Peripheral blood progenitor cell transplantation in 118 patients with hematological malignancies: analysis of factors affecting the rate of engraftment

The effect of increased collect pump rate on collection efficiency in hematopoietic progenitor cell collection by apheresis in allogeneic adult donors-A single center analysis

BACKGROUND

Optimizing CD34 recovery while minimizing harm to hematopoietic progenitor cell donors by apheresis (HPC(A) donors) is critical to the success of allogeneic hematopoietic cell transplantation. We examined the efficacy and safety of starting allogeneic HPC(A) donors at a collect pump rate (CPR) of 2 mL/min on the Spectra Optia regardless of the inlet flow rate and/or pre-apheresis white blood cell (WBC) count (high CPR group).

STUDY DESIGN AND METHODS

A single-center retrospective study was performed on allogeneic adult donors from 10/2020 to 12/2022. From 10/2020 to 6/19/2022, all donors had CPR of ~1 mL/min (historical group). High CPR group started 6/20/2022.

RESULTS

During the study period, 412 donors were in historical group versus 196 (32.2%) in high CPR group. Median CD34 collection efficiency (CE) was higher and more consistent in high CPR group (55.1% vs. 53% in historical group, p < .0001) and remained significant in multivariate analysis. Although product volume was higher in high CPR group, WBC, hematocrit, and platelet concentrations were significantly lower. No difference in engraftment outcomes in patients receiving products from two groups was observed. Moreover, no differences occurred in a significant peri-procedural adverse event or percent decrease in platelets (6.87% decrease in platelets per 100 × 106 CD34 cells collected versus 6.66% in historical group, p = .89). Furthermore, high CPR group had ~26 min less in collection time for every 100 × 106 CD34 cells collected, resulting in less positive fluid balances.

CONCLUSIONS

Starting allogeneic HPC(A) donor collection at a CPR of 2 mL/min is safe and effective.

Repopulating hematopoietic stem cells from steady-state blood before and after ex vivo culture are enriched in the CD34+CD133+CXCR4low fraction

The feasibility of ex vivo expansion allows us to consider the steady-state peripheral blood as an alternative source of hematopoietic stem progenitor cells for transplantation when growth factor-induced cell mobilization is contraindicated or inapplicable. Ex vivo expansion dramatically enhances the in vivo reconstituting cell population from steady-state blood. In order to investigate phenotype and the expression of homing molecules, the expression of CD34, CD133, CD90, CD45RA, CD26 and CD9 was determined on sorted CD34⁺ cells according to CXCR4 (“neg”, “low” “bright”) and CD133 expression before and after ex vivo expansion. Hematopoietic stem cell activity was determined in vivo on the basis of hematopoietic repopulation of primary and secondary recipients - NSG immuno-deficient mice. In vivo reconstituting cells in the steady-state blood CD34⁺ cell fraction before expansion belong to the CD133⁺ population and are CXCR4^low or, to a lesser extent, CXCR4^neg, while after ex vivo expansion they are contained only in the CD133⁺CXCR4^low cells. The failure of the CXCR4^bright population to engraft is probably due to the exclusive expression of CD26 by these cells. The limiting-dilution analysis showed that both repopulating cell number and individual proliferative capacity were enhanced by ex vivo expansion. Thus, steady-state peripheral blood cells exhibit a different phenotype compared to mobilized and cord blood cells, as well as to those issued from the bone marrow. These data represent the first phenotypic characterization of steady-state blood cells exhibiting short- and long-term hematopoietic reconstituting potential, which can be expanded ex vivo, a sine qua non for their subsequent use for transplantation.

Peripheral blood stem cell mobilization failure

Autologous hematopoietic stem cell transplantation (HSCT) is an important and often life saving treatment for many hematological malignancies and selected solid tumors. To rescue hematopoiesis after high-dose chemotherapy in autologous HSCT depends on maintaining sufficient stem cells. Hematopoietic stem cells and progenitor cells expressing CD34 in the BM are mobilized into the circulation with granulocyte-colony stimulating factor ± chemotherapy prior to autologous HSCT. One of the most important factors for success of autologous HSCT is hematopoietic stem cell (HSC) count. Minimum threshold for the engraftment of hematopoietic cells is accepted as 2 × 10(6) CD34 + cells/kg especially for platelet engraftment. Below this level it is defined as stem cell mobilization failure. There are several factors affecting stem cell mobilization: prior chemotherapy (such as fludarabine, melphalan, lenalidomide) and radiotherapy, age, type of disease, bone marrow cellularity. We tried to summarize the reasons of peripheral stem cell mobilization failure.

