Hello again to the members of World Community Grid. With this update, we announce that we are ready to call our projects completed. We thank World Community Grid, its member volunteers, and their computers for their help.

The major advanced from this project are as follows:

1) All calculations necessary to fully evaluate Phase 1 and Phase 2 of “Discovering Dengue Drugs – Together” have been completed. We are moving this project to a “completed” status and are assembling our results for posting on our web site. At this point, our calculations, which have used a combination of World Community Grid distributed computers and supercomputers from the Texas Advanced Computer Center (TACC; Austin, TX), have identified several new dengue protease inhibitors. These inhibitors have been validated in our laboratories using rigorous biochemical and cell culture assays. Most of these lead compounds inhibited both dengue and West Nile virus proteases. A handful of analogs developed from our initial computer-discovered dengue leads have entered crucial pre-clinical pharmacokinetic and efficacy studies. Thus, our World Community Grid project has been invaluable in helping identify dengue and West Nile protease inhibitors. We will be working over the next several years to turn these inhibitors into small molecules with properties suitable for human clinical trials.

2) Phase 2 of our project combined the computer resources of World Community Grid and TACC to provide unparalleled computing power to calculate the free energies of binding for several diverse proteins and a large number of potential ligands. We hypothesized that these extensive molecular dynamics calculations would provide statistical mechanical conformational ensembles from which we could accurately calculate free energies of binding. This was developed as a robust method to identify false-positive hits and more accurately discriminate between inhibitors and non-inhibitors. Unfortunately, calculations of the free energy of binding for a number of different protein:ligand systems did not match experimental measurements. Moreover, as we tested greater numbers of systems (facilitated by the combined computer resources of World Community Grid and TACC), we observed that an unacceptably large number of free energy calculations incorrectly predicted that known non-inhibitors would bind to a protein target. Thus, we conclude that the current state of free energy of binding calculations are not yet able to discriminate between binders and non-binders for every protein system However, as we reported earlier, there are some systems (e.g., lysozyme) where the free energy of binding calculations provided excellent discrimination between binders and non-binders. This work has shown that our current Phase 2 calculations are valuable at discriminating between true and false-positive hits for some target proteins, but not for all systems. We will continue our efforts to develop robust free energy of binding calculations that can be applied to a larger set of target proteins. This basic research project will not require the massive computing resources of World Community Grid at this time.

As always, we appreciate the time, effort, and dedication of World Community Grid members. The advances we are making in better understanding drug discovery software and its current limitations could not have been made without your efforts and your computer cycles.

Sincerely,
Stan