Chloroquine was discovered in 1934 by Hans Andersag and co-workers at the Bayer laboratories who named it "Resochin". It was ignored for a decade because it was considered too toxic for human use. During World War II, United States government-sponsored clinical trials for anti-malarial drug development showed unequivocally that chloroquine has a significant therapeutic value as an anti-malarial drug. It was introduced into clinical practice in 1947 for the prophylactic treatment of malaria.^[1]

• It has long been used in the treatment or prevention of malaria. After the malaria parasite Plasmodium falciparum started to develop widespread resistance to chloroquine,^[2][3] new potential utilisations of this cheap and widely available drug have been investigated. Chloroquine has been extensively used in mass drug administrations which may have contributed to the emergence and spread of resistance.

• As it mildly suppresses the immune system, it is used in some autoimmune disorders, such as rheumatoid arthritis and lupus erythematosus.

• Chloroquine is in clinical trials as an investigational antiretroviral in humans with HIV-1/AIDS and as a potential antiviral agent against chikungunya fever.^[4]

• The radiosensitizing and chemosensitizing properties of chloroquine are beginning to be exploited in anticancer strategies in humans.^[5][6]