326. RTX-biosimilar (CT-P10) results of a referral vasculitis centre: A real life experience

Background/Objectives: Biologic agents are breakthrough ugs in the treatment of rheumatic diseases including vasculitis. Rituximab (RTX) becomes one of the standard care in the treatment of ANCA-associated vasculitis (AAV), but high cost limits its use. Biosimilars offer cost-effective treatment options in various diseases due to increasing healthcare expenditures. CTP-10 is the first biosimilar of RTX and has been approved in Europe in all indications held by original RTX (oRTX) with extrapolation. We aimed to describe real life experience in the Vasculitis Centre regarding CTP10 in ter of interchangeability and adverse events. Methods: Data of Hacettepe University Vasculitis Research Centre was used for this study. Patients receiving oRTX or biosimilar (CT-P10) between October 2020-November 2021 were included in the study. Demographics, type and duration of disease, concomitant steroid dose, dosage schemes, and cumulative dose of oRTX/CT-P10 were recorded. Reason for interchangeability (substation or switch) was noted. The protocol for RTX infusion, both for oRTX and CTP-10, was standardized and given by the same premedication and dosing intervals. RTX-induced hypogammaglobulinemia was evaluated. Infusion related reactions (IRRs) were assessed during the infusion period according to the Common Terminology Criteria for Adverse Events (CTCAE); grade 1 includes mild sympto that not require intervention, while grade 2 includes moderate sympto that require interruption of the infusion but responds promptly to symptomatic treatment. Results: Total of 24 (10 female/14 male) patients were included; the median (IQR) age was 57.0 (19) years. Diagnosis were AAV (n=15), IgG4-RD (n=8) and cutaneous polyarteritis nodosa (cPAN, n=1). Fourteen (58.3%) patients used CTP-10 whereas 10 (41.7%) patients were on oRTX. None of the ug changes was due to substitution. All of the switches were made due to the hospital's reimbursement policy which was shown in Table. The most commonly used dosage schemes were 1000 mg once for 6 months or 1000 mg every two weeks for 6 months both for oRTX and CT-P10. IRRs occurred in 42.8% (21.4% at each grade) of patients switched from oRTX to CT-P10 and 22.2% (all of them grade 2) of patients received oRTX. Statistical analysis was not performed due to low numbers. Commonly observed IRRs were owsiness/weakness and itching/yness/irritation of throat both grade 1 and 2 (Table). RTX-induced hypogammaglobulinemia for IgG and IgM were determined in 2 (15.4%) and 3 (37.5%) patients, respectively. Conclusions: CT-P10 is an increasingly used biologic agent among our patients with acceptable adverse events. Severe IRR symptom was not seen in any of the patients receiving oRTX or CT-P10. Interchangeability of an originator biologic and use of biosimilar are generally tailored according to emerged scientific evidence as well as local resources. Disclosures: Non