Defining "poor mobilizer" in pediatric patients who need an autologous peripheral blood progenitor cell transplantation

PEGylated Granulocyte Colony-Stimulating Factor and Plerixafor Enhance Autologous Stem and Progenitor Cell Mobilization and Transplantation in Pediatric Patients

Autologous hematopoietic stem cell transplantation is used to restore bone marrow function after high-dose chemotherapy. For apheresis, granulocyte colony-stimulating factor (G-CSF) is standard of care, but obtaining sufficient stem cells can be challenging. Other mobilization agents include plerixafor and PEGylated G-CSF (PEG-G-CSF). While efficacy of these is established in adults, limited data for their use in pediatric patients are available. Here, we compare Good versus Poor Mobilizers and study success of different mobilization regimens in regard to CD34+cell-collection, -quality, -phenotype and hematologic reconstitution in pediatric patients. In this multi-center retrospective study, we analyzed data of 278 patients with solid tumors and lymphoma, mobilized with either G-CSF (n = 224), PEG-G-CSF (n = 34), or G-CSF/PEG-G-CSF with additional plerixafor (n = 20). In Poor Mobilizers (13.7% of all patients), addition of plerixafor to G-CSF augmented CD34+cell collection, without adverse effects on hematologic reconstitution and CD34+cell quality. PEG-G-CSF-aided mobilization was successful as first-line treatment in two-thirds of patients and did not impair hematological reconstitution, compared to G-CSF-only. Within the Poor Mobilizer group, G-CSF+plerixafor increased primitive (CD45RA-CD38-CD90+CD49f+) and CXCR4-expressing CD34+cells in apheresis products compared to G-CSF-only, without exceeding levels of Good Mobilizers. No plerixafor-related increase in tumor cells was observed in apheresis products. In conclusion, our comprehensive study supports the use of plerixafor and furthermore demonstrates the potential of patient-friendly PEG-G-CSF for mobilization of pediatric patients.

Peripheral blood stem cell harvesting in young children weighing less than 15 kg

Autologous peripheral blood stem cell (PBSC) transplantation is crucial in pediatric cancer treatment, and tandem transplantation is beneficial in certain malignancies. Collecting PBSCs in small children with low body weight is challenging. We retrospectively analyzed data of pediatric cancer patients weighing <15 kg who underwent autologous PBSC harvesting in our hospital. Collections were performed in the pediatric intensive care unit over 2 or 3 consecutive days, to harvest sufficient stem cells (goal ≥2 × 106 CD34+ cells/kg per apheresate). From April 2006 to August 2021, we performed 129 collections after 50 mobilizations in 40 patients, with a median age of 1.9 (range, 0.6-5.6) years and a body weight of 11.0 (range, 6.6-14.7) kg. The median CD34+ cells in each apheresate were 4.2 (range, 0.01-40.13) × 106/kg. 78% and 56% of mobilizations achieved sufficient cell dose for single or tandem transplantation, respectively, without additional aliquoting. The preapheresis hematopoietic progenitor cell (HPC) count was highly correlated with the CD34+ cell yield in the apheresate (r = 0.555, P < 0.001). Granulocyte colony-stimulating factor alone was not effective for mobilization in children ≥2 years of age, even without radiation exposure. By combining the preapheresis HPC count ≥20/μL and the 3 significant host factors, including age <2 years, no radiation exposure and use of chemotherapy, the prediction rate of goal achievement was increased (area under the curve 0.787).

Autologous peripheral blood stem cell harvest timing by absolute neutrophil count in children and young adult patients: Single-institute experience

BACKGROUND

Myeloablative, high-dose chemotherapy followed by autologous peripheral blood stem cell transplantation (PBSCT) improves outcome in some high-risk malignant solid tumors and lymphomas in children and young adults.

METHODS

We performed 16 peripheral blood stem cell (PBSC) harvests in 12 children and 2 young adult patients with a high-risk malignant solid tumor or refractory/relapsed Hodgkin's lymphoma from August 2015 to December 2020. In our chemotherapy mobilization protocol, we used an absolute neutrophil count (ANC) of >1 × 109/L following the nadir after chemotherapy as the criterion for undertaking the apheresis.

