Inclusion Criteria:

- AML by current WHO diagnostic criteria, any FAB type (except APML), Refractory ALL,
Accelerated/blast phase CML and Refractory MDS with total IPSS score of 2 or higher

- ECOG performance status <= 2

- Accessible for treatment, PK sample collection and required study follow-up

- Total Bilirubin ≤ 1.5 x ULN and ALT, AST ≤ 3 x ULN

Exclusion Criteria:

- Women who are pregnant or breastfeeding

- Subjects with Acute Promyelocytic leukemia disease or CNS leukemia disease)

- Hyperleukocytosis (defined as peripheral WBC >50,000/uL)

- Treatment with any other investigational agent for any indication within 30 days of
protocol enrollment

- Subjects a history of gastrointestinal disease

- Subjects less than four weeks from allogenic or autologous stem cell transplant
infusion