Reduced Conditioning Regimen Research Articles

Developing an Allogeneic Hematopoietic Progenitor Cell Transplant Service in a Resource-Limited Country: Challenges and Outcomes.

Introduction Allogeneic stem cell transplant has curative potential for many hematological disorders. Building an allogeneic hematopoietic progenitor cell transplant (HPCT) unit requires huge investment, infrastructure, equipment, medical supplies, and training of health care professionals. The key objective of this study is to share our experience of developing an allogeneic HPCT service at our tertiary care cancer hospital in a low-middle-income country. In addition, this study presents the outcomes of the first 30 allogeneic HPCTs done at our center. Methods This retrospective observational study included adult patients 18 years old or older with hematological malignancies who underwent allogeneic HPCT between July 2019 and April 2023 at Shaukat Khanum Memorial Cancer Hospital and Research Centre. Result Of the 30 patients, 24 underwent matched sibling donor (MSD) transplants in which a myeloablative-conditioning regimen (MAC) was used in 19, and a reduced conditioning regimen (RIC) was used in one. Of the six haploidentical-related donor transplants, four received MAC, and two received RIC. The median recipient age at HPCT was 23 and 21 years for MSD and Haplo-related donor transplants, respectively. The median follow-up duration was 12 months (Range: 10 days - 33 months). The overall survival rate at one yearwas 71.3% among all allogeneic stem cell transplant patients, whereas the disease-free survival rate at one yearwas 63.7%. In the acute lymphoblastic leukemia group, the disease-free survival rate at one year post allograft was 51.5%, while in the acute myeloid leukemia group, it was 78.7%. Conclusion This study demonstrates the successful development of an allogeneic bone marrow transplant unit at our hospital despite significant financial constraints. This has allowed us to provide a potentially curative and life-saving treatment to a substantial number of cancer patients. The bone marrow transplant outcomes of this study are comparable to those reported by international bone marrow transplant registries.

Conditioning Regimens in Allogeneic Hematopoietic Stem Cell Transplantation Do Not Fit All: Adjusting BuCy2 in Mexico to Improve Outcomes in Acute Myeloid Leukemia (AML) and Myelodysplastic Syndrome (MDS).

Background: Conditioning regimens are critical for allogeneic hematopoietic cell transplantation (allo-HCT). After unfavorable results using BuCy2 at the beginning of our HCT Program, a restructuring was made with the consequent development of a modified HCT method including a reduced conditioning regimen. The objective of this study was to describe the outcomes using Reduced BuCy2 (rBuCy2) in allo-HCT. Materials and Methods: Data from 38 consecutive patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) who underwent allo-HCT conditioned with rBuCy2 in a 21-year period were retrospectively analyzed. Results: Most patients were males (53%) and the median age was 35 years. The most common disease was myelodysplastic syndrome (55%). Toxicity grades III-IV were observed in 44%; and acute and chronic graft-versus-host disease were observed in 26% and 34%, respectively; the median follow-up was 26 months; 30-day non-relapse mortality (NRM) was 3%, and 1 and 2-year NRM were 8%. Ten-year overall survival (OS) was 60%, and 86%, for AML and MDS, respectively. Conclusion: Our rBuCy2 maintains a myeloablative effect, along with immunosuppression for fast engraftment and more importantly, this regimen reduces grades III-IV acute GVHD and NRM in allo-HCT and improves the OS and it appears to be an option for low and middle-income countries.

Palliative care pilot initiative for transplant patients: The Westchester Medical Center experience.

e19050 Background: It is well known HCT recipients experience multiple symptoms affecting quality of life. Emerging data supports the role palliative care can play in mitigating these issues. Our cellular therapy team collaborated with the Palliative Care team on a pilot project incorporating their expertise into the management of our new allogeneic transplant patients. We chose this group of patients given their increased needs relative to other cellular therapy recipients (i.e. autologous, CTL) and our institution’s available resources. Methods: Patients admitted to the HCT unit for allogenic stem cell transplant underwent palliative care consult during their conditioning regimen. During the initial palliative care visit, performed by a specialist palliative care nurse practitioner, patients underwent comprehensive assessment of physical symptoms, psychosocial distress, and overall quality of life. Patients were then followed during hospitalization by members of the palliative care team including Nurse Practitioner, Social Worker and Chaplain, to address identified needs and support both the patient and their family. The palliative care team provided daily communication and recommendations to our inpatient HCT team. Results: Patient one was a 61-year-old man with intermediate risk MDS who underwent a reduced intensity conditioning regimen of busulfan, fludarabine, and alemtuzumab. His transplant was complicated by delirium and anorexia. Patient two was a 63-year-old man with AML who underwent a reduced conditioning regimen of the same combination. His transplant was complicated by bone pain and insomnia. Patient three was a 70-year-old woman with AML who also underwent a reduced conditioning regimen. Her transplant was complicated by severe mucositis and gastric reflux. Conclusions: Allogeneic stem cell transplant patients experience a multitude of symptoms and psychosocial distress. With the help of a dedicated palliative care assessment, we can improve patients’ quality of life during their admission for the transplant. Considering the positive feedback from patients, we plan to conduct a formal prospective study evaluating the impact of palliative care on adult stem cell transplant patients at our institution. By addressing the patient’s whole person rather than just their disease, we also hope to decrease number of admissions as well as length of stay. Ultimately, we look forward to expanding this to other malignancies as well.

Impact of Vitamin D Deficiency on Survival for Patients Received Haploidentical Hematopoietic Stem Cell Transplantation (haplo-HSCT)

