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Research at the speed of light
One of the more recent innovations in drug discovery, high-throughput screening (HTS), is made feasible through advances in robotics and high-speed computer technology.
For scientists working in HTS laboratories, there are myriad challenges, including pressure to find increasing numbers of drug leads while containing costs. As a result, many are seeking larger compound sets, more automated systems to screen them faster, and an integrated set of equipment and consumables.
High-throughput screening requires the miniaturization and automation of in-vitro bioassays so that millions of variables can be tested. HTS is often an important step in the discovery of new medicines.
In this first installment of a multi-part series in ddn, we focus on some of the key developments in recent years with regard to screening technology and look ahead to see what the future holds.
J. Fraser Glickman, director and research assistant professor of the High-Throughput Screening Resource Center at Rockefeller University, points out that there have been several key developments in HTS in recent years.
"Among them, I would place the improved throughput and analysis of high-content technologies based on image analysis of cell samples, and so-called 'fragment-based' approaches for measuring binding of compound fragments," he says. "Also, we have seen a vast improvement in the automation of microtiter plate processing and the associated scheduling software. Cheminformatic software has also become phenomenally more effective."
Houston, Texas-based Selleck Chemicals is a worldwide supplier of high-performance kinase inhibitors and antibodies for cell signaling and oncology research. Sales director Sunny Xu notes that functional genomics with their RNAi and cDNA technologies are well-known recent applications of HTS.
"They are called siRNA high-throughput screening and cDNA library high-throughput screening," Xu says. "Particularly, the former will help scientists to understand the molecular basis of tumorigenesis, identification of therapeutic targets and so on. Capillary electrophoresis (CE) or HPLC-based HTS systems could be applicable to complex and even unpurified chemical mixtures, speeding up the identification of active components."
Dr. Rathnam Chaguturu is the director of HTS laboratories and courtesy research professor of molecular biosciences and medicinal chemistry at the University of Kansas.
He sees an increased awareness of label-free, HCS/HCA and multiplexed assays for screening and profiling.
Label-free: The way to be?
Chaguturu points out that there is a growing tendency now to adopt label-free platforms.
"Currently, most assays for the detection of biologically relevant binding events use either radioactive or fluorescent dyes to tag one or more molecules, over expression of the biological target of interest, or reporter proteins," he says.
Simply put, Chaguturu explains that this is quite an unnatural set-up. Furthermore, researchers are restricted to a simplistic biology assessment with just point-of-contact measures and one signaling pathway per ligand-receptor complex.
"We know that the therapeutic targets do not function in isolation, but operate in a systems biology context involving a complex set of integrated biochemical pathways, and we need to find a way to quantitate these processes," he says. "This is where label-free technologies come in to play as 99.5 percent of human genome has not yet been fully exploited for drug discovery."
The main reason, according to Chaguturu, is because the pharmaceutical industry has operated mainly in low-risk territory with potential for greater return on investment.
"Academia is the one that feeds new therapeutic targets for the pharmaceutical industry to pursue," he says. "Academia, by the nature of its mission, works in this unchartered territory of high risk and low reward, but for it to make headway, it is limited by the availability of easily adaptable technology formats to deorphanize the highly refractory targets. The label-free assay technology is widely applicable for many classes of targets and cellular processes."
Chaguturu explains this is especially useful in a systems biology context in charting metabolic pathways.
"Label-free technology is the way to go in deorphanizing these refractory targets, and that can be done without long and costly assay development process," he says. "Next, this technology allows us to generate biologically relevant data in a systems biology context. It is especially useful as an alternate readout technology for use in the hit-to-lead optimization process, and you can work with primary cell lines and without the need for engineered cell lines."
Glickman points out that over the last 15 years, the field of HTS has gone from infancy into a mature and robust approach, as evidenced by the growing number of labs throughout the world and in various sectors, which no longer view it as an experimental new technology, but rather as a requirement in order to have a healthy and competitive research program.
"We always keep a certain capacity for scanning the horizon for new screening technologies, and for being creative in the way we improve our efficiency," he notes. "Many of the pitfalls associated with HTS have now become transparent, and the community have actively presented resolutions to these issues."
As with any developing technology, change can be rapid, and in recent years, acoustic technology has been playing a large role in HTS. With so much technology changing so rapidly, there remain plenty of challenges facing scientists in HTS laboratories.
