In vitro and in vivo pharmacological characterization of SB 201993, an eicosanoid-like LTB4receptor antagonist with anti-inflammatory activity

Abstract Summary Leukotriene B 4 (LTB 4 ) and 12-(R)-hydroxy-5,8,10,14-eicosatetraenoic acid (12-[R]-HETE) have been postulated to contribute to the pathophysiology of inflammatory diseases. SB 201993, (E)-3 [[[[6-(2-carboxyethenyl)-5-[lsqb;8-(4-methoxyphenyl)octyl] oxy]-2-pyridinyl] methyl] thio] methyl] benzoic acid, identified from a chemical series designed as ring-fused analogs of LTB 4 , was evaluated as an antagonist of LTB 4 - and 12-(R)-HETE-induced responses in vitro and for anti-inflammatory activity in vivo. SB 201993 competitively antagonized ‘ 3 -H’-LTB 4 binding to intact human neutrophils (K i = 7.6 NM) and to membranes of RBL 2H3 cells expressing the LTB 4 receptor (RBL 2H3-LTB 4 R; IC 50 = 154 nM). This compound demonstrated competitive antagonism of LTB 4 - and 12-(R)-HETE-induced Ca 2+ mobilization responses in human neutrophils (IC 50 s of 131 nM and 105 nM, respectively) and inhibited LTB 4 -induced Ca 2+ mobilization in human cultured keratinocytes (IC 50 = 61 nM), RBL 2H3-LTB 4 R cells (IC 50 = 255 nM) and mouse neutrophils (IC 50 = 410 nM). SB 201993 showed weak LTD 4 -receptor binding affinity (K i = 1.9 μM) and inhibited 5-lipoxygenase (IC 50 of 3.6 mM), both in vitro and ex vivo. In vivo, SB 201993 inhibited LTB 4 -induced neutrophil infiltration in mouse skin and produced dose-related, long lasting topical anti-inflammatory activity against the fluid and cellular phases of arachidonic acid-induced mouse ear inflammation (ED 50 of 580 μg/ear and 390 μg/ear, respectively). Similarly, anti-inflammatory activity was also observed in the murine phorbol ester-induced cutaneous inflammation model (ED 50 of 770 and 730 mg/ear, respectively, against the fluid and cellular phases). These results indicate that SB 201993 blocks the actions of LTB 4 and 12-(R)-HETE and inhibits a variety of inflammatory responses; and thus may be a useful compound to evaluate the role of these mediators in disease models.