The pathogen that causes new coronary pneumonia is a new type of coronavirus, which is closely related to the previously familiar severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV). Infected patients will have fever, fatigue, and dry cough as the main clinical manifestations. In severe cases, acute respiratory distress syndrome will progress rapidly, or even die. So far, no specific drugs and vaccines have been approved for marketing.
After the new type of coronavirus (SARS-CoV-2) invades host cells, it begins to replicate in large numbers. The two processes of transcription and replication of the genetic material RNA genome are the core. The transcription of genetic material will finally be translated into the structural constituent protein of the new virus, and its replication will form the RNA genome of the new virus. RNA-dependent RNA polymerases (RdRp), also known as non-structural protein 12 (nsp12), can be assembled with multiple other non-structural proteins to form an efficient RNA synthesis "machine". As the core component of this transcriptional replication machine, RNA polymerase is one of the most important antiviral drug targets. Disrupting its function is expected to prevent virus replication and ultimately achieve the goal of treatment. The research on the drug targets of the new coronavirus, especially RNA polymerase, is very important for the research and development of such targeted drugs and the verification of the pharmacodynamic mechanism.
The structure of the complex analyzed shows that the RNA polymerase of the new coronavirus has the conservative characteristics of other viral RNA polymerases, and contains the NiRAN (Nidovirus RdRp-associated nucleotidyltransferase) characteristic domain of the Nidovirus; at the same time, viral RNA polymerization enzymes and virus non-structural proteins nsp7 and nsp8 constitute the core unit of transcription and replication machinery. Excitingly, the researchers also discovered for the first time a unique "β hairpin" domain at the N-terminus of the RNA polymerase of the new coronavirus. The discovery of this domain is to clarify the biology of the new coronavirus RNA polymerase. Through in-depth analysis of the atomic resolution structure, the research team discovered the key amino acid residues for the function of the new coronavirus RNA polymerase, and through the "hepatitis C virus polymerase ns5b-Sofosbuvir" effect. The structure of the “molecular” complex was compared, and the possible mode of action of the effector molecules (that is, the final product after metabolism) of remdesivir and fapilavir in inhibiting the new coronavirus RNA polymerase was proposed.
This study is the first to finely describe the internal structure of the transcription and replication machinery of the new coronavirus "RdRp-nsp7-nsp8", and shows how the effector molecules of drug candidates such as Radixivir and fapilavir can precisely target and inhibit viral RNA synthesis. Furthermore, a reasonable mechanism explanation was put forward for exerting pharmacodynamic activity, which laid an important theoretical foundation for the in-depth study of the molecular mechanism of the new coronavirus replication, and opened up a new way for the development of specific drugs against new coronary pneumonia.
In addition, the "Anti-Coronavirus Research Alliance" formed by the research team of Shanghai University of Science and Technology and its collaborators also jointly published the important research results of the new coronavirus on Nature "Structure of Mpro from COVID-19 virus and discovery of its inhibitors" "It is the first to successfully analyze the high-resolution three-dimensional structure of the main protease (Mpro), the key drug target of the new coronavirus, and to use three different drug discovery strategies to find inhibitors against the new coronavirus.
In the research strategy designed from scratch, the "Alliance" found that the Michael receptor N3 is a potent inhibitor of the main protease, and was the first to analyze the 2.1Å high-resolution complex structure of the main protease-N3 (and later Increase to 1.7Å), which is also the world's first three-dimensional structure of the new coronavirus protein to be resolved. In order to facilitate relevant scientific and technological workers to develop antiviral drugs targeting this enzyme as soon as possible, the "Alliance" for the key research issue published the research results for the first time and published the structure in the Protein Data Bank (PDB). Since January 26, the team has directly provided data to the laboratories of more than 300 universities, research institutions and enterprises. This structure was selected as the February Molecule of the Month by PDB protein structure database, and was reported by PDB.
Since then, the "Alliance" has continued to jointly use virtual screening and high-throughput screening strategies to screen more than 10,000 old drugs, clinical drugs, and natural active products, and found several species that have significant inhibitory effects on the main protease. Lead drugs, including disulfiram, carmofur, ebselen, shikonin, Tideglusib and PX-12. Subsequent anti-coronavirus experiments showed that both ebselen and N3 can significantly inhibit the replication of the neocoronavirus at the cellular level. It is worth mentioning that ebselen has been used in clinical trials for the treatment of various diseases such as hearing impairment (completed the second clinical phase), and has a good safety performance. The above-mentioned research results have laid an important foundation for the rapid development of anti-coronary pneumonia drugs with clinical potential.