Peripheral Blood Stem Cell Products Research Articles

Quality Assessment of Cryopreserved Peripheral Blood Stem Cell Products: Evaluation of Two Methods for Flow Cytometric Viability Testing

ABSTRACTIntroductionThe standard flow cytometry method for viability testing using 7‐aminoactinomycin D (7‐AAD) determines cells in necrosis and late apoptosis. The colony‐forming unit (CFU) assay, which evaluates the proliferation ability of HSCs, is also used in graft quality assessment despite known deficiencies that make this assay impractical in routine clinical settings. The aim was to compare the effectiveness of the flow cytometry 7‐AAD/annexin V method with the 7‐AAD method in assessing the quality of HSCs in autologous and allogeneic peripheral blood stem cell (PBSC) products.MethodsThirty autologous and 30 allogeneic fresh and thawed cryopreserved PBSC products were included in this study. The viability of HSCs was determined using the 7‐AAD method and 7‐AAD/annexin V method on a flow cytometer, while their clonogenic capacity was assessed by CFU assay.ResultsThere was an excellent correlation for CD34+ cell viability between the 7‐AAD and the 7‐AAD/annexin V method for fresh samples (Rs = 0.930, p < 0.001) and a good correlation for thawed PBSC samples (Rs = 0.739, p < 0.001). Excellent correlation was observed for post‐thaw CD34+ cell recovery between the two methods for viability (Rs = 0.980, p < 0.001). Statistical analysis showed a weak correlation between CFU‐GM recovery and CD34+ cell recovery, regardless of which viability testing method was used (7‐AAD method p = 0.021, Rs = 0.298; 7‐AAD/annexin V method p = 0.029, Rs = 0.282).ConclusionsResults of this study showed that in the quality assessment of cryopreserved PBSC product viability, the 7‐AAD/annexin V method had no added value compared to the 7‐AAD method, which was suitable enough for routine quality control of cryopreserved autologous and allogeneic PBSC samples.

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

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. 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. 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). 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.

Identifying Candidates for Effective Utilization of Stored Autologous PBSCs in Salvage Transplantation for Multiple Myeloma: Who Benefits Most?

Background/Objectives: High-dose chemotherapy (HD-CHT) followed by autologous stem cell transplantation (ASCT) remains the gold standard for eligible multiple myeloma (MM) patients, even amidst evolving therapeutic options. Clinical trials have demonstrated ASCT's efficacy in MM, including its potential as salvage therapy after prolonged remission. Peripheral blood stem cells (PBSCs) are now the primary source of hematopoietic stem cells for ASCT. Collecting additional PBSCs post-initial myeloablative conditioning is challenging, leading many centers to adopt the practice of collecting and storing excess PBSCs during initial therapy to support tandem transplants or salvage treatments. The use of salvage ASCT may diminish in the face of novel, highly effective treatments like bispecific antibodies and cellular therapies for relapsed/refractory MM (RRMM). Despite available stored PBSC grafts, salvage ASCTs are underutilized due to various factors, including declining performance status and therapy-related comorbidities. A cost utilization analysis from 2013 revealed that roughly 70% of patients had unused PBSC products in prolonged cryopreservation, costing a significant portion of total ASCT expenses. The average cost for collecting, cryopreserving, and storing PBSCs exceeded $20,000 per person, with more than $6700 spent on unused PBSCs for a second ASCT. A more recent analysis from 2016 underscored the declining need for salvage ASCT, with less than 10% of patients using stored PBSC grafts over a decade. Methods: To address the dilemma of whether backup stem cells remain necessary for myeloma patients, the study investigated strategies to reduce the financial burden of PBSC collection, processing, and storage. It evaluated MM patients undergoing frontline ASCT from January 2012 to June 2022, excluding those with planned tandem transplants and those who had a single ASCT with no stored cells. Discussion: Among the 240 patients studied, the median age at PBSC collection was 61. Notably, only 7% underwent salvage ASCT, with nearly 90% of salvage ASCT recipients being ≤ 61 years old at the time of initial ASCT. The study revealed a decreasing trend in salvage ASCT use with increasing age, suggesting that PBSC collection for a single transplant among elderly patients (>60 years old) could be a cost-effective alternative. Most transplant centers aimed to collect 10 × 106 CD34 + cells/kg, with patients over 65 often requiring multiple collection days. Shifting towards single-transplant collections among the elderly could reduce costs and resource requirements. Additionally, the study recommended implementing strategies for excess PBSC disposal or repurposing on the collection day to avoid additional storage costs. In summary, the decreasing utilization of salvage ASCT in MM, alongside financial considerations, underscores the need for revised stem cell collection policies. Conclusions: The study advocates considering single-transplant PBSC collections for elderly patients and efficient management of excess PBSCs to optimize resource utilization.

Safety and efficacy of peripheral blood stem cells collection in healthy children and pediatric patients with thalassemia major weighing 20 kg or less.

