POS0177 INFECTION INCIDENCE, TIMING, AND DOSE DEPENDENCY IN RHEUMATOID ARTHRITIS PATIENTS TREATED WITH RITUXIMAB: A RETROSPECTIVE COHORT STUDY

Background Rituximab (RTX) is a safe and effective treatment for rheumatoid arthritis (RA). In The Netherlands, RTX usually administered intravenously every six months in standard low dose (2x500 mg or 1x1000 mg). Ultra-low doses (1x500 1x200 months) have shown to be as well continued RA patients who are remission. [1] Despite its efficacy safety, there some concerns about infection risk RTX. Preliminary data suggest time dependent with higher shortly after infusion. [1,2] Objectives aim of this study was compare incidence rates (IRs) real-life population between ultra-low dosed RTX, an additional focus on since last Methods treated the Sint Maartenskliniek (The Netherlands) 2012 2021 were included retrospective cohort study. Patient-, disease-, treatment- characteristics retrieved from electronic health records. Infusions given within 30 days considered one treatment. As months, only infections occurring 6 administration included. absence exact date infection, start imputed using single imputation based known week, month period infection. Infection IRs, dose-dependency relations infusion analyzed mixed-effects Poisson regression correction confounders. After Bonferroni correction, results statistically significant if p<0.025. Results Among 490 followed 1254 patient years, 819 identified (65/100 years). Most mild (89%) respiratory tract most prevalent (49%). IRs 41, 54 71 per 100 years 200 mg, 500 1000 respectively. Incidence rate ratio (IRR) significantly lower comparison (adjusted IRR 0.64 (95% CI 0.45-0.93, p=0.019)). Infections seemed occur more frequently – although not - first two later cycle (table 1). Conclusion dosing, especially associated RA. Additionally, trend IR found. Therefore, future optimization focusing dosing slow release (e.g. by subcutaneous administration) may further addition reducing costs time. clinical practice, physicians should consider offering dosage sustained remission, instead continuing 1000mg dosage. References [1]Verhoef LM, den Broeder N, Thurlings RM, et al. (REDO study): randomised controlled non-inferiority trial. Lancet Rheumatol. 2019; 1: e145-e153. [2]Opdam MAA, de Leijer JH, dose-dependent mediated through circulating immunoglobulins, neutrophils B cells. Rheumatology (Oxford). 2022;62(1):330-334. Table 1. received dose/ Last (n) 654 129 36 Patient 926 241 87 (n/100 years) 41 Crude CI) 1.00 (ref.) 0.77 (0.62-0.95, p=0.014) 0.59 (0.41-0.85, p=0.004) Adjusted 0.82 (0.66-1.02, p=0.071) (0.45-0.93, p=0.019) Time 0-2 2-4 4-6 317 259 243 443 425 386 72 61 63 0.85 (0.72-1.01, p=0.060) 0.89 (0.75-1.05, p=0.160) 0.86 (0.73-1.01, p=0.070) 0.90 (0.76-1.07, p=0.244) Acknowledgements: NIL. Disclosure Interests Lara Veeken: None declared, Merel Opdam: L.M. Verhoef: Calin Popa: Reinout van Crevel: Alfons Grant/research support from: Grants quality care projects research RA, PsA axSpA Abbvie, Galapagos, Pfizer, Novartis, Lilly, Sanofi, Gilead institution/department rheumatology.