Please can you give a brief introduction to high throughput screening?
Quoting Mike Snowden (VP & Head of Discovery Sciences, AstraZeneca), “it’s where biology meets chemistry”.
It’s where for the first time a target protein can be probed for novel molecules that modulate its function, of course we want to do this to prove a hypothesis that these proteins are drug targets with the potential to deliver innovative medicines. But HTS is right at the beginning of that process it could be years before these molecules are ready to become drugs.
At AstraZeneca we carefully curate our screening collection of ~2 million compounds such that they contain a diverse set of molecules with great physical chemical properties so that they make good starting points for chemistry projects, which then optimise them.
In order to deploy this screening process we utilise assay robotics that manipulate test plates with 1536 wells, adding reagents, incubating cells and test compounds rapidly efficiently in a completely tracked system that enables us to deliver very high quality data.
Having generated this data we also need state of the art computer systems to analyse the results and enable us to identify the very best molecules.
How has the speed of screening changed over time?
Historically the high throughput screening paradigm was born in the mid nineties, as techniques to isolate natural products improved and combinatorial chemistry expanded the number of compounds available to laboratories.
With this came new plate formats and standardisation first allowing 96 well plates, then 384 and 1536 well assays to be common ground.
The speed of screening accelerated dramatically with assay technologies that allowed the reading of whole plates simultaneously these innovations were actually delivered in what was really a 10 year period ~ 95-05.
We also saw compound collections expand from a few thousand to perhaps a million or 2.
What’s interesting though is that despite this huge change in speed and capacity we did not see corresponding changes in success, that’s why we now spend much more time considering the quality of what we put into these screens, it’s no longer about time (although time and cost is important), it’s more important to get the quality right.
That is the right target the right assay technologies, we are now moving away from some simpler technologies with the knowledge that for example more complex cellular assays can better represent disease.
These actually take longer than some of the screens we ran historically and can limit the numbers of compounds we screen, but deliver a greater chance of success and that’s what’s important.
How are hits selected?
In a very simplistic way we select the active ones of course, however in life nothing is every that simple. Nowadays we run 2 million compounds in an assay which has well characterised responses, we would not run assays that do not allow statistical identification of active compounds so there is a lot of careful preparation and validation of assays before you can even start this process.
We typically identify between 10 and 30 thousand compounds from our library that are statistically active in our primary assay. We have to then ensure that these are reproducible and that they are not compounds that have non-specific effects in the assay system being used so there are then further rounds of screening to identify a smaller subset of compounds that we measure the potency of by running concentration response curves.
This is then the first point where you can start to make a judgment on how good one compound is compared to another, it is again a complex process that may involve a few thousand compounds.
Chemistry analysis is then really important to start to select compounds that look like they have the best properties and activity.
But even then it’s not finished: all the time we are combining data to reduce the numbers of compounds and home in our hit series. This could involve any number of different assays looking at the selectivity of these compounds or measuring specific liabilities, we are even looking at very early markers of toxicology to try and generate as much information as possible as early as possible so that the best choices can be made.
We hope to select perhaps 3 or 4 hit series that the chemistry teams can then start to optimise.
What is open innovation and what impact is it having on high throughput screening and hit identification?
Open innovation is very exciting. It’s an opportunity to share and become more successful, historically the way the big Pharma has behaved has not lent itself this sort of collaboration.
Pharma has historically been very protective of its assets and its intellectual property for fear of losing a competitive advantage. However, open innovation is changing this, it is clear that this new way of working opens opportunity for companies to really increase their chance of success.
By sharing corporate assets such as our High Throughput Screening infrastructure we are ensuring that they are being used against more targets than we could otherwise run by ourselves, we are gaining access to novel ideas and a degree of expertise that in some cases can only be built up in academic environments, where people have devoted their life’s work to just one disease or target area. In return the groups we are collaborating with gain access to millions of compounds, to screening expertise and infrastructure that allows the identification of starting points for drug discovery.
What’s important is that success is where the collaborators are free to take from AstraZeneca tools or starting points that they are free to continue to develop, with the only limitation being that we retain a right to negotiate in the future should a commercial opportunity present itself.
This really is a win-win for both parties often with AstraZeneca continuing to support the collaborators in different ways as the projects progress; after all it is in our interests too to have these projects become a success.
For my group open innovation has already seen 2 different external organisations place their own people in our laboratories. Where they can work alongside AstraZeneca experts and share knowledge this has been truly energising for everyone involved. And AstraZeneca has plans for the future to expand on this model with the newly announced creation of the AstraZeneca MRC UK Centre for Lead Discovery.