Peripheral blood stem cell (PBSC) collection in children poses challenges due to their small size, low body weight (BW), and unique pediatric physiology, especially among children weighing 20 kg (kg) or less. PBSC collection data of both healthy children and patients with thalassemia major (TM) weighing 20 kg or less between January 2013 and December 2020 were reviewed. Moreover, PBSCs characteristics along with various aspects of efficiency and safety between healthy donors and patients with TM were compared. A total of 262 PBSC procedures were performed on 255 children. Of these, 91 procedures were carried out on 85 allogeneic healthy donors, and 171 auto-backup collections were performed on 170 patients with TM to ensure PBSC availability and prevent transplantation failure. A minimum pre-apheresis hemoglobin (HGB) level of 60 g/L was discovered to be safe and feasible in patients with TM. The median CD34+ cell dose in the PBSC product during the initial apheresis procedure was higher in healthy donors compared to patients with TM (7.29 ± 5.28 × 106 cells/kg vs5.88 ± 4.23 × 106 cells/kg, P = .043). The total CD34+ cells/kg recipient weight exhibited a positive correlation with pre-apheresis monocyte counts, but a negative correlation with donor weight. Apheresis significantly reduced hematocrit and platelet counts in the allogeneic group compared to the autologous group. Patients with TM experienced a higher occurrence of bone pain related to granulocyte colony-stimulating factor treatment. Notably, no serious complications related to PBSCs mobilization, central venous catheter placement, or the apheresis procedure were observed in either group. PBSCs collection was both safe and effective in healthy children and pediatric patients with TM weighing 20 kg or less.

Assessment and comparison of viability assays for cellular products

Background aimsAccurate assessment of cell viability is crucial in cellular product manufacturing, yet selecting the appropriate viability assay presents challenges due to various factors. This study compares and evaluates different viability assays on fresh and cryopreserved cellular products, including peripheral blood stem cell (PBSC) and peripheral blood mononuclear cell (PBMC) apheresis products, purified PBMCs and cultured chimeric antigen receptor and T-cell receptor-engineered T-cell products. MethodsViability assays, including manual Trypan Blue exclusion, flow cytometry-based assays using 7-aminoactinomycin D (7-AAD) or propidium iodide (PI) direct staining or cell surface marker staining in conjunction with 7-AAD, Cellometer (Nexcelom Bioscience LLC, Lawrence, MA, USA) Acridine Orange/PI staining and Vi-CELL BLU Cell Viability Analyzer (Beckman Coulter, Inc, Brea, CA, USA), were evaluated. A viability standard was established using live and dead cell mixtures to assess the accuracy of these assays. Furthermore, precision assessment was conducted to determine the reproducibility of the viability assays. Additionally, the viability of individual cell populations from cryopreserved PBSC and PBMC apheresis products was examined. ResultsAll methods provided accurate viability measurements and generated consistent and reproducible viability data. The assessed viability assays were demonstrated to be reliable alternatives when evaluating the viability of fresh cellular products. However, cryopreserved products exhibited variability among the tested assays. Additionally, analyzing the viability of each subset of the cryopreserved PBSC and PBMC apheresis products revealed that T cells and granulocytes were more susceptible to the freeze–thaw process, showing decreased viability. ConclusionsThe study demonstrates the importance of careful assay selection, validation and standardization, particularly for assessing the viability of cryopreserved products. Given the complexity of cellular products, choosing a fit-for-purpose viability assay is essential.

Comparison of Biosimilar Filgrastim (Nivestym) Versus Originator Filgrastim (Neupogen) for Peripheral Blood Stem Cell Mobilization for Allogeneic Hematopoietic Stem Cell Transplantation

Background: Allogeneic hematopoietic stem cell transplantation (HSCT) is an optimal and potentially curative therapy for patients with hematologic malignancies. Granulocyte colony-stimulating factor (G-CSF) is used for the mobilization of peripheral blood stem cells (PBSCs) in allogeneic donors, and an optimal CD34 cell dose plays a critical role in successful transplantation. Nivestym, a biosimilar G-CSF to the originator Filgrastim (Neupogen), is now used by multiple institutions as it has become more available; however, there is a lack of data in this regard among healthy donors for allogeneic HSCT mobilization. In this study, we aim to compare the efficacy of Nivestym compared to Neupogen for allogeneic donor PBSC mobilization. Methods: For this retrospective single-center study, we included all (n=541) adult allogeneic HSCT donors at the University of Kansas Medical Center receiving Nivestym (January 2013-July 2020) or Neupogen (July 2020-June 2023) for donor PBSC mobilization. We conducted a bivariate analysis utilizing the ANOVA test. Statistical analyses were performed using SPSS version 28. Statistical significance was determined at p&amp;lt;0.05. Results: Our study included 541 allogeneic HSCT donors who received Neupogen (n=345, 64%) or Nivestym (n=196, 36%) for PBSC mobilization. The median age was 47 (range 17-76) years. The median donor weight was 86 (95% CI 87-91) kilograms. Donors receiving Neupogen had similar pre-GCSF WBC count (median 45 vs 47 K/uL, p=0.739), pre-GCSF CD34 percentages (median 17% vs 17%, p=0.527), and pre-GCSF circulating CD34 count (median 74 vs 74 million cells/kg, p=0.842) compared to donors receiving Nivestym. Neupogen recipients had similar median PBSC product total neutrophil count (TNC, 6.8 vs 6.5 K/uL, p=0.347), product CD34 percentage (75% vs 79%, p=0.068), absolute CD34 count (503 vs 533 million cells, p=0.636), and final CD34 dose (6.1 vs 6.3 million cells/kg, p=0.365) compared to Nivestym recipients. Seven percent (n=28) of donors needed two days of PBSC collection to achieve the target PBSC dose, with a statistically similar proportion noted in Neupogen (n=25, 7.3%) and Nivestym (n=13, 6.6%) cohorts. In a subgroup analysis stratified by age, donors aged 35 or older (n=154) had similar responses in all mentioned variables (p&amp;gt;0.05); however, for donors under the age of 35 years, the CD34 dose was higher in donors receiving Neupogen compared to Nivestym (median 6.9 vs 6.3 million cells/kg, p=0.044). Most of the PBSC collections (98%) were completed in one day, except for five donors in both Neupogen (5%) and Nivestym (8.5%) cohorts. Conclusions: Biosimilar G-CSF (Nivestym) demonstrated similar efficacy for peripheral blood stem cell mobilization compared to the originator G-CSF (Neupogen) among allogeneic HSCT donors. In donors aged 35 years or younger, a slightly lower PBSC product CD34 count was noted with Nivestym compared to Neupogen.

