PMN Engraftment Research Articles

Outcomes of Matched Unrelated Donor Allogeneic Stem Cell Transplants with High CD34-Positive Cell Dose: A Single Center Experience

Introduction: CD34+ peripheral blood stem cells serve as the primary source for the majority of allogeneic stem cell transplants for hematologic malignancy, and adequate cell numbers must be infused to ensure engraftment. While the target dose is typically 5x106 cells/kg, there have been conflicting data on the effect of higher doses on outcomes. Due to concern for adverse effects, such as graft-versus-host disease (GVHD), some groups have suggested capping the CD34+ cell dose; however, various levels have been recommended, and the majority of studies have only small numbers of patients at very high cell doses where any effects may be most evident. In addition, manipulation of grafts can be time-consuming and lead to an increased risk of contamination. To better assess the effect of high cell dose on outcomes, we reviewed patients at our center who received matched unrelated donor (MUD) transplants with CD34+ dose in the highest quintile. Methods: We performed a single-center retrospective analysis of adult patients with hematologic malignancy who received a MUD allogeneic stem cell transplant with CD34+ cell dose in the highest quintile (>13x106 cells/kg) from 2005 to 2021. Data were collected on patient and donor demographics, disease and transplant characteristics, and CIBMTR risk index. Outcomes were compared with the remaining MUD transplant patients during the same time period, including overall survival (OS), relapse-free survival (RFS), transplant-related mortality (TRM), GVHD rates and severity, and engraftment kinetics, with survival data censored at 10 years. Patients who received multiple transplants or had cryopreserved grafts were excluded. Neutrophil (PMN) engraftment was defined as the first of 3 consecutive days with absolute neutrophil count >500 cells/µL, and platelet (PLT) engraftment defined as the first of 3 consecutive days with PLT count >20x103 cells/µL and at least 7 days after most recent transfusion. Demographic data and GVHD rates were compared by Fisher's exact test or chi-squared test; age by Welch's t-test; engraftment kinetics medians by Mann-Whitney U test; and OS, RFS, and TRM by Kaplan-Meier analysis with log-rank (Mantel-Cox) test for significance. Results: 36 patients were identified in the highest quintile with a median CD34+ dose of 16.83x106 cells/kg (range: 13.02-39.02) compared to 139 control patients with median dose of 7.74x106 cells/kg (2.72-12.99). Patients in the high-dose group were more likely to be female (58.3% vs 38.8%, p=.04), with no other statistically significant differences in donor, recipient, or disease characteristics (Table 1). There was a trend toward faster PLT engraftment in the CD34-high group (median 16 vs 16.5 days, p=.058), but there was no effect on PMN engraftment time (14 vs 14, p=.78). There was no difference in incidence of acute GVHD, either grade 2 or above (33.3% vs 36.0%, p=.85) or grade 3 or above (19.4% vs 15.8%, p=.62), and the groups showed similar incidence of chronic GVHD both overall (38.9% vs 48.2%, p=.35) and for severe disease (13.9% vs 11.5%, p=.77). There was no significant difference in OS between the two groups by Kaplan-Meier analysis (Figure 1, p=.44). Comparing the CD34-high group to the control group, the estimated 2-year survival was 47.2% vs 55.7%, and the estimated 5-year survival was 37.3% vs 45.2%. There was similarly no difference in RFS or TRM (p=.34 and p=.55, data not shown). Conclusions: Previous studies of the effect of CD34+ cell dose on transplant outcomes have been limited by small numbers of patients at the highest doses. In this single-center study using one of the highest dose cutoffs in the literature (>13x106 cells/kg), we showed a trend toward faster PLT engraftment with no difference in GVHD incidence or mortality. As a retrospective study, a major limitation is possible confounding, and we plan to include other potential factors, such as GVHD prophylaxis, in multivariate analysis, though our initial results did not show major differences in baseline characteristics. In this cohort, patients receiving very high CD34+ cell doses had similar outcomes to those receiving standard doses. These data do not support the routine use of graft reduction by CD34+ cell number, which may help guide future practice. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

The Determinative Role of Hematopoietic Stem and Progenitor Cell Graft Composition on the Engraftment Kinetics after HSCT

