Filibuvir

Since the outbreak of severe acute respiratory syndrome (SARS) in 2003, the harm caused by coronaviruses to the world cannot be underestimated. Recently, a novel coronavirus (severe acute respiratory syndrome coronavirus‐2 [SARS‐CoV‐2]) initially found to trigger human severe respiratory illness in Wuhan City of China in 2019, has infected more than six million people worldwide by 21 June 2020, and which has been recognized as a public health emergency of international concern as well. And the virus has spread to more than 200 countries around the world. However, the effective drug has not yet been officially licensed or approved to treat SARS‐Cov‐2 and SARS‐Cov infection. NSP12‐NSP7‐NSP8 complex of SARS‐CoV‐2 or SARS‐CoV, essential for viral replication and transcription, is generally regarded as a potential target to fight against the virus. According to the NSP12‐NSP7‐NSP8 complex (PDB ID: 7BW4) structure of SARS‐CoV‐2 and the NSP12‐NSP7‐NSP8 complex (PDB ID: 6NUR) structure of SARS‐CoV, NSP12‐NSP7 interface model, and NSP12‐NSP8 interface model were established for virtual screening in the present study. Eight compounds (Nilotinib, Saquinavir, Tipranavir, Lonafarnib, Tegobuvir, Olysio, Filibuvir, and Cepharanthine) were selected for binding free energy calculations based on virtual screening and docking scores. All eight compounds can combine well with NSP12‐NSP7‐NSP8 in the crystal structure, providing drug candidates for the treatment and prevention of coronavirus disease 2019 and SARS.

Direct acting antivirals (DAAs) provide efficient hepatitis C virus (HCV) therapy and clearance for a majority of patients, but are not available or effective for all patients. They risk developing HCV-induced hepatocellular carcinoma (HCC), for which the mechanism remains obscure and therapy is missing. Annexin A2 (AnxA2) has been reported to co-precipitate with the non-structural (NS) HCV proteins NS5B and NS3/NS4A, indicating a role in HCC tumorigenesis and effect on DAA therapy.

Surface plasmon resonance biosensor technology was used to characterize direct interactions between AnxA2 and HCV NS5B, NS3/NS4 and RNA, and the subsequent effects on catalysis and inhibition.

No direct interaction between AnxA2 and NS3/NS4A was detected, while AnxA2 formed a slowly dissociating, high affinity (K _D = 30 nM), complex with NS5B, decreasing its catalytic activity and affinity for the allosteric inhibitor filibuvir. The RNA binding of the two proteins was independent and AnxA2 and NS5B interacted with different RNAs in ternary complexes of AnxA2:NS5B:RNA, indicating specific preferences.

The complex interplay revealed between NS5B, AnxA2, RNA and filibuvir, suggests that AnxA2 may have an important role for the progression and treatment of HCV infections and the development of HCC, which should be considered also when designing new allosteric inhibitors.