Inclusion Criteria:

          -  Relapsed/refractory AML (>= 20% blasts in bone marrow or extramedullary leukemia) or
             newly diagnosed AML patients who are not candidates for (age >= 70 years; adverse
             cytogenetics, e.g., as defined by the Medical Research Council [MRC] prognostic
             groupings; secondary AML; organ dysfunction arising from significant co-morbidities
             not directly linked to leukemia; Eastern Cooperative Oncology Group [ECOG] = 2) or not
             willing to undergo intensive chemotherapy; Note that both relapsed/refractory and
             newly diagnosed AML patients will be eligible for the dose escalation part of the
             study, but only newly diagnosed patients will be eligible for the dose expansion
             cohort

          -  Patients must have measurable disease as defined the presence of >= 20% blasts in bone
             marrow or extramedullary leukemia

          -  Eligible patient must show evidence of wild-type (WT) p53 as assessed by central DNA
             sequencing; note, that since patients with AML have a rapidly proliferating disease,
             patient can be enrolled and begin treatment prior to obtaining the results of this
             test; patients who are found to the TP53 mutated will be removed from study and can
             continue on single agent decitabine; however patients will continue to be followed for
             toxicity

          -  ECOG performance status =< 2 (Karnofsky >= 60%)

          -  Total bilirubin < 1.5 x institutional upper limit of normal (ULN) (< 2.0 x ULN for
             subjects with documented Gilbert's syndrome or < 3.0 x ULN for subjects for whom the
             indirect bilirubin level suggests an extrahepatic source of elevation)

          -  Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase [SGOT]) and
             alanine aminotransferase (ALT) (serum glutamic pyruvic transaminase [SGPT]) =< 2.5 x
             ULN

          -  Alkaline phosphatase < 2.0 x ULN (if liver or bone metastases are present, < 3.0 x
             ULN)

          -  Body surface area (BSA)-normalized creatinine clearance >= 30 mL/min/1.73 m^2 (using
             Cockcroft-Gault creatinine clearance [CrCl])

          -  Prothrombin time (PT) or partial thromboplastin time (PTT) < 1.5 x upper limit of
             normal (ULN), OR international normalized ratio (INR) < 1.5

          -  Patient must be willing to submit the blood sampling and bone marrow sampling for the
             PK and PD analyses and exploratory biomarkers

          -  The effects of KRT-232 (AMG-232) on the developing human fetus are unknown; for this
             reason and because decitabine is known to be teratogenic, women of child-bearing
             potential must agree to use adequate contraception prior to study entry and for the
             duration of study participation through 5 weeks (women) after receiving the last dose
             of KRT-232 (AMG-232); 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; men treated or enrolled on this protocol must also agree to use
             adequate contraception prior to the study, for the duration of study participation,
             and 3 months after completion of KRT-232 (AMG-232) administration

               -  Adequate methods of effective birth control include sexual abstinence (men,
                  women); vasectomy; or a condom with spermicide (men) in combination with barrier
                  methods, hormonal birth control or intrauterine device (IUD) (women)

          -  Ability to understand and the willingness to sign a written informed consent document

          -  White blood cell (WBC) count < 50,000/µL before administration of decitabine on cycle
             1 day 1; Note: hydroxyurea may be used to control the level of circulating leukemic
             blast cell counts to not lower than 10,000/uL during the study

        Exclusion Criteria:

          -  Acute promyelocytic leukemia with t(15;17)(q22;q12) and/or PML-RARA molecular
             rearrangement

          -  Patients with previously untreated AML with core binding factor (CBF) chromosomal
             aberrations (inv[16]/t[16;16] or t[8;21]); Note that patients with relapsed or
             refractory AML with CBF chromosomal aberrations will be eligible

          -  Unresolved toxicities from prior anti-tumor therapy, defined as not having resolved to
             Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 grade 0 or 1, or to
             levels dictated in the eligibility criteria with the exception of alopecia (grade 2 or
             3 toxicities from prior antitumor therapy that are considered irreversible [defined as
             having been present and stable for > 6 months], such as ifosfamide-related
             proteinuria, may be allowed if they are not otherwise described in the exclusion
             criteria AND there is agreement to allow by both the investigator and sponsor)

          -  Patients who are receiving any other investigational agents

          -  Major surgery within 28 days of study day 1

          -  Patients with known central nervous system involvement at the time of study entry will
             be excluded from this clinical trial because of their poor prognosis and because they
             often develop progressive neurologic dysfunction that would confound the evaluation of
             neurologic and other adverse events

