Apoptosis assays for quantifying the bioactivity of anticancer drug products

The goal of cancer therapy is to kill cancer cells. Many anticancer drugs are designed to kill cells by inducing apoptosis. However, the potency assays used for measuring the bioactivity of these products are generally cell viability assays which do not distinguish between cell death and growth inhibition. There are a number of commercial assays available to measure apoptosis; however, many of these assays are not appropriate for use in high-throughput screening formats preferred by industry to measure drug activity, also known as potency, due to their inherent low robustness and/or high variability. This review outlines the strengths and weaknesses of current apoptosis assays and highlights new promising assay developments for evaluation of anticancer therapeutics, such as the design of fluorescent and luminescent constructs to be applied as caspase substrates.