Computationally-informed point of departure evaluation for proarrhythmic cardiotoxicity assessment using 3D engineered cardiac microtissues from human iPSC-derived cardiomyocytes

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are
a promising new approach for in vitro proarrhythmic cardiotoxicity
assessment. However, variation due to differentiation batch, individual
sample variation, and non-linear responses to test drugs complicate
prediction of proarrhythmic drug concentrations. This study combines a
computational human action potential (AP) model of hERG channel block with
experimental data from three-dimensional hiPSC-CM engineered microtissues
to optimize point of departure (POD) estimation of drug-induced
prolongation of AP duration (APD). Computer simulations predicted that APD
prolongation from hERG block follows a logistic curve and that >81%
hERG block induced early afterdepolarizations (EADs) which significantly
shifted the APD response curve. Curve fitting of APD response by logistic,
bilinear breakpoint, and maximal curvature was more accurate prior to EAD
onset. Goodness-of-fit testing indicated that logistic regression with ≥6
test concentrations was sufficient to accurately estimate PODs. Power
analysis, based on experimental variations between batches (n=14), molds
(n=57), and microtissues (n=1701) predicted that PODs from 2~3 batches
with 10 microtissues per mold using a 5% threshold for APD prolongation
detected proarrhythmic cardiotoxicity with a negligible false positive
rate. We then applied this POD analysis to hiPSC‑CM microtissue data after
treatment with well characterized drugs (i.e., cisapride, ranolazine,
quinidine, and verapamil). Using bootstrapping, we estimated PODs and
confidence intervals that matched concentrations known to cause
proarrhythmic effects in patients. This study identified a robust method
for calculating PODs for proarrhythmic cardiotoxicity risk in vitro and
developed a framework for experimental design in this and other in vitro
platforms.