Synthesis and structure-activity relationships of new 1, 3-disubstituted cyclohexanes as structurally rigid leukotriene B(4) receptor antagonists.

A series of 1-hydroxy-3-¿3-hydroxy-7-phenyl-1-hepten-1-yl cyclohexane acetic acid derivatives was designed based on postulated active conformation of leukotriene B(4) (LTB(4)) and evaluated as human cell surface LTB(4) receptor (BLTR) antagonists. Binding was determined through ¿(3)HLTB(4) displacement from human neutrophils and receptor antagonistic assays by in vitro measurements of inhibition of leukocyte chemotaxis induced by LTB(4). On the basis of these assays, a structure-affinity relationship was investigated. Optimization of the acid chain length and omega-substitution of a phenyl group on the lipophilic tail were shown to be critical for binding activity. These modifications led to the discovery of compounds with submicromolar potency and selective BLTR antagonism. The most potent compound 3balpha (IC(50) = 250 nM) was found to significantly inhibit oedema formation in a topical model of phorbolester-induced inflammation. Substantial improvement of in vitro potency was achieved by modification of the carboxylic acid function leading to the identification of the N,N-dimethylamide series. Compound 5balpha, free of agonist activity, displayed higher potency in receptor binding with an IC(50) of 40 nM. These results support the hypothesis that the spatial relationship between the carboxylic acid and allylic hydroxyl functions is crucial for high binding affinity with BLTR.

Synthesis and biochemical/pharmacological profile of the novel leukotriene B4 receptor antagonist sodium (1S*, 3S*)-1-hydroxy-3-[(3 R*S*,E)-3-hydroxy-7-phenyl-1-hepten-1-yl]-1-cyclohexane acetate.

A novel series of leukotriene B4 (LTB4) antagonists is reported. These compounds present a cyclohexane ring in their chemical structure, which mimics the three conjugated double bonds of LTB4. The biochemical/pharmacological profile of the leader compound, PH-163 (sodium (1S*,3S*)-1-hydroxy-3-[(3R*S,E)-3-hydroxy-7-phenyl-1-hepten-1-yl]- 1 -cyclohexane acetate, CAS 163251-41-0) is described. This compound competes with [3H]LTB4 binding to its receptor in human neutrophils and guinea pig lung membranes with IC50's of 0.8 mumol/l and 0.2 mumol/l, respectively, i.e. relative binding affinities of 1% as compared to LTB4. PH-163 does not elicit any agonist activity, but inhibits leucocyte chemotaxis induced by LTB4 (pKB = 6.57) and lung parenchymal strip contraction (IC50 = 0.1 mumol/l). In conclusion, PH-163 or derivatives could be useful in the treatment of inflammatory diseases where LTB4 seems to be involved.