High-throughput-screening

High-throughput screening is the description of an airay of technologies to speed up the testing of compounds from various sources (natural or synthetic) for their parameters such as effects with specified test systems and ADME. 

The concept is also being applied for the previous stage in the process, i.e. the attempts to discover novel gene targets by, for example, differential display. 

Assay Detection instrument Throughput data points per week Gating method Advantages Disadvantages 

Electro- physiology Patch-clamp rig 150 Voltage/cunent command protocols Gold standard assay, high infoimation content Low-throughput not easily amenable to automation 

Aurora-FRET-based membrane-potential assay VIPR 96-well (20000) Toxin to activate channel or delay inactivation High-through-put functional readout, rapid reporter of changes in membrane potential, amenable to automation, Ratio-metiic Proprietary technology available through corporate alliance 

The aim of this section is to give an overview of the most common screening methods used in the hit generation phase. For a detailed description, the reader is directed to Lead Generation Approaches in Drug Discovery [5]. 

The assay developed for the HTS will also define the HTS quality [8]. There are two types of assays. The first one is the biochemical assay, a cell-fi ee assay. 

In this assay, the cell is broken down to its molecular machinery by ultracentrifugation or other separation techniques so that a specific process can be studied in the absence of other potentially interfering cellular components [9]. 

The other is the cell-based assay wherein the experiment uses five cells. Thus, this assay is physiologically more relevant and data obtained provides a richer picture of the test compound s function in the cellular machinery. One drawback of this assay is directly linked to the use of five cells as it requires special considerations. Hence, most often the throughput of the cell-based assay is lower than the biochemical assay throughput. The intrinsic molecular properties of the test compounds (e.g., permeabihty) can also be at play here adding an extra level of complexity to the data analysis. 

The type of information required by the project team and target itself will set the choice of the HTS assay type. The quality of the HTS outcome is directly linked to the assay format It is thus easy to conceive that the project team must define precisely their expectation for each target and not always treat targets belonging to the same class in a similar fashion. 

Advanced discovery of new electrocatalyst formulations is increasingly dominated by two techniques high-throughput screening of both model and practical catalyst materials and computational approaches to identify new active surfaces through theory. 

Scanning electron micrographs, at different magnifications, of a 3M Company Pt-coated thin film catalyst. (Reprinted from M. K. Debe et al.. Journal of Power Sources, 161, 1002. Copyright 2006, with permission from Elsevier.) 

Interestingly, reverse designing has come into being by virtue of the introduction of two extremely important seientifie diseoveries, namely (a) High Throughput Screening, and b) Combinatorial Chemistry. 

Baum and Borman (1996) postulated that combinatorial chemistry refers to a particular sophisticated method of minimizing the effective cost of drug discovery whereby the following three cardinal objectives may be accomplished with utmost satisfaction and fruitful results, namely  

Salient Features The various salient features of combinatorial chemistry are as enumerated 

In a rather broader perspective towards the ever increasing and eternal (never-ending) search for newer drug molecules i.e., chemical entities that essentially requires specific and noteworthy biological characterstic feature do require two kinds of approaches, for instance  

Rational designing usually encounters the following three obstacles and hinderances, such as (/) limitations, e.g., conformational flexibilities for both ligand and receptor, 

Despite the increasing R D and registration cost, a considerable number of new compounds have been introduced into the material protection market during the last 10 15 years. 

It is obvious that a lot of new compounds especially in the fungicidal and insecticidal area are spin-offs from agrochemical research. Important examples are azole fungicides, pyrethroids, benzoylureas and chloronicotinyl insecticides. 

In addition to new chemical entities, there are other interesting new approaches e.g. in antifouling or in using enzymes as material protection products. 

New technologies from life sciences, like the synthesis and high throughput screening of large compound libraries, can help to increase R D efficiency and to accelerate the finding of new lead structures. 

In future, the increasing R D and registration cost will make it necessary to focus the search for new compounds for material protection even more on larger market segments which can offer the required pay-back. 

This study provides evidence that Rab prenylation is important to statin-induced muscle toxicity, and that it is possible to identify suppressive small molecules that should not inhibit the beneficial effects of statins on blood cholesterol levels. The use of small molecules to dissect biosynthetic pathways is certainly not new, but affords a precise and rapid understanding of the phenotypic consequences of cellular perturbations. For the future, modern chemical biology techniques, including affinity labeling of isoprenoids [11], provide an attractive opportunity to identify the specific Rabs responsible for statin-induced muscle toxicity. As a common laboratory tool compound, G66976 is unlikely to become a clinical candidate. 

Further screening has the power to identify chemical series with improved prop-erties and more selective inhibition of statin-induced muscle toxicity. 

Tobert, JA. (2003) Lovastatin and beyond the history of HMG-CoA reductase inhibitors. Nat Rev. Drug Discovery, 2, 517-526. 

Morris, J.K., and Wald, N.J. (2012) Randomized Polypill crossover trial in people aged 50 and over. PLoS 

and Platt, R. (2004) Incidence of hospitalized rhabdomyolysis in patients treated with lipid-lowering drugs. /. Am. Chem. Soc., 292, 2585-2590. 

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M. Irving, J. Cournoyer, R.S. Li, C. Santos and B. Yan, Qualitative and quantitative analyses of resin-bound organic compounds. Comb Chem High Throughput Screening 4 353-362 2001. 

S. Bhattacharyya, Polymer-supported reagents and catalysts Recent advances in synthetic applications. Comb Chem High Throughput Screening 3 65-92 2000. 

H. Wennemers, Combinatorial chemistry A tool for the discovery of new catalysts. Comb Chem High Throughput Screening 4 273-285 2001. 

J Apostolakis, A Caflisch. Computational ligand design. Comb Chem High Throughput Screen 2 91-104, 1999. 

Table 8.2 shows the range of possible 71 values, with comments on their meaning in terms of high-throughput screening assays. 

FIGURE 8.15 Confirmation of initial hits in the HTS. Top panel shows the distribution of values from a single test concentration of a high-throughput screen. The criteria for activity and subsequent retest is all values >3 standard error units away from the mean (dotted line). The process of retesting will generate another distribution of values, half of which will be below the original criteria for activity. 

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