Sialidase as a target for inhibitors of influenza virus replication

Strategies for Antiviral Drug Discovery

The need for antiviral drugs is growing rapidly as more viral diseases are recognized. The methods used to discover these drugs have evolved considerably over the past 40 years and the overall process of discovery can be broken down into sub-processes which include lead generation, lead optimization and lead development. Various methods are now employed to ensure these processes are carried out efficiently. For lead generation, screening methodologies have developed to the extent where hundreds of thousands of compounds can be screened against a particular target. An alternative approach is to use the structures of enzyme substrates as a starting point for drug discovery. Much use is now made of X-ray crystallographic data of target–inhibitor complexes for the optimization of lead structures, and methods for preparing libraries of compounds to assist both generation and optimization of leads are welldeveloped. The methods used to predict and improve the pharmacokinetic properties of compounds are also changing rapidly. Finally, novel approaches to antiviral therapy using oligonucleotide-based compounds or modulating the host immune response are also being explored. This review discusses these approaches, provides examples of where their application has been successful and sets them against a historical background.

Combining docking, scoring and molecular field analyses to probe influenza neuraminidase-ligand interactions

In this project, several docking conditions, scoring functions and corresponding protein-aligned molecular field analysis (CoMFA) models were evaluated for a diverse set of neuraminidase (NA) inhibitors. To this end, a group of inhibitors were docked into the active site of NA. The docked structures were utilized to construct a corresponding protein-aligned CoMFA models by employing probe-based (H+, OH, CH3) energy grids and genetic partial least squares (G/PLS) statistical analysis. A total of 16 different docking configurations were evaluated, of which some succeeded in producing self-consistent and predictive CoMFA models. However, the best model coincided with docking the ionized ligands into the hydrated form of the binding site via PLP1 scoring function (r2LOO=0.735, r2PRESS against 24 test compounds=0.828). The highest-ranking CoMFA models were employed to probe NA-ligand interactions. Further validation by comparison with a co-crystallized ligand-NA crystallographic structure was performed. This combination of docking/scoring/CoMFA modeling provided interesting insights into the binding of different NA inhibitors.

Recent advances in clinical trials of the direct and indirect selective Factor Xa inhibitors

Over the years, pharmacological intervention to prevent undesired intravascular coagulation and the associated detrimental effects has been a clinical challenge. The first generation of anticoagulant agents, warfarin and unfractionated heparin (UFH), involve indirect mechanisms of inhibiting the coagulation cascade. Fractionated, or low-molecular weight, heparins (LMWHs) are more selective for coagulation Factor Xa (FXa) over thrombin (FIIa). LMWHs also utilise an indirect mechanism of inhibition and have improved pharmacokinetic, pharmacodynamic and therapeutic profiles over UFH. The success of LMWHs, along with the pivotal location of FXa in the coagulation cascade, has prompted interest in the discovery and development of selective FXa inhibitors. There are two general classes of FXa inhibitors in development, of which SR90107A/ORG31540, an antithrombin-III-dependent pentasaccharide and DX-9065a, a small molecule direct FXa inhibitor, have published clinical data. SR90107A/ORG31540 and DX-9065a offer safe, predictable pharmacokinetic and pharmacodynamic profiles when administered subcutaneously and intravenously, respectively, to healthy volunteers and appear to be progressing through clinical development. The purpose of this review is to compile and summarise the published Phase I and II clinical data for SR90107A/ORG31540 and DX-9065a.

Synthesis of a tetrasubstituted bicyclo [2.2.2] octane as a potential inhibitor of influenza virus sialidase

A novel synthesis of the bicyclo [2.2.2] octane ring system has been achieved utilising a tandem Henry cyclisation as the key stage. This chemistry has been employed in the synthesis of a potential inhibitor of influenza virus sialidase.

Sialidase inhibitors related to zanamivir: synthesis and biological evaluation of 4H-pyran 6-ether and ketone

Synthesis of 5R-Acetamido-4S-amino-4H-pyran-6R-O-( -ethyl)propyl and 6R-(1-oxo-2-ethyl)butyl 2-carboxylic acids (4 and 5) and their evaluation as inhibitors of influenza virus sialidase is described. Both compounds showed good inhibitory activity with marked selectivity for influenza A sialidase.