bwa-4c and Bronchial-Diseases

Inhibition of 5-lipoxygenase (5-LO) is a potential target for therapeutic intervention in asthma. Acetohydroxamic acids such as BW A4C are potent and selective 5-LO inhibitors in vitro and also inhibit 5-LO activity in vivo following oral administration. In man, BW A4C is metabolised relatively rapidly (t1/2 = approx. 2h) but nevertheless inhibits 5-LO with reasonable persistence. Chemical modification of BW A4C has resulted in compounds, including the alpha-methyl analogues BW B218C and BW A360C and the hydroxyurea BW B70C, that retain high in vitro potency as selective 5-LO inhibitors and, compared to BW A4C, have a higher potency and longer duration of action in vivo. Members of both the hydroxamic acid and hydroxyurea series of 5-LO inhibitors are presently being considered as potential anti-asthma drugs.

Topics: Anaphylaxis; Animals; Asthma; Benzeneacetamides; Bronchial Diseases; Guinea Pigs; Humans; Hydroxamic Acids; Hydroxyurea; Lipoxygenase Inhibitors

1. The effect of a novel series of orally-active acetohydroxamic acid inhibitors of arachidonate 5-lipoxygenase on 'leukotriene-dependent' anaphylactic bronchoconstriction has been investigated in anaesthetized, pump-ventilated guinea-pigs actively sensitized to ovalbumin (OA). In a complementary series of experiments, the pharmacokinetics of these compounds in the plasma compartment following oral administration to guinea-pigs has also been investigated. 2. In animals pretreated with mepyramine (2 mg kg-1, i.v.) and indomethacin (10 mg kg-1, i.v.) and challenged with antigen aerosol (OA 10 mg ml-1; 5 s) compounds BW A4C, BW A137C and BW A797C (10-200 mg kg-1, p.o., 1 h pre-challenge) markedly reduced that component of anaphylactic bronchoconstriction shown to be 'leukotriene-dependent'. 3. The maximum degree of inhibition (up to 75%) of 'leukotriene-dependent' anaphylactic bronchoconstriction by these three compounds was equivalent to that seen with the leukotriene antagonist FPL 55712 (10 mg kg-1, i.v.). 4. The peak levels of unchanged acetohydroxamic acids in the plasma compartment occurred 0.5 h after their oral administration and were as follows: BW A4C: 11.3 +/- 3.9; BW A137C: 7.6 +/- 2.4; BW A797C: 3.9 +/- 1.3 micrograms ml-1 plasma. 5. The inhibition by BW A4C and BW A137C (50 mg kg-1, p.o.) of 'leukotriene-dependent' anaphylactic bronchospasm persisted for up to 3 and 4 h respectively but did not extend to 6 h. The decline in inhibitory activity paralleled the fall in the concentration of unchanged drug in the plasma compartment over this time period. 6. The results of the present study are consistent with BW A4C, BW A137C and BW A797C attenuating 'leukotriene-dependent' bronchial anaphylaxis in anaesthetized guinea-pigs by selective inhibition of arachidonate 5-lipoxygenase.

Topics: Anaphylaxis; Animals; Arachidonate Lipoxygenases; Benzeneacetamides; Bronchial Diseases; Guinea Pigs; Hydroxamic Acids; Lipoxygenase Inhibitors; Male