CSL324 in COVID-19

Inclusion Criteria: * Age ≥ 18 years at the time informed consent is obtained * Positive for SARS-CoV-2 infection determined by a diagnostic test approved by the Food and Drug Administration (FDA) or allowed under an emergency use authorization * Chest computed tomography (CT) scan or X ray results confirming interstitial pneumonia * Meets ≥ 1 of the following criteria (subjects improving while on respiratory support still qualify): * Respiratory rate \> 30 breaths per minute * Peripheral (capillary) oxygen saturation (SpO2) ≤ 93% on room air * Partial pressure of oxygen in arterial blood (PaO2) to fraction of inspired oxygen (FiO2) ratio (PaO2 / FiO2) \< 300 * SpO2 / FiO2 ratio \< 218 (if PaO2 / FiO2 ratio is not available) * Radiographic lung infiltrates \> 50% Exclusion Criteria: * Currently enrolled, planning to enroll, or participated, within the last 30 days, in a clinical study requiring administration of an investigational product (ie, not yet marketed), including expanded access or compassionate use * Exceptions: * Administration of investigational product with emergency use authorization granted for treatment of COVID 19 (eg, remdesivir) is permitted * Convalescent plasma as part of approved special access programs such as expanded access, emergency IND, or compassionate use is permitted * Pregnant or breastfeeding (female subjects) * Intubated and requires mechanical ventilation (including ECMO) at time of randomization * Exception: use of HFNC oxygen and noninvasive ventilation are permitted * Endotracheal intubation is imminent, in the opinion of the investigator * Not expected to survive for more than 48 hours after hospital admission, in the opinion of the investigator * Presence of any of the following comorbid conditions before randomization and prior to SARS-CoV-2 infection: * New York Heart Association class IV heart failure * Stage 4 or 5 chronic kidney disease or requires renal replacement therapy * Biopsy proven cirrhosis, portal hypertension or hepatic encephalopathy * Stage IV malignancy * Chronic lung disease requiring home oxygen * Active tuberculosis * History or evidence of pulmonary alveolar proteinosis * Confirmed diagnosis or clinical suspicion of bacterial pneumonia or active uncontrolled bacterial, fungal, or non SARS-CoV-2 viral infection at Screening * Absolute neutrophil count (ANC) value \< 5 × 109 cells/L at Screening (can be lowered up to \< 1.5 × 109 cells/L after Independent Data Monitoring Committee review of safety data, if CSL324 induced neutropenia is not assessed as a safety concern) * Currently receiving a prohibited therapy including G-CSF, granulocyte-macrophage colony-stimulating factor (GM-CSF), or antibody against interleukin 6 (IL-6) / IL 6 receptor (anti IL-6 / 6R)