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October 04, 2007

Structure-based Drug Design

Structurally-informed approaches have increasingly demonstrated their value in drug design since the first biologically-relevant X-ray structures became available 30 years ago. The impact of these methods and technologies on early lead discovery and lead optimization is significant. Issues that are of current relevance include:

- Are we maximizing the use of (the never-ending, increasing) current computer power in Structure-based Drug Design (SBDD)?
- Virtual Screening (VS) is usually applied to enrich datasets with high-activity compounds. The "unusual" application of VS to weaker kinase binders is an interesting area of exploration.
- Cross-docking applied to a structurally-rich CDK2 dataset can shed some light on the pros and cons of utilizing docking methods during lead optimization.
- What is the function of modeling water molecules in SBDD? Instead of ignoring (or deleting) them, their influence on binding affinity should be considered.
- What do we know, what do we we think we know or simply don’t know about SBDD?

On 17 October 2007 we will hold an eCheminfo Community of Practice conference session at Bryn Mawr College, Philadelphia to discuss latest advances in SBDD. The session will be chaired by Jose Duca (Schering-Plough) and includes a knowledgeable panel of speakers and discussion leaders: Daniel Cheney (Bristol-Myers Squibb), Natasja Brooijmans (Wyeth), Jose Duca (Schering-Plough), Terry Stouch (JCAMD) and Julian Tirado-Rives (Yale). A description of the session with presentation abstracts follows:

Structure-based Drug Design
http://echeminfo.com/COMTY_conferencesprog07sbdd

(Please follow continuation to read abstracts)

Abstracts

Taking advantage of current computational capacities: Applications of high-resolution techniques in computer-assisted drug design
Daniel L. Cheney, Department of Molecular Biosciences, Bristol-Myers Squibb, Hopewell, New Jersey

Current computational resources have grown enormously over recent years, to the extent that modern gaming PC’s easily surpass on a per-processor basis the performance of supercomputers of a decade ago. The emergence of Linux clusters, office-PC grids, and cheap storage and memory is challenging the modeling community to integrate into the drug design process higher resolution methodologies which were until recently beyond our resources. In this presentation, the utilization of relatively rigorous techniques in the context of routine molecular modeling will be discussed. Applications involving real world problems in drug discovery will also be described

Realistic Virtual Screening Assessment in Kinases
Natasja Brooijmans, Wyeth

Most retrospective receptor-based virtual screening studies in the literature enrich libraries with highly-active compounds against the studied targets. While these studies show that docking can be used successfully to distinguish active ligands among decoys, these are not very realistic. In industrial settings, corporate and commercial collections are screened that contain very few optimized compounds that inhibit the target of interest in the nanomolar range. Leads identified by high-throughput screening and virtual screening are generally in the low-to-medium micromolar range. Using Glide SP docking, we have performed studies on a set of kinase targets that show that identifying these weak leads is significantly more difficult than identifying highly-optimized ligands. Enrichment Factors obtained with Glide4.0 and 4.5 will be compared. Finally, the use of pre- and post-docking filters to enhance Enrichment Factors was investigated.

Cross-docking vs. Scoring: Is Overfitting the Third Wheel?
José Duca, Schering-Plough Research Institute

Addressing protein flexibility has been a shortcoming of many methods. In this study, we used cross-docking of ~150 inhibitors into the full set of crystal structures for each inhibitor complexed with the kinase CDK2. In scoring relative binding potency based on multiple combinations of several target proteins, the dangers of over-fitting became apparent. Examples will be given of insights gained into ligand properties such as pKa values and relative tautomeric stabilities computed via ab initio quantum mechanical methods.

Ligand/protein binding in Structure-Based Drug Design: Examples of the role of water and caveats in its treatment
Terry R. Stouch, Editor-in-Chief of the Journal of Computer-Aided Molecular Design

The importance of the role of solvation in drug binding is often alluded to and explicit roles of individual water molecules have been recognized in some drug-protein complexes. However, the energetics and extent of water's importance has not been clearly defined and water molecules are not always seen by experiment and can be mistaken for other things. We will present clear examples of complexes where water plays active and passives roles in drug-protein binding and sometimes a major role. Computational analysis will be described that helps to understand the extent, impact, and energetics of water's effects with comparison to some more commonly used methods to describe solvation.

Ideas, Approaches and Progress in Structure-Based Drug Design
Julian Tirado-Rives, Yale University, Department of Chemistry

The process of going from a known structure of a pharmaceutical target to an active compound may seem both conceptually simple and practically daunting. This talk will expand on our current thoughts and ideas on the overall process, the computational approaches we utilize and are currently exploring, some of the progress achieved and future directions. Emphasis will be placed on the development of non-nucleoside inhibitors for HIV-1 reverse transcriptase using Free Energy Perturbation, de novo ligand design, and virtual screening of available libraries. Some relevant references are: Jorgensen, W. L.; Ruiz-Caro, J.; Tirado-Rives, J.; Basavapathruni, A.; Anderson, K. S.; Hamilton, A. D. “Computer-aided design of non-nucleoside inhibitors of HIV-1 reverse transcriptase.” Bioorg. Med. Chem. 2006, 16, 663-667. Tirado-Rives, J.; Jorgensen, W. L. “Contribution of Conformer Focusing on the Uncertainty in Predicting Free Energies for Protein-Ligand Binding.”
J. Med. Chem. 2006, 49, 5880-5884.

Barry Hardy
eCheminfo Community of Practice

Footnote:
Campus Map for direction guidance on arrival:
Download campus_mapnd.pdf

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