High affinity and selective histamine H4 antagonist (Ki = 12.5 nM). Exhibits >80-fold selectivity for H4 over other histamine receptors and no significant activity at a range of other targets. Inhibits histamine-induced eosinophil shape change in whole blood in vitro and ovalbumin-induced inflammation in ovalbumin-sensitized mice in vivo. Orally bioavailable. Purity 98%. MW (observed): 294.22