The importance of hematopoietic stem and progenitor cell (HSPC) dose in the outcome of hematopoietic stem cell transplant (HSCT) has been demonstrated by analyses of the threshold dose of CD34+ cells required to achieve donor engraftment, usually defined as endpoints of donor-derived neutrophil (PMN) or platelet (PLT) absolute numbers, and RBC transfusion independence. We recently described the heterogeneous HSPC composition of prospectively obtained umbilical cord blood samples and lack of correlation between CD34+ cell dose and the frequency of hematopoietic stem cells (HSC)(Mantri S et al, Blood Adv 2020).We describe here a pilot analysis of the relationship between HSPC graft composition and engraftment after HSCT. The study population is comprised of 17 children (3.4-22 years, median 13 years) treated with αβT/CD19B - cell depleted mobilized peripheral blood stem cell (PBSC) HSCT (αβhaplo-HSCT). Eight patients had acute lymphoblastic leukemia, seven had acute myeloid leukemia, and two myelodysplastic syndrome. All patients received serotherapy with Thymoglobulin and Rituximab, and a myeloablative conditioning consisting of either TBI 1200 cGy in combination with Fludarabine/Thiotepa (15 patients), Melphalan/Thiotepa (1 patient), or TBI (400 cGy) with Fludarabine/Thiotepa (1 patient receiving a second HSCT). Only 2/17 patients received 1-2 doses of G-CSF before Day+30.The CD34+ Lin- cells in the PBSC products were analyzed for HSPC composition, including HSC (CD38- CD90+ CD45RA-), Multipotent Progenitors (MPP, CD38- CD90- CD45RA-), Common Myeloid Progenitors (CMP, CD38+ CD123+ CD45RA-), Granulocyte-Monocyte Progenitors (GMP, CD38+ CD123+ CD45RA+), Megakaryocyte-Erythroid Progenitors (MEP, CD38+ CD123- CD45RA-) and Common Lymphoid Progenitors (CLP, CD38+ CD127+). Similar HSPC analyses were performed on marrow obtained at Days +30, +60, and +90 post-HSCT. The CD34+ cell dose in the grafts ranged from 8.5-40 x 10e6/kg recipient body weight (mean 15.6). The median time to Absolute Neutrophil Count (ANC) > 500 or 1000/mm 3 were Days +12 and +14, respectively, and for PLT > 50K or 100K/mm 3 Days +14 and +15, respectively. The time to either PMN or PLT engraftment did not correlate with the HSC dose. In contrast, the GMP dose was predictive of PMN engraftment: 7/8 patients receiving the highest GMP dose achieved ANC > 500 at 0-3 days before the median day of engraftment, while PMN engraftment was delayed by 1-5 days beyond the median in 6 of the 9 receiving the lowest GMP dose (χ 2 = 8.14, p=0.004)(Fig A). Of the patients with the highest MEP dose, 7/8 achieved PLT >50K/mm 3 0-4 days before the median, while 5/9 receiving the lowest dose engrafted 1-6 days beyond the median (χ 2 4.9, p=0.026) (Fig B). In the first 100 days post-HSCT, naïve CD4+ T-cells were all CD31+ CD45RA+ Recent Thymic Emigrants (RTE), indicating that they were newly produced T cells and not adoptively transferred from the αβhaplo-HSCT. The HSC dose did not correlate with the number of naïve CD4+ T cells until Day+180 (Fig C). Like PMN and PLT recovery, early T lymphoid recovery after HSCT was mainly derived from infused CLP, and likely switched to HSC-derived lymphopoiesis by Day +180. Consistent with this concept, HSC dose in the PBSC products was unrelated to the numbers of committed progenitors, e.g., CMP, MEP, CLP, in early (Day +30) post-transplant marrow samples.These data are consistent with clonal analyses of patients receiving lentiviral gene therapy and murine experiments demonstrating prolonged steady-state contribution of committed progenitors to peripheral blood cell maintenance (Biasco L et al, Cell Stem Cell 2016; Sun J et al, Nature 2014). While post-HSCT PMN or PLT numbers are frequently equated with “HSC engraftment” and naïve T-cell numbers with HSC-derived immune reconstitution, these early events reflect blood cell production by committed progenitors, which are variably present in the grafts. Although CD34+ cell dose is currently used to predict post-transplant engraftment and to qualify stem cell products for release, more accurate clinical predictions may be determined by the HSPC grafts' composition. Further, engineering of the progenitor composition of clinical HSCT products, e.g., co-transplantation of additional committed progenitors like GMP or CLP, could be strategically used to control post-transplant lymphohematopoietic recovery. [Display omitted] DisclosuresParkman: Jasper Biotech: Consultancy. Bertaina: Cellevolve Bio: Membership on an entity's Board of Directors or advisory committees; Neovii: Membership on an entity's Board of Directors or advisory committees; AdicetBio: Membership on an entity's Board of Directors or advisory committees.

