Comparative study of the unbinding process of some HTLV-1 protease inhibitors using Unbiased Molecular Dynamics simulation

The HTLV-1 protease is one of the major antiviral targets to overwhelm this virus. Several research groups have been developing protease inhibitors over the years, but none has been successful. In this regard, the development of new HTLV-1 protease inhibitors based on fixing the defects of previous inhibitors will overcome the absence of curative treatment for this oncovirus. Thus, we decided to study the unbinding pathways of the most potent (compound 10, Ki = 15 nM) and one of the weakest (compound 9, Ki = 7900 nM) protease inhibitors, which are very structurally similar, with the PDB IDs: 4YDG, 4YDF, using the Supervised Molecular Dynamics (SuMD) method. In this project, we had various short and long-time-scale simulations, that in total, we could have 12 successful unbindings (a total of 14.8 s) for the two compounds in both mp forms. This comparative study measured all the essential factors simultaneously in two different inhibitors, which improved our results. This study revealed that Asp32 or Asp32' in the two forms of mp state similarly exert super power effects on maintaining both potent and weak inhibitors in the binding pocket of HTLV-1 protease. In parallel with the important impact of these two residues, in the potent inhibitors unbinding process, His66' was a great supporter, that was absent in the weak inhibitors unbinding pathway. In contrast, in the weak inhibitors unbinding process, Trp98/Trp98' by pi-pi stacking interactions were unfavorable for the stability of the inhibitor in the binding site. In our opinion, these results will assist in designing more potent and effective inhibitors for the HTLV-1 protease.