Advances in stem cell mobilization

Use of granulocyte colony stimulating factor (G-CSF)-mobilized peripheral blood hematopoietic progenitor cells (HPCs) has largely replaced bone marrow (BM) as a source of stem cells for both autologous and allogeneic cell transplantation. With G-CSF alone, up to 35% of patients are unable to mobilize sufficient numbers of CD34 cells/kg to ensure successful and consistent multi-lineage engraftment and sustained hematopoietic recovery. To this end, research is ongoing to identify new agents or combinations which will lead to the most effective and efficient stem cell mobilization strategies, especially in those patients who are at risk for mobilization failure. We describe both established agents and novel strategies at various stages of development. The latter include but are not limited to drugs that target the SDF-1/CXCR4 axis, S1P agonists, VCAM/VLA-4 inhibitors, parathyroid hormone, proteosome inhibitors, Groβ, and agents that stabilize HIF. While none of the novel agents have yet gained an established role in HPC mobilization in clinical practice, many early studies exploring these new pathways show promising results and warrant further investigation.

Hematopoietic stem and progenitor cell mobilization in mice

Hematopoietic stem cell transplantation (HSCT) can be performed with hematopoietic stem and progenitor cells (HSPC) acquired directly from bone marrow, from umbilical cord blood or placental tissue, or from the peripheral blood after treatment of the donor with agents that enhance egress of HSPC into the circulation, a process known as "mobilization." Mobilized peripheral blood stem cells (PBSC) have become the predominate hematopoietic graft for HSCT, particularly for autologous transplants. Despite the success of PBSC transplant, many patients and donors do not achieve optimal levels of mobilization. Thus, accurate animal models and basic laboratory investigations are needed to further investigate the mechanisms that lead to PBSC mobilization and define improved or new mobilizing agents and/or strategies to enhance PBSC mobilization and transplant. This chapter outlines assays and techniques for exploration of hematopoietic mobilization using mice as a model organism.

Predictive factors for rapid neutrophil and platelet engraftment after allogenic peripheral blood stem cell transplantation in patients with acute leukemia

The aim of this study was to investigate predictive factors for rapid engraftment after allogeneic peripheral blood stem cell transplantation (alloPBSCT) in patients with acute leukemia. Two hundred sixty-two patients receiving alloPBSCT were analyzed. Subset analyses of donor stem cells were conducted using a flow cytometric method. The correlation between rapid engraftment of neutrophils, platelets, and donor stem cells doses, as well as other recipient and donor clinical factors, was analyzed. In univariate analysis, factors correlated with neutrophil engraftment (≥0.5 × 10(9)/L) by day 12 were achievement of complete remission (CR) after induction chemotherapy (CR1) before hematopoietic cell transplantation (HCT) and high numbers of CD34+ cells, CD3+ T cells, and CD3+/CD4+ T cells. Factors correlated with platelet engraftment (≥20 × 10(9)/L) by day 12 were achievement of CR1 before HCT, donor and recipient sex mismatch, and high numbers of mononuclear cells, CD34+ cells, CD3+ T cells, CD3+/CD4+ T cells, CD3+/CD8+ T cells, and CD56+ NK cells. In multivariate analysis, independent predictive factors for rapid neutrophil and platelet engraftment were CR1 before HCT (p < 0.001 and p = 0.002, respectively), high number of donor CD34+ cells (p = 0.005 and p < 0.001, respectively), and high number of CD3+ T cells (p = 0.005 and p = 0.001, respectively). In conclusion, achieving CR1 before HCT, as well as larger quantities of donor CD34+ and CD3+ T cells, may predict rapid neutrophil and platelet engraftment after PBSCT.

Chemokines and adult bone marrow stem cells

The adult bone contains a number of distinct populations of stem cells, including haematopoietic stem cells, mesenchymal stem cells, endothelial progenitor cells and fibrocytes. While haematopoietic stem cells are required to provide a lifelong supply of blood cells it is thought that the other populations of stem cells play a role in tissue regeneration and potentially disease. The chemokine CXCL12 is produced constitutively in the bone marrow and, acting via CXCR4, is critical in maintaining HSPCs in a quiescent state and retaining all subsets of stem and progenitor cells in the bone marrow environment. The cytokine G-CSF, used clinically to mobilize haematopoietic stem cells for bone marrow transplants, activates the sympathetic nervous system and bone marrow macrophages to reduce the expression of CXCL12 by bone marrow stromal cells, thereby promoting the exit of haematopoietic stem cells from the bone marrow. Understanding the molecular mechanisms underlying G-CSF stimulated mobilization has led to development of CXCR4 antagonists as fast acting mobilizing agents for haematopoietic stem cells. Evidence now suggests that CXCR4 antagonists can similarly mobilize distinct subsets of progenitor cells, namely the endothelial progenitor cells and mesenchymal stem cells, but this requires conditioning of the bone marrow with VEGF rather than G-CSF.

