Prediction of hematopoietic stem cell yield after mobilization with granulocyte-colony-stimulating factor in healthy unrelated donors

Comparison of biosimilar filgrastim and originator filgrastim for peripheral blood stem cell mobilization for allogeneic hematopoietic stem cell transplantation

BACKGROUND

Nivestym, a biosimilar granulocyte colony-stimulating factor (G-CSF) to the originator filgrastim (Neupogen), is now being used for the mobilization of peripheral blood stem cells (PBSC) in allogeneic hematopoietic stem cell transplantation (allo-HSCT). We aim to compare the efficacy of Nivestym and Neupogen for PBSC mobilization in healthy allogeneic donors.

METHODS

We conducted a retrospective single-center study including 541 adult allo-HSCT donors receiving Nivestym (January 2013-July 2020), or Neupogen (July 2020-June 2023) for donor PBSC mobilization. Bivariate analysis was conducted using SPSS version 28. Statistical significance was determined at a p-value <.05.

RESULTS

Our study included 541 allo-HSCT donors who received Neupogen (n = 345, 64%) or Nivestym (n = 196, 36%) for PBSC mobilization. The median age was 47 years (range 17-76). The median donor weight was 86 kg (95% confidence interval [CI]: 87-91). Donors receiving Neupogen had similar pre-G-CSF white blood cell count, CD34+ percentages, and circulating CD34+ count compared with donors receiving Nivestym. The Neupogen group had similar median PBSC product total neutrophil count, CD34+ percentage, absolute CD34+ count, and infused CD34+ dose compared with the Nivestym group. For donors aged 35 years or younger, the median CD34+ dose was higher in donors who received Neupogen compared with Nivestym (6.9 vs. 6.3 million cells/kg, p = .044).

CONCLUSIONS

Nivestym demonstrated similar efficacy for PBSC mobilization compared with Neupogen among allo-HSCT donors. In donors aged 35 years or younger, a slightly lower PBSC product CD34+ count was noted with Nivestym compared with Neupogen.

Scoping Review of Factors Associated with Stem Cell Mobilization and Collection in Allogeneic Stem Cell Donors

There is wide interindividual variation in the efficacy of CD34+ cell mobilization and collection in healthy allogenic hematopoietic stem cell donors. Donor characteristics, blood cell counts, and various factors related to mobilization and collection have been associated with blood CD34+ cell count and CD34+ cell yield after granulocyte colony-stimulating factor (G-CSF) mobilization and collection. Given the heterogenous nature of the literature reporting these associations, in this scoping review we clarify the determinants of CD34+ count and yield. Studies published between 2000 and 2023 reporting allogeneic donors undergoing G-CSF mobilization and peripheral blood stem cell (PBSC) collection were evaluated. Eligible studies were those that assessed blood CD34+ cell count or CD34+ cell yield in the first PBSC collection after mobilization with 4 or 5 days of G-CSF treatment. Associations were recorded between these outcomes and donor factors (age, sex, weight, ethnicity), mobilization factors (G-CSF scheduling or dose), collection factors (venous access, processed blood volume [PBV]) or laboratory factors (blood cell counts at baseline or after mobilization). The 52 studies evaluated between 15 and 20,884 donors. Forty-three studies were retrospective, 33 assessed blood CD34+ cell counts, and 39 assessed CD34+ cell yield from PBSCs. Blood CD34+ cell counts consistently predicted CD34+ cell yield. Younger donors usually had higher blood CD34+ cell counts and CD34+ cell yield. Most studies that investigated the effect of donor ancestry found that donors of non-European ancestry had higher blood CD34+ cell counts after mobilization and higher CD34+ cell yields from collection. The poor consensus about the best predictors of blood CD34+ cell count and yield necessitates further prospective studies, particularly of the role of donor ancestry. The current focus on donor sex as a major predictor requires re-evaluation.

CD34+ cell yield among healthy donors: Large-scale model development and validation

BACKGROUND

Successful engraftment in hematopoietic stem cell transplantation necessitates the collection of an adequate dose of CD34+ cells. Thus, the precise estimation of CD34+ cells harvested via apheresis is critical. Current CD34+ cell yield prediction models have limited reproducibility. This study aims to develop a more reliable and universally applicable model by utilizing a large dataset, enhancing yield predictions, optimizing the collection process, and improving clinical outcomes.

MATERIALS AND METHODS

A secondary analysis was conducted using the Center for International Blood and Marrow Transplant Research database, involving data from over 17 000 healthy donors who underwent filgrastim-mobilized hematopoietic progenitor cell apheresis. Linear regression, gradient boosting regressor, and logistic regression classification models were employed to predict CD34+ cell yield.

RESULTS

Key predictors identified include pre-apheresis CD34+ cell count, weight, age, sex, and blood volume processed. The linear regression model achieved a coefficient of determination (R2) value of 0.66 and a correlation coefficient (r) of 0.81. The gradient boosting regressor model demonstrated marginally improved results with an R2 value of 0.67 and an r value of 0.82. The logistic regression classification model achieved a predictive accuracy of 96% at the 200 × 106 CD34+ cell count threshold. At thresholds of 400, 600, 800, and 1000 × 106 CD34+ cell count, the accuracies were 88%, 83%, 83%, and 88%, respectively. The model demonstrated a high area under the receiver operator curve scores ranging from 0.90 to 0.93.

CONCLUSION

This study introduces advanced predictive models for estimating CD34+ cell yield, with the logistic regression classification model demonstrating remarkable accuracy and practical utility.

