Clinical and Biochemical Factors Associated With Infliximab Pharmacokinetics in Adult Patients With Inflammatory Bowel Disease

Many patients with inflammatory bowel disease (IBD) do not adequately respond to infliximab, potentially due to individual differences in pharmacokinetics (PK). This study aimed to identify clinical and biochemical variables associated with infliximab PK. Adult IBD patients treated with infliximab and with registered infliximab trough levels between March 1, 2021 and November 22, 2023, were included. Univariable and multivariable linear mixed-effects models were used to evaluate associations between clinical and biochemical covariates and infliximab trough levels. A systematic literature review was conducted to contextualize findings. The study included 259 patients (CD: n = 202; UC: n = 47; IBD-unclassified: n = 10) with 560 infliximab trough levels available for analysis. Higher hemoglobin was associated with lower infliximab levels (IBD: β = 0.668, p = 0.036; UC: β = 1.639, p = 0.018), as were albumin (IBD: β = 0.214, p = 0.002; CD: β = 0.345, p < 0.001) and AST (CD: β = 0.040, p = 0.019). Inverse associations were also found for ALT (UC: β = -0.100, p = 0.016), ALP (CD: β = -0.029, p = 0.021; UC: β = -0.018, p = 0.037) and GGT (IBD: β = -0.015, p = 0.028; UC: β = -0.034, p < 0.001). Endoscopic inflammation was positively associated with infliximab levels in CD (β = 3.402, p = 0.035). Systemic steroid use was associated with lower infliximab levels in UC (β = -4.263, p = 0.013). In conclusion, this study identified several clinical and biochemical variables, including albumin, hemoglobin and GGT across all patients, albumin, AST and ALP in CD, and hemoglobin, ALT, ALP and GGT in UC, that were associated with infliximab trough levels. Given the correlative nature of this study, these results should be interpreted cautiously. These findings merit validation and could inform model-informed precision dosing strategies in IBD clinical care.