Biomolecules & Therapeutics

The Korean Society of Applied Pharmacology (한국응용약물학회)
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Proarrhythmic Risk Assessment of Sildenafil under High-Dose Misuse Conditions Using the Comprehensive In Vitro Proarrhythmia Assay (CiPA)

  • Hanbi Kim (Pharmacology and Narcotics Research Division, National Institute of Food and Drug Safety Evaluation, Ministry of Food and Drug Safety) ;
  • Tae Woong Na (Pharmacology and Narcotics Research Division, National Institute of Food and Drug Safety Evaluation, Ministry of Food and Drug Safety) ;
  • Inkyo Jung (Pharmacology and Narcotics Research Division, National Institute of Food and Drug Safety Evaluation, Ministry of Food and Drug Safety) ;
  • Minji Kang (Pharmacology and Narcotics Research Division, National Institute of Food and Drug Safety Evaluation, Ministry of Food and Drug Safety) ;
  • Sujeong Park (Pharmacology and Narcotics Research Division, National Institute of Food and Drug Safety Evaluation, Ministry of Food and Drug Safety) ;
  • Chan Hyeok Kwon (Pharmacology and Narcotics Research Division, National Institute of Food and Drug Safety Evaluation, Ministry of Food and Drug Safety) ;
  • Kikyung Jung (Pharmacology and Narcotics Research Division, National Institute of Food and Drug Safety Evaluation, Ministry of Food and Drug Safety)
  • Received : 2025.05.21
  • Accepted : 2026.02.10
  • Published : 2026.05.01
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Abstract

The comprehensive in vitro proarrhythmia assay (CiPA) initiative, led by the U.S. Food and Drug Administration (FDA), provides a framework for predicting drug-induced arrhythmia risk. To support domestic CiPA implementation, we evaluated the proarrhythmic risk of sildenafil, a phosphodiesterase type 5 (PDE5) inhibitor. Sildenafil has been misused recreationally, with reports of high-dose non-medical intake. To simulate misuse, in vitro assays were conducted using concentrations up to 100× the maximum therapeutic plasma concentration (Cmax). The assessment followed the three core components of the CiPA paradigm. Patch clamp assays were conducted in Human Embryonic Kidney 293 (HEK293) and Chinese hamster ovary (CHO) cells transiently expressing Nav1.5, Cav1.2, and hERG ion channels. In silico modeling was performed using the CiPAORdv1.0 model based on IC50 and Hill coefficient values. Functional evaluation included multi-electrode array (MEA) recordings in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), and in vivo electrocardiography (ECG) analysis in rats was performed to observe QT interval prolongation. Sildenafil significantly inhibited hERG currents by 40.5% at 100× Cmax. In silico modeling predicted a low Torsades de Pointes (TdP) risk based on qNet biomarkers. In contrast, MEA recordings showed a concentration-dependent prolongation of corrected field potential duration (FPDc), with a significant 13.3% increase at 100× Cmax. The TdP risk estimated from MEA modeling was 64%. In vivo ECG analysis revealed significant QT prolongation at 50× Cmax. Despite low in silico TdP predictions, functional assays suggest that high concentrations of sildenafil as in misuse may pose a clinically relevant risk of QT prolongation and arrhythmia.

Keywords

Acknowledgement

This research was supported by a grant (23211MFDS219) from the Ministry of Food and Drug Safety in 2023–2024.

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