A Non-inferiority Study on Dose Reduction of Adalimumab in Psoriasis Patients Who Are Overtreated

In this study we investigate whether dose reduction of adalimumab in patients with supratherapeutic adalimumab Ctrough levels is non-inferior to standard dosing of adalimumab. Before randomization, 3 subsequent evaluations of adalimumab Ctroughs will be executed. Patients will be included after signing informed consent and randomized if 2/3 subsequent measurements during screening show supratherapeutic Ctrough levels. Time point of randomization is considered baseline (week 0). PASI calculation will be performed by a blinded and independent physician. In the concentration based arm, dosing frequency will be lowered to 40 mg every 3 weeks (33% reduction). In case of persistent supratherapeutic Ctroughs, a 50% dose reduction will be applied from week 12 onwards. In the standard based arm, patients will continue on standard dosing schedule of 40 mg every other week. During each study visit PASI and IGA score will be evaluated by an independent and blinded physician and adverse events, and concomitant medications will be evaluated by a member of the study team. Ctrough is quantified at each visit; and anti-drug antibodies concentrations only if subtherapeutic concentrations are observed. Patients complete the Dermatology Life Quality Index (DLQI) and EuroQol-5D-5L instrument at each visit. In addition, in a subset of patients in each treatment arm, additional sampling will be collected by dried blood spot sampling in order to build a PK(PD) model for adalimumab,