Safety and efficacy of healthy volunteer stem cell mobilization with filgrastim G-CSF and mobilized stem cell apheresis: results of a prospective longitudinal 5-year follow-up study

Long-term follow-up of cancer and catastrophic diseases in hematopoietic stem cell donors: a comprehensive matched cohort study

Hematopoietic stem cell (HSC) transplantation, using either bone marrow (BM) or peripheral blood stem cells (PBSC), is a well-established therapy for various hematologic and non-hematologic diseases. However, the long-term health outcomes after HSC donation remain a major concern for several potential donors. Thus, we aimed to conduct a matched cohort study of 5003 unrelated donors (1099 BM and 3904 PBSC) and randomly selected 50,030 matched controls based on age, sex, and resident area from the donor registry between 1998 and 2018. The medical insurance claims of all the participants were retrieved from the Taiwan National Health and Welfare Data Science Center after de-identification. Our findings revealed no differences in the incidence of cancer, death, and catastrophic diseases between HSC donors and matched healthy participants during long-term follow-up. Kaplan-Meier curves depicting the cumulative incidence of cancer and overall mortality throughout the follow-up period also demonstrated similar outcomes between donors and non-donors. In conclusion, our results indicate that HSC donation, whether through BM or PBSC, is safe and not associated with an increased risk of cancer, death, or catastrophic diseases. These findings provide valuable information for counseling potential HSC donors and for long-term management of HSC donor health.

A defined serum-free culture system for human long-term haematopoietic stem cells

Long-term repopulating haematopoietic stem cells (LT-HSCs) have the ability to reconstitute the entire haematopoietic system following transplantation permanently. Despite great achievements in HSC transplantation, the limited transplantable HSC number, especially LT-HSCs, remains critical for successful transplantation and broader applications. In this study, we established a defined serum-free culture system for in vitro expansion of LT-HSCs. This culture system (E1) expanded LT-HSCs from umbilical cord blood, human mobilization peripheral blood and bone marrow. These E1-expanded HSCs reconstituted the haematopoietic and immune systems in primary and secondary transplanted mice in a short time. Better haematopoietic reconstitution was observed in secondary xenografted mice. Moreover, we obtained the comprehensive expression profile and cellular components of LT-HSCs from umbilical cord blood. Our study provides a valuable tool for LT-HSC research and may improve clinical applications of HSCs.

Management of the Sickle Cell Trait: An Opinion by Expert Panel Members

The number of individuals with the sickle cell trait exceeds 300 million worldwide, making sickle cell disease one of the most common monogenetic diseases globally. Because of the high frequency of sickle cell disease, reproductive counseling is of crucial importance. In addition, unlike other carrier states, Sickle Cell Trait (SCT) seems to be a risk factor for several clinical complications, such as extreme exertional injury, chronic kidney disease, and complications during pregnancy and surgery. This expert panel believes that increasing knowledge about these clinical manifestations and their prevention and management can be a useful tool for all healthcare providers involved in this issue.

Hematopoietic stem cell mobilization

Hematopoietic stem cell (HSC) transplantation has been used to treat hematopoietic diseases for over 50 years. HSCs can be isolated from bone marrow (BM), umbilical cord blood, or peripheral blood. Because of lower costs, shorter hospitalization, and faster engraftment, peripheral blood has become the predominant source of HSCs for transplantation. The major factors determining the rate of successful HSC transplantation include the degree of human leukocyte antigen matching between the donor and recipient and the number of HSCs for transplantation. Administration of granulocyte colony-stimulating factor (G-CSF) alone or combined with plerixafor (AMD3100) are clinical used methods to promote HSC mobilization from BM to the peripheral blood for HSC transplantations. However, a significant portion of healthy donors or patients may be poor mobilizers of G-CSF, resulting in an insufficient number of HSCs for the transplantation and necessitating alternative strategies to increase the apheresis yield. The detailed mechanisms underlying G-CSF-mediated HSC mobilization remain to be elucidated. This review summarizes the current research on deciphering the mechanism of HSC mobilization.

Mobilization-based chemotherapy-free engraftment of gene-edited human hematopoietic stem cells

Hematopoietic stem/progenitor cell gene therapy (HSPC-GT) is proving successful to treat several genetic diseases. HSPCs are mobilized, harvested, genetically corrected ex vivo, and infused, after the administration of toxic myeloablative conditioning to deplete the bone marrow (BM) for the modified cells. We show that mobilizers create an opportunity for seamless engraftment of exogenous cells, which effectively outcompete those mobilized, to repopulate the depleted BM. The competitive advantage results from the rescue during ex vivo culture of a detrimental impact of mobilization on HSPCs and can be further enhanced by the transient overexpression of engraftment effectors exploiting optimized mRNA-based delivery. We show the therapeutic efficacy in a mouse model of hyper IgM syndrome and further developed it in human hematochimeric mice, showing its applicability and versatility when coupled with gene transfer and editing strategies. Overall, our findings provide a potentially valuable strategy paving the way to broader and safer use of HSPC-GT.

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HSPC mobilizers create an opportunity to engraft exogenous cells in depleted niches

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Ex vivo culture endows HSPCs with migration advantage by rescuing CXCR4 expression

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Cultured HSPCs outcompete mobilized HSPCs for engraftment in depleted BM niches

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Transient engraftment enhancers coupled with gene editing confer a competitive advantage

Superior physical and mental health of healthy volunteers before and five years after mobilized stem cell donation

Background

Safety, tolerability and efficacy of granulocyte colony-stimulating factor (G-CSF) for mobilization of hematopoietic stem and progenitor cells (HSPCs) from healthy donors have been conclusively demonstrated. This explicitly includes, albeit for smaller cohorts and shorter observation periods, biosimilar G-CSFs. HSPC donation is non-remunerated, its sole reward being “warm glow”, hence harm to donors must be avoided with maximal certitude. To ascertain, therefore, long-term physical and mental health effects of HSPC donation, a cohort of G-CSF mobilized donors was followed longitudinally.