RESULTS

The median CD34+ cell count per kg body weight of the 33 apheresis products was 4.92 × 106 cells/kg (range, 0.34-22.53 × 106 cells/kg). Thirteen of the 14 patients (93%) had successful PBSC collections that met their goals for PBSCT. Three patients did not receive PBSCT due to disease progression prior to transplantation. Prompt engraftment occurred in all the remaining 11 patients with 17 PBSCTs.

CONCLUSION

Our data suggest that ANC can be helpful as a surrogate parameter in clinical decision-making when the peripheral blood CD34+ count is unavailable.

Autologous peripheral blood stem cell mobilization and apheresis in pediatric patients with cancer: A single-center report of 64 procedures

BACKGROUND

The published experience concerning autologous peripheral blood stem cell collection in children is very limited.

METHODS

The data of pediatric patients who underwent autologous stem cell mobilization and apheresis between January 2011 and April 2020 were analyzed retrospectively.

RESULTS

We studied retrospectively 64 mobilization and apheresis procedures in 48 pediatric patients (34 males, 14 females), mean age of 7.31 ± 5.38 (range, 1.5-19.7) years, the underlying disease was mostly neuroblastoma (NBL). The body weight of 21 patients (43.75%) was 15 kg or less. The targeted autologous peripheral stem cell apheresis (APSCA) was successfully achieved in 98% of patients. Neuroblastoma patients were younger than the rest of the patients and underwent apheresis after receiving fewer chemotherapy cycles than others and all of them mobilized within the first session successfully. Plerixafor was added to mobilization in nine heavily pretreated patients (18.7%), median two doses (range, 1-4 doses). 11 patients (22.9%) underwent radiotherapy (RT) before mobilization with doses of median 24 Gy (range, 10.8-54.0 Gy). Patients with RT were older at the time of apheresis and had received more chemotherapy courses than patients without RT. As a result, patients with a history of RT had significantly lower peripheral CD34+ cells and CD34+ yields than those without RT. In 17 patients (35.4%), 22 different complications were noted. The most common complications were catheter-related infections (n:10, 20.8%), followed by catheter-related thrombosis in eight patients (16.7%).

CONCLUSIONS

Patients who had far less therapy before apheresis were more likely to mobilize successfully. Our study provides a detailed practice approach including complications during APSCA aiming to increase the success rates of apheresis in transplantation centers.

Prediction of success of CD34+ collection for autotransplantation in children

INTRODUCTION

Intensive chemotherapy with autologous stem cell transplantation is a therapeutic tool used in paediatric oncology. In adult patients, a peripheral blood CD34+ cell count superior to 20/μL enables an adequate collection of peripheral blood stem cells. There are no recommendations for children. This study aimed to determine whether the count of circulating CD34+ cells on the day before cytapheresis predicts successful collection in paediatric patients.

METHODS

We retrospectively studied all paediatric patients who underwent apheresis for stem cell autotransplantation in the CHU of Rennes between 2010 and 2019. Successful apheresis was defined as a collection superior to 3×10⁶ CD34+/kg. "Success" and "failure" groups were compared.

RESULTS

In total, 122 apheresis procedures were performed in 105 patients. It was a successful procedure in 81% of patients and a failure in 19% of patients. A minimal cut-off of circulating CD34+ count superior to 13/μL on D-1 allowed us to predict a collection of at least 3×10⁶ CD34+/kg (PPV 94,8%, NPV 51,4%). For children aged<6 years, the association with leucocyte increase during the 5 days before the procedure improved the prediction of success.

DISCUSSION

The peripheral blood CD34+ cell count is a predictive factor for successful collection in paediatric patients. The minimal cut-off that allows an adequate collection of peripheral blood stem cells is inferior to the minimal cut-off in adult patients. Nevertheless, this minimal number of circulating CD34+ cells is insufficient to predict the success or failure of apheresis in patients younger than 6 years of age.

