Therapeutic drug monitoring: Toward tailored dosing of adalimumab in rheumatoid arthritis.

Rationale:

Treatment with biologicals is based on the principle of 'one size fits all'. In the dosing scheme, patients characteristics or pharmacokinetic aspects are not taken into account. In addition, when a patient responds well to the drug, the question whether the dose can be de-escalated or the drug can be discontinued, remains unanswered. Based on literature, dose de-escalation seems to be safe with regard to disease activity and might be beneficial in lowering the risk of adverse events. An important additional aspect is the large amount of costs that can be saved when the same response rates are achieved with less medication.



Objective:

To examine response of disease activity in patients with high serum adalimumab concentration who are randomly assigned to continuation of the regular dose or to dose interval prolongation and to examine the cost-effectiveness of this therapeutic drug monitoring strategy.



Study design:

Open randomised controlled study of therapeutic drug monitoring in RA patients treated with adalimumab.



Intervention:

Patients with high adalimumab concentrations will be randomly assigned to continuation of adalimumab every other week or prolongation of the dosage interval to once every 3 weeks. Patients will be followed for 6 months.



Main study parameters:

Adalimumab serum concentrations define whether a patient is suitable for inclusion and randomisation. Adalimumab serum concentrations, disease activity and cost related parameters will be measured during follow-up.



Nature and extent of the burden:

We hypothesize that in patients with high adalimumab concentrations and dose interval prolongation disease activity remains stable, however, an increased disease activity risk can not be excluded.

We hypothesize that in rheumatoid arthritis (RA) patients responding to adalimumab, with high adalimumab serum concentrations at least 28 weeks after treatment initiation:

1. Lowering the serum concentrations through dose interval prolongation will not influence disease activity and hence;

2. Through lower costs, dose interval prolongation will be more cost–effective than the traditional treatment scheme.

-2 weeks, 0, 2 and 6 months.

Patients with high adalimumab concentrations will be randomly assigned to continuation of adalimumab every other week or prolongation of the dosage interval to once every 3 weeks. Patients will be followed for 6 months.