Assessment of Efficacy and Safety of Ruxolitinib in Participants With COVID-19-Associated ARDS Who Require Mechanical Ventilation (RUXCOVID-DEVENT)

Inclusion Criteria: * Participant or guardian health proxy must provide informed consent before any study assessment is performed. * Male or female participants aged ≥ 12 years. * Participants with coronavirus (SARS-CoV-2) infection confirmed ≤ 3 weeks prior to randomization by any test with local regulatory approval. * Participants who are intubated and receiving mechanical ventilation due to COVID-19-associated ARDS and have a PaO2/FiO2 of ≤ 300 mmHg within 6 -hours of randomization. Participants with lung imaging showing bilateral or diffuse pulmonary infiltrates on chest x-ray or CT scan. Exclusion Criteria: * Known history of hypersensitivity to any drugs or metabolites of similar chemical classes as ruxolitinib. * Presence of severely impaired renal function defined by estimated creatinine clearance \< 15 mL/min measured or calculated by Cockcroft-Gault equation or calculated by the updated bedside Schwartz equation. Participants must not be receiving CRRT or intermittent hemodialysis at screening. * In the opinion of the investigator, unlikely to survive for \> 24 hours from randomization. * Suspected active uncontrolled bacterial, fungal, viral, or other infection (besides COVID-19). * Currently receiving ECMO. * Participant may not be sharing a ventilator, or co-ventilating, with any other patient. * Treatment with anti-IL-6, IL-6R, IL-1RA, IL-1β, or GM-CSF antagonists, or a BTK inhibitor, within 7 days of randomization. * Treatment with a JAK inhibitor within 30 days of randomization. * Participants who are on long-term use of antirejection or immunomodulatory drugs. * Pregnant or nursing (lactating) women.