A novel hematopoietic progenitor cell mobilization regimen, utilizing bortezomib and filgrastim, for patients undergoing autologous transplant

Bortezomib enhances G-CSF-induced hematopoietic stem cell mobilization by decreasing CXCL12 levels and increasing vascular permeability

Bortezomib (BTZ) is known to enhance the mobilization of hematopoietic stem and progenitor cells (HSPCs) induced by granulocyte colony-stimulating factor (G-CSF). However, the most effective time at which to administer BTZ to produce this enhancing effect remains debatable, and the precise mechanism underlying the effect of BTZ is poorly understood. We addressed these questions in this article by performing animal experiments. First, in agreement with previous studies, BTZ administration 12 hours before blood collection was most effective for HSPC mobilization; in contrast, BTZ administration 3 days before blood collection negatively affected HSPC harvesting. Next, in terms of the mechanism of action, G-CSF, but not BTZ, downregulated the expression of very late antigen-4 on HSPCs and vascular cell adhesion molecule-1 on bone marrow (BM) stromal cells; however, intriguingly, both G-CSF and BTZ downregulated CXCL12 chemokine expression in BM. Notably, BTZ treatment also increased BM vascular permeability. These results suggest that the pro-mobilization effect of BTZ could involve the dissociation of HSPCs from BM stromal cells triggered by G-CSF, vascular hyperpermeability elicited by BTZ, and downregulation of CXCL12 concomitantly induced by G-CSF and BTZ.

Presence of Promyelocytes in Peripheral Blood as a Novel Predictor of Optimal Timing for Single-Step Peripheral Blood Stem Cell Collection

BACKGROUND

Because peripheral blood stem cell (PBSC) collection places a burden on the patient and should ideally be completed in a single procedure, a convenient clinical predictive factor is needed.

METHODS

This retrospective study included 72 patients who underwent autologous PBSC collection. A median volume of 3.9 × 10⁶ CD34-positive cells/kg (range: 0.3-47.4 × 10⁶ cells/kg) was collected on the first day. We defined failure as inability to collect 2.0 × 10⁶ cells/kg on the first day. PBSC collection was classified as failed (n = 25, 34.7%) and successful (n = 47, 65.3%), and patient clinical characteristics were analyzed.

RESULTS

The success group had significantly more cases in which a differential white blood cell count in peripheral blood on the day of PBSC collection detected promyelocytes (n = 34 [72.3%] vs. n = 11 [44.0%] in the failure group; P = 0.008). Sixty-two patients underwent autologous PBSC transplantation (median number of transplanted cells, 5.6 × 10⁶/μL; range: 1.60-47.4 × 10⁶ cells/μL). Among transplanted patients, the success and failure groups did not significantly differ in relation to the interval until neutrophil, platelet, or red blood cell engraftment.

CONCLUSION

The presence of promyelocytes in peripheral blood may be a useful indicator of the optimal timing for single-step PBSC collection.

The impact of multiple myeloma induction therapy on hematopoietic stem cell mobilization and collection: 25-year experience

While first-line induction therapy for patients with multiple myeloma has changed over the years, autologous hematopoietic stem cell transplantation still plays a significant role, improving both depth of response and progression-free survival of myeloma patients. Our 25-year experience in mobilizing hematopoietic stem and progenitor cells for 472 transplant-eligible myeloma patients was retrospectively reviewed. Patients were stratified according to the remission induction therapy received, and the outcomes were compared among the cohorts that received vincristine, adriamycin and dexamethasone (VAD) (n = 232), bortezomib and dexamethasone (BD) (n = 86), cyclophosphamide, bortezomib and dexamethasone (CyBorD) (n = 82) and other regimens (n = 67). Cyclophosphamide plus granulocyte colony-stimulating factor was the predominant mobilization regimen given. A greater number of CD34⁺ cells (9.9 × 10E6/kg, p = 0.026) was collected with less hospital admissions in BD patients (13%, p = 0.001), when compared to those receiving VAD (7.5 × 10E6/kg, 29%), CyBorD (7.6 × 10E6/kg, 19%), or other regimens (7.9 × 10E6/kg, 36%). Induction therapy did not influence the overall rate of unscheduled visits or the length of hospitalization because of complications following mobilization. The myeloma response was not significantly deepened following the cyclophosphamide administered for mobilization. This analysis demonstrates the importance of monitoring the impact of initial treatment on downstream procedures such as stem cell mobilization and collection.

Comparison and cost analysis of three protocols for mobilization and apheresis of haematopoietic progenitor cells

INTRODUCTION

Autologous bone marrow transplantation is a component of the malignant hemopathy therapy. The preferred mobilization and collection method is apheresis. The aim of this study is to compare three protocols analyzing the effect of plerixafor, higher dose of G-CSF and large volume leukapheresis (LVL).

MATERIALS AND METHODS

A retrospective cohort study including 119 patients referred for mobilization. Three protocols were compared: (a) G-CSF 10 μg/kg/day subcutaneous (sc) × 4 days mobilizing 1 to 1.5 blood volumes. (b) G-CSF 10 μg/kg/day sc × 4 days + plerixafor 0.24 mg/kg/day sc preventively or as a rescue agent mobilizing 1 to 1.5 blood volumes. (c) G-CSF 20 μg/kg/day sc × 4 days ± plerixafor 0.24 mg/kg/day sc preventively or as a rescue agent mobilizing 3 to 4 blood volumes.

RESULTS

The average number of days of apheresis was reduced to 1.37 with protocol 3. The average cost per patient was reduced by 67% compared with protocol 2 and increased by only 5% compared with protocol 1, reducing the failure rate to 0%.

CONCLUSION

Adding preemptive or rescue plerixafor (protocol 2) to G-CSF 10 μg/kg/day alone (protocol 1) did not improve the days of apheresis nor the number of CD34+ cells collected but had higher cost and failure rate. Using LVL, plerixafor and G-CSF 20 μg/kg/day (protocol 3) decreased the number of sessions to 1.37, reduced the failure rate to 0% and led to a significant increase in the number of CD34+ cells collected without toxicity and with a similar cost to protocol 1.

New agents in HSC mobilization

Mobilized peripheral blood (PB) is the most common source of hematopoietic stem cells (HSC) for autologous transplantation. Granulocyte colony stimulating factor (G-CSF) is the most commonly used mobilization agent, yet despite its widespread use, a considerable number of patients still fail to mobilize. Recently, a greater understanding of the interactions that regulate HSC homeostasis in the bone marrow (BM) microenvironment has enabled the development of new molecules that mobilize HSC through specific inhibition, modulation or perturbation of these interactions. AMD3100 (plerixafor), a small molecule that selectively inhibits the chemokine receptor CXCR4 is approved for mobilization in combination with G-CSF in patients with Non-Hodgkin's lymphoma and multiple myeloma. Nevertheless, identifying mobilization strategies that not only enhance HSC number, but are rapid and generate an optimal "mobilized product" for improved transplant outcomes remains an area of clinical importance. In recent times, new agents based on recombinant proteins, peptides and small molecules have been identified as potential candidates for therapeutic HSC mobilization. In this review, we describe the most recent developments in HSC mobilization agents and their potential impact in HSC transplantation.