Methods

We enrolled 245 healthy volunteers in this bi-centric long-term surveillance study. 244 healthy volunteers began mobilization with twice-daily Sandoz biosimilar filgrastim and 242 underwent apheresis after G-CSF mobilization. Physical and mental health were followed up over a period of 5-years using the validated SF-12 health questionnaire.

Results

Baseline physical and mental health of HSPC donors was markedly better than in a healthy reference population matched for ethnicity, sex and age. Physical, but not mental health was sharply diminished at the time of apheresis, likely due to side effects of biosimilar G-CSF, however had returned to pre-apheresis values by the next follow-up appointment after 6 months. Physical and mental health slightly deteriorated over time with kinetics reflecting the known effects of aging. Hence, superior physical and mental health compared to the general healthy non-donor population was maintained over time.

Conclusions

HSPC donors are of better overall physical and mental health than the average healthy non-donor. Superior well-being is maintained over time, supporting the favorable risk–benefit assessment of volunteer HSPC donation.

Trial registration National Clinical Trial NCT01766934

Cancer incidence in healthy Swedish peripheral blood stem cell donors

Granulocyte colony-stimulating factor (G-CSF) has been used for over 20 years to obtain peripheral blood stem cells from healthy donors for allogeneic stem cell transplantation. Concerns have been raised about a potentially increased cancer incidence in donors after donation, especially regarding haematological malignancies. In a prospective Swedish national cohort study, we studied the cancer incidence after donation in 1082 Swedish peripheral blood stem cell donors, donating between 1998 and 2014. The primary objective was to evaluate if the cancer incidence increased for donors treated with G-CSF. With a median follow-up time of 9.8 years, the incidence of haematological malignancies was 0.85 cases per 1000 person-years, and did not significantly differ from the incidence in age-, sex- and residence-matched population controls (hazard ratio 1.70, 95% confidence interval (CI) 0.79-3.64, p value 0.17), bone marrow donors or non-donating siblings. The total cancer incidence for peripheral blood stem cell donors was 6.0 cases per 1000 person-years, equal to the incidence in matched population controls (hazard ratio 1.03, 95% CI 0.78-1.36, p value 0.85), bone marrow donors or non-donating siblings. In this study of healthy peripheral blood stem cell donors, the cancer incidence was not increased after treatment with G-CSF.

Granulocyte Colony-Stimulating Factor Effectively Mobilizes TCR γδ and NK Cells Providing an Allograft Potentially Enhanced for the Graft-Versus-Leukemia Effect for Allogeneic Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potential cure for patients with hematological malignancies but substantial risks of recurrence of the malignant disease remain. TCR γδ and NK cells are perceived as potent innate effector cells in HSCT and have been associated with post-transplant protection from relapse in clinical studies. Immunocompetent cells from the donor are crucial for patient outcomes and peripheral blood stem cells (PBSC) are being increasingly applied as graft source. G-CSF is the preferential mobilizing agent in healthy donors for PBSC grafts, yet effects of G-CSF on TCR γδ and NK cells are scarcely uncovered and could influence the graft composition and potency of these cells. Therefore, we analyzed T and NK cell subsets and activation markers in peripheral blood samples of 49 donors before and after G-CSF mobilization and—for a subset of donors—also in the corresponding graft samples using multicolor flowcytometry with staining for CD3, CD4, CD8, TCRαβ, TCRγδ, Vδ1, Vδ2, HLA-DR, CD45RA, CD197, CD45RO, HLA-DR, CD16, CD56, and CD314. We found that TCR γδ cells were mobilized and harvested with an efficiency corresponding that of TCR αβ cells. For TCR γδ as well as for TCR αβ cells, G-CSF preferentially mobilized naïve and terminally differentiated effector (TEMRA) cells over memory cells. In the TCR γδ cell compartment, G-CSF preferentially mobilized cells of the nonVδ2 types and increased the fraction of HLA-DR positive TCR γδ cells. For NK cells, mobilization by G-CSF was increased compared to that of T cells, yet NK cells appeared to be less efficiently harvested than T cells. In the NK cell compartment, G-CSF-stimulation preserved the proportion of CD56dim NK effector cells which have been associated with relapse protection. The expression of the activating receptor NKG2D implied in anti-leukemic responses, was significantly increased in both CD56dim and CD56bright NK cells after G-CSF stimulation. These results indicate differentiated mobilization and altering properties of G-CSF which could improve the effects of donor TCR γδ and NK cells in the processes of graft-versus-leukemia for relapse prevention after HSCT.

Implications of hematopoietic stem cells heterogeneity for gene therapies

Hematopoietic stem cell transplantation (HSCT) is the therapeutic concept to cure the blood/immune system of patients suffering from malignancies, immunodeficiencies, red blood cell disorders, and inherited bone marrow failure syndromes. Yet, allogeneic HSCT bear considerable risks for the patient such as non-engraftment, or graft-versus host disease. Transplanting gene modified autologous HSCs is a promising approach not only for inherited blood/immune cell diseases, but also for the acquired immunodeficiency syndrome. However, there is emerging evidence for substantial heterogeneity of HSCs in situ as well as ex vivo that is also observed after HSCT. Thus, HSC gene modification concepts are suggested to consider that different blood disorders affect specific hematopoietic cell types. We will discuss the relevance of HSC heterogeneity for the development and manufacture of gene therapies and in exemplary diseases with a specific emphasis on the key target HSC types myeloid-biased, lymphoid-biased, and balanced HSCs.

Introduction of principles of blood management to healthy donor bone marrow harvesting

BACKGROUND AND OBJECTIVES

Patient blood (more accurately: haemoglobin, Hb) management (PBM) aims to optimize endogenous Hb production and to minimize iatrogenic Hb loss while maintaining patient safety and optimal effectiveness of medical interventions. PBM was adopted as policy for patients by the World Health Organization (WHO), and, all the more, should be applied to healthy donors.

MATERIALS AND METHODS

Observational data from 489 bone marrow (BM) donors were retrospectively analysed, and principles of patient blood management were applied to healthy volunteer BM donations.