BackgroundBeyond its role in bone health, vitamin D is known to have immunomodulatory effects including cell proliferation, differentiation and apoptosis. Delays in immune reconstitution following HSCT increase transplant-related toxicity. Several studies have explored the role of vitamin D deficiency after HSCT with mixed results regarding its impact on survival outcomes. Our aim in this study was to examine the impact of vitamin D deficiency prior to HSCT on transplant outcomes in patients who received a haplo-HSCT.MethodsThis retrospective study included consecutive patients who underwent haplo-HSCT at our institution between 02/2009 and 01/2021. Primary objectives were to assess progression-free survival (PFS) and overall survival (OS) by vitamin D status at the time of transplant. Vitamin D deficiency was defined as vitamin D levels < 20 nmol/L within 6 months prior to transplant. Survival estimates were calculated using Kaplan-Meier method. Proportional cox hazards analysis was used to adjust for multivariable analysis (MVA).ResultsFour-hundred and eighty-four patients out of 508 patients had vitamin D checked at baseline and were included in the final analysis. Table 1 summarizes patient, disease, and transplant characteristics for all study patients, and by vitamin D status. Median age for all study patients was 48 (18-72) years, of which 237 (49%) had vitamin D deficiency and 247 (51%) had normal vitamin D level. Overall, the two groups were comparable, except that patients in the vitamin D deficiency group were younger in age. Furthermore, we adjusted for disease subtype heterogeneity by using the validated disease risk index (DRI). With a median follow-up of 35.4 (range, 1.4-132.8) months, the 3-year PFS and OS for all study patients were 44% and 48%, respectively. The respective 3-year PFS and OS for the vitamin D deficiency group were 42% and 47% compared to 46% and 50% for patients with adequate vitamin D (p=0.773 for PFS; p=0.704 for OS). Furthermore, we found no difference in non-relapse mortality at 3 years (each for 30%; p=0.6682). Univariate analysis (UVA) was performed for the following variables: vitamin D, age, gender, KPS, DRI, HCT-CI, and intensity of conditioning regimen. MVA included only the factors with p value<0.1 in in the UVA (plus vitamin D). In UVA for PFS, age ≥55, KPS <90, high/very-high DRI, HXT-CI >3 and reduced intensity conditioning were associated with inferior outcome. Same factors were significantly associated with inferior OS, but the reduced conditioning regimen. In MVA, age ≥55 (HR 1.627, 95% CI: 1.212-2.212; p=0.0013), high/very-high DRI (HR 1.865, 95% CI: 1.427-2.437; p=<0.0001), and HCT-CI >3 (HR 1.314, 95% CI: 1.001-1.726; p=0.0493) were associated with decreased PFS. Patients in the vitamin D deficiency group had a trend towards decreased PFS (HR 1.292, 95% CI: 0.975-1.712; p=0.0746), but this didn't reach statistical significance. In regard to OS, age ≥55 (HR 1.727, 95% CI: 1.278-2,334; p=0.0004), high/very-high DRI (HR 1.855, 95% CI: 1.396-2.467; p=<0.0001), and HCT-CI >3 (HR 1.411, 95% CI: 1.058-1.882; p=0.0191) were again associated with decreased OS, while vitamin D deficiency patients showed a trend for decreased OS (HR 1.312, 95% CI: 0.973-1.77; p=0.0753).ConclusionOur study demonstrates that serum vitamin D levels prior to haplo-HSCT have no significant impact on either progression-free or overall survival, albeit with a trend for worse outcomes in the vitamin D deficient group. Prospective controlled studies are needed to assess the impact of vitamin D deficiency on transplant outcomes, and on the role of vitamin D supplementation to improve the outcomes. [Display omitted] DisclosuresQazilbash: Bristol-Myers Squibb: Other: Advisory Board; Oncopeptides: Other: Advisory Board; Angiocrine: Research Funding; Amgen: Research Funding; Biolline: Research Funding; NexImmune: Research Funding; Janssen: Research Funding. Shpall: Navan: Consultancy; Novartis: Honoraria; Axio: Consultancy; Magenta: Honoraria; Takeda: Patents & Royalties; Bayer HealthCare Pharmaceuticals: Honoraria; Adaptimmune: Consultancy; Affimed: Patents & Royalties; Magenta: Consultancy; Novartis: Consultancy.

Stem cell transplantation for pediatric patients with adrenoleukodystrophy: A nationwide retrospective analysis in Japan.

Adrenoleukodystrophy (ALD) is an X-linked recessive disorder and 30-40% of patients develop progressive cerebral neurodegeneration. For symptomatic ALD patients, allogeneic stem cell transplantation (SCT) is considered the standard treatment modality to stabilize or prevent the progression of neurological symptoms. We retrospectively analyzed the transplant outcomes of 99 pediatric patients with cerebral ALD in Japan. The conditioning regimens included Regimen A: fludarabine/melphalan/low-dose total body irradiation (TBI) with brain sparing (n=39), Regimen B; busulfan/cyclophosphamide±others (n=23), Regimen C: melphalan/total lymphoid irradiation/thoracoabdominal irradiation±anti-T lymphocyte globulin±fludarabine (n=27), and Regimen D: others (n=10). The 5-year overall survival (OS) and event-free survival (EFS) of all patients were 90.0% and 72.9%, respectively. The 5-year OS was 100.0% for Regimen A, 91.1% for Regimen B, 84.4% for Regimen C, and 67.5% for Regimen D (p=0.028). The 5-year EFS was 78.3% for Regimen A, 78.0% for Regimen B, 70.4% for Regimen C, and 48.0% for Regimen D (p=0.304). The OS marginally improved after 2007 compared with before 2006 (95.3% vs. 85.2%, p=0.066), due to the improvement of cord blood transplantation (CBT) outcomes after 2007 compared with before 2006 (96.6% vs. 68.4%, p=0.005). On magnetic resonance imaging of the brain, a reduced Loes score after SCT was only observed in one of the 15 bone marrow transplantation (BMT) patients, but in 5 of the 15 CBT patients (p=0.173). Our study revealed that a reduced conditioning regimen with fludarabine/melphalan/low-dose TBI provides better outcomes, and the results of CBT significantly improved after 2007.

Impact of induction chemotherapy with intermediate-dosed cytarabine and subsequent allogeneic stem cell transplantation on the outcome of high-risk acute myeloid leukemia

BackgroundAcute myeloid leukemia (AML) with antecedent hematological disease (s-AML) and treatment-related AML (t-AML) predicts poor prognosis. Intensive treatment protocols of those high-risk patients should consider allogeneic stem cell transplantation (allo-HSCT) in first complete remission (CR). Despite allo-HSCT, relapse rate remains high. Induction chemotherapy with liposomal cytarabine and daunorubicin (CPX-351) has been approved for patients with AML with myeloid-related changes (AML-MRC) or t-AML based on improved survival and remission rates compared to standard 7 + 3 induction.Patients and methods110 patients with newly diagnosed s-AML or t-AML at a university hospital were analyzed retrospectively. Median age was 62 years (24–77 years). A total of 65 patients with s-AML after MDS (59%) and 23 patients (20.9%) with t-AML were included. Induction chemotherapy consisted of intermediate-dosed cytarabine (ID-AraC) in combination with idarubicin (patients up to 60 years) or mitoxantrone (patients over 60 years). In patients subsequently undergoing allo-HSCT, reduced conditioning regimens (RIC) were applied prior to transplantation in 47 of 62 patients (76%).ResultsInduction chemotherapy with ID-AraC resulted in an overall response rate of 83% including complete remission (CR/CRi) in 69 patients (63%) with a low rate of early death (2.7%). Most relevant non-hematologic toxicity consisted of infectious complications including sepsis with need of intensive care treatment in five patients (4.5%) and proven or probable invasive fungal disease in eight patients (7.2%). Relapse-free survival (RFS), event-free survival (EFS) and overall survival (OS) of the whole cohort were 19 months (0–167), 10 months (0–234) and 15 months (0–234), respectively (p < 0.0001). A significant improvement of OS was observed in patients who underwent allo-HSCT compared to those without subsequent allo-HSCT: 9 vs. 46 months, p < 0.0001. Rate of transplantation-related mortality (TRM) in the early phase post allo-HSCT was low (0.9% at day 30 and 1.8% at day 90, respectively). RIC conditioning results in OS rate of 60% after 60 months post allo-HSCT (median OS not reached).ConclusionS-AML and t-AML patients receiving induction chemotherapy with intermediate-dosed cytarabine showed satisfactory response rate and consolidation therapy with allo-HSCT after full or reduced-intensity conditioning further improved survival in these patients with similar outcome as reported for CPX-351.

