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Explore the integral role of assay development in the drug discovery process. Dive into how advanced High-Throughput Screening assays streamline the identification and validation of novel chemical matter for small molecule therapeutics discovery.
Assay Development Blog

The Role of Assay Development in Drug Discovery

Assays are integral tools in scientific disciplines like biology and chemistry. They are structured procedures designed to investigate biological and chemical samples in well-defined conditions. Used extensively in various fields, assays allow researchers to investigate the presence, identity, amount, interaction, dynamics and impact of chemical and biological molecules, entities, and processes in a sample. So, what is the main purpose of assay development in drug discovery?

In drug discovery, the journey from conceptualizing a therapeutic intervention to its realization as a viable drug is complex and multifaceted. One of the crucial aspects of this process is identifying and validating new drug-like chemical matters that could be further developed as potential drug candidates, especially when dealing with small molecules. Small molecules have become a cornerstone of modern therapeutics because they can modulate various biological processes, often acting as inhibitors/antagonists or activators/agonists of specific cellular pathways.

To efficiently identify these small molecule candidates from vast chemical libraries, researchers often turn to (ultra) High-Throughput Screening (HTS). HTS is a robust approach that allows for rapidly testing the impact of thousands to millions of compounds on a specific biological target or activity. This is where the importance of assay development in drug discovery comes into sharp focus. The assays used in HTS must be highly sensitive, robust, reliable, and quick to deliver results. They are the gatekeepers, ensuring that only the most promising and therapeutically desirable compounds move forward in the drug discovery pipeline.

The choice of readout technology in assays is paramount. For instance, fluorescence-based assays might be favored due to their sensitivity, making them ideal for detecting the nuanced interactions of small molecules with their target proteins. Meanwhile, label-free assays, such as MALDI-TOF mass spectrometry, can directly inform on these interactions without any potential interference from surrogate labels.

What Types of Assays Readouts Are Common?

Assays are primarily categorized into two: label-based and label-free.

  1. Label-based Assays: These assays rely on chemical or biological labels, like fluorescent dyes and proteins, to detect the target activity, binding, localization, etc. They’re revered for their sensitivity and specificity but can be complex and potentially intrusive to natural interactions.
  2. Label-free Assays: These do not rely on labels, instead leveraging the intrinsic properties of the analytes. They preserve the natural state of molecules and are simpler but may lack sensitivity and require specialized equipment.

What Are Common Assay Types?

  • Biochemical: Assays are often based on purified targets and reveal the underlying mechanisms in biological reactions and interactions, serving as the foundation of a reductionist approach to investigate complex biochemistry.
  • Cellular: Physiologically relevant assays that lead scientists through the intricate paths of cellular functions, structures, and phenotypes. Read more about Cellular Assays.
  • Biophysical: These provide insight into the affinity and binding kinetics between biological and chemical molecules, acting as interpreters of the subtle language of biophysics.

Understanding assays is imperative for anyone delving into scientific research or medical diagnostics. They are the bond holding biology and chemistry together, opening doors to discoveries and innovations.

How Are Assays in Drug Discovery Developed

Target and Hit Identification

Assay development is the bedrock of target and hit identification. In this phase, researchers define the direction of the entire project. The goal is to pinpoint what the assay aims to detect or measure. Depending on the overarching research question, the focus cou set on a particular protein, DNA sequence, chemical compound, or another specific entity of interest.

Assay Design

In Assay Design, with the target firmly established, the emphasis shifts to devising an effective procedure to detect or measure it. The crux of this stage hinges on choosing a suitable methodology. The decision between a label-based or label-free assay depends on various factors:

  • The required sensitivity
  • The nature of the sample
  • The equipment at the researcher’s disposal


Validation is paramount in establishing the reliability of the assay. During validation, the newly designed assay undergoes rigorous testing under controlled assay conditions. Three pivotal criteria are scrutinized:

  • Accuracy, which measures how close the assay’s results align with the true value.
  • Repeatability, which assesses the consistency of results under identical conditions.
  • Reproducibility, which examines the assay’s ability to produce consistent outcomes under varied circumstances.


Optimization then steps in to refine the assay, ensuring its peak efficiency and sensitivity. Researchers tinker with various parameters at this juncture: adjusting reagent concentrations, fine-tuning incubation times and assay linearity, or modifying temperature settings. The overarching goal is twofold — enhancing the assay’s sensitivity to detect even trace amounts of the biochemical, cellular, or biophysical activity and bolstering its robustness to reduce errors.


Finally, Scale-Up focuses on preparing the assay for broader application scopes. Whether the intent is to process more samples or integrate the assay into high-throughput systems, this phase adapts the optimized protocol to cater to these needs. Throughout the scale-up, maintaining the assay’s consistency and reliability remains paramount.

Selecting an Assay Development Provider

Selecting the right collaborator for assay development in drug discovery is a critical decision that can significantly impact the outcome of your research. At the top of the considerations list is the partner’s expertise. A peek into their track record can reveal if they’ve successfully tackled projects similar to yours, providing reassurance about their capabilities.

Equally crucial is their infrastructure and equipment, especially when developing specialized assays, like label-free ones, which demand specific tools and facilities.

The unpredictable nature of research also highlights the importance of a partner’s flexibility. Collaborating with a team that can seamlessly adapt to unforeseen challenges is invaluable, ensuring that the project remains on track.

Additionally, clear communication about cost and timeline is essential. No research endeavor benefits from hidden costs or unexpected delays, so it’s essential to have a transparent dialogue about financial and temporal expectations.

Lastly, the efficacy of an assay hinges on its reliability, underscoring the importance of validation and quality control. Your chosen partner should develop the assay and ensure that it consistently meets rigorous quality benchmarks.

In conclusion, the ideal assay development partner combines robust expertise, the right tools, adaptability, financial transparency, and an unwavering focus on quality.

Learn more about our tailored biochemical, cellular and biophysical assay development solutions.