Safety and Efficacy Study of PD-616 Plus Cytarabine to Treat Acute Myelogenous Leukemia or Myelodysplastic Syndrome

Inclusion Criteria:

* Patient has newly diagnosed AML and refuses or is not eligible for treatment with aggressive chemotherapy and/or SCT; OR AML and has relapsed or been refractory to prior therapy; OR High-risk MDS, defined as IPSS intermediate-2 (INT-2) or IPSS high-risk, and refuses or is not eligible for standard or aggressive chemotherapy and SCT or prior experimental therapies; OR High-risk MDS, defined as IPSS INT-2 or IPSS high risk, and has failed or been refractory to deoxyribonucleic acid (DNA) hypomethylating agents (azacitidine or decitabine), lenalidomide, standard/aggressive chemotherapy, SCT, or prior experimental therapies.
* Has a bone marrow examination performed within 14 days before baseline (C1D1).
* Has an ECOG performance status score of 0 to 2.
* Aged between 18 and 75 years, inclusive.
* Has a life expectancy of ≥3 months.
* Has the following laboratory parameters within 7 days before baseline (C1D1):Serum creatinine ≤2 mg/dL; Total bilirubin ≤2.0 mg/dL; Alanine transaminase (ALT) or aspartate transaminase (AST) \<3.0×the upper limit of normal (ULN); Left ventricular ejection fraction (LVEF) \>40%; Forced expiratory volume in 1 second (FEV1) \>60% of predicted.
* If a female of child-bearing potential, has a negative serum pregnancy test result within 14 days before baseline and agrees to abstain from heterosexual intercourse or use a barrier method for contraception from 14 days before baseline (C1D1) through 30 days after the last study drug dose.
* If male, agrees to use a latex condom during any sexual contact with a female of child-bearing potential.
* Able to understand and willing to provide written informed consent.

Exclusion Criteria:

* Has received prior treatment with PD-616 or low-dose cytarabine.
* Has received chemotherapy (except hydroxyurea), biological therapy, radiotherapy or investigational therapy within 4 weeks before baseline (C1D1).
* Has active central nervous system (CNS) involvement (documented by radiologic lesions and/or malignant cells in the cerebrospinal fluid \[CSF\]).
* Has acute promyelocytic leukemia (APL, FAB M3).
* Has another active systemic malignancy treated with chemotherapy within 12 months before baseline (C1D1).
* Has known human immunodeficiency virus (HIV) infection.
* Has active graft-versus-host disease (GVHD).
* Has uncontrolled active infection of any kind. (Patients with infections controlled by active antibiotic treatment are eligible).
* Has significant renal or hepatic disease, uncontrolled or severe cardiovascular or pulmonary diseases, or other uncontrolled medical condition that, based on the Investigator's assessment, would compromise the patient's ability to tolerate study treatment or the assessment of treatment response.