In vitro antagonistic properties of a new angiotensin type 1 receptor blocker, azilsartan, in receptor binding and function studies.
The angiotensin II (AII) antagonistic action of azilsartan (AZL) [2-ethoxy-1-{[2'-(5-oxo-4,5-dihydro-1,2,4-oxadiazol-3-yl)biphenyl-4-yl]methyl}-1H-benzimidazole-7-carboxylic acid] was investigated in radioligand binding and function studies. AZL inhibited the specific binding of ¹²⁵I-Sar¹-Ile⁸-AII to human angiotensin type 1 receptors with an IC₅₀ of 2.6 nM. The inhibitory effect of AZL persisted after washout of the free compound (IC(50) value of 7.4 nM). Olmesartan, telmisartan, valsartan, and irbesartan also inhibited the specific binding with IC₅₀ values of 6.7, 5.1, 44.9, and 15.8 nM, respectively. However, their inhibitory effects were markedly attenuated with washout (IC₅₀ values of 242.5, 191.6, >10,000, and >10,000 nM). AZL also inhibited the accumulation of AII-induced inositol 1-phosphate (IP1) in the cell-based assay with an IC₅₀ value of 9.2 nmol; this effect was resistant to washout (IC₅₀ value of 81.3 nM). Olmesartan and valsartan inhibited IP1 accumulation with IC₅₀ values of 12.2 and 59.8 nM, respectively. The activities of these compounds were markedly reduced after washout (IC₅₀ value of 908.5 and 22,664.4 nM). AZL was defined as an inverse agonist in an experiment by using a constitutively active mutant of human angiotensin type 1 receptors. In isolated rabbit aortic strips, AZL reduced the maximal contractile response to AII with a pD'₂ value of 9.9. The inhibitory effects of AZL on contractile responses induced by AII persisted after the strips were washed; these inhibitory effects were more potent than those of olmesartan. These results suggest that AZL is a highly potent and slowly dissociating AII receptor blocker. Its tight receptor binding might be expected to produce potent and long-lasting antihypertensive effects in preclinical and clinical settings.
Pharmacology Research Laboratories, Pharmaceutical Research Division, Takeda Pharmaceutical Company, Ltd., Osaka, Japan. kusumoto_keiji@takeda.co.jp
Mami
M
Ojima
Hideki
H
Igata
Masayuki
M
Tanaka
Hiroki
H
Sakamoto
Takanobu
T
Kuroita
Yasuhisa
Y
Kohara
Keiji
K
Kubo
Hiromitsu
H
Fuse
Yoshimi
Y
Imura
Keiji
K
Kusumoto
Hideaki
H
Nagaya
D047228:Angiotensin II Type 1 Receptor Blockers / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism; D001562:Benzimidazoles / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D019556:COS Cells; D002522:Chlorocebus aethiops; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008297:Male; D010069:Oxadiazoles / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D011485:Protein Binding / Q000502:physiology; D011817:Rabbits; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism* / Q000502:physiology
D047228:Angiotensin II Type 1 Receptor Blockers; D001562:Benzimidazoles; D010069:Oxadiazoles; D044140:Receptor, Angiotensin, Type 1; C521273:azilsartan