Autologous Hematopoietic Progenitor Cell Research Articles

PS1220 EX‐VIVO HEMATOPOIETIC STEM CELL GENE THERAPY (GT) FOR MUCOPOLYSACCHARIDOSIS TYPE I HURLER (MPSIH): PRELIMINARY RESULTS FROM A PHASE I/II CLINICAL STUDY

Background:MPSIH is a lysosomal storage disease caused by α‐L‐iduronidase (IDUA) deficiency that is associated with progressive multisystem morbidity including neurodevelopmental deterioration and severe orthopedic manifestations, leading to death in early childhood. Current therapeutic strategies include enzyme replacement therapy and allogeneic hematopoietic stem cell transplantation (HSCT), which however show limitations in preventing neurodevelopmental and orthopedic complications. Transplantation of genetically‐engineered autologous hematopoietic stem and progenitor cells (HSPC) is an attractive treatment option for MPSIH thanks to the possibility to obtain supraphysiologic levels of the missing enzyme in the hematopoietic progeny, thus allowing for increased cross‐correction.Aims:We recently opened a phase I/II clinical trial (NCT03488394) in children affected by MPSIH aimed at evaluating safety, tolerability and efficacy of the transplantation of autologous, IDUA lentiviral (LV)‐transduced CD34+ cells in MPSIH patients undergoing myeloablative conditioning.Methods:The study foresees the enrollment of 6 patients who lack a non‐heterozygous HLA‐matched donor and display an IQ/DQ>70. Primary endpoints of safety include: overall survival, hematological engraftment and safety of drug product (DP) administration. Primary endpoint of efficacy is represented by IDUA activity in peripheral blood up to supraphysiologic levels at 1 year post‐gene therapy (GT). Treatment impact on nervous system, skeleton and other target organs is assessed by clinical and radiologic parameters, as well as by disease‐specific biomarkers.Results:By the submission deadline, two patients (24 and 14 months old) were treated and have a follow‐up of 7 and 1.5 months, respectively. Autologous HSPC were harvested after mobilization with G‐CSF and Plerixafor; the procedure was uneventful and resulted in cryopreserved DP of 24 and 14 million CD34+ cells/kg, respectively. Transduction efficiency in the drug products was above 80% using an optimized transduction protocol that preserved engraftment potential of ex vivo‐cultured HSPC in preclinical models. No adverse events related to DP infusion were recorded. Hematopoietic engraftment was fast in both patients; neutrophil engraftment occurred on day +17 and +22, respectively; platelet engraftment at day+15 with counts never falling below 30.000/ul in both patients. Importantly, both patients reached supraphysiologic levels of IDUA by day+14 that stabilized around 10 fold above the mean of the normal range, along with an in vivo vector copy number ranging from 2 to 4 in multiple hematopoietic lineages. At the 6 month follow‐up of patient 1, stable IDUA activity was detected in the cerebrospinal fluid, and urinary GAGs normalized. A third patient has been successfully mobilized resulting in a cryopreserved DP of 13 million CD34+ cells/kg and will be treated shortly. Other patients are currently under evaluation.Summary/Conclusion:Preliminary clinical results indicate that our optimized transduction protocol allows efficient HSPC transduction without compromising their engraftment potential. Treated patients showed rapid hematopoietic recovery, supraphysiologic IDUA levels in the peripheral blood and metabolic correction of the MPSI‐H enzyme defect in critical target tissues. Long term‐follow up and treatment of further patients are necessary to confirm that IDUA supraphysiologic levels result in improvement of neurological and orthopedic outcome as compared to allogeneic HSCT.

Bone marrow harvesting from paediatric patients undergoing haematopoietic stem cell gene therapy

Collection of an adequate amount of autologous haematopoietic stem progenitor cells (HSPC) is required for ex vivo manipulation and successful engraftment for certain inherited disorders. Fifty-seven paediatric patients (age 0.5–11.4 years) underwent a bone marrow harvest for the purpose of HSPC gene therapy (GT), including adenosine deaminase-severe combined immunodeficiency (ADA-SCID), Wiskott–Aldrich syndrome (WAS) and metachromatic leukodystrophy (MLD) patients. Total nucleated cells and the percentage and absolute counts of CD34+ cells were calculated at defined steps of the procedure (harvest, CD34+ cell purification, transduction with the gene transfer vector and infusion of the medicinal product). A minimum CD34+ cell dose for infusion was 2 × 106/kg, with an optimal target at 5–10 × 106/kg. Median volume of bone marrow harvested was 34.2 ml/kg (range 14.2–56.6). The number of CD34+ cells collected correlated inversely with weight and age in all patients and particularly in the MLD children group. All patients reached the minimum target dose for infusion: median dose of CD34+ cells/kg infused was 10.3 × 106/kg (3.7–25.9), with no difference among the three groups. Bone marrow harvest of volumes > 30 ml/kg in infants and children with ADA-SCID, WAS and MLD is well tolerated and allows obtaining an adequate dose of a medicinal product for HSPC-GT.

Editing the Sickle Cell Disease Mutation in Human Hematopoietic Stem Cells: Comparison of Endonucleases and Homologous Donor Templates.

