1. In the opinion of the clinical team, progression to intubation or mechanical ventilation is imminent and inevitable, within the next 24 hours, irrespective of the provision of treatments. 2. Patients admitted with primary suspected or proven Mycoplasma pneumoniae, Chlamydia pneumoniae and bacterial pneumonia, who acquired COVID-19 while hospitalized. 3. Treatment with immunomodulators or anti-rejection drugs within the last 3 months. 4. Pregnant or breast feeding. 5. Men, and women of child-bearing potential, unwilling to use highly effective contraception during their participation in the trial and for 2 weeks after study completion. 6. Anticipated transfer to another hospital which is not a study site within 72 hours. 7. Known sensitivity to any of the study medication/placebo excipients. 8. Prior dosing with AZD1656 on a previous clinical trial. 9. Patients admitted as a result of and receiving immediate treatment for an acute asthmatic attack, acute myocardial infarction, acute cerebrovascular event. 10. Any known non-COVID-19, non-diabetes related, serious condition which, in the opinion of the clinical team, makes the patient unsuitable for the trial. 11. Known history of drug or alcohol abuse within previous 12 months of screening. 12. Known history of HIV, hepatitis C or unresolved hepatitis B or severe liver disease. 13. Current or planned use of gemfibrozil or any other strong inhibitors of CYP2C8. 14. Current or previous participation in another clinical trial where the patient has received a dose of an Investigational Medicinal Product (IMP) containing small molecule treatment(s) within 30 days or 5 half-lives (whichever is longer) prior to enrolment into this study, or containing biological treatment(s) within 3 months prior to entry into this study.

1. In the opinion of the clinical team, progression to intubation or mechanical ventilation is imminent and inevitable, within the next 24 hours, irrespective of the provision of treatments. 2. Patients admitted with primary suspected or proven Mycoplasma pneumoniae, Chlamydia pneumoniae and bacterial pneumonia, who acquired COVID-19 while hospitalized. 3. Treatment with immunomodulators or anti-rejection drugs within the last 3 months. 4. Pregnant or breast feeding. 5. Men, and women of child-bearing potential, unwilling to use highly effective contraception during their participation in the trial and for 2 weeks after study completion. 6. Anticipated transfer to another hospital which is not a study site within 72 hours. 7. Known sensitivity to any of the study medication/placebo excipients. 8. Prior dosing with AZD1656 on a previous clinical trial. 9. Patients admitted as a result of and receiving immediate treatment for an acute asthmatic attack, acute myocardial infarction, acute cerebrovascular event. 10. Any known non-COVID-19, non-diabetes related, serious condition which, in the opinion of the clinical team, makes the patient unsuitable for the trial. 11. Known history of drug or alcohol abuse within previous 12 months of screening. 12. Known history of HIV, hepatitis C or unresolved hepatitis B or severe liver disease. 13. Current or planned use of gemfibrozil or any other strong inhibitors of CYP2C8. 14. Current or previous participation in another clinical trial where the patient has received a dose of an Investigational Medicinal Product (IMP) containing small molecule treatment(s) within 30 days or 5 half-lives (whichever is longer) prior to enrolment into this study, or containing biological treatment(s) within 3 months prior to entry into this study.