AZD6738 is a potent ATR kinase inhibitor with IC50 value of 1 nM against the isolated enzyme. AZD6738 selectively inhibits ATR activity by blocking the downstream phosphorylation of the serine/threonine protein kinase CHK1. This prevents ATR-mediated signaling, and results in the inhibition of DNA damage checkpoint activation, disruption of DNA damage repair, and the induction of tumor cell apoptosis. It also induces cell death and senescence in non-small cell lung cancer (NSCLC) cell lines. MW: 412.51. Purity ≥98% by HPLC