Purity >95%. PHA-793887 is a pyrrolo[3,4-c]pyrazole that inhibits cyclin-dependent kinases Cdk2/cyclin A, Cdk2/cyclin E, Cdk5/p25, and Cdk7/cyclin H with IC50 values of 8, 8, 5, and 10 nM, respectively. It is more than 6-fold selective for these kinases over Cdk1/cyclin B, Cdk4/cyclin D1, Cdk9/cyclin T, and GSK3Beta (IC50 s = 60, 62, 138, and 79 nM, respectively). PHA-793887 is cytotoxic to human ovarian A2780, colon HCT116, pancreatic BX-PC3, and leukemic K562, KU812, KCL22, and TOM1 cells both in vitro and in xenograft models. This compound has been examined in patients with solid tumors in phase 1 clinical trials.