High-Throughput Screening (HTS) Services: Early Drug Discovery

High-throughput screening (HTS) is one of the most widely used methods for hit identification. It involves screening large libraries of compounds (often hundreds of thousands or more) against a biological target in a rapid, automated manner.

Evotec is a global leader in HTS services, offering one of the most advanced and comprehensive technology platforms in the world, combined with a vast wealth of expertise and experience in a range of modalities. 

Flexible solutions are available, including:

• standalone single- or multi-target HTS services 
• fully integrated lead discovery support. 

In the past 5 years, over €12 million have been invested in the HTS facilities, increasing efficiency and throughput for a wide variety of detection technologies. The company prides itself on the quality of its screening collection of >850,000 compounds. This collection provides access to diverse and novel, biologically relevant chemical space, and the compounds have been selected for their chemical tractability and drug-likeness.

Evotec is a global leader in HTS, offering one of the most advanced and comprehensive technology platforms in the world, combined with a vast wealth of expertise and experience in a range of modalities. 

In 2000, Evotec launched the first HTS system in miniaturized format. To date, Evotec has:

• >1,500 tailored assays developed
• >750 cell-based, microorganism-based, and biochemical assays miniaturized for use in HTS campaigns
• >5,000 proteins produced over the past 5 years
• ~ 1,600 cell lines produced
• >1,750 protein ligand complexes delivered

Significant knowledge and expertise are available to deliver novel modalities, and we offer all major screening platforms and readout technologies. 

Evotec's multidisciplinary team includes experts in:

• Biochemistry
• Computational chemistry
• In vitro biology
• Medicinal chemistry
• Automation

With an excellent combination of disease biology knowledge, as well as drug discovery and development expertise, Evotec selects the most suitable screening strategy for your target class and therapeutic area of interest.

Discover a treasure trove of tractable chemical starting points in Evotec's extensive collection of compounds, carefully curated to fuel groundbreaking discoveries.

Evotec's screening library of >850,000 carefully curated compounds is differentiated by its:

• Quality
• Diversity
• Novelty

It has a confirmed track record of delivering chemically tractable and attractive lead-like hit compounds representing suitable starting points for medicinal chemistry optimization. 

Our compound libraries are available as:

• Single compounds
• Pools, optimized for affinity selection mass spectrometry screening (ASMS)

Furthermore, Evotec has access to >150 billion DNA-tagged compounds for DNA-encoded library (DEL) screening through its collaboration with X-Chem.

Our team of experts works with you to design the most suitable screening strategy for your target or phenotype. 

Evotec's experience in HTS is vast, and is combined with advanced technology:

• 750+ biochemical, cellular, or microorganism-based campaigns run
• >1,500 assays developed
• 10 fully automated HTS platforms, including BSL2+/3-enabled platforms for HTS of microorganisms, ensuring rapid generation of robust data

Our state-of-the-art platforms employ a wide array of detection technologies enabling superior sensitivity in screening and detection of invaluable hits with high confidence. Stringent review processes ensure the selection and prioritization of the most promising compounds with the highest likelihood of success.

Our capabilities include:

• Target-based approaches, such as biochemical, cell-based, biophysical, including ASMS and DEL technology, and fragment-based screening
• Various cellular and phenotypic screening approaches
• In silico approaches

Successful HTS requires the right combination of technology, assay quality, compound libraries, and data analytics to identify the most promising hit series for your drug discovery program.

