Riviciclib is a potent inhibitor of cyclin-dependent kinase (CDK)(CDK9-cyclinT1, CDK4-cyclin D1, and CDK1-cyclinB with IC50s of 20 nM, 63 nM, and 79 nM, respectively),with antitumor activity on cisplatin-resistant cells.
CDK12-IN-4, a pyrazolotriazine compound, exhibits potent inhibition of CDK12 by achieving an IC50 value of 0.641 μM, utilizing high ATP levels (2 mM). Notably, CDK12-IN-4 does not impact CDK2 Cyclin E (IC50 > 20 μM) or CDK9 Cyclin T1 (IC50 > 20 μM) under the influence of high ATP (2 mM) levels (WO2021116178A1).