Pharmacoeconomic impact of up-front use of plerixafor for autologous stem cell mobilization in patients with multiple myeloma

Background aimsStem cell collection can be a major component of overall cost of autologous stem cell transplantation (ASCT). Plerixafor is an effective agent for mobilization; however, it is often reserved for salvage therapy because of its high cost. We present data on the pharmacoeconomic impact of the use of plerixafor as an up-front mobilization in patients with multiple myeloma (MM).MethodsPatients with MM who underwent ASCT between January 2008 and April 2011 at the Mount Sinai Medical Center were reviewed retrospectively. In April 2010, practice changes were instituted for patients with MM to delay initiation of granulocyte-colony-stimulating factor (G-CSF) support from day 0 to day +5 and to add plerixafor to G-CSF as an up-front autologous mobilization. Targets of collection were 5–10 × 10⁶ CD34⁺ cells/kg.ResultsOf 50 adults with MM who underwent ASCT, 25 received plerixafor/filgrastim and 25 received G-CSF alone as an up-front mobilization. Compared with the control, plerixafor mobilization yielded higher CD34⁺ cell content (16.1 versus 8.4 × 10⁶ CD34⁺ cells/kg; P = 0.0007) and required fewer sessions of apheresis (1.9 versus 3.1; P = 0.0001). In the plerixafor group, the mean number of plerixafor doses required per patient was 1.8. Although the overall cost of medications was higher in the plerixafor group, the cost for blood products and overall cost of hospitalization were similar between the two groups.ConclusionsUp-front use of plerixafor is an effective mobilization strategy in patients with MM and does not have a substantial pharmacoeconomic impact in overall cost of hospitalization combined with the apheresis procedure.     

The use of plerixafor in hematopoietic progenitor cell collection in pediatric patients: a single center experience

Background aimsPlerixafor was recently approved for use in combination with granulocyte–colony-stimulating factor (G-CSF) for hematopoietic progenitor cell (HPC) collection by apheresis in adults with multiple myeloma (MM) or non-Hodgkin lymphoma (NHL). However, its efficacy in pediatric patients is not well-studied; thus, we report on our institutional experience with this population. Methods. A retrospective observational analysis was performed using both stem cell-processing laboratory information as well as apheresis charts and medical records on all pediatric patients who received plerixafor as part of the mobilization regimen between December 2006 and December 2010. The primary outcome was collection yield. Secondary outcomes included the ability to undergo autologous hematopoietic stem cell transplantation (auto-HSCT) and engraftment status. Results. Eighteen HPC collections by apheresis representing seven mobilization courses were performed on five pediatric patients with poor mobilization status (three males, two females; median age 14 years). Median pre-harvest peripheral blood CD34⁺ cell (PB CD34⁺) count was 6.88/μL. A strong correlation between pre-harvest PB CD34⁺ count and collection yield was observed. Median total collection yield was 2.26 × 10⁶ CD34⁺ cells/kg. Four patients achieved a minimum collection of 2 × 10⁶ CD34⁺ cells/kg. Three patients underwent auto-HSCT with a median neutrophil and platelet engraftment of 12 and 34 days, respectively. No major adverse events with plerixafor administration or apheresis collections were reported. Conclusions. Plerixafor in combination with G-CSF is a safe and potentially helpful mobilization agent in poor mobilizers. Further studies should be done to evaluate the true efficacy of plerixafor in the pediatric population.     

Mobilization and engraftment of peripheral blood stem cells in healthy related donors >55 years old