Stem Cells mobilization and collection in allogeneic related and unrelated donors: a single center experience with focus on plerixafor

INTRODUCTION

Poor CD34 + cells mobilization in allogeneic donors could affect transplant outcome. In a subgroup of patient mobilization with granulocyte colony-stimulating factor (G-CSF) alone is unsatisfactory, and Plerixafor could be used to enhance CD34 + cells release from bone marrow niche.

MATERIALS AND METHODS

We conducted a retrospective single-center, cohort study on healthy allogeneic donors both related and unrelated, treated by Udine Transfusion Center over the last 10 years (2012-2022). In the 195 allogeneic donors treated we analyzed age, sex, body weight, BMI, comorbidities, G-CSF dosage and even baseline white blood cell count as possible predictor of insufficient CD34 + cells mobilization on day 5. In the subgroup of related donors we evaluated even baseline CD34 + cells (measured before mobilization start). Processed donor blood volume, collection efficiency and apheresis product were examined. Additionally a comparative analysis was conducted between G-CSF alone treated donors and poor mobilizing ones, in which Plerixafor was administered at a dose of 0.24 mg/kg as a pre-emptive or rescue agent.

RESULTS

In 9 donors, due to poor mobilization (defined as CD34 + < 20/µL or estimated yield < 1 ×106 kg/recipient body weight), the use of plerixafor was necessary. PLX at a dose of 0.24 mg/kg was administered 5 h before collection, inducing an average increase of 5.1 (1.7-12.6) in CD34 + circulating cells. In this subgroup of patients, BMI and weight were significantly lower (p = 0.03). Interestingly, baseline CD34 + cells (measured before the onset of mobilization) also seems to predict poor mobilization (p = 0.003). In donors additionally treated with Plerixafor compared to those who received G-CSF alone, collection efficiency was higher (p = 0.02) and CD34 + cells collected were comparable (p = 0.2). Side effects related to the administration of plerixafor, if they occurred, were well tolerated.

CONCLUSIONS

Plerixafor is a safe and effective drug in the rescue and prevention of poor mobilization. New prospective studies on allogeneic donors should be performed to increase the treatable population to avoid inadequate collection and mobilization. New laboratory predictors such as baseline CD34 + cells should be investigated in larger cohorts and then used as early screening.

Platelet-derived circulating soluble P-selectin is sufficient to induce hematopoietic stem cell mobilization

BACKGROUND

Granulocyte colony-stimulating factor (G-CSF)-mediated mobilization of hematopoietic stem cells (HSCs) is a well-established method to prepare HSCs for transplantation nowadays. A sufficient number of HSCs is critical for successful HSC transplantation. However, approximately 2-6% of healthy stem cell donors are G-CSF-poor mobilizers for unknown reasons; thus increasing the uncertainties of HSC transplantation. The mechanism underlining G-CSF-mediated HSC mobilization remains elusive, so detailed mechanisms and an enhanced HSC mobilization strategy are urgently needed. Evidence suggests that P-selectin and P-selectin glycoprotein ligand-1 (PSGL-1) are one of the cell-cell adhesion ligand-receptor pairs for HSCs to keep contacting bone marrow (BM) stromal cells before being mobilized into circulation. This study hypothesized that blockage of PSGL-1 and P-selectin may disrupt HSC-stromal cell interaction and facilitate HSC mobilization.

METHODS

The plasma levels of soluble P-selectin (sP-sel) before and after G-CSF administration in humans and male C57BL/6J mice were analyzed using enzyme-linked immunosorbent assay. Male mice with P-selectin deficiency (Selp-/-) were further employed to investigate whether P-selectin is essential for G-CSF-induced HSC mobilization and determine which cell lineage is sP-sel derived from. Finally, wild-type mice were injected with either G-CSF or recombinant sP-sel to investigate whether sP-sel alone is sufficient for inducing HSC mobilization and whether it accomplishes this by binding to HSCs and disrupting their interaction with stromal cells in the BM.

RESULTS

A significant increase in plasma sP-sel levels was observed in humans and mice following G-CSF administration. Treatments of G-CSF induced a decrease in the level of HSC mobilization in Selp-/- mice compared with the wild-type (Selp+/+) controls. Additionally, the transfer of platelets derived from wild-type mice can ameliorate the defected HSC mobilization in the Selp-/- recipients. G-CSF induces the release of sP-sel from platelets, which is sufficient to mobilize BM HSCs into the circulation of mice by disrupting the PSGL-1 and P-selectin interaction between HSCs and stromal cells. These results collectively suggested that P-selectin is a critical factor for G-CSF-induced HSC mobilization.

CONCLUSIONS

sP-sel was identified as a novel endogenous HSC-mobilizing agent. sP-sel injections achieved a relatively faster and more convenient regimen to mobilize HSCs in mice than G-CSF. These findings may serve as a reference for developing and optimizing human HSC mobilization in the future.

Lactate dehydrogenase as a hematopoietic stem cell mobilization biomarker in autologous transplantation

INTRODUCTION

Pre-apheresis peripheral blood CD34+ cell count (PBCD34+) is the most important predictor of good cell mobilization before hematopoietic stem cell transplantation, albeit flow cytometry is not always immediately available. Identification of surrogate markers can be useful. The CD34+ cells proliferate after mobilization, resulting in elevated lactate dehydrogenase (LDH) activity and correlating with the PBCD34+ count.

