Design, synthesis and evaluation of 2-aminothiazole derivatives as sphingosine kinase inhibitors

Sphingosine kinases (SphK1, SphK2) are main regulators of sphingosine-1-phosphate (S1P), which is a pleiotropic lipid mediator involved in numerous physiological and pathophysiological functions. SphKs are targets for novel anti-cancer and anti-inflammatory agents that can promote cell apoptosis and modulate autoimmune diseases. Herein, we describe the design, synthesis and evaluation of an aminothiazole class of SphK inhibitors. Potent inhibitors have been discovered through a series of modifications using the known SKI-II scaffold to define structure-activity relationships. We identified N-(4-methylthiazol-2-yl)-(2,4′-bithiazol)-2′-amine (24, ST-1803; IC50 values: 7.3 μM (SphK1), 6.5 μM (SphK2)) as a promising candidate for further in vivo investigations and structural development.