Site-specific correction of a point mutation causing a monogenic disease in autologous hematopoietic stem and progenitor cells (HSPCs) can be used as a treatment of inherited disorders of the blood cells. Sickle cell disease (SCD) is an ideal model to investigate the potential use of gene editing to transvert a single point mutation at the β-globin locus (HBB). We compared the activity of zinc-finger nucleases (ZFNs) and CRISPR/Cas9 for editing, and homologous donor templates delivered as single-stranded oligodeoxynucleotides (ssODNs), adeno-associated virus serotype 6 (AAV6), integrase-deficient lentiviral vectors (IDLVs), and adenovirus 5/35 serotype (Ad5/35) to transvert the base pair responsible for SCD in HBB in primary human CD34+ HSPCs. We found that the ZFNs and Cas9 directed similar frequencies of nuclease activity. Invitro, AAV6 led to the highest frequencies of homology-directed repair (HDR), but levels of base pair transversions were significantly reduced when analyzing cells invivo in immunodeficient mouse xenografts, with similar frequencies achieved with either AAV6 or ssODNs. AAV6 also caused significant impairment of colony-forming progenitors and human cell engraftment. Gene correction in engrafting hematopoietic stem cells may be limited by the capacity of the cells to mediate HDR, suggesting additional manipulations may be needed for high-efficiency gene correction in HSPCs.

Loss-of-Function Mutations in HLA-Class I Alleles in Acquire Aplastic Anemia: Evidence for the Involvement of Limited Class I Alleles in the Auto-Antigen Presentation of Aplastic Anemia

[Background] Acquired aplastic anemia (AA) is a rare syndrome characterized by pancytopenia and bone marrow hypoplasia. The cytotoxic T lymphocyte (CTL) attack against autologous hematopoietic stem progenitor cells (HSPCs) is thought to be responsible for bone marrow failure in the majority of AA cases; however, little is known about the target antigens of the CTLs. HLA class I-allele lacking leukocytes (HLA-LL) due to copy-number neutral loss of heterozygosity in the short arm of chromosome 6 (6pLOH) or somatic loss-of-function mutations in HLA class I genes are detected in approximately 20% of patients with newly diagnosed AA, and the presence of HLA-LL represents compelling evidence to support that CTLs specific to HSPCs are involved in the development of AA. Our recent studies using single nucleotide polymorphism array (SNP-A) genotyping and droplet digital polymerase chain reaction (ddPCR) revealed that HLA-B*40:02 is the most frequently lost among all class I alleles that are lost as a result of 6pLOH (Zaimoku, et al. Blood 2017). Various somatic loss-of-function mutations in B*40:02 revealed by deep sequencing in the study substantiated the important role of HLA-B4002 in the autoantigen presentation of AA. However, in the other 6pLOH(+) AA patients who did not possess HLA-B4002, which accounted for 20% of the total AA cases involving patients possessing HLA-LL, the allele in the missing haplotype that was responsible for the autoantigen presentation was largely unknown because the lost fragment of chromosome 6p usually contained 2 or more HLA class I alleles. [Objectives/Methods] To identify class I alleles other than HLA-B*40:02 that are critically involved in the auto-antigen presentation of AA, we screened a total of 624 patients for the presence of HLA-LL using monoclonal antibodies specific to class I HLA alleles, SNP-A, and ddPCR, and performed targeted deep sequencing of HLA class I genes by using SeqCap EZ Choice pobes (Roche) and MiSeq sequencer (Illumina). The paired fractions, including granulocytes that lacked an HLA-A allele and granulocytes that retained the HLA-A allele, as well as CD3+ T cells, were sorted using monoclonal antibodies specific to HLA-A alleles with a BD FACSAria Fusion system (BD Biosciences), and were subjected to DNA extraction. All DNA samples of granulocytes and control cells (CD3+ T cells or buccal mucosa cells) were prepared for targeted deep sequencing. [Results] One hundred and fourteen patients were found to be positive for HLA-LL and 62 (54.4%) of the 114 HLA-LL(+) patients did not carry B*40:02 (severe, n=30; non-severe, n=32; male, n=38; female, n=24; median age, 62 [range, 6-93] years). Apart from B*40:02 (45.6%), A*02:06 (24.6%) was the second-most frequent HLA class I allele in the lost haplotype. The targeted deep sequencing of 20 patients with HLA-LL revealed 6pLOH alone in 11 patients, and somatic loss-of-function mutations plus 6pLOH in 9 patients; none of the patients were positive for somatic loss-of-function mutations alone. Of note, somatic loss-of-function mutations were found in only 5 alleles (A*02:06 in four, B*40:01 in two, B*40:03, A*31:01, and B*54:01 in one each) out of 27 different alleles contained in the lost haplotype. Among the 9 patients with somatic loss-of-function mutations, the median number of mutations per patient was 1 (range, 1-2); these included a missense mutation (n=1), frameshift deletions (n=3) and nonsense mutations (n=7) (Figure). Four patients had a breakpoint of 6pLOH in between the HLA-A and C loci; their lost alleles were A*02:06 (n=2) and A*31:01 (n=2), and the occurrence of 6pLOH in the four patients was therefore attributed to the two HLA-A alleles. Sixty-six percent of the HLA-LL(+) B*40:02(-) patients had at least one of the five alleles in the lost haplotypes. The frequencies of each “high risk” allele found in patients possessing HLA-LL are summarized in Table. [Conclusions] In addition to B*40:02, five class I alleles including HLA-A*02:06, A*31:01, B*54:01, B*40:03 and B*40:01 are thought to play an essential role in the auto-antigen presentation by the HSPCs of Japanese AA patients. The frequencies of the six class I alleles in general Japanese population are much higher than those in the general Caucasian populations but similar to the frequencies in East Asian populations. The higher frequencies of the six alleles in comparison to Caucasian countries may account for the higher incidence of AA in East Asia. [Display omitted] DisclosuresTakamatsu:Ono: Research Funding; Bristol-Myers Squibb: Research Funding; Janssen: Honoraria; Celgene: Honoraria, Research Funding. Nakao:Novartis: Honoraria; Alexion Pharmaceuticals, Inc.: Consultancy, Honoraria; Kyowa Hakko Kirin Co., Ltd.: Honoraria.

