History records that in the 17th century the Peruvians (South America) used the extract of the bark of the Cinchona tree to fight fever and chills. In 1633 this extract was introduced in Europe for the same treatment and used to treat malaria. Quinine was isolated from the extract in 1820 and chloroquine is an analog of quinine.
In 1934 Hans Andersag of Bayer Laboratories (a German pharmaceutical company) discovered chloroquine and gave it the brand name Resochin. It was ignored for many years because it was considered too toxic. However, during WWII the US government sponsored clinical trials and found chloroquine to be an effective antimalarial drug. In 1947 it was put into clinical practice as a prophylactic antimalarial.
Besides its use in malaria, it is also used to treat Amebiasis (amoebic infection) and rheumatic diseases.
Very recently it has shown favorable results in the treatment of patients infected with the COVID-19 or SARS-CoV-2 viruses. When administered along with azithromycin there have been favorable therapeutic outcomes in patients.
One of the suspected mechanisms related to its antiviral activity is that chloroquine is a zinc ionophore, thereby allowing more uptake of zinc into a cell’s cytoplasm inhibiting the viral RNA dependent RNA polymerase.
Source: https://en.wikipedia.org/wiki/Chloroquine#History and https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4182877/
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