POS0722 EFFECTS ON SOLUBLE IMMUNE CHECKPOINTS INDUCED BY TOCILIZUMAB MONOTHERAPY AFTER ULTRA-SHORT-TERM GLUCOCORTICOIDS IN LARGE VESSEL – GIANT CELL ARTERITIS PATIENTS

Background The most affected vessels in Giant cell arteritis (GCA) are the temporary arteries, but some patients extracranial large also involved (LV-GCA). Tocilizumab (TCZ), a monoclonal anti-interleukin-6 receptor1 antibody, has been approved as glucocorticoid (GC) sparing agent with GCA. Recently, new therapeutic protocols that combine rapid GC tapering and TCZ emerging, their effects on circulating immune cells mediators scarcely known [1]. Another clinical need LV-GCA management is lack of gold standard to define disease state. role checkpoint molecules tuning activation system. They expressed surface cells, soluble forms exist. Active GCA showed reduction CD4+ T expressing PD1 VISTA comparison controls [2,3]. We hypothesize checkpoints modulated by combined treatment they biomarkers able differentiate active from inactive patients. Objectives: 1) To evaluate monotherapy after ultra-short-term treatments checkpoints. 2) identify plasma discriminate between phase those remission. Methods included 16 enrolled single-arm open-label trial ( NCT05394909 ) performed at AUSL-IRCCS Reggio Emilia. Inclusion criteria: PET/CT FDG uptake ≥2 least one vascular district among ESR >40 mm/h (or CRP >10 mg/L); cranial or systemic manifestations polymyalgia rheumatica. Exclusion more than 10 mg/day prednisone for consecutive days previous 3 months. Remission was defined all following: absence any signs symptoms directly attributable GCA; normalization values; new/worsened damage CT; <2 districts overall PET image interpretation non-active vasculitis. All received 500 mg per day methylprednisolone intravenously three weekly subcutaneous injections until week 52. Plasma samples were collected baseline before injections. For Laboratory data same time points. Concentrations CD137L, CD137, CD27, CTLA4, CD80, CD40, CD40L, GITR, GITRL, ICOSL, IDO, LAG3, MICA, MICB, PD1, PDL1, PDL2, PTX3, TIM3 evaluated multiplex bead-based assay MAGPIX instrument. Wilcoxon test used groups, Spearman correlation analysis. P < 0.05 considered statistically significant. Results Soluble PDL1 not detected almost irrespective phase. Intravenous determined significant MICB an increase PTX3 levels. After 52 weeks monotherapy, plasmatic ICOSL observed compared baseline. At weeks, 7 classified remission active. Changes levels occurred Levels did correlate concentrations, markers currently practice inflammation. Conclusion Ultra-short-term modulate evaluation investigated panel allow different phases. References [1]Gloor AD. Rheumatol 2019 [2]Hid CR. Front Immunol [3]Zhang H. Proc Natl Acad Sci 2017 [4]Hellmich B. Ann Rheum Dis Acknowledgements Azienda Unità Sanitaria Locale (AUSL)-IRCCS, Emilia, Italy: “Bando la valorizzazione della Ricerca Istituzionale 2021.” Disclosure Interests None Declared.