Immune Reconstitution after Allogeneic Stem Cell Transplantation - a Systematic Single Center Survey

The renewal of the immune system after allogeneic hematopoietic stem cell transplantation (HSCT) is a complex process not fully understood. Recently, the use of reduced intensity conditioning (RIC) regimens, new anti-viral drugs and intensified GvHD treatment changed the landscape of allogeneic transplantation. Here, the influence of several parameters on the development of the cellular and humoral immunity of 136 patients consecutively transplanted in a single center was analyzed.All adult patients transplanted during a period of three years (September 2010 to August 2013), were analyzed in respect of immunoglobulin levels with the turbidimetric method, serum electrophoresis, immunofixation and lymphocyte subset counts by flow cytometry. Also the occurrence of a monoclonal/biclonal gammopathy was reported. In addition, we looked for donor chimerism, B and T cell receptor repertoire of peripheral blood samples. Most patients received a reduced conditioning regimen; nearly all patients received either anti-thymoglobulin (ATG) or alemtuzumab (25/136 matched related donors) leading to a relatively low rate of chronic GvHD (40%). The immune parameters obtained one year after stem cell transplantation were correlated with relevant factors of stem cell transplantation, namely the conditioning regimen, diagnosis, relapse rate, age, sex and history of CMV infection, acute and chronic GvHD using Pearson correlation, t-test and regression analysis (SPSS).A normal CD4/CD8 ratio at day 360 after HSCT was only seen in 14% of evaluable patients, while it was reduced in 83%. This was mainly due by an impaired CD4 cell count while the CD8 cell count was even increased in 42%. The CD8 cell count was significantly higher in patients after CMV infection (p<0.001) and in those not receiving alemtuzumab as part of the conditioning regimen (p=0.003). The IgG level was normal in 51%, reduced in 31% and increased in 17 % of tested patients. The IgG level correlated with a history of CMV infection, NK, CD4, and CD8 cell count (all p≤0.025); but age, sex, diagnosis, relapse, use of RIC, acute and chronic GvHD had no significant impact. The development of a new clonal gammopathy was found in 18 patients after undergoing a HSCT and was in nearly all cases reversible. Interestingly, this was associated with chronic GvHD (p=0.034), but not any of the other parameters.Almost all patients show a compromised immune system one year after allogeneic stem cell transplantation mainly characterized by an inverted CD4/CD8 ratio. Whether an increased CD8 cell count may not only reflect the response to viral infections but in some cases improved immunosurveillance, is hard to document. Interestingly, the immunoglobulin levels are highly variable ranging from antibody deficiency to hypergammaglobulinemia positively correlating with CMV reactivation. Continuous disbalanced immunoreactivity indicated by clonal gammopathy was associated with chronic GvHD. The systematic evaluation of these basic immune parameters may lead to better therapeutic guidance in patients after allogeneic HSCT. DisclosuresNo relevant conflicts of interest to declare.

Clofarabine/Busulfan-Based Reduced Intensity Conditioning Regimens Provides Very Good Survivals in Patients Allografted in Remission for Acute Myeloid Leukemia: A Retrospective Study on Behalf of the SFGM-TC

Introduction: Clofarabine/busulfan based reduced conditioning regimens (RIC) have been developed recently with the hope to improve outcomes in older patients allografted for myeloid malignancies. Indeed, clofarabine, a second generation purine analogue, has been proved to have higher anti-leukemic myeloid activity compared to fludarabine, a drug extensively used as part of RIC for allogeneic stem cell transplantation (allo-SCT). However, larger studies are needed to confirm these results.Method: This was a retrospective study including all patients who received a clofarabine/busulfan based RIC allo-SCT for myeloid malignancies and reported within the SFGM-TC registry. Data were obtained through PROMISE, an internet-based system shared by all European transplantation centers. All patients gave informed consent allowing to collect their personal data from this data base.RIC regimen consisted of clofarabine 30 mg/m²/day 4 to 5 days (Clo), busulfan 3.2 mg/kg/day 2 days (B2) and one or two days of rabbit antithymocyte globulin (A1 or A2). CloB2A2 have been used first as a conditioning platform while some centers have used CloB2A1 since 2014 in order to try to decrease relapse and improve the results of the CloB2A2 patients.The primary objective of the study was to report the main outcomes of the whole cohort at 2 years: overall survival (OS), disease free survival (DFS), relapse incidence (RI), non-relapse mortality (NRM) and GVHD and Relapse-free survival (GRFS). Secondary objectives were to identify prognostic factors and to compare outcomes between CloB2A2 (n=43)/CloB2A1 (n=41) cases.Results: Between January 2008 and December 2016, 84 patients (males n=47, median age 61.6 years) met the inclusion criteria. The majority of patients had acute myeloid leukemia (AML, n=63) while 21 cases had myelodysplastic or myeloproliferative syndrome. Sixty-one patients were in complete remission (CR) at time of transplant (CR1 n=49. CR2, n=12), including 55 AML cases (CR1 n=43; CR2 n=12). All patients but one (bone marrow graft) received peripheral blood stem cell as graft source. All patients received matched donors (sibling n=34; unrelated n=50). There were no significant differences in term of characteristics between CloB2A2 (n=43, median follow-up 39 months) and CloB2A1 (n=41, median follow-up 21 months) patients, except the median age of the cohort which was higher in the latter group (65 vs 61 years, p=0.02) and, as expected, the median year of transplant (2013 vs 2015, p<0.001). All patients engrafted except one CLOB2A1 case.With a median follow up of 31 months (range: 5.7-74.1) for patients alive, 2-year OS, DFS, RI, NRM and GRFS were 64.5% (53.8-75.2); 57.2% (46.2-68.2); 27.7% (18.2-37.9); 15.1% (8.2-23.9) and 43.6% (32.5-54.7), respectively, for the whole cohort. Considering AML in remission, 2-year OS, DFS, RI, NRM and GRFS were 74.2% (62-86.5); 66.8% (53.6-79.9); 23.4% (12.7-36); 9.8% (3.5-19.9) and 50.9% (36.9-64.9), respectively.2-year outcomes were similar between CloB2A1 and CloB2A2 sub-groups: OS 61.2% (43.8-78.6) vs 65.1% (50.9-79.4), p=0.93; DFS 60.8% (44.9-76.6) vs 54.7% (39.6-69.7), p=0.93; RI 28.8% (15.1-44) vs 26.3% (14-40.3), p=0.51; NRM 10.5% (3.2-22.7) vs 19% (8.8-32.2), p=0.55; GRFS 45% (27.9-62) vs 41.7% (27-56.5), p=0.96. Comparable outcomes were also observed when considering only AML patients in CR. However, a trend for lower NRM within the CloB2A1 subgroup was observed (4.2% (0.3-18.1) vs 16% (4.8-33), p= 0.14).In multivariate analysis, active disease at transplant was the only factor adversely impacting 2 years outcomes.Conclusion: CloB2A2/A1 RIC regimens provides very good results for AML patients allografted in CR. CloB2A1 should be retained as a RIC platform for these patients. Our results have to be confirmed prospectively. DisclosuresPeffault De Latour:Amgen: Research Funding; Pfizer: Consultancy, Honoraria, Research Funding; Alexion Pharmaceuticals, Inc.: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding. Mohty:Sanofi: Honoraria, Speakers Bureau.

