* participation in any other clinical trial of an experimental treatment for covid-19, unless related to an expanded access program as part of standard of care at screening or during study. * evidence of multiorgan failure. * requiring mechanical ventilation at screening. * alanine aminotransferase (alt) or aspartate aminotransferase (ast) \> 5 x upper limit of normal (uln) at screening. * creatinine clearance \< 30 ml/min at screening. * pregnancy or lactation at screening. * allergy or other contraindication or one of ensifentrine. * in the opinion of the clinical team, progression to death is imminent and inevitable within the next 24 hours, irrespective of the provision of treatments. * use of prohibited medications (theophylline, pde4 inhibitors \[e.g. roflumilast, apremilast, crisaborole\] within 48 hours of screening or during study) * any other reason that the investigator considers makes the patient unsuitable to participate.

* participation in any other clinical trial of an experimental treatment for covid-19, unless related to an expanded access program as part of standard of care at screening or during study. * evidence of multiorgan failure. * requiring mechanical ventilation at screening. * alanine aminotransferase (alt) or aspartate aminotransferase (ast) \> 5 x upper limit of normal (uln) at screening. * creatinine clearance \< 30 ml/min at screening. * pregnancy or lactation at screening. * allergy or other contraindication or one of ensifentrine. * in the opinion of the clinical team, progression to death is imminent and inevitable within the next 24 hours, irrespective of the provision of treatments. * use of prohibited medications (theophylline, pde4 inhibitors \[e.g. roflumilast, apremilast, crisaborole\] within 48 hours of screening or during study) * any other reason that the investigator considers makes the patient unsuitable to participate.

- participation in any other clinical trial of an experimental treatment for covid-19, unless related to an expanded access program as part of standard of care at screening or during study. - evidence of multiorgan failure. - requiring mechanical ventilation at screening. - alanine aminotransferase (alt) or aspartate aminotransferase (ast) > 5 x upper limit of normal (uln) at screening. - creatinine clearance < 30 ml/min at screening. - pregnancy or lactation at screening. - allergy or other contraindication or one of ensifentrine. - in the opinion of the clinical team, progression to death is imminent and inevitable within the next 24 hours, irrespective of the provision of treatments. - use of prohibited medications (theophylline, pde4 inhibitors [e.g. roflumilast, apremilast, crisaborole] within 48 hours of screening or during study) - any other reason that the investigator considers makes the patient unsuitable to participate.

- participation in any other clinical trial of an experimental treatment for covid-19, unless related to an expanded access program as part of standard of care at screening or during study. - evidence of multiorgan failure. - requiring mechanical ventilation at screening. - alanine aminotransferase (alt) or aspartate aminotransferase (ast) > 5 x upper limit of normal (uln) at screening. - creatinine clearance < 30 ml/min at screening. - pregnancy or lactation at screening. - allergy or other contraindication or one of ensifentrine. - in the opinion of the clinical team, progression to death is imminent and inevitable within the next 24 hours, irrespective of the provision of treatments. - use of prohibited medications (theophylline, pde4 inhibitors [e.g. roflumilast, apremilast, crisaborole] within 48 hours of screening or during study) - any other reason that the investigator considers makes the patient unsuitable to participate.