Chemistry, molecular and cell biology, and nutritional sciences and toxicology professor Daniel Nomura, an investigator in the Berkeley-UCSF Innovative Genomics Institute, has been working with the pharmaceutical company Novartis on ways of developing drugs that harness proteins using cysteine-reactive probes. That work is now being adapted in efforts to fight COVID-19 by targeting the virus's proteins. Speaking of the main protease they're investigating, he says: "This enzyme is really well behaved and has at the center of it this amino acid -- a cysteine -- that coordinates the chemistry. ... We have this very large library of cysteine-targeting covalent ligands that we've been building out over many years. ... We thought that was a perfect way into targeting the catalytic cysteine of what I would consider a highly druggable protein."