Advances in stem cell mobilization

The use of mobilized peripheral blood stem cells (PBSCs) has largely replaced the use of bone marrow as a source of stem cells for both allogeneic and autologous stem cell transplantation. G-CSF with or without chemotherapy is the most commonly used regimen for stem cell mobilization. Some donors or patients, especially the heavily pretreated patients, fail to mobilize the targeted number of stem cells with this regimen. A better understanding of the mechanisms involved in hematopoietic stem cell (HSC) trafficking could lead to the development of newer mobilizing agents and therapeutic approaches. This review will cover the current methods for stem cell mobilization and recent developments in the understanding of the biology of stem cells and the bone marrow microenvironment.

Predictive factors for poor peripheral blood stem cell mobilization and peak CD34(+) cell count to guide pre-emptive or immediate rescue mobilization

BACKGROUND AIMS

Failure in mobilization of peripheral blood (PB) stem cells is a frequent reason for not performing hematopoietic stem cell transplantation (HSCT). Early identification of poor mobilizers could avoid repeated attempts at mobilization, with the administration of pre-emptive rescue mobilization.

METHODS

Data from the first mobilization schedule of 397 patients referred consecutively for autologous HSCT between 2000 and 2010 were collected. Poor mobilization was defined as the collection of < 2 × 10(6) CD34(+)cells/kg body weight (BW).

RESULTS

The median age was 53 years (range 4-70) and 228 (57%) were males. Diagnoses were multiple myeloma in 133 cases, non-Hodgkin's lymphoma in 114, acute myeloid leukemia or myelodysplastic syndrome in 81, Hodgkin's lymphoma in 42, solid tumors in 17 and acute lymphoblastic leukemia in 10. The mobilization regimen consisted of recombinant human granulocyte-colony-stimulating factor (G-CSF) in 346 patients (87%) and chemotherapy followed by G-CSF (C + G-CSF) in 51 (13%). Poor mobilization occurred in 105 patients (29%), without differences according to mobilization schedule. Diagnosis, previous therapy with purine analogs and three or more previous chemotherapy lines were predictive factors for poor mobilization. A CD34(+)cell count in PB > 13.8/μL was enough to ensure ≥ 2 × 10(6) CD34(+)cells/kg, with high sensitivity (90%) and specificity (91%).

CONCLUSIONS

The prevalence of poor mobilization was high, being associated with disease type, therapy with purine analogs and multiple chemotherapy regimens. The threshold of CD34(+) cell count in PB identified poor mobilizers, in whom the administration of immediate or pre-emptive plerixafor could be useful to avoid a second mobilization.

High-dose therapy and autologous peripheral blood stem cell transplantation in patients with multiple myeloma

Since its introduction in 1983, high-dose therapy followed by autologous peripheral blood stem cell transplantation is a pillar of the treatment of patients with multiple myeloma. In the last decades, a multitude of clinical trials helped to improve strategies based on high-dose therapy and autologous stem cell transplantation resulting in a continuously prolongation of overall survival of patients. In this chapter we will review the progress, which has been made in order to enhance the mobilisation of autologous stem cells and increase the effectiveness of this treatment.

Update on clinical experience with AMD3100, an SDF-1/CXCL12-CXCR4 inhibitor, in mobilization of hematopoietic stem and progenitor cells

PURPOSE OF REVIEW

Mobilized peripheral blood stem cells are increasingly used for the reconstitution of hematopoiesis in autologous and allogeneic transplants. New agents and approaches are emerging to improve mobilization efficacy while reducing duration and toxicity of mobilization. The purpose of this review is to overview clinical experience with AMD3100 (plerixafor) and its role in stem cell mobilization.

RECENT FINDINGS

AMD3100 is a bicyclam molecule that selectively and reversibly antagonizes the binding of stromal cell-derived factor-1 (SDF-1) to its receptor CXC motif receptor-4 (CXCR4) with subsequent egress of hematopoietic stem cells to the peripheral blood. AMD3100 safely and rapidly mobilizes stem cells in patients with lymphoma, myeloma and healthy donors, and is synergistic in combination with granulocyte-colony stimulating factor. In addition, AMD3100 disrupts the interaction between mouse and human leukemic blasts and the bone marrow stroma, mobilizing blasts to the peripheral blood and sensitizing them to chemotherapy.

SUMMARY

AMD3100 was recently FDA-approved for stem cell mobilization in combination with granulocyte-colony stimulating factor in patients with non-Hodgkin's lymphoma and multiple myeloma. Studies are underway testing AMD3100 as an adjunct to chemotherapy in patients with refractory acute myelogenous leukemia (and other hematologic malignancies), as a strategy to sensitize leukemic cells to chemotherapy and improve clinical outcomes.