Xu notes that examples of key changes are robotics, miniaturization, sophisticated assay chemistry to sophisticated software and database.
According to Glickman, the main challenge "is keeping costs down and efficiency up. This does not only apply to HTS but to drug discovery in general, which is facing and will continue to face sustainability issues related to the cost burden on society."
According to Chaguturu, assay development is the most critical component leading up to a screening campaign.
"For assay development work, robotics is not a deciding factor, but for screening campaigns, liquid handling robotics is a must without which no amount of FTE could measure up to the throughput needed, and do the tasks in a timely manner," he says. "So the biggest challenge is the development of appropriate assays in a timely fashion."
Adapting to changes can be analogous to trying to turn a battleship, and Chaguturu contends that pharma greatly underestimates the significance of toxicobiology, and doesn't understand it well enough to pick the right drug targets.
"Pharma is not set up to do this sort of research," he said, noting it "warrants collaboration between industry and academia."
The trend he views is pharma developing partnerships with academia in an open-platform paradigm to advance drug discovery endeavors. He points out several examples, including Novartis and Institutes for Biomedical Research; GlaxoSmithKline (GSK) and Centers for Excellence for Drug Discovery; Pfizer and the Biotherapeutics and Bioinnovation Center; Lilly and Phenotypic Drug Discovery (PD2) Initiative; and Merck and Sage Bionetworks.
Moreover, a dozen competing drug companies have agreed to share data on thousands of Alzheimer's patients in hopes that the extra information will spark new ideas for treatments. Called the Coalition Against Major Diseases, the collaboration pairs patient-advocacy groups with such pharmaceutical giants as GSK, Pfizer and AstraZeneca. It is led by the Critical Path Institute, a nonprofit partnership associated with the U.S. Food and Drug Administration (FDA) that aims to speed discovery of new drugs.
A new decade, a new mantra
Even with the ever-changing technologies, Chaguturu notes that the drug discovery landscape is at a crossroads with profound changes looming in the horizon, and open innovation becoming the new mantra for reinvigorating the pharmaceutical R&D's lackluster drug candidate pipeline.
"To fill this void, academia has now ventured from its traditional role of exploring the fundamental aspects of disease biology into the high -throughput screening arena in a big way, thanks to the NIH Roadmap Initiative and the EuOpen Screen program for facilitating this transition," he says. "The oft-quoted myth that high-throughput screening has not been the panacea for drug discovery, as one was led to believe at first, has now been squashed as the origins of many of the drug candidates in pharma's pipeline can now be traced back to in-house HTS campaigns. HTS has found its niche in academia with research priorities in drug discovery endeavors."
Researchers, Glickman points out, are continually looking ways to improve their processes and striking the right "economy of scale."
"Scientifically, the main question for us is how we can improve the predictive value of the in-vitro tests we perform to translate well into in-vivo results," he says. "As academics, we also try to place ourselves in target areas where there is little published information. Another challenge is finding talented, classically trained medicinal chemists to improve the properties of hits, which can be a long, unpredictable and arduous task."
Chaguturu points out that with the flow of top pharmaceutical drug discovery scientific talent in to academia and the industrialization of small molecule library synthesis, academia is poised to take drug discovery to new heights.
"There is also a much-needed collaborative spirit between pharma and academia in closing the risk-reward gap as exemplified by a number of industry-academia collaborative agreements that are being put in place," he says. "The technology transfer offices are now generally charged in guiding the researcher in IP disclosures, patenting decisions and commercialization of research results. This has transformed the faculty in to entrepreneurs in managing their inventions. So, the long-term future is quite bright."
Xu concludes that HTS technologies will be more widely accepted by pharmaceutical and biotechnology companies as an integral part of their drug discovery processes and the HTS market will continue to grow.
"Technological advancements will revolutionize the market," Xu says. "Technological advancements such as the use of robotics and cell-based assays have had a significant impact on the HTS market. HTS reagents and assays are experiencing increasing demand, leading to intense competition among reagent manufacturers, much more than among instrument manufacturers."
Glickman is very positive about the future of HTS, in the sense that as an approach to identify chemical lead compounds, it has become a "proven performer."
"I also feel that many of the technological innovations that have been designed for HTS drug discovery purposes, are starting to bleed over into other fields, such as RNAi screening, and in addressing basic scientific issues using the analytical techniques performed in microtiter plates," he says.