Blood and bone marrow samples will be obtained periodically for pharmacokinetic and biomarker correlative studies. Pharmacokinetic analysis by ELISA; anti-aflibercept antibody measurements; analysis of VEGF and VEGFR expression; and analysis of gene expression by quantitative PCR will be conducted. The effect of aflibercept on apoptosis and proliferation of CD34+ cells will also be analyzed by flow cytometry based assays.