Screening a phytochemical compound library for cardiotoxicity using human iPSC-derived cardiomyocytes

Abstract Drug-induced cardiotoxicity remains a major hurdle in drug development and one of the leading causes of post-marketing drug withdrawal. Traditional preclinical safety assays—based on animal models, isolated cardiac tissues, and heterologous ion-channel systems—often fail to predict human-specific cardiac liabilities due to interspecies differences in electrophysiology, metabolism, and contractile behavior. In this context, human induced pluripotent stem cell–derived cardiomyocytes (hiPSC-CMs) have emerged as a powerful alternative, offering a renewable, patient-specific, and mechanistically relevant model for cardiac safety assessment. The present thesis aimed to establish and apply a human-based, multiparametric in vitro platform combining hiPSC-CM monolayers on microelectrode arrays (MEA) with three-dimensional engineered heart tissues (EHTs) to identify and characterize mechanisms of drug-induced cardiotoxicity. A chemically diverse phytochemical compound library was screened for acute and chronic effects on cardiac electrophysiology, contractility, and cell viability. MEA recordings provided quantitative readouts of field potential duration, beat rate, amplitude, beat amplitude, excitation-contraction coupling and arrhythmic events, enabling sensitive detection of both proarrhythmic and conduction-altering compounds. Selected hits were subsequently validated in EHTs, a more mature 3D model, to assess whether electrophysiological alterations were accompanied by true contractile dysfunction. This integrated approach revealed several phytochemicals capable of modulating cardiac electrophysiology and contractile performance through distinct mechanisms, underscoring the value of combining electrophysiological, mechanical, and cytotoxicity endpoints within a unified screening framework. Importantly, comparison across different hiPSC-CM lines, including disease-specific genotypes, demonstrated the potential of this system for precision cardiac safety testing. Overall, the work presented in this thesis advances human-based cardiac safety pharmacology by establishing a scalable, translational platform that bridges early mechanistic screening and tissue-level validation. By reducing reliance on animal experiments and aligning with regulatory initiatives such as CiPA, it contributes to a more predictive and ethical paradigm for assessing cardiotoxic risk in drug discovery.