Antimalarial Drugs as Immune Modulators: New Mechanisms for Old Drugs

The best known of the naturally occurring antimalarial compounds are quinine, extracted from cinchona bark, and artemisinin (qinghao), extracted from Artemisia annua in China. These and other derivatives are now chemically synthesized and remain the mainstay of therapy to treat malaria. The beneficial effects of several of the antimalarial drugs (AMDs) on clinical features of autoimmune disorders were discovered by chance during World War II. In this review, we discuss the chemistry of AMDs and their mechanisms of action, emphasizing how they may impact multiple pathways of innate immunity. These pathways include Toll-like receptors and the recently described cGAS-STING pathway. Finally, we discuss the current and future impact of AMDs on systemic lupus erythematosus, rheumatoid arthritis, and devastating monogenic disorders (interferonopathies) characterized by expression of type I interferon in the brain.