BEAM Vs Cyclophosphamide-Based Conditioning Regimen in Aggressive Multiple Sclerosis: A Retrospective Analysis of European Blood and Marrow Transplantation Society

Background Multiple Sclerosis (MS) is a chronic, immuno-mediated disease of Central Nervous System (CNS), mostly affecting young adults and frequently resulting in a progressive, irreversible disability despite the administration of approved Disease Modifying Treatments (DMTs). Autologous HSCT was shown to induce a high rate of sustained, treatment-free remissions in cases of aggressive MS, seldom associated to a partial reversal of disability. Toxicity of Conditioning Regimen is still a major concern. We retrospectively analyzed the outcome of 926 MS patients reported to the EBMT Registry who underwent autologous HSCT following the two most frequent CRs for this indication in the last 20 years. Patients and Methods Patient data were extracted from both the EBMT database and a disease-specific database developed by the EBMT Autoimmune Diseases Working Party (ADWP). Patients were selected for having received either BEAM + ATG (BEAM) or HD-Cyclophosphamide + ATG (CYC) as conditioning regimen. Hematological toxicity was assessed through Neutrophil (PMN) engraftment and 100-days (early) mortality (eTRM). MS forms at HSCT were reported as Relapsing-Remitting (RR), Secondary Progressive (SP), Primary Progressive (PP) and Progressive-Relapsing (PR). The impact of variables related to both patients (age, gender, year of HSCT, EDSS at HSCT) and disease characteristics (MS form, interval diagnosis-HSCT) at HSCT in the two groups were also evaluated. Results The utilization of conditioning regimens along the observed time period (1998-2018) was variable, with an increase of the HSCT activity in general after 2010 (230 vs 697 procedures) and a prevalence of BEAM before 2010 (205 BEAM vs 25 CYC) and of CYC thereafter (205 BEAM vs 492 CYC, p=0.001). Also, RR forms of MS prevailed over Progressive forms after 2010 (p=0.001) which is reflected in the different distribution across the two regimens, with RR significantly more frequently treated with CYC-based regimen (p<0.001). Gender distribution and age at HSCT was similar in the two groups (p=ns), whilst the interval between diagnosis and HSCT was longer in BEAM group than CYC (8.47 years ± 5.9 vs 7.57 ±5.5, mean ± SD, p=0.012). PMN engraftment in BEAM/ATG- and CYC/ATG-treated patients occurred at +11.0 (8-42) and +10.9 (8-95) days, respectively (median and range, p=ns). Overall eTRM was low (1.4%), but slightly higher in BEAM over CYC (8/402, 2% vs 5/517, 1%, p=ns). Discussion Although autologous HSCT is increasingly used as a treatment in highly active MS, toxicity remains a principal concern in the neurological community despite a marked decrease of TRM over time. The intensity of conditioning regimens has varied in the literature, but the best toxicity/efficacy ratio remains unclear. The non-myeloablative regimen CYC-ATG has become the most common conditioning regimen despite a lack of comparative data with more intense regimens. In our large retrospective analysis of the two most frequent conditioning regimens in the EBMT Registry, there was no significant difference in major toxicity indicators despite differences in chronological period and patients characteristics in the two groups. Comparative analysis of neurological efficacy is currently ongoing and will inform the toxicity/efficacy ratio and clinical choice of conditioning regimen in autologous HSCT in MS. Disclosures Mielke: Bellicum: Consultancy, Honoraria, Other: Travel (via institution); Jazz Pharma: Honoraria, Other: Travel support, Speakers Bureau; IACH: Other: Travel support; Kiadis Pharma: Consultancy, Honoraria, Other: Travel support (via institution), Speakers Bureau; Miltenyi: Consultancy, Honoraria, Other: Travel and speakers fee (via institution), Speakers Bureau; DGHO: Other: Travel support; GILEAD: Consultancy, Honoraria, Other: travel (via institution), Speakers Bureau; Celgene: Honoraria, Other: Travel support (via institution), Speakers Bureau; ISCT: Other: Travel support; EBMT/EHA: Other: Travel support.

Outcomes after Double Umbilical Cord Blood Transplantation in Children: A Survey on Behalf of Eurocord and PDWP-EBMT

