Background: The combination of antitumor necrosis factor-alpha (TNF-α) agents with immunomodulators (IMMs) is a common treatment for pediatric Crohn's disease (CD). Although methotrexate (MTX) can be a first-line medication as an IMM, most clinicians in real-life practice, especially in South Korea, are more familiar with thiopurines. This study aimed to compare the efficacy and immunogenicity of MTX and azathioprine (AZA) as concurrent therapies for pediatric CD.
Methods: In this pilot study, 29 newly diagnosed pediatric patients with moderate-to-severe CD were randomized to receive either MTX (n = 15) (15 mg/body surface area (BSA) per week) or oral AZA (n = 14) (0.5 mg/kg per day) in combination with Infliximab (IFX). The primary outcomes were the proportion of patients in endoscopic, biochemical, and transmural remission after 14 and 54 weeks of IFX therapy. The trough levels (TLs) of IFX and anti-drug antibody (ADA) levels were also compared.
Results: Among the 29 patients, there were no significant differences in the biochemical (p = 1.0 at week 14, p = 0.45 at week 54), endoscopic (p = 0.968 at week 14, p = 0.05 at week 54), or transmural (p = 0.103 at week 54) remission rates between the two medications during the concurrent therapy. Additionally, the trends in the IFX trough and ADA levels over time during the treatments were similar for both medications, with no significant differences (p = 0.686, p = 0.389, respectively).
Conclusion: The MTX showed comparable efficacy to the AZA in pediatric CD patients with moderate-to-severe disease. This effectively maintained adequate IFX levels and reduced ADA production. Therefore, although additional large-scale clinical trials are needed, this study demonstrated that either MTX or AZA can be selected as IMMs in the concurrent treatment of pediatric CD, depending on individual medical institutions' circumstances.
Keywords: anti-drug antibody; azathioprine; immunogenicity; immunomodulatory; methotrexate; pediatric Crohn’s disease; trough level of anti-TNF agent.