A highly potent and stable pan-coronavirus fusion inhibitor as a candidate prophylactic and therapeutic for COVID-19 and other coronavirus diseases

The development of broad-spectrum antivirals against human coronaviruses(HCoVs)is critical to combat the current coronavirus disease 2019(COVID-19)pandemic caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)and its variants,as well as future outbreaks of emerging CoVs.We have previously identified a polyethylene glycol-conjugated(PEGylated)lipopeptide,EK1C4,with potent pan-CoV fusion inhibitory activity.However,PEG linkers in peptide or protein drugs may reduce stability or induce anti-PEG antibodies in vivo.Therefore,we herein report the design and synthesis of a series of dePEGylated lipopeptide-based pan-CoV fusion inhibitors featuring the replacement of the PEG linker with amino acids in the heptad repeat 2 C-terminal fragment(HR2-CF)of HCoV-OC43.Among these lipopeptides,EKL1C showed the most potent inhibitory activity against infection by SARS-CoV-2 and its spike(S)mutants,as well as other HCoVs and some bat SARS-related coronaviruses(SARSr-CoVs)tested.The dePEGylated lipopeptide EKL1C exhibited significantly stronger resistance to proteolytic enzymes,better metabolic stability in mouse serum,higher thermostability than the PEGylated lipopeptide EK1C4,suggesting that EKL1C could be further developed as a candidate prophylactic and therapeutic for COVID-19 and other coronavirus diseases.