Biochemical inhibition assays reported in this work confirmed the hypothesis. Further testing with DNMT3A and DNMT3B revealed that both molecules are potent inhibitors of DNMT1 and selective versus DNMT3A and DNMT3B. Thus far, other than 5 (GSK3685032), the two quinazolines reported in this work are the few small-molecule selective inhibitors of DNMT1 over DNMT3A and DNMT3B.