There are many reason for conducting cell based assays. You might want to find out if a chemical or material is cytotoxic, meaning that it is toxic to cells. Another reason for conducting cell based assays is to ensure that a biological product is manufactured appropriately. Biological products often have multiple functional domains that might interact with several different molecules in order to function appropriately. For example, a protein product might have a functional domain that allows for the product to be internalized into the cell, a domain that allows it to move to the nucleus and another domain that allows it to activate a transcription factor. All these functional domains must be tested before the batch of product is released. Sometimes these functional domains must be done in a living organism, but in most cases the biological activity of protein product can be tested using a cell based assay.
Cell based assays are defined as any assay that takes place within a living cell. Because this definition is so general, there are thousands of different cell based assays. However, cell based assays can be grouped into categories such as cell proliferation assays, cell death assays, reporter gene assays, and cell signaling assays. A description of these assays can be found in PBL’s testing webpage titled In Vitro Potency Assays.
In a regulatory setting, cell based assays are commonly used for cytotoxicity testing, to determine the biological activity (potency) of drug product and drug substance, to determine the mechanism of action (MOA), early stage proof of principal studies, and in immunogenicity studies to determine if antibodies produced by the patient are neutralizing the drug product.