**4.1 Virus attachment and entry**

The trimeric *SARS-CoV-2* spike glycoprotein has a crucial role in the virus attachment and entry. The glycoprotein constituent monomer comprises two subunits, S1 and S2. The S1 encompasses the N-terminal domain (NTD) and the RBD, which is accountable for interacting with ACE2. Therefore, RDB is considered an effective drug target for discovering therapeutic agents such as neutralizing antibodies [18]. In **Table 2**, some anti-RBD antibodies are listed. The results of some studies demonstrated potent therapeutic and prophylactic abilities of anti-RDB antibodies in cell culture or animal model systems. In this regard, Gao et al. demonstrated that a potent COVID-19 antibody, BD-368-2 has significant prophylactic effectiveness in *SARS-CoV-2*-infected hACE2 mice at a dose of 20 mg/kg [24]. Similarly, another study confirmed both prophylactic and treatment activities of CB6 antibody in a dose of 50 mg/kg [25]. The ability of COV2-2130 to reduce the viral burden and levels of inflammation has also been approved [26]. Furthermore, besides the introduced antibodies, several small molecules such as salvianolic acid, arbidol, dri-c23041, cepharanthine, abemaciclib, osimertinib, trimipramine, colforsin, ingenol, and clofazimine have also been considered for in vitro evaluation of their *SARS-CoV-2* entry inhibition activities [27].