RESULTS AND CONCLUSION

We managed to render BM aspiration safe for donors, notably completely avoiding the collection of autologous blood units and blood transfusions through iron management, establishment and curation of high-yield aspiration technique, limitation of collection volume to 1·5% of donor body weight and development of volume prediction algorithms for the requested cell dose.

Effects of Granulocyte Colony-Stimulating Factor on Proliferation and Apoptosis of B Cells in Bone Marrow of Healthy Donors

BACKGROUND AND OBJECTIVE

The aim of this study was to investigate the effects of granulocyte colony-stimulating factor (G-CSF) on the proliferation and apoptosis of bone marrow (BM) B cells from healthy donors and its mechanism.

MATERIALS AND METHODS

The proliferation ability and apoptosis of BM cells from healthy donors before and after in vivo G-CSF application were determined by multiparameter flow cytometry. The gene expression of B cells was detected by RNA-Seq. In vitro experiments were performed to investigate the effects of G-CSF on the proliferation and apoptosis of BM B cells through which gene.

RESULTS

Treating healthy donors with G-CSF significantly decreased proliferation and increased apoptosis of BM B cells. The proliferation of CD19⁺CD27^- B cell subgroup and CD19⁺CD24^hiCD38^hi B cell subset were also decreased. G-CSF also significantly altered proapoptotic genes, cell cycle arrest genes, and DNA replication and cell cycle genes, especially significantly increased SOCS1 expression of BM B cells. In vitro experiments showed that SOCS1 overexpression did not affect B cell proliferation ability and apoptosis.

CONCLUSIONS

Our results suggest that extensive effects of G-CSF on BM B cells, such as inhibiting proliferation, inducing apoptosis, and altering a series of gene expression.

Mobilized peripheral blood: an updated perspective

Enforced egress of hematopoietic stem cells (HSCs) out of the bone marrow (BM) into the peripheral circulation, termed mobilization, has come a long way since its discovery over four decades ago. Mobilization research continues to be driven by the need to optimize the regimen currently available in the clinic with regard to pharmacokinetic and pharmacodynamic profile, costs, and donor convenience. In this review, we describe the most recent findings in the field and how we anticipate them to affect the development of mobilization strategies in the future. Furthermore, the significance of mobilization beyond HSC collection, i.e. for chemosensitization, conditioning, and gene therapy as well as a means to study the interactions between HSCs and their BM microenvironment, is reviewed. Open questions, controversies, and the potential impact of recent technical progress on mobilization research are also highlighted.

Identification and characterization of permissive cells to dengue virus infection in human hematopoietic stem and progenitor cells

BACKGROUND

Dengue virus (DENV) is a significant threat to public health in tropical and subtropical regions, where the frequency of human migration is increasing. Transmission of DENV from donors to recipients after hematopoietic stem cell transplantation has been steadily described. However, the underlying mechanisms remain unclear.

STUDY DESIGN AND METHODS

Freshly isolated bone marrow (BM) was subjected to DENV infection, followed by multicolor fluorescence-activated cell sorting (FACS) analysis. Virus in supernatants was collected and analyzed by plaque assay.

RESULTS

DENV-1 to DENV-4 could effectively infect freshly obtained BM and produced infectious virus. DENV infection did not change the quantitative population of hematopoietic stem and progenitor cells (HSPCs), megakaryocytic progenitor cells (MkPs) and megakaryocytes. Additionally, DENV antigen, nonstructural protein 1, was enriched in HSPCs and MkPs of DENV infected marrow cells. CD34+, CD133+, or CD61+ cells sorted out from BM were not only the major contributing targets facilitating the DENV infection directly but also facilitated the spread of DENV into other cells when cocultured.

CONCLUSION

Results suggest that DENV can efficiently infect HSPCs, which might jeopardize the recipients if DENV-infected cells were subsequently used. We therefore raise the need for DENV screening for both the donors and recipients of hematopoietic stem cell transplantation, especially for donors exposed to endemic areas, to mitigate DENV infection in immunocompromised recipients.

Peripheral Blood Stem Cell Mobilization in Healthy Donors by Granulocyte Colony-Stimulating Factor Causes Preferential Mobilization of Lymphocyte Subsets

Background

Allogeneic hematopoietic stem cell transplantation is associated with a high risk of immune-mediated post-transplant complications. Graft depletion of immunocompetent cell subsets is regarded as a possible strategy to reduce this risk without reducing antileukemic immune reactivity.

Study design and methods

We investigated the effect of hematopoietic stem cell mobilization with granulocyte colony-stimulating factor (G-CSF) on peripheral blood and stem cell graft levels of various T, B, and NK cell subsets in healthy donors. The results from flow cytometric cell quantification were examined by bioinformatics analyses.

Results

The G-CSF-induced mobilization of lymphocytes was a non-random process with preferential mobilization of naïve CD4⁺ and CD8⁺ T cells together with T cell receptor αβ⁺ T cells, naïve T regulatory cells, type 1 T regulatory cells, mature and memory B cells, and cytokine-producing NK cells. Analysis of circulating lymphoid cell capacity to release various cytokines (IFNγ, IL10, TGFβ, IL4, IL9, IL17, and IL22) showed preferential mobilization of IL10 releasing CD4⁺ T cells and CD3^-19^- cells. During G-CSF treatment, the healthy donors formed two subsets with generally strong and weaker mobilization of immunocompetent cells, respectively; hence the donors differed in their G-CSF responsiveness with regard to mobilization of immunocompetent cells. The different responsiveness was not reflected in the graft levels of various immunocompetent cell subsets. Furthermore, differences in donor G-CSF responsiveness were associated with time until platelet engraftment. Finally, strong G-CSF-induced mobilization of various T cell subsets seemed to increase the risk of recipient acute graft versus host disease, and this was independent of the graft T cell levels.

Conclusion

Healthy donors differ in their G-CSF responsiveness and preferential mobilization of immunocompetent cells. This difference seems to influence post-transplant recipient outcomes.

