“…Therefore, any procedure applicable to cancer patients and capable of increasing the yield of circulating progenitors in the absence of added toxicity, is expected to have a profound impact on the feasibility, toxicity, and costs of hematopoietic transplants. Despite several attempts to improve PBPC mobilization by molecules capable of interfering with the mechanism(s) regulating hematopoietic stem cell trafficking [13, , –16], or by using combinations of cytokines [17, , , , , –23], so far substitutes or adjuncts to rhG‐CSF either failed to substantially improve the mobilization of blood progenitors obtained with rhG‐CSF alone or resulted in limited improvement [24, 25]. Recent data suggest that new agents, such as the CXCR4 antagonist, AMD3100, or the recombinant human growth hormone (GH) significantly improve PBPC mobilization in normal donors [16, 26, 27] or poor mobilizers [28, 29].…”