Adverse events related to central venous catheters (CVC) and the influence of CVC characteristics on peripheral blood hematopoietic progenitor cell collection in children

Introduction

The use of peripheral blood progenitor cells (PBPCs) as a source for hematopoietic stem cell transplantation (HSCT) in pediatric healthy donors is still under debate. The risk of a central venous catheter (CVC) placement and catheter-related complications continue to be the main arguments to discourage its use.

Methods

we present a retrospective analysis of 140 PBPC collections in pediatric patients and donors, describing adverse events (AE) related to CVCs as well as the influence of catheterrelated variables on the efficiency of the leukapheresis.

Results

14 CVC-related AEs were recorded (10%). The most common was fever in 5 patients, 4 of which had a catheter-related bacteriemia. Thrombotic events were only observed in 3 patients with active malignancy. A healthy donor presented a moderate bleeding after catheter withdrawal that resolved with local measures, and none of the rest presented any AE. Regarding variables related to the development of AEs, the subject group (patient or donor) was the only one significantly associated (p < 0.0001). Of interest, efficiency was also related to catheter location, being worse in those located in the femoral vein than in into the jugular or the subclavian veins (p < 0.05). In a multivariate analysis, the only variable significantly associated was catheter size (beta 0.238, p < 0.01).

Discussion

Placing a CVC for PBPC collection in pediatric subjects is overall safe; CVC-related complications in pediatric healthy donors are very rare. Furthermore, we should try to place catheters of the largest caliber possible, since the efficiency of the collection is related to this variable.

Development and validation of a predictive model to guide the use of plerixafor in pediatric population

Plerixafor, a CXCR4 receptor antagonist, reduces the binding and chemotaxis of hematopoietic stem cells to the bone marrow stroma, resulting in predictable peak of cluster of differentiation 34⁺ (CD34⁺) cells in the peripheral blood (PB) approximately 10 h after its administration. We developed a model that could predict the CD34⁺ harvest volume on the first day of apheresis (AP-CD34⁺) based on PB-CD34⁺ counts immediately prior to commencing apheresis in pediatric population. In all, data from 45 pediatric patients from the MOZAIC study who received either granulocyte colony-stimulating factor (G-CSF) alone or G-CSF plus plerixafor were included. The modeling of the data exhibited a strong and highly predictive linear relationship between the counts of PB-CD34⁺ cells on the first day of apheresis and AP-CD34⁺ cells collected on the same day. It is predicted that there are approximately 13 new collected CD34⁺ cells for 100 new circulating CD34⁺ cells before apheresis. Our predictive algorithm can be used to quantify the minimal count of PB-CD34⁺ cells that enables to collect at least 2 × 10⁶ or 5 × 10⁶ AP-CD34⁺ cells/kg with sufficient assurance (probability = 0.90) and can guide the use of plerixafor in patients at higher perceived risk for mobilization failure. Trial registration of MOZAIC study: ClinicalTrials.gov, NCT01288573; EudraCT, 2010-019340-40.

Mobilization with high-dose granulocyte colony-stimulating factor alone at 12 μg/kg twice a day in high-risk pediatric patients: A retrospective analysis of the experience in a single center

INTRODUCTION

Mobilization regimes in pediatric patients at high risk for poor mobilization are not standardized across different institutions. We present a retrospective analysis of our experience with a high-dose granulocyte colony-stimulating factor (G-CSF) regime of 12 μg/Kg per body weight (BW) twice a day for 4 days used in high-risk patients.

MATERIAL AND METHODS

We report the results of all pediatric patients mobilized with high-dose G-CSF between January 1999 and February 2021 in our center. A successful mobilization was defined as a peripheral blood (PB) CD34⁺ cell count of ≥10 CD34⁺ cells/μl on the fifth day of mobilization immediately before leukapheresis. A minimum cell yield of ≥2 × 10⁶ CD34⁺ cells/Kg of BW was required for a successful collection.

