Abstract
Ro 24-5913, (E)-4-[3-[2-(4-cyclobutyl-2- thiazolyl)ethenyl]phenylamino]-2,2-diethyl-4-oxobutanoic acid, has been identified as a chemically unique, potent and selective LTD4 antagonist. In vitro, Ro 24-5913 competes with [3H]LTD4 for its binding site on guinea pig lung membranes with an IC50 of 6.4 +/- 2.2 nM. In isolated guinea pig tracheal smooth muscle, Ro 24-5913 produces concentration-dependent rightward shifts of LTD4-induced contraction curves (pA2 value of 9.6 +/- 0.2). The slope of the Schild plot is not significantly different from 1, indicating that the antagonism is of a competitive nature. In the human bronchus, Ro 24-5913 is an effective antagonist of LTD4-induced contractions (pKB of 9.3 +/- 0.1). In vivo, Ro 24-5913 dose-dependently inhibits LTD4-induced bronchoconstriction in guinea pigs by the i.v. (ID50 0.13 mg/kg), oral (ID50 0.12 mg/kg) and aerosol (IC50 0.008%) routes of administration. This in vivo activity is specific as evidenced by the inability of Ro 24-5913 to inhibit bronchoconstriction induced by LTB4, PAF or histamine. In comparison with other LTD4 antagonists evaluated in this guinea pig model, Ro 24-5913 is markedly superior in terms of oral potency, bioavailability and oral duration of action. Ro 24-5913 also blocks allergic bronchospasm mediated by endogenously generated leukotrienes in guinea pigs; the potency and duration of action is nearly equivalent to that seen as an antagonist of bronchoconstrictions produced by exogenous LTD4. In summary, Ro 24-5913 is representative of a novel chemical class of LTD4 receptor antagonists.(ABSTRACT TRUNCATED AT 250 WORDS)
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|