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Exploring the Potential of Mass Spectrometry in Drug Discovery: A JBS Special Issue

Somewhere in a nearby lab or on an exhibition floor is a technology that some research scientists know about, but might not embrace in their daily work in drug discovery. Adapting its use by pairing it with other technologies opens a world of potential that is currently examined in a special issue of the Journal of Biomolecular Screening (JBS).

 

There's an element of mystery and a few myths around mass spectrometry (MS) that JBS Guest Co-Editors Jonathan Wingfield, Ph.D., AstraZeneca (U.K.), and Ian Wilson, D.Sc., of Imperial College (U.K.), hope to dispel. "One is the idea that MS is a high-tech platform that tends to be operated by specialists," comments Wingfield. "That impression can be a potential barrier that stops people from wanting to use this type of technology. I hope this collection of papers appearing in a rigorously peer-reviewed, main-stream scientific journal will debunk some of these myths and get people interested in the potential of MS."

Wilson agrees. He sees the issue as an opportunity to demonstrate how MS-based techniques can impact any area of discovery. "I would hope that it will encourage further innovation in the use of the technique," he comments. "MS is absolutely essential for industry and academia to push back the boundaries in an efficient and timely way."

The February 2016 JBS special issue, "Advances in Mass Spectrometry within Drug Discovery," focuses on progressive improvement in both the speed and sensitivity of MS-based techniques that are facilitating an ever-increasing number of applications for high-throughput screening (HTS). The issue demonstrates new ways in which MS has evolved from its initial use for structure determination to one where the bulk of applications now revolve around routine applications in analyte detection and quantification.

Wingfield notes that MS platforms are not inexpensive assets to own. "You get the sense that people are pushing those assets to the limit to seek out new functions to improve their return on investment for those systems," he observes. "The special issue shows novel, cutting edge applications, but also the reapplication of existing technologies to improve throughput and drive down costs or to enable the ability to multiplex."

Wingfield and Wilson believe that this collection of manuscripts captures the many screening applications that MS currently supports from HTS MS platforms and new targets, methods for screening for DGAT2 inhibitors and fatty acid synthase inhibitors, the versatility of MS and how it can be integrated with other assay platforms to deliver high value data, and screening via bioaffinity-MS, to use of a bead/lysate-based affinity capture method coupled to MS analysis for target identification in a cell-based phenotypic screen, a novel targeted lipidomics platform for monitoring eicosanoid lipid modulation, MS-imaging and more.

"General scientists in drug discovery might find it difficult to explore all this information on their own," Wingfield notes. "I thought it would be useful to bring those threads together so that someone who is interested in drug discovery, who has a minor knowledge of MS, could get a flavor of the diversity of the applications within our area of research. This is a good opportunity to bring MS research together in one journal that enables the SLAS readership to get that broader perspective."

Whether it was his own growing interest in MS or an uptick in interest by the entire life sciences discovery and technology community, Wingfield began to notice a distinct increase in conference presentations and dialog about MS's potential in drug discovery in the last couple of years. He found the MS-focused poster and podium presentations at SLAS2015 particularly intriguing.

"I spoke with some of the speakers afterward and encouraged them to use the upcoming JBS special issue as a way to get their research out into a broader community," says Wingfield, who is an author in both JBS and the Journal of Laboratory Automation (JALA), two SLAS-published, MEDLINE-indexed scientific journals.

"The power of the journal is that you can put the same data that you might present to 100 seminar attendees out on the desks of thousands of scientists and SLAS members," Wingfield says. "Part of developing this special issue is going out, listening to presentations and recruiting authors. This approach was well received by the authors and helped streamline our work during the review process because we were already familiar with the subject matter in many cases."

From the Familiar to the Forward-Looking

Wingfield believes readers will be impressed at how MS technology adapts. "From fairly bread and butter type activities for people in the drug discovery space, such as routine biochemical screening, to measuring compound concentrations in cells, there's not a typical application in this collection of articles. It really shows the ingenuity of the people using these systems," he observes.

As an example, Wingfield mentions "Microfluidic Chip–Based Online Screening Coupled to Mass Spectrometry," by Janaki Krishnamoorthy Iyer, et al, which discusses the development and optimization of a microfluidic online screening technique coupled to nano–liquid chromatography (LC) and in parallel with MS for the identification of thrombin and FXa inhibitors in mixtures. He also points to "The Evolution of MALDI-TOF Mass Spectrometry toward Ultra-High-Throughput Screening: 1536-Well Format and Beyond," by Carl Haslam, et al. which looks at MALDI technology for high-frequency, high-density screening.

"We've got examples of people using mass spectrometry in the natural products space as well in another screening application," he continues, describing "Bioaffinity Mass Spectrometry Screening," by Ben Yang, et al. This article examines the use of electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS or ESI-FTMS) to screen 192 natural product extracts and a 659-member natural product-based fragment library for bindings to a potential malaria drug target, Plasmodium falciparum Rab11a (PfRab11a, PF13_0119).