Background aimsThe increasing scarcity of young related donors has led to the use of older donors for related allogeneic hematopoietic stem cell transplantation (HSCT). This study analyzed the influence of age on the results of mobilization of peripheral blood stem cells (PBSCs) in healthy donors as well as on the engraftment and outcome of HSCT.MethodsA retrospective analysis from a single center was performed comparing the results of PBSC mobilization from related healthy donors according to their age.ResultsThe study included 133 consecutive related donors. The median age was 50 years (range, 4–77 years); 70 (53%) donors were males, and 44 (33%) were >55 years old. All donors were mobilized with granulocyte colony-stimulating factor for 5 days. The peak CD34⁺ cell count in peripheral blood was higher in younger than in older donors (median, 90.5 CD34⁺ cells/μL [range, 18–240 CD34⁺ cells/μL] versus 72 CD34⁺ cells/μL [range, 20–172.5 CD34⁺ cells/μL], P = 0.008). The volume processed was lower in younger than in older donors (16,131 mL [range, 4424–36,906 mL] versus 18,653 mL [range, 10,003–26,261 mL], P = 0.002) with similar CD34⁺ cells collected (579.3 × 10⁶ cells [range, 135.14 × 10⁶–1557.24 × 10⁶ cells] versus 513.69 × 10⁶ cells [range, 149.81 × 10⁶–1290 × 10⁶ cells], P = 0.844). There were no differences in time to recovery of neutrophils and platelets or in the incidences of acute and chronic graft-versus-host disease, overall survival, non-relapse mortality and relapse incidence.ConclusionsDonors >55 years old mobilized fewer CD34⁺ cells and required a greater volume to collect a similar number of CD34⁺ cells. The outcome of HSCT was not influenced by donor age. Donor age should not be a limitation for related allogeneic HSCT.     

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

Background aimsFailure 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 mobilizationMethodsData 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 × 10⁶ CD34⁺cells/kg body weight (BW).ResultsThe 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 × 10⁶ CD34⁺cells/kg, with high sensitivity (90%) and specificity (91%).ConclusionsThe 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.     

Stem cell transplantation for metastatic breast cancer: analysis of tumor contamination

The purpose of this study was to determine the efficacy, engraftment kinetics, effect of bone marrow tumor contamination, and safety of high-dose therapy and granulocyte-colony stimulating factor (G-CSF) mobilized peripheral blood progenitor cell (PBPC) support for patients with responding metastatic breast cancer. Forty two patients underwent G-CSF (10 μg/kg) stimulated PBPC harvest. PBPC and bone marrow aspirates were analyzed by histologic and immunocytochemical methods for tumor contamination. Thirty-seven patients received high-dose therapy consisting of cyclophosphamide 6 g/m², thiotepa 500 mg/m², and carboplatin 800 mg/m² (CTCb) given as an infusion over 4 d followed by PBPC reinfusion and G-CSF (5 μg/kg) support. No transplant related deaths or grade 4 toxicity was recorded. CD34+ cells/kg infused was predictive of neutrophil and platelet recovery. With a median follow-up of 38 months, three year survival was 44% with relapse-free survival of 19%. Histological bone marrow involvement, found in 10 patients, was a negative prognostic factor and was associated with a median relapse-free survival of 3.5 months. Tumor contamination of PBPC by immunohistochemical staining was present in 22.5% of patients and found not to be correlated with decreased survival. G-CSF stimulated PBPC collection followed by a single course of high dose chemotherapy and stem cell infusion with G-CSF stimulated marrow recovery leads to rapid, reliable engraftment with low toxicity and promising outcome in women with responding metastatic breast cancer.     

Validation of a formula for predicting daily CD34(+) cell collection by leukapheresis

Background aimsThe ability to predict how many CD34⁺ cells a donor will collect on a given day is vital for efficient leukapheresis.MethodsWe validated a formula to predict daily CD34⁺ cell collections by leukapheresis, calculated as follows: (peripheral blood CD34⁺ cells/L) × (adjusted collection efficiency of 30%)/body weight (kg), multiplied by the number of liters processed. This validation was performed from 234 donors undergoing 30 L large volume leukapheresis (LVL) and 162 donors undergoing smaller collections (non-LVL). The LVL group consisted of 811 collection events (625 multiple myeloma, 186 non-myeloma). The non-LVL group consisted of 224 collection events (196 multiple myeloma, 28 non-myeloma). All predicted and observed CD34⁺ cell collection numbers were plotted (predicted versus observed) and assessed using linear regression analyses. Linear correlation coefficients (r-values), slopes and intercepts of the regression lines were evaluated.ResultsPredicted versus observed data points across all quantities of CD34⁺ cells/kg collected by both LVL and non-LVL had strong r-values of 0.947 and 0.913, respectively, demonstrating near perfect positive linear correlations. Data for LVL collections subgrouped by number of cells collected (poor, intermediate and good), mobilization regimen, collection day and diagnosis were analyzed the same way and showed consistent findings.ConclusionsWe have validated a formula with a strong ability to predict collection of CD34⁺ cells/kg that would allow for individualization of collection for any donor once the peripheral blood CD34⁺ cell count and optimal goal of collection were known; to date this has not been published by other groups.     

