Study of AMG 673 in Subjects With Relapsed/Refractory Acute Myeloid Leukemia

Inclusion Criteria

- Subject has provided informed consent prior to initiation of any study-specific
activities/procedures.

- Subjects ≥ 18 years of age at the time of signing consent.

- AML as defined by the WHO Classification (Appendix D) persisting or recurring
following 1 or more treatment courses except promyelocytic leukemia (APML).

- More than 5% myeloblasts in bone marrow.

- Eastern Cooperative Oncology Group (ECOG, Appendix F) Performance Status of ≤ 2.

- Renal function as follows: serum creatinine < 2.0 mg/dL (176.84 mmol/L) and estimated
glomerular filtration rate > 30 mL/min/1.73 m2.

- Hepatic function as follows: Aspartate aminotransferase (AST) and Alanine
aminotransferase (ALT) ≤ 3.0 x upper limit of normal (ULN). Bilirubin ≤ 1.5 x ULN
(unless considered due to Gilbert's syndrome or hemolysis) Exclusion Criteria

- Active extramedullary AML in the central nervous system (CNS).

- Known hypersensitivity to immunoglobulins.

- White blood cells (WBC) > 15,000 cells/mcL (15 cells x 10^9/L) at screening. In
subjects with WBC > 15,000 cells/mcL at screening with lymphocyte predominance,
subject may be deemed eligible for the trial by the Amgen physician, after discussion
with the investigator.

- Prior malignancy (other than in situ cancer) unless treated with curative intent and
without evidence of disease for > 2years before screening.

- Autologous HSCT within 6 weeks prior to start of AMG 673 treatment.

- Allogeneic HSCT within 3 months prior to start of AMG 673 treatment.

- Non-manageable graft versus host disease.

- History or evidence of cardiovascular risk including any of the following:

- History or evidence of clinically significant arrhythmias (ventricular
fibrillation, ventricular tachycardia, supraventricular tachycardia, atrial
tachycardia/flutter, atrial fibrillation with rapid ventricular response, second
or third degree atrioventricular block, and sick sinus syndrome).

- Exception: Subjects with controlled atrial fibrillation for > 30 days prior to
study day 1 are eligible. Controlled atrial fibrillation is defined as atrial
fibrillation with no rapid ventricular response which requires no change in
medication/dosage or addition of new medication or hospital admission within 30
days prior to study day 1.

- History of acute coronary syndromes (eg, myocardial infarction and unstable
angina) and/or coronary angioplasty within 6 months prior to study day 1.

- History or evidence of ≥ Class II congestive heart failure as defined by New York
Heart Association (NYHA).

- Chronic hypertension (defined as a systolic blood pressure [SBP] >140 mm Hg
and/or diastolic blood pressure [DBP] > 90 mm Hg which cannot be controlled by
anti hypertensive therapy).

- Subjects with intra-cardiac defibrillators.

- Abnormal cardiac valve morphology (≥ grade 2) (subjects with grade 1
abnormalities [ie, mild regurgitation/stenosis] can be entered on study. Subjects
with moderate valvular thickening should not be entered on study).

- History of arterial thrombosis (eg, stroke or transient ischemic attack) in the past 3
months.

- Active infection requiring intravenous antibiotics within 1 week of study enrollment
(day 1).

- Known positive test for human immunodeficiency virus (HIV).

- Positive for hepatitis B surface antigen.

- Positive for hepatitis C or chronic hepatitis C.

· Possible exceptions: acute hepatitis C and completely cleared of the virus
(demonstrated by negative viral load), chronic hepatitis C with undetectable viral
load defined by sustained virologic response 24 weeks (SVR24) after completion of
anti-hepatitis C treatment.

- Unresolved toxicities from prior antitumor therapy, defined as not having resolved to
CTCAE, version 4.0 grade 1 (with the exception of myelosuppression, eg, neutropenia,
anemia, thrombocytopenia), or to levels dictated in the eligibilitycriteria with the
exception of alopecia or toxicities from prior antitumor therapy that are considered
irreversible (defined as having been present and stable for > 2 months) which 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.

- Antitumor therapy (chemotherapy, antibody therapy, investigational agents,
molecular-targeted therapy or retinoid therapy) within 14 days of day 1. Exception:
hydroxyurea to control peripheral blood leukemic cell counts isallowed until start of
IP treatment.

- Treatment with systemic immune modulators including, but not limited to, non-topical
systemic corticosteroids (exception: physiological replacement and pre-medication for
blood products is permitted), cyclosporine, and tacrolimus within 2 weeks before
enrollment (day 1).

- Prior treatment with chimeric antigen receptor T cell (CAR-T) infusion for the
treatment of AML (CD33 or other target)

- Prior participation in an investigational study (drug, procedure or device) within 21
days of study day 1.

- Major surgery within 28 days of study day 1 with the exception of biopsy and insertion
of central venous catheter.

- History or evidence of any other clinically significant disorder, condition or disease
that, in the opinion of the investigator or Amgen physician, if consulted, would pose
a risk to subject safety or interfere with the study evaluation, procedures or
completion.

- Males and females of reproductive potential who are unwilling to practice a highly
effective method(s) of birth control while on study through 15 weeks after receiving
the last dose of study drug. Acceptable methods of highly effective birth control
include sexual abstinence (males, females); vasectomy; bilateral tubal
ligation/occlusion; or a condom with spermicide (men) in combination with hormonal
birth control or intrauterine device (IUD) (women). Males who are unwilling to abstain
from sperm donation while on study through 5 half-lives after receiving the (last
[multiple-dose studies]) dose of study drug.

- Females who are lactating/breastfeeding or who plan to breastfeed while on study
through 15 weeks after receiving the last dose of study drug.

- Females with a positive pregnancy test

- Females planning to become pregnant while on study through 15 weeks after receiving
the last dose of study drug.

- Subject likely to not be available to complete all protocol-required study visits or
procedures, and/or to comply with all required study procedures to the best of the
subject and investigator's knowledge.