Medical and ethical considerations on hematopoietic stem cells mobilization for healthy donors

Hematopoietic stem cell transplantation is a common procedure potentially beneficial to many individuals with cancer, hematological, or inherited disorders, and has highlighted the need of related or unrelated donors to perform allograft. Donation of hematopoietic stem cells, either through bone marrow harvest or peripheral blood stem cell collection, is well-established and widespread. Over the past two decades, the peripheral blood stem cell collection by aphaeresis has become the main source of hematopoietic stem cells for transplantation, due to faster engraftment and practicability and lower risk of relapse for high-risk patients. For peripheral blood stem cell donation, donors require mobilization of hematopoietic stem cells from bone marrow into the blood stream. This is performed by growth factors injections. This article is a review of reported applications of growth factors (original granulocyte colony stimulating factor and its biosimilars), for healthy donors' peripheral blood stem cell mobilization, in terms of toxicity, side effects, efficacy and follow-up. There is still an ethical dilemma for clinicians involved in allograft, because they expose healthy donors to drugs. It is important to dispel some of the critical concerns regarding their use in healthy volunteers, particularly because they receive no personal therapeutic benefit from this procedure.

What is the role of biosimilar G-CSF agents in hematopoietic stem cell mobilization at present?

Mobilization of hematopoietic stem cells, which has largely replaced bone marrow harvesting as a source of hematopoietic stem cells, using recombinant agents such as filgrastim or lenograstim has become a standard procedure in both patients and healthy donors prior to peripheral blood stem cell collection for autologous and allogeneic stem cell transplantation. Published literature data suggest that mobilization with recombinant granulocyte-colony stimulating factor (G-CSF) is safe and mobilization outcomes are satisfactory. In recent years, besides G-CSF originators, biosimilar G-CSF agents have been approved by the regulatory agencies for the same indications. Current data showed that by using the biosimilar G-CSF, similar results regarding safety and efficacy of hematopoietic stem cell mobilization may be achieved compared to the originator G-CSF. Although the issues such as the similarity to a licenced biological medicine, differences in manufacturing processes, the potential to cause immunogenicity, extrapolation and interchangeability of these biosimilar products are still being discussed by the scientific area, however, more experience with these agents now exists in approved endications and there seems to be no reason to expect significant differences between biosimilar G-CSF and originator G-CSF regarding their efficacy and safety in both patients and healthy donors. Also, the significant cost savings of biosimilars in real life setting may enhance the use of these agents in the future. Nonetheless, the collection of long-term follow-up data is mandatory for both patients and healthy donors, and multicentre randomized clinical trials that directly compare biosimilar G-CSF with the originator G-CSF are needed in order to allow the transplant community to make informed decisions regarding the choice of G-CSF.

Short-term side effects and attitudes towards second donation: A comparison of related and unrelated haematopoietic stem cell donors

The Nordic Register of Haematopoietic Stem Cell Donors (NRHSD) has registered related and unrelated donors from 10 transplant centres in Sweden, Norway, Finland and Denmark since 1998. We present a prospective, observational study of 1,957 donors, focusing mainly on the differences between related and unrelated donors. Related donors are reported to have more comorbidities, but similar side effects compared with unrelated donors. Side effects after BM or PBSC donation are generally of short duration and in this study no deaths, myocardial infarctions, splenic ruptures, or thromboembolic events are reported. Interestingly, related donors express more hesitancy towards donating again when asked 1 month after donation.

Mobilization of hematopoietic stem cells with the novel CXCR4 antagonist POL6326 (balixafortide) in healthy volunteers-results of a dose escalation trial

BACKGROUND

Certain disadvantages of the standard hematopoietic stem and progenitor cell (HSPC) mobilizing agent G-CSF fuel the quest for alternatives. We herein report results of a Phase I dose escalation trial comparing mobilization with a peptidic CXCR4 antagonist POL6326 (balixafortide) vs. G-CSF.

METHODS

Healthy male volunteer donors with a documented average mobilization response to G-CSF received, following ≥6 weeks wash-out, a 1-2 h infusion of 500-2500 µg/kg of balixafortide. Safety, tolerability, pharmacokinetics and pharmacodynamics were assessed.

RESULTS

Balixafortide was well tolerated and rated favorably over G-CSF by subjects. At all doses tested balixafortide mobilized HSPC. In the dose range between 1500 and 2500 µg/kg mobilization was similar, reaching 38.2 ± 2.8 CD34 + cells/µL (mean ± SEM). Balixafortide caused mixed leukocytosis in the mid-20 K/µL range. B-lymphocytosis was more pronounced, whereas neutrophilia and monocytosis were markedly less accentuated with balixafortide compared to G-CSF. At the 24 h time point, leukocytes had largely normalized.

CONCLUSIONS

Balixafortide is safe, well tolerated, and induces efficient mobilization of HSPCs in healthy male volunteers. Based on experience with current apheresis technology, the observed mobilization at doses ≥1500 µg/kg of balixafortide is predicted to yield in a single apheresis a standard dose of 4× 10E6 CD34+ cells/kg from most individuals donating for an approximately weight-matched recipient. Exploration of alternative dosing regimens may provide even higher mobilization responses. Trial Registration European Medicines Agency (EudraCT-Nr. 2011-003316-23) and clinicaltrials.gov (NCT01841476).

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.

In vivo engineering of mobilized stem cell grafts with the immunomodulatory drug FTY720 for allogeneic transplantation

The immunological attributes of stem cell grafts play an important role in the outcome of allogeneic stem cell transplants. Currently, ex vivo manipulation techniques such as bulk T-cell depletion or positive selection of CD34(+) cells are utilized to improve the immunological attributes of grafts and minimize the potential for graft-versus-host disease (GvHD). Here, we demonstrate a novel graft engineering technique, which utilizes the immunomodulatory drug FTY720 for in vivo depletion of naïve T (TN ) cells from donor G-CSF-mobilized grafts without ex vivo manipulation. We show that treatment of donor mice with FTY720 during mobilization depletes grafts of TN cells and prevents lethal GvHD following transplantation in a major mismatch setting. Importantly, both stem cells and NK cells are retained in the FTY720-treated grafts. FTY720 treatment does not negatively affect the engraftment potential of stem cells as demonstrated in our congenic transplants or the functionality of NK cells. In addition, potentially useful memory T cells may be retained in the graft. These findings suggest that FTY720 may be used to optimize the immunological attributes of G-CSF-mobilized grafts by removing potentially deleterious TN cells which can contribute to GvHD, and by retaining useful cells which can promote immunity in the recipient.