Double UCBT (dUCBT) has been used in adults to reach an acceptable cell dose. For most children a single unit with a total nucleated cell (TNC) dose >3x107/Kg can be easily identified, but that is not always the case for heavier patients (pts). Use of dUCBT might decrease relapse and increase graft-versus-host-disease (GvHD). Data on dUCBT in children are scarce in the literature. A recent randomized study in children has described similar outcomes after double compared to single UCBT. Our study provides an overview of the use of dUCBT in the pediatric population reported to Eurocord.We retrospectively analyzed the outcomes of unrelated dUCBT in 177 children transplanted between 2002 and 2012 in 61 EBMT centres. Analysis was performed separately for pts with malignant (n=139) and non-malignant (NM, n=38) diseases.Among pts with malignancies, 76 had ALL, 40 AML, 6 MDS, 2 CML, 11 NHL, 3 Hodgkin Lymphoma and 1 Multiple Myeloma. Median age at dUCBT was 15 years (1.3-17.9) and median weight was 55 kg (13-97). Disease status at dUCBT was 1st complete remission (CR) (36%), ≥2nd CR (34%) or advanced (25%), and missing in 5% of the pts. In this group, 117pts received a myeloablative conditioning (MAC) and 22 a reduced intensity regimen (RIC). Cyclophosphamide+fludarabine+TBI was administered to 41% of the pts; 55% received ATG in the conditioning. Median number of collected TNC was 5.7x107/kg (3,6-12,8). Considering the unit with the higher number of HLA incompatibilities with the recipient, 56% had 2 mismatches. GvHD prophylaxis was cyclosporine-A (CSA) based in 93% of the pts (58% received CSA + mycofenolate mofetil). Median follow-up was 31 months. Cumulative incidence (CI) of neutrophil (PMN) and platelet (PLT) engraftment was 88% at 60 days and 64% at 180 days after dUCBT, and it was achieved with a median time of 24 and 45 days, respectively. Among the 122 pts with PMN engraftment, 85/94 with available data on chimerism were full donor and, of these, 20% had dual chimerism. CI of acute GvHD grade II-IV and grade III-IV at 100 days was 51% and 26%, respectively; it was significantly higher in pts who did not receive ATG (grade II-IV: 35% vs 67%, p=0.004; grade III-IV: 12% vs 37%, p=0.0075). Chronic GvHD was observed in 24/104 pts at risk (60% extensive; 2-year (yr) CI: 18%). The 2-yr CI of relapse was 31%. In univariate analysis, RIC, advanced stage at transplantation and a collected TNC dose lower than the median, were significantly associated with higher rates of relapse.The 2-yr CI of transplant related mortality (TRM) was 27%. Overall, 73 pts died: 35 of relapse, 15 of infections, 9 of GvHD and 14 of other causes. The 2-yr disease free survival (DFS) and overall survival (OS) were 42% and 45%, respectively.Among pts with NM disorders, 24 had bone marrow failure syndrome (BMFS) (10 Fanconi Anemia, 13 Acquired Aplastic Anemia and 1 other inherited BMFS), 2 hemoglobinopathies, 7 immune deficiencies and 5 metabolic disorders. Median age at dUCBT was 11 years (0.7-17.9) and the median weight was 40 kg (13-70). In this group, 27 pts received a RIC (40% TBI based), 10 a MAC (90% busulfan based), and 1 no conditioning regimen. ATG was administered to 82% of the pts and GvHD prophylaxis was CSA-based in 77%. The median number of collected TNC was 8.4x107/kg (1,2-11,2) and 60% of the grafts had ≥2 HLA mismatches with the recipient. Median follow-up was 39 months. Overall, 28 pts achieved PMN engraftment and 16 PLT engraftment, with a median time of 23 and 61 days, respectively. In univariate analysis, pts with BMFS compared to others had a significantly lower CI of PMN engraftment (58% vs 100%, p=0.002). Among the 10 pts who did not engraft, 3 had autologous reconstitution and 3 had a subsequent allogeneic HSCT. Forteen pts developed acute GvHD grade II-IV and 10/25 pts at risk had chronic GvHD (3 extensive). Overall 21 pts died (17 with BMFS): 9 of infections, 5 of GvHD and 7 of other causes. The 2-yr OS was 42% and it was significantly lower in pts with BMFS compared to those affected by other NM disorders (28% vs 70%, p=0.03).In pts with malignancies, despite a higher incidence of acute GvHD, DFS and OS seem to be comparable to those reported in the literature for single UCBT or HSCT from other alternative stem cell sources. In the NM disorders group, despite the high cell dose, dUCBT did not seem to improve results in pts with BMFS. This survey suggests that dUCBT is feasible in children and should be considered when a single unit with an adequate cell dose is not available. DisclosuresNo relevant conflicts of interest to declare.

Evaluation of MRD Status by Flow Cytometry and PCR in Multiple Myeloma Elderly Patients Receiving Autologous Stem Cell Transplantation After Bortezomib-Supplemented Mobilization and Conditioning

