Biological Activity: | Highly selective histamine H 4 receptor silent antagonist; binds with high affinity to the human H 4 receptor (K i = 26 nM) and is > 540-fold selective over the H 3 receptor (K i = 14.1 μ M). In vitro, inhibits mast cell and eosinophil chemotaxis with IC 50 values of 138 and 530 nM respectively. Orally active in vivo . |