ALBERT

Description: Background: AMD3100 (AMD or plerixafor) inhibits the binding of SDF-1 to its cognate receptor CXCR4 resulting in the rapid mobilization of CD34+ hematopoietic progenitor cells into the peripheral circulation. A prior phase I study suggested peak CD34+ cell mobilization occurred 6–8 hours following a 240 mcg/kg dose of AMD. This investigation provides preliminary data on the safety and CD34+ cell mobilizing effects of doses up to 480 mcg/kg of AMD. Methods: To account for inter-subject variability, subjects in three cohorts received two different subcutaneous doses of AMD. Healthy volunteers received the following doses of AMD: 240 mcg/kg and 320 mcg/kg (cohort 1); 320 mcg/kg and 400 mcg/kg (cohort 2); and 400 mcg/kg and 480 mcg/kg (cohort 3). Subjects received the higher dose at least 14 days after the first to allow adequate wash-out of AMD. The absolute number of circulating CD34+ cells were measured after each dose at the following times: 0, 2, 4, 6, 8, 10, 12, 14, 18, and 24 hours. In addition, this study assessed the following parameters: adverse events, AMD pharmacokinetics (400 and 480 mcg/kg doses), cytokine polarization status (Th1 vs Th2) of AMD mobilized CD3+ T-cells, and endothelial progenitor cell measurements. Results: To date, 16 of the planned 18 subjects have been enrolled on study with final results available for the first two cohorts; preliminary results exist for four subjects in the third cohort (400 mcg/kg vs 480 mcg/kg dose). Common toxicities include diarrhea, nausea, sinus tachycardia, injection site redness, perioral paresthesias, and headache. No dose limiting toxicities were observed; however, the frequency and/or magnitude of headache, nausea, vomiting, diarrhea, and tachycardia were greater at the 400 mcg/kg dose. Table 1 summarizes the preliminary CD34+ mobilization results for the 240, 320, and 400 mcg/kg doses. The lines in figures 1 and 2 show the difference in an individual subjects peak CD34+ cell number mobilized following 2 different doses of AMD. Conclusion: Although this phase I study is ongoing, preliminary data suggest doses of AMD higher than 240 mcg/kg may improve the peak numbers of CD34+ cells mobilized into the circulation. Furthermore, although dose escalation continues, the adverse events observed after a 400 mcg/kg dose of AMD appear similar to those observed after lower doses; no grade 3 or 4 adverse events have been observed. The final study results will provide additional data on the dose of AMD that optimizes CD34+ cell and CFU-GM mobilization for both autologous and allogeneic hematopoietic stem cell collections. CD 34+ cell mobilization 240 mcg/kg 320 mcg/kg 400 mcg/kg *Two subjects in 400 mcg dose group had the same peak mobilization time at two time points: these were averaged Number of subjects 6 12 10 Mean mobilized CD34 cells/microliter 27 29 31 Standard deviation of CD34 cells/microliter 13 14 13 Average peak mobilization time in hours* 9 10 11 Range of peak mobilization times in hours 8−14 6−14 8−18 Figure Figure

Description: The graft-versus-leukemia (GVL) effect following allogeneic stem cell transplantation (SCT) is evidence that T lymphocytes can eradicate leukemia. The successful identification of a range of leukemia-associated antigens such as proteinase 3 (PR3) and Wilms tumour-1 (WT1) has stimulated efforts to induce leukemia-specific T-cell responses to these antigens using peptide vaccines. Here we describe the safety and immunogenicity of a combined vaccine of two leukemia-associated antigenic peptides, PR1 and WT1. Eight HLA-A*0201 positive patients with myeloid malignancies (2 myelodysplasia, 5 acute myeloid leukemia and 1 chronic myeloid leukemia) received one subcutaneous dose each of PR1 and WT1 vaccines in Montanide adjuvant, with granulocyte-macrophage colony-stimulating factor (GM-CSF). All patients completed 4 weeks follow-up to monitor toxicity and immunological responses. Toxicity was limited to grade 1–2. All remain alive at a median of 252 days (range 105–523). We analyzed the immunological response to vaccination using PR1/HLA-A*0201 and WT1/HLA-A*0201 tetrameric complexes and flow cytometry for intracellular interferon-gamma (IFN-γ) in samples obtained pre- and weekly post-vaccination. A significant CD8+ T-cell response to the vaccine was defined as the emergence of PR1 or WT1-specific CD8+ T-cells when the pre-study analysis was negative or a twofold increase in frequencies when responses were present pre-vaccination. Following vaccination, a significant CD8+ T-cell response to PR1 was seen in 7/8 patients (median 0.34%, range 0.04–0.48%), to WT1 in 5/8 patients (median 0.29%, range 0–0.42%) and to one or both antigens in 8/8 patients. Vaccine-induced CD8+ T-cells were seen as early as 1 week post-vaccination, produced IFN-γ and were preferentially expanded in the effector compartment (CD45RO+/-CD27−). Post-vaccination, there was a strong correlation between the emergence of PR1 or WT1+CD8+ T-cells and a reduction in WT1 mRNA expression, a marker of minimal residual disease, suggesting a vaccine-driven anti-leukemia effect. Loss of response was associated with reappearance of WT1 transcripts (P