Exposure-response of ciclosporin and methotrexate in children and young people with severe atopic dermatitis: a secondary analysis of the TREatment of severe Atopic dermatitis Trial (TREAT).

This is a secondary analysis of a multicentre randomized controlled trial of ciclosporin and methotrexate in children and young people (CYP) with severe atopic dermatitis (AD). Longitudinal trough ciclosporin and erythrocyte methotrexate polyglutamate (MTX-PG) concentrations were measured to evaluate their associations with treatment response and adverse events. Both ciclosporin (4 mg kg-1 daily) and methotrexate (0.4 mg kg-1 weekly) led to a significant reduction in disease severity scores over the 36-week treatment period. Higher trough ciclosporin concentrations were associated with lower disease severity scores and may serve as a useful tool for therapeutic drug monitoring of ciclosporin in CYP with AD. However, in contrast to a previously published study, steady-state erythrocyte-MTX-PG concentrations showed no significant association with treatment response. Drug concentrations were comparable between patients with and without drug-related adverse events.