We recently reported that K777, or K11777, a di-peptide vinyl sulfone inactivator of the trypanosomal cysteine protease, cruzain (Scheme 1), which had been a clinical candidate for Chagas disease (McKerrow et al., 2009), was an exceptionally potent anti-SARS-CoV-2 agent (Mellott et al., 2021). The gene discussed is CTSB; the disease is Chagas disease.