human use. instead, in world war ii, the german africa corps used the chloroquine analogue 3-methyl-chloroquine, known as sontochin. after allied forces arrived in tunis, sontochin fell into the hands of americans, who sent the material back to the united states for analysis, leading to renewed interest in chloroquine. united states government-sponsored clinical trials for antimalarial drug development showed unequivocally that chloroquine has a significant therapeutic value as an antimalarial drug.: 61–66 it was introduced into clinical practice in 1947 for the prophylactic treatment of malaria. chemical synthesis the first synthesis of chloroquine was disclosed in a patent filed by ig farben in 1937. in the final step, 4,7-dichloroquinoline was reacted with 1-diethylamino-4-aminopentane. by 1949, chloroquine manufacturing processes had been established to allow its widespread use. society and culture resochin tablet package formulations chloroquine comes in tablet form as the phosphate, sulfate, and hydrochloride salts. chloroquine is usually dispensed as the phosphate. names brand names include chloroquine fna, resochin, dawaquin, and lariago. other animals chloroquine, in various chemical forms, is used to treat and control surface growth of anemones and algae, and many protozoan infections in aquariums, e.g. the fish parasite amyloodinium ocellatum. it is also used in poultry malaria.: 1237 research chloroquine was proposed as a treatment for sars, with in vitro tests inhibiting the severe acute respiratory syndrome coronavirus (sars-cov). in october 2004, a published report stated that chloroquine acts as an effective inhibitor of the replication of sars-cov in vitro. in august 2005, a peer-reviewed study confirmed and expanded upon the results. chloroquine was being considered in 2003, in pre-clinical models as a potential agent against chikungunya fever. covid-19 this section is an excerpt from chloroquine and hydroxychloroquine during the covid-19 pandemic. a world health organization infographic that states that hydroxychloroquine does not prevent illness or death from covid-19. chloroquine and hydroxychloroquine are anti-malarial medications also used against some auto-immune diseases. chloroquine, along with hydroxychloroquine, was an early experimental treatment for covid-19. neither drug prevents sars-cov-2 infection. cleavage of the sars-cov-2 s2 spike protein required for viral entry into cells can be accomplished by proteases tmprss2 located on the cell membrane, or by cathepsins (primarily cathepsin l) in endolysosomes. hydroxychloroquine inhibits the action of cathepsin l in endolysosomes, but because cathepsin l cleavage is minor compared to tmprss2 cleavage, hydroxychloroquine does little to inhibit sars-cov-2 infection. several countries initially used chloroquine or hydroxychloroquine for treatment of persons hospitalized with covid-19 (as of march 2020), though the drug was not formally approved through clinical trials. from april to june 2020, there was an emergency use authorization for their use in the united states, and was used off label for potential treatment of the disease. on 24 april 2020, citing the risk of "serious heart rhythm problems", the fda posted a caution against using the drug for covid-19 "outside of the hospital setting or a clinical trial". their use was withdrawn as a possible treatment for covid-19 infection when it proved to have no benefit for hospitalized patients with severe covid-19 illness in the international solidarity trial and uk recovery trial. on 15 june 2020, the fda revoked its emergency use authorization, stating that it was "no longer reasonable to believe" that the drug was effective against covid-19 or that its benefits outweighed "known and potential risks". in fall of 2020, the national institutes of health issued treatment guidelines recommending against the use of hydroxychloroquine for covid-19 except as part of a clinical trial. in 2021, hydroxychloroquine was part of the recommended treatment for mild cases in india. in 2020, the speculative use of hydroxychloroquine for covid-19 threatened its availability for people with established indications (malaria and auto-immune diseases). other the radiosensitizing and chemosensitizing properties of chloroquine are being evaluated for anticancer strategies in humans. in biomedicinal science, chloroquine is used for in vitro experiments to inhibit lysosomal degradation of protein products. chloroquine and its modified forms have also been evaluated as treatment options for inflammatory conditions like rheumatoid arthritis and inflammatory bowel disease.