          -  History of allergic reactions attributed to compounds of similar chemical or biologic
             composition to KRT-232 (AMG-232) or decitabine

          -  All herbal medicines (e.g., St. John's wort), vitamins, and supplements consumed by
             the subject within the 30 days prior to receiving the first dose of KRT-232 (AMG-232),
             and continuing use, if applicable, will be reviewed by the principal investigator

          -  Use of any known CYP2C8 substrates with a narrow therapeutic window is not allowed
             during the study and patients must come off 14 days prior to receiving the first dose
             of KRT-232 (AMG-232)

          -  Use of any known CYP3A4 substrates with narrow therapeutic window (such as alfentanil,
             astemizole, cisapride, dihydroergotamine, pimozide, quinidine, sirolimus, or
             terfanide) within the 14 days prior to receiving the first dose of KRT-232 (AMG-232);
             other medications (such as fentanyl and oxycodone) may be allowed per investigator's
             assessment/evaluation

          -  Treatment with medications known to cause corrected QT (QTc) interval prolongation
             within 7 days of study day 1 is not permitted unless approved by the principal
             investigator; use of ondansetron is permitted for treatment of nausea and vomiting

          -  Current use of warfarin, factor Xa inhibitors and direct thrombin inhibitors

               -  Note: Low molecular weight heparin and prophylactic low dose warfarin are
                  permitted; PT/PTT must meet the inclusion criteria; subjects taking warfarin must
                  have their INR followed closely

          -  Uncontrolled intercurrent illness including, but not limited to, active infection,
             symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or
             psychiatric illness/social situations that would limit compliance with study
             requirements; patients receiving an anti-microbial agent may be eligible if the
             patient remains afebrile and hemodynamically stable for 72 hours; patients with
             myocardial infarction within 6 months of study day 1, symptomatic congestive heart
             failure (New York Heart Association [NYHA] class III and higher), unstable angina, or
             cardiac arrhythmia requiring medication are excluded

          -  Patients with gastrointestinal (GI) tract disease causing the inability to take oral
             medication, malabsorption syndrome, requirement for intravenous alimentation, prior
             surgical procedures affecting absorption, uncontrolled inflammatory GI disease (e.g.,
             Crohn's disease, ulcerative colitis)

          -  Patients with history of bleeding diathesis

          -  Positive hepatitis B surface antigen (HepBsAg) (indicative of chronic hepatitis B),
             positive hepatitis total core antibody with negative HBsAG (suggestive of occult
             hepatitis B), or detectable hepatitis C virus ribonucleic acid (RNA) by a
             polymerase-chain reaction (PCR) assay (indicative of active hepatitis C - screening is
             generally done by hepatitis C antibody [HepCAb], followed by hepatitis C virus RNA by
             PCR if HepCAb is positive)

          -  Human immunodeficiency virus (HIV)-patients positive for human immunodeficiency virus
             (HIV) are NOT excluded from this study, but HIV-positive patients must have:

               -  A stable regimen of highly active anti-retroviral therapy (HAART)

               -  No requirement for concurrent antibiotics or antifungal agents for the prevention
                  of opportunistic infections

               -  A CD4 count above 250 cells/mcL and an undetectable HIV viral load on standard
                  PCR-based test

          -  Men and women of reproductive potential who are unwilling to practice acceptable
             methods of effective birth control while on study through 5 weeks (women) or 3 months
             (men) after receiving the last dose of KRT-232 (AMG-232); acceptable methods of
             effective birth control include sexual abstinence (men, women); vasectomy; or a condom
             with spermicide (men) in combination with barrier methods, hormonal birth control or
             IUD (women)

          -  Pregnant women are excluded from this study because KRT-232 (AMG-232) is an agent with
             the potential for teratogenic or abortifacient effects; because there is an unknown
             but potential risk for adverse events in nursing infants secondary to treatment of the
             mother with KRT-232 (AMG-232), breastfeeding should be discontinued if the mother is
             treated with KRT-232 (AMG-232); these potential risks may also apply to other agents
             used in this study

          -  Women who are lactating/breast feeding or who plan to breastfeed while on study
             through 1 week after receiving the last dose of study drug

          -  Patients with a baseline QTc > 500 msec and patients with a family history of
             prolonged QT syndrome

          -  Patients with known TP53 mutations or chromosome 17 or 17p deletions