Triplexes created by uniting the fluorescent viability and cytotoxicity multiplex with luminescent chemistries are advantageous for several reasons. First, it is possible to conduct immediate confirmation testing of apparent cytotoxic compounds in the same well by leveraging the statistical power of orthogonal detection of viability (viable cell aminopeptidase, dead cell protease and ATP biomarkers). The economy of this consolidated testing is noteworthy in terms of compound usage, culture set up, and operator man-hours. Second, the mechanism of cell death can often be elucidated when combined with caspase detection reagents, allowing for partial characterization of a compound's potential. It should be noted however, that caspase activity can be transient and immeasurable in long-term experiments due to the kinetics of apoptosis and caspase biomarker decay. Therefore, caspase-negative data sets should be rescreened at multiple compound exposure periods. This type of characterization of pathway dependent cytotoxicity is useful for continued annotation of a library, because compounds causing necrotic profiles at micromolar concentrations are rarely therapeutically useful and may offer unacceptable cytotoxic risk. And third, viability and cytotoxicity can be used to normalize luminescent data from other assays (Fig. 7) . Single parameter genetic reporter responses are susceptible to experimental variation due to differential transfection efficiencies, cell number delivered to the well (clumping) or to cytotoxicity caused by the test compound [55] . Viability and cytotox-icity data can therefore help reconcile aberrant data points or explain decreases in genetic reporter signals due to cell death.