A cell-permeable, reversible inhibitor of Cdk1, showing preference for Cdk1/cyclin B1 (Ki = 35 nM) over Cdk1/cyclin A (Ki = 110 nM); also inhibits Cdk2 (Ki = 340 nM), PKCδ (Ki = 318 nM), and SGK (Ki = 497 nM) but not Cdk4; reversibly arrests proliferating cells at the G2/M phase border,…