AC708 is a small molecule CSF1R inhibitor that effectively inhibits CSF1R phosphorylation mediated by CSF-1 (IC50 = 26 nM) and IL-34 (IC50 = 33 nM). It also inhibited the activity of growth factor-dependent cells cultured in CSF-1 (IC50 = 38 nM) or IL-34 (IC50 = 40 nM) and inhibited the differentiation and survival of primary human osteoclasts mediated by CSF-1 (IC50 = 15nM). AC708 showed significant specificity in kinase selectivity tests against CSF1R and the closely related PDGFR family of receptors PDGFRα and β, FLT3 and KIT.