OBJECTIVE

To determine the LDH cut-off value at which adequate CD34+ cell mobilization is achieved and its diagnostic yield.

MATERIALS AND METHODS

A total of 103 patients who received an autologous stem cell transplantation (ASCT) between January 2015 and January 2020 were included. Demographic and laboratory characteristics were obtained, including complete blood count, pre-apheresis PBCD34+ and LDH levels. Receiver operating characteristic (ROC) curves were performed to identify the optimal serum LDH activity cut-off points for ≥ 2 and ≥ 4 × 106 cells/kg post-mobilization CD34+ count and their diagnostic yield.

RESULTS

A post-mobilization serum LDH cut-off value of 462 U/L yielded a sensitivity (Se) = 86.8% (positive predictive value [PPV] = 72.7%), a pre- and post-mobilization serum LDH difference cut-off value of 387 U/L, an Se = 45.7% (PPV = 97%) and an LDH ratio of 2.46, with an Se = 47.1% (PPV = 97%) for an optimal mobilization count (CD34+ ≥ 4 × 106).

CONCLUSION

The LDH measurement represents a fast and affordable way to predict PBCD34+ mobilization in cases where flow cytometry is not immediately available. According to the LDH diagnostic yield, it could be used as a surrogate marker in transplant centers, supporting the CD34+ count, which remains the gold standard.

Predicting Successful Hematopoietic Stem Cell Collection in Healthy Allogeneic Donors

Introduction

Collection of peripheral blood stem cells (PBSCs) from healthy donors is a well-established process. We aimed to identify factors predictive of successful CD34+ PBSC collection and established a formula capable of predicting CD34+ cell yield.

Methods

We retrospectively evaluated 588 healthy adult donors (median age 29 years, range 18-69 years) at our institution from 2017 to 2022. The predicted minimal number of CD34+ cells was calculated as follows: (peripheral CD34+ cells/µL × adjusted collection efficiency of 30%) × total liters processed. This formula was further modified according to donor and recipient body weight (BW).

Results

Median total collection was 8.0 × 106 CD34+ cells/kg BW (range 1.0-47.1 × 106 cells/kg BW) with 522 donors (89%) collecting ≥5.0 × 106 cells/kg of recipient BW. A second leukapheresis (LP) was performed in 49 donors. Need for two LPs was more common in female donors (OR 6.68, 95% CI, 2.62-17.05; p < 0.001), donors with higher age (OR for 10 years difference 1.53, 95% CI, 1.15-2.03, p = 0.003), donors with WBC count <30 × 109/L after 5 days of granulocyte-colony stimulating factor (G-CSF) stimulation (OR, 4.33; 95% CI, 1.59-11.83; p = 0.004), and a donor/recipient weight ratio <1 (OR 6.21, 95% CI, 2.69-14.34; p < 0.001). Predictive factors for optimal LP (i.e., ≥5.0 × 106 CD34+ cells/kg of recipient BW) were peripheral blood (PB) CD34+ cell count >50/µL (OR 12.82, range 6.34-25.92, p < 0.001), male donor (OR 2.77, range 1.06-7.23, p = 0.04), and a donor/recipient weight ratio >1 (OR 3.12, range 1.57-6.24, p = 0.001). WBC, platelets, hemoglobin, and age had no significant predictive value. Predicted versus observed number of CD34+ cells/kg BW collected demonstrated a very strong linear correlation (r = 0.925, 95% CI, 0.912-0.936, p < 0.0001).

Conclusions

Of the routinely monitored indicators in PBSC donors, CD34+ cell count in PB is the most important factor in predicting G-CSF-induced PBSC yields. Higher age, female sex, WBC <30 × 109/L, and a donor/recipient weight ratio <1 are useful indicators for identifying suboptimal mobilizers. The modified formula has shown successful and consistent performance in the prediction of key outcome measures including the minimum CD34+ cell collection, determination of the required length of apheresis, and whether a second day of PBSC collection was necessary to achieve the respective collection goal.

A novel PEGylated form of granulocyte colony-stimulating factor, mecapegfilgrastim, for peripheral blood stem cell mobilization in patients with hematologic malignancies

BACKGROUND

The Pegylated recombinant human granulocyte colony stimulating factor (PEG-rhG-CSF) has longer half-life and is given once only, which is more comfortable for patients. We aimed to evaluate the efficacy of mecapegfilgrastim for hematopoietic stem cell (HSC) mobilization in patients with hematologic malignancies and to explore the potential factors related to HSC mobilization.

METHODS

A retrospective analysis was performed on patients who underwent HSC mobilization in the hematology department of Mianyang Central Hospital from April 2016 to November 2022. The number of CD34 + cells collected was compared between the patients receiving mecapegfilgrastim (PEG group) and those receiving recombinant human granulocyte colony-stimulating factor (rhG-CSF group), and the possible factors for mobilization failure were analyzed.

RESULTS

The success rates of collecting CD34 + cells in the PEG group and rhG-CSF group were 80.6% and 67.7%, respectively (χ = 1.444, P = 0.229). The median CD34 + cell counts were 3.62 × 10^6/kg and 2.92 × 10^6/kg (P = 0.178), respectively. After combination with plerixafor for mobilization, the median number of CD34 + cells collected in the PEG group and rhG-CSF group were 3.64 × 10^6/kg and 3.92 × 10^6/kg, respectively, with no significant difference (P = 0.754). There was no significant difference in hematopoietic cell recovery or infection between the groups (P > 0.05). Multivariate analysis showed that more than 5 cycles of chemotherapy (OR = 15.897, 95% CI: 1.766-143.127, P = 0.014), a precollection WBC count < 32 × 10^9/L (OR = 14.441, 95% CI: 2.180-95.657, P = 0.006) and a precollection to premobilization lymphocyte ratio < 1.7 (OR = 11.388, 95% CI: 2.129-60.915, P = 0.004) were independent risk factors for HSC mobilization failure.

