All rights reserved.