A pan-coronavirus fusion inhibitor targeting the HR1 domain of human coronavirus spike

Xia, Shuai; Yan, Lei; Xu, Wei; Agrawal, Anurodh Shankar; Algaissi, Abdullah; Tseng, Chien-Te K.; Wang, Qian; Du, Lanying; Tan, Wenjie; Wilson, Ian A.; Jiang, Shibo; Yang, Bei; Lu, Lu

In our previous studies, we found that the MERS-CoV-specific fusion inhibitor MERS-HR2P could not block SARS-CoV pseudovirus infection and did not display any broad-spectrum inhibitory activity. Thus, it was unclear whether 6-HB was a good target site for the development of a broad-spectrum anti-HCoV inhibitor. To identify a pan-HCoV fusion inhibition target site and preferably also to develop a potential pan-HCoV inhibitor against infection of multiple HCoVs in the human respiratory tract, we successfully established multiple HCoV S-mediated cell-cell fusion assays to determine the cross-inhibitory spectrum between HR1Ps and HR2Ps, which are derived from the HR1 and HR2, respectively, of HCoVs. Unexpectedly, we found that OC43-HR2P harbored broad-spectrum binding activity to all HR1Ps and manifested fusion inhibitory activity against all HCoV S-mediated cell-cell fusion. We then further optimized the OC43-HR2P to improve its antiviral activity and solubility. The optimized peptide EK1 exhibited broad and potent fusion inhibitory activity against infection by HCoVs and SL-CoVs on various in vitro models, i.e., cell-cell fusion assays and pseudotyped or live viral infection assays. We assessed the prophylactic and protective effects of EK1 through intranasal administration on OC43 and MERS-CoV mouse models. EK1 exhibited effective preventive and protective effects in these mouse models with an acceptable in vivo safety profile. Furthermore, the in vivo pharmacokinetic profiling and safety studies helped us acquire useful data for potential human clinical trials in the future.