CLK1-IN-1 is a potent and selective inhibitor of Cdc2-like kinase 1 (CLK1) with an IC50 of 2 nM.

CLK1:2 nM

In addition to CLK1, only two kinases have an IC50 value less than 100 nM, namely CLK2 (IC50: 31 nM) and CLK4 (IC50: 8 nM), DYRK1A is the strongest off-target. The effects of CLK1-IN-1 on yellow LC3 puncta also displays obvious dose dependency, and a dose of 10 μM shows the best performance. In addition, in CLK1-IN-1-treated cells, the number of red LC3 puncta (mRFP signals only35) increases compared with that of DMSO-treated cells, indicating the formation of autolysosomes. Importantly, CLK1-IN-1 stimulates the degradation of SQSTM1/p62 and increases the ratio of red LC3 puncta to yellow LC3 puncta, both of which indicate induction of autophagic flux by CLK1-IN-1.

Exposure to APAP causes severe liver injury, but treatment with CLK1-IN-1 (i.p., 30 mg/kg) provides significant hepatoprotection, reducing serum ALT and AST levels to normal.