Combining Mobilizing Agents with Busulfan to Reduce Chemotherapy-Based Conditioning for Hematopoietic Stem Cell Transplantation.

In the context of hematopoietic stem cell (HSC) transplantation, conditioning with myelo- and immune-ablative agents is used to eradicate the patient’s diseased cells, generate space in the marrow and suppress immune reactions prior to the infusion of donor HSCs. While conditioning is required for effective and long-lasting HSC engraftment, currently used regimens are also associated with short and long-term side effects on extramedullary tissues and even mortality. Particularly in patients with severe combined immunodeficiency (SCID), who are generally less than 1-year old at the time of transplantation and often suffer from existing comorbidities. There is a pressing need for development of alternative, less toxic conditioning regimens. Hence, we here aimed to improve efficacy of currently used myeloablative protocols by combining busulfan with stem-cell niche-directed therapeutic agents (G-CSF or plerixafor) that are approved for clinical use in stem cell mobilization. T, B and myeloid cell recovery was analyzed in humanized NSG mice after different conditioning regimens. Increasing levels of human leukocyte chimerism were observed in a busulfan dose-dependent manner, showing comparable immune recovery as with total body irradiation in CD34-transplanted NSG mice. Notably, a better T cell reconstitution compared to TBI was observed after busulfan conditioning not only in NSG mice but also in SCID mouse models. Direct effects of reducing the stem cell compartment in the bone marrow were observed after G-CSF and plerixafor administration, as well as in combination with low doses of busulfan. Unfortunately, these direct effects on the stem population in the bone marrow were not reflected in increased human chimerism or immune recovery after CD34 transplantation in NSG mice. These results indicate moderate potential of reduced conditioning regimens for clinical use relevant for all allogeneic transplants.

Mixed Chimerism after Allogeneic Hematopoietic Stem Cell Transplantation in Patients with β Thalassemia: Impact on Outcome and Risk Factors

Background: Hematopoietic stem cell transplantation (HSCT) is the most effective curative option for patients with thalassemia major(TM). Early post-transplant mixed chimerism (MC) has known to be a predictor of secondary graft rejection. However, the impact of the persisting mixed chimerism on transplant outcome remains controversial. Recently Thiotepa(TT) has been decreased to reduce toxicity.There was no data available on reduced intensity conditioning on mixed chimersim in a large group of patients with thalassemia to date. Aims: To assess risk factors of mixed chimerism and to evaluate possible correlations between mixed chimerism and the development of complications after HSCT, in terms of graft versus host disease (GVHD) development, OS, TFS and GR. Patients and methods: From December2008 until December 2019, 618 patients with TM underwent HSCT at our center with median age of 6 (1-23) and median follow up time of 70 months(1-135), from HLA-identical sibling donors (SD) (n=212; 34.3%), unrelated donors (UD, n=313; 50.6%),sibling Cord blood(CB, n=49,7.9%)and parent donors (PD, n=44,7.1%). Source of graft were 538 (87.1%) from peripheral stem cells, 32(5.2%) from bone marrow and 48(7.8%)from sibling cord blood. Cy+Bu+Flu+TT+ATG conditioning regimen was used in 416 pts while a reduced conditioning regimen Cy+Bu+Flu+ATG was used for 167pts and Cy+Bu+Flu for the other 35 pts. Results Overall Survival (OS), Thalassemia-Free survival (TFS), Transplantation-related mortality (TRM) and graft rejection (GR) for the entire group were 94.8%, 92.7% ,5.2% and 2.4% respectively. MC was presented in 70 pts with 52 male and 18 female, defined as the presence of &amp;gt;5% residual recipient cells. Cumulative incidence of MC was 12.4% (Figure1). 5 pts had secondary graft failure and another 5 patients persisting MC post-transplant refractory to DLI following a second HSCT. There were two deaths ineffective to DLI and one die of idiopathic pneumonia and one of hemolytic uremic syndrome. The median MC present time was 4 months (1-59 months).No significant difference was observed in OS and Thalassemia-Free survival (TFS) between MC and PC pts. The cumulative probability of OS, TFS between MC pts and FC pts was 97.1% vs. 94.4% (P=0.343) and 89.6% vs. 93.2% (P=0.272). However, the incidence of MC was significantly associated with the development of graft failure/rejection. Graft failure occurred in 5 pts in the MC group vs.7 pts in the full donor chimerism (PC) group, the corresponding incidence were 7.6% vs. 1.6 % respectively. (P =0.001, Figure 2). Acute GVHD incidence was much lower in MC pts than in PC pts (2.9% vs. 12.7%, P=0.022, Figure 3 A), whereas MC pts had significantly higher chronic GVHD(16.8% vs. 4.2%, P=0.000 Figure 3 B). 2 of 70 MC pts developed I-II aGVHD. No MC pts develop II-IV aGVHD. MC patients were unlikely to have severe acute GVHD. MC was associated with an increased risk of chronic GVHD, mostly were DLI derived Patients receiving stem cells from cord blood of matched sibling donors had a high risk of MC.MC incidence of stem cell source from peripheral blood(PB), bone marrow(BM), cord blood (CB)were 10.6%, 10%, 34.2% respectively.(P=0.000, Figure 4). Unrelated donors had a lower risk of MC than sibling donors. Incidence of MC from unrelated donors was 9.5% vs. 16.1% from sibling donors (P=0.007, Figure 5) Intravenous Thiotepa (TT) in combination with Busulfan (Bu) , cyclophosphamide (Cy) anti-thymocyte globulin(ATG) on HSCT could reduce the risk of MC. The corresponding incidence of MC in Cy+Bu+Flu+TT+ATG, Cy+Bu+Flu+ATG, Cy+Bu+Flu conditioning regimen were 9.2%,15.9%,40.9% resepectively(P=0.000, Figure 6). There was also a significant difference in chimerism based on donor-recipient gender pairing (P = 0.041): male grafts into male patients having the greatest risk of MC and female grafts into female patients having the least. Patients who under 9 years old had a higher risk of MC than that of pts&amp;gt;9 years old (P=0.018, Figure 7), Summary: Our results show that patients who presented mixed chimerism showed a similar post-transplant outcome in OS and TFS but was associated with higher risk of graft failue.Patients receiving stem cells from CB had a high risk of MC than from PBSC. Reduced nonmyeloablative approach capable of achieving allogeneic mixed hematopoietic chimerism. Our data suggests that Cy+Bu+Flu+TT+ATG is a preferred conditioning regimenfor TM patients could reduce the risk of mixed chimerism. Disclosures No relevant conflicts of interest to declare.

