Abstract
Cell-based assays are essential for drug discovery and development as they increase the quality of lead
compounds due to their physiological relevance. Toxicological data can be gathered during the early phases
of hit selection and verification, reducing costs and attrition rates during clinical trials.
Amongst the various cell-based assays that are currently being used, high content screening (HCS) has
enjoyed particular interest and is now widely considered as an essential tool for the drug discovery and
development industry and is implemented at every step of the process. This powerful technology is used for
target validation1,2, primary screening3, secondary screening4, structure-activity relationship studies5,6 and
ADMET (adsorption, distribution, metabolism, excretion and toxicity) studies7. Several factors have
contributed to the success of HCS.
Firstly, it is arguably the cell-based assay that can yield the most data due to the richness of information
contained in the images. Thus, not only quantitative information such as intensity or number of structures
can be obtained, but also descriptive qualifiers, such as size, morphology and texture of objects. Secondly, it
is one of the few technologies that can measure spatial data, allowing the assay of translocations events and
distribution of objects in regards to each other or to other objects (i.e. vesicle clustering or vesicle distance to
plasma membrane). Thirdly, due to the analytical power of modern image analysis, subpopulations can be
analysed, making HCS a very sensitive technique, allowing a person to screen for rare events. Lastly, due to
the multiplexing capability of HCS, toxicity can be directly assayed by using appropriate markers, instead of
being indirectly inferred by reduced cell numbers. Also, several parameters can be screened in parallel,
allowing for screening and counter-screening to be performed in a single assay. All these properties facilitate
the decision-making process during hit prioritisation and lead development.
In recent years, live cell imaging has emerged as a new trend in HCS and most vendors of HCS readers now
offer versions with incubation chambers and environmental control. Live cell imaging adds a further level of
complexity to HCS and poses many new technological challenges. This article will review some of the
advantages and challenges of kinetic HCS and discuss future directions.