Ex Vivo Gene-Edited Cell Therapy for Sickle Cell Disease: Disruption of the BCL11A Erythroid Enhancer with Zinc Finger Nucleases Increases Fetal Hemoglobin in Plerixafor Mobilized Human CD34+ Cells

Increases in fetal hemoglobin (HbF) are associated with improved clinical outcomes in the inherited hemoglobinopathies. We are developing a novel gene-edited cell therapy to treat patients with sickle cell disease (SCD) and beta-thalassemia (BT) using autologous hematopoietic stem and progenitor cells (HSPCs) genetically modified with zinc finger nucleases (ZFNs) to restore high levels of HbF expression. The ZFNs have been designed to specifically target the GATA motif within an intronic erythroid-specific enhancer (ESE) of BCL11A, the gene encoding a transcriptional regulator of the fetal-to-adult hemoglobin switch. Previously, we reported successful ZFN-mediated, ex vivoBCL11A gene editing in dual mobilized HSPCs, i.e. peripheral stem cells mobilized with a combination of granulocyte colony-stimulating factor (G-CSF) and plerixafor1. The editing procedure was optimized for high on-target/low off-target modification levels and increases in HbF in erythroid progeny. This drug product, ST-400, passed extensive safety testing and is currently in a phase 1/2a clinical trial for transfusion-dependent beta-thalassemia (ClinicalTrials.gov number NCT03432364).An analogous drug product, BIVV003, is being developed as a therapeutic for SCD. In patients with SCD, the use of G-CSF for stem cell mobilization is not recommended due to the risk of clinical complications. Therefore, peripheral HSPCs are obtained from SCD patients via single agent, plerixafor mobilization and apheresis2-5. Understanding the effect of this change in mobilization strategy on ZFN editing efficiency and specificity is a key element in preparing for SCD gene-edited cell therapy. In the present studies, we demonstrate comparability of ZFN editing outcomes in single and dual mobilized HSPCs obtained from healthy donors. In plerixafor mobilized HSPCs from five healthy donors at research scale, ZFN-mediated gene editing induced an efficient modification at the BCL11A ESE target site (>75% of alleles modified, as measured by MiSeq deep sequencing) with high post-editing viability (77%). Similar gene editing efficiencies (>70%) were obtained in HSPCs at clinical manufacturing scale (n=2). Further, in vitro HbF protein levels and HbF+ cell frequencies within erythroid progeny of edited cells were increased by >4 and 3-fold respectively - compared to non-edited cells in the same culture conditions, using reverse phase high-performance liquid chromatography and flow cytometry (n=4 healthy donors at research scale). Single cell clone analysis revealed that ZFN-mediated gene editing targeted both alleles of BCL11A at high frequency (91-94% of edited cells within erythroid progeny) with high levels of replicable GATA-disrupting indel patterns. On average, each edited allele contributed an additional 17.6% increase in HbF production in vitro, with a statistically-significant increase in HbF level for biallelic edited vs. unedited controls (3.4 fold).Critical to BIVV003 use in clinical trials, ZFN-mediated gene editing did not impair single agent mobilized HSPC function in vitro based on measurements of colony forming unit (CFU) production and frequencies of long-term HSC (LT-HSC) and common myeloid progenitor (CMP) cells by flow cytometry. In agreement with this data, injection of BIVV003 into immune-deficient NBSGW mice resulted in robust long-term engraftment (21 weeks) without any impact on the number of HSPCs and their differentiated progeny. Overall, these data demonstrate potential efficacy of ZFN-edited HSPCs (BIVV003) as a novel cell therapy for SCD patients.Holmes et al., 2017 (ASH abstract)Fitzhugh et al., 2009Lagresle-Peyrou et al., 2018Hsieh and Tisdale, 2018Yannaki et al., 2012 DisclosuresMoran:Bioverativ, a Sanofi Company: Employment. Ling:Bioverativ, a Sanofi Company: Employment. Lessard:Bioverativ, a Sanofi Company: Employment. Vieira:Bioverativ a Sanofi Company: Employment. Hong:Bioverativ, a Sanofi Company: Employment. Holmes:Sangamo Therapeutics: Employment. Reik:Sangamo Therapeutics: Employment. Dang:Sangamo Therapeutics: Employment. Gray:Sangamo Therapeutics: Employment. Levasseur:Bioverativ, a Sanofi Company: Employment. Rimmele:Bioverativ, a Sanofi Company: Employment.

