Angiotensin II Receptor Antagonists : Candesartan Cilexetil

Blockade of the action of angiotensin II (AII) has long been a target for the development of novel antihypertensive agents. We recently discovered a novel class of potent nonpeptide AII receptor antagonists, benzimidazole-7-carboxylic acids including candesartan. Candesartan is a highly potent and insurmountable AII type-1 receptor (AT1)-selective antagonist. Structure-activity relationship (SAR) studies revealed that the adjacent arrangement of a lipophilic substituent, a tetrazolylbiphenylmethyl moiety and a carboxyl group was the important structural requirement for potent AII antagonistic activity. Especially, the presence of a carboxyl group at the 7-position was found to be essential for insurmountable antagonism. To improve bioavailability of candesartan, chemical modification was examined to yield candesartan cilexetil, a prodrug of candesartan. Candesartan cilexetil is a potent and long-acting blocker that, when given once a day to patients, provides effective 24 hr blood pressure control.