Hydroxychloroquine is a synthetic less toxic derivative of chloroquine (Prod. No. AG-CR1-3721), commonly used as an antimalarial drug. Hydroxychloroquine 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. Hydroxychloroquine is used to treat rheumatoid arthritis, systemic lupus erythematosus, antiphospholipid antibody syndrome and Sjögren's syndrome. Hydroxychloroquine 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. It increases lysosomal pH in antigen-presenting cells and blocks in inflammatory conditions, toll-like receptors on plasmacytoid dendritic cells (PDCs). By decreasing TLR signaling, it reduces the activation of dendritic cells and the inflammatory process. It also acts as an antagonist TLR7 and TLR9. Hydroxychloroquine shows antiviral activity against several viruses by inhibiting viral replication and inhibits SARS-CoV-2 viral infection (COVID-19), in vitro.