Incidence and Therapeutic Implications of Germline TP53 Mutations in Hypodiploid Childhood Acute Lymphoblastic Leukemia: A Retrospective Analysis of the Italian Cohort

Background. Hypodiploid Acute Lymphoblastic Leukemia (ALL) is a rare subtype of childhood ALL known to be associated with a poor prognosis. Currently, intensive chemotherapy and haematopoietic stem cell transplantation are recommended as the main therapeutic strategy for these patients. Previous studies showed that low-hypodiploid ALL frequently carry TP53 variants, the majority of which are germline mutations. This finding suggests that hypodiploid ALL may be a manifestation of underlying Li-Fraumeni syndrome, with an associated high risk for secondary tumors. We analyzed TP53 variants in the Italian cohort of hypodiploid pediatric ALL patients diagnosed between 2000 and 2019, to explore frequency and characteristics, as well as the potential role of germline variants in the therapeutic strategy. Patients were treated according to the AIEOP-BFM ALL2000 (n=16), ALL2009 (n=16) and ALL2017 (n=8) protocols. Methods. We performed a targeted Next Generation Sequencing (NGS) Nextera Flex DNA panel of 40 genes, including TP53, in a retrospective series of hypodiploid paediatric ALL Italian patients enrolled in four nationwide frontline protocols. Ploidy was defined based on DNA index (DNAi) and/or cytogenetics/FISH, and cases with DNAi&amp;lt;0.8 were included in this study. Only TP53 variants with VF &amp;gt;5% and coverage 500X were considered. Bioinformatics analysis has been carried out by Sophia DDM software. NGS has been performed both in disease (hematopoietic) and germline (remission or buccal brush) tissues samples. Results. Nineteen TP53 variants were observed in 20/40 (50%) hypodiploid ALL patients, with 19/20 being low-hypodiploid ALL cases (DNAi between 0,6 and 0,8); 13/19 TP53 variants were known to be pathogenic whereas 6/19 were classified as Variant of Unknown Significance (VUS). Considering the VUS variants, 3/6 were missense, 1/6 frameshift and 2/6 in-frame ins/del. Notably, 13 patients out of 20 (65%) were found to carry a germline variant, while 5 patients presented a somatic variant; in 2 cases the remission sample was not available, but the VF&amp;lt;20% was indicative of a somatic variant. Among the germline variants, 1 was found to be a germline mosaicism, presenting a nonsense pathogenic TP53 variant both in remission (VF 10%) and buccal brush sample at remission (VF 8.5%). 16/19 variants reside in the p53 core DNA binding domain, known to be a fundamental site that mediates the transcription of p53 regulated genes, where most of the pathogenic mutations in cancer cells occur. The 3 variants outside the DNA binding domain were 1 nonsense, 1 frameshift and 1 missense, and were localized in the nuclear localization signal region (NLS) or in the oligomerization domain (OD). Considering the 32 patients with at least 5 years of follow-up, EFS was not significantly different between TP53 wild type (47.1% ± 12.1) vs TP53 variant (51.9% ± 17,8) subgroups. According to MRD stratification criteria, the patients carrying a TP53 variant were classified as medium risk in 14/20, standard risk in 5/20 and HR in 1 case, not statistically different from TP53 wild type. Collection of data on secondary neoplasms in patients and their relatives in ongoing. Conclusion. Our data represent the largest low hypodiploid patient cohort tested so far, confirming the high frequency of deleterious TP53 mutations. Mutational testing of TP53 in patients with hypodiploid ALL is warranted, in order to ensure a proper genetic counseling for patients with germline mutations and their families, with tailored clinical surveillance (according to Li-Fraumeni Syndrome guidelines). The best therapeutic regimen for hypodiploid patients is still a matter of debate, with MRD at the end of induction and TP53 germline mutations potentially indicating a highest relevance in the indication to hematopoietic stem cell transplantation. Chemotherapy-only treatment could be indicated for MRD-low patients and HSCT for MRD-High, potentially considering a reduced conditioning regimen for TP53 mutated cases. Disclosures Locatelli: Amgen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bellicum Pharmaceutical: Membership on an entity's Board of Directors or advisory committees; Miltenyi: Speakers Bureau; Medac: Speakers Bureau; Jazz Pharmaceeutical: Speakers Bureau. Rizzari:Sobi: Consultancy, Other: Advisory Board.

Use of Ex Vivo Graft Manipulation and Posttransplant Cyclophosphamide Result in Low GvHD Rates and Acceptable Engraftment after RIC Regimens in Pediatric Mismatched SCT

Introduction: There are currently two strategies to prevent Graft-versus-Host Diseases (GvHD) mainly applied in haploidentical transplantation. One is ex-vivo T-cell depletion of TcRa/b T-cells and the other is the T-replete approach, in which the donor T-cells remain in the graft and are tolerized in vivo by post-transplant cyclophosphamide (pCy). The ex-vivo depletion strategy does not require post-transplant immune suppression for GvHD prevention, whereas T-replete transplants require intensive immune suppression. A major obstacle for engraftment is the persistence of patients' T-cells despite intensive and myeloablative condition regimens, thus probably leading to rejection of the graft. We hypothesized that both methods could be combined in a setting of Reduced Conditioning setting (RIC). The ex-vivo T-cell depletion would allow to omit post-transplant immunosuppression and the pCy given at day +3 and +4 could induce in-vivo tolerance of the residual patients' T-cells not eliminated by RIC. Therefore, we applied this strategy in patients who were not eligible based on their poor clinical condition and who were considered to endure only a very reduced conditioning regimen. Results: We report on a cohort of 6 pediatric patients who were not eligible for myeloablative condition regimens due to preexisting organ dysfunctions (lungs, gut or liver) but were in urgent need of an SCT from matched unrelated (n=2) or haploidentical family donors (n=4). Diagnoses were: immune deficiencies (n =4; CARMIL 2, STAT 1, ICF 2, 1 not classified), relapsed metastatic ependymoma, refractory Burkitt´s lymphoma. All patients received a non-myeloablative conditioning regimen (ATG (Thymoglobin) 2mg/kg d-9 to d-7, fludarabine 30mg/m² d-6 to d-2, TBI 4Gy d-1, cyclophosphamide 50mg/kg d+3, d+4; adapted from Aversa, Reisner et al. Blood Adv. 2017). One patient additionally received thiotepa 2x5mg/kg on d-2. The CliniMACS® device was used for TCRab/CD19 depletion of peripheral stem cells; a median number of 14x10E6 CD34+ cells/kg bw with 6.4x10E3/kg bw residual TCRa/b T-cells was infused without any further posttransplant immune suppression. Four patients received a single add back of CD45 RA depleted donor T-cells at d+7. Dosages of 1x10E5/kg, 1x10E6/kg or 5x10E6/kg were administered. Two patients received an additional T-cell depleted stem cell boost after application of pCy Engraftment occurred in 4/6 patients; 2 patients rejected their haploidentical grafts and showed complete autologous reconstitution. Median time to reach ANC&gt;500 was 19 days (range 15-23). Four patients had no signs of GvHD; 1 patient had grade I; the patient who had received the highest dose of CD45RA depleted DLI developed grade III but could be treated successfully. No cGvHD occurred. Immune recovery was rapid. Median numbers of CD3+ T-cells, CD3/CD4+ T-cells, CD19+ B cells and CD56+ NK cells at d30 and d100 were 120/µl, 9/µl, 0/µl, 140/µl and 205/µl, 60/µl, 67/µl and 206/µl, respectively. 3 patients are alive and well with a median follow up of 824 days (43-1100). Last observed donor chimerisms were 95-100%. Causes of death in 3 other patients were: MAS/sepsis (STAT 1 deficiency, d 264) and progression in both patients with malignancies (d282 and d73). The patient with relapsed ependymoma showed a transient tumor regression for 3 months posttransplant whereas the patient with refractory Burkitt´s lymphoma had only a short response for 4 weeks. Conclusions: The combination of TCRa/b depletion and pCy allowed to use a very reduced conditioning regimen which could be administered in pediatric patients even with preexisting significant organ dysfunctions without severe side effects. GvHD could be effectively prevented (except in one patient who received a high number of DLI) together with an acceptable engraftment rate provided by post cy. Thus, this method might offer the possibility to establish a donor-derived hematopoiesis without using pharmacological myeloablation and with minimal toxicity and might be the basis for future strategies to further reduce the conditioning regimen, especially for patients with non-malignant diseases. Disclosures No relevant conflicts of interest to declare.

