Chloroquine and hydroxychloroquine are widely used anti-malarial drugs with well-known immunomodulatory properties that have extended their use to several immuno-rheumatological diseases including RA [83]. The ability of chloroquine to produce an anti-viral effect has been known since the late 1960s [84]. Several mechanisms by which the drug is able to interfere with the growth and spread of different viruses (including SARS coronavirus) have been demonstrated in in vitro studies [85], even though the subsequent in vivo experience was controversial [86,87].