Inclusion Criteria:

          -  Confirmed diagnosis of primary or secondary AML [any subtype except acute
             promyelocytic leukemia (APL)] according to World Health Organization (WHO)
             classification

          -  Patients with AML must meet one of the following criteria, a or b:

             a. Primary Induction Failure (PIF) AML, defined as disease refractory to one of the
             following, i or ii: i. An intensive induction attempt, per institution. Induction
             attempts include high-dose and/or standard-dose cytarabine

             ± an anthracyclines/anthracenedione ± an anti-metabolite, with or without growth
             factor or targeted therapy containing regimens.

        Examples include but are not limited to:

          1. One cycle of high dose cytarabine (HiDAC) containing regimen

          2. One cycle of liposomal cytarabine and daunorubicin

          3. Two cycles of standard dose cytarabine containing regimen ii. For adults who are age
             75 years or older, or who have comorbidities that preclude use of intensive induction
             chemotherapy; PIF is defined as AML refractory to one of the following less intensive
             regimens, 1 or 2:

        1. ≥ 2 but ≤ 4 cycles of Bcl-2 inhibitors in combination with azacitidine, decitabine, or
        low dose cytarabine 2. ≥ 2 but ≤ 4 cycles of gemtuzumab ozogamicin monotherapy b. Early
        relapse (ER) AML, defined as AML in first relapse with initial CR1 duration < 6 months 3.
        Limit of 3 prior lines of therapy: up to 2 induction (induction, re-induction) or 1
        induction plus/minus 1 consolidation attempt, followed by a maximum of 1
        salvage/re-induction attempt.

          -  Eastern Cooperative Oncology Group (ECOG) performance status ≤2

          -  Life expectancy of at least 4 weeks

          -  Peripheral blast count </= 20,000/mm3 at the time of first dose

          -  Acceptable laboratory parameters and adequate organ reserve

        Exclusion Criteria:

          -  History of allogeneic stem cell transplantation

          -  Prior treatment with an anti-CD123-directed agent

          -  Need for concurrent other cytoreductive chemotherapy

          -  Any active untreated autoimmune disorders (with the exception of vitiligo, resolved
             childhood atopic dermatitis, prior Grave's disease now euthyroid clinically and with
             stable supplementation)

          -  Second primary malignancy that requires active therapy. Adjuvant hormonal therapy is
             allowed.

          -  Antitumor therapy or investigational agent within 14 days or 5 half-lives of Cycle 1
             Day 1.

          -  Requirement, at the time of study entry, for concurrent steroids > 10 mg/day of oral
             prednisone or the equivalent, except steroid inhaler, otic preparations, nasal spray
             or ophthalmic solution

          -  Use of immunosuppressant medications in the 2 weeks of Cycle 1 Day 1

          -  Use of granulocyte colony stimulating or granulocyte-macrophage colony stimulating
             factor in the 2 weeks of Cycle 1 Day 1

          -  Known central nervous system (CNS) leukemia

          -  Active uncontrolled infection (including, but not limited to viral, bacterial, fungal,
             or mycobacterial infection),

          -  Known human immunodeficiency virus infection, unless all of the following criteria are
             met:

             i. CD4+ count ≥ 350 cells/μL, ii. undetectable viral load, and iii. receiving highly
             active antiretroviral therapy.

          -  Known, active, history of or current acute or chronic hepatitis B or C virus (HBV)
             infection (as evidenced by detectable HBV surface antigen and HBV DNA ≥ 500 IU/mL),

          -  History of hepatitis C virus (HCV) infection, unless the infection has been treated
             and cured,

          -  Active SARS-CoV-2 infection. While SARS-CoV-2 testing is not mandatory for study
             entry, testing for ongoing infection should follow local clinical practice
             guidelines/standards. Participants with a positive test result for ongoing SARS-CoV-2
             infection, known asymptomatic infection, or suspected infection are excluded unless or
             until asymptomatic and with subsequent negative SARS-CoV-2 laboratory test.