A Study to Evaluate the Efficacy and Safety of Tocilizumab in Hospitalized Participants With COVID-19 Pneumonia

• Hospitalized
• COVID-19 pneumonia confirmed by a positive polymerase chain reaction (PCR) of any specimen and radiographic imaging
• SpO2 < 94% while on ambient air

Inclusion Criteria Specific to Long-Term Extension

• Participated in Study ML42528 (EMPACTA) (includes participants who completed or discontinued early from the main study)

• Known severe allergic reactions to TCZ or other monoclonal antibodies
• Require continuous positive airway pressure (CPAP), bilevel positive airway pressure (BIPAP), or invasive mechanical ventilation
• 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
• Immunocompromised (besides well-controlled HIV) or on immunosuppressive therapy (except for steroids for COVID), advanced cancer
• Have received oral anti-rejection or immunomodulatory drugs (including TCZ) within the past 3 months
• Participating in another interleukin (IL)-6 antagonist clinical trial or other drug clinical trials (participation in COVID-19 anti-viral trials may be permitted if approved by Medical Monitor)
• Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) > 10 x upper limit of normal (ULN) detected within 24 hours at screening (according to local laboratory reference ranges)
• Absolute neutrophil count (ANC) < 1000/uL at screening (according to local laboratory reference ranges)
• Platelet count < 50,000/uL at screening (according to local laboratory reference ranges)
• Pregnant or breastfeeding, or positive pregnancy test in a pre-dose examination
• Treatment with an investigational drug within 5 half lives or 30 days (whichever is longer) of randomization (investigational COVID-19 antivirals may be permitted if approved by Medical Monitor)
• 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
• Any history of Diverticulitis or GI perforation
• Use of systemic corticosteroids unless on a stable chronic dose