Batebulast (NCO-650) is an anti-allergic drug. It significantly inhibited both the initial and secondary increases in cAMP stimulated by antigen, anti-IgE and concanavalin A (Con A) in rat peritoneal mast cells. It strongly inhibited the incorporation of the 3H-methyl moiety into phospholipid by antigen, anti-IgE and Con A during histamine release. Batebulast significantly inhibited the compound 48/80-induced bronchoconstriction in dogs. Batebulast had no effect on the bronchoconstriction induced by inhalation of acetylcholine, suggesting that NCO-650 appears to have no anti-cholinergic effect and thus no effect on the vagal reflex that occurred during the asthmatic responses. NCO-650 may be useful for the treatment of bronchial asthma as an orally active drug. Batebulast has been in phase II clinical trials for the treatment of asthma in Japan. However, this research has been discontinued.