Mobilization of peripheral-blood stem cells by concurrent administration of daniplestim and granulocyte colony-stimulating factor in patients with breast cancer or lymphoma

A phase 1/2 study of chemosensitization with the CXCR4 antagonist plerixafor in relapsed or refractory acute myeloid leukemia

The interaction of acute myeloid leukemia (AML) blasts with the leukemic microenvironment is postulated to be an important mediator of resistance to chemotherapy and disease relapse. We hypothesized that inhibition of the CXCR4/CXCL12 axis by the small molecule inhibitor, plerixafor, would disrupt the interaction of leukemic blasts with the environment and increase the sensitivity of AML blasts to chemotherapy. In this phase 1/2 study, 52 patients with relapsed or refractory AML were treated with plerixafor in combination with mitoxantrone, etoposide, and cytarabine. In phase 1, plerixafor was escalated to a maximum of 0.24 mg/kg/d without any dose-limiting toxicities. In phase 2, 46 patients were treated with plerixafor 0.24 mg/kg/d in combination with chemotherapy with an overall complete remission and complete remission with incomplete blood count recovery rate (CR + CRi) of 46%. Correlative studies demonstrated a 2-fold mobilization in leukemic blasts into the peripheral circulation. No evidence of symptomatic hyperleukocytosis or delayed count recovery was observed with the addition of plerixafor. We conclude that the addition of plerixafor to cytotoxic chemotherapy is feasible in AML, and results in encouraging rates of remission with correlative studies demonstrating in vivo evidence of disruption of the CXCR4/CXCL12 axis.

Role of CXCR4 chemokine receptor blockade using AMD3100 for mobilization of autologous hematopoietic progenitor cells

G-CSF mobilization of hematopoietic progenitor cells (HPCs) is mediated through enzyme release from maturing myeloid cells, leading to digestion of adhesion molecules, trophic chemokines and their receptors, and the extracellular matrix. HPCs traffic to and are retained in the marrow through the trophic effects of the chemokine SDF-1alpha/CXCL12 binding to its receptor, CXCR4. AMD3100 reversibly inhibits SDF-1alpha/CXCR4 binding, and AMD3100 administration mobilizes CD34+ cells into the circulation. AMD3100 has been tested in several clinical trials which demonstrate that it improves the number of CD34+ cells mobilized including patients failing to mobilize with G-CSF alone. Engraftment of AMD3100-mobilized cells is prompt and durable. Toxicities are mild and infrequent. Lymphoma and myeloma cells do not appear to be mobilized. AMD3100 appears to be a promising agent for HPC mobilization.

Factors for PBPC collection efficiency and collection predictors

Factors affecting collection efficiency of peripheral blood stem cells (PBSCs) include patient's age, diagnosis, preceding chemoradiotherapy, disease invasion of the bone marrow and mobilizing chemotherapy in PBSC collection for autologous transplants. Mobilizing cytokines, timing for apheresis, machines and operating software would affect mobilization and collection of PBSCs both for autologous and allogeneic transplantation. Also donor's age and gender would affect PBSC yield for allogeneic transplantation. Surrogate markers including peripheral blood CD34+ cell counts before mobilization and on day of collection have been reported to predict the yield of PBSC harvest. A number of standard procedures have been developed based on these findings. Newer agents for PBSC mobilization are being evaluated and still other factors affecting mobilization are being sought to better predict and cope with poor mobilization.

Rapid mobilization of CD34+ cells following administration of the CXCR4 antagonist AMD3100 to patients with multiple myeloma and non-Hodgkin's lymphoma

PURPOSE

Interactions between the chemokine receptor CXCR4 and its ligand stromal derived factor-1 regulate hematopoietic stem-cell trafficking. AMD3100 is a CXCR4 antagonist that induces rapid mobilization of CD34+ cells in healthy volunteers. We performed a phase I study assessing the safety and clinical effects of AMD3100 in patients with multiple myeloma (MM) and non-Hodgkin's lymphoma (NHL).

PATIENTS AND METHODS

Thirteen patients (MM, n=7; NHL, n=6) received AMD3100 at a dose of either 160 microg/kg (n=6) or 240 microg/kg (n=7). WBC and peripheral blood (PB) CD34+ cell counts were analyzed at 4 and 6 hours following injection.

RESULTS

AMD3100 caused a rapid and statistically significant increase in the total WBC and PB CD34+ counts at both 4 and 6 hours following a single injection. The absolute CD34+ cell count increased from a baseline of 2.6 +/- 0.7/microL (mean +/- SE) to 15.6 +/- 3.9/microL and 16.2 +/- 4.3/microL at 4 hours (P=.002) and 6 hours after injection (P =.003), respectively. The absolute CD34+ cell counts observed at 4 and 6 hours following AMD3100 were higher in the 240 microg/kg group (19.3 +/- 6.9/microL and 20.4 +/- 7.6/microL, respectively) compared with the 160 microg/kg group (11.3 +/- 2.7/microL and 11.3 +/- 2.5/microL, respectively). The drug was well tolerated and only grade 1 toxicities were encountered.

CONCLUSION

AMD3100 appears to be a safe and effective agent for the rapid mobilization of CD34+ cells in patients who have received prior chemotherapy. Further studies in combination with granulocyte colony-stimulating factor in patients with lymphoid malignancies are warranted.

The enhanced in vitro hematopoietic activity of leridistim, a chimeric dual G-CSF and IL-3 receptor agonist

The in vitro activity of leridistim was characterized for cell proliferation, generation of colony-forming units (CFU) and differentiation of CD34+ cells. In AML-193.1.3 cells, leridistim exhibited a significant increase in potency compared to rhG-CSF, SC-65303 (an IL-3 receptor agonist) or an equimolar combination of rhG-CSF and SC-65303. CFU-GM assays demonstrated that at 50% of the maximum response, the relative potency of leridistim was 12-fold greater than the combination of rhG-CSF and rhIL-3 and 44-fold more potent than rhG-CSF alone. In multi-lineage CFU assays, a combination of erythropoietin (rhEPO) and leridistim resulted in greater numbers of BFU-E, CFU-GEMM and CFU-Mk than rhEPO alone. Ex vivo culture of peripheral blood or bone marrow CD34+ cells with leridistim substantially increased total viable cells over cultures stimulated with rhG-CSF, SC-65303, or a combination of rhG-CSF and SC-65303. Culture with leridistim, resulted in a greater increase in myeloid (CD15+/CD11b+), monocytic (CD41-/CD14+) and megakaryocytic (CD41+/CD14-) precursor cells without depleting the progenitor pool (CD34+/CD15-/CD11b-). These results demonstrate that leridistim is a more potent stimulator of hematopoietic proliferation and differentiation than the single receptor agonists (rhG-CSF and SC-65303) either alone or combined. These unique attributes suggest that leridistim may enhance hematopoietic reconstitution following myelosuppressive chemotherapy.