Clonal Hematopoiesis and Cardiovascular Disease in Patients With Multiple Myeloma Undergoing Hematopoietic Cell Transplant

There is a paucity of information on the association between clonal hematopoiesis of indeterminate potential (CHIP) and cardiovascular disease (CVD) in patients with cancer, including those with multiple myeloma (MM) undergoing hematopoietic cell transplant (HCT), a population at high risk of developing CVD after HCT. To examine the association between CHIP and CVD in patients with MM and to describe modifiers of CVD risk among those with CHIP. This was a retrospective cohort study of patients with MM who underwent HCT between 2010 and 2016 at City of Hope Comprehensive Cancer Center in Duarte, California, and had pre-HCT mobilized peripheral blood stem cell (PBSC) products cryopreserved and accessible for CHIP analyses. The study team performed targeted panel DNA sequencing to detect the presence of CHIP (variant allele frequency 2% or more). The primary end point was the 5-year cumulative incidence and risk for developing de novo CVD (heart failure, coronary artery disease, or stroke) after HCT. Of 1036 consecutive patients with MM (580 male [56%]; median age, 60.0 years) who underwent a first autologous HCT, 201 patients had at least 1 CHIP variant (19.4%) and 35 patients had 2 or more variants (3.4%). The 5-year incidence of CVD was significantly higher in patients with CHIP (21.1% vs 8.4%; P < .001) compared with those without CHIP; the 5-year incidence among those with 2 or more variants was 25.6%. In the multivariable model, CHIP was associated with increased risk of CVD (hazard ratio [HR], 2.72; 95% CI, 1.70-4.39), as well as of individual outcomes of interest, including heart failure (HR, 4.02; 95% CI, 2.32-6.98), coronary artery disease (HR, 2.22; 95% CI, 1.06-4.63), and stroke (HR, 3.02; 95% CI, 1.07-8.52). Patients who had both CHIP and preexisting hypertension or dyslipidemia were at nearly 7-fold and 4-fold increased risk of CVD, respectively (reference: no CHIP, no hypertension, or dyslipidemia). CHIP was significantly and independently associated with risk of CVD in patients with MM undergoing HCT and may serve as a novel biologically plausible biomarker for CVD in this cohort. Patients with MM and both CHIP and cardiovascular risk factors had an exceptionally high risk of CVD. Additional studies are warranted to determine if cardiovascular preventive measures can reduce CHIP-associated CVD risk.

The Peripheral Blood Stem Cell Immunome Demonstrates Abnormal Immune Effector Cells Early in the Disease Course of Multiple Myeloma and Contributes to Inferior Outcomes and Secondary Myeloid Neoplasms

