Inclusion Criteria:

- The subject has primary myelofibrosis (PMF), post-polycythemia vera MF, or
post-essential thrombocythemia MF and requires therapy, including subjects who have
received prior MF-directed therapy and relapsed or subjects with refractory disease;
or if newly diagnosed, then with intermediate or high risk according to the Lille
scoring system.

- The subject is unwilling to undergo or is not a candidate for peripheral stem
cell/bone marrow transplant.

- The subject is ≥18 years old.

- The subject has an Eastern Cooperative Oncology Group (ECOG) performance status of
≤2.

- The subject has adequate organ function.

- The subject has the capability of understanding the informed consent document and has
signed the informed consent document.

- Sexually active subjects (male and female) must use medically acceptable methods of
contraception during the course of the study.

- Female subjects of childbearing potential must have a negative pregnancy test at
screening.

- The subject has had no diagnosis of malignancy or evidence of other malignancy for 2
years prior to screening for this study (except non-melanoma skin cancer or in situ
carcinoma of the cervix).

Exclusion Criteria:

- The subject has uncontrolled intercurrent illness including, but not limited to,
ongoing or active infection, hypertension, symptomatic congestive heart failure,
unstable angina pectoris, myocardial infarction within 3 months, or cardiac
arrhythmias.

- The subject is pregnant or breastfeeding.

- The subject is known to be positive for the human immunodeficiency virus (HIV).

- The subject is unable or unwilling to abide by the study protocol or cooperate fully
with the investigator or designee.