LF 16.0335, a novel potent and selective nonpeptide antagonist of the human bradykinin B2 receptor

1. In the present paper, we describe the in vitro pharmacological properties of LF 16.0335 (1-[[3-[(2,4-dimethylquinolin-8-yl)oxymethyl]-2,4-dichloro-phenyl]sulphonyl] -2(S) - [[4 -[4-(aminoiminomethyl)phenylcarbonyl]piperazin-1-yl]carbonyl]pyrrolidine), a novel and potent nonpeptide antagonist of the human bradykinin (BK) B₂ receptor.
2. LF 16.0335 displaced [³H]-BK binding to membrane preparations from CHO cells expressing the cloned human B₂ receptor, INT 407 cells and human umbilical vein with K_i values of 0.84±0.39 nM, 1.26±0.68 nM and 2.34±0.36 nM, respectively.
3. In saturation binding studies performed in INT 407 cell membranes in the presence or absence of LF 16.0335, B_max values of [³H]-BK were not significantly changed suggesting that LF 16.0335 behaves as a competitive antagonist.
4. LF 16.0335 had no affinity for the cloned human kinin B₁ receptor stably expressed in 293 cells. In addition, this compound at 1 μM did not significantly bind to a range of 40 different membrane receptors and eight ion channels except muscarinic M₂ and M₁ receptors for which an IC₅₀ value of 0.9 and 1 μM was obtained.
5. BK stimulates in a concentration-dependent manner phosphoinositosides (IPs) production in cultured INT 407 cells. Concentration-response-curves to BK were shifted to the right in the presence of LF 16.0335 (0.1 μM) without reduction of the maximum. LF 16.0335 inhibited the concentration-contraction curve to BK in the human umbilical vein giving a pA₂ value of 8.30±0.30 with a Schild plot slope that was not different from unity.
6. These results demonstrate that LF 16.0335 is a potent, selective and competitive antagonist of the human bradykinin B₂ receptor.