Azacytidine (Aza) treatment is effective in some patients with acute myeloid leukemia (AML). Clinical observations suggest that DNMT3A-mutant patients represent a subgroup of AML patients that responds particularly well to Aza-treatment. Data coming from a mouse model support this finding and we have already generated molecular data suggesting a molecular pathway involved in Aza-response in DNMT3A-mutant AML patients. We now aim to validate these findings in primary AML-blasts. To this end, we have FACS-sorted blasts from patients with AML prior to and under Aza-treatment and plan to correlate pre-treatment as well as on-treatment methylomes to clinical Aza-response.