1. Subjects with suspected severe or moderately severe pneumonia, presenting with any of the following: respiratory rate > 26 breaths/min, significant respiratory distress, or SpO2 ≤94 % on room air, 2. Subjects requiring treatment in the hospital, according to the treating physician’s judgement, 3. Subjects having any contraindication to treatment with HCQ, such as a long QTc interval (>450 ms in men, >470 ms in women), porphyria, epilepsy, severe renal insufficiency, 4. Screening 12-lead ECG results showing evidence of clinically significant disturbances of cardiac rhythm or impulse conduction. Atrial fibrillation, paroxysmal supraventricular tachycardia or supraventricular extrasystoles are not exclusionary, 5. Cardiac insufficiency of NYHA Class 3-4, 6. History of stroke, within 6 months of screening, 7. Subjects with a history of seizures within one year of screening, 8. Subjects with a history of drowning accident, 9. Any psychiatric diagnosis or symptoms (e.g., hallucinations, major depression, delusions, schizophrenia, bipolar disorder) that, in the opinion of the investigator, could interfere with study procedures or assessments or subject safety, 10. Disorder related to alcohol or drug abuse, as defined in DSM-5-TR, within one year prior to screening, 11. Evidence of current or history of any significant autoimmune disease that, in the opinion of the investigator, could interfere with evaluation of the study results or constitute a health hazard for the subject, 12. Evidence of an immune system that is compromised, including, but not limited to, a diagnosis of HIV, or the subject has been splenectomised or has received an organ transplant (corneal transplants excluded), or is receiving chronic systemic immunosuppressive medication, 13. Evidence of current clinically significant and possibly unstable pulmonary, gastrointestinal, renal, hepatic, endocrine, haematological or cardiovascular system disease or metabolic disturbance, 14. Diagnosis of cancer (haematological or solid tumour) for which the subject is currently being treated, or for which there is evidence of active disease. Subjects with local prostate cancer or local dermatological tumours, such as basal or squamous cell carcinoma, may be included, 15. Any clinically significant abnormalities in laboratory tests, vital signs, ECG or physical examination findings at screening that in the opinion of the investigator require further investigation or treatment or may interfere with study procedures or safety. These may include, but are not limited to, the following: a. estimated glomerular filtration ratio (eGFR) < 30 ml/min/1.73 m2, based on the CKD-EPI equation, b. a plasma total bilirubin value >2 times the upper limit of the reference range, c. plasma alanine aminotransferase (ALT) or aspartate aminotransferase (AST) value >3 times the upper limit of the reference range, 16. Current or anticipated use or recent prior use (pre-study time limits specified in Section 5.4 of the protocol) of disallowed concomitant treatment, use of concomitant medications that prolong the QTc interval is not allowed (see Appendix 1), 17. Having received in another clinical trial any other investigational medication (unless it can be documented that the subject received only placebo) within 3 months or 5 half-lives (whichever is longer) before screening, 18. Disease or medication that, in the opinion of the investigator, could seriously impact the assessments of safety, tolerability or efficacy. 19. Pregnancy or breast-feeding.

1. Subjects with suspected severe or moderately severe pneumonia, presenting with any of the following: respiratory rate > 26 breaths/min, significant respiratory distress, or SpO2 ≤94 % on room air, 2. Subjects requiring treatment in the hospital, according to the treating physician’s judgement, 3. Subjects having any contraindication to treatment with HCQ, such as a long QTc interval (>450 ms in men, >470 ms in women), porphyria, epilepsy, severe renal insufficiency, 4. Screening 12-lead ECG results showing evidence of clinically significant disturbances of cardiac rhythm or impulse conduction. Atrial fibrillation, paroxysmal supraventricular tachycardia or supraventricular extrasystoles are not exclusionary, 5. Cardiac insufficiency of NYHA Class 3-4, 6. History of stroke, within 6 months of screening, 7. Subjects with a history of seizures within one year of screening, 8. Subjects with a history of drowning accident, 9. Any psychiatric diagnosis or symptoms (e.g., hallucinations, major depression, delusions, schizophrenia, bipolar disorder) that, in the opinion of the investigator, could interfere with study procedures or assessments or subject safety, 10. Disorder related to alcohol or drug abuse, as defined in DSM-5-TR, within one year prior to screening, 11. Evidence of current or history of any significant autoimmune disease that, in the opinion of the investigator, could interfere with evaluation of the study results or constitute a health hazard for the subject, 12. Evidence of an immune system that is compromised, including, but not limited to, a diagnosis of HIV, or the subject has been splenectomised or has received an organ transplant (corneal transplants excluded), or is receiving chronic systemic immunosuppressive medication, 13. Evidence of current clinically significant and possibly unstable pulmonary, gastrointestinal, renal, hepatic, endocrine, haematological or cardiovascular system disease or metabolic disturbance, 14. Diagnosis of cancer (haematological or solid tumour) for which the subject is currently being treated, or for which there is evidence of active disease. Subjects with local prostate cancer or local dermatological tumours, such as basal or squamous cell carcinoma, may be included, 15. Any clinically significant abnormalities in laboratory tests, vital signs, ECG or physical examination findings at screening that in the opinion of the investigator require further investigation or treatment or may interfere with study procedures or safety. These may include, but are not limited to, the following: a. estimated glomerular filtration ratio (eGFR) < 30 ml/min/1.73 m2, based on the CKD-EPI equation, b. a plasma total bilirubin value >2 times the upper limit of the reference range, c. plasma alanine aminotransferase (ALT) or aspartate aminotransferase (AST) value >3 times the upper limit of the reference range, 16. Current or anticipated use or recent prior use (pre-study time limits specified in Section 5.4 of the protocol) of disallowed concomitant treatment, use of concomitant medications that prolong the QTc interval is not allowed (see Appendix 1), 17. Having received in another clinical trial any other investigational medication (unless it can be documented that the subject received only placebo) within 3 months or 5 half-lives (whichever is longer) before screening, 18. Disease or medication that, in the opinion of the investigator, could seriously impact the assessments of safety, tolerability or efficacy. 19. Pregnancy or breast-feeding.