* patients requiring mechanical ventilation (intubation or bi-pap) at the time randomization. * patients receiving any investigational drugs other than drugs or therapies to treat covid-19, with the exception of investigational immune-modulatory drugs as per section 5.4. * pregnant women are excluded from this study because duvelisib is agent with the potential for teratogenic or abortifacient effects. because there is an unknown but potential risk for adverse events in nursing infants secondary to treatment of the mother with duvelisib, breastfeeding should be discontinued before starting study drug and breastfeeding should not be resumed until at least 1 month after last dose of study drug. * clinical suspicion that the etiology of acute illness (acute decompensation) is primarily due to a condition other than covid-19 * known contraindication to duvelisib * patients with hepatic cirrhosis as defined by symptomatic liver dysfunction; liver fibrosis by biopsy; alt \> 5 times uln, ast\> 5 times uln, or bilirubin \> 3 times uln. * patients with autoimmune diseases or patients on chronic immunosuppressive medications at the time of hospital admission or screening.

* patients requiring mechanical ventilation (intubation or bi-pap) at the time randomization. * patients receiving any investigational drugs other than drugs or therapies to treat covid-19, with the exception of investigational immune-modulatory drugs as per section 5.4. * pregnant women are excluded from this study because duvelisib is agent with the potential for teratogenic or abortifacient effects. because there is an unknown but potential risk for adverse events in nursing infants secondary to treatment of the mother with duvelisib, breastfeeding should be discontinued before starting study drug and breastfeeding should not be resumed until at least 1 month after last dose of study drug. * clinical suspicion that the etiology of acute illness (acute decompensation) is primarily due to a condition other than covid-19 * known contraindication to duvelisib * patients with hepatic cirrhosis as defined by symptomatic liver dysfunction; liver fibrosis by biopsy; alt \> 5 times uln, ast\> 5 times uln, or bilirubin \> 3 times uln. * patients with autoimmune diseases or patients on chronic immunosuppressive medications at the time of hospital admission or screening.

- patients requiring mechanical ventilation (intubation or bi-pap) at the time randomization. - patients receiving any investigational drugs other than drugs or therapies to treat covid-19, with the exception of investigational immune-modulatory drugs as per section 5.4. - pregnant women are excluded from this study because duvelisib is agent with the potential for teratogenic or abortifacient effects. because there is an unknown but potential risk for adverse events in nursing infants secondary to treatment of the mother with duvelisib, breastfeeding should be discontinued before starting study drug and breastfeeding should not be resumed until at least 1 month after last dose of study drug. - clinical suspicion that the etiology of acute illness (acute decompensation) is primarily due to a condition other than covid-19 - known contraindication to duvelisib - patients with hepatic cirrhosis as defined by symptomatic liver dysfunction; liver fibrosis by biopsy; alt > 5 times uln, ast> 5 times uln, or bilirubin > 3 times uln. - patients with autoimmune diseases or patients on chronic immunosuppressive medications at the time of hospital admission or screening.

- patients requiring mechanical ventilation (intubation or bi-pap) at the time randomization. - patients receiving any investigational drugs other than drugs or therapies to treat covid-19, with the exception of investigational immune-modulatory drugs as per section 5.4. - pregnant women are excluded from this study because duvelisib is agent with the potential for teratogenic or abortifacient effects. because there is an unknown but potential risk for adverse events in nursing infants secondary to treatment of the mother with duvelisib, breastfeeding should be discontinued before starting study drug and breastfeeding should not be resumed until at least 1 month after last dose of study drug. - clinical suspicion that the etiology of acute illness (acute decompensation) is primarily due to a condition other than covid-19 - known contraindication to duvelisib - patients with hepatic cirrhosis as defined by symptomatic liver dysfunction; liver fibrosis by biopsy; alt > 5 times uln, ast> 5 times uln, or bilirubin > 3 times uln. - patients with autoimmune diseases or patients on chronic immunosuppressive medications at the time of hospital admission or screening.