RESULTS

Of the 262 patients included in the analysis, mobilization failure was found in 27 (10.3%). In a univariate analysis, this was associated with age, weight, baseline diagnosis, and having undergone a previous mobilization cycle, the latter being the only factor that remained significantly associated in a multivariate analysis (P = 0.03). The 54 patients (20.6%) did not reach the minimum required CD34⁺ cell yield. 50.4% of the patients reported adverse events (AEs) during the mobilization period, and 23 (9.1%) reported 3 or more concomitant AEs. However, all of them were mild and did not affect the mobilization schedule.

CONCLUSIONS

Although most high-risk pediatric patients are successfully mobilized with the high-dose G-CSF regime, this approach does not salvage all of them and significantly increases the presence of AEs in comparison to standard-dose regimes.

Plerixafor stem cell mobilization in Japanese children: A post-marketing study

BACKGROUND

Plerixafor is approved in Japan for hematopoietic stem cell mobilization prior to autologous transplant, but limited data are available on the use in children. This study evaluates the safety and effectiveness of plerixafor in Japanese children aged <15 years.

METHODS

A multicenter, post-marketing surveillance study was conducted in Japan to evaluate the safety and effectiveness of plerixafor in routine clinical practice. This subgroup analysis examined the safety and effectiveness of plerixafor administered as a once-daily, subcutaneous injection in children aged <15 years. The primary effectiveness outcome was the proportion of patients with 2 × 10⁶ cells CD34+ cells/kg collected via apheresis within 4 days.

RESULTS

Eighteen patients with solid tumors were included in this analysis; (median age 6.0 years, range, 1-13 years). In addition to granulocyte colony-stimulating factor, all patients had received chemotherapy immediately prior to plerixafor administration. The mean (SD) daily dose of plerixafor was 0.24 (0.01) mg/kg. Seven of the 18 patients (38.9%) developed adverse drug reactions (ADRs), all occurring in patients aged ≥6 years and weighing ≥16 kg. The most common ADRs were pyrexia (n = 4), vomiting (n = 3), nausea (n = 2), and abdominal pain (n = 2). Twelve patients (66.7%) achieved a CD34+ cell count ≥2 × 10⁶ cells/kg within 4 days after the start of plerixafor administration.

CONCLUSIONS

The results provide an encouraging sign that plerixafor 0.24 mg/kg may be safe and effective in pediatric patients in routine clinical practice in Japan, but further research in larger studies is needed.

Peripheral blood stem and progenitor cell collection in pediatric candidates for ex vivo gene therapy: a 10-year series

Hematopoietic stem and progenitor cell (HSPC)-based gene therapy (GT) requires the collection of a large number of cells. While bone marrow (BM) is the most common source of HSPCs in pediatric donors, the collection of autologous peripheral blood stem cells (PBSCs) is an attractive alternative for GT. We present safety and efficacy data of a 10-year cohort of 45 pediatric patients who underwent PBSC collection for backup and/or purification of CD34⁺ cells for ex vivo gene transfer. Median age was 3.7 years and median weight 15.8 kg. After mobilization with lenograstim/plerixafor (n = 41) or lenograstim alone (n = 4) and 1−3 cycles of leukapheresis, median collection was 37 × 10⁶ CD34⁺ cells/kg. The procedures were well tolerated. Patients who collected ≥7 and ≥13 × 10⁶ CD34⁺ cells/kg in the first cycle had pre-apheresis circulating counts of at ≥42 and ≥86 CD34⁺ cells/μL, respectively. Weight-adjusted CD34⁺ cell yield was positively correlated with peripheral CD34⁺ cell counts and influenced by female gender, disease, and drug dosage. All patients received a GT product above the minimum target, ranging from 4 to 30.9 × 10⁶ CD34⁺ cells/kg. Pediatric PBSC collection compares well to BM harvest in terms of CD34⁺ cell yields for the purpose of GT, with a favorable safety profile.

