Structural basis of SARS-CoV-2 main protease inhibition by a broad-spectrum anti-coronaviral drug.
Wang, Y.C., Yang, W.H., Yang, C.S., Hou, M.H., Tsai, C.L., Chou, Y.Z., Hung, M.C., Chen, Y.(2020) Am J Cancer Res 10: 2535-2545
- PubMed: 32905393 
- Primary Citation of Related Structures:  
7CAM, 7CB7 - PubMed Abstract: 
The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or 2019 novel coronavirus (2019-nCoV), took tens of thousands of lives and caused tremendous economic losses. The main protease (M pro ) of SARS-CoV-2 is a potential target for treatment of COVID-19 due to its critical role in maturation of viral proteins and subsequent viral replication. Conceptually and technically, targeting therapy against M pro is similar to target therapy to treat cancer. Previous studies show that GC376, a broad-spectrum dipeptidyl M pro inhibitor, efficiently blocks the proliferation of many animal and human coronaviruses including SARS-CoV, Middle East respiratory syndrome coronavirus (MERS-CoV), porcine epidemic diarrhea virus (PEDV), and feline infectious peritonitis virus (FIPV). Due to the conservation of structure and catalytic mechanism of coronavirus main protease, repurposition of GC376 against SARS-CoV-2 may be an effective way for the treatment of COVID-19 in humans. To validate this conjecture, the binding affinity and IC 50 value of M pro with GC376 was determined by isothermal titration calorimetry (ITC) and fluorescence resonance energy transfer (FRET) assay, respectively. The results showed that GC376 binds to SARS-CoV-2 M pro tightly (K D = 1.6 μM) and efficiently inhibit its proteolytic activity (IC 50 = 0.89 μM). We also elucidate the high-resolution structure of dimeric SARS-CoV-2 M pro in complex with GC376. The cocrystal structure showed that GC376 and the catalytic Cys145 of M pro covalently linked through forming a hemithioacetal group and releasing a sulfonic acid group. Because GC376 is already known as a broad-spectrum antiviral medication and successfully used in animal, it will be a suitable candidate for anti-COVID-19 treatment.
Organizational Affiliation: 
Institute of New Drug Development, China Medical University Taichung 40402, Taiwan.