Recovery of Unrelated Donors of Peripheral Blood Stem Cells versus Recovery of Unrelated Donors of Bone Marrow: A Prespecified Analysis from the Phase III Blood and Marrow Transplant Clinical Trials Network Protocol 0201

We report a comparison of time to recovery, side effects, and change in blood counts from baseline to after donation from unrelated donors who participated in the Blood and Marrow Transplant Clinical Trials Network phase III randomized, multicenter trial (0201) in which donor-recipient pairs were randomized to either peripheral blood stem cell (PBSC) or bone marrow (BM) donation. Of the entire cohort, 262 donated PBSC and 264 donated BM; 372 (71%) donors were from domestic and 154 (29%) were from international centers (145 German and 9 Canadian). PBSC donors recovered in less time, with a median time to recovery of 1 week compared with 2.3 weeks for BM donors. The number of donors reporting full recovery was significantly greater for donors of PBSC than of BM at 1, 2, and 3 weeks and 3 months after donation. Multivariate analysis showed that PBSC donors were more likely to recover at any time after donation compared with BM donors (hazard ratio, 2.08; 95% confidence interval [CI], 1.73 to 2.50; P < .001). Other characteristics that significantly increased the likelihood of complete recovery were being an international donor and donation in more recent years. Donors of BM were more likely to report grades 2 to 4 skeletal pain, body symptoms, and fatigue at 1 week after donation. In logistic regression analysis of domestic donors only in which toxicities at peri-collection time points (day 5 filgrastim for PBSC donors and day 2 after collection of BM donors) could be analyzed, no variable was significantly associated with grades 2 to 4 skeletal pain, including product donated (BM versus PBSC; odds ratio, 1.13; 95% CI, .74 to 1.74; P = .556). Blood counts were affected by product donated, with greater mean change from baseline to after donation for white blood cells, neutrophils, mononuclear cells, and platelets in PBSC donors whereas BM donors experienced a greater mean change in hemoglobin. This analysis provided an enhanced understanding of donor events as product donated was independent of physician bias or donor preference.

Donors' health state the year after peripheral haematopoietic progenitor cell collection: A prospective follow-up study in related and unrelated donors compared to first-time platelet donors

Granulocyte colony-stimulating factor (G-CSF) mobilized peripheral haematopoietic progenitor cells collected by apheresis (HPC-A) are the most common source used for allogeneic hematopoietic stem cell transplantation (HSCT). Retrospective short and long-term donor follow-up studies show very low risks of serious complications and do not report compelling evidence of increased cancer occurrence. Some studies reported a prolonged period of leucopenia without an obvious association with infectious complications. However, beyond the first few weeks after the procedure a relationship between events is elusive. We therefore evaluated medical service utilization by prospectively recruited HPC-A donors and first-time platelet apheresis donors for comparison for 1 year after donation. Data were prospectively collected using questionnaires and by medical record review. A total of 215 HPC-A donors (111 unrelated donors and 104 related donors) and 96 first-time platelet donors consented to participation in the study. Follow-up was available for 202 (96%): questionnaires were returned by 74% and records from nonstudy contacts were available for 94% of donors. During the 1-year follow-up, 94 of the donors who returned questionnaires sought medical attention for diagnostic evaluation and/or treatment: 41% of HPC-A donors and 40% of platelet donors. Medical service utilization the first year after HPC-A donation is similar to that after first-time platelet donation. The occurrence of serious medical conditions in both related and unrelated HPC-A donors underscores the importance of participation in long-term follow-up in large cohorts. The findings in this relatively small cohort contribute to evidence on the safety of G-CSF mobilization and HPC-A. J. Clin. Apheresis 31:523-528, 2016. © 2015 Wiley Periodicals, Inc.

Impact of Charged Particle Exposure on Homologous DNA Double-Strand Break Repair in Human Blood-Derived Cells

Ionizing radiation generates DNA double-strand breaks (DSB) which, unless faithfully repaired, can generate chromosomal rearrangements in hematopoietic stem and/or progenitor cells (HSPC), potentially priming the cells towards a leukemic phenotype. Using an enhanced green fluorescent protein (EGFP)-based reporter system, we recently identified differences in the removal of enzyme-mediated DSB in human HSPC versus mature peripheral blood lymphocytes (PBL), particularly regarding homologous DSB repair (HR). Assessment of chromosomal breaks via premature chromosome condensation or γH2AX foci indicated similar efficiency and kinetics of radiation-induced DSB formation and rejoining in PBL and HSPC. Prolonged persistence of chromosomal breaks was observed for higher LET charged particles which are known to induce more complex DNA damage compared to X-rays. Consistent with HR deficiency in HSPC observed in our previous study, we noticed here pronounced focal accumulation of 53BP1 after X-ray and carbon ion exposure (intermediate LET) in HSPC versus PBL. For higher LET, 53BP1 foci kinetics was similarly delayed in PBL and HSPC suggesting similar failure to repair complex DNA damage. Data obtained with plasmid reporter systems revealed a dose- and LET-dependent HR increase after X-ray, carbon ion and higher LET exposure, particularly in HR-proficient immortalized and primary lymphocytes, confirming preferential use of conservative HR in PBL for intermediate LET damage repair. HR measured adjacent to the leukemia-associated MLL breakpoint cluster sequence in reporter lines revealed dose dependency of potentially leukemogenic rearrangements underscoring the risk of leukemia-induction by radiation treatment.

Spleen Size Is Significantly Influenced by Body Height and Sex: Establishment of Normal Values for Spleen Size at US with a Cohort of 1200 Healthy Individuals

PURPOSE

To define height- and sex-corrected normal values for spleen length and volume determined with ultrasonography (US).

