Combinatorial chemistry lead discovery

PURPOSE AND RATIONALE In vitro testing of drug candidates and combinatorial chemistry lead to an increase of lipophilic compounds with poor solubility (Lipinsky). Poor solubility itself may lead to poor oral availability of a potential drug. The growing demand for solubility data in lead phase of drug discovery is answered by a variety of simple solubility assays, which allow the classification of a compound without real quantification (see previous section). One of the easiest way to detect saturation in a solvent is the turbidity of the solution if precipitation occurs. The turbidity caused by precipitation of a poorly soluble compound can be detected by a couple of detection methods (Van de Hulst, Hongve). Lipinsky describes the first methodology, which use UV as detection method and is able to screen hundreds of compounds a day with one instrument. 

In a typical combinatorial chemistry drug-discovery protocol, a large array of compounds, called combinatorial libraries, are produced and tested for high-affinity binding to enzymes, receptors, or antibodies. The compounds that provide a hit with the target are selected and further developed into leads. Further optimization of leads narrows the potential drug candidates to one or... 

A recently introduced NMR-based approach to lead discovery known as SAR by NMR was used in conjunction with combinatorial chemistry to discovery inhibitors that block DNA binding of human papillomavirus E2 protein (Figure 13). SAR by NMR was used to screen for initial ligands for the E2 protein by monitoring changes in the amide... 

Nowadays a broad range of methods is available in the field of chemoinfor-matics. These methods will have a growing impact on drug design. In particular, the discovery of new lead structures and their optimization will profit by virtual saeening [17, 66, 100-103]. The huge amounts of data produced by HTS and combinatorial chemistry enforce the use of database and data mining techniques. 

Murray CW, Clark DE, Auton TR, Firth MA, Li J, Sykes RA, Waszkowycz B, Westhead DR, Young SC. PRO SELECT combining structure-based drug design and combinatorial chemistry for rapid lead discovery. J Comput Aided Mol Des 1997 11 193-207. 

Langer T, Wolber G. Virtual combinatorial chemistry and in silica screening efficient tools for lead structure discovery Pure Appl Chem 2004 76 991-6. 

Combinatorial chemistry and parallel synthesis are now the dominant methods of compound synthesis at the lead discovery stage [2]. The method of chemistry synthesis is important because it dictates compound physical form and therefore compound aqueous solubility. As the volume of chemistry synthetic output increases due to combinatorial chemistry and parallel synthesis, there is an increasing probability that resultant chemistry physical form will be amorphous or a neat material of indeterminate solid appearance. There are two major styles of combinatorial chemistry - solid-phase and solution-phase synthesis. There is some uncertainty as to the true relative contribution of each method to chemistry output in the pharmaceutical/biotechnology industry. Published reviews of combinatorial library synthesis suggest that solid-phase synthesis is currently the dominant style contributing to about 80% of combinatorial libraries [3]. In solid-phase synthesis the mode of synthesis dictates that relatively small quantitities of compounds are made. 

Medicinal chemistry makes use of solid phase combinatorial chemistry as a (rapidly maturing) tool for lead discovery and optimization. Metathesis reactions are obviously useful in this context [45] as they can be used ... 

One of the driving forces to apply combinatorial chemistry in drug discovery is to accelerate lead discovery and preclinical research in order to find the next drug. It is important that these combinatorial library compounds are as pure as possible when performing lead discovery screening. At this stage,... 

The identification of compounds with a desired property is a central pursuit in science. In the field of drug discovery combinatorial chemistry has played an increasingly important role for identification and optimization of drug leads which target therapeutically important biomolecules. For the successful implementation of combinatorial methods, new and innovative synthesis methods have been developed. Additionally, novel conceptual approaches to the design of compounds have been pursued to more efficiently generate libraries of small molecules. 

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