In a dose-dependent fashion in guinea pigs, RS-601 (1-10 mg/kg) clearly inhibits the bronchoconstriction induced by intravenous administration of U-46619 and LTD4. Similarly, RS-1452 (10 mg/kg) significantly inhibits U-46619-induced bronchoconstriction. At a dose of 10 mg/kg, RS-601 significantly inhibits the late-phase response and LPS-induced AHR. However, it does not affect biphasic bronchial responses. Additionally, RS-601 (3 and 10 mg/kg) clearly inhibits the AHR[1].