Therapeutic Drug Monitoring of Guselkumab in Psoriasis Patients

Evaluation of the Preditive Value of Early Serum Trough Concentrations and Anti-drug Antibodies of Guselkumab and the Development of the Concentration-response Curve of Guselkumab for 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.

Inclusion Criteria:

1. Participants must have a clinical or histological diagnosis of chronic plaque-type psoriasis
2. Participants must sign an ICF indicating that he or she understands the purpose of, and procedures required for, the study and is willing to participate in the study

Exclusion Criteria:

1. Participants who have currently a predominant nonplaque form of psoriasis
2. Participants who are pregnant, nursing or planning a pregnancy
3. Participants who are unable or unwilling to undergo multiple venapunctures
4. Participants who are treated according to a different dosing schedule than standard dosing of guselkumab