Inclusion Criteria:  Part 1 only, patients with a primary diagnosis of COVID-19, with or without pneumonia, who agree to be monitored daily for at least 7 days after randomization and who accept continuing to be assessed for the study procedures. Part 2 only, patients with a primary diagnosis of COVID-19, with or without pneumonia.  Exclusion Criteria:  At the time of randomization, patients who require intensive care unit (ICU) admission or patients with severe respiratory insufficiency who require mechanical ventilation or with rapid worsening of respiratory function leading to expectation for mechanical ventilation or ICU admission. Evidence of rapid clinical deterioration or existence of any life-threatening co-morbidity or any other medical condition that, in the opinion of the investigator, makes the patient unsuitable for inclusion. Patients who, at the time of enrollment, are not in a clinical condition compatible with the oral administration of the study drug.