Successful hematopoietic stem cell mobilization and apheresis collection using plerixafor alone in sickle cell patients

AbstractNovel therapies for sickle cell disease (SCD) based on genetically engineered autologous hematopoietic stem and progenitor cells (HSPCs) are critically dependent on a safe and effective strategy for cell procurement. We sought to assess the safety and efficacy of plerixafor when used in transfused patients with SCD for HSC mobilization. Six adult patients with SCD were recruited to receive a single dose of plerixafor, tested at lower than standard (180 µg/kg) and standard (240 µg/kg) doses, followed by CD34+ cell monitoring in peripheral blood and apheresis collection. The procedures were safe and well-tolerated. Mobilization was successful, with higher peripheral CD34+ cell counts in the standard vs the low-dose group. Among our 6 donors, we improved apheresis cell collection results by using a deep collection interface and starting apheresis within 4 hours after plerixafor administration. In the subjects who received a single standard dose of plerixafor and followed the optimized collection protocol, yields of up to 24.5 × 106 CD34+ cells/kg were achieved. Interestingly, the collected CD34+ cells were enriched in immunophenotypically defined long-term HSCs and early progenitors. Thus, we demonstrate that plerixafor can be employed safely in patients with SCD to obtain sufficient HSCs for potential use in gene therapy.

Preclinical Development of a Hematopoietic Stem and Progenitor Cell Bioengineered Factor VIII Lentiviral Vector Gene Therapy for Hemophilia A.

Genetically modified, autologous hematopoietic stem and progenitor cells (HSPCs) represent a new class of genetic medicine. Following this therapeutic paradigm, we are developing a product candidate, designated CD68-ET3-LV CD34+, for the treatment of the severe bleeding disorder, hemophilia A. The product consists of autologous CD34+ cells transduced with a human immunodeficiency virus 1-based, monocyte lineage-restricted, self-inactivating lentiviral vector (LV), termed CD68-ET3-LV, encoding a bioengineered coagulation factor VIII (fVIII) transgene, termed ET3, designed for enhanced expression. This vector was shown capable of high-titer manufacture under clinical scale and Good Manufacturing Practice. Biochemical and immunogenicity testing of recombinant ET3, as well as safety and efficacy testing of CD68-ET3-LV HSPCs, were utilized to demonstrate overall safety and efficacy in murine models. In the first model, administration of CD68-ET3-LV-transduced stem-cell antigen-1+ cells to hemophilia A mice resulted in sustained plasma fVIII production and hemostatic correction without signs of toxicity. Patient-derived, autologous mobilized peripheral blood (mPB) CD34+ cells are the clinical target cells for ex vivo transduction using CD68-ET3-LV, and the resulting genetically modified cells represent the investigational drug candidate. In the second model, CD68-ET3-LV gene transfer into mPB CD34+ cells isolated from normal human donors was utilized to obtain in vitro and in vivo pharmacology, pharmacokinetic, and toxicology assessment. CD68-ET3-LV demonstrated reproducible and efficient gene transfer into mPB CD34+ cells, with vector copy numbers in the range of 1 copy per diploid genome equivalent without affecting clonogenic potential. Differentiation of human CD34+ cells into monocytes was associated with increased fVIII production, supporting the designed function of the CD68 promoter. To assess in vivo pharmacodynamics, CD68-ET3-LV CD34+ cell product was administered to immunodeficient mice. Treated mice displayed sustained plasma fVIII levels and no signs of product related toxicity. Collectively, the findings of the current study support the preclinical safety and efficacy of CD68-ET3-LV CD34+.

Mobilization of Hematopoietic Progenitor Cells for Autologous Transplantation Using Pegfilgrastim and Plerixafor: Efficacy and Cost Implications

Filgrastim (FIL) is the most common growth factor combined with plerixafor for autologous hematopoietic progenitor cell mobilization, but requires daily, multi-injection administration. We adopted a standardized mobilization regimen with pegfilgrastim (PEG) and upfront plerixafor, allowing for a single injection given the long half-life and slow elimination of PEG. Between 2015 and 2017, a total of 235 patients with lymphoma or plasma cell dyscrasias underwent mobilization with PEG 6 mg on day 1 and upfront plerixafor 24 mg on day 3, followed by apheresis on day 4 regardless of peripheral blood CD34+ cells. The median CD34+ cells/mm3 in peripheral blood on first day of collection was 48 and median collection yield was 7.27 × 106 CD34+ cells/kg (range, 0.32 to 39.6 × 106 CD34+ cells/kg) after a mean of 1.6 apheresis collections. Overall, 83% of patients achieved the mobilization target, and 95% reached the minimum necessary CD34+ cell yield to proceed with transplantation (2 × 106 CD34+ cells/kg). Because FIL is weight-based and dosed daily, the cost comparison with PEG is influenced by patient weight and number of apheresis sessions required. A cost simulation using actual patient data indicates that PEG is associated with lower cost than FIL for the majority of patients. Autologous hematopoietic progenitor cell mobilization with PEG and plerixafor is practical, effective, and not associated with increased cost compared with FIL mobilization.

