Direct inhibition of 5-LO, partly through an iron-catalysed
redox mechanism, has been achieved with compounds
such as benzofurans (L-670,630 and L-650,224),
hydroxamates (BWA4C), N-hydroxyurea derivatives (A-
64077 or zileuton) and indazolinones (ICI 207,968), with
good selectivity and potency [49]. ICI 207,968 and
BWA4C, which are orally active, produced dose-dependent
inhibition of the cysteinyl-leukotriene component
of antigen-induced bronchoconstriction in sensitized
guinea-pigs [50]. BWA4C also exhibited ex-vivo LTB4
synthesis when dosed orally to volunteers. Zileuton had
similar in vitro potency and selectivity to acetohydroxamates
and inhibited leukotriene synthesis ex-vivo [49].
Zileuton inhibited airway microvascular leakage and
bronchoconstriction induced by inhaled allergen in the
sensitized guinea-pig model [51], in addition to inhibiting
leucocyte accumulation [51, 52]. Zileuton produced
dose-dependent inhibition of leukotriene synthesis exvivo
following oral administration to volunteers, with a
duration of action of 6 h at doses of 600–800 mg [53].
Direct inhibition of 5-LO, partly through an iron-catalysed
redox mechanism, has been achieved with compounds
such as benzofurans (L-670,630 and L-650,224),
hydroxamates (BWA4C), N-hydroxyurea derivatives (A-
64077 or zileuton) and indazolinones (ICI 207,968), with
good selectivity and potency [49]. ICI 207,968 and
BWA4C, which are orally active, produced dose-dependent
inhibition of the cysteinyl-leukotriene component
of antigen-induced bronchoconstriction in sensitized
guinea-pigs [50]. BWA4C also exhibited ex-vivo LTB4
synthesis when dosed orally to volunteers. Zileuton had
similar in vitro potency and selectivity to acetohydroxamates
and inhibited leukotriene synthesis ex-vivo [49].
Zileuton inhibited airway microvascular leakage and
bronchoconstriction induced by inhaled allergen in the
sensitized guinea-pig model [51], in addition to inhibiting
leucocyte accumulation [51, 52]. Zileuton produced
dose-dependent inhibition of leukotriene synthesis exvivo
following oral administration to volunteers, with a
duration of action of 6 h at doses of 600–800 mg [53].
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