MATERIALS AND METHODS

The authors performed a retrospective data review of stem cell donors who had provided written informed consent for stem cell donation and use of anonymized data and biologic materials for scientific and quality control purposes. Spleen length, spleen volume, and anthrophometric data were correlated in 1230 healthy volunteers to identify variables that affect spleen size. Multiple linear regression analysis was performed to weight effects of various variables on spleen size. Linear regression through the 95th percentile for men and women of different height cohorts generated the formula for the upper limit of normal for spleen length and volume. For validation, the upper limit of normal was calculated for each volunteer and compared with the observed value. Formulae to calculate the additional percentiles were similarly generated and validated. A cohort of 75 volunteers was analyzed twice to assess the stability of spleen length and volume over time.

RESULTS

Spleen length and volume were significantly and independently associated with sex (length: P < .001; volume: P = .012), body height (P < .001 for both), and weight (P < .001 for both), with men and taller and heavier individuals having longer and larger spleens. The spleen length of 20 of 324 women (6%) and 234 of 906 men (26%) exceeded the previously reported upper limit of normal of 12 cm. Repeat measurements indicated that spleen length (median difference, 0.10 cm; range, -1.8 to 1.7 cm) and volume (median difference, 3 cm(3); range, -106 to 142 cm(3)) were quite stable. A mobile application that performs these calculations is available for download.

CONCLUSION

The authors define height- and sex-corrected normal values for spleen length and volume for women with a body height of 155-179 cm and men with a body height of 165-199 cm and propose validated algorithms to gauge the percentile of an individual's spleen size.

Duchenne muscular dystrophy: current cell therapies

Duchenne muscular dystrophy is a genetically determined X-linked disease and the most common, progressive pediatric muscle disorder. For decades, research has been conducted to find an effective therapy. This review presents current therapeutic methods for Duchenne muscular dystrophy, based on scientific articles in English published mainly in the period 2000 to 2014. We used the PubMed database to identify and review the most important studies. An analysis of contemporary studies of stem cell therapy and the use of granulocyte colony-stimulating factor (G-CSF) in muscular dystrophy was performed.

Automated CD34+ cell isolation of peripheral blood stem cell apheresis product

BACKGROUND AIMS

Immunomagnetic enrichment of CD34+ hematopoietic "stem" cells (HSCs) using paramagnetic nanobead coupled CD34 antibody and immunomagnetic extraction with the CliniMACS plus system is the standard approach to generating T-cell-depleted stem cell grafts. Their clinical beneficence in selected indications is established. Even though CD34+ selected grafts are typically given in the context of a severely immunosuppressive conditioning with anti-thymocyte globulin or similar, the degree of T-cell depletion appears to affect clinical outcomes and thus in addition to CD34 cell recovery, the degree of T-cell depletion critically describes process quality. An automatic immunomagnetic cell processing system, CliniMACS Prodigy, including a protocol for fully automatic CD34+ cell selection from apheresis products, was recently developed. We performed a formal process validation to support submission of the protocol for CE release, a prerequisite for clinical use of Prodigy CD34+ products.

METHODS

Granulocyte-colony stimulating factor-mobilized healthy-donor apheresis products were subjected to CD34+ cell selection using Prodigy with clinical reagents and consumables and advanced beta versions of the CD34 selection software. Target and non-target cells were enumerated using sensitive flow cytometry platforms.

RESULTS

Nine successful clinical-scale CD34+ cell selections were performed. Beyond setup, no operator intervention was required. Prodigy recovered 74 ± 13% of target cells with a viability of 99.9 ± 0.05%. Per 5 × 10E6 CD34+ cells, which we consider a per-kilogram dose of HSCs, products contained 17 ± 3 × 10E3 T cells and 78 ± 22 × 10E3 B cells.

CONCLUSIONS

The process for CD34 selection with Prodigy is robust and labor-saving but not time-saving. Compared with clinical CD34+ selected products concurrently generated with the predecessor technology, product properties, importantly including CD34+ cell recovery and T-cell contents, were not significantly different. The automatic system is suitable for routine clinical application.

G-CSF-primed bone marrow as a source of stem cells for allografting: revisiting the concept

The source of hematopoietic stem cells (HSCs) for allogeneic transplantation has evolved over the last decades, from the sole use of unstimulated bone marrow (BM) to the use of G-CSF (filgrastim)-mobilized peripheral blood, G-CSF-primed BM (G-BM) and cord blood. G-CSF-mobilized PBSC has replaced BM as the most commonly used source of allogeneic stem cells. G-BM is a source of HSCs, with studies demonstrating the safety and feasibility of this strategy with the potential for reducing GvHD, while retaining the speed of engraftment. Although the G-BM had lost its use as the optimal source of stem cells, after the widespread use of haploidentical transplantation, their use has resurfaced in 2010. This source can still be used in today's world of transplantation in aplastic anemia and other benign diseases, as well as in children donors. This study intends to review the evidence for this approach and whether this approach still has merit in the ever-evolving field of allogenic HSC transplantation. The merit of G-BM is its ability to offer speed of engraftment with reduced GvHD.

Variant rs1801157 in the 3'UTR of SDF-1ß does not explain variability of healthy-donor G-CSF responsiveness

The genetics responsible for the inter-individually variable G-CSF responsiveness remain elusive. A single nucleotide polymorphism (SNP) in the 3’UTR of CXCL12, rs1801157, was implicated in X4-tropic HiV susceptibility and later, in two small studies, in G-CSR responsiveness in patients and donors. The position of the SNP in the 3’UTR together with in-silico predictions suggested differential binding of micro-RNA941 as an underlying mechanism. In a cohort of 515 healthy stem cell donors we attempted to reproduce the correlation of the CXCL12 3’UTR SNP and mobilization responses and tested the role of miR941 in this context. The SNP was distributed with the expected frequency. Mobilization efficiency for CD34+ cells in WT, heterozygous and homozygous SNP individuals was indistinguishable, even after controlling for gender. miR941 expression in non-hematopoietic bone marrow cells was undetectable and miR941 did not interact with the 3’ UTR of CXCL12. Proposed effects of the SNP rs1801157 on G-CSF responsiveness cannot be confirmed in a larger cohort.

