Therapeutic Drug Monitoring of Guselkumab in Psoriasis Patients

Biologic such as guselkumab are currently the most effective treatment option for patients with moderate to severe psoriasis. But they are costly for healthcare systems and still described according to a 'one dose fits all' dosing regimen, leading to potential over- and undertreatment. In this study we aim to investigate the predictive value of early serum trough levels of guselkumab and determine the therapeutic window of guselkumab in psoriasis patients.

Patients will be included after signing informed consent. After inclusion, patients will continue on standard dosing schedule of guselkumab (i.e. one loading dose (100 mg) at week 0 and week 4 and followed by subcutaenously injections every 8 weeks). During each study visit blood will be taken in order to quantify Ctroughs and/or anti-drug antibodies towards guselkumab. In addition, Psoriasis Area and Severity Index (PASI) and Investigator's Global Assessment (IGA) score will be evaluated by a physician. Patients complete the Dermatology Life Quality Index (DLQI) and European quality of life EQ-5D instrument at each visit.