Wee1 (EC 2.7.10.2) is a protein kinase, regulates the G2 checkpoint in response to DNA-damage. Preclinical studies have elucidated the role of wee1 in DNA-damage repair and the stabilization of replication forks, supporting the validity of wee1 inhibition as a viable therapeutic target in cancer. Wee1 belongs to a family of protein kinases involved in the terminal phosphorylation and inactivation of cyclin-dependent-kinase 1-bound cyclin B. It is the major kinase responsible for the inhibitory phosphorylation of the tyrosine15 residue on Cdk1/Cdc2, near its ATP-binding pocket, and plays a critical role in the proper timing of cell division by controlling the entry into mitosis and DNA-replication during S phase. Recent evidence demonstrates that wee1 is also involved in the coordination of DNA-replication and the maintenance of stalled replication forks through regulation of cyclin-dependent kinase 2 (Cdk2)[1].