Reporter assay systems are suitable for the multi-parameter phenotype screening of drug candidates [21] . In contrast to the single molecular target approach, cell-based reporter assays reflect the complexity of the living organism. Therefore, they are becoming widely used to screen the effects of small molecules on signaling pathways [22] . However, drug discovery by HTS in cell-based assays presents its own difficulties. For instance, isolation of a hit compound often does not suggest a single, particular molecular target, preventing further optimization of hit compounds by medicinal chemistry [23] . This has led to cell-based screens being termed 'black-box' screens [21] . However, in most cases, target pathways may be predicted and investigated further. Nonetheless, drug companies prefer the well-characterized molecular target approach rather than phenotypic screening to accelerate the early phase of drug development. In fact, cell-based screens tend to identify more false positives than molecular target screens, presumably because of the existence of many potential targets in the biological pathway of interest [24] . Nonetheless, hit compounds from molecular target screens can fail to generate the expected effect on cells or have undesirable side effects that are potentially harmful to humans. In the context of the ongoing paradigm shift towards pathway-driven drug discovery, particularly in the academic field, it becomes increasingly important to accomplish promising candidate isolation earlier in the drug discovery pipeline and with higher throughput. Currently, many large pharmaceutical companies have established open innovation research programs through collaboration with non-profit research organizations to overcome these problems. Academic research teams typically utilize cell-based reporter assay systems for primary drug screening. Furthermore, research is also being conducted using living animals to monitor the more complex dynamics of the hit compounds identified by screening.