A Safety and Efficacy Study to Evaluate AMG 531 Treatment in Subject With Myelodysplastic Syndrome Receiving Revlimid

Inclusion Criteria: * Diagnosis of MDS by bone marrow biopsy based on the World Health Organization (WHO) classification * Low or Intermediate-1 risk category MDS using the IPSS * Planned to receive lenalidomide 10 mg capsule by mouth daily for all 28 days of each cycle for at least 4 cycles * Eastern Cooperative Oncology (ECOG) performance status of 0-2 * Subjects must be at least 18 years of age or older Exclusion Criteria: * Prior exposure to \>3 cycles of lenalidomide * Exposure to lenalidomide within the last 30 days * Prior history of leukemia or aplastic anemia * Prior history of stem cell transplantation * Prior malignancy (other than in situ cervical cancer or basal cell cancer of the skin) unless treated with curative intent and without evidence of disease for 3 years before randomization * Active or uncontrolled infections * Unstable angina, congestive heart failure \[NYHA \> class II\], uncontrolled hypertension \[diastolic \> 100 mmHg\], uncontrolled cardiac arrhythmia, or recent (within 1 year) myocardial infarction * History of arterial thrombosis ( eg, stroke or transient ischemic attack) in the past year * History of venous thrombosis in the past year * Received IL-11 within 4 weeks of screening * Less than 4 weeks since receipt of any investigational drug or device * Have previously received any other thrombopoietic growth factor * Pregnant or breast feeding * Subjects of reproductive potential who are not using adequate contraceptive precautions, in the judgment of the investigator * Known hypersensitivity to any recombinant E coli-derived product