Background: Upfront autologous stem cell transplant (ASCT) is the standard-of-care for newly diagnosed multiple myeloma (MM) patients. However, relapse and the development of therapy-related myeloid neoplasms (t-MN) post ASCT results in considerable morbidity and mortality. We hypothesized that enrichment of abnormal myeloid progenitors and immune effector cells (IEC) in peripheral blood stem cells (PBSCs) of patients with MM is associated with a higher risk of relapse and development of t-MN. Methods: After institutional review board approval, we screened patients with active MM that were evaluated at Mayo Clinic, Rochester, MN between 01/01/2003 and 12/31/2020. Patients that underwent an ASCT and had cryopreserved PBSC product available for research were included. Using mass cytometry, we performed a comprehensive immunophenotyping of mobilized cryopreserved PBSCs from 54 MM patients undergoing 1 st ASCT, using validated antibody panel of 37 lymphoid- and myeloid-based markers each. Flow cytometry standard files were normalized and concatenated using the Fluidigm acquisition software. Flow cytometry standard files were uploaded to the OMIQ software from Dotmatics (www.omiq.ai, www.dotmatics.com), where transformation and cleaning (doublets, debris) were performed. To correct for between-sample technical variations (“batch effects”), we used fdaNorm within the omiq.ai platform. Clustering and visualization of normalized and concatenaded flowcytometry files were performed within the omiq.ai platform using PhenoGraph and UMAP, respectively. We performed principal component analysis (PCA) to identify major immunomic drivers of variability across patients. We explored the associations between immune subsets and the dichotomized clinical outcomes of interest: progression-free (PFS), myeloid neoplasm-free (MNFS) and overall survival (OS) from ASCT. A 2-sided false discovery rate adjusted P-value of &amp;lt;0.05 was considered significant when multiple comparisons were performed; otherwise, a P-value of &amp;lt;0.05 was considered significant. Results: The most abundant cell populations were T-cells (49% of the CD45 +) and myeloid cells (43% of the CD45 + cells). Clustering on the CD45 + cells revealed 30 unique lymphoid clusters and 27 unique myeloid clusters. Subclustering on NK-cells identified an additional 16 NK-cell clusters. On PCA, principal components-1 (PC-1) and 2 (PC-2) explained 15.2% and 12.5% of the variability in the data, respectively. A high PC-2 score was associated with inferior median PFS (20 vs. 52 months; P=0.005, Figure 1A), MNFS (52 vs. 85 months, P=0.03, Figure 1B) and OS (64 vs. 106 months, P=0.01) from ASCT. Immune subsets enriched in the high PC-2 cohort included the ‘NKT-like’ (CD56 +) T-cell subset which expressed the inhibitory CD159a receptor and TIGIT; a terminally differentiated (CD27/CD28 -, CD57/KLRG1 +) and exhausted (TIGIT/PD-1 +) T cell subset, 2 exhausted (TIGIT/PD-1 +) T cell subsets; an immunosenescent (CD27/CD28 -, CD57/KLRG1 +) T cell subset as well as a terminally exhausted (C27/C28 -, KLRG1/PD-1/TIGIT +) TCRgamma-delta subset. Immune subsets with high loadings within PC-1 (associated with improved clinical outcomes) consisted exclusively of CD4 + cells with early memory phenotypes (CD27/CD28/CD127 +). Abnormal expression of CD7 and HLA-DR expression on myeloid progenitor cell subsets was associated with an inferior PFS, MNFS, and OS. A NK-cell subcluster, characterized by an immature (CD56 high), inhibitory (CD159a +, NKG2A) phenotype, was enriched in patients developing t-MN (0.33% vs. 0.17%, P=0.006). Conclusion: We identify abnormal myeloid and immune effector cells in the PBSCs of patients with MM, even prior to ASCT. Patients with a PBSC product that is enriched in immunosuppressive T and myeloid cell subsets, and with a lower proportion of antigen presenting cells, progenitor populations, and anti-tumor macrophages have a shorter PFS and MNFS. This suggests that the predisposition to t-MN and inferior outcomes for MM are possibly determined early in the disease course. These findings need external validation and have the potential to guide sequencing of future treatment modalities.

Liquid Storage of Peripheral Blood Stem Cell Products: Effects of Time and Temperature on Product Quality

Unrelated donor peripheral blood stem cell (PBSC) products often require transport to distant locations, which may take up to 72 hours. Temperature is an important variable that can be controlled during PBSC storage or transport; therefore, we studied the impact of temperature on prolonged storage of clinical-grade, mobilized PBSC products. PBSC products were collected by apheresis from 3 granulocyte colony-stimulating factor-mobilized donors, split into 2 PVC blood bags of equal volume, and stored at room temperature (RT) (18°C to 25 ºC) or 4 °C (2°C to 8 ºC) for 96 hours. Samples were obtained at 24-hour intervals for pH, cell counts, flow cytometry phenotyping and viability (7AAD), and hematopoietic colony-forming units (CFU). Starting PBSC products contained 52, 65, and 38×109 total nucleated cells (TNCs), with cell concentrations of 125, 263, and 94.6×106 TNCs/mL, respectively. Product pH dropped during storage, with significantly lower values for RT stored products than for 4 ºC stored products, and was greatest in the product with the highest TNC count. The percent recovery of viable CD34+ progenitor cells, CD3+ T cells, CD4+ T helper cells, CD8+ cytotoxic T cells, CD19+ B cells, CD15+ granulocytes, CD14+ monocytes, and CD16+/56+ natural killer (NK) cells all decreased over 96 hours but decreased more dramatically in the RT group. Cell recovery differences were statistically significant at most time points for all cell populations except CD15+ granulocytes. For CD34+ cells stored at 4 °C, mean recovery from prestorage values were 97 ± 3% at 24 hours, 87 ± 4% at 48 hours, 88 ± 10% at 72 hours, and 78 ± 1% at 96 hours, compared to RT product values of 45 ± 11%, 19 ± 19%, 2 ± 2%, and 0 ± 0%, respectively. CFUs were well preserved through 96 hours at 4 ºC but not at RT. During PBSC storage, pH and content of viable CD34+ cells, T cells, B cells, monocytes, NK cells, and CFU all declined. However, at 4 ºC, viable cell recoveries are relatively well preserved, even at 72 hours, whereas RT storage resulted in rapid product deterioration. PBSC products requiring prolonged liquid storage or transport before cryopreservation or infusion should be maintained at 4 ºC.