Impact of mobilization and remobilization strategies on achieving sufficient stem cell yields for autologous transplantation

The purpose of this article was to examine historic institutional autologous stem cell mobilization practices and evaluate factors influencing mobilization failure and kinetics. In this retrospective study we analyzed clinical records of 1834 patients who underwent stem cell mobilization for autologous transplantation from November 1995 to October 2006 at the Washington University in St. Louis. Successful mobilization was defined as collection of > or =2 x 10(6) CD34(+) cells/kg. From 1834 consecutive patients, 1040 met our inclusion criteria (502 non-Hodgkin's lymphoma [NHL], 137 Hodgkin's lymphoma, and 401 multiple myeloma [MM]). A total of 976 patients received granulocyte colony-stimulating factor (G-CSF) and 64 received G-CSF plus chemotherapy (G/C) for the initial mobilization. Although the median CD34(+) cell yield was higher in G/C group than in G-CSF alone group, the failure rates were similar: 18.8% and 18.6%, respectively. Overall, 53% of patients collected > or =2 x 10(6) CD34(+) cells/kg during the first apheresis with either mobilization regimen. Regardless of mobilization regimen used, MM patients had the highest total CD34(+) cell yield and required less aphereses to collect > or =2 x 10(6) CD34(+) cells/kg. Mobilized, preapheresis, peripheral blood CD34(+) count correlated with first day apheresis yield (r = .877, P < .001) and 20 cells/microL was the minimum threshold needed for a successful day 1 collection. For the remobilization analysis we included patients from the whole database. A total of 269 of 1834 patients underwent remobilization using G/C, G-CSF, and/or GM-CSF, and G-CSF plus plerixafor. Only 23% of remobilized patients achieved > or =2 x 10(6) CD34(+) cells/kg and 29.7% failed to pool sufficient number of stem cells from both collections. Patients receiving G-CSF plus plerixafor had lowest failure rates, P = .03. NHL patients remobilized with G-CSF who waited > or =25 days before remobilization had lower CD34(+) cell yield than those who waited < or =16 days, P = .023. Current mobilization regimens are associated with a substantial failure rate irrespective of underlying disease. Patients who fail initial mobilization are more likely to fail remobilization. These findings suggest that there is a need for more effective first-line mobilization agents.

Hematologic recovery after autologous PBPC transplantation: importance of the number of postthaw CD34+ cells

BACKGROUND

The implementation of a quality-assurance program is a major requirement to ensure quality and safety of the final PBPC components intended for clinical use. It is not clear whether the quantification of CFU-GM and CD34+ cells should be done on fresh components and after cryopreservation, which better represents the actual composition of the graft.

STUDY DESIGN AND METHODS

Correlation between prefreeze and postthaw MNCs, CD34+ cells, and CFU-GM collected from 126 patients undergoing BMT (n=43) or PBPC (n =83) transplantation were evaluated. The statistical incidence of prefreeze and postthaw parameters as well as patient characteristics and conditioning regimens on hematologic recovery were analyzed.

RESULTS

By multivariate analysis, prefreeze and postthaw CD34+ cells were the only two variables significantly and independently correlated to hematologic recovery. Low prefreeze and postthaw CD34+ cell numbers associated to a low CD34+ yield characterize PBPC grafts from patients who have the slowest hematologic recovery. The postthaw PBPC CD34+ cell number can be estimated before conditioning regimen by thawing a small aliquot of the graft.

CONCLUSION

In association to prefreeze CD34+ cell number and to CD34+ yield, postthaw CD34+ cell number may be useful in monitoring cell loss during processing and identifying patients at risk of slow PBPC engraftment.

Long-term hematologic reconstitution after autologous peripheral blood progenitor cell transplantation: a comparison between controlled-rate freezing and uncontrolled-rate freezing at 80 degrees C

BACKGROUND

The most widely used system for peripheral blood progenitor cell (PBPC) cryopreservation is controlled-rate freezing (CRF). Uncontrolled-rate freezing (URF) at -80 degrees C has also been used, but its clinical impact has not been studied sufficiently yet.

STUDY DESIGN AND METHODS

Two groups of patients were compared: Group A consisted of 69 patients autotransplanted with PBPCs cryopreserved with CRF; Group B consisted of 192 patients autotransplanted with PBPCs cryopreserved with URF at -80 degrees C. The same cryoprotectant solution and storage system were used.

RESULTS

A significant delay of hematologic reconstitution (HR) in the URF group was observed for neutrophils greater than 0.5 x 10(9) per L and for platelets greater than 20 x 10(9) per L and greater than 50 x 10(9) per L; we did not observe any differences in the clinical course. The long-term HR was comparable in the two groups, all patients showed stable engraftment, and no late graft failures were observed.

CONCLUSION

Our study confirms that URF is safe and allows sustained long-term engraftment without increasing the risks of transplantation, even though the early engraftment after URF is slower.

