Apparently the possible utility of chloroquine was discovered because SLE patients on it in China weren't getting Covid-19 during the outbreak [0]. [0]: https:

Apparently the possible utility of chloroquine was discovered because SLE patients on it in China weren't getting Covid-19 during the outbreak [0]. [0]: https://www.jqknews.com/news/388543-The_novel_coronavirus_pneumonia_has_short_term_curative_effect_on_the_treatment_of_new_crown_pneumonia.html https://www.jqknews.com/news/388543-The_novel_coronavirus_pn...