The SARS-CoV-2 spike protein trimer in the prefusion conformation was obtained from pdb file # 6VSB [20]. Hydroxychloroquine (CLQ-OH) is (RS)-2-[{4-[(7-chloroquinolin-4-yl)amino]pentyl}(ethyl)amino]ethanol. CLQ-OH was generated by hydroxylation of chloroquine (CLQ) and validated as previously described [10]. CLQ was retrieved from pdb file # 4V2O (CLQ co-crystallized with saposin B) [21].