A recent phase II study however has shown significant response rates with Revlimid as a single agent in patients with MDS. The total response rate was 56%. The effects of Revlimid and SCF on hematopoietic progenitors cells were examined in vitro. RhSCF and Revlimid were shown to be synergistic in stimulating the proliferation of hematopoietic progenitor cells and their precursors in vitro, thereby forming the rationale for this study.