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Rituximab (RTX) represents a milestone in the treatment of mixed cryoglobulinemic vasculitis (MCV). Despite usually well-tolerated, RTX may induce different types of adverse drug reactions, including exacerbation of vasculitis. Recently, RTX biosimilar CT-P10 has been approved in Europe for the treatment of rheumatoid arthritis, but no data are available about effectiveness and safety of CT-P10 in the treatment of MCV. In this multicenter open-label study, we analyzed the safety of CT-P10 in patients with MCV treated in first-line or after a shift by RTX originator. Fifty-one consecutive MCV patients (females/males 35/16, median age 68 years, median disease duration 42 months, 51% HCV positive) were included in the study between July and December 2018 and were treated with CT-P10 (group 1). Safety and effectiveness of CT-P10 were compared with a retrospective group (group 2) including 75 consecutive patients treated with RTX originator between July 2017 and July 2018. Thirty-six patients were treated with CT-P10 for the first time, while the other 15 switched from RTX originator. RTX was administrated with high or dosage schemes (375 mg/m 2 four times a week apart/1000 mg twice one week apart or 250 mg/m 2 twice one week apart). During a month period after the last infusion, 13/51 adverse events (AE) were observed in group 1 and 17/75 in group 2 (p not significant). Among them, 7/13 and 6/17 (in group 1 and 2, respectively) could be considered immune-mediated AE (p not significant). At univariate analysis patients with IM-AE were more frequently males (p = 0.04) and with a lower disease duration (p = 0.03), but both the parameters were not significant at logistic regression. About clinical response after 6 months by the end of the treatment, no differences were observed between patients treated with originator and CT-P10 regarding the response to the therapy. No differences were observed in safety and effectiveness between patients naïve at RTX or switching from originator. Despite the higher prevalence of immune-mediated AE among patients treated with CT-P10 than originator, we have observed no significant differences between the 2 groups. The use of a low-dosage regimen is more common in group 1 than in group 2, representing a possible bias of the study, possibly influencing the appearance of AE. Considering the cost/efficacy ratio of biosimilars, their use could be helpful to treat a large number of MCV patients with an effectiveness and safety comparable to originator. Multicenter studies including a large number of patients and the new RTX biosimilars could be useful to fully elucidate the possible risk of immune-mediated adverse events with biosimilar drugs. Considering the cost/efficacy ratio of CT-P10, its use could help to treat a large number of MCV patients with an effectiveness and safety comparable to originator.

This study aims to evaluate the efficacy and safety of repeated treatments with low-dose rituximab for relapsing mixed cryoglobulinemia vasculitis. Thirty-seven patients with mixed cryoglobulinemia vasculitis refractory to standard of care treatment, 34 of which were HCV-positive, were treated with rituximab at the reduced dosage of 250 mg/m 2 given twice 1 week apart per cycle. Thirty patients (81%) achieved a clinical response; 5 of them remain in remission, 3 were lost to follow-up or died, and 22 relapsed after a mean of 15.7 months. Eleven relapsers were retreated with one (6 patients), 2 (3 patients), or 3 (2 patients) additional rituximab cycles given at each relapse. Clinical and laboratory efficacy and side effects of long-term treatment were evaluated. Clinical response to retreatment was 91% (10/11) at the first relapse, 80% (4/5) at the second relapse, and 100% (2/2) at the third relapse. The mean (±SD) time to relapse was 17.1 ± 14.1 months in 30 patients who were treated with only one cycle (from first cycle to the first relapse) and 45.7 ± 30.6 months (from first cycle to the last observed relapse) in 11 patients treated with 2 or more cycles (p = 0.0037). Severe adverse reactions occurred in 3 patients, in 2 of whom at the first cycle. Our results suggest that repeated treatment of relapsing mixed cryoglobulinemia with a low-dose rituximab regimen is efficacious, safe, and cost-effective for the long-term management of this disorder.