Unlikely to survive for >48 hours from screening Participants with critical disease or multi-organ failure Any contraindication to HCQ or intolerance to HCQ Any medical condition or concomitant therapy that may put the particpants at risk if they are treated with HCQ Pregnant or breastfeeding women Use of antiarrhythmic medications and medications known to prolong QT interval or cause Torsades de Pointes (TdPs) Participants with history of congenital or acquired long QT, arrhythmia, family history of long QT or sudden cardiac death, or any other cardiac condition that, by the judgement of the Investigator, would put the patient at higher risk for QTc prolongation or sudden cardiac death Participants with the following ECG findings at screening: QTcF >470 msec for women or >450 msec for men or heart rate <50 beats/minute Participants with known glucose-6-phosphate dehydrogenase (G6PD) deficiency

Unlikely to survive for >48 hours from screening Participants with critical disease or multi-organ failure Any contraindication to HCQ or intolerance to HCQ Any medical condition or concomitant therapy that may put the particpants at risk if they are treated with HCQ Pregnant or breastfeeding women Use of antiarrhythmic medications and medications known to prolong QT interval or cause Torsades de Pointes (TdPs) Participants with history of congenital or acquired long QT, arrhythmia, family history of long QT or sudden cardiac death, or any other cardiac condition that, by the judgement of the Investigator, would put the patient at higher risk for QTc prolongation or sudden cardiac death Participants with the following ECG findings at screening: QTcF >470 msec for women or >450 msec for men or heart rate <50 beats/minute Participants with known glucose-6-phosphate dehydrogenase (G6PD) deficiency