PDK Inhibitor II is a potent, ATP site-targeting PDK1 inhibitor (IC50 = 6 nM) and effectively suppresses cellular Akt Thr308 phosphorylation level in PC-3 cultures (IC50 ≤1 µM), while affecting PKA (IC50 = 1.6 µM) and 7 other kinases (IC50 ≥600 nM) only at much higher concentrations.