Development of a predictive marker panel for the individualised bDMARD therapy of psoriatic arthritis: protocol for a prospective observational study (Integrate-PsA).

INTRODUCTION: Psoriatic arthritis is a chronic inflammatory disease that can affect the axial skeleton as well as the joints and enthesis. Following the failure of conventional synthetic disease-modifying antirheumatic drugs (DMARDs), numerous biological DMARDs (b-DMARDs) or targeted synthetic DMARDs are now available, although current guidelines do not recommend a specific mode of action in the absence of comorbidities or contraindications. The aim of the study is to identify markers associated with the achievement of Minimal Disease Activity (MDA) at week 16 in patients treated with tumour necrosis factor inhibitors (TNFi), interleukin-17 inhibitors (IL-17i) or interleukin-23 inhibitors (IL-23i). METHODS AND ANALYSIS: A total of 100 patients with active psoriatic arthritis (PsA) with a clinical indication for treatment escalation of methotrexate (MTX) (ie, non-response or intolerance to MTX) to a b-DMARD are to be included in the prospective observational cohort study. Patients are escalated according to physician's choice to one of the following modes of action: TNFi, IL-23i or IL-17i. Participant recruitment is currently ongoing and is expected to be completed in July 2026. This protocol was finalised prior to database lock and before any outcome analyses were conducted. The primary endpoint is achieving MDA at 16 weeks. Secondary endpoints include changes in clinical scores: Psoriasis Area and Severity Index 75% improvement, Disease Activity in Psoriatic Arthritis, Nail Psoriasis Severity Index and biomarker evaluation from blood and skin biopsy samples. Machine learning techniques will be applied to identify marker patterns associated with treatment response, while treatment-specific marker interactions will be explored on a hypothesis-generating basis. ETHICS AND DISSEMINATION: Ethics approval was obtained from the Ruhr University Bochum Ethics Committee (no. 23-7918) on 1 December 2024 for study protocol number 2.0 (30 October 2024). Study results will be published in an international journal, regardless of whether the results are positive or negative. Results will be communicated to the scientific community and healthcare professionals at the conference. TRIAL REGISTRATION NUMBER: DRKS00032573.