Recent advances in developing small-molecule inhibitors against SARS-CoV-2

The COVID-19 pandemic caused by the novel SARS-CoV-2 virus has caused havoc across the entire world.Even though several COVID-19 vaccines are currently in distribution worldwide,with others in the pipeline,treatment modalities lag behind.Accordingly,researchers have been working hard to understand the nature of the virus,its mutant strains,and the pathogenesis of the disease in order to uncover possible drug targets and effective therapeutic agents.As the research continues,we now know the genome structure,epidemiological and clinical features,and pathogenic mechanism of SARS-CoV-2.Here,we summarized the potential therapeutic targets involved in the life cycle of the virus.On the basis of these targets,small-molecule prophylactic and therapeutic agents have been or are being developed for prevention and treatment of SARS-CoV-2 infection.

A pan-coronavirus peptide inhibitor prevents SARS-CoV-2 infection in mice by intranasal delivery

Coronaviruses(Co Vs)have brought serious threats to humans,particularly severe acute respiratory syndrome coronavirus 2(SARS-Co V-2),which continually evolves into multiple variants.These variants,especially Omicron,reportedly escape therapeutic antibodies and vaccines,indicating an urgent need for new antivirals with pan-SARS-Co V-2 inhibitory activity.We previously reported that a peptide fusion inhibitor,P3,targeting heptad repeated-1(HR1)of SARS-Co V-2 spike(S)protein,could inhibit viral infections.Here,we further designed multiple derivatives of the P3 based on structural analysis and found that one derivative,the P315V3,showed the most efficient antiviral activity against SARS-Co V-2 variants and several other sarbecoviruses,as well as other human-Co Vs(HCo Vs).P315V3 also exhibited effective prophylactic efficacy against the SARS-Co V-2 Delta and Omicron variants in mice via intranasal administration.These results suggest that P315V3,which is in PhaseⅡclinical trial,is promising for further development as a nasal pan-SARS-Co V-2 or pan-Co Vs inhibitor to prevent or treat CoV diseases.

HR121 targeting HR2 domain in S2 subunit of spike protein can serve as a broad-spectrum SARS-CoV-2 inhibitor via intranasal administration

The continuously emerging SARS-CoV-2 variants pose a great challenge to the efficacy of current drugs,this necessitates the development of broad-spectrum antiviral drugs.In the previous study,we designed a recombinant protein,heptad repeat(HR)121,as a variant-proof vaccine.Here,we found it can act as a fusion inhibitor and demonstrated broadly neutralizing activities against SARS-CoV-2 and its main variants.Structure analysis suggested that HR121 targets the HR2 domain in SARS-CoV-2 spike(S)2 subunit to block virus-cell fusion.Functional experiments demonstrated that HR121 can bind HR2 at serological-pH and endosomal-pH,highlighting its inhibition capacity when SARS-CoV-2 enters via either cellular membrane fusion or endosomal route.Importantly,HR121 can effectively inhibit SARS-CoV-2 and Omicron variant pseudoviruses entering the cells,as well as block authentic SARSCoV-2 and Omicron BA.2 replications in human pulmonary alveolar epithelial cells.After intranasal administration to Syrian golden hamsters,it can protect hamsters from SARS-CoV-2 and Omicron BA.2 infection.Together,our results suggest that HR121 is a potent drug candidate with broadly neutralizing activities against SARS-CoV-2 and its variants.

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.