Comparison of two single-platform ISHAGE-based CD34 enumeration protocols on BD FACSCalibur and FACSCanto flow cytometers

Background aimsEnumeration of viable CD34⁺ cells provides critical information for the bone marrow (BM) transplant physician. The single-platform ISHAGE protocol is the most reliable method currently available to quantitate accurately this important subset of cells. Previous studies have shown that 5 CD34⁺ cells/µL blood predicts the collection of at least 0.5 × 10⁶ CD34⁺ cells/kg patient weight. From the apheresis product, infusion of 2.5 × 10⁶ viable CD34⁺ cells (measured pre-cryopreservation)/kg patient weight will reliably permit engraftment of the hematopoietic system (as measured by the time to 20000 platelets/µL) by day 12–14 post-infusion.MethodsWe compared the CD34⁺ cell numbers derived from Flow Count-based Stem-Kit?; (Beckman Coulter) and Trucount? tube-based stem cell enumeration (SCE) kit (BD Biosciences) ISHAGE templates on BD FACSCalibur? and BD FACSCanto? cytometers on 12 granulocyte–colony-stimulating factor (G-CSF)-mobilized peripheral blood (MPB) and 10 peripheral blood stem cell (PBSC) samples.ResultsComparison of results showed that there was no statistical difference between samples run with Stem-Kit on the FACSCalibur versus SCE kit-based assays on either the FACSCalibur or FACSCanto. Mean results for the Stem-Kit/Calibur combination were 137, for SCE kit/Calibur 140 and for SCE kit/Canto 137 cells/µL. Pair-wise comparison of data based on rank order showed no statistically significant difference and all correlation coefficients had an R²>0.98.ConclusionsThe two kits generated very similar data on a range of fresh samples regardless of instrument platform. These results confirm and extend the utility of the single-platform ISHAGE protocols with a variety of reagent kits and instrument platforms.     

Low baseline platelet count predicts poor response to plerixafor in patients with multiple myeloma undergoing autologous stem cell mobilization

Background aimsBaseline platelet count has been shown to be a sensitive predictor of autologous peripheral blood progenitor cell collection yield in patients with multiple myeloma mobilized with granulocyte colony-stimulating factor (G-CSF). Patients who mobilize poorly with G-CSF are often treated with plerixafor to enhance mobilization. There are no surrogate markers available to predict response to plerixafor.MethodsWe retrospectively analyzed data from 73 patients with multiple myeloma who did not have adequate mobilization with G-CSF alone and were treated with plerixafor as a rescue agent.ResultsWe found that baseline platelet count directly correlated with peripheral blood CD34⁺ (PB-CD34⁺) count after plerixafor treatment (r = 0.36, P < 0.0001) and the number of PB-CD34⁺ cells collected on the first day of apheresis and inversely correlated with the number of apheresis sessions needed to collect the target number of PB-CD34⁺ cells (P = 0.0015). Baseline platelet count of 153 000/µL or less was associated with 90% specificity of predicting poor response to plerixafor with a sensitivity of 33%.ConclusionsBaseline platelet count is a good predictor of mobilization response to plerixafor in patients with multiple myeloma.     

Anticoagulation in large-volume leukapheresis: comparison between citrate- versus heparin-based anticoagulation on safety and CD34 (+) cell collection efficiency

Background aimsLittle is known of the effect of anticoagulation on peripheral blood progenitor cell (PBPC) harvest during large-volume leukapheresis (LVL). Because of the interaction of heparin with stromal cell-derived factor (SDF)-1α, it has been proposed that a heparin-based anticoagulation may result in an increased PBPC collection efficiency compared with standard citrate-based anticoagulation.MethodsWe conducted a prospective randomized trial to address the effect of both anticoagulation regimes on safety, subjective comfort and CD34 ⁺ collection efficiency in 90 adult patients undergoing standardized LVL. Anticoagulation consisted of either citrate (group C) or a combination of heparin and low-dose citrate (group H).ResultsThe overall incidence of adverse reactions (AR) during LVL was 17%. AR consisted only of citrate-related AR; no bleeding complications were observed. Determination of parameters of the acid–base balance revealed a higher frequency of metabolic alkalosis in group C. Analysis of serum SDF-1α revealed no differences in SDF-1α plasma levels. There were no differences in the CD34 ⁺ cell collection efficiency, resulting in the harvest of equal CD34 ⁺ cell yields independent of the anticoagulation used.ConclusionsOur data show no clinical relevant effect of a heparin containing anticoagulation in terms of an increased overall CD34 ⁺ cell collection during LVL, although this regime shows some benefits in terms of the incidence and subjective tolerance towards AR. Based on our results the decision between a citrate- and heparin-substituted anticoagulation for LVL should be driven by patient-related factors, and should concern potential contraindications of both methods.     

