Study of the Efficacy and Safety of a Single Administration of Olokizumab vs. Placebo in Addition to Standard Treatment in Patients With Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection (COVID-19).

Inclusion Criteria: * COVID-19 diagnosis (confirmation of the presence of SARS-CoV-2 virus by rt-PCR) OR sample collection for SARS-CoV-2 virus rt-PCR if the results of SARS-CoV-2 virus rt-PCR are not available yet. * Dated informed consent for participation in this study signed by the patient, or by the legally acceptable representative or when prior consent of the patient is not possible, and the subject's legally acceptable representative is not available, documented approval / favorable opinion by the IRB/IEC. * SpO2 ≤93% (room air) or respiratory rate greater than 30/min (room air) or oxygenation index PaO2/FiO2 ≤300 mmHg (or SpO2/FiO2 ≤315 in the case PaO2/FiO2 assessment is not available (supplementary oxygen) * Computed tomography findings: features consistent with bilateral COVID-19 viral pneumonia and no alternative explanation for these findings. Exclusion Criteria: * Presence of any of the following laboratory abnormalities: absolute neutrophil counts \<0,5 х 10\^9/L white blood cell count \< 2 х 10\^9/L, platelet count \< 50 х 10\^9/L, Alanine aminotransferase (АLT) and/or Aspartate aminotransferase (AST) ≥3,0 х Upper Limit of Normal (ULN) * Kidney injury with creatinine clearance \<30 mL/min. * Hypersensitivity to OKZ, and/or its components. * Septic shock (need for vasopressors to maintain mean arterial pressure ≥ 65 mm Hg and lactate ≥2 mmol / L in the absence of hypovolemia). * Estimated survival of less than 24 hours regardless of treatment. * History of perforation of the gastrointestinal tract, history of diverticulitis. * Recent (less than 5 half-lives), current or planned during the current study period use of immunosuppressive drugs: * biologics (except OKZ) with immunosuppressive effect, including, but not limited to: Interleukin-1 (IL-1) inhibitors (anakinra, rilonacept, canakinumab), IL-6 inhibitors (tocilizumab, sarilumab, siltuximab, etc.), IL-17A inhibitors (seсukinumab, etc.), Tumor Necrosis Factor-alpha (TNF-alpha) inhibitors (infliximab, adalimumab, etanercept, etc.), anti-B-cells therapy, etc.;. * other immunosuppressive drugs (excluding methotrexate in dose up to 25 mg/week), including but not limited to: 1. Glucocorticoids in high doses (\> 1 mg / kg equivalent of methylprednisolone) orally and parenterally; 2. JAK inhibitors; etc. * Concurrent participation in another clinical trial during 30 days before screening. * Pregnancy or lactation. * A history of active tuberculosis, or active tuberculosis suspected by the Investigator. * Administration of plasma from COVID-19 reconvalescent donors for 4 weeks prior to the patient's inclusion in the study and/or planned administration during the study * Patients who deteriorated into Category 4 of the 5-point clinical status scale within more than the last 24 hours.