Biosimilar granulocyte-colony-stimulating factor for healthy donor stem cell mobilization: need we be afraid?

Biosimilars are approved biologics with comparable quality, safety, and efficacy to a reference product. Unlike generics, which are chemically manufactured copies of small-molecule drugs with relatively simple chemical structures, the biosimilar designation is applied to drugs that are produced by living organisms, implying much more difficult to control manufacturing and purification procedures. To account for these complexities, the European Medicines Agency (EMA), the US Food and Drug Administration, the Australian Therapeutic Goods Administration, and other regulatory authorities have devised and implemented specific, markedly more demanding pathways for the evaluation and approval of biosimilars. To date, several biosimilars have been approved, including versions of somatropin, erythropoietin, and granulocyte-colony-stimulating factor (G-CSF), and several biosimilar monoclonal antibodies are currently in development. The reference G-CSF product (Neupogen, Amgen) has been used for many years for prevention and treatment of neutropenia and also for mobilization of peripheral blood stem cells (PBSCs). However, concerns have been raised about the safety and efficacy of biosimilar G-CSF during PBSC mobilization procedures, especially in healthy donors. This article reviews the available evidence on the use of biosimilar G-CSF in this setting. Aggregate clinical evidence supports the assessment by the EMA of biosimilar and originator G-CSF as highly biologically similar, with respect to desired and undesired effects.

A review of the genetic and long-term effects of G-CSF injections in healthy donors: a reassuring lack of evidence for the development of haematological malignancies

In 2007 the WMDA responded to the publication of two manuscripts suggesting a causal link between G-CSF and myeloid malignancies in healthy donors by convening an international symposium to examine this issue. At the time, registries reviewed the long-term follow-up of their healthy donors, which suggested no excess of leukaemia in PBSC donors compared with BM donors. Although the evidence for an increased risk of malignancy in healthy donors was felt to be weak, it could not be excluded. The WMDA, therefore, issued a statement, to be included in all donor consent forms, stating that it was unknown whether G-CSF increased or decreased the risk of later developing cancer. In 2012, with 5 years of additional donor follow-up and the results of several genetic studies now available, the clinical working group of the WMDA again reviewed the data. On the basis of an assessment of a continuing lack of evidence for an increased risk of malignancy in donors receiving G-CSF, the WMDA has re-issued a more reassuring statement. The revised statement was circulated to all WMDA member registries in late 2012 to replace the existing statement in consent forms, which now conclusively states that, 'Studies following large numbers of unrelated donors have shown that the risk of developing cancer within several years after the use of G-CSF is not increased compared with donors not receiving G-CSF'. Herein we review the evidence on which this statement is based.

Effective collection of peripheral blood stem cells in children weighing 20 kilogram or less in a single large-volume apheresis procedure

INTRODUCTION

Peripheral blood stem cell (PBSC) transplantation has become a routine procedure in pediatric oncology. A special group of PBSC donors are children weighing 20 kg or less. Limited vascular access and low blood volume puts them at a higher risk. Central line placement and a priming apheresis machine are recommended to avoid these complications.

PATIENTS AND METHODS

PBSC collections performed from July 2006 to May 2013 in children weighing less than 20 kg were included. All donors had a central venous catheter (CVC). An apheresis machine was primed with packet red blood cells.

RESULTS

Twenty-seven PBSC collections were performed in 22 children weighing 20 kg or less, 14 for allogeneic and 8 for autologous transplantation, in order to collect at least 2 × 10(6) CD34+ cells/kg. In the allogeneic group, median age and weight were 3 years (0.8-7) and 15.5 kg (8-20). In the autologous group, median age and weight were 3 years (2-7) and 15.35 kg (12.5-19.5). A single large-volume apheresis was sufficient to obtain the CD34+ cells needed in 78.5% and 75% of the allogeneic and autologous groups, respectively, with a median 11.84 × 10(6) and 5.79 × 10(6) CD34+ cells collected per kilogram of weight of the recipient. No serious complications related to the apheresis procedure or CVC placement occurred.

CONCLUSION

PBSC collection in a single large-volume apheresis for allogeneic and autologous transplants in children weighing 20 kg or less is a safe and effective procedure when based on standardized protocols.

The novel CXCR4 antagonist POL5551 mobilizes hematopoietic stem and progenitor cells with greater efficiency than Plerixafor

Mobilized blood has supplanted bone marrow (BM) as the primary source of hematopoietic stem cells for autologous and allogeneic stem cell transplantation. Pharmacologically enforced egress of hematopoietic stem cells from BM, or mobilization, has been achieved by directly or indirectly targeting the CXCL12/CXCR4 axis. Shortcomings of the standard mobilizing agent, granulocyte colony-stimulating factor (G-CSF), administered alone or in combination with the only approved CXCR4 antagonist, Plerixafor, continue to fuel the quest for new mobilizing agents. Using Protein Epitope Mimetics technology, a novel peptidic CXCR4 antagonist, POL5551, was developed. In vitro data presented herein indicate high affinity to and specificity for CXCR4. POL5551 exhibited rapid mobilization kinetics and unprecedented efficiency in C57BL/6 mice, exceeding that of Plerixafor and at higher doses also of G-CSF. POL5551-mobilized stem cells demonstrated adequate transplantation properties. In contrast to G-CSF, POL5551 did not induce major morphological changes in the BM of mice. Moreover, we provide evidence of direct POL5551 binding to hematopoietic stem and progenitor cells (HSPCs) in vivo, strengthening the hypothesis that CXCR4 antagonists mediate mobilization by direct targeting of HSPCs. In summary, POL5551 is a potent mobilizing agent for HSPCs in mice with promising therapeutic potential if these data can be corroborated in humans.