Higher efficacy of Etoposide + Cytarabine Plus Pegfilgrastim in poorly mobilizing Multiple Myeloma and lymphoma Patients

Background aimsAn optimal strategy for mobilizing hematopoietic stem cells in poorly mobilizing patients with multiple myeloma (MM) and lymphoma has not yet been determined.MethodsWe retrospectively analyzed the efficacy and safety of etoposide combined with cytarabine (etoposide 75 mg/m², daily d1∼2; Ara-C 300 mg/m², every 12 h d1∼2), plus pegfilgrastim (6 mg d6) in 32 patients with MM or lymphoma, among whom 53.1% were defined as “proven poor mobilizers.”ResultsThis approach resulted in adequate mobilization (≥2.0 × 10⁶ CD34⁺ cells/kg) in 93.8% of patients and optimal mobilization (≥5.0 × 10⁶ CD34⁺ cells/kg) in 71.9% of patients. A total of 100% of patients with MM reached at least 5 × 10⁶ CD34⁺ cells/kg collected, the amount required for double autologous stem cell transplant. In total, 88.2% of patients with lymphoma reached at least 2 × 10⁶ CD34⁺ cells/kg collected, the amount required for a single autologous stem cell transplant. This was achieved with a single leukapheresis in 78.1% of cases. A median peak number of 42.0/μL circulating CD34⁺ cells and a median number of blood CD34⁺ cells counts in 6.7 × 10⁶/L were collected among 30 successful mobilizers. Approximately 6.3% of patients required plerixafor rescue, which was successful. Nine (28.1%) of the 32 patients suffered grade 2∼3 infections, and 50% required platelet transfusions.ConclusionsWe conclude that chemo-mobilization with etoposide, Ara-C and pegfilgrastim in poorly mobilizing patients with MM or lymphoma is very effective and has acceptable toxicity.     

Consistent bone marrow-derived cell mobilization following repeated short courses of granulocyte–colony-stimulating factor in patients with amyotrophic lateral sclerosis: results from a multicenter prospective trial

Background and aimsThe aim of this study was to evaluate and characterize the feasibility and safety of bone marrow-derived cell (BMC) mobilization following repeated courses of granulocyte–colony stimulating factor (G-CSF) in patients with amyotrophic lateral sclerosis (ALS).MethodsBetween January 2006 and March 2007, 26 ALS patients entered a multicenter trial that included four courses of BMC mobilization at 3-month intervals. In each course, G-CSF (5 μg/kg b.i.d.) was administered for four consecutive days; 18% mannitol was also given. Mobilization was monitored by flow cytometry analysis of circulating CD34⁺ cells and by in vitro colony assay for clonogenic progenitors. Co-expression by CD34⁺ cells of CD133, CD90, CD184, CD117 and CD31 was also assessed.ResultsTwenty patients completed the four-course schedule. One patient died and one refused to continue the program before starting the mobilization courses; four discontinued the study protocol because of disease progression. Overall, 89 G-CSF courses were delivered. There were two severe adverse events: one prolactinoma and one deep vein thrombosis. There were no discontinuations as a result of toxic complications. Circulating CD34⁺ cells were monitored during 85 G-CSF courses and were always markedly increased; the range of median peak values was 41–57/μL, with no significant differences among the four G-CSF courses. Circulating clonogenic progenitor levels paralleled CD34⁺ cell levels. Most mobilized CD34⁺ cells co-expressed stem cell markers, with a significant increase in CD133 co-expression.ConclusionsIt is feasible to deliver repeated courses of G-CSF to mobilize a substantial number of CD34⁺ cells in patients with ALS; mobilized BMC include immature cells with potential clinical usefulness.     