A Real-Life Study of Autologous Stem-Cell Transplantation in Patients with Multiple Myeloma Older Than 65 Years in a Latin American Country

Introduction: The majority of patients with Multiple Myeloma (MM) are elderly (≥ 65 years). High dose chemotherapy followed by autologous stem cell transplantation (HDCT-ASCT) is the standard of care in patients younger than 65 years. This treatment option should be individualized in elderly patients, mainly due to increased toxicity. Goals: To assess the safety and outcome of HDCT-ASCT in real life in patients ≥ 65 years of age with a diagnosis of MM. Material and methods: Retrospective cohort study of consecutive patients with a diagnosis of MM according to the IMWG 2014 criteria from a single academic center in Argentina, undergoing their first HDTC-ASCT during the period 2008- 2018. Patients with plasma cell leukemia or light chain amyloidosis were excluded. Data was extracted from medical records and collected in an standardized case report form. Consolidation treatment and maintenance were used according to the standard of institutional care at the time of the ASCT. The patients ≥ 65 years old at HDCT-ASCT were compared with those below &lt; 65 years treated in the same period. Response were categorized as: complete remission (CR), very good partial remission plus partial remission (VGPR/PR) and stable disease plus progression disease (EE/PD). Overall response rate (ORR) included CR, VGPR and PR. Overall survival (OS) and progression free survival (PFS) were calculated using the Kaplan and Meier method and compared using log-rank test. For survival, the risk ratio (HR) was calculated according to the multivariate Cox regression model. Transplant-related mortality (TRM) was analyzed with cumulative incidence curves of competitive risks. Values of p &lt;0.05 were considered statistically significant. Results: A total of 221 patients were included in the analysis: 50 patients ≥65 years (7 out of 50 &gt; 70 years) and 171 patients &lt;65 years. Patient's demographics and disease characteristics by age group are summarized in Table 1. Reduced conditioning regimen (melphalan 140 mg/m2) was used in 5% of younger patients and 24% of older patients, p &lt;0.001. In the safety analysis, no significant differences were found between the two groups in the median days of hospitalization, duration of days of neutropenia or thrombocytopenia and life support measures during the period of hospitalization for the transplant (Table 2). The TRM was 2.7% at 100 days (95% CI 1.1-5.5); there was no difference between patients ≥ 65 years and &lt;65 years (2% vs. 2.9%, respectively; p = 0.928). CR before transplant was 22% and 24% and at day 100 after ASCT 44% and 37% in patients ≥65 years and &lt;65 years, respectively. For VGPR, corresponding rate were 64% and 67% before transplant and 79% and 77% at day 100 after ASCT in patients ≥65 years and &lt;65 years, respectively. ASCT increased CR rate in both groups (p=0.050 and p=0.024, respectively). After a median follow-up of 42.5 months (IQR 21-71.5), 3-year PFS was 56.2% (95% CI 39.8-70%) in ≥65 years and 58.2% (95% CI 49.6-65.9) in &lt;65 years; (p = 0.86). The OS at 3 years was 78.3% (95% CI 62.1-88, 2) in ≥65 years and 79.3% (95% CI 71.6-85.1) in &lt;65 years; (p = 0.94). In the multivariate analysis including age at transplant, the quality of pre-transplant response (HR 0.08 for CR, p &lt;0.001; HR 0.16 for VGPR/PR, p = 0.003) and the use of IP (HR 0.51; p = 0.047) were associated with better OS; while the age at transplant had no impact (HR 1.06; p=0.865) (Figure 1). For PFS , including age at transplant, only the quality of pre-transplant response demonstrated statistical significance (HR 0.06 for CR, p &lt;0.001; HR 0.14 for VGPR/PR, p &lt;0.001). Additionally, post-transplant maintenance, was independently associated with better OS (HR 0.34; p=0.016) and PFS (HR 0.47; p &lt;0.001). Conclusions: Our data shows that it is feasible and safe to perform HDCT-ASCT in fit patients with multiple myeloma older than 65 years, and even in patients &gt;70 years old. Patient selection should be based on frailty and comorbidities rather than chronological age alone. This group of patients experiences survival benefits similar to young patients. Disclosures No relevant conflicts of interest to declare.

Treosulfan Metabolite (S, S-EBDM) Pharmacokinetics Influences Regimen Related Toxicity in Patients with Beta Thalassaemia Major Undergoing HSCT

