Comparison of Complarate® (Tocilizumab Biosimilar) and Actemra® in Patients With Rheumatoid Arthritis

Inclusion Criteria: * Availability of written informed consent obtained from the patient before the start of any procedures related to the study. * Men and women 18-75 years of age, inclusive, at the time of signing the informed consent form. * Patients with a documented diagnosis of rheumatoid artritis (RA), established according to the 2010 ACR/EULAR classification criteria at least 6 months before screening, with moderate to high disease activity and an insufficient response to methotrexate monotherapy (maintaining moderate/high disease activity for at least 3 months) and/or poor tolerability of methotrexate (including the subcutaneous form of the drug) and/or insufficient response to or intolerance to other synthetic disease-modifying anti-inflammatory drugs (sDMARDs) in combination with methotrexate or without methotrexate. * The number of swollen and/or painful joints is 6 or more. * No changes in the dosage regimen of standard RA therapy with oral glucocorticosteroids and NSAIDs for ≥ 4 weeks before screening. * No changes in the dosing regimen of standard RA sDMARD therapy for ≥ 4 weeks before screening. * Agreement to adhere to adequate methods of contraception throughout the study and for 3 months after the end of tocilizumab therapy. Exclusion Criteria: * A history of rheumatic autoimmune disease other than rheumatoid arthritis. * Functional Class IV according to the ACR Functional Status Classification or wheelchair/bedridden. * Development of pronounced extra-articular (systemic) manifestations of the disease and complications (rheumatoid vasculitis, amyloidosis, Felty's syndrome, neuropathy, damage to the organ of vision). * Use of oral corticosteroids in doses greater than \>10 mg daily prednisolone equivalent, or change in oral corticosteroid dose within 4 weeks before or during screening. * Use of injectable corticosteroids (including intra-articular corticosteroids) or intra-articular hyaluronic acid injections within 4 weeks before or during screening. * Therapy with tumor necrosis factor-alfa (TNF-alpha) inhibitors or any other genetically engineered biological drugs within 1 month before screening. * History of tocilizumab therapy. * Major surgery (including joint surgery) within 8 weeks before the start of the study or elective surgery within 6 months after the start of the study. * A history of an adverse drug reaction to any of the components of the study drug or a reference drug. * Immunization with any live or live attenuated vaccine within 1 month before the first dose of the study or comparator drug. * A history of a disease associated with the accumulation of immune complexes (including serum sickness). * Concomitant diseases and conditions that, in the opinion of the Investigator and/or Sponsor, jeopardize the safety of the patient during participation in the study, or which will influence the analysis of safety data. * Active systemic infection (bacterial, viral or fungal) within 14 days before signing the informed consent form or at the time of screening. * Blood donation or blood loss (450 ml of blood or more) less than 2 months before the start of the study. * Pregnancy or breastfeeding. * History of demyelinating disease of the central nervous system. * History of diverticulosis/intestinal diverticulitis or chronic ulcerative diseases of the lower gastrointestinal tract, such as Crohn's disease, ulcerative colitis. * History of tuberculosis. * Positive/doubtful test with tuberculosis allergen. * Participation in clinical trials of drugs less than 3 months before signing the informed consent form. * Positive tests for hepatitis B or C, HIV or syphilis. * Unwillingness or inability to comply with the recommendations prescribed by this protocol. * Identification during screening of other diseases/conditions not listed above that, in the opinion of the physician-researcher, prevent the inclusion of the patient in the study.