Combination therapy with carfilzomib, lenalidomide and dexamethasone (KRd) results in an unprecedented purity of the stem cell graft in newly diagnosed patients with myeloma.

Still, many physicians give 4 cycles of combination therapy to multiple myeloma patients prior to collection of stem cells for autologous bone marrow transplant. This tradition originates from older doxorubicin-containing regiments which limited the number of cycles due to cumulative cardiotoxicity. Using older regiments, most patients had residual myeloma cells in their autologous stem-cell grafts during collection. Emerging data show that newly diagnosed multiple myeloma patients treated with modern carfilzomib/lenalidomide/dexamethasone (KRd) therapy, on average, take 6 cycles until reaching minimal residual disease (MRD) negativity. We assessed newly diagnosed patients treated with KRd focusing MRD status both in the individual patient's bone marrow, and the corresponding autologous hematopoietic progenitor cell grafts during collection. Per protocol, stem-cell collection was allowed after 4 to 8 cycles of KRd. We found similar stem-cell yield independent of the number of cycles of KRd. At stem-cell collection, 11/30 patients (36.6%) were MRD negative in their bone marrow; all 11 patients had MRD negative hematopoietic progenitor cell grafts. Furthermore, 18/19 patients who were MRD positive in their bone marrows also had MRD negative hematopoietic progenitor cell grafts. These observations support 6 cycles of KRd as an efficacious and safe induction strategy prior to stem-cell collection.

Autologous hematopoietic progenitor cell mobilization and collection in adult patients presenting with multiple myeloma and lymphoma: A position-statement from the Turkish Society of Apheresis (TSA)

Autologous hematopoietic cell transplantation (AHCT) is a routinely used procedure in the treatment of adult patients presenting with multiple myeloma (MM), Hodgkin lymphoma (HL) and various subtypes of non-Hodgkin lymphoma (NHL) in upfront and relapsed/refractory settings. Successful hematopoietic progenitor cell mobilization (HPCM) and collection are the rate limiting first steps for application of AHCT. In 2015, almost 1700 AHCT procedures have been performed for MM, HL and NHL in Turkey. Although there are recently published consensus guidelines addressing critical issues regarding autologous HPCM, there is a tremendous heterogeneity in terms of mobilization strategies of transplant centers across the world. In order to pave the way to a more standardized HPCM approach in Turkey, Turkish Society of Apheresis (TSA) assembled a working group consisting of experts in the field. Here we report the position statement of TSA regarding autologous HPCM mobilization strategies in adult patients presenting with MM and lymphoma.

Current practice of autologous hematopoietic progenitor cell mobilization in adult patients with multiple myeloma and lymphoma: The results of a survey from Turkish hematology research and education group (ThREG)

Autologous hematopoietic cell transplantation (AHCT) is an established treatment option for adult patients presenting with multiple myeloma (MM), Hodgkin lymphoma (HL) and various subtypes of non-Hodgkin lymphoma (NHL) in upfront and/or relapsed/refractory disease settings. Although there are recently published consensus guidelines addressing critical issues regarding autologous hematopoietic progenitor cell mobilization (HPCM), mobilization strategies of transplant centers show high variability in terms of routine practice. In order to understand the current institutional policies regarding HPCM in Turkey and to obtain the required basic data for preparation of a national positional statement on this issue, Turkish Hematology Research and Education Group (ThREG) conducted a web-based HPCM survey. The survey was designed to include multiple-choice questions regarding institutional practice of HPCM in adults presenting MM, HL, and NHL. The representatives of 27 adult HCT centers participated to the study. Here we report the results of this survey shedding light on the real-world experience in Turkey in terms of autologous HPCM mobilization strategies in patients presenting with MM and lymphoma.

