Chloroquine is a commonly used antimalarial drug, more toxic than its derivative hydroxychloroquine (Prod. No. AG-CR1-3720). Chloroquine has anti-inflammatory, immunomodulating, anti-infective, antiviral, antithrombotic and metabolic effects. It has anticancer properties, related to their strong antiproliferative, antimutagenic, epigenetic and autophagy inhibiting and apoptosis inducing activities. Chloroquine is used to treat rheumatoid arthritis, systemic lupus erythematosus, antiphospholipid antibody syndrome and Sjögren's syndrome. Chloroquine interfers with lysosomal activity and autophagy, interacts with membrane stability and alters signaling pathways and transcriptional activity, which can result in inhibition of cytokine production and modulation of certain co-stimulatory molecules. Chloroquine shows antiviral activity against several viruses by inhibiting viral replication and inhibits SARS-CoV-2 viral infection (COVID-19) in vitro.