Study, Evaluating Pharmacokinetics, Pharmacodynamics, Immunogenicity and Safety Profiles of Rituximab Compared to MabThera® in Patients With Rheumatoid Arthritis

Inclusion Criteria: * Male and Female 18-65 y.o. with body weight 50-120 kg * Patients with active rheumatoid arthritis with disease duration minimum 6 months prior to screening visit per ACR/EULAR 2019 criteria classification. * Moderate or severe active course of rheumatoid arthritis, which is defined as the fulfillment of all of the following conditions: * ≥6 tender joints (based on a score of 68 joints) at screening and baseline; And * ≥6 swollen joints (based on a score of 66 joints) at screening and at baseline; And * level of C-reactive protein is not less than 10 mg/l or ESR is not less than 28 mm/hour at screening. * Positive result of the analysis for antibodies to cyclic citrullinated peptide (≥10 units/ml) and / or the presence of rheumatoid factor (≥ 20 units/ml) at screening (see section). * Received treatment for RA and experienced an inadequate response or intolerance to treatment with at least 1 anti-TNF alpha therapy; * Must have received MTX for a minimum of 12 weeks, with the last 4 weeks, prior to screening at a stable dose 10-25 mg/week; Exclusion Criteria: * Contraindications according to the MabThera SmPC and every serious coexisting diseases which, in the Investigator's opinion, would preclude subject participation * History of current rheumatic autoimmune disease other than RA and current inflammatory joint disease other than RA * Positive tests for HIV, hepatitis B surface antigen (HBsAg) Anti-HBc antibody, hepatitis C antibody * Prior treatment with rituximab, other anti-CD20 mAb * Pregnancy or lactation or women planning to get pregnant during the course of the study and/or within 12 months post last study drug infusion * COVID prior 8 weeks prior to Screening visit or other acute systemic infection within 4 weeks prior to Day 1 * Allergic reaction or intolerance to rituximab, MabionCD20 or any of their components * Severe allergic or anaphylactic reactions to humanized or murine monoclonal antibodies or previous treatment of any lymphocyte-depleting therapies * Confirmed current active tuberculosis (TB). * Any significant cardiac disease * History of a severe allergic reaction or anaphylactic reaction to a biological agent or history of hypersensitivity to any component of the study drug including known hypersensitivity or allergy to a murine product.