DEC-C and Thioguanine for R/R AML

Inclusion Criteria: 1. Age ≥18 years of age 2. Patients must have histologically and cytologically confirmed R/R AML according to the World Health Organization classification based on documented bone marrow biopsy or peripheral blood specimens, with the exception of acute promyelocytic leukemia 1. Relapsed AML is defined as the detection of ≥5% blasts in the bone marrow or reappearance of leukemic blasts in the peripheral blood in a patient with prior remission 2. Refractory AML is defined as the failure to obtain a CR, CRh, or CRi after at least two courses of intensive induction (including hypomethylating agent plus venetoclax induction) or at least six cycles of a hypomethylating agent-based regimen (except venetoclax combinations as above) 3. Able to provide informed consent 4. Eastern Cooperative Oncology Group (ECOG) performance score of 0 to 2 or Karnofsky ≥60% 5. Adequate organ function defined by the following parameters: 1. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤5x the upper limit of normal (ULN) 2. Bilirubin ≤2x the ULN unless due to known Gilbert's disease or hemolysis due to blood transfusion 3. Calculated glomerular filtration rate (GFR) of ≥ 30 mL/min/1.73 m2 6. Prior hypomethylating agent is allowed 7. Female patients of childbearing potential must not be nursing or planning to become pregnant and require a negative urine or serum pregnancy test within 30 days of study therapy. 8. Female patients of childbearing potential must be willing to use at least 1 method of highly effective contraception during the study. Should a woman become pregnant or suspect she is pregnant while she or her partner is participating in this study, she should inform her treating physician immediately. 9. Male patients treated or enrolled who are sexually active must agree to adequate contraception use and refrain from sperm donation throughout the duration of the study, and up to 4 months after completion of thioguanine and decitabine-cedazuridine. 10. Willing to provide pretreatment bone marrow aspirate and biopsies samples as well as subsequent bone marrow aspirate and biopsies samples during the study. 11. Ability to understand and the willingness to sign a written informed consent document. Exclusion Criteria: 1. Previously received thioguanine 2. Any anti-leukemic therapy, including investigational therapies, within 14 days of study treatment initiation. Hydroxyurea for blood count control is allowed throughout induction cycle(s) 3. Prior allogeneic hematopoietic stem cell transplantation within 3 months of study enrollment; active graft versus host disease 4. Clinical suspicion for active central nervous system (CNS) involvement by AML; previously treated CNS involvement is allowed 5. Second malignancy requiring treatment within 6 months of study enrollment, with the exception of non-melanoma skin cancers or cancers requiring hormonal therapy only 6. Active, uncontrolled infection 7. Human immunodeficiency virus (HIV) not controlled by standard therapy 8. Active hepatitis B or C infection. Participants whose infections are controlled with antiviral therapy are allowed. 9. Significant medical diseases or comorbidities, in the opinion of the investigator, that would preclude the safe participation in the study 10. Known hypersensitivity to DEC-C or thioguanine