Cardiovascular Profile of Xanthone-Based 1,4 Dihydropyridines Bearing a Lidoflazine Pharmacophore Fragment.

As a follow-up to our previous studies on differently substituted 1,4-dihydropyridines endowed with a peculiar cardiac selectivity, in this paper, a small series of hybrid compounds bearing the pharmacophore fragment of lidoflazine in position 2 or 3 on a 4-(xanthen-9-one)-dihydropyridine core was reported. Lidoflazine was selected due to our promising previously reported data, and the xanthen-9-one substituent was introduced in position 4 of the dihydropyridine scaffold based on the cardiac selectivity observed in several of our studies. The new hybrid compounds were tested to assess cardiac and vascular activities, and the data were evaluated in comparison with those previously obtained for 4-(xanthen-9-one)-dihydropyridines and lidoflazine⁻nifedipine hybrid compounds. The functional studies indicated an interesting peculiar selectivity for the cardiac parameter inotropy, in particular when the lidoflazine fragment was introduced in position 2 of the dihydropyridine scaffold (4a⁻e), and thus a possible preferential binding with the Cav 1.2 isoform of l-type calcium channels, which are mainly involved in cardiac contractility.

Lidoflazine is a high affinity blocker of the HERG K(+)channel.

Lidoflazine is an antianginal calcium channel blocker that carries a significant risk of QT interval prolongation and ventricular arrhythmia. We investigated whether or not lidoflazine inhibits current through the rapid delayed rectifier K(+) channel alpha subunit (encoded by HERG - human ether-a-go-go-related gene), since this channel has been widely linked to drug-induced QT-prolongation. Lidoflazine inhibited potently HERG current (I(HERG)) recorded from HEK 293 cells stably expressing wild-type HERG (IC(50) of approximately 16 nM). It was approximately 13-fold more potent against HERG than was verapamil under similar conditions. On membrane depolarization, I(HERG) inhibition developed gradually, ruling out closed-channel state dependent inhibition. The effect of command voltage on the drug's action suggested that lidoflazine preferentially inhibits activated/open HERG channels. The S6 mutation Y652A largely eliminated the inhibitory action of lidoflazine, whilst the F656A mutation also reduced blocking potency. We conclude: first, that lidoflazine produces high affinity blockade of the alpha subunit of the HERG channel by binding to aromatic amino acid residues within the channel pore and, second, that this is likely to represent the molecular mechanism of QT interval prolongation by this drug.

1,4-Dihydropyridines bearing a pharmacophoric fragment of lidoflazine.

A series of 1,4-dihydropyridines bearing a pharmacophoric fragment of lidoflazine was synthesized. The compounds were evaluated for inotropic, chronotropic, and calcium antagonist activities. All compounds behave as inotropic and chronotropic agents, except for compounds 4b, 5a, and 5b, which exhibit a rather weak calcium antagonism in vascular smooth muscle (like aorta). Compound 5b is about twofold more potent in decreasing both chronotropy and inotropy, while compound 5c is about fivefold more potent in decreasing inotropy than nifedipine. Moreover, compound 5b is the most potent calcium antagonist derivative of the series.