Per Queen's Regulatory Office, study is terminated or expired.

The overall objective is to evaluate the clinical efficacy and safety of tocilizumab relative to placebo among approximately 300 hospitalized adult patients who have severe COVID-19. The study will be a 2 arm double blinded comparison between tocilizumab 8 mg/kg and matching placebo IV. The dose may be repeated in 8-12 hours if clinical symptoms worsens, (e.g. increase in oxygen requirements). Participants will be followed for 28 days.

Inclusion Criteria:

• ii. Hospitalized with COVID-19 pneumonia, based on chest X-ray or CT scan AND iii. Evidence of hyperinflammation: IL-6>40pg/mL (if available) OR CRP >2 mg/dL OR ferritin >2000 ng/mL AND iv. One or more of the following: impending need for requiring invasive or non-invasive mechanical ventilation OR shock requiring vasopressor (without evidence of bacterial / fungal infection) OR need for extracorporeal membrane oxygenation (ECMO) OR severe, refractor ARDS (PaO2/FiO2<200 mmHg)

Exclusion Criteria:

Known severe allergic reactions to tocilizumab or other monoclonal antibodies

• Active tuberculosis infection based on history
• Suspected active bacterial, fungal, viral, or other infection (besides COVID-19)
• In the opinion of the investigator, progression to death is imminent and inevitable within the next 24 hours, irrespective of the provision of treatments
• Have received oral anti-rejection or immunomodulatory drugs (including tocilizumab) with the past 6 months
• Participating in other drug clinical trials (participation in COVID-19 trials allowed)
• Self-reported pregnant or breastfeeding
• Any serious medical condition or abnormality of clinical laboratory tests that, in the investigator's judgment, precludes the patient's safe participation in and completion of the study
• Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) > 10 x upper limit of normal (ULN) detected within 24 hours at baseline
• Absolute neutrophil count (ANC) < 1000/mL at baseline
• Platelet count < 50,000/mL at baseline