THU0183 ABATACEPT AND LOW GAMMA-GLOBULIN LEVELS: NO ASSOCIATION WITH INFECTIOUS RISK OR RA DISEASE ACTIVITY CONTROL

Background: Abatacept (ABA) can induce decrease in gamma-globulins, but the long-term safety of such reduction is unknown. Moreover, it is suggested that such decrease is dissociated from disease activity response. Objectives: To evaluate ABA-induced gamma-globulins reduction and its correlation with disease activity control and the risk of infection in rheumatoid arthritis(RA) patients. Methods: This is a retrospective inception cohort of RA patients undergoing ABA for the first time in a large single tertiary cohort (2007 to 2019). Patients were evaluated regarding clinical and inflammatory data, total and specific (IgG, IgM, IgA) gamma-globulins assessed before, at 3 and 6 months, and then every 6 months up to discontinuation/censoring. The occurrence of severe or recurrent infections as cause of discontinuation of treatment was recorded. All patients were submitted to a systematic infectious screening protocol before and during treatment. Results: One hundred seventy-nine RA patients were included. They were predominantly female (93%;n=167) and had a positive rheumatoid factor (RF, 84%; n=151). Median(range) age and disease duration were 55.1(17-81.3) and 14(1.6-39.8) years, respectively. ABA was used in median as the 3rd (1-8) bDMARD. Most patients (74.3%, n=134) had already used a TNFi previously and 34.1% (n=61) had failed to rituximab. Baseline DAS28 [median(range)] was 4.9 (2-8.62), CDAI 27(5-66), HAQ 1.5 (0-3), ESR 18(2-111), and CRP 8.1(0.1 -135.7). Levels of total gamma-globulins(TGG) were 1.2 (0.5-2.8g/dL), IgG 1,094(422-2,785mg/dL), IgM104(19-405 mg/dL), and IgA 324 (100-739mg/dL). Forty-five patients (25.1%) had low IgG before ABA, but only 8(4.5%) had IgG 0.05). At baseline, TGG, IgG, IgM and IgA correlated positively to all disease activity parameters: DAS28(r=+0.33; r=+0.31;r=+0.24 and r=+0.37, respectively; p 0.05). Moreover, at 6 months, 25 patients (14%) achieved DAS28 ≤ 2.6 and 49 (27.4%) had low disease activity (DAS28 ≤ 3.2). Baseline or longitudinal measures of TTG and subtypes were similar among patients who responded and those who did not, regardless of the cut-off used(p\u003e0.05. Only 14 patients (9.4%) had the medication discontinued due to infections: 3 due to recurrent infections and 11 to severe infections. One patient died. The frequencies of low IgG (under the normal limit of normality) at baseline and all time points(p\u003e0.05) were similar among patients with and without severe/recurrent infections. None of these patients had low TGG or very low IgG( 0.05). Conclusion: This cohort of real-world RA patients shows that reduction in gamma-globulin levels induced by ABA is safe, non-progressive and not associated to a higher risk of infection, even in patients with low IgG or TGG. Additionally, it is not associated to clinical response. Disclosure of Interests: None declared