The experimental asthma caused by IgE antibody in rats is inhibited by HSR-6071 (0.01-0.1 mg/kg; i.v.) in a dose-dependent manner. The bronchoconstriction mediated by IgE or IgG antibody in guinea-pigs is also prevented by HSR-6071 (0.3, 1,3 mg/kg; i.v.). HSR-6071 inhibits cyclic AMP phosphodiesterase activity and produces relaxation of the guinea-pig isolated trachea.
HSR-6071 inhibits the IgE-mediated histamine release with an IC ₅₀ of 0.46 nM. HSR-6071 is effective not only by i.v. but also by p.o. administration on the IgE mediated PCA in rats. The most potent inhibition with HSR-6071 is observed when it is given p.o. 5 min before the antigen challenge, indicating the rapid absorption of HSR-6071 through the gastrointestinal tract.