Severe acute respiratory syndrome coronavirus 2
Some scientists thought the drug remdesivir, which was invented as a medicine for Ebola, could work against SARS-CoV-2.  Remdesivir works against some viruses.  Remdesivir had 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.