Plerixafor combined with G-CSF for stem cell mobilization in children qualified for autologous transplantation- single center experience

Failure of autologous peripheral blood CD34⁺ stem cells collection can adversely affect the treatment modality for patients with hematological and nonhematological malignant diseases where high dose chemotherapy followed by hematopoietic stem cell transplantation has become part of their treatment. Plerixafor in conjunction with G-CSF is approved for clinical use as a mobilization agent. The clinical efficacy of Plerixafor in CD34⁺ cells collection was analyzed in our institution. A total of 13 patients aged 1-15,5 years received Plerixafor in combination with G-CSF: 7 with neuroblastoma, 2 with Ewing's sarcoma and single patients with Hodgkin's lymphoma, germ cell tumor, retinoblastoma and Wilms tumor. Twelve patients (923%) achieved CD34+ cell counts of ≥ 20 × 10⁶/L after 1-7 doses of Plerixafor. The average 9,9 - fold increase in number of CD34⁺ cells were achieved following the first dose and 429 - fold after second dose of plerixafor. Among the 13 patients, 12 yielded the minimum required cell collection of 2 × 10⁶/kg within an average of 2 doses of Plerixafor. The mean number of apheresis days was 1.75. The median total number of collected CD34⁺ cells was 982 × 10⁶/kg. Plerixafor enables rapid and effective mobilization, and collection of sufficient number of CD34⁺ cells.

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.

Plerixafor combined with standard regimens for hematopoietic stem cell mobilization in pediatric patients with solid tumors eligible for autologous transplants: two-arm phase I/II study (MOZAIC)

This study (NCT01288573) investigated plerixafor's safety and efficacy in children with cancer. Stage 1 investigated the dosage, pharmacokinetics (PK), pharmacodynamics (PD), and safety of plerixafor + standard mobilization (G-CSF ± chemotherapy). The stage 2 primary endpoint was successful mobilization (doubling of peripheral blood CD34+ cell count in the 24 h prior to first apheresis) in patients treated with plerixafor + standard mobilization vs. standard mobilization alone. In stage 1, three patients per age group (2-<6, 6-<12, and 12-<18 years) were treated at each dose level (160, 240, and 320 µg/kg). Based on PK and PD data, the dose proposed for stage 2 was 240 µg/kg (patients 1-<18 years), in which 45 patients were enrolled (30 plerixafor arm, 15 standard arm). Patient demographics and characteristics were well balanced across treatment arms. More patients in the plerixafor arm (24/30, 80%) met the primary endpoint of successful mobilization than in the standard arm (4/14, 28.6%, p = 0.0019). Adverse events reported as related to study treatment were mild, and no new safety concerns were identified. Plerixafor + standard G-CSF ± chemotherapy mobilization was generally well tolerated and efficacious when used to mobilize CD34+ cells in pediatric cancer patients.

Regulatory systems in bone marrow for hematopoietic stem/progenitor cells mobilization and homing

Regulation of hematopoietic stem cell release, migration, and homing from the bone marrow (BM) and of the mobilization pathway involves a complex interaction among adhesion molecules, cytokines, proteolytic enzymes, stromal cells, and hematopoietic cells. The identification of new mechanisms that regulate the trafficking of hematopoietic stem/progenitor cells (HSPCs) cells has important implications, not only for hematopoietic transplantation but also for cell therapies in regenerative medicine for patients with acute myocardial infarction, spinal cord injury, and stroke, among others. This paper reviews the regulation mechanisms underlying the homing and mobilization of BM hematopoietic stem/progenitor cells, investigating the following issues: (a) the role of different factors, such as stromal cell derived factor-1 (SDF-1), granulocyte colony-stimulating factor (G-CSF), and vascular cell adhesion molecule-1 (VCAM-1), among other ligands; (b) the stem cell count in peripheral blood and BM and influential factors; (c) the therapeutic utilization of this phenomenon in lesions in different tissues, examining the agents involved in HSPCs mobilization, such as the different forms of G-CSF, plerixafor, and natalizumab; and (d) the effects of this mobilization on BM-derived stem/progenitor cells in clinical trials of patients with different diseases.