Although doctors and scientists are testing a vast arsenal of existing drugs and drug candidates in the fight against the novel coronavirus, SARS-CoV-2, EIDD-2801 stands out. It attacks the same viral enzyme, the RNA-dependent RNA polymerase, as Gilead Sciences’ remdesivir, which the US Food and Drug Administration recently granted emergency use authorization, allowing it to be used by doctors in the pandemic. But unlike remdesivir, which has to be given intravenously, EIDD-2801 can be taken orally as a pill.

This means if EIDD-2801 is shown to be safe and effective, people could take it at home rather than in a hospital. That would allow EIDD-2801 to be taken earlier in the course of the disease, killing off the virus before it wreaks havoc on the body.

EIDD-2801’s other intriguing feature is that it appears to have a high barrier to resistance. Drugs can force viruses to quickly develop mutants that aren’t affected by the drug, which then makes the drug obsolete. But EIDD-2801 hasn’t prompted that sort of resistance in lab tests despite efforts to coerce such mutants to arise.