Xu et al. 49  identified two small molecules, TGG (2; Figure 4) and luteolin (3; Figure 4), that can bind avidly to the SARS‐CoV‐1 S2 protein and inhibit its entry into Vero E6 cells (EC50: 4.5 µM, 10.6 µM; respectively). Compounds 2 and 3 showed cytotoxicity (CC50) of 1.08 and 0.155 mM, and the selectivity index (SI) values of 2 and 3 were 240.0 and 14.62, respectively. Further studies regarding acute toxicity revealed that the 50% lethal doses of 2 and 3 were ~456 and 232 mg/kg, respectively. These results indicate that these small molecules could be used at relatively high concentrations in mice. 49  Quercetin (4; Figure 4), an analog of 3, also showed antiviral activity against SARS‐CoV‐1, with an EC50 value of 83.4 µM and a CC50 value of 3.32 mM. 50