Successful reduction of overexposure in patients with rheumatoid arthritis with high serum adalimumab concentrations: an open-label, non-inferiority, randomised clinical trial

Objective High adalimumab serum concentrations do not result in better response in patients with rheumatoid arthritis (RA), suggesting overexposure. We investigated whether patients with adalimumab concentrations >8 mu g/mL can prolong their dosing interval by 50% without a clinically relevant change in disease activity. Methods Consecutive patients with RA, treated with adalimumab 40mg every other week for at least 28 weeks, were approached for this randomised, open-label, non-inferiority trial. Patients with adalimumab trough concentrations >8 mu g/mL were randomly (1:1) assigned to dose-interval prolongation of once every 3weeks or continuation of every other week. Primary outcome was the change in disease activity score of 28 joints (DAS28-ESR) after 28 weeks, with a non-inferiority margin of 0.6 points. Results In total, 147 patients were screened. Fifty-five patients had concentrations >8 mu g/mL and were randomised. Mean DAS28 after 28 weeks was -0.14SD 0.61 in the prolongation group and 0.300.52 in the continuation group. Mean difference was significantly in favour of the prolongation group: 0.44 (95% CI 0.12 to 0.76, p=0.01). Conclusions Adalimumab-treated patients with RA with trough concentrations >8 mu g/mL can prolong their standard dosing interval to once every 3weeks without loss of disease control. Trial registration number NTR3509; Results.