CONCLUSIONS

The HSC mobilization efficacy of mecapegfilgrastim in patients with hematologic malignancies was comparable to that of rhG-CSF, and combination with plerixafor for mobilization was feasible and effective. Patients with more than 5 cycles of chemotherapy before HSC mobilization, a precollection WBC count lower than 32 × 10^9/L, and a precollection lymphocyte count less than 1.7 times the premobilization lymphocyte count have a high probability of HSC mobilization failure.

Peripheral Blood Allogeneic Stem Cell Mobilization: Can We Predict a Suboptimal Mobilization?

Allogeneic peripheral blood stem cells mobilization is now the basis of most stem cell transplants. In a very limited number of cases, mobilization is suboptimal leading to further collection procedures, to suboptimal cell doses infusion with delayed engraftment time, increased risks of transplant procedure and of related costs. To date we have no recognized and shared criteria for early estimating the probability of poor mobilization in healthy donors. We then analyzed allogeneic peripheral blood stem cell donations performed at the Fondazione Policlinico Universitario A.Gemelli IRCCS Hospital from January 2013 to December 2021 in order to identify premobilization factors associated with successful mobilization. The following data were collected: age, gender, weight, complete blood cell count at baseline, G-CSF dose, number of collection procedures, CD34+ cell count in peripheral blood on the first day of collection, CD34+ cell dose per kg body weight of recipient. Mobilization efficacy was defined according to the number of CD34+ cells in peripheral blood on day +5 of G-CSF administration. We classified donors as sub-optimal mobilizers or good mobilizers according to the achievement of the 50 CD34+ cell/μL threshold. We observed 30 suboptimal mobilizations in 158 allogeneic peripheral blood stem cell donations. Age and baseline white blood cell count were factors significantly associated with negative or positive impact on mobilization, respectively. We did not find significant differences in mobilization based on gender or G-CSF dose. Using cut-off values of 43 years and 5.5×10⁹/L WBC count, we built a suboptimal mobilization score: donors who reach 2, 1 or 0 points have a 46%, 16% or 4% probability of suboptimal mobilization, respectively. Our model explains 26% of the variability of mobilization confirming that most of the mobilization magnitude depends on genetically determined factors; however, suboptimal mobilization score is a simple tool providing an early assessment of mobilization efficacy before G-CSF administration begins in order to support allogeneic stem cells selection, mobilization and collection. Through a systematic review, we looked for confirmation of our findings. According to the published articles, all the variables we included in our model are confirmed to be strongly related to the success of mobilization. We believe that score system approach could be applied in clinical practice to assess the risk of mobilization failure at baseline allowing for a priori intervention.

Use of plerixafor to mobilize haematopoietic progenitor cells in healthy donors

Increased transplant activity calls for improved stem cell collection, especially when peripheral blood is the preferred source of haematopoietic progenitor cells (HPCs). Plerixafor is a bicyclam molecule that mobilizes CD34+ cells by reversibly disrupting CXCR4-CXCL12-supported HPC retention. Plerixafor is given with granulocyte colony-stimulating factor (G-CSF) to help harvest autologous CD34+ cells for transplantation when mobilization with G-CSF fails. Mobilization protocols with the same doses of plerixafor and G-CSF have been used off-label in healthy allogeneic donors, with equal success and scarce side effects, both in adult and paediatric patients. Plerixafor has also been used as a sole mobilization agent. Plerixafor alone or coupled with G-CSF might lead to harvesting distinct cellular populations conferring improved engraftment properties and increased survival. Those characteristics might make plerixafor an especially attractive mobilization agent, particularly for non-related donations. However, available data are limited, and long-term follow-up is needed to clarify the best scenario for using plerixafor with or without G-CSF in healthy donors. In this review, we will summarize the evidence supporting this practice, highlighting the practical aspects and providing clues for an expanded use of plerixafor.

Weighty choices: selecting optimal G-CSF doses for stem cell mobilization to optimize yield

There are limited data on the effect of donor body mass index (BMI) on peripheral blood stem cell (PBSC) mobilization response to granulocyte colony-stimulating factor (G-CSF), especially in unrelated donors. Obesity has been associated with persistent leukocytosis, elevated circulating progenitor cells, and enhanced stem cell mobilization. Therefore, we hypothesized that adequate collection of CD34+ cells may be achieved with lower doses (per kilogram of body weight) of G-CSF in donors with higher BMI compared with donors with lower BMI. Using the Center for International Blood and Marrow Transplant Research database, we evaluated the impact of donor BMI on G-CSF-mobilized PBSC yield in healthy unrelated donors. We examined 20 884 PBSC donations collected at National Marrow Donor Program centers between 2006 and 2016. We found significantly higher collection yields in obese and severely obese donors compared with normal and overweight donors. An increase in average daily G-CSF dose was associated with an increase in stem cell yield in donors with normal or overweight BMI. In contrast, an increase in average daily G-CSF dose beyond 780 μg per day in obese and 900 μg per day in severely obese donors did not increase cell yield. Pain and toxicities were assessed at baseline, during G-CSF administration, and postcollection. Obesity was associated with higher levels of self-reported donation-related pain and toxicities in the pericollection and early postdonation recovery periods. This study suggests a maximum effective G-CSF dose for PBSC mobilization in obese and severely obese donors, beyond which higher doses of G-CSF add no increased yield.