CMET-15. META-ANALYSIS OF TREATMENT MODALITIES IN METASTATIC ATYPICAL TERATOID/RHABDOID TUMORS IN CHILDREN

The aim of this study is to investigate the efficacy of different treatment modalities associated with best outcomes in the management of metastatic central nervous system (CNS) atypical teratoid/rhabdoid tumors (AT/RT) in children, which represent around 20% of newly-diagnosed AT/RT cases and are associated with dismal prognosis. A review of 1,433 peer-reviewed manuscripts from 1993 through June 2017 revealed 27 studies with a total of 80 metastatic AT/RT patients. The 3-year overall survival (OS) was 30% (95% confidence interval: 21–40%). Though treatment protocols varied widely by institution, the most-effective at improving the OS were the Medical University of Vienna AT/RT protocol, which incorporates radiation therapy (RT), intrathecal chemotherapy (IT), marrow-ablative chemotherapy and autologous hematopoietic progenitor cell rescue (AuHPCR) (3-year OS = 100%), and the Dana Farber protocol, which incorporates RT and IT (3-year OS = 57%). Gross total resection of the primary tumor was not associated with a significant improvement in the OS (p = 0.938). These results are further supported by a multivariable analysis, in which RT (p = 0.0139), IT (p = 0.0322), and AuHPCR (p <0.0001) were all independently associated with a reduced risk of death, with AuHPCR having the greatest impact on OS (Hazard Ratio = 0.21). Multimodal treatment approach should be incorporated in the management of metastatic CNS AT/RT in children and may include AuHPCR, with adjuvant RT and IT. Given the rarity of published research focused on metastatic AT/RT, these conclusions may be an important step towards the creation of standard treatment guidelines for metastatic AT/RT patients.

Granulocyte–Colony Stimulating Factor plus Plerixafor in Patients with β-thalassemia Major Results in the Effective Mobilization of Primitive CD34+ Cells with Specific Gene Expression Profile

Successful gene therapy for β-thalassemia requires optimal numbers of autologous gene-transduced hematopoietic stem and progenitor cells (HSPCs) with high repopulating capacity. Previous studies suggested superior mobilization in these patients by the combination of granulocyte–colony stimulating factor (G-CSF) plus plerixafor over single agents. We mobilized four adult patients using G-CSF+plerixafor to assess the intra-individual variation of the circulating CD34+ cells number and subtypes preand post-plerixafor administration. The procedure was well-tolerated and the target cell dose of ≥8 × 106 CD34+ cells/kg was achieved in three of them with one apheresis procedure. The addition of plerixafor unanimously increased the number of circulating CD34+ cells, and the frequency of the most primitive CD34+ subtypes: CD34+/38− and CD34+/133+/38− as well as the in vitro clonogenic potency. Microarray analyses of CD34+ cells purified from the leukapheresis of one patient mobilized twice, with G-CSF and with G-CSF+plerixafor, highlighted in G-CSF+plerixafor-mobilized CD34+ cells, higher levels of expression genes involved in HSPC motility, homing, and cell cycles. In conclusion, G-CSF+plerixafor in β-thalassemia patients mobilizes optimal numbers of HSPCs with characteristics that suggest high capacity of engraftment after transplantation.

Performance and safety of femoral central venous catheters in pediatric autologous peripheral blood stem cell collection.

Autologous peripheral blood hematopoietic progenitor cell collection (A-HPCC) in children typically requires placement of a central venous catheter (CVC) for venous access. There is scant published data regarding the performance and safety of femoral CVCs in pediatric A-HPCC. Seven-year, retrospective study of A-HPCC in pediatric patients collected between 2009 and January 2017. Inclusion criteria were an age ≤ 21 years and A-HPCC using a femoral CVC for venous access. Femoral CVC performance was examined by CD34 collection rate, inlet rate, collection efficiency (MNC-FE, CD34-FE), bleeding, flow-related adverse events (AE), CVC removal, and product sterility testing. Statistical analysis and graphing were performed with commercial software. A total of 75/119 (63%) pediatric patients (median age 3 years) met study criteria. Only 16% of children required a CVC for ≥ 3 days. The CD34 collect rate and CD34-FE was stable over time whereas MNC-FE decreased after day 4 in 80% of patients. CD34-FE and MNC-FE showed inter- and intra-patient variability over time and appeared sensitive to plerixafor administration. Femoral CVC showed fewer flow-related AE compared to thoracic CVC, especially in pediatric patients (6.7% vs. 37%, P = 0.0005; OR = 0.12 (95%CI: 0.03-0.45). CVC removal was uneventful in 73/75 (97%) patients with hemostasis achieved after 20-30 min of pressure. In a 10-year period, there were no instances of product contamination associated with femoral CVC colonization. Femoral CVC are safe and effective for A-HPCC in young pediatric patients. Femoral CVC performance was maintained over several days with few flow-related alarms when compared to thoracic CVCs.

Automatic washing of thawed haematopoietic progenitor cell grafts: a preclinical evaluation.

Autologous haematopoietic progenitor cell (HPC) is a prerequisite for high-dose chemotherapy in treatment of several haematologic and non-haematologic malignancies. HPCs are collected by apheresis and cryopreserved until infusion. Postinfusion adverse events have been in part related to the dimethyl sulphoxide (DMSO) used as cryoprotectant. The aim was to evaluate (i) an automated sequential washing procedure for DMSO removal in thawed HPC grafts and (ii) washing solutions in replacement of hydroxyethyl starch (HES)-based solutions. A total of 26 HPC bags cryopreserved with 10% DMSO and intended for disposal were used. The Sepax-2 (Biosafe, Eysins, Switzerland) was evaluated using a sequential washing procedure. Outcomes were CD34+ cell recovery and viability after washing. The Ringer lactate supplemented or not with albumin 2·5-5% presented satisfactory results compared with HES solution in terms of CD34+ cell recovery and viability after washing. However, the apparition of aggregates led us to renounce to these alternative solutions. Using HES solution and a sequential washing of three bags, we showed the elimination of 95% of the DMSO, a postwash viable CD34+ cell recovery of 79·9 ± 9·4% and a total nucleated cell viability of 66·5 ± 9·3%. The preclinical evaluation of an automated sequential washing procedure for DMSO removal in thawed HPC grafts has proven to be effective and comparable to previously published data. Despite our attempt to find an alternative solution to the HES solution, more efforts should be done on this side to reach a consensus on cryopreservation protocols.

