Modelling adverse drug reactions using induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs)

Adverse drug reactions (ADRs) constitute the fourth leading cause of death and their incidence is steadily increasing. Cardiovascular toxicity is one of the most common and serious ADR and is the leading cause of drug discontinuation. The overarching goal of this thesis is to investigate cardiac ADRs using human pluripotent stem cell derived cardiomyocytes (hPSC-CMs). Doxorubicin is a chemotherapy drug administered to adult and pediatric patients for the treatment of hematological and solid tumors, however, it can cause doxorubicin induced cardiotoxicity (DIC). We generated induced pluripotent stem cell derived cardiomyocytes (iPSC-CMs) from patients who received doxorubicin as part of their chemotherapy regimen. iPSC-CMs from individuals who developed DIC displayed significantly greater sensitivity to doxorubicin compared to iPSC-CMs from patients who did not experience DIC. Several variants associated with DIC have been identified, with RARG –S427L having the strongest genetic evidence. iPSC-CMs together with genome editing, provide a powerful platform to establish causal relationships between genetic variants and ADRs. We used CRISPR/Cas9 to investigate the functional impact of RARG-S427L on DIC in isogenic patient derived iPSC-CMs that differed only at the RARG locus. Genetic correction of RARG-S427L decreased susceptibility to in vitro DIC, whereas introduction of RARG-S427L had the opposite effect. We also used this platform to identify novel cardioprotectants that can be used clinically to prevent DIC. Empagliflozin, a sodium-glucose co-transporter 2 inhibitor, is an FDA-approved medication for the treatment of diabetes that shows cardiovascular benefits. iPSC-CMs treated with empagliflozin exhibited reduced doxorubicin induced cell death. Finally, we showed that enriched cardiomyocyte subtype populations are necessary for accurate drug screening and disease modelling. Ibrutinib is an anticancer drug indicated for the treatment of B cell malignancies; however, it can cause atrial fibrillation. We used atrial and ventricular hPSC-CMs to study ibrutinib induced atrial fibrillation. Ibrutinib had an arrhythmogenic impact on hPSC atrial derived cardiomyocytes, while ventricular hPSC remained unaffected. Collectively, our findings demonstrate that hPSC-CMs represent a powerful platform for disease modelling and drug screening that is amenable to personalized risk prediction for the prevention of adverse drug reactions.Medicine, Faculty ofExperimental Medicine, Division ofGraduat

Ibrutinib Displays Atrial-Specific Toxicity in Human Stem Cell-Derived Cardiomyocytes

Summary: Ibrutinib (IB) is an oral Bruton's tyrosine kinase (BTK) inhibitor that has demonstrated benefit in B cell cancers, but is associated with a dramatic increase in atrial fibrillation (AF). We employed cell-specific differentiation protocols and optical mapping to investigate the effects of IB and other tyrosine kinase inhibitors (TKIs) on the voltage and calcium transients of atrial and ventricular human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs). IB demonstrated direct cell-specific effects on atrial hPSC-CMs that would be predicted to predispose to AF. Second-generation BTK inhibitors did not have the same effect. Furthermore, IB exposure was associated with differential chamber-specific regulation of a number of regulatory pathways including the receptor tyrosine kinase pathway, which may be implicated in the pathogenesis of AF. Our study is the first to demonstrate cell-type-specific toxicity in hPSC-derived atrial and ventricular cardiomyocytes, which reliably reproduces the clinical cardiotoxicity observed. : The authors employ cell-specific cardiac differentiation protocols, RNA-seq, and optical mapping to demonstrate atrial-specific toxicity of ibrutinib, a first-in-class BTK inhibitor. Other tyrosine kinase inhibitors (TKIs) with the same drug target do not affect atrial electrophysiology. Nilotinib and vandetanib, two TKIs known to be associated with QT prolongation and risk of sudden death, demonstrated ventricular-specific electrophysiologic dysregulation. Keywords: cardiac electrophysiology, tyrosine kinase inhibitors, atrial fibrillation, drug screening, optical mapping, RNA-se