Choosing the right screening technology is critical to the success of your hit identification campaign and depends on the following:

• Understand the target biology: 
  • The screening approach is highly dependent on the nature of the biological target, which could be a protein, enzyme, receptor, cellular process, or a complex cell-free system, for example
  • If the target is well-defined structurally, then complementary computational methods, such as virtual screening or structure-based design, will be valuable approaches to define the compound screening set and progress the hit series 
  • If the target is not well-understood, but the disease-relevant cellular phenotype is established, then phenotypic screening may be more appropriate
• HTS: 
  • Large-scale and rapid compound screening should be utilized to quickly narrow down target-specific chemical spaces and ideally identify multiple chemically diverse novel hit series to generate new IP 
  • It’s important that the developed screening assay cascades are optimized for accuracy, reproducibility, and low interference to ensure data are robust and reliable for progression to later phases
• Fragment-based drug discovery (FBDD): 
  • This technique is frequently used if the target is structurally complex. In FBDD approaches, binding of low molecular weight fragments are screened by sensitive biophysical methods, and hits are coupled, then further optimized into high-affinity small molecules
• Advanced screening technologies: 
  • A number of advanced technology platforms are available to improve hit discovery for complex proteins that are difficult to target. These include ASMS, DNA-encoded library screening, and complex phenotypic screening assays, coupled with advanced artificial intelligence and machine learning (AI/ML) methods

When choosing the screening method, it's important to consider what resources are available in terms of budget and technical capabilities. 

Engaging with service providers such as Evotec allows access to a vast amount of external knowledge and technical expertise from interdisciplinary teams – reducing the timelines and improving the overall chance of success for the project.

High-quality high-throughput screening assays forms the foundation of a successful HTS campaign, and is achieved by assay optimization, counter-screening, and hit confirmation. 

It's vital to develop high-quality and robust assays, optimized for:

• Accuracy (sensitivity and specificity)
• Reproducibility
• Minimal interference

This will reduce the incidence of false positives and negatives. To enable maximal throughput and reduce cost, miniaturization is typically required. However, maintaining accuracy remains crucial during this assay miniaturization process.

Primary assays detect on-target effects or binding using HTS readouts. The choice of assay depends on the target identity:

• Biochemical assays provide insight into target binding or modulation in a cell-free environment
• Cell-based assays provide a more physiologically relevant environment, required for certain target classes

Certain compounds may interfere with the primary assay read-out. For example:

• An auto-fluorescent compound may interfere with a fluorescent read-out
• A compound may cause luciferase inhibition in a reporter gene screen

Counter-screens are used to identify and filter out not only these interfering compounds but also compounds with a non-drug-like mode of action and prevent the progression of such compounds.

As part of the hit discovery process, active compounds identified from the primary HTS campaign are then confirmed and evaluated via:

• Confirmatory testing
• Dose-response curve assessment
• Biophysical screening
• Orthogonal testing
• Secondary screening assays

Before proceeding with large-scale screening, pilot studies are recommended to validate the performance of the assay. 

Assay development is one of the most critical stages in the hit identification process, as the quality of the assay and robustness of the automation infrastructure determine the quality of the data. Evotec has an experienced team available to discuss and plan your project. 

The quality and diversity of the compound library influence the ability to identify tractable, novel hit series for medicinal chemistry optimization. 

Evotec’s compound library features:

• Diversity of chemical space: 
  • The compound library should be well-curated and diverse, covering a broad range of biologically relevant, lead-like chemical structures and scaffolds, increasing the chances of finding high-quality, novel hit series 
• >850,000 compounds, including:
  • 800,000 maximally diverse compounds, including 50,000 “ligand efficiency” compounds
  • 25,000 fragments for fragment-based screening
  • 5,000 compounds with known bio-annotation
  • 30,000 natural products and semi-synthetic derivatives
  • 2,000 macrocycles
  • 5,000 Cys-directed covalent library
  • 1,200 RNA-focused binders
• High quality: 
  • Evotec continually invests in its libraries to expand the chemical diversity and novelty, but also to maintain the highest quality and access to new chemical modalities
  • Compounds are characterized in terms of their drug-like properties and chemical tractability 
  • Purity, solubility, and potential interference in the assays are also assessed

Success in hit identification depends on the quality of the compound library. Evotec’s library is refreshed regularly to include novel scaffolds, eliminate inactive or problematic compounds, and check for purity and solubility issues.