AbstractAbstract 4523Autologous Stem Cell Transplantation (ASCT) is still an option for eligible patients with Multiple Myeloma (MM). High-dose melphalan (HDM: 200mg/m∧2) is the recommended conditioning before ASCT, but synergistic effects of Bortezomib (BOR) and HDM have been reported in vitro and in vivo. PATIENTS AND METHODS:We evaluated in 56 MM fit elderly patients (median age 65 yrs), the feasibility and efficacy (also in terms of evaluation of minimal residual disease: MRD) of a strategy, combining BOR, Cyclophosfamide (CY) and dexamethasone (DEX) as induction and mobilizing therapy (CY-BOR), for ASCT, with conditioning including BOR-HD-MEL. The patients achieving at least PR after 4 CY-BOR courses, were mobilized with BOR and DEX standard schedule with CY 3g/m∧2 (day 8). The pts collecting at least 2.5×10∧6CD34+/kg underwent ASCT with HD-MEL (day-1) and BOR (1.0mg/m∧2 on -6,-3,+1,+4), followed by thalidomide consolidation until Relapse/Progression. The MRD has been prospectively evaluated both by using 4 colour flow cytometry (FC), and by using patient-specific probes, by ASO-PCR. The percentage of plasma cells (PCs) has been evaluated both in in PBSC harvested and in bone marrow, with CD38, CD45, CD56, CD138, CD19, CD27, CD28, CD117, kappa and lambda, along different steps of therapy. RESULTS:Of 44 pts evaluable for response before ASCT, 32 (73%) achieved 3PR and 30 (68%) were mobilized: 29 (66%) collected3 2.5×106CD34+/kg and 25 underwent ASCT. Median time for PMN engraftment was 11 days (range 10–13) and 14 (range12–20) for PLT>=20.000/mcl. We observed grade 3 neuropathy in 3 patients and pneumonia during induction in 2 patients. At day +180 from ASCT 23 are evaluable for response and 21 for MRD: 3 pts have progressive disease (PD), 2 pts have a PR, 4 pts have a VGPR, 10 pts a nCR and 4 pts a CR. Four colour FC, in order to detect clonal plasmacells (cPCs) along several steps of treatment, showed that 3 pts (14%) achieved MRD negativity: 1/21 pts achieved MRD negativity at day +180 (cPC <0.01%), being positive after induction and at day +90 after ASCT; two patients were MRD negative after induction (one developed positivity at day + 180 and relapsed at day +365 from ASCT; the other one became positive at day +90 after ASCT and, is in CR at 10 months from ASCT). In 5 patients we evaluated MRD by PCR with patient-specific probes. One patient achieved clearance of MRD after induction and still maintains negative of PCR at 27 months from ASCT: this patient had positivity of MRD by flow cytometry after induction and at 90 months from ASCT, then became negative and is in CR. One became PCR negative after ASCT: flow cytometry was negative too and the patient is in CR at 10 months from ASCT; the remaining three patients are PCR positive: two of them experienced progression of disease. CONCLUSIONS:ASCT with HDM and BOR is feasible in older patients, with very high RRs and without major toxicities. We need a longer follow up and a larger number of pts to assess if these results will translate in a benefit in terms of outcome. Disclosures:Fragasso:Mundipharma: Honoraria.

Unmanipulated Bone Marrow Transplantation From Haploidentical Related Donor for Patients with High-Risk Hematological Malignancies