A toxicity reduced conditioning regimen containing Treosulfan (Treo), Fludarabine (Flu), Thiotepa in patients with class III high risk thalassemia major (TM) has significantly improved transplant outcomes compared to the historical Busulfan/cyclophosphamide based myeloablative regimen (Mathews et al, 2013). However, complications related to mixed chimerism, rejection and regimen related toxicity remain. Analysis of Treo pharmacokinetics (PK) in TM showed significant inter individual variation but no association with HSCT outcome (Mohanan et al, 2018). This may be attributed to the fact that only the pro-drug Treo was measured and not its active metabolites. Treo, administered as a prodrug, is converted non-enzymatically to its active metabolite monoepoxide 2S, 3S-1,2-epoxybutane-3,4-diol-4-methanesulfonate (S, S-EBDM) and (2S,3S)- 1,2:3,4-diepoxybutane (S, S-DEB) that causes cytotoxicity. We have now assessed the PK of both Treo and S, S-EBDM and the factors which may influence the inter-individual variation in PK, and their impact on HSCT outcome in patients with TM. Fifty-six patients with TM undergoing HSCT between January 2016 and June 2019 with Flu/Treo based conditioning regimen (Flu 40mg/m2/day x 4 days as a 1hr infusion and Treo as 14g/m2/day x 3 days infused at 5g/hr) were included in this analysis. Selected functional polymorphisms in NAD(P)H Quinone Dehydrogenase-1 (NQO1) and Glutathione S-transferase (GST) genes that showed association with Treo PK based on our previous report (Pai et al, Abstract. Proceedings of BMT Tandem Meetings 2018) were screened. Plasma Treo and S, S-EBDM were measured using an LC-MS/MS method. Treo and S, S-EBDM PK were estimated using nonlinear mixed effects modeling via Monolix 5.0.1. The covariates tested were age, sex, body weight, BSA, serum ferritin, NQO1 3'UTR (rs10517) and GSTA1*B polymorphisms. The influence of Treo &amp; S, S-EBDM PK and polymorphisms on graft rejection, regimen related toxicities (RRT), chimerism status, overall and event-free survival were estimated using logistic regression analysis. A two-compartment model best described the PK of Treo and S, S-EBDM. Two and 11-fold inter-individual variation was observed in Treo and S, S-EBDM PK respectively. Among the covariates tested, Treo Cl decreased with age (p=0.03) while, S, S-EBDM apparent Cl increased in patients with NQO1 3'UTR variant (p=0.02) and decreased in patients with GSTA1*B variant genotype (p=0.02). Neither Treo AUC nor clearance showed association with HSCT outcome. However, high S, S-EBDM AUC (213. Vs 130 mg*hr/mL, p=0.016) and low S, S-EBDM apparent Cl (68 Vs 122 L/hr/m2, p=0.013) were significantly associated with increased incidence of sinusoidal obstruction syndrome (SOS). Also, on quartile analysis, patients with S, S-EBDM AUC &gt;210 mg*hr/mL and Treo/S, S-EBDM AUC ratio &gt;18 mg*hr/mL showed increased incidence of SOS (p=0.006 &amp; p=0.026 respectively). Multivariate analysis adjusting for known clinical risk factors also showed in addition to age, only high S, S-EBDM AUC to be significantly associated with increased incidence of SOS (p=0.013). No association between rejection or mixed chimerism and Treo/S, S-EBDM PK was observed, probably due to very low incidence of graft rejection in this cohort (4/56; 7%). Our study suggests that active metabolite S, S-EBDM influences SOS following HSCT in TM patients. It is well acknowledged that Treo to S, S-EBDM conversion is a non-enzymatic nucleophilic substitution reaction and there is a difference in the disposition of Treo and S, S-EBDM in different organs including the liver (Romanski et al, 2017). Treo metabolites exert their cytotoxic activity by both DNA-DNA and DNA-protein crosslinks in these organs. The role of Treo metabolites in exhausting essential cellular proteins like GSH and NQO1 as well as the effect of GST/NQO1 variants in influencing Treo metabolism in liver which may then impact the incidence and severity of SOS need further evaluation. Disclosures No relevant conflicts of interest to declare.

Maternal T-cell engraftment impedes with diagnosis of a SCID-ADA patient

We describe the case of a child affected by severe combined immunodeficiency (SCID) with adenosine deaminase (ADA) deficiency showing a maternal T-cell engraftment, a finding that has never been reported before. The presence of engrafted maternal T cells was misleading. Although ADA enzymatic levels were suggestive of ADA-SCID, the child did not present the classical signs of ADA deficiency; therefore, the initial diagnosis was of a conventional SCID. However, ADA toxic metabolites and molecular characterization confirmed this diagnosis. Polyethylene glycol-modified bovine (PEG) ADA therapy progressively decreased the number of maternal engrafted T cells. The child was grafted with full bone marrow from a matched unrelated donor, after a reduced conditioning regimen, and the result was the complete immunological reconstitution.

Self-Destructive Behavior among Full-Donor Blood and Marrow Grafts and the Association with Long-Term Graft Function

Self-Destructive Behavior among Full-Donor Blood and Marrow Grafts and the Association with Long-Term Graft Function

Alternative donor hematopoietic stem cell transplantation for sickle cell disease.

Most patients who could be cured of sickle cell disease (SCD) with stem cell transplantation do not have a matched sibling donor. Successful use of alternative donors, including mismatched family members, could provide a donor for almost all patients with SCD. The use of a reduced-intensity conditioning regimen may decrease late adverse effects. Ten patients with symptomatic SCD underwent CD34+ cell-selected, T-cell-depleted peripheral blood stem cell transplantation from a mismatched family member or unrelated donor. A reduced-intensity conditioning regimen including melphalan, thiotepa, fludarabine, and rabbit anti-thymocyte globulin was used. Patients were screened for a companion study for immune reconstitution that included a donor lymphocyte infusion given 30-42 days after transplant with intravenous methotrexate as graft-versus-host disease (GVHD) prophylaxis. Seven eligible patients were treated on the companion study. Nine of 10 patients are alive with a median follow-up of 49 months (range, 14-60 months). Surviving patients have stable donor hematopoietic engraftment (mean donor chimerism, 99.1% ± 0.7%). There were no sickle cell complications after transplant. Two patients had grade II-IV acute GVHD. One patient had chronic GVHD. Epstein-Barr virus-related posttransplant lymphoproliferative disorder (PTLD) occurred in 3 patients, and 1 patient died as a consequence of treatment of PTLD. Two-year overall survival was 90%, and event-free survival was 80%. A reduced-intensity conditioning regimen followed by CD34+ cell-selected, T-cell-depleted alternative donor peripheral blood stem cell transplantation achieved primary engraftment in all patients with a low incidence of GVHD, although PTLD was problematic. This trial was registered at clinicaltrials.gov as #NCT00968864.

Improved Outcome of Unrelated Cord Blood Transplantation in Children with Severe Aplastic Anemia

