Abstract A series of aminooxadiazoles was optimized for inhibition of Cdc7. Early lead isoquinoline 1 suffered from modest cell potency (cellular IC 50= 0.71 μM measuring pMCM2), low selectivity against structurally related kinases, and high IV clearance in rats (CL= 18 L/h/kg). Extensive optimization resulted in azaindole 26 (Cdc7 IC 50= 1.1 nM, pMCM2 IC 50= 32 nM) that demonstrated robust lowering of pMCM2 in a mouse ...