What is an Inhibition Assay?

An inhibition assay is a laboratory test that is implemented during pharmaceutical drug testing. The purpose of the assay is to determine whether the activity of a drug, such as an enzyme, is affected by the administration of a second molecule.

In simple terms, this means that an inhibition assay can be used to assess the effect of one drug on another, known as DDI (drug-drug interaction).


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The behaviour of enzymes

Enzymes are proteins that play a key role in the human body. They act as catalysts of chemical reactions in living organisms. They speed up the reaction in the cells and are essential for life.

Enzymes have three main purposes in the body:

  1. Breaking down molecules in the digestive system to supply the body with the components that it needs to survive.
  2. Processing toxins in the liver that can be harmful to the body.
  3. Replicating DNA to generate new cells with identical copies of the original ones, which is essential to living organisms.

However, sometimes enzymes do not work efficiently. For example, they can act too fast, and they may need to be slowed down, what is known as inhibition.


An enzyme inhibitor is a compound that modifies the normal activity of an enzyme by reducing the speed of the process. This plays a key role in drug discovery and inhibition assays are essential to identify the effect of molecules on enzymes.

Sometimes, the cells in the body react in a way that is not expected, leading to harmful processes and causing disease. Enzymes inhibitors are molecules that can bind to these enzymes, slowing down their activity and reducing harmful processes.

Inhibition can take place in different ways:

  • The substrate has to compete with the inhibitor to attach to the enzyme.
  • Non-competitive. The enzyme cannot work effectively when the inhibitor binds.
  • Uncompetitive. Once a substrate and an enzyme are bound, the inhibitor binds to them slowing down the reaction.
  • Irreversible. The inhibitor permanently disables the enzyme and its ability to speed up reactions.

These inhibition methods are essential to prevent the activity of enzymes that act abnormally.

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What is the meaning of inhibition in the context of drug testing?

An enzyme inhibitor is a drug candidate extremely valuable in Drug discovery. When enzymes do not work correctly due to hyperactivation, overexpression or dysfunction, they can cause disease(s) as the processes of the body do not function correctly. Example on many rare diseases, but with a genetic involvement usually.

If an enzyme speeds up, it must be stopped to prevent diseases or illnesses from evolving. This is when an inhibitor can be used to slow the activity of an enzyme.

The importance of inhibition assays

Inhibition assays are one of the main ways of discovering the mechanisms of diseases. Enzyme inhibitors can help with the understanding of diseases and their development. For example, they can be used as cancer-fighting agents.

An example of this can be seen in penicillin. This antibiotic inhibits the enzymes that produce the peptidoglycan that is essential for the cell wall of bacteria. The human body does not produce peptidoglycan, so the use of penicillin as enzyme inhibitor is very useful for destroying harmful bacteria.

The assay, performed in vitro, consists of the addition of a compound to an enzyme to detect the inhibition. This study is essential to understand the activity of drugs and to identify possible effects on diseases.

Inhibition assays are also useful to understand how drugs react with each other in the human body. If a person suffers from more than one affliction, medical practitioners need to understand how one drug reacts with another to prevent an adverse reaction.

Inhibition assays are therefore essential for drug screening as they allow identifying how an active compound can work more effectively. They play a key role in Drug discovery and development process to understand how they work in order to prevent and cure human diseases.

Those efficacy screenings can be developed in vitro or in vivo, also in alternative animal models such as zebrafish. Biobide can design efficacy assays in zebrafish, to demonstrate the efficacy of drug candidates related to enzyme inhibition activities. Apart from testing them for safety too. This way, the best candidates can be selected earlier and then move forward in a more cost and time-efficient way in the Drug discovery and development process.


  1. https://www.sciencedirect.com/topics/chemistry/enzyme-inhibitor
  2. https://www.medicalnewstoday.com/articles/319704#the-basics
  3. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0023627

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