Cryopreservation of Growth Factor-Mobilized Peripheral Blood Stem Cells Does Not Compromise Major Outcomes after Allogeneic Hematopoietic Cell Transplantation: A Single-Center Experience

During the COVID-19 pandemic, cryopreservation of allogeneic donor stem cell products ensured availability of products at the start of conditioning for hematopoietic cell transplantation (HCT). Following recommendations from unrelated donor registries, including the National Marrow Donor Program (NMDP), many centers started to cryopreserve related donor peripheral blood stem cell (PBSC) products. Throughout the process, several centers have published outcomes with cryopreserved versus fresh products, some with conflicting results. Even though cryopreservation was initially considered only a temporary measure driven by the pandemic, potential advantages include greater flexibility of transplant timing. However, concern about detrimental effects of cryopreservation including increased risks of graft rejection, relapse and consequently mortality remained. The primary objective was to describe our center's experience comparing outcomes following PBSC transplantation with cryopreserved versus fresh grafts. This was an observational case study with retrospective review comparing cryopreserved grafts (N=213), to a recent historical cohort (controls) using fresh grafts (N=167). In multivariable analyses, the adjusted hazard ratio (fresh vs. cryo) we for overall mortality was HR= 1.20 (95% confidence interval (CI), 0.79-1.82; p=0.40), for non-relapse mortality HR=0.99 (95% CI, 0.55-1.77; p=0.98), and for relapse HR=0.94 (95% CI, 0.60 -1.48; p=0.80). The adjusted hazard ratio for platelet engraftment was HR=1.31 (95% CI, 1.05-1.63; p=.02) and the odds ratio of grades III-IV acute GVHD was OR=1.75 (95% CI 1.01-3.04; p=.05) with fresh compared to cryopreserved grafts. There was no demonstrable difference in the risk of chronic GHVD. Although longer-term follow-up is needed, these data provide preliminary reassurance that in the event of another pandemic or should the logistical need arise in individual patients, cryopreservation of PBSC products constitutes a reasonably safe alternative.

Serious Stem Cell Donation Events and Recipient Adverse Reactions Related to Severe Acute Respiratory Syndrome Coronavirus 2: Review of Reports to the World Marrow Donor Association

The severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) pandemic has deeply impacted hematopoietic stem cell (HSC) donation and transplantation. Numerous changes in practice have been introduced, and monitoring the impact of these changes on donations and transplantations is of vital importance. As part of a global response to this pandemic, the World Marrow Donor Association (WMDA) asked that its member registries and cord blood banks submit SARS-CoV-2-related adverse events to the WMDA-operated Serious Product Events and Adverse Reactions (SPEAR) database. Here we review SARS-CoV-2-related SPEAR events that occurred in 2020. The WMDA SPEAR Committee reviewed reports submitted via an online tool. The Committee reviewed each report following the European Union definitions of a serious adverse event or reaction and determined the imputability and its impact. Reports submitted in 2020 were included in this analysis. A TOTAL OF: 74 such reports were received, and events were classified as donor-related (n=41; 55.4%), recipient-related (n=3; 4.1%), technical issues (n=31; 41.8%), or transport-related issues (n=4; 5.4%). Five cases appeared in multiple categories. The most frequently reported adverse events were of cells being unused. Many of these cases were caused by the uncoupling of the donation and transplantation consequent on the cryopreservation of products, as well as technical issues related to cell viability. Experience in some registries suggests that these issues have become less frequent as transplantation centers have become used to the changes in practice. Lessons learned include the importance of confirming recipient eligibility before the start of donor mobilization or collection and of minimizing the time between cell collection and transplantation. Transplantation centers should familiarize themselves with the expected cell losses when peripheral blood stem cell and bone marrow products are cryopreserved and should have validated viability assays in place for quality assurance. Reassuringly, there were no reports of donors becoming severely unwell because of G-CSF or transmission of SARS-CoV-2 to recipients and only 1 report of complete failure of transport of a donation.

The Effect of the COVID-19 Pandemic on Unrelated Allogeneic Hematopoietic Donor Collections and Safety.

The COVID-19 pandemic profoundly influenced unrelated donor (UD) allogeneic peripheral blood stem cell (PBSC) collections. Changes included efforts to minimize COVID-19 exposure to donors and cryopreservation of products. The extent to which the efficacy and safety of PBSC donations were affected by the pandemic is unknown. Prospective cohort analysis of PBSC collections comparing pre-pandemic (01 April 2019-14 March 2020) and pandemic (15 March 2020-31 March 2022) eras. Of a total of 291 PBSC collections, cryopreservation was undertaken in 71.4% of pandemic donations compared to 1.1% pre-pandemic. The mean requested CD34+ cell dose/kg increased from 4.9 ± 0.2 × 106 pre-pandemic to 5.4 ± 0.1 × 106 during the pandemic. Despite this increased demand, the proportion of collections that met or exceeded the requested cell dose did not change, and the mean CD34+ cell doses collected (8.9 ± 0.5 × 106 pre-pandemic vs. 9.7 ± 0.4 × 106 during the pandemic) remained above requested targets. Central-line placements were more frequent, and severe adverse events in donors increased during the pandemic. Cryopreservation of UD PBSC products increased during the pandemic. In association with this, requested cell doses for PBSC collections increased. Collection targets were met or exceeded at the same frequency, signaling high donor and collection center commitment. This was at the expense of increased donor or product-related severe adverse events. We highlight the need for heightened vigilance about donor safety as demands on donors have increased since the pandemic.

