COVID-19
Some scientists also think the drug remdesivir, which was invented as a medicine for Ebola, could work against SARS-CoV-2.  Remdesivir works against other viruses and it has already been tested in humans, so the doctors already knew it would not hurt the patients even if it did not make them better.  Because scientists already knew remdesivir was safe, they were able to start testing it in humans right away.