Ll. Chang et al., POTENT AND ORALLY-ACTIVE ANGIOTENSIN-II RECEPTOR ANTAGONISTS WITH EQUAL AFFINITY FOR HUMAN AT(1) AND AT(2) SUBTYPES, Journal of medicinal chemistry, 38(19), 1995, pp. 3741-3758
In order to block the effects induced by the interactions between angi
otensin II (AII) and both AT(1) and AT(2) receptors, we have pursued t
he discovery of orally active non-peptide AII antagonists that exhibit
potent and equal affinity for human AT(1) and AT(2) receptor subtypes
. A series of previously prepared nanomolar (IC50) trisubstituted 1,2,
4-triazolinone biphenyl-sulfonamide dual-acting AII antagonists has be
en modified at five different positions in order to increase AT(2) bin
ding affinity, maintain AT(1) activity, and reduce the human adrenal A
T(2)/AT(1) potency ratio (IC50 ratio) from greater than or equal to 10
. The targeted human adrenal potency ratio of less than or equal to 1
was achieved with a number of compounds possessing an ethyl group at C
-5 of the triazolinone and a 3-fluoro substituent at the N-4-biarylmet
hyl moiety. The most favored of these was compound 44 which exhibited
subnanomolar potency at both the AT(1) (rabbit aorta) and AT(2) (rat m
idbrain) receptors, with a slight preference for the latter, and had a
human adrenal AT(2)/AT(1) IC50 ratio of 1. This tert-butyl sulfonylca
rbamate with an N-2-[2-bromo-5-(valerylamino)phenyl] substituent had e
xcellent iv activity at 1 mg/kg (100% peak inhibition, greater than or
equal to 4 h duration of action) and is orally active at 3 mg/kg with
>6 h duration of action in a conscious rat model. The present study s
hows that the NH of the amide on the N-2-aryl moiety is not required f
or subnanomolar binding affinity to either receptor subtype, although
a keto functionality at this position is essential for acceptable AT(2
) binding. Receptor-ligand binding interactions derived from the struc
ture-activity relationships are discussed with respect to both recepto
r subtypes.