This ground breaking collaboration will sit within the new AstraZeneca site at the Cambridge Biomedical Campus, due to be completed in 2016. It will see world class MRC-supported researchers working side-by-side with scientists in AstraZeneca’s high throughput screening group, identifying new methods to better understand a range of diseases and potential treatment options.
As part of the collaboration, which will run for an initial period of five years, academic researchers will benefit from unprecedented access to over two million molecules in AstraZeneca’s compound library, as well as its state-of-the-art high throughput screening facilities at the new site.
Research proposals will be submitted to the MRC that will independently assess and select the best scientific proposals from a broad range of therapy areas and diseases. The MRC will fund up to 15 screening projects per year to be carried out at the Centre for Lead Discovery.
AstraZeneca will have the first option to enter a negotiation to license any resulting drug discovery programmes of relevance to the company’s therapeutic areas of interest. If this option is not used, the academics can negotiate with other parties.
Of course for me and many people working in this industry open innovation is exciting because it’s great to have the opportunity to work with great scientists across AstraZeneca as well as with world class researches within organisations such as the MRC, it’s even better because success means bringing more medicines to patience and that gives us a real sense of achievement.
What excites you most about the future of high throughput screening?
There are some opportunities to work differently with technology vendors and collaborators and I think the HTS department is a pivotal part to play in how this develops in the future.
Right now there is real excitement about the AstraZeneca MRC UK Centre for Lead Discovery and rightly so this is going to be very important for our collective success. However, there is a sense that this is just the beginning; AstraZeneca has recently launched an open innovation portal where other researches can bring new ideas and work with us in a similar way, or work with us to validate targets, gain screening sets that they can use in their own laboratories or even send us their compounds for testing. It’s a completely different approach to working with the outside world and this is very exciting.
With the creation of the Cambridge Bioscience Centre we also have the investment in the creation of the AstraZeneca MRC UK Centre for Lead Discovery this will mean the re-investment in a world class screening infrastructure in the UK. This is very exciting for the future of the UK pharmaceutical industry and the future of what is the last pharmaceutical HTS centre in the UK.
But more importantly than that it is an opportunity for an HTS centre to work with automation companies and technology development organisations so that the infrastructure that is deployed is world class and remains world class for a long time.
What hurdles need to be overcome in order to increase the efficiency of high throughput screening?
That’s an interesting question; of course historically we have seen many increases in efficiency through the introduction of high density plate formats and new plate reader technologies. We have also seen the reduction in the number of HTS sites with companies seeing efficiency gains in centralising such activities.
With every novel approach it’s important that we continue to drive down cost, while we increase the quality and speed.
There may be some opportunities for higher density formats but I don’t see a large efficiency increase in these as the standard plate types are often a cheaper option.
I do see some opportunity for the use of novel technologies like microfluidics for example. Here the potential is that we could deliver 100’s of fold reductions in cost, allowing concentration response cure definition of a compound collection or testing of multiple conditions.
However, as yet it’s not fully validated as a screening technology with some technical issues still to resolve regards getting the compound collection into such devises and it’s yet to be completely proven at a quality level too.
I think as we move forward we will see more smart screening, this to me means not necessarily predicting what we think are going to be hits and screening these, but instead really trying to understand our compound collections. Annotating them with important data early so that compounds with properties complementary to the target can be selected for screening.
Of course all of Pharma’s efficiency is based on selection of the right targets; we have seen the renaissance of the phenotypic screening paradigm. This too impacts HTS and the definition of compounds having activity in certain phenotypic assays may be some of the data we need to generate to understand our compound collections.
However, it appears that the real power in phenotypic screening will be its ability to identify targets that will translate to the clinic. By identifying these targets and screening the ones which we have high confidence in we could increase the efficiency of HTS (and drug discovery) in a way that we had not necessarily projected 5 or 10 years ago.
Where can readers find more information?
About Mark Wigglesworth
Mark Wigglesworth joined AstraZeneca in Sept 2012 to lead the newly formed Global High Throughput Screening Centre.
His screening experience was gained at SmithKline Beecham and then GlaxoSmithKline where he worked extensively in GPCR drug discovery initiating and leading a number of projects to deliver lead molecules to drug discovery programmes.
Mark has led groups of scientists responsible for delivery of structure activity relationship data to iterative chemistry programmes as well as working within Compound Management.
Mark has contributed to numerous publications in the field of GPCR pharmacology and Compound Management including editing a book describing the Management of Biological and Chemical Samples for Screening Applications.
In his current role he leads a team of more than 20 scientists dedicated to identifying novel chemical starting points for drug discovery programmes.