The effects of albumin on serum infliximab concentrations and efficacy in UC were reported previously.23 Although the occurrence of antibodies Alectinib clinical trial to TNF inhibitors has been cited as a possible cause for loss of therapeutic effect,10, 13 and 24 the multivariable logistic regression analysis showed that ATI status was not associated strongly with successful induction of clinical response at week 8 or maintenance of response at week 30. Overall, the data from the multivariable model suggest that low serum infliximab concentrations

(which could result from the presence of ATI) are associated more directly with a decreased response rather than just the occurrence of ATI. This finding is consistent with conclusions from a systematic review of the impact ABT-737 in vivo of ATI in Crohn’s disease,25 as well as previously published findings of the ACT trial, which showed that the clinical response rate was numerically higher in patients who had inconclusive ATI status (with higher serum infliximab concentrations) compared with those who tested positive or negative for ATI (with lower serum infliximab concentrations).2 Furthermore,

other investigators have reported that some ATI may be transient and do not lead to worse clinical outcomes unless these ATI levels are sustained.26 The persistence of ATI was not assessed in the current analysis to make this determination. Notwithstanding this apparent lack of effect of ATI status on efficacy, it should be noted that the assay used for these ATI assessments was only able to detect ATI accurately in the absence of detectable circulating infliximab. Also, Olopatadine there likely is some bias from missing data because patients who withdrew early from the study because of lack of efficacy may not have had a comprehensive assessment of ATIs. It is possible that a higher proportion of these patients may have developed ATIs compared with those who continued in the trial. Another important finding in the current study was that although patients with the poorest outcomes generally

showed relatively lower serum infliximab concentrations, they did so at both dose levels in the ACT studies. Although the reason for this phenomenon is unknown, this counterintuitive finding suggests an intricate relationship between infliximab pharmacodynamics and its systemic clearance, such that patients who are more likely to respond better to infliximab have intrinsically lower clearance of the drug. Because the overall infliximab clearance is unchanged within the dose range evaluated in the ACT trials,4 this hypothesis could explain why, despite higher infliximab dose and higher infliximab concentrations, the proportion of patients achieving efficacy outcomes remained largely unchanged when the respective dose-stratified concentration quartiles were compared, most strikingly in the lowest infliximab concentration quartiles (Supplementary Figure 4).