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.

Donor-intrinsic variables determine mobilization efficiency: analyses from a cohort of sixty twice-mobilized stem cell donors

Background

Healthy volunteer registry donors have become the backbone of stem cell transplantation programs. While most registrants will never become actual donors, a small minority are called upon twice, most commonly for the same patient because of poor graft function. Anecdotal evidence provides no hard reasons to disallow second-time mobilized apheresis, but few centers have treated enough two-time donors for definitive conclusions. Moreover, for reasons unknown, the efficiency of G-CSF varies greatly between donations.

Methods

Comparison of outcomes of first vs. second donations can formally confirm G-CSF responsiveness as intrinsically, likely genetically, determined. In our database, we identified 60 donors (1.3%) who received two cycles of G-CSF 24 days to 4 years apart and systematically compared mobilization outcomes.

Results

First and second mobilization and collection proceeded without severe or unusual adverse effects. First-time mobilization efficiency was highly predictive of second-time mobilization. Neither mobilization efficiency nor time lag between donations affected the similarity of first- and second-time mobilization outcomes.

Conclusions

With the caveat that only donors with an unremarkable first donation were cleared for a second, our data indicate that a second donation is feasible, equally tolerable as a first donation, and efficient. Moreover, the data strongly support the notion of donor-intrinsic variables dictating mobilization response and argue against relevant damage to the stem cell compartment during mobilization with rhG-CSF.

Plerixafor-based mobilization in pediatric healthy donors with unfavorable donor/recipient body weight ratio resulted in a better CD34+ collection yield: A retrospective analysis

INTRODUCTION

In order to propose risk-adapted mobilization algorithms, several authors have tried to look for predictive factors of the CD34⁺ yield in healthy pediatric donors. Donor recipient body weight ratio (D/R ratio) was identified as one of the main variables related with the success to achieve the target cell dose for transplantation. According to this variable we modified the mobilization schedule.

MATERIAL AND METHODS

We report the results of 46 mobilizations and apheresis procedures performed in our center with unfavorable D/R ratio. Mobilization was attempted by the standard regime of G-CSF (10 mcg/kg/24 hours) in 28 cases (60.9%), with high dose G-CSF (10 mcg/kg/12 hours) in 9 cases (19.6%), and with plerixafor and G-CSF single dose regime in 9 cases (19.6%).

RESULTS

CD34⁺ cell quantification before apheresis is closely related to CD34⁺ yield, being the only factor related to collected CD34⁺ cells (beta .71; P < .0001). The mobilization efficiency was higher in plerixafor group compared to the other two schedules (P < .0001). By using plerixafor for mobilization, we achieved the target CD34⁺ cell dose of ≥2 × 10⁶ /kg per recipient body weight in all cases with unfavorable D/R ratio. It was observed that 17.4% of cases that not reached the established target cell dose were located in the standard or high-dose mobilization regimes. This difference is even greater for optimal collections (≥5 × 10⁶ /kg), since of the 54.3% cases that did not reach this goal none was mobilized by plerixafor.

CONCLUSION

Tailoring the mobilization regime we can reach the target cell dose, even in those cases with the worst D/R ratio.

Salvage treatment with plerixafor in poor mobilizing allogeneic stem cell donors: results of a prospective phase II-trial

We conducted a prospective clinical trial to investigate the safety and efficacy of plerixafor (P) in allogeneic peripheral blood stem cells (PBSC) donors with poor mobilization response to standard-dose granulocyte colony-stimulating factor (G-CSF), defined by <2 × 10⁶ CD34 + cells/kg recipient body-weight (CD34+/kg RBW) after 1st apheresis. A single dose of 240 µg/kg P was injected subcutaneously at 10 p.m. on the day of the 1st apheresis. Thirty-seven allogeneic PBSC donors underwent study treatment. The median CD34+ count in peripheral blood was 15/µl on Day 1 after G-CSF alone, versus 44/µl on Day 2 after G-CSF plus P (p < 0.001). The median yield of CD34+ cells was 1.1 × 10⁸ on Day 1 and 2.8 × 10⁸ on Day 2. In contrast to a median yield of only 1.31 × 10⁶ CD CD34+/kg RBW on Day 1, triggering study inclusion, a median of 3.74 × 10⁶ CD CD34+/kg RBW were collected with G-CSF plus P on Day 2. Of 37 donors, 21 reached the target cell count of >4.5 × 10⁶ CD34+/kg RBW (57%, 95%CI 40-73%). No donor experienced a severe adverse event requiring treatment. In conclusion, P might be considered on a case-by-case basis for healthy allogeneic donors with very poor stem cell mobilization success after G-CSF.

