Several hundred trials of potential treatments for the coronavirus are now underway around the world. Early results suggest a few might slightly reduce the risk of dying from covid-19, but we won’t know for sure until larger trials have been completed.

“The good news is that there is a lot of activity,” says Trudie Lang at the University of Oxford. “Sadly, however, we don’t actually have anything that works as yet.”

There are two main approaches. One is …