Anti-asthmatic effect of ASP3258, a novel phosphodiesterase 4 inhibitor

ASP3258 is a potent and selective PDE4 inhibitor and exerts a wide-range of anti-inflammatory effects with low emetic potential, a major adverse effect of PDE4 inhibitors. Here, we investigated the anti-asthmatic potency of ASP3258 as compared with those of two representative PDE4 inhibitors: roflumilast and cilomilast. Orally administered ASP3258, roflumilast, and cilomilast all inhibited ovalbumin (OVA)-induced eosinophil infiltration into the airway of sensitized Brown Norway rats with ED(50) values of 0.81, 0.46, and 4.4 mg/kg, respectively. Histological examination also revealed a decreasing trend in inflammatory cell infiltration into the lung following ASP3258 administration. In vitro investigation of bronchodilatory activities showed that these compounds (10(-8)-10(-6) M) concentration-dependently inhibited OVA-induced contraction of trachea isolated from sensitized guinea pigs but had no effect on spasmogen-precontracted tracheal tension prepared from non-sensitized guinea pigs up to 10(-6) M. In vivo experiments using sensitized guinea pigs showed that these orally administered compounds inhibited OVA-induced increases in airway resistance with ED(50) values of 2.2, 0.35, and 12 mg/kg, respectively. Further, orally administered ASP3258 (0.1 and 1 mg/kg), roflumilast (0.1 and 1 mg/kg), and cilomilast (10 mg/kg) significantly suppressed airway hyperresponsiveness caused by OVA exposure. ASP3258's potent inhibition of antigen-induced bronchoconstriction and airway hyperresponsiveness, two characteristic symptoms of bronchial asthma, suggests that this compound will be useful in treating asthma.