Bone Marrow Transplantation: Prognostic Factors of Peripheral Blood Stem Cell Mobilization with Cyclophosphamide and Filgrastim (r-metHuG-CSF): The CD34+ Cell Dose Positively Affects the Time to Hematopoietic Recovery and Supportive Requirements after High-Dose Chemotherapy

To prospectively analyze factors that influence peripheral blood stem cell (PBSC) collection and hematopoietic recovery after high-dose chemotherapy (HDC), 39 patients received cyclophosphamide 4 g/m(2) and rHuG-CSF (Filgrastim) 5 &mgr;g/kg/day. Leukapheresis was started when CD34(+) cells/mL were > 5 x 10(3). A minimum of 2 x 10(6) CD34(+) cells/kg was collected. Median steady-state bone marrow CD34(+) cell percentage was 0.8% (range, 0.1 to 6). Thirty-two patients received HDC with autologous PBSC transplantation plus Filgrastim. A median of 2 (range, 0 to 6) leukapheresis per patient were performed and a median of 6.3 x 10(6) CD34(+) cells/kg (range, 0 to 44.4) collected; four patients failed to mobilize CD34(+) cells. The number of cycles of prior chemotherapy had an inverse correlation with the number CD34(+) cells/kg collected (r = -0.38; p < 0.005). Patients with <7 cycles had a higher predictability for onset of leukapheresis than patients with (3) 7 (93% versus 50%; p < 0.005). The four patients who failed to mobilize had received >/=7 cycles. The number of CD34(+) cells/kg infused after HDC had an inverse correlation with days to recovery to 0.5 x 10(9) neutrophils/L and 20 x 10(9) platelets/L (r = -0.68 and -0.56; p < 0.005). The effect of these factors on mobilization and hematopoietic recovery were confirmed by multivariate analysis. Requirements for supportive measures were significantly lower in patients given a higher dose of CD34(+) cells/kg. Therefore, PBSC collection should be planned early in the course of chemotherapy. Larger number of CD34(+) cells/kg determined a more rapid hematopoietic recovery and a decrease of required supportive measures.

The effects of prior induction therapy with melphalan on subsequent peripheral blood progenitor cell transplantation for myeloma

High dose chemoradiotherapy with autologous peripheral blood progenitor cell transplantation (PBPCT) may improve outcome in myeloma. Melphalan is an effective drug in the treatment of myeloma, but is potentially toxic to progenitor cells. We studied 8 patients receiving intermittent intravenous melphalan (25 mg/m2) as induction therapy before PBPCT to assess engraftment characteristics post-transplantation. Comparison was made with an age-matched control group of patients with non-Hodgkins lymphoma who had not received melphalan during induction therapy. There was correlation (P=0.037) between the dose of melphalan per kg body weight given, premobilization, and days to neutrophil engraftment, but no significant difference between the two groups in neutrophil recovery. The study group had delayed platelet recovery (P=0.01) and required more platelet support post-transplantation (P=0.05). 3-4 weekly melphalan (25 mg/m2) up to 6 courses was delivered to patients who went on to PBPCT without significantly influencing neutrophil recovery but with a negative impact on platelet recovery.

A European reference protocol for quality assessment and clinical validation of autologous haematopoietic blood progenitor and stem cell grafts

Recently, the regulatory authorities have begun to show interest in haematopoietic stem cell products. On a professional rather than a regulatory basis, the International Society for Hematotherapy and Graft Engineering (ISHAGE) has established the Foundation for the Accreditation of Haematopoietic Cell Therapy (FACHT), which has drawn up guidelines for standards and accreditation of such activity. In Europe, the regulatory environment with regard to haematopoietic stem cell grafts, processing and storage are currently less stringent. However, in 1998 the European Joint Accreditation Committee Euro-ISHAGE/EBMT (JACIE) prepared a regulatory document 'Standards for Blood and Marrow Progenitor Cell Collection, Processing and Transplantation' which was approved by the EBMT General Assembly. The major objectives were to promote quality of medical and laboratory practice in haematopoietic progenitor cell transplantation. The standards extend and detail the pre-existing activity of EBMT centres including all phases of collection, processing and administration of these cells. This is the platform for the proposed reference protocol for CD34(+) cell enumeration and clinical validation of quality assessment to ensure that appropriate standards of work and product quality are established and will be maintained.

The role of cytokines and adhesion molecules for mobilization of peripheral blood stem cells

CD34(+) hematopoietic stem cells from peripheral blood are commonly used for autologous or allogeneic transplantation following high-dose therapy in malignant diseases. The introduction of hematopoietic growth factors such as G-CSF has greatly facilitated the mobilization of CD34(+) cells. The mechanism of stem cell mobilization is not yet clear. It seems to be a multistep process with a crosstalk between cytokines and adhesion molecules. In this review, the role of hematopoietic growth factors, chemokines, and adhesion molecules for mobilization and homing of CD34(+) cells is summarized. In addition, factors influencing the cytokine-induced mobilization in patients and healthy donors are described. The review closes with an overview of new classes of mobilizing drugs such as monoclonal antibodies, specific peptides, or antisense oligonucleotides targeting adhesion molecules.

