Key result
Amiodarone analogues such as B2-O-CH(2)-CH(2)-N-piperidine demonstrated significantly less cytotoxicity and higher affinity towards hERG channels compared to the parent compound amiodarone.
Amiodarone analogues can be synthesized to retain or improve hERG channel inhibition while reducing cytotoxicity, demonstrating these properties are mechanistically distinct.
Amiodarone analogues may enable safer hERG inhibition; leaves open clinical translation in arrhythmia management.
BACKGROUND AND PURPOSE: Amiodarone (2-n-butyl-3-[3,5 diiodo-4-diethylaminoethoxybenzoyl]-benzofuran, B2-O-CH(2)CH(2)-N-diethyl) is an effective class III antiarrhythmic drug demonstrating potentially life-threatening organ toxicity. The principal aim of the study was to find amiodarone analogues that retained human ether-a-go-go-related protein (hERG) channel inhibition but with reduced cytotoxicity. EXPERIMENTAL APPROACH: We synthesized amiodarone analogues with or without a positively ionizable nitrogen in the phenolic side chain. The cytotoxic properties of the compounds were evaluated using HepG2 (a hepatocyte cell line) and A549 cells (a pneumocyte line). Interactions of all compounds with the hERG channel were measured using pharmacological and in silico methods. KEY RESULTS: Compared with amiodarone, which displayed only a weak cytotoxicity, the mono- and bis-desethylated metabolites, the further degraded alcohol (B2-O-CH(2)-CH(2)-OH), the corresponding acid (B2-O-CH(2)-COOH) and, finally, the newly synthesized B2-O-CH(2)-CH(2)-N-pyrrolidine were equally or more toxic. Conversely, structural analogues such as the B2-O-CH(2)-CH(2)-N-diisopropyl and the B2-O-CH(2)-CH(2)-N-piperidine were significantly less toxic than amiodarone. Cytotoxicity was associated with a drop in the mitochondrial membrane potential, suggesting mitochondrial involvement. Pharmacological and in silico investigations concerning the interactions of these compounds with the hERG channel revealed that compounds carrying a basic nitrogen in the side chain display a much higher affinity than those lacking such a group. Specifically, B2-O-CH(2)-CH(2)-N-piperidine and B2-O-CH(2)-CH(2)-N-pyrrolidine revealed a higher affinity towards hERG channels than amiodarone. CONCLUSIONS AND IMPLICATIONS: Amiodarone analogues with better hERG channel inhibition and cytotoxicity profiles than the parent compound have been identified, demonstrating that cytotoxicity and hERG channel interaction are mechanistically distinct and separable properties of the compounds.
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Waldhauser et al. (2008) studied this question. Amiodarone analogues vs. Amiodarone was evaluated on Cytotoxicity and hERG channel inhibition. Amiodarone analogues such as B2-O-CH(2)-CH(2)-N-piperidine demonstrated significantly less cytotoxicity and higher affinity towards hERG channels compared to the parent compound amiodarone.
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