Influence of related donor age on outcomes after peripheral blood stem cell transplantation

Background aimsThe rising use of allogeneic transplantation in older recipients necessitates considering older related donors. The effect of related donor age for peripheral blood stem cell allografts (PBSC) on graft maintenance and outcomes, independent of CD34⁺cell dose, has not been well-characterized.MethodsHLA-related donors (98% siblings) underwent a uniform filgrastim-based mobilization regimen aiming to collect and infuse 5 × 10⁶ CD34⁺ cells/recipient kg. Donor and recipient age were modeled in multiple ways to account for the correlation, and outcomes reported by decade of donor age.ResultsThe median donor and recipient ages were 52 years and 54 years, respectively. The mean CD34⁺ cell dose infused was 5.6 × 10⁶ CD34⁺/kg and 75% of patients received a narrow range between 4.4 and 6.6 × 10⁶ CD34⁺ cells/kg. Neither better PBSC mobilization nor higher CD34⁺ content of allografts was significantly associated with engraftment or transplant outcomes. After adjusting for recipient age and other prognostic factors, older donor age by decade conferred a lower risk of non-relapse mortality (NRM) [hazard ratio (HR) = 0.64, 95% confidence interval (CI) 0.45–0.91, P = 0.013] and borderline improvement in overall survival (OS) (HR = 0.76, 95% CI 0.58–0.99, P = 0.045) without altering progression-free survival (PFS) (HR = 0.85, 95% CI 0.66–1.07, P = 0.18).ConclusionsOlder donor age does not worsen outcome after matched related donor PBSC transplantation in patients receiving a narrow range CD34⁺ cells. The relatively small sample size mandates that the finding of similar to improved outcomes for older related donor age must be confirmed in larger studies.     

Granulocyte-macrophage colony-stimulating factor increases the proportion of circulating dendritic cells after autologous but not after allogeneic hematopoietic stem cell transplantation

Background aimsGranulocyte–macrophage (GM) colony-stimulating factor (CSF) has been used as an adjuvant in cancer immunotherapy. We tested the hypothesis that GM-CSF (Leukine^®; sargramostim) improves immune reconstitution after hematopoietic stem cell transplantation (HSCT) based on our prior in vitro work that demonstrated the pro-inflammatory effects of GM-CSF on dendritic cells (DC).MethodsGM-CSF was administered to donors, along with standard granulocyte (G) CSF, during stem cell mobilization, and to recipients from the day prior to transplant until engraftment. Eighteen patients consented to the GM-CSF⁺ protocol and were compared with 17 matched controls undergoing HSCT during the same time period (GM-CSF^?).ResultsNumbers of white blood cells (WBC) and CD34⁺ stem cells in the graft were comparable to controls. Surprisingly, contrary to our hypothesis, the allogeneic donor graft had significantly decreased numbers of CD3⁺ T cells and their subsets (CD4⁺, CD4⁺ CD45RA⁺, CD4⁺ CD45RO⁺, CD8⁺ and CD8⁺ CD45RO⁺), DC (both myeloid and plasmacytoid) and natural killer (NK) cells (CD16⁺ CD56⁺). In the GM-CSF arm, following allogeneic transplantation, the levels of DC, T cells and NK cells did not increase with treatment. Conversely, autologous transplant patients receiving GM-CSF had a higher proportion of DC at the time of engraftment.ConclusionsThese findings demonstrate that administration of GM-CSF improves DC reconstitution after autologous rather than allogeneic HSCT.     

Pseudotyped recombinant adeno-associated viral vectors mediate efficient gene transfer into primary human CD34+ peripheral blood progenitor cells

Background and aimsBecause of their pluripotency, human CD34⁺ peripheral blood progenitor cells (PBPC) are targets of interest for the treatment of many acquired and inherited disorders using gene therapeutic approaches. Unfortunately, most current vector systems lack either sufficient transduction efficiency or an appropriate safety profile. Standard single-stranded recombinant adeno-associated virus 2 (AAV2)-based vectors offer an advantageous safety profile, yet lack the required efficiency in human PBPC.MethodsA panel of pseudotyped AAV vectors (designated AAV2/x, containing the vector genome of serotype 2 and capsid of serotype x, AAV2/1–AAV2/6) was screened on primary human granulocyte–colony-stimulating factor (G-CSF)-mobilized CD34⁺ PBPC to determine their gene transfer efficacy. Additionally, double-stranded self-complementary AAV (dsAAV) were used to determine possible second-strand synthesis limitations.ResultsAAV2/6 vectors proved to be the most efficient [12.8% (1.8–25.4%) transgene-expressing PBPC after a single transduction], being significantly more efficient (all P < 0.005) than the other vectors [AAV2/2, 2.0% (0.2–7.3%); AAV2/1, 1.3% (0.1–2.9%); others, <; 1% transgene-expressing PBPC]. In addition, the relevance of the single-to-double-strand conversion block in transduction of human PBPC could be shown using pseudotyped dsAAV vectors: for dsAAV2/2 [9.3% (8.3–20.3%); P < 0.001] and dsAAV2/6 [37.7% (23.6–61.0%); P < 0.001) significantly more PBPC expressed the transgene compared with their single-stranded counterparts; for dsAAV2/1, no significant increase could be observed.ConclusionsWe have shown that clinically relevant transduction efficiency levels using AAV-based vectors in human CD34⁺ PBPC are feasible, thereby offering an efficient alternative vector system for gene transfer into this important target cell population.     

