Cyclin-dependent kinases (CDKs) are key regulators of cell cycle progression and are therefore promising targets for cancer therapy. (R)-CR8 is a second-generation analog of (R)-roscovitine that inhibits Cdk1/cyclin B, Cdk2/cyclin A, Cdk2/cyclin E, Cdk5/p25, and Cdk9/cyclin T with IC50 values of 0.09, 0.072, 0.041, 0.11, and 0.18 μM, respectively. (R)-CR8 has 2- to 4-fold improved potency for the inhibition of CDKs over (R)-roscovitine and can inhibit the proliferation of various cancer cell lines with ~40-fold more potency than (R)-roscovitine (IC50s ~ 0.39 versus 27.8 μM, respectively). (R)-CR8 also inhibits casein kinase 1 (CK1δ/ε) with an IC50 value of 0.40 μM and inhibits GSK3α/β with an IC50 value of 12 μM.
