Another peptidic drug with a Michael acceptor was N3 (40), which was reported to inhibit SARS‐CoV‐1 3CLpro (K i, 9.0 µM) by Yang et al. It was observed to be a broad‐spectrum antiviral compound, also inhibiting other CoVs, such as MERS‐CoV Mpro (IC50, 0.28µM), 135  HCoV‐229E, HCoV‐NL63, and HCoV‐HKU1 Mpro. 135 ,  136 ,  137 ,  138  It has also exhibited high antiviral activity in an animal model of infectious bronchitis virus. 137  The CC50 of 40 is greater than 133 μM.