Development of a quantitative prediction model for peripheral blood stem cell collection yield in the plerixafor era

Background aimsPredicting autologous peripheral blood stem cell (PBSC) collection yield before leukapheresis is important for optimizing PBSC mobilization and autologous stem cell transplantation (ASCT) for treating hematological malignancies. Although guidelines for plerixafor usage based on peripheral blood CD34⁺ (PB-CD34⁺) cell count are available, their predictive performance in the real world remains unclear.MethodsThis study retrospectively analyzed 55 mobilization procedures for patients with non-Hodgkin lymphoma or multiple myeloma and developed a novel quantitative prediction model for CD34⁺ cell collection yield that incorporated four clinical parameters available the day before leukapheresis; namely, PB-CD34⁺ cell count the day before apheresis (day ?1 PB-CD34⁺), number of prior chemotherapy regimens, disease status at apheresis and mobilization protocol.ResultsThe effects of PB-CD34⁺ cell counts on CD34⁺ cell collection yield varied widely per patient characteristics, and plerixafor usage was recommended in patients with poorly controlled disease or those with a history of heavy pre-treatments even with abundant day ?1 PB-CD34⁺ cell count. This model suggested a more proactive use of plerixafor than that recommended by the guidelines for patients with poor pre-collection condition or those with a higher target number of CD34⁺ cells. Further, the authors analyzed the clinical outcomes of ASCT and found that plerixafor use for stem cell mobilization did not affect short- or long-term outcomes after ASCT.ConclusionsAlthough external validations are necessary, the results can be beneficial for establishing more effective and safer mobilization strategies.     

Characterization of hematopoietic stem cell subsets from patients with multiple myeloma after mobilization with plerixafor

Background aimsPrevious studies have demonstrated that the combination of granulocyte–colony-stimulating factor (G-CSF) + plerixafor is more efficient in mobilizing CD34⁺ hematopoietic stem cells (HSC) into the peripheral blood than G-CSF alone. In this study we analyzed the impact of adding plerixafor to G-CSF upon the mobilization of different HSC subsets.MethodsWe characterized the immunophenotype of HSC subsets isolated from the peripheral blood of eight patients with multiple myeloma (MM) before and after treatment with plerixafor. All patients were supposed to collect stem cells prior to high-dose chemotherapy and consecutive autologous stem cell transplantation, and therefore received front-line mobilization with 4 days of G-CSF followed by a single dose of plerixafor. Samples of peripheral blood were analyzed comparatively by flow cytometry directly before and 12 h after administration of plerixafor.ResultsThe number of aldehyde dehydrogenase (ALDH)^bright and CD34⁺ cells was significantly higher after plerixafor treatment (1.2–5.0 and 1.5–6.0 times; both P < 0.01) and an enrichment of the very primitive CD34⁺ CD38^? and ALDH^bright CD34⁺ CD38^? HSC subsets was detectable. Additionally, two distinct ALDH⁺ subsets could be clearly distinguished. The small ALDH^high subset showed a higher number of CD34⁺ CD38^? cells in contrast to the total ALDH^bright subpopulation and probably represented a very primitive subpopulation of HSC.ConclusionsA combined staining of ALDH, CD34 and CD38 might represent a powerful tool for the identification of a very rare and primitive hematopoietic stem cell subset. The addition of plerixafor mobilized not only more CD34⁺ cells but was also able to increase the proportion of more primitive stem cell subsets.     