Seasonal variation of human physiology does not influence the harvest of peripheral blood CD34+ cells from unrelated hematopoietic stem cell donors

There are many reports on factors predicting the outcome of PBSC (peripheral blood stem cell) mobilization, such as the donor's gender, age, weight, white blood cell count, platelets pre apheresis, LDH and iron status. Although there are reports of seasonal variation in the physiology of the human immune system and hematopoiesis there are no data that such differences play a role in the response to G-CSF in healthy hematopoietic stem cell donors. The response to G-CSF could also impact the collection results during different seasons. To assess the possible impact of seasonal variation we performed a retrospective, single-center analysis of mobilization and harvest of PBSC in 330 healthy unrelated donors. We found no significant differences in the number of CD34+ cells in peripheral blood after G-CSF mobilization and in collection results when all donors were analyzed. In the subgroup of male donors the number of CD34+ stem cells after G-CSF mobilization was higher than average in summer and autumn (p = 0.036), however, it did not translate into clinically relevant differences in stem cell harvest. We conclude that although there is possible seasonal variation in the response to G-CSF in male donors there is no impact on PBSC harvest in healthy unrelated donors.

Mobilization-based transplantation of young-donor hematopoietic stem cells extends lifespan in mice

Mammalian aging is associated with reduced tissue regeneration and loss of physiological integrity. With age, stem cells diminish in their ability to regenerate adult tissues, likely contributing to age-related morbidity. Thus, we replaced aged hematopoietic stem cells (HSCs) with young-donor HSCs using a novel mobilization-enabled hematopoietic stem cell transplantation (HSCT) technology as an alternative to the highly toxic conditioning regimens used in conventional HSCT. Using this approach, we are the first to report an increase in median lifespan (12%) and a decrease in overall mortality hazard (HR: 0.42, CI: 0.273-0.638) in aged mice following transplantation of young-donor HSCs. The increase in longevity was accompanied by reductions of frailty measures and increases in food intake and body weight of aged recipients. Young-donor HSCs not only preserved youthful function within the aged bone marrow stroma, but also at least partially ameliorated dysfunctional hematopoietic phenotypes of aged recipients. This compelling evidence that mammalian health and lifespan can be extended through stem cell therapy adds a new category to the very limited list of successful anti-aging/life-extending interventions. Our findings have implications for further development of stem cell therapies for increasing health and lifespan.

The effect of serum vitamin B12, folate, ferritin levels and transferrin saturation on stem cell mobilization in allogeneic donors

INTRODUCTION

Peripheric blood derived stem cells are used in 75 % of allogeneic stem cell transplantations. Iron, vitamin B12 and folate involve in hematopoiesis. Therefore serum levels of iron, vitamin B12 and folat may effect stem cell mobilization. We aimed to analyze the effects of iron status, vitamin B12 and folate levels on peripheric blood stem cell mobilization in healthy donors.

METHOD

The mobilization results of 218 allogeneic donors were analyzed retrospectively.

RESULTS

In 64 donors, serum ferritin level was <15 μg / L and transferrin saturation was <20 %. When we compared the donors with iron deficiency to the donors without iron deficiency, the number of collected CD34 + cell was significantly higher in donors without iron deficiency. We did not find any impact of serum vitamin B12 and folate level on CD34+ cells collected.

CONCLUSION

Our study shows that serum ferritin and transferrin saturation have a greater effect on the amount of CD34+ cells collected from donors than serum vitamin B12 and folate levels. Consequently, when compliance tests of allogeneic donors are performed, the evaluation of vitamin B12 and folate levels is not necessary; whereas iron deficiency must be assessed and -if possible- corrected before apheresis is performed.

Smoking is an important factor that affects peripheral blood progenitor cells yield in healthy male donors

BACKGROUND

Smoking could reduce the CD34+ cells in peripheral blood of healthy individual. This study aimed to investigate the correlation between smoking load and the effect of peripheral blood hematopoietic progenitor cells (PBPCs) mobilization by granulocyte colony-stimulating factor (G-CSF) alone in healthy donors.

METHODS

Retrospective analysis was performed on 145 healthy adult PBPCs donors who underwent PBPCs mobilization and collection. Smoking factors were evaluated and correlated with mobilization responses, as indicated by the collected CD34+ cells concentration.

RESULTS

The collected CD34+ cells concentration was closely related to pre-CD34 (P < .001) and CD34+ cells collected per volume blood processed (P < .001) which suggested that collected CD34+ cells concentration was a reliable indicator of PBPCs mobilization efficiency. The heavy smoking donors revealed significantly lower collected CD34+ cells concentration, compared to that of the nonsmoking (P < .001) and light smoking donors (P < .05). The levels of collected CD34+ cells in light smoking were also obviously lower than that in nonsmoking donors (P < .05).There were no obvious differences in the collected CD34+ cells concentration, overall processed blood volume and total collected CD34+ cells between nonsmoking and smoking cessation groups (P = .490; P = .464; P = .819).

CONCLUSION

Cigarette smoking is an important factor that affects the yield of PBPCs in male donors, especially when the smoking load is more than five pack-years. Mobilization of PBMCs could be restored by smoking cessation in chronic smokers.

Validation of a formula predictive of peripheral blood stem cell yield and successful collection in healthy allogeneic donors

BACKGROUND

An efficient mobilization and collection of peripheral blood stem cells (PBSCs) are crucial to optimize engraftment in the recipient. We aim to validate a formula that predicted CD34⁺ cell yield and to describe variables that correlated with high yield mobilization and collection in healthy donors.

METHODS

We retrospectively analyzed clinical and laboratory data from healthy donors who underwent PBSC collection from 2006 to 2015. The predicted number of collected cells was calculated using the following formula: Total number of CD34⁺ (cells×10⁶/kg) yield=[(peripheral CD34⁺ cells/μL)×(0.43)/recipient body weight (kg)]×total liters processed.

