Abstract

BackgroundInadequate systemic exposure to infliximab (IFX) is associated with treatment failure. This work evaluated factors associated with reduced IFX exposure in children with autoimmune disorders requiring IFX therapy.MethodsIn this single-center cross-sectional prospective study IFX trough concentrations and anti-drug antibodies (ADAs) were measured in serum from children diagnosed with inflammatory bowel disease (IBD) (n = 73), juvenile idiopathic arthritis (JIA) (n = 16), or uveitis (n = 8) receiving maintenance IFX infusions at an outpatient infusion clinic in a tertiary academic pediatric hospital. IFX concentrations in combination with population pharmacokinetic modeling were used to estimate IFX clearance. Patient demographic and clinical data were collected by chart review and evaluated for their relationship with IFX clearance.ResultsIFX trough concentrations ranged from 0 to > 40 μg/mL and were 3-fold lower in children with IBD compared to children with JIA (p = 0.0002) or uveitis (p = 0.001). Children with IBD were found to receive lower IFX doses with longer dosing intervals, resulting in dose intensities (mg/kg/day) that were 2-fold lower compared to children with JIA (p = 0.0002) or uveitis (p = 0.02). Use of population pharmacokinetic analysis to normalize for variation in dosing practices demonstrated that increased IFX clearance was associated with ADA positivity (p = 0.004), male gender (p = 0.02), elevated erythrocyte sedimentation rate (ESR) (p = 0.02), elevated c-reactive protein (CRP) (p = 0.001), reduced serum albumin concentrations (p = 0.0005), and increased disease activity in JIA (p = 0.009) and IBD (p ≤ 0.08). No significant relationship between diagnosis and underlying differences in IFX clearance was observed. Multivariable analysis by covariate population pharmacokinetic modeling confirmed increased IFX clearance to be associated with anti-IFX antibody positivity, increased ESR, and reduced serum albumin concentrations.ConclusionsEnhanced IFX clearance is associated with immunogenicity and inflammatory burden across autoimmune disorders. Higher systemic IFX exposures observed in children with rheumatologic disorders are driven primarily by provider drug dose and interval selection, rather than differences in IFX pharmacokinetics across diagnoses. Despite maintenance IFX dosing at or above the standard recommended range for IBD (i.e., 5 mg/kg every 8 weeks), the dosing intensity used in the treatment of IBD is notably lower than dosing intensities used to treat JIA and uveitis, and may place some children with IBD at risk for suboptimal maintenance IFX exposures necessary for treatment response.

Highlights

  • Inadequate systemic exposure to infliximab (IFX) is associated with treatment failure

  • Enhanced IFX clearance is associated with immunogenicity and inflammatory burden across autoimmune disorders

  • Despite maintenance IFX dosing at or above the standard recommended range for inflammatory bowel disease (IBD) (i.e., 5 mg/kg every 8 weeks), the dosing intensity used in the treatment of IBD is notably lower than dosing intensities used to treat juvenile idiopathic arthritis (JIA) and uveitis, and may place some children with IBD at risk for suboptimal maintenance IFX exposures necessary for treatment response

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Summary

Introduction

Inadequate systemic exposure to infliximab (IFX) is associated with treatment failure. The introduction of biological therapies, including infliximab (IFX), has drastically altered the treatment course of chronic autoimmune disorders affecting children [1]. As the first monoclonal antibody approved for pediatric indications, IFX remains one of the most well studied biologic agents and is widely used, on and off-label, for the management of several chronic autoimmune disorders, including inflammatory bowel disease (IBD) [3], juvenile idiopathic arthritis (JIA) [4, 5], and uveitis [6,7,8]. Studies in IBD and rheumatoid arthritis (RA) indicate that 30% of patients fail to respond to IFX therapy and up to 50% of those who do respond lose response by 1 year of treatment [9, 10]. IFX is currently not labeled for use in children with JIA, due in part to the drug not achieving the primary endpoint in a pivotal phase 3 placebo-controlled randomized-controlled trial, in which the dosing strategy, guided by adult dosing parameters, failed to result in similar drug exposures in children [12, 13]

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