Allosteric inhibitors of the NS3 protease from the hepatitis C virus.
The nonstructural protein 3 (NS3) from the hepatitis C virus processes the non-structural region of the viral precursor polyprotein in infected hepatic cells. The NS3 protease activity has been considered a target for drug development since its identification two decades ago. Although specific inhibitors have been approved for clinical therapy very recently, resistance-associated mutations have already been reported for those drugs, compromising their long-term efficacy. Therefore, there is an urgent need for new anti-HCV agents with low susceptibility to resistance-associated mutations. Regarding NS3 protease, two strategies have been followed: competitive inhibitors blocking the active site and allosteric inhibitors blocking the binding of the accessory viral protein NS4A. In this work we exploit the intrinsic Zn(+2)-regulated plasticity of the protease to identify a new type of allosteric inhibitors. In the absence of Zn(+2), the NS3 protease adopts a partially-folded inactive conformation. We found ligands binding to the Zn(+2)-free NS3 protease, trap the inactive protein, and block the viral life cycle. The efficacy of these compounds has been confirmed in replicon cell assays. Importantly, direct calorimetric assays reveal a low impact of known resistance-associated mutations, and enzymatic assays provide a direct evidence of their inhibitory activity. They constitute new low molecular-weight scaffolds for further optimization and provide several advantages: 1) new inhibition mechanism simultaneously blocking substrate and cofactor interactions in a non-competitive fashion, appropriate for combination therapy; 2) low impact of known resistance-associated mutations; 3) inhibition of NS4A binding, thus blocking its several effects on NS3 protease.
Institute of Biocomputation and Physics of Complex Systems (BIFI), Joint Unit IQFR-CSIC-BIFI, Universidad de Zaragoza, Zaragoza, Spain.
Olga
O
Abian
Sonia
S
Vega
Javier
J
Sancho
Adrian
A
Velazquez-Campoy
D000494:Allosteric Regulation / Q000187:drug effects; D000998:Antiviral Agents / Q000737:chemistry / Q000494:pharmacology*; D002460:Cell Line; D004353:Drug Evaluation, Preclinical; D024882:Drug Resistance, Viral / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D016174:Hepacivirus / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D011480:Protease Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D011485:Protein Binding; D017361:Viral Nonstructural Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry; D014779:Virus Replication / Q000187:drug effects; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases
D000998:Antiviral Agents; D008024:Ligands; D011480:Protease Inhibitors; D017361:Viral Nonstructural Proteins; C084422:NS3 protein, hepatitis C virus; D012697:Serine Endopeptidases; D043583:Nucleoside-Triphosphatase; D053487:DEAD-box RNA Helicases; D000085242:Viral Proteases