RESULTS

We evaluated 338 collections from 307 allogeneic PBSC donors. The predicted versus the observed number of CD34⁺ cells/kg collected yielded an r-value of 0.775 (0.726-0.816; p<0.0001). Overall, 55.7% donors had an acceptable mobilization level. Donors with a body weight <67kg were less likely to yield a satisfactory CD34⁺ cell count (OR=0.44; 95% CI 0.24-0.81), while a white blood cell (WBC) count >40×10⁹/L (OR=3.69; 2.11-6.46) and platelet count ≥200×10⁹/L (OR=2.09; 1.26-3.47) on the day of collection predicted a good level of mobilization. Predictors of a CD34⁺ cell yield/kg of ≥4×10⁶ with only one apheresis session were: circulating CD34⁺ cells/μL >40 (OR=16; 6.94-36.93), hemoglobin ≥14g/dL (OR=3.40; 1.53-7.57), WBC >40×10⁹/L (OR=4.61; 2.10-10.10) on the first collection day, and a positive delta weight between donor and recipient (OR=3.10; 1.36-7.06).

CONCLUSION

The formula for predicting CD34⁺ cell yield is accurate and suggests the optimal length of time for successful leukapheresis. Validation of the predictors of successful mobilization will help to further refine PBSC leukapheresis procedures.

Prior blood donations do not affect efficacy of G-CSF mobilization nor outcomes of haematopoietic stem cell collection in healthy donors

BACKGROUND AND OBJECTIVES

Many consider volunteer blood donors as ideal candidates for unrelated haematopoietic progenitor cell (HPC) donation. However, frequent blood donations could influence the results of HPC mobilization. To our best knowledge, there are no data on the possible impact of repeated blood donation on efficiency of subsequent HPC mobilization by granulocyte colony-stimulating factor (G-CSF).

MATERIALS AND METHODS

We compared outcomes of HPC mobilization in unrelated donors with and without a history of blood donation. We conducted a prospective study on 287 consecutive donors admitted to the Department of Hematology since January 2016. The final analysis included 153 donors who agreed to take part in the study and had undergone stem cell mobilization with G-CSF.

RESULTS

History of blood donations prior to haematopoietic stem cell mobilization with G-CSF does not have a significant impact on the number of collected CD34+ cells in the first leucocytapheresis (516.2 x 10⁶ (170-1148) in blood donors vs 490.5 x 10⁶ (101-1154) in non-donors) (P = 0.32). In all donors, in this study mobilization of HPC was successful: 87.5% of blood donors and 85.6% of non-donors collected the required cell number in a single apheresis. In blood donors, a higher number of blood donations within 2 and 5 years prior to HPC mobilization correlated significantly with successful donation within one leucocytapheresis (P = 0.014 and P = 0.024, respectively).

CONCLUSION

Multiple blood donations do not significantly influence the outcome of HPC collection in unrelated donors. Blood donors and non-donors have similar results of HPC collection, so there is no reason to favour either group.

Development of an Unrelated Donor Selection Score Predictive of Survival after HCT: Donor Age Matters Most

Donor factors, in addition to HLA matching status, have been associated with recipient survival in unrelated donor (URD) hematopoietic cell transplantation (HCT); however, there is no hierarchical algorithm that weights the characteristics of individual donors against each other in a quantitative manner to facilitate donor selection. The goal of this study was to develop and validate a donor selection score that prioritizes donor characteristics associated with better survival in 8/8 HLA-matched URDs. Two separate patient/donor cohorts, the first receiving HCT between 1999 and 2011 (n = 5952, c1), and the second between 2012 and 2014 (n = 4510, c2) were included in the analysis. Both cohorts were randomly spilt, 2:1, into training and testing sets. Despite studying over 10,000 URD transplants, we were unable to validate a donor selection score. The only donor characteristic associated with better survival was younger age, with 2-year survival being 3% better when a donor 10 years younger is selected. These results support previous studies suggesting prioritization of a younger 8/8 HLA-matched donor. This large dataset also shows that none of the other donor clinical factors tested were reproducibly associated with survival, and hence flexibility in selecting URDs based on other characteristics is justified. These data support a simplified URD selection process and have significant implications for URD registries.

Five Days Granulocyte Colony-Stimulating Factor Treatment Increases Bone Formation and Reduces Gap Size of a Rat Segmental Bone Defect: A Pilot Study

Bone is an organ with high natural regenerative capacity and most fractures heal spontaneously when appropriate fracture fixation is provided. However, additional treatment is required for patients with large segmental defects exceeding the endogenous healing potential and for patients suffering from fracture non-unions. These cases are often associated with insufficient vascularization. Transplantation of CD34+ endothelial progenitor cells (EPCs) has been successfully applied to promote neovascularization of bone defects, however including extensive ex vivo manipulation of cells. Here, we hypothesized, that treatment with granulocyte colony-stimulating factor (G-CSF) may improve bone healing by mobilization of CD34+ progenitor cells into the circulation, which in turn may facilitate vascularization at the defect site. In this pilot study, we aimed to characterize the different cell populations mobilized by G-CSF and investigate the influence of cell mobilization on the healing of a critical size femoral defect in rats. Cell mobilization was investigated by flow cytometry at different time points after five consecutive daily G-CSF injections. In a pilot study, bone healing of a 4.5-mm critical femoral defect in F344 rats was compared between a saline-treated control group and a G-CSF treatment group. In vivo microcomputed tomography and histology were applied to compare bone formation in both treatment groups. Our data revealed that leukocyte counts show a peak increase at the first day after the last G-CSF injection. In addition, we found that CD34+ progenitor cells, including EPCs, were significantly enriched at day 1, and further increased at day 5 and day 11. Upregulation of monocytes, granulocytes and macrophages peaked at day 1. G-CSF treatment significantly increased bone volume and bone density in the defect, which was confirmed by histology. Our data show that different cell populations are mobilized by G-CSF treatment in cell specific patterns. Although in this pilot study no bridging of the critical defect was observed, significantly improved bone formation by G-CSF treatment was clearly shown.

