Relapse Prophylaxis With N-803 for AML and MDS Pts Following Allo HSCT

Inclusion Criteria:

1. Diagnosis of acute myelogenous leukemia (AML) or myelodysplastic syndrome (MDS) for
whom an allogeneic hematopoietic stem cell transplant using a reduced intensity
conditioning is planned or has been performed and patient is prior to day 60
post-transplant.

2. Able to begin study treatment between day +42 and day +60 after the transplant and
meets the following transplant related requirements:

- Sustained neutrophil (ANC > 1000/mcL) and platelet (> 30,000/mcL) engraftment

- >50% donor myeloid and lymphoid chimerism blood or bone marrow on most recent
bone marrow (BM) evaluation

- No evidence of recurrent disease on most recent bone marrow evaluation (day 21 or
28 post-transplant is acceptable)

- No morphologic evidence of relapse (< 5% bone marrow blasts) on most recent BM
evaluation (Day 21 or 28 post-transplant is acceptable)

- Being followed in the outpatient setting (not an inpatient)

- No plan of giving other anti-cancer treatment (i.e. maintenance therapy [e.g.
sorafenib for FLT3m+ AML or hypomethylating therapy], additional therapy for MRD)

3. If acute GVHD is present it must be clinically improving on topical steroids and/or on
low dose systemic steroids (≤ 0.3 mg/kg/day prednisone) and with clinical stability
for at least 1 week prior to determination of eligibility. GVHD prophylaxis will be
continued per individual institutional standard practice

4. One of the following donor graft sources used for the transplant:

- Group 1: sibling donor

- Group 2: haploidentical donor [with post-transplant cyclophosphamide]

- Group 3: unrelated donor

- Group 4: unrelated umbilical cord blood

5. Karnofsky performance status ≥ 70%

6. Adequate organ function within 14 days of study enrollment defined as:

- Renal: serum creatinine: ≤ 2.0 mg/dL

- Hepatic: SGOT ≤ 3 x upper limit of institutional normal (ULN)

7. Sexually active females of child-bearing potential and males with partners of child
bearing potential must agree to use effective contraception during therapy and for 4
months after completion of therapy.

8. Voluntary written consent prior to the performance of any research related procedures

Exclusion Criteria:

1. Prior N-803 (previously known as ALT-803)

2. Pregnant or breastfeeding - N-803 is an investigational agent. Women of child bearing
potential must have a negative pregnancy test at screening.

3. Class II or greater New York Heart Association Functional Classification criteria or
serious cardiac arrhythmias likely to increase the risk of cardiac complications of
cytokine therapy (e.g. ventricular tachycardia, frequent ventricular ectopy, or
supraventricular tachyarrhythmia requiring chronic therapy)

4. Marked baseline prolongation of QT/QTc interval (e.g. demonstration of a QTc interval
> 500 milliseconds)

5. Active uncontrolled bacterial, fungal, or viral infections - all prior infections must
have resolved following optimal therapy and must be afebrile for at least 24 hours at
time of enrollment.

6. Active autoimmune disease requiring immunosuppressive therapy (GVHD prophylaxis is
permitted per institutional practice)

7. History of severe asthma and currently on chronic medications (mild asthma requiring
inhaled steroids only is eligible)

8. Received any investigational agent within the 14 days before the start of study
treatment (1st dose of N-803)