"Even when the papers discuss well established technologies there are different ways of applying it," says Wingfield, using as an example the RapidFire technology applied in both "A High-Throughput Screen to Identify LRRK2 Kinase Inhibitors for the Treatment of Parkinson's Disease Using RapidFire Mass Spectrometry," by Melanie Leveridge, et al. as well as "Direct Measurement of Intracellular Compound Concentration by RapidFire Mass Spectrometry Offers Insights," by Laurie J. Gordon, et al.

"I'm certain there are more applications out there," Wingfield comments. "It's quite clear that one size doesn't fit all. You have to adapt and blend the MS techniques to the applications." As is done in "Exemplifying the Screening Power of Mass Spectrometry Imaging over Label-Based Technologies for Simultaneous Monitoring of Drug and Metabolite Distributions in Tissue Sections," by Richard J. A. Goodwin, et al, in which the contributors reveal MS advantages that enable scientists to explore compound distribution in tissue sections.

"MS is not a tool in which you can just open the box and start using it," Wingfield states. "You have to think about blending the biology with the system you are using and matching that to the MS platform that you want to use. As a scientist, I find that interesting and challenging."

Discovering Where MS Intersects with Drug Discovery

Wingfield comes to the MS technology from a different perspective and identifies with the audience he hopes to reach. "My personal background is not in MS," he explains. He began to explore its potential through a collaboration his lab pursued to use an acoustic droplet ejection (ADE) platform, which they were using extensively in the compound management space to move microscopic amounts of liquid, and adapt that technology to accommodate an MS backend to evaluate the liquids. For this work, Wingfield's team received the 2015 SLAS Innovation Award, which can be accessed for free (courtesy of Labcyte Inc.) at both SLAS.org and in the February 2016 special issue of JALA on Advancing Scientific Innovation with Acoustic Droplet Ejection.

"That's where my interest started out. However, the more I read, the more I realized that I didn't understand as much about MS as I initially thought. I guess that's often the case when you begin to probe in more detail and begin connecting between sciences," Wingfield comments. An application similar to the one developed by Wingfield's team appears in the JBS special issue. "Coupling Laser Diode Thermal Desorption with Acoustic Sample Deposition to Improve Throughput of Mass Spectrometry–Based Screening," by Zuzana Haarhoff, et al, also embraces the move toward label-free screening in drug discovery by investigating the approach of coupling ADE with laser diode thermal desorption (LDTD)–tandem mass spectrometry (MS/MS).

By contrast to Wingfield's experience, Wilson has been using MS as a part of his work for as long as he can remember to identify drug and endogenous metabolites in support of drug discovery and development. "MS has been an essential tool for the characterization of unknown compounds for me," he says.

He acknowledges being stunned by the huge technological strides that transformed MS from an expensive tool run by specialists into "a routine piece of laboratory instrumentation widely distributed in the lab and used by almost everyone," Wilson continues. "The major difference between my early experiences of MS and its use now has been the rise of hyphenation with liquid chromatography (LC)," he comments. The special issue highlights an LCMS application in the article "Development of a Medium-Throughput Targeted LCMS Assay to Detect Endogenous Cellular Levels of Malonyl-CoA to Screen Fatty Acid Synthase Inhibitors," by Philip J. Hopcroft and David I. Fisher.

"LCMS for me and many others has transformed the utility of the technique, enabling both identification and quantification to be performed," Wilson says. "If you took MS away we could still do pharmacokinetics but it would be a lot more difficult and time consuming, and much less sensitive."

These days Wilson uses LCMS extensively for both drug metabolism studies, in the search for drug metabolites that might provide mechanistic insight into toxicity, and in the search for endogenous metabolites biomarkers of disease and toxicity, using the techniques of metabonomics/metabolomics, that might also illuminate underlying biochemical mechanisms. "We hope that this work may enable drug discovery and safety assessment scientists to select the best compounds to take forward from discovery into development, and then into humans, with a long-term reduction in attrition," he says, adding that these techniques may also directly aid things such as patient stratification and precision medicine in the clinic.

The JBS special issue represents several points of connection for life sciences discovery and technology professionals. For Wilson, it's an opportunity to populate future issues of SLAS's scientific journals with further discoveries: "Other users seeing these articles might be encouraged to also publish their work to the benefit of the whole community," he concludes. For Wingfield, it's vital to raise the profile of MS: "I think it's important to open an ongoing dialog. We can use a special issue like this to give people an idea of MS potential."

Learn More in the February 2016 Special Issue of JBS

The JBS special issue on Advances in Mass Spectrometry within Drug Discovery features 12 original research reports from the U.K., U.S., Singapore and Australia, and is available now at JBS Online for SLAS Biomolecular Sciences Section members, JBS subscribers and pay-per-view readers. Free public access becomes available one year after final publication.

February 22, 2016