TRIAZOLINONE BIPHENYLSULFONAMIDES AS ANGIOTENSIN-II RECEPTOR ANTAGONISTS WITH HIGH-AFFINITY FOR BOTH THE AT(1) AND AT(2) SUBTYPES

Angiotensin II (AII), the endogenous peptide Ligand of the AII receptor, has equivalent high affinity for both the AT(1) and AT(2) receptor subtypes while most of the reported nonpeptide AII antagonists are AT(1)-selective. In an effort to identify dual AT(1)/AT(2) nonpeptide AII antagonists, we have pursued modifications of previously prepared trisubstituted 1,2,4-triazolinone biphenylsulfonamides which exhibited subnanomolar in vitro AT(1) (rabbit aorta) AII antagonism and AT(2) (rat midbrain) IC50 values of <40 nM. Present results show that a suitable amide (or reversed amide) side chain appropriately positioned on the N-2-aryl group of these compounds gave >15-fold enhancement in AT(2) binding affinity without sacrificing nanomolar AT(1) potency (IC50). This added amide, combined with an appropriate choice of the N-substituent on the sulfonamide and the ortho substituent on the N-2-aryl group, led to an analogue (46, L-163,- 007) which exhibited subnanomolar AT(1) binding affinity and an AT(2)/AT(1) IC50 ratio of 3. This compound showed excellent iv activity at 1 mg/kg and oral efficacy at 3 mg/kg with >6 h duration in a conscious rat model. Available data suggest that the newly introduced amide side chain, mandatory for low nanomolar binding affinity at the AT(2) receptor, is well-tolerated by the AT(1) receptor and has minimal effect on the in vivo properties of these molecules.