Patients with Crohn's disease may experience disease relapse on maintenance infliximab. Anti-drug antibodies likely contribute to loss of response, and serum infliximab levels likely correlate with efficacy.
Dr Feagan and colleagues from Canada prospectively evaluated the relationship between trough serum infliximab concentration and disease activity.
Adult patients with a diagnosis of Crohn's disease who had received at least 5 consecutive infliximab infusions, and who planned to receive at least two additional infusions were enrolled.
The Crohn's Disease Activity Index (CDAI), serum infliximab, C-reactive protein (CRP) and antibodies-to-infliximab (ATI) were assessed at baseline, week 4 and week 8.
|Infliximab trough concentrations below 3 μg/mL may increase the likelihood of symptoms|
|Alimentary Pharmacology & Therapeutics|
Receiver operating characteristic (ROC) analysis examined the relationship between infliximab concentrations and disease activity.
The mean CDAI score, which decreased 1.05 points between infusions, did not correlate with the mean change in trough infliximab concentration, but was associated with the mean change in CRP concentration.
The research team found that trough infliximab concentrations below 2.8–4.6 μg/mL best predicted a ≥ 70 point increase in the CDAI between infusions, and those below 2.7–2.8 μg/mL best predicted CRP >5 mg/mL at the second infusion.
The team observed that antibodies-to-infliximab at either visit decreased the proportion of patients with therapeutic infliximab trough levels compared with patients who were antibodies-to-infliximab negative.
Dr Feagan's team concludes, "This prospective study confirms the relationship between trough infliximab concentrations, inflammation and antibodies-to-infliximab."
"Infliximab trough concentrations below 3 μg/mL may increase the likelihood of symptoms and inflammation."