Bone marrow endothelial progenitors augment atherosclerotic plaque regression in a mouse model of plasma lipid lowering

The major event initiating atherosclerosis is hypercholesterolemia-induced disruption of vascular endothelium integrity. In settings of endothelial damage, endothelial progenitor cells (EPCs) are mobilized from bone marrow into circulation and home to sites of vascular injury where they aid endothelial regeneration. Given the beneficial effects of EPCs in vascular repair, we hypothesized that these cells play a pivotal role in atherosclerosis regression. We tested our hypothesis in the atherosclerosis-prone mouse model in which hypercholesterolemia, one of the main factors affecting EPC homeostasis, is reversible (Reversa mice). In these mice, normalization of plasma lipids decreased atherosclerotic burden; however, plaque regression was incomplete. To explore whether endothelial progenitors contribute to atherosclerosis regression, bone marrow EPCs from a transgenic strain expressing green fluorescent protein (GFP) under the control of endothelial cell-specific Tie2 promoter (Tie2-GFP(+)) were isolated. These cells were then adoptively transferred into atheroregressing Reversa recipients where they augmented plaque regression induced by reversal of hypercholesterolemia. Advanced plaque regression correlated with engraftment of Tie2-GFP(+) EPCs into endothelium and resulted in an increase in atheroprotective nitric oxide and improved vascular relaxation. Similarly augmented plaque regression was also detected in regressing Reversa mice treated with the stem cell mobilizer AMD3100 which also mobilizes EPCs to peripheral blood. We conclude that correction of hypercholesterolemia in Reversa mice leads to partial plaque regression that can be augmented by AMD3100 treatment or by adoptive transfer of EPCs. This suggests that direct cell therapy or indirect progenitor cell mobilization therapy may be used in combination with statins to treat atherosclerosis.

Predictors of the yield of mobilized peripheral blood CD34+ cells in HLA-matched sibling donor

We examined the donor factors that may affect the yield of peripheral blood stem cell (PBSC) mobilized from healthy donors. Pre-apheresis PB-CD34(+) cell count was the only factor that correlated with PBSC yield. Leukocyte count (LC) and monocyte count (MC) correlated with PB-CD34(+) cell. Male gender and PB-CD34(+) cell count of at least 87.1/μL and 69.8/μL on day-4 and -5 of G-CSF were associated with the ability to harvest at least 5×10(6)/kg CD34(+) cells after one apheresis. We concluded that gender and PB-CD34(+) cell count are important predictors of PBSC yield. LC and MC may serve as surrogate markers for estimating the PB-CD34(+) cell count.

Effect of filgrastim (recombinant human granulocyte colony stimulating factor) on IgE responses in human asthma: a case study

RATIONALE

The role of peripheral blood progenitor cell mobilization on Immunoglobulin E (IgE) responses has not been studied.

METHODS

Distributions of blood lymphocytes (CD4+, CD8+, CD8+CD60+, CD19+, CD23+, CD16/56+, CD25, CD45RA+, CD45RO+, CD34+), and levels of serum immunoglobulins (IgM, IgG, IgA, IgE) were studied in an allergic asthmatic serum IgE+ (181IU/mL) adult (m/45 y/o) donor undergoing routine stem cell mobilization protocol (American Society of Hematology) before (day-30), during (day 4), and after (1 wk post last dose) filgrastim (subcutaneous, 480 mcg, 2qd) treatment (flow cytometry, nephelometry, UniCAP Total IgE Fluoro enzyme immunoassay).

RESULTS

On day 4 of filgrastim treatment, numbers of CD8+CD60+T cells and CD23+ blood cells dramatically increased (98% and 240% respectively) compared with pre treatment. In contrast on day 4 of treatment, serum IgE levels decreased (>50%) compared with pre treatment. CD8+CD60+T cells and CD23+ blood cells and serum IgE levels approached pre-treatment levels at 1 week post treatment.

CONCLUSIONS

Filgrastim treatment transiently increases numbers of CD8+CD60+T and CD23+ expressing cells, which are known to regulate human IgE responses, while also transiently suppressing ongoing IgE responses. These results suggest that filgrastim affects IgE related responses, and may be useful in modulating allergic responses.

Bone marrow endothelial progenitors in atherosclerotic plaque resolution

Atherosclerosis is a major cause of morbidity and mortality in the United States. Persistently elevated circulating low-density lipoprotein, or hypercholesterolemia, and deposition of low-density lipoprotein in the vascular wall are the main inducers of atherosclerosis, which manifests itself as arterial lesions or plaques. Some plaques become thrombosis-prone and rupture, causing acute myocardial infarction or stroke. Lowering plasma cholesterol through the use of statins is the primary intervention against atherosclerosis. Treatment with statins slows progression of atherosclerosis but can only support limited plaque regression. Partially regressed plaques continue to pose a serious threat due to their remaining potential to rupture. Thus, new interventions inducing complete reversal of atherosclerosis are being sought. Implementation of new therapies will require clear understanding of the mechanisms driving plaque resolution. In this Views and Commentary, we highlight the role of bone marrow endothelial progenitors in atherosclerotic plaque regression and discuss how regenerative cell-based interventions could be used in combination with plasma lipid-lowering to induce plaque reversal in order to prevent and/or reduce adverse cardiovascular events.

Hematopoietic stem cell mobilization: updated conceptual renditions

Despite its specific clinical relevance, the field of hematopoietic stem cell mobilization has received broad attention, owing mainly to the belief that pharmacologic stem cell mobilization might provide clues as to how stem cells are retained in their natural environment, the bone marrow 'niche'. Inherent to this knowledge is also the desire to optimally engineer stem cells to interact with their target niche (such as after transplantation), or to lure malignant stem cells out of their protective niches (in order to kill them), and in general to decipher the niche's structural components and its organization. Whereas, with the exception of the recent addition of CXCR4 antagonists to the armamentarium for mobilization of patients refractory to granulocyte colony-stimulating factor alone, clinical stem cell mobilization has not changed significantly over the last decade or so, much effort has been made trying to explain the complex mechanism(s) by which hematopoietic stem and progenitor cells leave the marrow. This brief review will report some of the more recent advances about mobilization, with an attempt to reconcile some of the seemingly inconsistent data in mobilization and to interject some commonalities among different mobilization regimes.