Protein kinase D (PKD) is a serine/threonine protein kinase that is activated by diacylglycerol, commonly downstream of PKC signaling. The three human PKD isoforms target a variety of proteins to alter cell proliferation, survival, invasion, and protein transport. CID755673 is a small molecule inhibitor of PKD (IC50s = 182, 280, 227 nM for PKD1, 2, and 3, respectively) that exhibits higher selectivity for PKD over Akt, polo-like kinase 1, CDK activating kinase, CAMKII and three different PKC isoforms (IC50s range from 15 to > 50 μM). At 25 μM, CID755673 has been shown to inhibit prostate cancer cell proliferation, cell migration, and invasion.