IntroductionHematopoietic stem cell transplantation (HSCT) from an HLA-matched related donor is a first-line treatment for children with severe aplastic anemia (SAA). HSCT from an HLA-matched unrelated donor (MUD) is indicated as a salvage treatment for non-responders to immunosuppressive therapy (IST).Because unrelated cord blood transplantation (UCBT) has been considered as an experimental therapy, information of UCBT in patients with SAA is scarce, especially in pediatric patients. We analyzed the outcomes of UCBT in children with AA registered in the Transplant Registry Unified Management Program (TRUMP) conducted by the Japanese Society for Hematopoietic Cell Transplantation.Patients and MethodsBetween 1998 and 2013, 27 patients <15 years old who underwent an UCBT as the first HSCT were registered in the TRUMP database. Patients with congenital bone marrow failure syndrome such as Fanconi anemia were excluded from the analysis. Treatment failure were defined as death by all causes, graft failure (GF) and secondary malignancy. Data collected as October 2014 were analyzed.ResultsPatients' characteristicsAmong the 27 patients, 10 patients underwent UCBT during 1998 - 2005 and 17 patients underwent UCBT during 2006 - 2013. The median age at the time of UCBT was 6 years (range, 0 - 14). The male/female ratio was 12/15. The median interval between the diagnosis of AA and CBT was 212 days (range, 39 - 2,982). Sixteen patients received antithymocyte globulin (ATG) as immunosuppressive therapy (IST) before UCBT. The median total nucleated cell number and CD34 positive cell number at cryopreservation were 3.99 x 107/kg (range, 0.09 - 16.11 x 107/kg) and 1.31 x 105/kg (range, 0.39 - 6.17 x 105/kg), respectively. Ten patients received fludarabine (FLU) + cyclophosphamide (CY) + irradiation ± ATG. Six received FLU + CY + ATG. Four received FLU + melphalan (MEL) + irradiation and the remaining 7 received other various conditioning regimens. Cyclosporine was used in 9 patients and tacrolimus was used in 17 patients for graft-versus-host disease (GVHD) prophylaxis.Transplantation outcomesNeutrophil recovery was observed in 19 patients and the median time to engraftment was 20 days. Platelets engraftment was observed in 17 patients and the median time to engraftment was 50 days. One patient experienced secondary GF. Sustained engraftment was observed in 18 patients. Grade II - IV acute GVHD, limited chronic GVHD, and extensive chronic GVHD were observed in 6 (26%), 2 (10%), and 2 patients (10%), respectively.With median follow-up times of 18 months after CBT, 19 of 27 patients were alive. Causes of death included bacterial/fungus infections in 3, veno-occulusive disease (VOD) in 2, EBV-LPD, hematologic malignancy, and secondary GF in each 1 patient.The 5-year overall and failure-free survival (OS, FFS) of all patients were 69.5±9.0% and 59.3±9.5%, respectively. The 5-year OS and FFS of 17 patients who underwent UCBT after 2006 was 93.8±6.1% and 76.0±10.5%, respectively. Primary GF was observed in 8 patients, including 3 who underwent UCBT during 2006 - 2013. Two patients, who underwent UCBT after 2006, received FLU + CY + ATG without irradiation and remaining one patient received CY + ATG + total body irradiation (TBI). We screened anti-HLA antibodies in 8 patients but none of them were positive. The conditioning regimens including ATG exhibited a significantly worse FFS than those without ATG (33.3±12.2 % vs 91.7±8.0 %, P=0.004). On the other hand, the conditioning regimens including irradiation exhibited a better FFS than those without irradiation (75.0±9.7 % vs 14.3±13.2 % , P=0.01). The 5 year FFS of FLU + MEL + irradiation regimen (n=4) and FLU + CY + irradiation regimen (n=10) was 100% and 90%±9.5%, respectively.Univariate analysis resulted in no statistical significant differences in OS and FFS in HLA disparities, total nucleated cell number and CD34 positive cell number at cryopreservation, and methods of GVHD prophylaxis. One patient developed secondary malignancy.DiscussionOur study showed that a reduced conditioning regimen with Flu, MEL/CY and low-dose irradiation may be an optimal regimen for SAA children receiving UCBT. An important finding is that ATG has no benefit in this setting. A prospective study with larger number of patients is warranted to confirm our promising results. DisclosuresKojima:SANOFI: Honoraria, Research Funding.

A 5'UTR Polymorphism in NT5E Gene Influences Outcome in Patients with Acute Myeloid Leukemia Undergoing Hematopoietic Stem Cell Transplantation with Fludarabine Based Conditioning Regimen

Allogeneic hematopoietic stem cell transplantation (Allo-SCT) with fludarabine based reduced intensity or toxicity reduced conditioning regimen with Busulfan or Melphalan (Flu/Bu; Flu/Mel) has improved HSCT outcome in patients with AML. Limited reports on the PK of Flu in patients with malignant hematological diseases undergoing Allo-SCT suggest that Flu AUC is associated with transplant related mortality (TRM) (Long-Boyle et al, 2011). We prospectively analyzed the PK and pharmacogenetics (PG) of Flu and Bu on Allo-SCT outcome in patients with AML receiving Flu/Bu or Flu/Mel based regimen.Forty-eight adult AML patients receiving Flu/Bu(targeted) (Flu 40mg/m2 /day intravenously from day-5 to -2 and intravenous Bu 130mg/m2 /day from day-5 to-2; n=27) or Flu/Mel (Flu 30mg/m2 /day intravenously from day -6 to -2 and Mel 140mg/m2 intravenously on day -1; n=21) regimen prior to Allo-SCT between January 2012 and 2015 were enrolled in this study. Peripheral blood was collected for PK analysis at serial time points and plasma was separated and analyzed the same day (for Bu TDM). Bu dose was adjusted based on the first dose PK to achieve target cumulative total AUC (22000mmoles*min). Flu plasma levels was analyzed using LC-MS/MS and the concentration was expressed as mmol/ml. Genetic polymorphisms that influence Flu and Bu PK (NT5E 5'-UTR variant rs2295890 and GSTA1*B polymorphism) were screened using pre- HSCT genomic DNA. The influence of Flu/Bu PK and PG on clinical outcome endpoints such as overall survival (OS) and event-free survival (EFS) was evaluated using cox regression analysis.The demographics of the patients is listed in the Table. There was a significant inter-individual variation in the flu clearance (1.2mL/h/m2(0.5-4.3); 8.6 fold) and AUC (46mmol*h/ml (24-101); 4.2 fold). Fludarabine AUC trended higher in Flu/Bu group when compared to Flu/Mel group (median AUC 52 vs. 43 mmol*h/ml respectively; p=0.08). Neither of the polymorphisms significantly explained the variation in Bu or Flu PK in this cohort and none of the PK parameters was associated with EFS/OS. However, patients carrying variant genotype of the NT5E 5'UTR polymorphism (rs2295890) showed significantly better OS (p=0.016) and EFS (p=0.007) (Figure) compared to those carrying wild type genotype. We have previously reported that this variant is associated with decreased Flu Clearance in patients with aplastic anemia and thalassemia receiving Flu based conditioning regimen (Mohanan et al, December 06, 2014; 124 (21): 3884; Mohanan et al, December 03, 2015; 126 (23): 3120). Although not significant, the Flu clearance was lower in the NT5E variants in this cohort as well. It can be extrapolated that patients carrying the variant genotype of the NT5E polymorphism, have decreased relapse incidence (Wild type-8; Variants-1) and hence better EFS and OS post HSCT, due to decreased clearance and increased systemic exposure to Flu. This finding need to be validated in a larger number and in patients with other disease conditions undergoing HSCT with Flu based regimen, in order to achieve the goal of personalizing conditioning regimen. [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Successful allogeneic bone marrow transplantation with reduced intensity conditioning regimen for a pediatric relapsed ALK positive anaplastic large cell lymphoma.

Pediatric anaplastic large cell lymphoma (ALCL) is a chemosensitive malignancy, but about 30% of patients experience relapse. In most of these patients, a second complete remission is obtainable with salvage chemotherapy, though relapse free survival rates are as low as 30-60%. Herein, we report a 6-year-old boy with relapsed anaplastic lymphoma kinase (ALK) positive ALCL successfully treated with vinblastine monotherapy followed by allogeneic hematopoietic stem cell transplantation (allo-HSCT), with a reduced intensity conditioning (RIC) regimen, from his father. One HLA locus from the father was mismatched. The boy had neither severe graft-versus-host disease nor transplantation related complications. He is currently well and has remained disease free for 10 months, to date, since transplantation. Allo-HSCT with a RIC regimen may be a promising treatment strategy for relapsed ALK positive ALCL based on obtaining graft-versus lymphoma effects as well as reducing transplantation-related mortality.