BellBrook Labs' Transcreener® HTS Assays Used to Explore New Ways to Attack Diseases

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Two recent scientific publications show how Transcreener Assays for AMP/GMP and ADP detection enable high throughput screening (HTS) with emerging drug targets including chaperone ATPases, phosphodiesterases, fatty-acyl CoA synthetases and peptide ligases. The availability of robust HTS methods will facilitate the identification of selective inhibitors for these promising drug targets, an important first step in exploring new strategies to battle cancer, bacterial infections and other diseases.

Most drugs exert their effects by interfering with the disease-related function of a few types of proteins such as GPCRs or protein kinases, commonly called “validated” drug targets. Because developing new drugs is an extremely expensive and risky undertaking, pharmaceutical companies understandably direct most of their R&D activities efforts into these validated drug targets or closely related proteins. However, the track record of this approach in recent years has been less than anyone would have expected, with clinical attrition rates remaining close to 90%.

One line of thinking is that the validated drug target families may be tapped out to some degree, and that targeting new types of proteins with compelling links to disease pathologies may provide a more fertile ground for truly groundbreaking discoveries. Often, the initial technical hurdle to pursuing a new drug target is development of an assay – a method for monitoring its function - that is suitable for an automated HTS environment. Two recent research reports, one authored by staff scientists at BellBrook Labs and the other by investigators at London’s prestigious The Institute of Cancer Research (ICR), highlight the use of BellBrook’s Transcreener Assays to overcome significant assay development challenges with promising drug target enzymes.

Dr. Wynne Aherne and her colleagues at the ICR used the Transcreener ADP Assay to detect the ATPase activity of two molecular chaperones, Hsp 90 and Hsp 72, and reported their results in the March volume of The Journal of Biomolecular Screening (J Biomol Screen. 2010 Mar;15(3):279-86.). These chaperones are believed to provide selective growth advantages to cancer cells by rescuing damaged and/or aberrant proteins from degradation and by increasing the survival of the cancer cells. Small molecule inhibitors of chaperone ATPase activity have already entered clinical trials, and new ones with fewer side effects are being sought by several pharmaceutical and academic laboratories. The requirements for the ICR study were particularly demanding, and included the very low activity of the Hsp90 enzyme and the need for very high ATP concentrations – as much as one millimolar - which made existing assay technologies unsuitable.

Dr. Aherne, who established the HTS facilities in the Cancer Research UK Centre for Cancer Therapeutics at the ICR, worked closely with BellBrook scientists, most notably Dr. Tony Klink, to optimize assay conditions with the Transcreener ADP assay, and was ultimately able to achieve robust detection with significantly reduced enzyme usage and shorter assays times relative to alternative methods. Dr. Aherne reported, “It was a pleasure working with Tony Klink and his colleagues at BellBrook Labs. The Transcreener ADP Assay proved to be particulary useful for measuring the ATPase activity of HSP90 and HSP72 even at high ATP concentrations. We are currently applying the assay to other novel targets selected for the discovery of new cancer drugs.”

Dr. Paul Workman, Director of the Centre for Cancer Therapeutics and a coauthor on the ICR study, will present some of the results at the 2010 Society for Biomolecular Screening meeting in Phoenix, AZ next month. "We are delighted to work with BellBrook Labs to harness their expertise in assay development. This is part of our overall approach to work with a range of excellent partners in the fight against cancer,” Dr. Workman says.

Transcreener is a universal, high throughput biochemical assay platform developed by BellBrook Labs for detection of nucleotides, which are formed by thousands of cellular enzymes, many of which catalyze the covalent regulatory reactions that are central to cell signaling and represent new opportunities for therapeutic intervention. It relies on highly specific antibodies that detect nucleotides coupled with homogenous fluorescent detection formats suitable for automated HTS applications. A key advantage of the method is that a single Transcreener assay can be used with any enzyme that produces a given nucleotide, allowing detection of hundreds of different drug targets. Moreover, it is the only enzyme assay method that allows direct detection of nucleotide enzyme products without the use of additional coupling or reporter enzymes, which are a source of interference by chemical library compounds. BellBrook currently holds three patents on the Transcreener technology.

In a separate report published in Assays and Drug Development Technologies (Assay Drug Dev Technol. 2010 Feb 17 Epub ahead of print), BellBrook Labs scientists led by Matt Staeben report on the development of a Transcreener assay for AMP and GMP and its validation for detection of phosphodiesterases (PDEs), ligases, and synthetases. The ligases and synthetases are especially challenging enzyme classes from an assay development standpoint. They use the energy of phosphodiester bond cleavage – usually ATP or NAD - to catalyze the joining of diverse molecules, including peptides, nucleic acids, and lipids. Most alternative assay methods rely on detection of the ligated products, which requires development of a new assay for each enzyme. However, the other product of these reactions is almost always AMP, which means that the Transcreener AMP/GMP assay can be used to detect the vast majority of ligases and synthetases. In one of the more notable experiments in the recent report, Dr. Staeben was able to monitor flux through the multi-enzyme ubiquitin ligase cascade with the Transcreener AMP/GMP assay. BellBrook is following up on these results as ubiquitin ligases and related peptide ligases are under intense focus as potential therapeutic targets for a broad range of diseases including cancer and viral infections.

About BellBrook Labs:
BellBrook Labs, LLC was founded in 2002 and currently employs 21 people. The company develops detection reagents and microfluidic devices that accelerate the discovery of more effective therapies for cancer and other debilitating diseases. Transcreener® is a patented high throughput screening assay platform that was introduced in 2005 and is used to identify inhibitors for kinases and other types of protein drug targets. The iuvo™ Microconduit Array technology is a line of unique microscale devices for miniaturization and automation of advanced cell models that are more representative of human physiology. Visit BellBrook’s website for more information http://www.bellbrooklabs.com

The Institute of Cancer Research (ICR):

  •     The ICR is Europe’s leading cancer research centre
  •     The ICR has been ranked the UK’s top academic research centre, based on the results of the Higher Education Funding Council’s Research Assessment Exercise
  •     The ICR works closely with partner The Royal Marsden NHS Foundation Trust to ensure patients immediately benefit from new research. Together the two organisations form the largest comprehensive cancer centre in Europe
  •     The ICR has charitable status and relies on voluntary income, spending 95 pence in every pound of total income directly on research
  •     As a college of the University of London, the ICR also provides postgraduate higher education of international distinction
  •     Over its 100-year history, the ICR’s achievements include identifying the potential link between smoking and lung cancer which was subsequently confirmed, discovering that DNA damage is the basic cause of cancer and isolating more cancer-related genes than any other organisation in the world
  •     The ICR is home to the world’s leading academic cancer drug development team. Several important anti-cancer drugs used worldwide were synthesised at the ICR and it has discovered an average of two preclinical candidates each year over the past five years. For more information visit http://www.icr.ac.uk.

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Robert Lowery
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