Pharmacokinetics and exposure-efficacy relationship of adalimumab in pediatric patients with moderate to severe Crohn's disease: Results from a randomized, multicenter, phase-3 study

Background: Adalimumab, a fully human monoclonal antibody (IgG1) to tumor necrosis factor, has shown benefit in the treatment of inflammatory bowel disease. The purpose of this analysis was to evaluate the pharmacokinetics (PK) and the serum concentration-efficacy relationship of adalimumab in pediatric patients with moderate-to-severe Crohn's disease. Methods: The safety, efficacy, and PK of adalimumab was evaluated in a phase-3, randomized, double-blind, 52-week study (IMAgINE-1, N 192), which had a 4-week open-label induction phase (dose was determined by patient weight) followed by a 48-week double-blind maintenance phase (standard and low-dose arms, drug given every other week). Trough serum adalimumab (baseline, weeks 2, 4, 16, 26, and 52) and anti-adalimumab antibody measurements (baseline, weeks 16, 26, and 52) were collected. Disease activity was assessed using the Pediatric Crohn's Disease Activity Index. Results: At week 52, adalimumab trough concentrations (mean ± SD) were higher for patients in the standard-dose (9.48 ± 5.61 g/mL) compared with the low-dose (3.51 ± 2.21 g/mL) arm. In patients whose doses were increased from every other week to weekly, higher trough concentrations were observed after dose escalation. Higher body weight, baseline C-reactive protein, and lower baseline albumin levels were associated with greater clearance of adalimumab. An exposure (serum concentration)-efficacy relationship was observed, in which higher concentrations of adalimumab were associated with greater rates of remission. Conclusions: This study is the first to describe the PK of adalimumab in pediatric patients with moderate-to-severe Crohn's disease. A positive association between serum adalimumab concentration and remission/response was identified.