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.

A Single Center 25-year Experience in Autologous Peripheral Blood Stem Cell Collection: A Focus on the Collection Efficiency

Background: Harvest of hematopoietic progenitor cells via leukapheresis is being used increasingly for autologous transplantation. Adequate yield of cells per kilogram body weight of recipient is required for a successful engraftment. Collection efficiency (CE) is a useful parameter to assess quality of peripheral blood stem cell (PBSC) collection program. In this study, we report a 25-year experience in a tertiary care Hospital in Italy.&#x0D; Patients and Methods: 1,026 consecutives autologous PBSC collection procedure, performed in 763 patients, from January 1996 to December 2020 were retrospectively considered. Data regarding patients, Blood Cells Separators (BCS) , apheresis procedures and PBSC products were collected in our database. In these 25 years different BCS were adopted in our Apheresis Unit (AU). In the first period (1996-1999) we used Fresenius Com. Tec, in the central period (2000-2013) we used Cobe Spectra and in the last period (2014-2020) Spectra Optia.&#x0D; Results: As regards the evaluation of patients before leukapheresis, the most significant data was the increasing number of CD34+ cells. Considering the PBSC collection procedure, there was a progressive increase in the processed blood volume with a shorter apheresis duration. Data related to the PBSC collection demonstrated an increasing CD34+ cell yield and efficiency a raise in CE that was 43% using Fresenius COM-TEC BCS, 49% using Cobe Spectra BCS and 53% using Spectra Optia BCS. .&#x0D; Conclusions: These results were observed considering a 25-year period, thus a great number of factors likely contributing to the observed results, including technological improvement of the instrumentation for leukapheresis, increased experience of the team operating in the Apheresis Unit, improved mobilization protocols, better criteria for patients’ selection. Focusing our attention on CE we observed quite satisfactory results with a median which rose from 43% to 53% with an increase of 10% in the observation period.

Flow Cytometric Characterization of Hematopoietic Stem and Progenitor Cell Subpopulations in Autologous Peripheral Blood Stem Cell Preparations after Cryopreservation

Introduction: Autologous stem cell transplantation is a successful routine procedure with only a small number of non-engraftment cases, although the time to hematopoietic recovery may vary considerably across patients. While CD34 has been the decisive marker for enumerating hematopoietic stem and progenitor cells (HSPCs) for more than 30 years, the impact of CD34-positive cellular subpopulations in autologous HSPC grafts on hematopoietic reconstitution remains unclear. Methods: The two-color ISHAGE protocol represents the current gold standard for CD34+ cell enumeration but includes only the number of viable CD45+/CD34+ cells relative to the body weight of the recipient. We adapted a multicolor flow cytometry marker panel for advanced characterization of CD34 subpopulations in retained samples of autologous peripheral blood stem cell products (n = 49), which had been cryostored for a wide range from 4 to 15 years. The flow cytometric analysis included CD10, CD34, CD38, CD45, CD45RA, CD133, and viability staining with 7AAD. The findings were correlated with clinical engraftment data, including reconstitution of leukocytes, neutrophils, and platelets after transplantation (TPL). Results: We demonstrated that the identification of autologous HSPC subpopulations by flow cytometry after cryopreservation is feasible. Regarding the distribution of HSPC subpopulations, a markedly different pattern was observed in comparison to previously published data obtained using fresh autologous material. Our data revealed the largest ratio of lympho-myeloid progenitors (LMPPs) after freezing and thawing, followed by multipotent progenitors and erythroid-myeloid progenitors. A high ratio of LMPPs, representing an immature stage of differentiation, correlated significantly with early neutrophilic granulocyte and leukocyte engraftment (p = 0.025 and p = 0.003). Conversely, a large ratio of differentiated cells correlated with late engraftment of neutrophilic granulocytes (p = 0.024). Overall, successful engraftment was documented for all patients. Conclusion: We established an advanced flow cytometry panel to assess the differentiation ability of cryostored autologous peripheral blood stem cell grafts and correlated it with timely hematopoietic reconstitution. This approach represents a novel and comprehensive way to identify hematopoietic stem and progenitor subpopulations. It is a feasible way to indicate the engraftment capacity of stem cell products.

Impact of Mobilization Strategies on Peripheral Blood Stem Cell Collection Efficiency and Product Quality: A Retrospective Single-Center Study.

