Assessment of the Influence of Inflammation and FCGR3A Genotype on Infliximab Pharmacokinetics and Time to Relapse in Patients with Crohn's Disease.

Abstract

Infliximab is a monoclonal anti-tumor necrosis factor-α (anti-TNFα) antibody that profoundly modified the treatment of Crohn's disease (CD). The polymorphism of Fc fragment of IgG, low affinity IIIa, receptor (CD16a) [FCGR3A] influences the biological response to infliximab in patients with CD. Our aim was to study its influence on infliximab pharmacokinetics and risk of relapse after infliximab discontinuation. In 111 CD patients in remission, infliximab was discontinued and its concentrations were measured for 30months or until relapse. Infliximab pharmacokinetics were described using monocompartmental population modeling. The elimination rate of infliximab increased with C-reactive protein (CRP) [p=0.00018] and was 16% higher in FCGR3A-158V/V patients than in F carriers (p=0.0028). Risk of relapse was higher in patients with baseline CRP≥5mg/L than in those with a lower value (p=0.0000029). In addition, there was a first-order interaction between CRP and the FCGR3A genotype; in patients with high CRP, risk of relapse was higher for V/V patients than for F carriers (hazard ratio 4.80 and 2.84 for V/V and F carriers, respectively; p=0.013). Both increased inflammation and FCGR3A-158V/V genotype are associated with increased infliximab elimination and risk of relapse after infliximab discontinuation in patients with CD.