Association of adalimumab trough concentrations and treatment response in patients with Juvenile Idiopathic Arthritis

Objective: To assess the relationship of adalimumab trough concentrations and treatment response in paediatric patients with juvenile idiopathic arthritis (JIA).

Methods: Monocentric cohort study of JIA patients treated with adalimumab. Clinical data and samples were collected during routine follow-up. Adalimumab trough concentrations were quantified by a novel liquid chromatography-tandem mass spectrometry assay. Anti-adalimumab antibodies were measured in samples with trough concentrations ≤5mg/l. Disease activity was evaluated using the clinical Juvenile Arthritis Disease Activity Score with 71 joint-count (cJADAS71). Response to adalimumab was defined according to recent international treat-to-target guidelines.

Results: 35 adalimumab trough samples were available from 34 paediatric patients with JIA. Although there was no significant difference in adalimumab dose, trough concentrations were significantly lower in patients with secondary failure (median 1.0 mg/l; IQR 1.0-5.3) compared with patients with primary failure (median 13.97 mg/l; IQR 11.81-16.67) or an adequate response (median 14.94 mg/l; IQR 10.31-16.19) to adalimumab.

Conclusion: Adalimumab trough concentrations were significantly lower in JIA patients with secondary failure compared with patients with primary failure or an adequate response to adalimumab. Results suggest that trough concentration measurements could identify JIA patients who require increased adalimumab doses to achieve or maintain therapeutic drug concentrations.

Keywords: Juvenile idiopathic arthritis; LC-MS/MS; adalimumab; therapeutic drug monitoring.