Incremental Innovation of Ex Vivo Hematopoietic Stem Cell Engineering to Expand Clinical Gene Therapy Applications

Transplantation of genetically engineered, autologous hematopoietic stem and progenitor cells (HSPC) is becoming a promising alternative to allogeneic stem cell transplantation for curing genetic diseases, avoiding the risks of graft versus host disease and prolonged immunosuppression. Most clinical gene therapy protocols are based on CD34+ HSPC engineered during >2 days of ex vivo culture. By xenotransplanting mobilized peripheral blood (mPB) CD34+ HSPC, which were lentivirally (LV) marked with different fluorescent proteins according to CD38/CD90 expression levels allowing quantitative assessment of the contribution of CD38/CD90 subpopulations to hematopoietic reconstitution (n=48 NSG mice, 3 experiments), we identified 2 distinct waves of reconstitution: (1) short term repopulation (up to 2 months) mostly driven by CD34+CD38intCD90+/- cells and (2) long-term repopulation driven by CD34+CD38-CD90+ (70%) and CD34+CD38-CD90- cells (30%). Notably, an intermediate wave extending from 2 to 4 months driven by CD34+CD38low cells was selectively eliminated by prolonged ex vivo culture and could be rescued when culture time was reduced to 1 day. We therefore developed a novel LV transduction protocol able to provide curative levels of gene transfer during a single day of ex vivo culture. Stimulating CD34+ cells or CD34+CD38- cells with Prostaglandin E2 (PGE2) increased gene transfer with VSVg-pseudotyped LVs by 1.5-2 fold acting on early steps of transduction, an effect that was further potentiated by the late-acting compound Cyclosporin A. Using large-scale vector preparations for gene therapy of mucopolysaccharidosis type 1, chronic granulomatous disease or beta-thalassemia, we show by in vitro and xenotransplantation assays that a 1-day PGE2 protocol achieved similar transduction efficiencies into BM or MPB HSPC from healthy donors and patients as our 62h benchmark protocol. PGE2 treatment did not result in toxicity or skewed multi-lineage differentiation. However, shortening ex vivo culture increased engraftment levels in the NSG mouse model. To entirely avoid culturing progenitor cells, we explored the feasibility to limit ex vivo manipulation to HSC-enriched CD34+CD38- cells that may be co-transplanted with unmanipulated CD34+ progenitor cells devoid of long-term engraftment potential. This could further improve hematopoietic reconstitution, increase safety by reducing the LV integration load infused into the patient and downscale ex vivo manipulation making the process more efficient and economically sustainable. To this end, we optimized a sequential bead-based, GMP-compatible selection procedure to separate mPB into a CD34+CD38- stem and CD38+ progenitor cell fraction. We reached high purity (87+/-6.6% CD34+) and recovery of CD34+CD38- cells (37.3+/-8.7%), making their isolation clinically viable. Bead-selected CD34+CD38- cells showed higher engraftment potential than equivalent numbers of FACS-sorted cells. Co-infusion of unmanipulated (culture-sensitive) CD38+ supporter cells with genetically-engineered CD34+CD38- cells into NSG mice resulted in rapid engraftment followed by near-complete replacement of untransduced short-term repopulating progenitors by gene-marked HSPC deriving from CD34+CD38- cells after the 3rd month post-transplant. Finally, we explored ex vivo expansion of mPB CD34+CD38- cells with arylhydrocarbon receptor antagonists and/or pyrimido-indole-derivatives. These cells expanded 3-10 fold in a 7-14 d time-window, far less than seen for total CD34+ cells, thereby facilitating culture handling and reducing cost. Unlike CD34+ cells, expanded mPB CD34+CD38- cells largely maintained their SCID-repopulating potential providing proof-of-concept for the expansion of gene-modified HSC. This clinically applicable platform will improve the efficacy, safety and sustainability of ex vivo gene addition and open up new opportunities in the field of gene editing. DisclosuresCiceri:MolMed SpA: Consultancy.

Mobilization of hematopoietic progenitor cells for autologous transportation: consensus recommendations

Selected patients with certain hematological malignancies and solid tumors have the potential to achieve long-term survival with autologous hematopoietic progenitor cell transplant. The collection of these cells in peripheral blood avoids multiple bone marrow aspirations, results in faster engraftment and allows treatment of patients with infection, fibrosis, or bone marrow hypocellularity. However, for the procedure to be successful, it is essential to mobilize a sufficient number of progenitor cells from the bone marrow into the blood circulation. Therefore, a group of Brazilian experts met in order to develop recommendations for mobilization strategies adapted to the reality of the Brazilian national health system, which could help minimize the risk of failure, reduce toxicity and improve the allocation of financial resources.

