Cdc2-Like Kinase Inhibitor, TG003 is a benzothiazole agent that acts as a specific and ATP-competitive inhibitor of Clk family members. Reports show that TG003 modifies the regulation of alternative splicing modulated by phosphorylation of SR proteins in vitro, and rescues defects in the development of Xenopus caused by an overabundance of Clk activity. Additionally, it represses the dissociation of nuclear speckles and serine/arginine-rich protein phosphorylation. TG003 has demonstrated no inhibiting affect on Clk3, protein kinase C, cAMP-dependent protein kinase, SRPK1, and SRPK2. Although TG009 is structurally analogous, it is has been shown to be 500-1000 times less potent on both Clk1/Sty and Clk4, and has been used as a negative control. Cdc2-Like Kinase Inhibitor, TG003 is an inhibitor of CLK1, CLK2 and CLK4.