Hits are identified from the high-throughput screens. However, many of the primary HTS campaigns are based on testing in single-concentration (or “single shot”) assays, and active compounds need further evaluation to confirm their efficacy, potency, affinity to the target, and activity in more physiologically relevant model systems. 

This is achieved through:

• Confirmatory screening: re-testing the active compounds from the primary screen against the target using the same assay conditions as the primary screen to determine if the data are reproducible
• Dose response screening: testing the confirmed active compounds over a range of concentrations to determine an EC₅₀ or IC₅₀, usually under the same assay conditions as the primary HTS campaign to provide a more quantitative estimation of effect on the target
• Orthogonal screening: a different technology/assay is used to reconfirm the hits, such as a biophysical assay to confirm direct binding of hits to the target and assess their mode of action
• Secondary screening: to confirm the biological relevance of the hits, typically by measuring efficacy in a functional cell-based assay

Hit confirmation is a key part of the hit identification process and helps to reduce false positives and negatives. Often, it provides greater insight into the hits’ mechanism of action, and potentially early structure-activity relationships. Evotec offers an extensive range of technologies and platforms for hit confirmation and validation.

Integrating advanced data analytics and in silico technologies helps to improve the quality of hit identification outcomes.

At Evotec, we implement:

• Advanced data analytics:
  • The volume of data generated within HTS campaigns can be vast
  • Advanced data analytics can help with many tasks, including analyzing screening data to identify desired and undesirable patterns and outliers, or analyzing historical data
• Structure-based virtual screening:
  • For virtual screening, sophisticated in silico models play a vital role in our strategies
  • Distinct virtual screening approaches are applied at different stages of hit identification: at the compound selection stage, computer-aided drug design (CADD) can identify focused compound subsets for screening, reducing the cost of screening and increasing the chance of success
• Hit expansion:
  • Within hit expansion, AI/ML can be trained on the screening data to identify additional hits
  • These models are continuously evolving as new data are generated
• Hit prioritization:
  • AI/ML-enabled cheminformatics can prioritize hits for further validation by ranking compounds based on predicted activity, off-target effects, and drug-likeness
  • False positives and undesirable mechanisms of action can also be identified from prior screening data, and potential statistical false negatives could be avoided using ML approaches

Evotec has strong expertise in bioinformatics and data science. These techniques are applied at various stages of drug discovery and hit identification to reduce cost and increase success. Feedback loops between screening data and compound selection are key to incorporating knowledge into the next iteration.

Partnering with Evotec means accessing 25+ years of HTS expertise, our carefully curated >850,000 compound library, and 10 automated screening platforms, along with direct scientist-to-scientist collaboration. 

Our platform-agnostic approach adapts to your target biology. This flexibility, combined with the expertise of our multidisciplinary teams, delivers strategic insights that increase the probability of successful hit identification and translation into lead optimization.

Let's design your screening strategy together.

HTS is performed at an early phase in the lead discovery process. It involves screening thousands or millions of compounds through a previously developed biological assay using automation. HTS identifies potential hits that show binding or activity against a particular biological target or cellular phenotype. 

Data generated can be used to guide future compound selection, hit expansion, and early structure-activity relationships. HTS could also serve as an engine to generate high-quality big data sets to build AI/ML models.

HTS uses miniaturized assays and automation to screen large compound libraries, generating data rapidly and cost-effectively. Setting up, maintaining, and staffing HTS facilities is expensive and time-consuming, so using an external partner is recommended for both heavy and light HTS users.

Modern HTS is a highly multidisciplinary approach, and the success of screening programs relies heavily on experience in automation, analytics, biology, medicinal chemistry, data science, cheminformatics, and operational efficiencies, to ensure identification of the most promising and tractable hit series.

Large, established contract research organizations (CROs) such as Evotec have state-of-the-art infrastructure already in place for HTS, as well as access to multidisciplinary teams. Tapping into large internal compound libraries, a vast wealth of knowledge, and a wide range of technology platforms can reduce time and cost, and increase the likelihood of success without a major up-front investment in infrastructure and personnel.