Phase 1 study of pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) in breast cancer patients after autologous peripheral blood progenitor cell (PBPC) transplantation

Forty-seven patients with stage II, III, or IV breast cancer undergoing autologous peripheral blood progenitor cell (PBPC) transplantation were randomized to placebo (n = 13) or to one of five sequential dose cohorts of pegylated (PEG) recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) (1.0, 2.5, 5.0, 7.5, or 10.0 microg/kg/day) (n= 34). Blinded study drug was started on the day of transplantation and was continued until the platelet count was > or =100 x 109/l or a maximum of 21 days. PBPCs were mobilized with filgrastim (r-metHuG-CSF) and all patients received filgrastim starting on day +2 after transplantation. The nadir platelet count was not affected by treatment. The median time to platelet recovery was 11 and 12 days for the placebo and combined PEG-rHuMGDF groups, respectively. No trends in adverse events suggested dose- or treatment-related toxicity. Two patients withdrew from the study because of an adverse event (allergic reaction in the 7.5 microg/kg group) probably related to study drug, and veno-occlusive disease (VOD) (in the 5 microg/kg group) which was felt not to be related to study drug by the investigator. No patients developed neutralizing antibodies to MGDF. Day +21 and day +28 platelet counts were higher in the group receiving PEG-rHuMGDF (246 vs 148 x 109/l and 299 vs 145 x 109/l, respectively; both P < 0. 05). PEG-rHuMGDF up to 10 microg/kg/day was well tolerated. In this study, there was no effect of study drug on initial platelet engraftment at the doses studied. However, the efficacy of other doses is unknown.

Differential effects of IL-2 incubation on hematopoietic potential of autologous bone marrow and mobilized PBSC from patients with hematologic malignancies

Culturing of hematopoietic progenitor cells for 24 h with IL-2 generates cytotoxic effector cells that mediate in vitro and possibly in vivo antitumor activity. We examined the effect of IL-2 incubation on progenitor cells from 24 patients with hematologic malignancies using paired autologous bone marrow (ABM) and PBSC to determine differences in hematopoietic potential. Cells were cryopreserved and stored in liquid nitrogen until conditioning therapy was completed. After thawing, cells were incubated with IL-2 for 24 h at 37 degrees C. Paired samples of ABM and PBSC from the same patient were analyzed for nucleated and mononuclear cell number, CD34 antigen expression, and colony-forming unit (CFU) activity before and after IL-2 incubation. There was a significant decrease in the average number of mononuclear cells (MNC) (x10(8)/kg) (<0.001) and CD34+ cells (x10(6)/kg) (0.006) from both ABM and PBSC after 24 h IL-2 culture (ABM MNC: 0.6+/-0.1 vs. 0.4+/-0.0, p = <0.001; PBSC MNC: 4.4+/-0.5 vs. 3.7+/-0.4, p = 0.03; ABM CD34+: 2.4+/-0.5 vs. 1.3+/-0.3, p = <0.001; PBSC CD34+: 6.6+/-1.8 vs. 5.0+/-1.2, p = 0.05). However, whereas ABM CFU/10(5) MNC plated (269.3+/-47.2 vs. 385.6+/-70.6) were significantly increased (p = 0.005), there was no change in PBSC CFU (271.0+/-47.2 vs. 257.3+/-48.5). The mean plating efficiency (%) of ABM CD34+ cells was markedly increased after IL-2 incubation (10.1+/-3.3 vs. 19.0+/-7.2, p = 0.04), although it was lower than that of PBSC CD34+ cells, which did not change significantly in culture (29.4+/-5.5 vs. 36.0+/-6.5). Additional work is in progress to determine the cause and significance of the enhanced plating efficiency of the ABM progenitor cells.

Daily measurements of blood CD34+ cells after stem cell mobilization predict stem cell yield and posttransplant hematopoietic recovery

The value of daily monitoring of the blood CD34+ cell concentration as a guide to the optimal timing of stem cell harvests was studied in 60 patients who underwent 66 stem cell mobilizations and 189 leukaphereses. There was a highly significant correlation between the blood CD34+ count and the CD34+ cell content in the apheresis product of the same day (r = 0.904, p < 0.01). Thus, the target yield of 4 x 10(6) CD34+ cells/kg can be harvested in one or two leukaphereses when the blood CD34+ cell count exceeds 50 x 10(6)/L. However, an insufficient harvest is to be expected when the blood CD34+ cell count is below 20 x 10(6)/L. The data from 35 autologous blood cell transplantations with a minimum CD34+ cell yield of 1.5 x 10(6)/kg showed that the recovery of blood neutrophil counts to 1.0 x 10(9)/L occurred in all patients within 9-14 days, but the time to recovery of the platelet counts to 20 x 10(9)/L may exceed 14 days, especially if the CD34+ cell content is below 4 x 10(6)/kg. Daily monitoring of blood CD34+ cell counts is a rapid and reliable means to guide the timing of stem cell collections. The count predicts well the CD34+ cell content of the harvests, the number of leukaphereses needed, and the speed of hematopoietic recovery.

