Patients who meet any of the following criteria are NOT eligible for inclusion in the study: 1. Treatment with IMV or ECMO (NIAID-OS 7), 2. Hepatic dysfunction: ALT or AST > 5 ULN, history of chronic hepatic disease (defined with ChildPugh score B or C), 3. Renal dysfunction: estimated glomerular filtration rate (eGFR, MDRD) <50 mL/min/1.73 m2, or need for haemodialysis or hemofiltration, 4. PaO2/FiO2 ratio < 100 mmHg, 5. Treatment with prohibited medication within 5 half-lives, and inability to stop during treatment period, 6. Anticipated discharge from the hospital or transfer to another hospital within 72 hours of screening 7. History of: a. intolerance or hypersensitivity to ibuprofen to more than one medication belonging to the class of sulfonamides, such as sulfamethazine, sulfamethoxazole, sulfasalazine, nimesulide or celecoxib (hypersensitivity to sulphanilamide antibiotics alone, e.g. sulfamethoxazole does not qualify for exclusion) b. lactase deficiency, galactosemia or glucose-galactose malabsorption c. gastrointestinal bleeding or perforation due to previous NSAIDs therapy or recurrent peptic ulcer/haemorrhage 8. Active bleeding or bleeding diathesis (excluding menses), prior intracranial haemorrhage 9. Participation in other interventional clinical trials 10. Clinical condition not compatible with oral administration of the study drug 11. Pregnancy: a) positive or missing pregnancy test before first drug intake or day 1, b) pregnant or lactating women, Women of childbearing potential and fertile men who do not agree to use at least one primary form of contraception for the duration of the study

Patients who meet any of the following criteria are NOT eligible for inclusion in the study: 1. Treatment with IMV or ECMO (NIAID-OS 7), 2. Hepatic dysfunction: ALT or AST > 5 ULN, history of chronic hepatic disease (defined with ChildPugh score B or C), 3. Renal dysfunction: estimated glomerular filtration rate (eGFR, MDRD) <50 mL/min/1.73 m2, or need for haemodialysis or hemofiltration, 4. PaO2/FiO2 ratio < 100 mmHg, 5. Treatment with prohibited medication within 5 half-lives, and inability to stop during treatment period, 6. Anticipated discharge from the hospital or transfer to another hospital within 72 hours of screening 7. History of: a. intolerance or hypersensitivity to ibuprofen to more than one medication belonging to the class of sulfonamides, such as sulfamethazine, sulfamethoxazole, sulfasalazine, nimesulide or celecoxib (hypersensitivity to sulphanilamide antibiotics alone, e.g. sulfamethoxazole does not qualify for exclusion) b. lactase deficiency, galactosemia or glucose-galactose malabsorption c. gastrointestinal bleeding or perforation due to previous NSAIDs therapy or recurrent peptic ulcer/haemorrhage 8. Active bleeding or bleeding diathesis (excluding menses), prior intracranial haemorrhage 9. Participation in other interventional clinical trials 10. Clinical condition not compatible with oral administration of the study drug 11. Pregnancy: a) positive or missing pregnancy test before first drug intake or day 1, b) pregnant or lactating women, Women of childbearing potential and fertile men who do not agree to use at least one primary form of contraception for the duration of the study