Inclusion Criteria:

          -  Age ≥18 years at the time of voluntarily signing an IEC-approved informed consent,
             there is no upper age limit

          -  Diagnosis of AML with NPM1 mutation according to WHO criteria

          -  Confirmed FLT3 expression on leukemic cells

          -  Known mutational status of FLT3 (FLT3-ITD, FLT3-TKD, FLT3 wild type)

          -  Hematological CR (ANC count >1.000/μL, Thrombocytes > 100.000/μL), but MRD positivity
             after any therapy except allogeneic stem cell transplantation

          -  Life expectancy of > 3 months

          -  ECOG performance status ≤ 2

          -  Subject must be willing to receive transfusion of blood products

          -  Be willing and able to comply with the study protocol for the duration of the study

          -  Females of childbearing potential (FCBP) must undergo repetitive pregnancy testing
             (serum or urine) and results must be negative

          -  Reliable contraception should be maintained throughout the study and for 6 months
             after study treatment

          -  Unless practicing complete abstinence from heterosexual intercourse, sexually active
             FCBP must agree to use adequate contraceptive methods

          -  Males (including those who have had a vasectomy) must use an effective barrier method
             of contraception throughout the study and for 6 months after study treatment if
             sexually active with a female of childbearing potential

          -  All subjects must:

               -  understand that the investigational product could have a potential teratogenic
                  risk.

               -  be counseled about pregnancy precautions and risks of fetal exposure.

               -  be able to comply with all study-related procedures, medication use, and
                  evaluations.

        Exclusion Criteria:

        The presence of ANY of the following criteria will exclude a patient from study enrollment:

          -  Patients proceeding to hematopoietic stem cell transplantation (suitable candidate and
             donor available, informed consent of patient)

          -  Pregnant or breast feeding females

          -  >5% blasts in bone marrow or extramedullary disease

          -  Treatment with monoclonal antibody within 3 months before treatment with FLYSYN or
             known immunoglobulin intolerance

          -  Known positivity for HIV, active HBV, HCV, or Hepatitis A infection

          -  No consent for registration, storage and processing of the individual
             disease-characteristics and course as well as information of the family physician
             and/or other physicians involved in the treatment about study participation

          -  No consent for biobanking

          -  Presence of any medical/psychiatric condition or laboratory abnormalities which may
             limit full compliance with the study, increase the risk associated with study
             participation or study drug administration, or may interfere with the interpretation
             of study results and, in the judgment of the investigator, would make the patient
             inappropriate for entry into this study

          -  Prior history of malignancies, other than AML/myelodysplastic syndrome (MDS), unless
             the subject has (i) been free of the disease for ≥ 2 years. (ii) Exceptions include
             the following: Basal cell carcinoma of the skin, carcinoma in situ of the cervix,
             carcinoma in situ of the breast, incidental histological finding of prostate cancer
             (TNM stage of T1a or T1b)

          -  Patients receiving any medication listed in the Appendix IV "Prohibited Medications"
             (within 14 days prior to the first dose of study drug)

          -  Uncontrolled infection, e.g. infection progressing under adequate
             antimicrobial/antifungal/antiviral treatment

          -  Patients under ongoing treatment with another investigational medication or having
             been treated with an investigational medication within 14 days of screening

          -  Current treatment with immunosuppressive agents

          -  Systemic diseases (cardiovascular, renal, hepatic, etc.) that would prevent study
             treatment (e.g., creatinine >1.5x upper normal serum level; bilirubin, AST or AP >2.5x
             upper normal serum level; heart failure NYHA III/IV; severe obstructive or restrictive
             ventilation disorder)