Embryotoxicity analysis of anti-arrhythmia drugs amiodarone, dronedarone, and their metabolites using 3D gastruloid models.

Amiodarone and dronedarone are anti-arrhythmic drugs that are structurally related but differ in iodine content. Although contraindicated during pregnancy due to suspected embryotoxicity based on animal studies, their mechanisms of action and relevance to human development remain unclear. Here, we used gastruloids - 3D aggregates of mouse or human pluripotent stem cells that recapitulate axial elongation morphogenesis of early embryos - to investigate their developmental effects. In mouse gastruloids, both drugs and their major metabolites impaired growth and elongation at 1.5 - 3.0 µM. They also altered expression of genes involved in somite segmentation and retinoic acid biosynthesis. Notably, dronedarone down-regulated additional genes, and only amiodarone's morphological effects were alleviated by retinoic acid supplementation, suggesting distinct mechanisms of action. In human gastruloids, dronedarone induced abnormal convoluted morphology and disrupted gene expression at concentrations as low as 0.05 µM, whereas amiodarone showed effects at 2.0 µM, indicating greater sensitivity of the human model to dronedarone. Transcriptomic analyses revealed both overlapping and distinct gene expression changes between the two drugs. These results demonstrate that gastruloid-based assays can detect adverse effects of amiodarone and dronedarone at clinically relevant concentrations, as therapeutic plasma levels are approximately 1.3 - 2.6 µM for amiodarone and 0.15 - 0.30 µM for dronedarone. The study also provided mechanistic and human-relevant insights not attainable through traditional animal testing. Our findings underscore the utility of stem cell-based models for assessing human developmental toxicity, and support their use in evaluating safer alternatives for anti-arrhythmic therapy during pregnancy.