AbstractAbstract 2350In this study we investigated the feasibility and clinical value of non T-cell depleted bone marrow transplantation (BMT) from HLA haploidentical related donor in patients with high risk hematological malignancies. Materials and Methods.Between August 2005 and May 2010, 71 patients were transplanted for acute myeloid leukemia (AML) (n=42), acute lymphoblastic leukemia (n=13), chronic myeloid leukemia (n=5), Hodgkin lymphoma (n=5), plasmacell leukemia (n=3), myelofibrosis (n=2) and myelodisplastic syndrome (n=1). Their median age was 35 years (5-71). At time of BMT, all patients were at very high risk: 39 were in early (complete remission 1 or 2) and 31 in more advanced stage of disease. Seventeen of them were given a previous transplant either autologous (n=14) or allogenic (n=3). All donors were HLA identical at 1 haplotype and mismatched for 2 (n=24) or 3 (n=47) loci on the unshared haplotype. As pretransplant regimen, 10 patients received a reduced intensity conditioning consisting of Fludarabine (Flu) alone (n=1), Flu + Thiotepa (Thio) + Melphalan (n=2) or Flu + Thio + i.v.Busulphan (Bu) (n=7), and 61 patients received a myeloablative therapy consisting of Aracytin + Cyclophosphamide combined with TBI (n=7) or Treosulphan (n=11) or Bu (n=11), whereas the last 32 consecutive patients underwent transplant after conditioning with the association of Thio + Flu + i.v. Bu. All patients received an identical graft-versus-host disease (GvHD) prophylaxis consisting of Fresenius Antithymocyte Globulin (5 mg/Kg/d from day -4 to -1) combined with Cyclosporine (1,5-3 mg/Kg/day i.v. from day -7 to +28 and orally 5 mg/Kg until day +365), Methotrexate (15 mg/sqm on day +1 and 10 mg/sqm on day +3, +6 and +11), Mycophenolate Mofetil (1 g/d from day +7 to +100) and the anti-CD 25 monoclonal antibody Basiliximab (20 mg i.v. on day 0 and +4). Bone marrow cells were harvested from all donors after priming with Filgrastim at 3–4 microg/Kg/d from day -7 to -1. Bone marrow cells were infused fresh and unmanipulated on day 0. Results.The median dose of total nucleated, CD34+ and CD3+ cells infused was 7.8 (1-28) ×108/kg, 2.1 (0.8-11) ×106/Kg and 28 (10-98) ×106/Kg, respectively. One patient had a primary graft failure and 5 patients died too early to be evaluated for engraftment. Results in terms of cumulative incidence (CI) of PMN engraftment, acute and chronic GvHD, relapse, transplant related mortality (TRM) and overall survival (OS) estimated with the Kaplan Meyer method are given in the Table. After a median follow-up of 16 (3-56) months, the 3 years probability of OS and disease-free survival (DFS) was 43% and 37% respectively for all patients (see Figure). The 3 years OS for the 42 patients with AML was 48% (61% for 30 patients transplanted in early stage and 18% for 12 patients transplanted in advanced stage, P=0.01). The 1 year OS for the 32 patients transplanted with the conditioning therapy employed in the last 2 years (Thio + Flu + i.v. Bu) was 72% in 18 patients transplanted in early stage and 52% in 14 patients transplanted in advanced stage (P=0.47).Early stageAdvanced stageAll patientsP valueN.393271CI of PMN engraftment at day 3087±0.381±0.588+0.7NSCI of acute GvHD grade II - IV34±0.716±0.626±0.3NSCI of acute GvHD grade III - IV9±0.43±0.16±0.1NSCI of chronic GvHD8±0.214±0.811±0.1NSCI of relapse at 2 years30±0.737±133±0.4NSCI of TRM at 1 year21±0.441±0.530±0.3NSCI of TRM at 2 years24±0.548±1.336±0.6NSOS at 3 years54±9.226±9.943±70.03 [Display omitted] Conclusions.BMT from haploidentical donor using G-CSF primed, unmanipulated bone marrow cells and an intensive regimen for GVHD prophylaxis is correlated with high engraftment rate, low incidence of acute and chronic GVHD, acceptable TRM and favourable patient outcome. The results seem particularly encouraging for AML patients grafted at an early disease stage. In alternative to transplant from matched unrelated donor or cord blood, this approach can be offered to high risk patients with hematological malignancies particularly for those who are on urgency for a transplant.Results are given as % ± standard error Disclosures:No relevant conflicts of interest to declare.

Successful Stem Cell Mobilization Rescue by AMD3100 (Plerixafor)+G-CSF for Patients Who Failed Primary Mobilization: Results from the Phase III (3101-NHL) Study.

Background: AMD3100 (plerixafor)+G-CSF (A+G) was generally safe and more effective in mobilizing CD34+ hematopoietic stem cells compared to placebo+G-CSF (P+G) in a Phase III, multicenter, randomized, double-blind, placebo controlled study conducted in patients with non-Hodgkin's lymphoma (NHL). In the intent-to-treat analysis, 78/148 (53%) patients in the P+G group and 20/150 (13%) patients in the A+G group failed to mobilize ≥ 2 x 106 CD34+ cells/kg, p<0.0001. Of these failure patients, 52 in the P+G group and 10 in the A+G group consented to enter into the rescue arm of the study. This abstract reports the outcomes of these rescue patients.Methods: Patients enrolled in the Phase III study who failed to mobilize ≥2 x 106 CD34+ cells/kg could enter into the rescue arm of the study and receive A+G. The patient's treatment assignment in the study remained blinded. Following a rest period of ≥7 days, patients were given G (10 μg/kg/day) subcutaneously (SQ) for 4 days. In the evening around 10PM on Day 4, patients were given a dose of A (240 μg/kg SQ). On Day 5, all patients returned to clinic to receive a morning dose of G before apheresis. Patients continued to receive the evening dose of A followed by morning dose of G and apheresis the next day for up to a total of 4 aphereses or until ≥5 x 106 CD34+ cells/kg were collected. Pooled cells were allowed for transplantation.Results: After rescue therapy, 33/52 (63%) patients who previously failed P+G and 4/10 (40%) patients who previously failed A+G collected ≥2 x 106 CD34+ cells/kg. Seven of the 33 patients who previously failed with P+G collected ≥ 5 x 106 CD34+ cells/kg. Six of the ten A+G patients and 46/52 P+G patients were transplanted. Median time to PMN engraftment was Day 10 and Day 11 for the A+G and P+G groups, respectively. Median time to platelet engraftment was Day 22 and Day 20 for the A+G and P+G groups, respectively. One patient in the P+G group never had platelet counts > 50,000 and was counted as a failure to engraft, even though the patient was clinically stable through 6 months post-transplant. In the re-mobilized group, 9 patients died (2 patients were never transplanted and 7 patients had disease progression). Grafts were durable for ≥100 days in all 6 rescued A+G patients and all 41 rescued P+G patients who engrafted. The predominant adverse events were mild gastrointestinal effects (diarrhea, nausea, vomiting, and abdominal pain) and injection site reactions. There were no drug-related serious adverse events reported in these re-mobilized patients.Conclusions: The addition of AMD3100 to G-CSF successfully mobilized sufficient stem cells for transplant in 63% of NHL patients who previously failed mobilization with G-CSF alone. The high success rate is consistent with the Compassionate Use Protocol experience. AMD3100 was generally well tolerated. The 40% success rate in the patients who previously failed AMD3100+G-CSF suggests that re-mobilization with the same combination is a potentially useful strategy for similar patients.

