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

BACKGROUND AND OBJECTIVES: Infliximab is a monoclonal anti-tumor necrosis factor-alpha (anti-TNFalpha) 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. METHODS: In 111 CD patients in remission, infliximab was discontinued and its concentrations were measured for 30 months or until relapse. Infliximab pharmacokinetics were described using monocompartmental population modeling. RESULTS: 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 >/=5 mg/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). CONCLUSION: 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