Abstract The overall objective of this study is to develop a novel, predictive in vitro platform for studying physiological responses of endothelium mediated human cardiomyocytes toxicity to therapeutics.  The proposed effort specifically responds to NHLBI Small Business Topics of Special Interest HLS18-08.  A critical in vivo component lacking in conventional models used for cardiac toxicity is the absence of endothelial cells and perivascular cells in communication with cardiomyocytes thereby limiting realistic predictions.  We propose to develop and demonstrate iPSCs-based microfluidic device and assay that will accurately reproduce the physiological conditions of vascular and cardiac tissue interactions observed in vivo.  Phase I will culminate with a clear demonstration of endothelium mediated toxicity screening with physiological relevant modulation of cardiomyocytes and endothelial cells caused by drug-induced interactions.  During Phase II, we will expand the platform further with culture of perivascular cells, and perform toxicity screening with clinically relevant drugs followed by in vivo validation.  We will also develop a framework for high throughput assays by integration with micro well plates.  A multi-disciplinary, partnership with expertise in microfluidics cell-based assays, iPSC-based cardiomyocytes, native extracellular matrices, regenerative medicine and cardiac toxicity with clinical relevance has been assembled to successfully meet the research objectives.  The end-product will be commercialized to researchers in industry and academia engaged in drug discovery and drug delivery.  The developed assay will also have critical applications in basic research, where it can be used to identify molecular mechanisms and in drug discovery for development of therapeutics.