Recently the CXCR4/CXCL12-axis has been recognized as one of the pivotal adhesion pathways by which hematopoietic stem cells are retained in the bone marrow. CXCR4 antagonists with different chemical specification are being developed. Pharmacology research guides the way to the rational development effective antagonists. One antagonist, plerixafor, is clinically approved now for stem cell mobilization of lymphoma and myeloma patients. This allows patients to receive potentially life-saving treatment which could not have been administered otherwise. Through early clinical studies it was recognized that CXCR4 antagonists also mobilize malignant hematopoetic cells, i.e. leukemia cells. In preclinical studies a sensitization of mobilized leukemic cells to standard cytotoxic chemotherapy could be shown. Clinical studies are under way. CXCR4 antagonists are an exciting new class of compounds which are also employed for the mobilization of angiogenic cells or for the treatment of solid tumors. In this book a concise review of the current status of knowledge and future developments will be presented.This book reports on CXCR4 antagonists, an exciting new class of compounds that aid in use of stem cells for treatment of leukemia and other cancers. Includes coverage of plerixafor, now approved for stem cell mobilization of lymphoma and myeloma patients.Preface.- Preclinical Experience with AMD3100 for Mobilization of Hematopoietic Stem and Progenitor Cells.- Molecular Pharmacology of CXCR4 Inhibition.- Combination Strategies for Stem Cell Mobilization Targeting CXCR4 and S1P Receptors.- Should We Stay Or Should We Go Now? Cell Adhesion and Mobilization Pathways of Hematopoietic Cellls.- Role of the CXCR4/CXCL12 Axis in Hematopoietic Stem Cell Trafficking.- Early Studies of AMD3100/Plerixafor in Healthy Volunteers.- The Current Role of Plerixafor in Stem Cell Mobilization for Hematopoietic Stem Cell Transplantation.- Relevance and Clinical Implications of Tumor Cell l3