Kumar and coworkers [120] synthesized multiple pyrazolone analogues as SARS-coronavirus (CoV) and Middle East Respiratory Syndrome (MERS)-CoV 3C-like protease inhibitors, among which compounds 167 and 168 (Fig. 16 ) exerted the strongest inhibitory effects against SARS and MERS with IC 50 values of 6.4 and 5.8 mM (167), 5.8 and 7.4 mM (168), respectively.