A French single-center experience on allogeneic stem cell transplant cryopreservation during severe acute respiratory syndrome coronavirus 2 pandemic

Background aimsAllogeneic hematopoietic stem cell transplantation (allo-SCT) is a curative treatment for chemo-resistant hematological malignancies. Because of transport restriction imposed by the coronavirus disease 2019 pandemic, regulatory bodies and societies recommended graft cryopreservation before recipient conditioning. However, the freezing and thawing processes, including washing steps, might impair CD34+ cell recovery and viability, thereby impacting the recipient engraftment. Over 1 year (between March 2020 and May 2021), we aimed to analyze the results of frozen/thawed peripheral blood stem cell allografts in terms of stem cell quality and clinical outcomes.MethodsTransplant quality was evaluated by comparing total nucleated cells (TNCs), CD34+ cells and colony-forming unit–granulocyte/macrophage (CFU-GM)/kg numbers as well as TNC and CD34+ cell viabilities before and after thawing. Intrinsic biological parameters such as granulocyte, platelet and CD34+ cell concentrations were analyzed, as they might be responsible for a quality loss. The impact of the CD34+ cell richness of the graft on TNC and CD34 yields was evaluated by designing three groups of transplants based on their CD34 /kg value at collection: >8 × 10 ⁶/kg, between 6 and 8 × 10⁶/kg and <6 × 10⁶/kg. The consequences of cryopreservation were compared in the fresh and thawed group by evaluating the main transplant outcomes.ResultsOver 1 year, 76 recipients were included in the study; 57 patients received a thawed and 19 patients a fresh allo-SCT. None received allo-SCT from a severe acute respiratory syndrome coronavirus 2–positive donor. The freezing of 57 transplants led to the storage of 309 bags, for a mean storage time (between freezing and thawing) of 14 days. For the fresh transplant group, only 41 bags were stored for potential future donor lymphocyte infusions. Regarding the graft characteristics at collection, median number of cryopreserved TNC and CD34+ cells/kg were greater than those for fresh infusions. After thawing, median yields were 74.0%, 69.0% and 48.0% for TNC, CD34+ cells and CFU-GM, respectively. The median TNC dose/kg obtained after thawing was 5.8 × 10⁸, with a median viability of 76%. The median CD34+ cells/kg was 5 × 10⁶, with a median viability of 87%. In the fresh transplant group, the median TNC/kg was 5.9 × 10⁸/kg, and the median CD34+ cells/kg and CFU-GM/kg were 6 × 10⁶/kg and 276.5 × 10⁴/kg, respectively. Sixty-one percent of the thawed transplants were out of specifications regarding the CD34+ cells/ kg requested cell dose (6 × 10⁶/kg) and 85% of them would have had this dose if their hematopoietic stem cell transplant had been infused fresh. Regarding fresh grafts, 15.8% contained less than 6 × 10⁶ CD34+ cells /kg and came from peripheral blood stem cells that did not reach 6 × 10⁶ CD34+ cells /kg at collection. Regarding the factor that impaired CD34 and TNC yield after thawing, no significant impact of the granulocyte count, the platelet count or the CD34+ cells concentration/µL was observed. However, grafts containing more than 8 × 10 ⁶/kg at collection showed a significantly lower TNC and CD34 yield.ConclusionsTransplant outcomes (engraftment, graft-versus-host disease, infections, relapse or death) were not significantly different between the two groups.     

Day 4 collection of granulocyte colony-stimulating factor-mobilized HLA-matched sibling donor peripheral blood allografts demonstrates no long-term increase in chronic graft-versus-host disease or relapse rates