Autologous stem cell transplantation is routinely used in the management of several hematological diseases, solid tumors, and immune disorders. Peripheral blood stem cell (PBSC) collection performed by apheresis is the preferred source of stem cells. In this study, the potential impact of mobilization regimens on the performance of the Spectra Optia® continuous mononuclear cell collection system was evaluated. We performed a retrospective data analysis for patients undergoing autologous PBSC collection at the Medical University Vienna, Vienna General Hospital between September 2016 and June 2018. Collections were divided into two main groups according to the mobilization regimen received: without (210 collections) or with (99 collections) plerixafor. Assessed variables included product characteristics and collection efficiency (CE). Overall, product characteristics were similar between the groups. Median CD34+ CE2 was 50.1% versus 53.0%, and CE1 was 66.9% versus 69.9% following mobilization without and with plerixafor, respectively; the difference was not statistically significant. Simple linear regression showed a very weak positive correlation between the mobilization method and CE1 or CE2 (mobilization with plerixafor increased CE2 by 4.106%). In conclusion, the Spectra Optia® apheresis system led to high CE and a good quality of PBSC products when mobilization regimens with or without plerixafor were used.

Allogeneic Stem Cell Cryopreservation Is Associated with Equivalent Survival and Relapse Rates with Lower Rate of Severe Chronic Gvhd

The ongoing COVID-19 pandemic continues to raise challenges for safe administration of allogeneic hematopoietic stem cell transplantation (allo-HSCT). From March to August 2020, unrelated donor (URD) peripheral blood stem cell (PBSC) products were shipped to central national hubs and cryopreserved either at the site of collection or infusion, a shift from the traditional practice of infusing fresh stem cells. The National Marrow Donor Program (NMDP) instituted this mandate due to uncertainty around international transportation of stem cells as well as a fail-safe to prevent interruptions to a planned transplant if a donor contracted COVID-19 after the recipient started conditioning chemotherapy. We previously published our single institution experience demonstrating equivalent short-term clinical outcomes (overall survival [OS], progression free survival [PFS], relapse, and non-relapse mortality [NRM]) between adult recipients of fresh vs cryopreserved allogeneic stem cells (median follow up time 16 months [fresh] vs 8 months [cryopreserved]) (PMID: 34581754). We also demonstrated lower T-cell chimerism at day 30 and 100 after receipt of cryopreserved grafts. There is a paucity of data evaluating longer term outcomes of patients receiving cryopreserved stem cells compared to fresh. Currently there is variability among donation and transplant centers around the practice of cryopreservation prior to allo-HSCT. With ongoing surges of COVID-19 and evolution of new variants, the risk of donors or recipients contracting COVID-19 leading to delays or disruptions in planned allo-HSCT remains high. In January 2022 with the rise of the Omicron variant of COVID-19, the NMDP reinstated the cryopreservation recommendation. Anecdotal reports indicate multiple recent instances of a planned URD testing positive for COVID-19 after conditioning chemotherapy had started but before stem cell harvest, raising the potential for severe deleterious outcomes in the intended transplant recipient. Given the unremitting COVID-19 surges three years into the pandemic and continued uncertainty around longer-term survival and relapse rates of allo-HSCT using cryopreserved stem cells, we reanalyzed our prior cohort and added 116 additional patients (40 cryopreserved, 76 fresh) with at least 1-year follow up for a total of 141 and 279 patients receiving cryopreserved versus fresh (respectively) URD PBSCs between January 1, 2019, and July 31, 2021. The cohorts had similar baseline characteristics including donor/recipient age/sex, disease, and conditioning regimen/intensity. Patients receiving cryopreserved cells were more likely to receive post-transplant cyclophosphamide as part of the graft versus host disease (GVHD) prophylaxis regimen (24% vs 15%, p=0.015). Median follow-up time among survivors in this cohort was 22 months (range, 4-41 months). Two-year OS was not different in patients receiving fresh versus cryopreserved stem cells (63% vs 63%, p=0.73) (Figure 1A). Two-year PFS was also similar (57% for fresh, 52% for cryopreserved, p=0.27) (Figure 1A). Relapse (36% vs 30%, p=0.17) and NRM (12% vs 13%, p=0.79) at two years were comparable between patients receiving fresh versus cryopreserved stem cells (Figure 1B). In total, 8 patients died of COVID-19 in this cohort (4 fresh, 3 cryopreserved). Cumulative incidence of moderate/severe chronic GVHD (cGVHD) was higher in patients receiving fresh stem cells versus cryopreserved (24% vs 9%, p=0.0003). Whereas cryopreservation was associated with lower T-cell chimerism early after transplant, by 1-year post-transplant, T-cell chimerism was not different (2% vs 5% of fresh vs cryopreserved patients with T-cell chimerism <75% at 1 year, p=0.14). However, Day 30 T-cell chimerism <75% was associated with a reduction in OS and PFS regardless of cryopreservation of stem cells (data not shown). As the COVID-19 pandemic continues with frequent surges in case numbers and rapid viral evolution, the risk for interruptions in life-saving allo-HSCT therapies remains high. Our data show that allo-HSCT with cryopreserved URD PBSCs results in similar OS, PFS, relapse rates, and NRM at 2 years post-transplantation. We found that cryopreservation is associated with lower 1-year cumulative incidence of moderate/severe cGVHD without compromise in OS. While this is an intriguing finding, larger multicenter analyses are needed to confirm these observations. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

