* 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.

* 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.

- 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.

- 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.