Dear Editor,rnSince December 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a pneumonia outbreak in Wuhan city, China, followed by global spread [1, 2].As of 9 April, 2020, millions of confirmed cases of SARS-CoV-2 infection have been reported, and the global death toll of SARS-CoV-2 infection has surged to tens of thousands of victims, making it a public health emergency of international concern (PHEIC).However, no specific antiviral drug or vaccine for SARS-CoV-2 treatment exists.The high infectivity and the increasing fatality of SARS-CoV-2 highlight the demand for drug discovery.SARS-CoV-2 is closely related to severe acute respiratory syndrome coronavirus (SARS-CoV) [2].Full-genome sequencing analysis indicated that SARSCoV-2 shares a high-sequence identity with SARS-CoV [3].The spike protein (S-protein) of coronaviruses interacts with cell receptors to mediate viral entry into target cells [4].Additional evidence suggests that both SARS-CoV and SARS-CoV-2 employ angiotensin-converting enzyme 2 (ACE2) as the entry receptor and that the receptor-binding domain (RBD) of the S-protein directly binds to ACE2, triggering endocytosis of virus particles [5-7].A recent study suggested that the binding affinity between ACE2 and the RBD of SARS-CoV-2 is 10-20 times stronger than that with the RBD of SARS-CoV [5], which likely explains the increased infectivity of SARS-CoV-2.