POS0253 RITUXIMAB-BIOSIMILAR FOR ANTI-NEUTROPHIL CYTOPLASMIC ANTIBODIES-ASSOCIATED VASCULITIS: EXPERIENCE OF A SINGLE ITALIAN CENTER

Abstract

Background:Rituximab (RTX), an anti-CD20 monoclonal antibody, represents a valuable treatment for anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV). RTX biosimilar CT-P10 (RTX-B) has been approved in Europe in all indications held by RTX originator (RTX-O). As stated by recent international consensus-based recommendations, 1 there is evidence regarding safety and efficacy of biosimilars in the context of rheumatic diseases, but it is encouraged to gather additional data. 2,3Objectives:To report the experience of a single Italian center with RTX-B in AAV in terms of safety and efficacy.Methods:We retrospectively reviewed the charts of all AAV patients followed up in our Small Vessel Vasculitis Clinic and we selected those who received RTX-B between October 2017 and May 2020, both naïve to RTX (RTX-Bn) or already treated with ≥1 course of RTX-O and switched to RTX-B (RTX-Bs). Baseline features, disease outcome, concomitant therapy and adverse events 6 (T6), 12 (T12) and 24 (T24) months after RTX-B introduction, when available, were collected. Non-parametric statistic tests were used.Results:Fifty-six AAV patients (44 [78.6%] granulomatosis with polyangiitis (GPA), 12 [21.4%)] microscopic polyangiitis (MPA)) received RTX-B with a median follow up of 20 (IQR 10-24) months. ANCA were positive in 49 (87.5%) patients. Ten (17.9%) patients were newly diagnosed with AAV, while 23 (41.1%) had refractory disease and another 23 had relapsing disease.Thirty-three (58.9%) patients were RTX-Bs, whereas 23 (41.1%) RTX-Bn. In 29 (51.8%) patients RTX was decided because of remission induction, while in 27 (48.2%) as maintenance regimen. Median cumulative RTX-B dose was 2.5 (2-3.875) grams with 3 (IQR 2-4) median courses. AAV activity, adverse events and concomitant therapy at T6, T12 and T24 are shown in Table 1. One GPA patient died of severe infection 3 months after a single infusion of RTX-B 500 mg as maintenance therapy.Table 1.AAV activity, concomitant therapy and adverse events at T0, T6, T12 and T24.T0T6T12T24n (%)56 (100)52 (92.6)40 (71.4)18 (32.1)Dose RTX-B, median (IQR) grams1.75 (0.5-2)0.5 (0.5-1)0.5 (0.5-1)0.5 (0.5-1)Concomitant prednisone therapy, n (%)42 (75)27 (48.2)13 (32.5)4 (22.2)Dose prednisone, median (IQR) milligrams/day5 (5-15.625)2.5 (2.5-5)3.75 (2.75-7.5)2.75 (1.56-4.5)Concomitant bDMARDs, n (%)10 (17.9)5 (9.6)3 (7.5)1 (5.6)RefractorinessNA4 (7.7)2 (5)1 (5.6)RelapseNA0 (0)3 (7.5)2 (11.1)RemissionNA48 (92.3)35 (87.5)15 (83.3)SuspensionNA10 (19.2)9 (22.5)4 (22.2)Infusion reaction, n (%)1 (1.8)1 (1.9)0 (0)0 (0)Infectious adverse events, n (%)NA10 (19.2)6 (15)3 (16.7)Severe infectious adverse events, n (%)NA2 (3.8)1 (2.5)0 (0)Considering the 52 (92.6%) patients who reached a 6 months-follow up, we marked a significant decrease of number of patients on steroid therapy (39 [75%] vs 27 [51.9%]; p=0.003), of median prednisone daily dose (5 [IQR 5-25] vs 2.5 [IQR 1.25-5 mg; p=0.001) and of number of patient on concomitant bDMARDs (10 [19.2%] vs 5 [9.6%]; p=0.003).Analysing the 40 (71.4%) patients who reached a 12 months-follow up, we confirmed the tendency with a decrease of number of patients on steroid therapy (29 [72.5%] vs 13 [32.5%]; p=0.007), of median prednisone daily dose (5 [IQR 5-12.5] vs 3.75 [IQR 2.75-7.5]; p=0.008) and of number of patient on concomitant bDMARDs (9 [22.5%] vs 3 [7.5%]; p=0.009).No statistically significant difference was found for the same variables comparing T0 versus T24.Conclusion:Our experience with RTX-B is limited; however, it represents an extensive report about the use of RTX-B in AAV patients and confirmed that it may be a well-tolerated and effective therapy in AAV setting, in agreement with previous evidence on RTX-O. Prospective and larger studies are needed to confirm this preliminary evidence.