POS0853 DECREASE IN ANTI-TOPOISOMERASE-1 ANTIBODY TITER IN PATIENTS WITH SYSTEMIC SCLEROSIS DURING LONG-TERM RITUXIMAB THERAPY

Background:Rituximab (RTX) is a new option in the treatment of systemic sclerosis (SSc) [1]. There is not enough data on changes in the level of autoantibodies and their clinical significance during RTM therapy. There are only a few reports on the higher efficiency of RTX in patients (pts) with SSc positive for anti-topoisomerase-1 antibodies (a-Topo-1), therefore the study of this issue might be interested.Objectives:To compare clinical parameters and B-lymphocytes (B-lymph) level in SSc pts depending on the presence or absence of a-Topo-1 during RTX therapy with prospective long-term follow-up.Methods:This study included 88 pts with SSc. The mean follow-up period was 26,3±10,7 months. The mean age was 47years (17-71), female-73 pts (83%), the diffuse cutaneous subset of the disease had 50 pts (57%). Symptoms of the interstitial lung disease (ILD) were observed in 70 pts (80%). The mean disease duration was 5,9±4,8 years. The cumulative mean dose of RTX was 2,9±1,1 grams. All patients received prednisone at a dose of 11,7±4,4 mg, immunosuppressants received 42% of them. There were 63 pts positive for a-Topo-1 and 25 pts - negative. The pts of the compared groups did not differ in the main demographic and clinical parameters, excepting lung involvement. In a-Topo-1 positive group 55 (87%) pts had ILD and only 15 (60%) – in a-Topo-1-negative group (p=0,02). The results at baseline and at the end of the follow up are presented in the form of mean values and changes in parameters (delta).Results:Considering the entire cohort, an improvement of almost all outcome parameters was found. When a-Topo-1 positive and a-Topo-1-negative pts were analyzed separately, we observed a significantly higher decrease in the activity score, depletion of B-lymph, an increase in forced vital capacity (FVC) and diffusion capacity for carbon monoxide (DLCO) in a-Topo-1 positive group of pts (table 1).Table 1.Changes of the main outcome parameters depending on the presence of a-Topo-1 on RTX therapy.Parametersa-Topo-1positive ptsa-Topo-1negative ptsPDelta Activity score (EScSG-AI)1,790,90,001Delta Rodnan skin score (mRSS)4,95,2NSDelta B-lymphocytes (absolute count)0,2120,1930,001Delta FVC*, %8,646,460,001Delta DLCO**, %2,860,0320,001*FVC - forced vital capacity % predicted, **DLCO - diffusion capacity for carbon monoxide % predictedThe a-Тopo-1 level decreased from 174,2±50,1 to 148,1±66,1 units/ml (p=0,0009). In this group, a-Тopo-1 became negative in 5 pts (7,9%). The disappearance of a-Topo-1 positivity was accompanied by a more pronounced decrease in mRSS (delta mRSS=7,4) and a higher depletion of B-lymph. There was a higher cumulative dose of RTX (4±1,4grams) in this 5 pts compared with the pts who sustained a-Topo-1 positivity. There was a moderate negative statistically significant correlation between the a-Topo-1 and the total dose of RTX (r=-0,298, p=0,017). A moderate negative statistically significant correlation was found between the a-Topo-1 and FVC (r=-0,322, p=0,009).Conclusion:In our study, the a-Topo-1 level significantly decreased during RTX therapy in Russian pts. The decrease in a-Topo-1 titers correlated with the total dose of RTX and was accompanied by a decrease in mRSS, disease activity index and an increase in FVC and DLCO. A higher efficacy of RTX in the a-Topo-1 positive group with prevalence of ILD was revealed, therefore a-Topo-1 positivity could be considered as a predictor of a better response to RTX therapy.References:[1]Jordan S, et al. Effects and safety of rituximab in systemic sclerosis: an analysis from the European Scleroderma Trial and Research (EUSTAR) group. Ann Rheum Dis.2015;74:1188–94.Doi:10.1136/annrheumdis-2013-204522.[2]Ebata S, Yoshizaki A, et.al. Rituximab therapy is more effective than cyclophosphamide therapy for Japanese patients with anti-topoisomerase I-positive systemic sclerosis-associated interstitial lung disease. J Dermatol.2019.Nov;46(11):1006-1013.doi:10.1111/1346-8138.15079.Disclosure of Interests:None declared