Inclusion Criteria:

• Adult subjects (18 years of age or older) with advanced MDS or sAML/MDS with >=20% and <=50% blasts in bone marrow, as well as peripheral blasts <=50% and absolute blasts <1 Gi/L. Both Type I and Type II blasts will be included in blast count.
• Subjects must be dependent on regular platelet transfusions or have a platelet count taken within the 4 weeks prior to randomization that is <30 Gi/L.
• Subjects must be relapsed, refractory or ineligible to receive standard treatment options of azacitidine and decitabine and must be relapsed, refractory or ineligible to receive intensive chemotherapy or autologous/allogeneic stem cell transplantation.
• Prior therapy with demethylating agents (azacitidine or decitabine), lenalidomide or IL-11(oprelvekin) must have been completed at least 4 weeks before Day 1; antithymocyte/antilymphocyte globulin, intensive chemotherapy, or autologous/allogeneic stem cell transplantation must have been completed at least 2 months before Day 1.
• Subjects must have platelet count and platelet transfusion data available over a period of 4 weeks prior to randomization.
• Subjects with MDS or sAML/MDS must have stable disease indicated by a doubling time of peripheral blast counts >7 days during screening.
• During the 4 weeks prior to randomization, subjects must have a baseline bone marrow examination including all of the following:
• cytomorphology to confirm bone marrow blasts (Type I and Type II) between 20-50%,
• cytogenetics (provide only most prevalent abnormal clone),
• histopathology,
• flow cytometric assessment of the megakaryocytic lineage markers CD41, CD61, and TPO-R. Flow cytometry may alternatively be performed on peripheral blood blasts provided that the subject has a sufficiently increased peripheral blood blast count (as per local flow cytometry requirements).
• Supportive/palliative therapies such as cytokines (except for IL-11; oprelvekin), valproic acid, all-trans retinoic acid or mild chemotherapy are allowed if part of the local SOC, provided those therapies have been at a stable dose for 4 weeks or were completed 4 weeks prior to enrollment into this study. Erythropoiesis-stimulating agents (ESAs) in anemic subjects or granulocyte colony-stimulating factor (G-CSF) in subjects with severe neutropenia and recurrent infections are allowed during the study as per accepted standards. Subjects who enter the study on ESAs or G-CSF should continue at the same dose schedule until the optimal dose of study medication has been established.
• ECOG Status 0-3.
• Subject is able to understand and comply with protocol requirements and instructions.
• Subject has signed and dated informed consent.
• Prothrombin time (PT/INR) and activated partial thromboplastin time (aPTT) must be within 80 to 120% of the normal range at baseline.
• The following clinical chemistries MUST NOT exceed the upper limit of normal (ULN) reference range by more than 50%: creatinine, ALT, AST, total bilirubin (except for Gilbert's Syndrome), and alkaline phosphatase. In addition, albumin must not be below the lower limit of normal (LLN) by more than 10%.
• Subject is practicing an acceptable method of contraception (documented in chart). Female subjects (or female partners of male subjects) must either be of non-childbearing potential (hysterectomy, bilateral oophorectomy, bilateral tubal ligation or post-menopausal >1 year), or of childbearing potential and use 1 of the following highly effective methods of contraception (i.e., Pearl Index <1.0%) from 2 weeks prior to administration of study medication, throughout the study, and 28 days after completion or premature discontinuation from the study:
• Complete abstinence from intercourse;
• Intrauterine device (IUD);
• Two forms of barrier contraception (diaphragm plus spermicide, and for males condom plus spermicide);
• Male partner is sterile prior to entry into the study and is the only partner of the female;
• Systemic contraceptives (combined or progesterone only).

Exclusion Criteria:

• Subjects with a diagnosis of acute promyelocytic leukemia.
• History of treatment for cancer other than MDS or sAML/MDS with systemic chemotherapy and/or radiotherapy within the last 2 years.
• History of treatment with romiplostim or other TPO-R agonists.
• Pre-existing cardiovascular disease (including congestive heart failure, New York Heart Association [NYHA] Grade III/IV), or arrhythmia known to increase the risk of thromboembolic events (e.g. atrial fibrillation), or subjects with a QTc >450 msec (QTc >480 msec for subjects with Bundle Branch Block).
• Bone marrow fibrosis that leads to an inability to aspirate marrow for assessment.
• Spleen size >14 cm (length as per ultrasound examination).
• Leukocytosis >=25,000/uL prior to Day 1 of study medication.
• Female subjects who are nursing or pregnant (positive serum or urine Beta-human chorionic gonadotropin [B-hCG] pregnancy test) at screening or pre-dose on Day 1.
• Current alcohol or drug abuse.
• Treatment with an investigational drug within 30 days or 5 half-lives (whichever is longer) preceding the first dose of study medication.
• Active and uncontrolled infections.
• Subjects infected with Hepatitis B, C or Human Immunodeficiency Virus (HIV).