Inclusion Criteria:

          -  Diagnosis of 1 of the following diseases:

               -  Primary or secondary AML (including erythroleukemia and eosinophilic leukemia,
                  but excluding acute promyelocytic leukemia)

               -  B-cell ALL

               -  BPDCN

               -  CML in blast phase, resistant or intolerant to tyrosine kinase inhibitor therapy

          -  Patients with relapsed or refractory disease with no available standard therapy

          -  ECOG performance status 0-2

          -  Not a candidate for, or refusing treatment with hematopoietic stem cell
             transplantation

          -  Fertile patients must agree to use effective contraception during and for 4 weeks
             after the last dose of XmAb14045

          -  Male patients must agree to use highly effective contraception, and refrain from
             donating sperm during the treatment period and for at least 4 weeks after the last
             dose of XmAb14045

          -  Able and willing to complete the entire study

        Exclusion Criteria:

          -  Systemic antineoplastic therapy (including cytotoxic chemotherapy and toxin
             immunoconjugates, but excluding hydroxyurea), unconjugated antibody therapy, or
             radiotherapy within 2 weeks of the first dose of study treatment, or small molecule
             kinase inhibitors within 6 elimination half-lives of the first dose of study
             treatment.

          -  Prior therapy with CD123- or IL-3R-directed immunotherapies, including monospecific
             and bsAbs, immunoconjugates, or chimeric antigen receptor- modified T-cell therapy

          -  Failure to recover from Grade 3 or 4 toxicity from previous treatment (unrelated to
             malignant bone marrow involvement)

          -  Known uncontrolled central nervous system involvement by malignant disease

          -  Absolute blast count ≥10,000/mm3 or symptoms of leukostasis

          -  Diagnosis of promyelocytic leukemia

          -  Aspartate aminotransferase or alanine aminotransferase at screening >3.0 x upper limit
             of normal (ULN) unless considered due to leukemic organ involvement

          -  Bilirubin >1.5 x ULN, unless prior diagnosis and documentation of leukemic organ
             involvement, ongoing hemolysis, or Gilbert's syndrome

          -  Serum creatinine >2.0 x ULN, or estimated creatinine clearance <40mL/min

          -  Active heart failure or New York Heart Association Class III or IV or Objective
             Assessment C or D

          -  History or evidence of a clinically unstable/uncontrollable disorder, condition or
             disease other than primary malignancy, that in the opinion of the Investigator would
             pose a risk to the patient safety or interfere with the study evaluation, procedures,
             or completion

          -  Evidence of any active, uncontrolled bacterial, viral, parasitic, or systemic fungal
             infections within 1 week of first dose of study drug

          -  Positive test for human immunodeficiency virus (HIV) -I or -II antibodies, hepatitis B
             surface antigen (HBsAg), hepatitis B core antibody (HBcAb), or hepatitis C virus (HCV)
             antibody (unless HCV viral load test by PCR is negative). HBcAb positivity will be
             allowed if one or more of the following is true: a) HBsAb is present; b) hepatitis B
             DNA testing is negative and the patient is receiving hepatitis B reactivation
             prophylaxis with entecavir, tenofovir, or lamivudine

          -  Patient is pregnant or breast feeding, or planning to become pregnant while enrolled
             in the study, up to the End of Study visit