In late 2019, cases of an unknown respiratory tract infection were first reported in Wuhan, China. By February 2020, the novel coronavirus SARS CoV-2 was identified as the causative agent for COVID-19.1,2 Genome analysis of this virus revealed a high similarity to SARS CoV-1, the coronavirus that caused severe acute respiratory syndrome (SARS) in 2002–2003.2−4 Like SARS CoV-1, which resulted in 799 deaths among the 8464 probable cases,5 SARS CoV-2 can induce fever, coughing, and difficulty breathing that rapidly becomes more serious in some cases. The spread of SARS CoV-2 has been more extensive than that of SARS CoV-1, causing a global pandemic with the current number of worldwide infections surpassing eight million and deaths surpassing 400,000.6 The SARS CoV-1 genome encodes for two large polyproteins pp1a (∼450 kDa) and pp1ab (∼750 kDa) that contain overlapping sequences and include a 3C-like cysteine protease (3CLpro). The function of this internally encoded 3CLpro is integral to the processing of these proteins and critical for viral replication.7 The SARS CoV-1 3CLpro shares a high degree of structural homology and similar substrate specificity with the coronavirus 3C-like cysteine proteases of hCoV 229E and TGEV8 but is most similar to the SARS CoV-2 3CLpro. Specifically, the SARS CoV-1 and SARS CoV-2 share 96% identity between their respective 3CLpro sequences and 100% identity in the active site.8 A recent report by Dai et al. demonstrates that crystallographic information and structure–activity relationships obtained with the SARS CoV-1 3CLpro could facilitate the design of potent SARS CoV-2 3CLpro inhibitors with antiviral potency.9