Critical Role Of Cytotoxicity Test During Drug Discovery And Development


The safety of any medicinal drug is addressed starting with the early phases of drug development. Cytotoxicity assay must be run to screen through all pharmaceutical components to be used besides the active pharmaceutical ingredient. 

As the active ingredient is going to be in touch with new chemicals for stability, efficiency, and other factors, a thorough cytotoxicity screening must be done to ensure safety. 

Why Is A Cytotoxicity Test Important For Other Excipients As well?

When the active ingredient is found to be the lead component, new chemicals are not only introduced to it for stability and efficiency purposes. Some chemicals are introduced to help the active ingredient with cell penetration. This can have major effects on cytotoxicity. This is the main reason why a combination of all excipients goes through such tests.

How Is Such A Test Conducted?

For a human-specific cytotoxicity test in vitro cell lines are used. There have been great success stories associated with the ADME studies, which help draw significant inference for such tests. The in vitro systems designed for such tests have a failure rate of around 10%.

These tests are now designed to check for cell permeability, the stability of metabolites, and the interactions drug components have with the membrane transport systems, in the cell. These tests employ tiered methods to check for toxicity. Limitations and liabilities of such tiered models are checked beforehand to ensure fewer chances of failure. Different cell cultures are used for carrying out multiple screenings at this stage.

Cell Lines Used For Cytotoxicity Test

Drug development costs millions of dollars and takes a considerable chunk of time. This is why it’s necessary to develop assays that would lower the chances of failure. Cell-specific lines are chosen to test biocompatibility and viability. Here’s a list of cell lines used for conducting cytotoxicity assay:


This cell line originates in adult human skin. This line is chosen to test penetration through the skin and can be used to test topical solutions.


This cell line originates in the bronchial epithelium and the respective studies are conducted to check the absorption and excretion through the cell line.


Originating in osteosarcoma cells, this line is used to test transport and absorption in drugs.

HeLa & A431

The origin of this line is the epithelial cervical cancer cells and is used for checking drug toxicity and is widely used for cancer research.

HCT-116, HT29, Caco-2 

Originates in cell adenocarcinoma cells and is widely popular for toxicity tests and to check epithelial absorption of the intestine.


Originating in the submucosal glands (serous cells), this cell line is concerned with drug delivery conducted to the respiratory epithelium.

It can be said that these tests also confirm how effective the drug delivery would be through a certain cell line. Cytotoxicity assay is best conducted in a GLP as the chances of implementing validated test procedures are higher there. Cytotoxicity also proves to be extremely crucial as drugs could jeopardize human life without such tests.