Is peripheral access for apheresis procedures underutilized in clinical practice?-A single centre experience.

The majority of reports regarding general vascular access choices for apheresis procedures argue that peripheral venous access should be considered first. However, the clinical reality appears to be different. While some procedures mandate central vascular access (e.g., therapeutic apheresis procedures in critically ill patients) and in some cases it is the patient's preference, we propose that the majority of elective procedures can be successfully performed peripherally. To establish the feasibility and suitability of peripheral access for different apheresis procedures, undertaken in elective or emergency settings. The choice of vascular access devices and cannulation sites were analysed retrospectively from all apheresis procedures performed between January 2014 and December 2015 at a single institution. Over 2 years a total of 3714 procedures were performed on 1061 patients. Absolute number of procedures (percentage) done peripherally: autologous and allogeneic hematopoietic progenitor cell harvest-400 (88%) and 458 (97%) respectively; mononuclear cell harvest-88 (93%); automated red cell exchange-1954 (80%); therapeutic plasma exchange-766 (26%); white blood cell depletion-48 (71%). Choice of vascular access for all procedures (absolute number [percentage]): peripheral and ultrasound-guided peripheral deep vein cannulation-2683 (72%); central venous catheter access: femoral-331 (9%); jugular-511 (14%); subclavian-2 (<1%); double-lumen port-187 (5%). Peripheral access in all apheresis procedures (emergency and elective) was 72%; for purely elective procedures this number increased to 80% to 97%, depending on the procedure. In our institution the majority of elective apheresis procedures are successfully performed using peripheral access.

Procedure-related complications and adverse events associated with pediatric autologous peripheral blood stem cell collection.

Autologous peripheral blood hematopoietic progenitor cell collection (A-HPCC) in pediatric patients is considered relatively safe although technically challenging. Very little is known regarding the incidence, risk factors and impact of procedure-related adverse events (AE) on pediatric A-HPCC outcomes. Prospective 4.5-year review of AE associated with pediatric A-HPCC. AE were graded by severity and type. Potential demographic and procedural risk factors, and the impact on product quality, were compared by t-test, chi-square, and linear regression. Sixty-two children underwent 110 A-HPCC, including 36 (58%) under 20 kg. Fifty-five AE were documented in 25.4% A-HPCCs and 39% of children (citrate 25%, access 19%, technical 11%, cardiovascular 0%, allergic 1.8%). No AE were noted in children < 10 kg anticoagulated with heparin. Access and technical AE accounted for 73% of severe AE, with line-related problems underlying most technical AE (87.5%, P = 0.006). AE were more likely in older (P = 0.012), heavier patients (P = 0.02), who frequently required more than one A-HPCC (P = 0.012). In contrast, young children were more likely to experience citrate AE with gastrointestinal symptoms (median age, 6 years; P = 0.076). AE had no impact on CD34 collection rates; however, mean CD34 yields (4.2 vs. 20.4 million/kg; P = 0.0035) were decreased in patients with technical AE due to lower peripheral CD34 counts and a high number of aborted procedures (37%). Venous access and flow-related issues are a major factor associated with moderate and severe AE, effecting ∼10% of patients. AE are more frequent with increasing patient age, weight, and number of procedures. J. Clin. Apheresis 32:35-48, 2017. © 2016 Wiley Periodicals, Inc.

A novel hematopoietic progenitor cell mobilization regimen, utilizing bortezomib and filgrastim, for patients undergoing autologous transplant.

Adequate hematopoietic progenitor cell (HPC) collection is critical for patients undergoing autologous HPC transplant (AHPCT). Historically, 15 - 30% of patients failed HPC mobilization with granulocyte-colony stimulating factor (G-CSF) alone. Bortezomib, a proteasome inhibitor, has been shown to down regulate very late antigen-4 (VLA-4), an adhesion molecule expressed on HPCs. In this pilot study, bortezomib was administered on days -11 and -8 at a dose of 1.3 mg/m2 intravenously (IV) or subcutaneously (SQ), followed by G-CSF 10 mcg/kg SQ, on days -4 to -1 prior to HPC collection (Day 1). Nineteen patients, with multiple myeloma (n = 12) or non-Hodgkin lymphoma (n = 7) undergoing AHPCT for the first time, were enrolled. Patients were excluded if they had worse than grade II neuropathy or platelet count less than 100 x 109 /L. Bortezomib was well tolerated and all patients had adequate HPC collections with no mobilization failures. One patient (6%) had a CD34+ cell count of 3.9 cells/µL on Day 1 and received plerixafor per institutional algorithm. Eleven patients completed HPC collection in 1 day and eight in 2 days. All patients underwent AHPCT and had timely neutrophil and platelet engraftment. Comparison with a historical control group of 70 MM and lymphoma patients, who were mobilized with G-CSF, showed significantly higher CD 34+ cells/kg collected in the bortezomib mobilization study group. Bortezomib plus G-CSF is an effective HPC mobilizing regimen worth investigating further in subsequent studies. J. Clin. Apheresis 31:559-563, 2016. © 2015 Wiley Periodicals, Inc.