Background aimsIn a previous pilot study of HLA-matched sibling donor hematopoietic cell transplantation (HCT), the authors determined the feasibility of day 4 versus day 5 granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood stem cell (PBSC) collection compared with a historical cohort. Given identified differences in the PBSC product (day 4 cohort with significantly lower infused total nucleated, mononuclear and CD3 cells compared with other collection cohorts), the authors performed a follow-up study to determine long-term post-HCT outcomes, including detailed characterization of chronic graft-versus-host disease (GVHD).MethodsThis was a prospective observational study, and the authors collected data on chronic GVHD, staging, sites of involvement and treatments. Performance status, incidence of relapse, overall survival and duration of immunosuppressive therapy (IST) were also evaluated. Data were examined retrospectively. To account for differences in length of follow-up among cohorts, the authors also determined performance status and chronic GVHD staging, sites and treatment at 2 years post-HCT.ResultsAt 2 years post-HCT, the overall survival rate was 71.7% in the day 4 cohort compared with 61.5%, 52% and 56% in the day 5, 2-day and historical cohorts, respectively (P = 0.283). The cumulative incidence of chronic GVHD was 65.2% in the day 4 cohort versus 46.4% in the day 5 cohort, 51.1% in the 2-day cohort and 65% in the historical cohort (P = 0.26). There was no significant difference in the maximum overall stage of chronic GVHD (P = 0.513), median number of sites involved (P = 0.401) or cumulative incidence of discontinuation of IST (P = 0.32). Death from chronic GVHD was less common in the day 4 and day 5 cohorts compared with the 2-day and historical cohorts, though this did not reach statistical significance.ConclusionsThe authors’ preliminary results demonstrated that collection of allogeneic matched sibling donor PBSCs on day 4 of G-CSF was feasible, reduced donor exposure to growth factor and was associated with an initial cost savings. Importantly, the authors now demonstrate that transplantation of day 4 mobilized PBSCs is not associated with any adverse outcomes post-HCT, including late effects such as chronic GVHD. Further investigation of donor G-CSF collection algorithms is merited in other HCT settings, including unrelated and mismatched related donors.     

Mobilization of CD34~+CD38~- hematopoietic stem cells after priming in acute myeloid leukemia

AIM: To evaluate quantitatively and qualitatively the different CD34+cell subsets after priming by chemotherapy granulocyte colony-stimulating factor(± G-CSF)in patients with acute myeloid leukemia.METHODS: Peripheral blood and bone marrow sampleswere harvested in 8 acute myeloid leukemia patients during and after induction chemotherapy. The CD34/CD38 cell profile was analyzed by multi-parameter flow cytometry. Adhesion profile was made using CXC chemokine receptor 4(CXCR4)(CD184), VLA-4(CD49d/CD29) and CD47.RESULTS: Chemotherapy ± G-CSF mobilized immature cells(CD34+CD38 population), while the more mature cells(CD34+CD38lowand CD34+CD38+populations) decreased progressively after treatment. Circulating CD34+cells tended to be more sensitive to chemotherapy after priming with G-CSF. CD34+cell mobilization was correlated with a gradual increase in CXCR4 and CD47expression, suggesting a role in cell protection and the capacity of homing back to the marrow.CONCLUSION: Chemotherapy ± G-CSF mobilizes into the circulation CD34+bone marrow cells, of which, the immature CD34+CD38-cell population. Further manipulations of these interactions may be a means with which to control the trafficking of leukemia stem cells to improve patients’ outcomes.     

Prediction of CD34(+) cell yield in hematopoietic cell products from children by peripheral blood CD34(+) cell counts

Background aimsPeripheral blood stem cells (PBSC) are increasingly used as an alternative to bone marrow in autologous transplantations. In adult patients, the peripheral blood CD34 ⁺ cell count is a good predictor of CD34 ⁺ cell yield in apheresis. However, the determinants of stem cell yield in the pediatric population have not been well established.MethodsWe retrospectively studied 396 apheresis procedures in 301 pediatric patients. Receiver operating characteristic (ROC) curves based on pre-apheresis peripheral blood CD34 ⁺ cell counts were generated to facilitate prediction of the optimal timing of PBSC collection. The associations between CD34 ⁺ cell yield and age and mobilization regimen were analyzed.ResultsSignificant differences in CD34 ⁺ cell yield among different age groups were observed. Furthermore, higher CD34 ⁺ cell yields were obtained in patients receiving chemotherapy as part of the mobilization regimen than those without chemotherapy. A correlation was noted between the CD34 ⁺ cell yield and blood surrogate markers, including white blood cell count, absolute neutrophil count and pre-apheresis peripheral blood CD34 ⁺ cell count. Cut-off values of > 35 CD34 ⁺ cells/μL in patients < 15 years old and > 45 CD34 ⁺ cells/μL in patients ≥ 15 years old were strong predictors of an adequate PBSC collection in one apheresis session. For clinical use, ROC curves and tables were generated to assist advance planning for PBSC collection.ConclusionsThe pre-apheresis peripheral blood CD34 ⁺ cell count is most useful in predicting PBSC yield. Our new cut-off values have better operating characteristics for children than the conventional value of 20 CD34 ⁺ cells/μL used for adults.