Single Agent AMD3100 Mobilization of Peripheral Blood Progenitor Cells for Autologous Transplantation in Patients with Multiple Myeloma (MM).

Background: The addition of AMD3100 to a G-CSF mobilization regimen increases the number of hematopoietic stem and progenitor cells (HSPCs) that can be collected by apheresis, allowing the successful (re)mobilization and transplantation of MM patients. This single-arm, open-label, study was therefore initiated to determine if AMD3100 alone could successfully mobilize HSPCs in MM patients for autologous stem cell transplantation (ASCT). This is the first clinical trial of HSPCs mobilized by AMD3100 alone in the autologous transplant setting.Methods: Patients received 240 μg/kg AMD3100 followed by apheresis 6 hours later. Dosing and apheresis could be repeated for up to 4 consecutive days or until ge;4 × 106 CD34+ cells/kg were collected. Post-transplant follow-up included daily WBC measurements until leukocyte engraftment (≥0.5 × 109/l for 3 consecutive days or ≥1 × 109/l for 1 day), and platelet engraftment (≥20 × 109/l for 7 days).Results: Nine patients have been enrolled. The median number of CD34+ cells collected was 2.7 × 106/kg (Range:1.9– 4.6), completed in 4 apheresis days by 8 patients and 3 days by 1 patient. Six patients (67 %) mobilized ≥2 × 106 CD34+ cells/kg and 2 pts (22 %) mobilized ≥4 × 106 CD34+ cells/kg. All patients were transplanted; 1 patient received tandem transplants with study cells; 1 patient received tandem transplants, the first transplant with study cells followed by a second transplant with G-CSF mobilized cells. Median time to PMN engraftment was 10 days (Range: 10–11 days); median time to PLT engraftment was 21 days (Range: 15–33 days, except for 1 patient with platelet recovery some time between day 23 and 82). One patient with Plasma Cell Leukemia died of disease relapse at 6 months. Engraftment was durable with a follow-up of over 19 months in the earliest transplanted patient. AMD3100 was safe and generally well tolerated with the most common adverse events being injection site reactions, GI upset, and paresthesias. There were no drug-related severe adverse events.Conclusions: AMD3100 alone mobilizes autologous HSPCs that provide prompt and durable engraftment, indicating that AMD3100 mobilizes functional HSPCs independent of the presence of G-CSF. These results are consistent with and reinforced by observations made using AMD3100 to mobilize allogeneic HSPCs [Devine et al., ASH 2005, #299]. While the number of cells mobilized by AMD3100 alone is relatively modest, AMD3100 plus G-CSF mobilizes a more primitive subset of CD34+ cells than G-CSF alone which could potentially translate into fewer CD34+ cells being required for transplantation when AMD3100 is part of the mobilization regimen [Seeger et al., ASH 2005, #1969]. Therefore, further evaluation of dose and schedule, as well as the role of CD34+ phenotype, is required to optimize HSPC mobilization with single-agent AMD3100.

Unrelated Cord Blood Transplantation (UCBT) in Children with Sickle Cell Disease (SCD): US Centers Experience.

