Niclosamide (181; Figure 39), an anthelmintic drug, exhibited very potent antiviral activity against SARS‐CoV‐1 replication and stopped viral antigen synthesis at 1.56 μM concentrations. 238  It prevented the cytopathic effect of SARS‐CoV‐1 at low concentrations of 1 μM and halted SARS‐CoV‐1 replication with an EC50 less than 0.1 μM in Vero E6 cells. 188  Gassen et al. demonstrated that niclosamide inhibits SKP2 activity, increases the lysine‐48‐linked polyubiquitination of the Benclin 1 level, boosts autophagy, and effectively impedes MERS‐CoV replication. 239  Niclosamide inhibited MERS‐CoV replication by up to 1000‐fold at 48 h p.i. at 10 μM. 239