What is High Throughput Screening?

An introduction to the world of high-throughput screening, a brief history of the technology, and the many ways this technology is being used today

Learning objectives:

1) Be able to define high-throughput screening

2) Understand the history of high-throughput screening and how it has progressed since then

3) List some of the basic methodologies for high-throughput screening

4) Understand the use of high-throughput screening in drug discovery 

The world of high-throughput screening is a new and exciting horizon in scientific research, but to begin it is worth answering the question: what is high-throughput screening? High-throughput screening is a method that uses robotics, highly sensitive detectors, and data processing software to test hundreds and thousands of compounds in miniaturized in vitro assays to measure their ability to activate, inhibit, or otherwise modulate a biological target of interest. If the definition alone isn’t all that exciting that is fair, but throughout the following article, the reasons why this technology is so incredible will become clear and hopefully articulate the power of high-throughput screening.

The origins of high-throughput screening, like almost everything else in science, came from a lack of efficiency in the old way of doing things. Researchers in Pfizer’s natural products screening group were looking to manipulate R DNA within Streptomycete clones in order to produce novel antibiotics and improve antibiotic production (1). With libraries of thousands of Streptomycete clones, numerous culture broths, and a number of environmental conditions, screening at their current fastest rate would take researchers far too much time to complete. As such, an automated screening process using 24-well plates and a robotic system to inoculate and dispense fermentation broths onto these plates containing bacterial indicators was created marking the beginning of high-throughput screening. Over the coming decades, improvements to the technology were made which included increasing the size of compound libraries and combinatorial chemistry. Combinatorial chemistry made it possible for scientists to manipulate compounds that had properties of interest but were not quite interacting with the target in a productive way, which are known lead compounds. Further increases to the power of high-throughput screening came in the form of more miniaturization with the introduction of microfluidics and plates with as many as 3456 wells (2).

With so many compounds being tested, the need for efficient mechanisms for quantifying compound-target interactions was high. Today, the most common methods for measuring interactions in a high-throughput screen are fluorescence and bioluminescence (2). These technologies use fluorescent reporters that increase their fluorescent activity with increasing compound-target interactions thus giving scientists an idea if a chemical could efficiently interact with a target (a.k.a. a hit) and how high of an affinity for interaction a compound had. Another common methodology used in high-throughput screening today is the division of assays into phenotypic vs target-based screens. A phenotypic-based screen measures outputs from biochemical processes when a whole cell is exposed to a compound. This differs from a target-based screen which utilizes isolated products such as enzymes and measures interactions of compounds with only that target molecule (3). While a target-based screen allows you to measure direct interaction, it does not give you an idea of how this occurs within a whole-cell while the opposite is true for phenotypic assays so choosing between the two approaches is important during high-throughput screens. Though there are many more nuances to high-throughput screening, the information provided so far should give you a decent idea of the robustness and versatility of this technology.

Of all the uses of high-throughput screening, one of the most prevalent and important is in drug discovery. Drug discovery entails screening a library of compounds to test for their ability to inhibit or enhance the activity of a target. When a hit or lead compound is then identified, it must be further optimized for potency, selectivity, and pharmacokinetics (4). While the first phases of screening are typically done so using a target-based approach, interaction here does not indicate the drug activity in vivo. The next phase of drug trials will then usually consist of a phenotypic screen to further identify drug candidates for future stages of testing. Though screening only represents the preliminary phases of drug development, high-throughput technologies are vitally important in this sector and allow the discovery of new drugs to occur on a near-daily basis worldwide.

Though drug discovery is arguably the most significant use of high-throughput screening technology, it only represents one of many applications. High-throughput screening is a robust and reliable methodology that has evolved rapidly since its creation in the early 90s and will continue to become more reliable, affordable, and accessible in the near future.

Questions and Answers

1. What is high-throughput screening? High-throughput screening is a method that uses robotics, highly sensitive detectors, and data processing software to test hundreds and thousands of compounds in miniaturized in vitro assays to measure their ability to activate, inhibit, or otherwise modulate a biological target of interest. 
2. Who completed first high-throughput screening experiment and what were they doing? The researchers in Pfizer’s natural product screening group were attempting to discover novel antibiotics and antibiotic production methods
3. What are the two methods used for measuring interactions? Fluorescence and bioluminescence readings 
4. What are two common methodologies used in high-throughput screening? Phenotypic and target-based screens 
5. What is drug discovery? Drug discovery entails screening a library of compounds to test for their ability to inhibit or enhance the activity of a target

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References

1.Pereira, D. A. & Williams, J. A.. Origin and evolution of high throughput screening. British Journal of Pharmacology 152, 53–61 (2007).

2.Attene-Ramos, M. S., Austin, C. P. & Xia, M.. in 916–917 (2014). doi:10.1016/b978-0-12-386454-3.00209-8

3.Avery, V. M., Camp, D., Carroll, A. R., Jenkins, I. D. & Quinn, R. J.. in 177–203 (2010). doi:10.1016/b978-008045382-8.00062-9

4.Carnero, A.. High throughput screening in drug discovery. Clinical and Translational Oncology 8, 482–490 (2006).