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).
CGP74514A is a CDK1 inhibitor with potential anticancer activity. In U937 cells, CGP74514A - induced apoptosis (5 microM) became apparent within 4 hr and approached 100% by 24 hr. The pan- caspase inhibitor Boc-fmk and the caspase-8 inhibitor lETD-fmk opposed CGP74514A -induced caspase-9 activation and PARP degradation, but not cytochrome c or Smac DIABLO release. CGP74514A -mediated apoptosis was substantially blocked by ectopic expression of full-length Bel- 2, a loop-deleted mutant Bcl-2, and Bcl-x(L). CGP74514A treatment (5 microM; 18 hr) resulted inincreased p21(CIP1) expression, p27(KIP1) degradation, diminished E2F1 expression, and dephosphorylation of p34(CDC2). It also induced early (i.e., within 2 hr) inhibition of CDK1 activity and dephosphorylation of pRb, followed by pRb degradation, but did not block pRb phosphorylation at CDK2- and CDK4- specific sites. These findings indicate that the selective CDK1 inhibitor, CGP74514A , induces complex changes in cell cycle......