All viruses, including SARS-CoV-2, the virus that causes COVID-19, have the same goal: invade our cells, use our cells’ internal machinery to make copies of itself, and then release the newly made virus to infect more of our cells. But protease inhibitors, a class of drugs long used to treat HIV and hepatitis C, have been shown to stop this process — known as the viral life cycle. These drugs work by blocking a critical enzyme, a protease, that the virus needs to replicate. Read on to learn more.