Association between infliximab concentrations and clinical response in psoriasis: a prospective cohort study.

Background: Infliximab (IFX) trough concentrations (C _min ) have been linked to treatment efficacy in psoriatic patients. Inter-individual IFX C _min variability and factors influencing IFX pharmacokinetics could explain differences in treatment response.
Objective: To evaluate the association between IFX C _min and clinical outcomes in psoriatic patients.
Methods: Prospective study of 33 patients with moderate to severe psoriasis receiving IFX at Bellvitge University Hospital, between October 2013 and November 2016. IFX C _min and antibodies toward infliximab (ATI) were measured.
Results: We collected 155 IFX C _min and ATI values (mean age, 46 (14) years; 11 (33.3%) women). Mean IFX C _min was 2.5 (2.4) mg/L and ATIs were detected in six patients, resulting in undetectable IFX C _min . IFX C _min was significantly associated with ATI and body mass index (BMI) (β -2.51, 95% CI -3.56 to -1.4 and β -0.05, 95% CI -0.09 to -0.01). PASI score and PASI 90/100 response were significantly associated with IFX C _min (IRR 0.80, 95% CI 0.70 to 0.92; OR 1.79, 95% CI 1.18 to 2.71 and OR 1.79, 95% CI 1.14 to 2.81).
Conclusion: IFX C _min significantly influences PASI 90/100 response rates. IFX C _min wa significantly associated with ATI and BMI. The observed inter-individual variability in IFX C _min supports the need for IFX drug monitoring.