UCBT may be curative in patients (pts) with high-risk SCD. Unrelated cord blood units matched at >4/6 HLA are acceptable for UCBTs and available to most pts. We reviewed UCBTs in 7 children with SCD and cerebrovascular accidents performed in 4 centers (1998 to 2003): 4 pts were conditioned with conventional myeloablative regimens, and 3 pts with reduced-intensity regimens. The former received busulfan (BU), cyclophosphamide (CY) and anti-thymocyte globulin (ATG) (3 pts) or BU/CY/ATG plus fludarabine (FLU) (1 pt). Of 3 pts who received 4/6 HLA-matched UCBTs after BU/CY/ATG and GVHD prophylaxis with methylprednisone (MP) and cyclosporine (CSP) or tacrolimus (TAC), 2 have durable engraftment, 1 had autologous reconstitution (BMT 2004; 34:405–11). A 5 yr old (yo) female with transfusion-induced alloimmunization received a 5/6 HLA-matched UCBT (6.2 X 10^7/kg nucleated [NC] cells) after BU/CY/ATG/FLU, followed by CSP and MP post-transplant. PMN engraftment and VNTR > 98% of donor origin were documented 24 and 37 days, respectively, after UCBT. Complications included elevated liver enzymes during conditioning, grade IV GVHD of skin, GI and liver, grade III mucositis, VOD, parainfluenza 3 infection, candidemia and adenovirus viremia. Pt died of severe acute GVHD and multi-organ failure 73 days after UCBT. Two different reduced-intensity regimens were used in the other 3 pts. An 8 yo male received a 4/6 HLA-matched UCBT (3.2 X 10^7/kg NC) after conditioning with alemtuzumab, rituximab, hydroxyurea, thiotepa and TBI (600cGy, with 300 cGy total dose to liver and kidneys) and received TAC and mycophenolate mofetil (MMF) post-transplant. This patient failed UCBT 8 months earlier (FLU/CY/ATG/TLI, 4/6 HLA). PMN engraftment and VNTR > 98% of donor origin was documented within 18 days after UCBT. Complications included grade I skin GVHD, grade 1 mucositis and parainfluenza 1 infection. This pt remains engrafted and fully active 1.6 ys after UCBT. A 4 yo female and a 16 yo male received 4/6 or 5/6 HLA-matched cord units, respectively, after BU or CY, ATG, FLU and total lymphoid irradiation (200 or 500 cGy) and received CSP and MMF post-transplant. Neither had evidence of donor engraftment, and autologous reconstitution was documented within 2 weeks after UCBT. Sustained donor engraftment occurred in 3/4 pts (75%) who underwent UCBT after myeloablative conditioning and 1/3 pts (33%) who underwent UCBT after reduced-intensity conditioning. Two of the 3 pts who engrafted after myeloablative preparative regimens developed acute grade III–IV GVHD, and 1 of these pts developed extensive chronic GVHD. The 1 pt who engrafted after a reduced-intensity preparative regimen developed grade I acute GVHD only. Significant viral infections (CMV 1 pt, adenovirus, parainfluenzavirus 2 pts each) occurred in 4 pts. In this limited experience, following various conditioning regimens, optimal GVHD and infection prevention remains a challenge. Both apparent lesser risk and documented durable engraftment may justify further development of non-myeloablative strategies for UCBT in children with high-risk SCD.

High-dose thiotepa and etoposide in children with poor-prognosis brain tumors.

Outcome data were analyzed for 27 patients who were affected with recurrent or newly diagnosed high-risk brain tumors and who underwent high-dose chemotherapy with triethylenethiophosphoramide (thiotepa) and etoposide in addition to autologous stem cell transplantation between May 1992 and September 2002. Fifteen males and 12 females (median age, 11 years) were included in the study. Twelve patients had newly diagnosed high-risk brain tumors, and 15 patients had recurrent brain tumors. The conditioning regimen consisted of thiotepa 900 mg/m2 and etoposide 1500 mg/m2 over 3 days starting on Day -5. Stem cell rescue was performed using bone marrow (BM) in 8 patients, peripheral blood stem cells (PBSCs) in 18 patients, and BM and PBSCs in 1 patient. For the BM group, neutrophil (PMN) engraftment was achieved on Day +14 (median value), whereas platelet (PLT) engraftment was achieved on Day +68 (median value). One patient did not achieve PLT engraftment. For the PBSC group, the PMN engraftment was achieved on Day +10.0 (median value), and the PLT engraftment was achieved on Day +15.5 (median value). Transplantation-related toxicity (evaluated using the Bearman score) included Grade 2-3 mucositis in 16 patients, Grade 1 kidney toxicity in 6 patients, Grade 1 liver toxicity in 6 patients, and Grade 2 liver toxicity in 1 patient. Transplantation-related mortality was observed in 1 patient (3.6%), who died of Candida pneumonia. The 3-year overall survival (OS) rate was 44.6%, and the 3-year event-free survival (EFS) rate was 31%. There was a statistically significant difference in OS and EFS rates for patients who underwent ASCT and achieved complete remission compared with patients who had measurable disease. The results of the current study suggest that high-dose chemotherapy followed by ASCT may be beneficial for patients who achieve complete remission before ASCT, whereas for other patients, new strategies are required.