Ultrapotent SARS-CoV-2 neutralizing antibodies effectively block new-emerging mutational variants (preprint)

Accumulating mutations on SARS-CoV-2 Spike (S) protein may increase the possibility of immune escape, challenging the present COVID-19 prophylaxis and clinical interventions. Here, in a panel of receptor binding domain (S-RBD) specific monoclonal antibodies (mAbs) with high neutralizing potency against authentic SARS-CoV-2, at least 6 of them were found to efficiently block the pseudovirus of 501Y.V2, a highly transmissible SARS-CoV-2 variant with escape mutations. The top 3 neutralizing Abs (13G9, 58G6 and 510A5) exhibited comparative ultrapotency as those being actively pursued for clinical development. Interestingly, the antigenic sites for the majority of our neutralizing Abs overlapped with a single epitope (13G9e) on S-RBD. Further, the 3-dimensional structures of 2 ultrapotent neutralizing Abs 13G9 or 58G6 in complex with SARS-CoV-2 S trimer demonstrated that both Abs bound to a steric region within S472–490. Moreover, a specific linear region (S450–457) was identified as an additional target for 58G6. Importantly, our cryo-electron microscopy (cryo-EM) analysis revealed a unique phenomenon that the S-RBDs interacting with the fragments of antigen binding (Fabs) of 13G9 or 58G6 encoded by the IGHV1-58 and the IGKV3-20 gene segments were universally in the ‘up’ conformation in all observed particles. The potent neutralizing Abs presented in the current study may be promising candidates to fulfill the urgent needs for the current pandemic of SARS-CoV-2, and may of fundamental value for the next-generation vaccine development.

Structure-Based Design, Synthesis and Biological Evaluation of Peptidomimetic Aldehydes as a Novel Series of Antiviral Drug Candidates Targeting the SARS-CoV-2 Main Protease (preprint)

SARS-CoV-2 is the etiological agent responsible for the COVID-19 outbreak in Wuhan. Specific antiviral drug are urgently needed to treat COVID-19 infections. The main protease (Mpro) of SARS-CoV-2 is a key CoV enzyme that plays a pivotal role in mediating viral replication and transcription, which makes it an attractive drug target. In an effort to rapidly discover lead compounds targeting Mpro, two compounds (11a and 11b) were designed and synthesized, both of which exhibited excellent inhibitory activity with an IC50 value of 0.05 M and 0.04 M respectively. Significantly, both compounds exhibited potent anti-SARS-CoV-2 infection activity in a cell-based assay with an EC50 value of 0.42 M and 0.33 M, respectively. The X-ray crystal structures of SARS-CoV-2 Mpro in complex with 11a and 11b were determined at 1.5 [A] resolution, respectively. The crystal structures showed that 11a and 11b are covalent inhibitors, the aldehyde groups of which are bound covalently to Cys145 of Mpro. Both compounds showed good PK properties in vivo, and 11a also exhibited low toxicity which is promising drug leads with clinical potential that merits further studies.

Structure of RNA-dependent RNA polymerase from 2019-nCoV, a major antiviral drug target (preprint)

A novel coronavirus (2019-nCoV) outbreak has caused a global pandemic resulting in tens of thousands of infections and thousands of deaths worldwide. The RNA-dependent RNA polymerase (RdRp, also named nsp12), which catalyzes the synthesis of viral RNA, is a key component of coronaviral replication/transcription machinery and appears to be a primary target for the antiviral drug, remdesivir. Here we report the cryo-EM structure of 2019-nCoV full-length nsp12 in complex with cofactors nsp7 and nsp8 at a resolution of 2.9-[A]. Additional to the conserved architecture of the polymerase core of the viral polymerase family and a nidovirus RdRp-associated nucleotidyltransferase (NiRAN) domain featured in coronaviral RdRp, nsp12 possesses a newly identified {beta}-hairpin domain at its N-terminal. Key residues for viral replication and transcription are observed. A comparative analysis to show how remdesivir binds to this polymerase is also provided. This structure provides insight into the central component of coronaviral replication/transcription machinery and sheds light on the design of new antiviral therapeutics targeting viral RdRp. One Sentence SummaryStructure of 2019-nCov RNA polymerase.

Structure-based drug design, virtual screening and high-throughput screening rapidly identify antiviral leads targeting COVID-19 (preprint)

A new coronavirus (CoV) identified as COVID-19 virus is the etiological agent responsible for the 2019-2020 viral pneumonia outbreak that commenced in Wuhan1-4. Currently there is no targeted therapeutics and effective treatment options remain very limited. In order to rapidly discover lead compounds for clinical use, we initiated a program of combined structure-assisted drug design, virtual drug screening and high-throughput screening to identify new drug leads that target the COVID-19 virus main protease (Mpro). Mpro is a key CoV enzyme, which plays a pivotal role in mediating viral replication and transcription, making it an attractive drug target for this virus5,6. Here, we identified a mechanism-based inhibitor, N3, by computer-aided drug design and subsequently determined the crystal structure of COVID-19 virus Mpro in complex with this compound. Next, through a combination of structure-based virtual and high-throughput screening, we assayed over 10,000 compounds including approved drugs, drug candidates in clinical trials, and other pharmacologically active compounds as inhibitors of Mpro. Six of these inhibit Mpro with IC50 values ranging from 0.67 to 21.4 M. Ebselen also exhibited promising antiviral activity in cell-based assays. Our results demonstrate the efficacy of this screening strategy, which can lead to the rapid discovery of drug leads with clinical potential in response to new infectious diseases where no specific drugs or vaccines are available.