Abstract
We evaluated the airway activity of the novel phosphodiesterase type 4 inhibitor SB 207499 [Ariflo;c-4-cyano-4-(3-cyclopentyloxy-4-methoxyphenyl-r-1-cyclohexane carboxylic acid)], in the guinea pig. Ovalbumin (OA)-induced contractions of guinea pig isolated tracheal strips were inhibited by SB 207499 with an EC50 of 1 μM but had little or no effect on exogenous agonist-induced contraction, which suggests that its effect on OA-induced contraction in vitro is primarily due to inhibition of mediator release from mast cells. In anesthetized guinea pigs, SB 207499 inhibited OA-induced bronchoconstriction with i.v. and p.o. ID50 values of 1.7 and 17 mg/kg, respectively. At 1, 3 and 6 hr after SB 207499 (30 mg/kg p.o.), OA-induced bronchospasm was inhibited by 92%, 70% and 58%, respectively, corresponding to elevated plasma concentrations of 1.62 ± 0.19, 1.65 ± 0.29 and 0.93 ± 0.24 μg/ml, respectively, of SB 207499. SB 207499 also inhibited house dust mite-induced bronchoconstriction (ID50 = 0.9 mg/kg i.v. and 8.9 mg/kg p.o.). In contrast to its lack of bronchorelaxant activityin vitro, SB 207499 inhibited bronchospasm induced by i.v. leukotriene D4 (LTD4) [ID50 = 3 mg/kg i.v.]. The bronchorelaxant effect of i.v.-administered SB 207499 was at least additive with that of salbutamol in reversing infused histamine-enhanced airway tone, but it did not alter base line or enhance salbutamol-induced cardiovascular effects. In conscious guinea pigs, SB 207499 (10 or 30 mg/kg p.o.), 1 hr before antigen or LTD4 challenge, markedly reduced bronchospasm and subsequent eosinophil influx as measured by bronchoalveolar lavage 24 hr after provocation. SB 207499 administered after OA or LTD4 challenge also reduced airway eosinophilia measured at 24 hr after OA challenge or 96 hr after LTD4 challenge. These results, coupled with the broad anti-inflammatory activity of SB 207499 previously described (Barnette et al., 1998), suggest that SB 207499 will be useful in the treatment of asthma and other inflammatory disorders.
Footnotes
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Send reprint requests to: David C. Underwood, Ph.D., SmithKline Beecham Pharmaceuticals, Pulmonary Pharmacology, UW2532, P.O. Box 1539, King of Prussia, PA 19406
- Abbreviations:
- PDE4
- phosphodiesterase type 4
- OA
- ovalbumin
- HDM
- house dust mite
- LTD4
- leukotriene D4
- SB 207499 (Ariflo)
- c-4-cyano-4-3-cyclopentyloxy-4-methoxyphenyl-r-1-cyclohexane carboxylic acid
- BAL
- bronchoalveolar lavage
- Received November 26, 1997.
- Accepted July 10, 1998.
- The American Society for Pharmacology and Experimental Therapeutics
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