Autologous transplantation of blood stem cells mobilized with filgrastim alone in 93 patients with malignancies: the number of CD34+ cells reinfused is the only factor predicting both granulocyte and platelet recovery

High-dose chemotherapy (HDC) supported by autologous transplantation of blood stem cells (BSC) is used increasingly for patients with poor-risk malignancies. We report our experience with 93 consecutive patients who were mobilized with recombinant human granulocyte colony-stimulating factor (rhG-CSF) alone. They received a fixed dose of G-CSF for 5 or 6 days, and BSC were collected by leukapheresis. Aphereses were evaluated for MNC, CD34+ cells, and CFU-GM counts and cryopreserved. All patients received a conditioning regimen without TBI. Engraftment was assessed as the first of 2 consecutive days on which patients achieved 0.5 and 1 x 10(9)/L neutrophils and an unsupported platelet count of 25 x 10(9)/L. Multivariate analysis was performed to study patients and graft characteristics that could influence reconstitution. The G-CSF priming regimen was well tolerated and allowed collection of BSC for all patients, 66% of them achieving >3 x 10(6)/kg CD34+ cells, and 86% achieving >10 x 10(4) CFU-GM/kg. The numbers of collected CD34 and CFU-GM cells were highly correlated. The number of courses of chemotherapy prior to collection, a diagnosis of breast cancer, the use of rhG-CSF posttransplant, and the numbers of CFU-GM and CD34+ cells reinfused were correlated with hematologic recovery. In a multivariate analysis, however, the number of CD34+ cells was the only factor independently influencing both granulocyte and platelet recovery. Patients who received at least 3 x 10(6)/kg CD34+ cells achieved granulocyte reconstitution on day 11 after reinfusion (range 8-15) and an unsupported platelet count of 25 x 10(9)/l on day 14 (range 12-180), significantly earlier than patients who received fewer cells (p < 0.001). In addition, G-CSF administration postreinfusion independently enhanced granulocyte reconstitution but not platelet recovery. In conclusion, CD34+ cell number appears to be the only factor predicting both granulocyte and platelet reconstitution. Based on this study, the collection of a minimal number of 3 x 10(6)/kg CD34+ cells appears desirable.

Comparison of the content and subpopulations of CD3 and CD34 positive cells in bone marrow harvests and G-CSF-mobilized peripheral blood leukapheresis products from healthy adult donors

Recombinant human granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood stem/progenitor cells (PBPC) have replaced bone marrow (BM) harvests for autologous transplantation after myeloablative therapy in cancer patients. G-CSF-mobilized PBPC from healthy donors contain one log excess of T lymphocytes representing a potential risk for graft-versus-host disease (GVHD). However, recent pilot clinical studies of G-CSF-mobilized allogeneic PBPC transplantation have shown rapid haematological recovery and no severe acute GVHD except in a very few cases. Therefore, the risk of inducing severe acute GVHD is not as high as was expected during the pioneering period of allogeneic PBPC transplantation. The present study was performed to address the possible reasons for the rapid haematological recovery and the absence of severe acute GVHD observed after allogeneic PBPC transplantation by comparing the contents and subsets of CD3+ and CD34+ G-CSF-mobilized PBPC (n = 31) with those of BM (n = 26) allografts from healthy adult donors. The present results revealed that the phenotypic profiles of CD3+ and CD34+ cells differ between PBPC and BM allografts. The single PBPC leukapheresis product contained 10 times more mononuclear cells, 1.5 times more CD34+ cells, 5.5 times more CD3+ T lymphocytes, 3 times more CD19+ B lymphocytes and 3.8 times more CD14+ monocytes than the single BM harvest. Both CD34+CD33+ myeloid progenitor cells and CD34+HLA-DR-long-term reconstituting haemopoietic stem cells were significantly increased in the CD34+ G-CSF-mobilized PBPC compared with the CD34+ BM cells; median 73.1% and 30.4% vs 60.6% and 5.0%, respectively, P < 0.01. The percentage of CD3+ cells coexpressing CD4 (T helper/inducer) was similar in both PBPC and BM allografts, 47.2% and 45.6%, respectively, whereas the percentage of CD3+ cells coexpressing CD8 (T suppressor/cytotoxic) was significantly decreased in PBPC compared with BM; 37.0% vs 55.9%, p < 0.01. The rapid haematological recovery after allogeneic PBPC transplantation could be due to the increased content of CD34+CD33+ myeloid committed cells and the CD34+HLA-DR-long-term reconstituting haemopoietic stem cells in the PBPC allografts. Also, the absence of an increased risk of severe acute GVHD after allogeneic PBPC transplantation could be due to the increased T lymphocyte ratio of CD4+/CD8+ in the PBPC allografts. In conclusion, rapid haematological recovery without an increased risk of severe acute GVHD can be achieved using G-CSF-mobilized PBPC rather than BM for allogeneic transplantation.

