KH-CB20, an E/Z mixture, is a potent and selective inhibitor of CLK1 and the closely related isoform CLK4, with an IC50 of 16.5 nM for CLK1. KH-CB20 can also inhibit DYRK1A (IC50=57.8 nM) and CLK3 (IC50=488 nM)[1].
KH-CB20 shows selectivity for CLK1 (IC50=16.5 nM) over DYRK1A (IC50=57.8 nM) and CLK3 (IC50=488 nM)[1].
[1]. Fedorov O, et, al. Specific CLK inhibitors from a novel chemotype for regulation of alternative splicing. Chem Biol. 2011 Jan 28;18(1):67-76.