NU6027 is a potent cyclin-dependent kinase (CDK) and Rad3-related kinase (ATR) inhibitor. NU6027 has been shown to inhibit tumor cell growth. NU6027 inhibits ATR, impairing G2/M arrest and homologous recombination thus increasing sensitivity to DNVIP(LA)damaging agents and poly(ADP-ribose) polymerase (PARP) inhibitors