The Sysmex XN series hematopoietic progenitor cell (XN-HPC) as a predictive marker of stem cell enumeration and products: a systemic review and meta-analysis

ABSTRACT Objectives: Sysmex® XN series hematopoietic progenitor cell (XN-HPC) is a sensitive, fast, and economic analytical method for predicting the yields of peripheral blood stem cell enumeration and products, and does not require a sophisticated or expensive workflow. However, various studies have shown that the characteristics of its diagnostic performance were non-uniform. Methods: We performed a systematic inquiry using PubMed, Embase, and Cochrane Library, to comprehensively search for studies published before November 21, 2021. The pooled specificity (SPE), sensitivity (SEN), negative likelihood ratio (NLR), positive likelihood ratio (PLR), diagnostic odds ratio (DOR) and receiver operating characteristic (ROC) curves were summarized to appraise the diagnostic merit of XN-HPC. A forest plot was used to research the sensitivities and specificities of XN-HPC performance. Subgroup analysis was performed to investigate heterogeneity where of importance. Results: Our research included four studies that assessed the diagnostic performance of XN-HPC in hematopoietic progenitor cell collection. The pooled accuracy was 95.4% (95% CI, 94.3–96.3), SPE was 0.81 (95% CI, 0.71–0.88), SEN was 0.95 (95% CI, 0.75-0.99), NLR was 0.06 (95% CI, 0.01–0.37), PLR was 5.0 (95% CI, 3.0–8.5), DOR was 78 (95% CI, 9–707) and the summary of the area under the ROC was 0.90 (95% CI, 0.87–0.92). Forest plot of sensitivities and specificities from XN-HPC test accuracy studies indicated the existence of high heterogeneity. We deduced that the patients were the source of heterogeneity via subgroup analysis. Conclusions: XN-HPC is an excellent diagnostic marker for quantitative detection of peripheral blood hematopoietic progenitor cells.

CT-098 Impact of T-Cell Dose on Outcome of T Cell–Replete HLA-Mismatched Allogeneic Peripheral Blood Stem Cell Transplantation

The outcome of allogeneic hematopoietic cell transplantation (HCST) relies on both disease-related factors and transplant-related factors including the conditioning regimen and immunotherapy exploiting the graft-versus-tumor (GVT) effect. CD3+ T cells are the main player in the GVT process, but an increased dose of these cells results in an increased risk of acute graft-versus-host disease (GVHD). We aimed to study whether the T-cell dose of allogeneic peripheral blood stem cell (PBSC) products influences transplantation outcomes in our patient population. This is a retrospective chart review study including patients over 18 years of age, diagnosed with AML, ALL, or MDS, who underwent PBSC mismatched allogeneic transplant, including haploidentical, one-antigen mismatched related, or 2-alleles mismatched related transplants at the King Hussein Cancer Center's bone marrow transplant program between January 2010 and December 2020. We calculated the median CD3 cell dose and divided all patients into 2 groups (Low and High dose groups) and then measured the cumulative incidence of acute GVHD, chronic GVHD, and 1- and 2-year overall survival (OS). Thirty-five patients were stratified according to the median CD3+ cell dose into the Low CD3 group, which included 18 (51%) patients with a mean dose of 13.7×107/kg (range: 2.8-19.7), and the High CD3 group, which included 17 (49%) patients with a mean dose of 29.7×107/kg (range: 19.8-93.1) (P-value: 0.000). The cumulative incidence of acute GVHD was 60% (n=12) in the Low CD3 group and 40% (n=8) in the High CD3 group (P-value: 0.24). The cumulative incidence of chronic GVHD was 64% (n=9) in the Low CD3 group and 35% (n=5) in the High CD3 group (P-value: 0.26). The overall survival for the cohort (n=35) at 12 months was 60.9% and reached 49.6% at 24 months. The 12-month OS for the Low and High CD3 groups was 66.7% and 52.9%, respectively. The 24-month OS for the Low and High CD3 groups was 66.7% and 33.1%, respectively (P-value: 0.084). Although the study showed a trend toward better OS in the Low CD3+ dose group, the difference was not statistically significant.

410 - Hematopoietic Stem/Progenitor Cells and Engineering: WASHING OF ABO INCOMPATIBLE ALLOGENEIC PERIPHERAL BLOOD STEM CELL PRODUCTS IS ASSOCIATED WITH LESS INFUSION REACTIONS BUT SIMILAR TRANSFUSION BURDEN AND TRANSPLANT OUTCOMES

410 - Hematopoietic Stem/Progenitor Cells and Engineering: WASHING OF ABO INCOMPATIBLE ALLOGENEIC PERIPHERAL BLOOD STEM CELL PRODUCTS IS ASSOCIATED WITH LESS INFUSION REACTIONS BUT SIMILAR TRANSFUSION BURDEN AND TRANSPLANT OUTCOMES