[CAS NO. 942425-68-5]  PHA-767491 HCl

PHA-767491 displays approximately 20-fold selectivity for Cdk1, Cdk2 and GSK3-β, 50-fold selectivity for MK2 and Cdk5 and 100-fold selectivity for PLK1 and CHK2. PHA-767491 inhibits cell proliferation in a variety of human cell lines with IC50 of 0.86 μM for SF-268 to 5.87 μM for K562, and significantly induces apoptosis in a p53-independent manner in almost all cell lines in contrast with 5-FU or gemcitabine which only works in a few of cell lines. Unlike current DNA synthesis inhibitors, PHA-767491 treatment at 5 μM blocks the initiation of DNA replication but not replication fork progression, due to specific inhibition of Cdc7 kinase and Mcm2 phosphorylation at the Cdc7-dependent Ser40 site. The up-regulated Mcl-1 levels in ABT-737-resistant OCI-LY1 and SU-DHL-4 cells can be significantly decreased by PHA-767491 treatment at 3 μM possibly due to the inhibition of Cdk9, leading to the restoration of the sensitivity to ABT-737. The direct mitochondrial dependent pro-apoptosis effect of PHA-767491 is also observed when applied at 1 μM in quiescent chronic lymphocytic leukemia (CLL) cells through the similar mechanism with EC50 of 0.34-0.97 μM. While in proliferating CLL cells stimulated by CD154 and interleukin-4, PHA-767491 treatment at 5 μM abolishes DNA synthesis by inhibiting Cdc7 rather than triggering cell death.