Adriforant hydrochloride (PF-3893787 hydrochloride) is a novel histamine H4 receptor antagonist binding affinity ( K i =2.4 nM) and is also a functional ( K i =1.56 nM) antagonist. In Vitro Adriforant is tested and observed binding K i =2.4 nM and functional K i =1.56 nM for H4R. Data from functional assays produce convergent projections of the free plasma efficacious concentration and Adriforant (Compound 13) is fast on/fast off on rhH4R. The in vitro IC 50 on human native isolated eosinophils assessing actin polymerisation is 1.16 nM and assuming need 10 times the IC 50 for >90% receptor occupancy (and therefore near complete inhibition of the response) suggested a concentration of 12 nM. The data in the whole blood GAFS assay demonstrates that the imetit induced shape change is completely blocked at a total blood concentration of 30 nM (which correcting for PPB and blood partitioning equates to approximately 10 nM free). For the purpose of dose projection and safety margin calculation, a Ceff/Cmin concentration of 10-15 nM is used. MCE has not independently confirmed the accuracy of these methods. They are for reference only. Form:Solid IC50& Target:Ki: 2.4 nM (H4R bind), 1.56 nM (H4R func)