A novel association between relaxin receptor polymorphism and hematopoietic stem cell yield after mobilization

Mobilization of hematopoietic stem cells (HSCs) from the bone marrow to the peripheral blood is a complex mechanism that involves adhesive and chemotactic interactions of HSCs as well as their bone marrow microenvironment. In addition to a number of non-genetic factors, genetic susceptibilities also contribute to the mobilization outcome. Identification of genetic factors associated with HSC yield is important to better understand the mechanism behind HSC mobilization. In the present study, we enrolled 148 Korean participants (56 healthy donors and 92 patients) undergoing HSC mobilization for allogeneic or autologous HSC transplantation. Among a total of 53 polymorphisms in 33 candidate genes, one polymorphism (rs11264422) in relaxin/insulin-like family peptide receptor 4 (RXFP4) gene was significantly associated with a higher HSC yield after mobilization in Koreans. However, in a set of 101 Europeans, no association was found between circulating CD34+ cell counts and rs11264422 genotype. Therefore, we suggest that the ethnic differences in subjects’ genetic background may be related to HSC mobilization. In conclusion, the relaxin—relaxin receptor axis may play an important role in HSC mobilization. We believe that the results of the current study could provide new insights for therapies that use relaxin and HSC populations, as well as a better understanding of HSC regulation and mobilization at the molecular level.

Factors affecting hematopoietic stem cell mobilization and apheresis in allogeneic donors: The role of iron status

Infused CD34 cell count has a significant impact on transplant outcome. In this retrospective study, we aimed to analyze the impact of donor iron parameters on peripheral blood stem cell (PBSC) collection. A total of 303 related donors were included in the study. The mobilization regimen, recombinant G-CSF, was given for four consecutive days. A CD34⁺ cell count below 2×10⁶/kg was defined as mobilization failure which was demonstrated in 23 donors (7.6%). Mobilization failure was more frequent in female donors than male donors (13.7% vs 3.4%). Body mass index, mean corpuscular volume, hemoglobin and ferritin levels were found to be lower in donors with mobilization failure. Body mass index was significantly correlated with PBSC count on the 4th day of G-CSF. Body mass index, male gender, mean corpuscular volume and ferritin levels had significant impact on PBSC count. Although PBSC count was found to be similar between female and male donors, female gender was shown to have an adverse impact on PBSC collection, which may be attributed to lower body weight and concurrent iron deficiency.

Autologous Stem Cell Mobilization and Collection

Peripheral blood stem cell collection is an effective approach to obtain a hematopoietic graft for stem cell transplantation. Developing hematopoietic stem/progenitor cell (HSPC) mobilization methods and collection algorithms have improved efficiency, clinical outcomes, and cost effectiveness. Differences in mobilization mechanisms may change the HSPC content harvested and result in different engraftment kinetics and complications. Patient-specific factors can affect mobilization. Incorporating these factors in collection algorithms and improving assays for evaluating mobilization further extend the ability to obtain sufficient HSPCs for hematopoietic repopulation. Technological advance and innovations in leukapheresis have improved collection efficiency and reduced adverse effects.

Healthy donor hematopoietic stem cell mobilization with biosimilar granulocyte-colony-stimulating factor: safety, efficacy, and graft performance

BACKGROUND

Biosimilar granulocyte-colony-stimulating factors (G-CSFs) have been available in the European Union since 2008, and Sandoz' biosimilar filgrastim was approved in the United States in March 2015 for all of the reference product's indications except acute radiation syndrome. Biosimilar G-CSFs have been largely embraced by the medical community, except for some reservations about healthy-donor stem cell mobilization, for which use outside of clinical studies was cautioned against by some members of the scientific community.

STUDY DESIGN AND METHODS

In a two-center safety surveillance study (National Clinical Trial NCT01766934), 245 healthy volunteer stem cell donors were enrolled. Of 244 donors who began mobilization with twice-daily Sandoz biosimilar filgrastim, 242 received a full (n = 241) or partial (n = 1) course of G-CSF and underwent apheresis. Efficacy and safety were assessed and are reported here.

RESULTS

Biosimilar filgrastim was accompanied by the typical G-CSF class-related adverse effects of expected frequency and severity. Median mobilization for CD34-positive stem cells was 97/µL (range, 20-347/µL); after one apheresis (91%) or two aphereses (9%) from all but three donors (1.2%), cell doses in excess of the typical 4 × 10⁶ CD34-positive cells/kg of the recipient had been collected (range, 3-52 × 10⁶ /kg). Biochemical and hematologic alterations were consistent with previous reports; all had normalized by the first follow-up 1 month after mobilization. Stem cell products engrafted with typical probability and kinetics for G-CSF-mobilized stem cell products.

CONCLUSION

These data support the use of biosimilar filgrastim for healthy-donor stem cell mobilization as safe and effective.