OP0256 FIBROBLAST ACTIVATION PROTEIN (FAP) PET-CT IMAGING ALLOWS TO DEPICT INFLAMMATORY JOINT REMODELING IN PATIENTS WITH PSORIATIC ARTHRITIS

Background Psoriatic arthritis (PsA) is characterized by substantial mesenchymal tissue activation in the context of inflammation leading to structural damage. Measuring humans vivo challenging but may represent a possibility detect regions at risk for Recently, theranostic ligands have been developed that selectively bind Fibroblast Activation Protein (FAP) and allow recognition activated cells vivo. Accumulation such FAP-based tracers can be visualized positron-emission tomography (PET) (1). Objectives In this study, we analyzed whether FAP tracer-based PET-CT patients with PsA signal associated joint Methods 120 consecutive fulfilling CASPAR criteria 100 healthy controls without musculoskeletal disease received full-body investigation using 68 Ga-labelled inhibitor ( Ga-FAPI-04) tracer, specifically binding FAP. For all visually identified pathological tracer-positive lesions mean maximum standardized uptake value (SUV mean, SUV max) was assessed. Tracer quantified peripheral axial joints correlated various composite scores PsA. Hand MRI scans were performed parallel assess lesions. Follow-up Ga-FAPI-04 obtained subset treated cytokine inhibitors (follow-up between 3-6 months) damage over time. addition, related responses synovial biopsy samples evaluated on molecular level high-resolution slide RNA-sequencing patients. Results accumulated enthesial sites compared (p < 0.0001). Active pain as well measured visual analogue scale highly an increased (peripheral pain: R = 0.718, p 0.0001; back 0.875, Disease Activity PSoriatic Arthritis (DAPSA) score also max expression (R 0.774; Increased baseline progression months later assessed PsAMRIS 0.778, Treatment partially reduced which arrest MRI. contrast, persistent rapid Molecular analysis from FAP+ revealed interactions fibroblasts T cells, innate lymphoid macrophages, strong upregulation NF-kB pathways fostering cartilage bone destruction. Conclusion Our study presents first in-human evidence fibroblast correlates imaging might therefore improve assessment rapidly emerging open new options treat-to-target strategies References [1]Schmidkonz C, Rauber S, Atzinger A, Agarwal R, Gotz TI, Soare Cordes M, Prante O, Bergmann Kleyer Agaimy Kuwert T, Schett G, Ramming Disentangling inflammatory fibrotic activity protein imaging. Ann. Rheum. Dis. 79 (2020), 1485-1491. Disclosure Interests None declared