CRT 0066101 is a novel, potent and selective inhibitor of protein kinase D (PKD) with IC₅₀ values of 1, 2.5 and 2 nM for PKD1, 2, and 3 respectively. CRT 0066101 exhibits selectivity for PKD against a panel of >90 protein kinases, including PKCα, MEK, ERK, c-Raf and c-Src.