Abstract
CP-195543 [(+)-2-(3-benzyl-4-hydroxy-chroman-7-yl)-4-trifluoromethyl-benzoic acid] is a structurally novel, selective and potent leukotriene B4 (LTB4) receptor antagonist. In vitro CP-195543 inhibited [3H]LTB4binding to high-affinity LTB4 receptors on human neutrophils (HN) and murine spleen membranes with IC50values of 6.8 nM (Ki = 4.9 nM) and 37.0 nM (Ki = 26.9 nM), respectively. CP-195543 inhibited human and mouse neutrophil chemotaxis mediated by LTB4 with IC50 values of 2.4 nM and 7.5 nM, respectively. Evidence of noncompetitive antagonist effects on the HN high-affinity LTB4 receptor was obtained by Scatchard analysis of [3H]LTB4 binding to and chemotaxis of HN to LTB4. Scatchard analyses of [3H]LTB4 binding to low-affinity receptors on HN indicated that CP-195543 acted as a competitive antagonist at this receptor, and inhibition of LTB4-mediated CD11b up-regulation on HN was inhibited competitively by CP-195543 (pA2 = 7.66). In whole blood, CP-195543 also blocked CD11b up-regulation on HN (pA2 = 7.12) and murine neutrophils (pA2 = 7.06) with a similar potency. LTB4-mediated CD11b up-regulation on human monocytes and eosinophils in whole blood were inhibited by CP-195543 with IC50 values of 270 nM and 420 nM, respectively. CP-195543 at 10 μM failed to inhibit HN chemotaxis and CD11b up-regulation mediated through alternative (i.e., complement fragment 5a, interleukin-8, platelet-activating factor) G-protein-coupled chemotactic factor receptors. In vivo, after oral administration, CP-195543 blocked LTB4-mediated neutrophil infiltration in guinea pig and murine skin with ED50 values of 0.1 mg/kg and 2.8 mg/kg p.o., respectively. When administered in osmotic pumps, CP-195543 reduced the clinical symptoms and attendant weight loss in an IL-1-exacerbated murine model of collagen-induced arthritis with half-maximal effects associated with plasma drug levels of 0.4 to 0.5 μg/ml. Collectively these data provide evidence of thein vitro potency and in vivo efficacy of a novel LTB4 antagonist and support its clinical evaluation in a variety of inflammatory diseases in man.
Footnotes
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Send reprint requests to: Henry J. Showell, Department of Cancer, Immunology and Infectious Diseases, Central Research Division, Pfizer Inc., Groton, CT 06340.
- Abbreviations:
- LTB4
- leukotriene B4, 5(S),12(R)-dihydroxy,6-cis,8,10-trans,14-cis-eicosatetraenoic acid
- 5-LO
- 5-lipoxygenase
- FLAP
- 5lipoxygenase-activating protein
- HN
- human neutrophil
- MN
- murine neutrophil
- MSM
- murine spleen membrane
- HM
- human monocyte
- HE
- human eosinophil
- IL-8
- interleukin 8
- MPO
- myeloperoxidase
- HEPES
- N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid
- EDTA
- ethylenediaminetetraacetic acid
- BSA
- bovine serum albumin
- HBSS
- Hanks’ balanced salt solution
- PBS
- phosphate-buffered saline
- FACS
- fluorescence-activated cell sorter
- Received October 21, 1997.
- Accepted February 5, 1998.
- The American Society for Pharmacology and Experimental Therapeutics
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