Infliximab drug and antibody levels in patients with dermatological conditions

Background In recent years, studies monitoring infliximab in rheumatoid arthritis and inflammatory bowel disease have confirmed the relationship between the clinical response and the infliximab and anti-infliximab antibodies serum levels. However, there is only limited evidence in the field of dermatology. Objective The aim of this study was to establish the correlation between plasma infliximab levels, the presence of anti-infliximab antibodies and the clinical response in dermatological conditions. Setting Retrospective observational study in a tertiary hospital (University Hospital of La Corua, Spain). Method Patients with dermatological conditions being treated with infliximab (5 mg/kg/8 weeks after the induction dose) were included in the study. The concentrations of infliximab and anti-infliximab antibodies were quantified by two sandwich-type ELISA immunoassays. The patients were classified into three groups based on the efficacy: good, partial or non-efficacy at the time of each blood assessment. The development of adverse reactions was also evaluated. Main outcome measures Plasma levels of infliximab and anti-infliximab antibodies, clinical response and infusion reactions. Results 17 patients (45 assessments) were included. The good/partial efficacy rate was significantly higher in the case of > 0.05 than < 0.05 mu g/mL infliximab concentration (93.3 vs. 40.0 %, p < 0.001). Anti-infliximab antibodies were only detected in five samples. Their presence was associated with a higher frequency of infusion reactions and a lower efficacy rate in comparison with the group without antiinfliximab antibodies (100.0 vs. 0.0 %, p < 0.001 and 0.0 vs. 85.0 %, p < 0.001 respectively). Conclusions The results obtained show that the presence of infliximab concentrations higher than 0.05 mu g/mL are correlated with a good clinical response and the absence of toxicity. The incidence of anti-infliximab antibodies is low, although a correlation was observed between the presence of antibodies, absence of infliximab concentration, loss of clinical response and the development of infusion reactions.