Thrombocytopenia after high-dose chemotherapy and autologous stem cell transplantation: an unresolved problem and possible approaches to resolve it

Prolonged thrombocytopenia is a frequent clinical problem in cancer patients undergoing high-dose chemotherapy and autologous transplantation. The use of GM-CSF as an adjuvant to autologous bone marrow transplantation (ABMT) has significantly reduced the duration of neutropenia after high-dose chemotherapy but failed to accelerate platelet recovery in transplanted patients. The more rapid hematopoietic reconstitution obtained by autologous mobilized peripheral blood progenitor cell transplantation (PBPCT) after high-dose chemotherapy has resulted in its increasing use instead of ABMT. However, PBPCT does not always produce faster platelet engraftment after high-dose chemotherapy, and persistent thrombocytopenia remains a significant clinical problem in PBPC-transplanted patients. The duration of severe thrombocytopenia (requiring frequent platelet transfusions) until platelet recovery varies widely depending on the quality of the autograft and previous radiotherapy or chemotherapy. The median days to reach 20,000/microliters platelets ranged from 10 to 32 days. Pilot clinical studies in which cancer patients were transplanted with enriched CD34+ cell autografts, obtained from G-CSF-mobilized PB, showed a similar platelet recovery after high-dose chemotherapy but also wide variation among the patients. The median days to reach 20,000/microliters platelets ranged from 9 to 38 days. The dose of CFU-GM in the autograft has been identified as the best predictive factor for hematopoietic recovery (p < 0.0001) after high-dose chemotherapy and autologous PBPCT in 118 patients with hematologic malignancies. A similar assessment of the megakaryocyte progenitor cells (BFU-MK and CFU-MK) in the autograft not only could predict time to platelet recovery but also could help to optimize the number and method of mobilization of the PBPC required to shorten the problematic obligatory 2-week duration of thrombocytopenia after high-dose chemotherapy. A routine assessment of the number of BFU-MK and CFU-MK present in each autograft and correlation with platelet recovery after transplantation would enable us to define the clinical threshold cell dose required for rapid platelet recovery. Recently, several non-specific cytokines with thrombopoietic activity have been evaluated in phase I clinical trials, including interleukin-1, interleukin-3 followed by GM-CSF, interleukin-6, and interleukin-11 in cancer patients, showing an encouraging trend toward a decrease in thrombocytopenia after chemotherapy. The recently cloned specific platelet cytokine, thrombopoietin, is currently undergoing phase I clinical studies, and the results are awaited with interest.

Peripheral blood stem cell transplantation in acute myeloid leukemia: the experience of the Bordeaux Group

Since our initial report of successful peripheral blood stem cell transplantation (PBSCT) in a patient with acute myeloid leukemia (AML), we have performed more than 300 PBSCTs; 49 of them were done for AML patients. PBSC mobilization (and collection) was influenced by the number of previous courses of chemotherapy and significantly increased when G-CSF was combined with chemotherapy for mobilization. Hematopoietic recovery (HR) was complete in every patient. The HR rate was influenced by the number of cells transplanted. Platelet recovery was significantly quicker for patients given G-CSF for mobilization. The outcome of patients transplanted in first or second remission was similar to that usually observed after bone marrow transplantation.

Rationale for high-dose chemotherapy and application of haematopoietic growth factors in acute myeloid leukaemia

High-dose chemotherapy in acute myeloid leukaemia (AML) is more effective and not associated with a higher risk of lethal complications during the induction phase as compared with less intensive regimens. This seemingly paradoxical finding is explained by the more rapid reduction of the leukaemic cell mass and the faster restoration of normal haematopoesis. In the most recent study on double induction therapy by the German AML Cooperative Group involving 665 adult patients with AML the rate of complete remission was 66%-73%. Haematopoietic growth factors used as part of the anti-tumour regimen offer a number of advantages. These include acceleration of haematopoietic recovery and the potential to enhance the sensitivity of leukaemic blasts when given prior to and during cytostatic therapy. New perspectives to further enhance the intensity of antileukaemic therapy may emerge from the introduction of peripheral stem cell transplantation into the treatment strategy.