Abstract: Recipients of a partially T-cell–depleted (TCD) allogeneic stem cell transplantation (allo-SCT) developing reactivation of Epstein-Barr virus (EBV) with quantified viral DNA levels exceeding 1000 genome equivalents/milliliter (geq/mL) are at high risk for EBV–lymphoproliferative disease (EBV-LPD). We studied whether preemptive therapy with rituximab prevents EBV-LPD, LPD-mortality, and abrogates viral reactivation in high-risk patients. We monitored 49 recipients of a TCD allo-SCT weekly for EBV reactivation by quantitative real-time polymerase chain reaction (PCR). Preemptive therapy by a single infusion of rituximab was given to patients with viral reactivation more than or equal to 1000 geq/mL. Results were compared with an historical control group of patients retrospectively monitored for EBV reactivation at similar intervals. There were 17 prospectively monitored patients who showed EBV reactivation more than or equal to 1000 geq/mL and 15 received preemptive therapy. Median time to preemptive therapy was 113 days (range, 41-202 days) after SCT. There were 14 patients who showed complete response (CR) as characterized by prevention of EBV-LPD and complete clearance of EBV-DNA from plasma, which was achieved after a median number of 8 days (range, 1-46 days). One patient progressed to EBV-LPD despite pre-emptive therapy, but obtained CR after 2 infusions of rituximab and donor lymphocyte infusion. There were 2 patients who had already developed EBV-LPD prior to preemptive rituximab, but obtained CR following 2 rituximab infusions. Comparison of this prospectively followed series to our historical cohort with the same high-risk profile showed a reduction of EBV-LPD incidence (18% ± 9% versus 49% ± 11%, respectively) and a complete abrogation of LPD-mortality (0% versus 26% ± 10%, respectively) (P = .04) at 6 months from EBV-DNA more than or equal to 1000 geq/mL. Frequent quantitative monitoring of EBV reactivation and preemptive therapy by rituximab improves outcome in patients at high risk of EBV-LPD.

Abstract: Introduction The use of autologous haematopoietic cell transplantation (auto-HCT) in the treatment of myeloma (MM) has greatly increased over the last twenty-five years. There are, however, few large datasets detailing the overall trends in transplant use, patient selection, induction regimen, choice of mobilisation regimen, stem cell yield, response to transplant and survival. We performed a retrospective analysis of all patients who underwent first auto-HCT for MM in EBMT centres between 1993 and 2017 and analysed these trends over consecutive five-year cohorts: (1) 1993-1997, (2) 1998-2002, (3) 2003-2007, (4) 2008-2012 and (5) 2013-2017. Methods Data on patients with MM who underwent a first auto-HCT at EBMT centres between 1993 and 2017 were obtained from the EBMT registry. Med-A forms consist of registration and follow-up forms. More detailed information in captured in Med-B forms. Results A total of 103,032 patients in 568 centres in 54 countries were included in this analysis. The number of transplants increased seven-fold between the first and fifth cohorts: (1) 5,246, (2) 12,554, (3) 21,153, (4) 28,390 and (5) 35,689. The gender breakdown has been consistent over time: 58% Male, 42% Female. Over these years, the median patient age at transplant has increased significantly, as follows: (1) 54, (2) 57, (3) 58, (4) 59, and (5) 61 years. The percentage of patients 〉 65 years at transplant has also increased: (1) 3%, (2) 9%, (3) 14%, (4) 14%, and (5) 22%. Between 1993 and 1997, IgG, IgA and Light Chain (LC) MM constituted 58%, 22% and 16%, respectively. The corresponding percentages between 2013 and 2017 were 52%, 18% and 27%, respectively. Data on the choice of first induction regimen was available in 19,882 (21%) cases (Med-B forms) though only cohorts 4 (2008-2012) and 5 (2013-2017) had specific data in more than 80% of cases. The trends in the percentage use of these regimens in the two cohorts since 2008 are as follows: VTD: 11% to 32%; VCD: 5% to 20%; CTD 15% to 10%; VD: 19% to 7%; PAD 5% to 4%; VRD 2% to 3%; VAD: 8% to 3%. The CR rates pre-ASCT have improved: (1) 16% (2) 14% (3) 13% (4) 20% and (5) 21%; 〉 PR rates pre-ASCT also reveal deeper responses over time: (1) 65%, (2) 68%, (3) 70%, (4) 72%, and (5) 73%. Stem cell mobilisation regimen data was available in 19,882 (19%) cases. In these centres, the use of cyclophosphamide has steadily increased: (1) 31%, (2) 54%, (3) 63%, (4) 64%, and (5) 65%. Conversely, the use of single agent G-CSF has declined: (1) 69%, (2) 45%, (3) 36%, (4) 31%, and (5) 28%. G-CSF + Plerixafor was used in 3.5% of cases from 2008-2012 and 5% in 2013-2017. The median number of stem cells collected (CD34+cells x 10^6/kg) has gradually increased: (1) 5.1, (2) 5.2, (3) 6.3, (4) 6.6, and (5) 6.5, though the median cell dose infused has remained relatively constant: (1) 3.6, (2) 4.1, (3) 4.0, (4) 3.8, and (5) 3.8. Almost all (99%) patients received peripheral blood (PB) stem cells. The number of months from diagnosis to auto-HCT has been stable since 1998: (1) 8.9, (2) 7.7, (3) 7.4, (4) 7.4, and (5) 7.3. Finally, three-year overall survival (OS) post-transplant has risen from 65% to 81% and Progression-Free Survival (PFS) from 41% to 46% (Figure 1). Conclusions This very large dataset shows consistently increasing numbers of auto-HCT for MM in Europe over the last 25 years. Although it is still sometimes stated that 65 years is the upper age limit for auto-HCT in Europe, 22% of auto-HCT recipients in the most recent cohort were older. Analysis of MM subtypes shows an increasing rate of auto-HCT for patients with LC MM, possibly facilitated by the deeper responses which are now being achieved, overall CR rates having risen from 16% to 21% and 〉 PR rates from 65% to 73%. Most patients (59%) in the most recent cohort (2013-2017) received bortezomib-based triplet induction regimens: VTD: 32%; VCD: 20%; PAD 4%; VRD 3%. Data from a subset of centres confirm the use of cyclophosphamide-based stem cell mobilisation in two-thirds; only 5% used G-CSF + Plerixafor. The median stem cell yield has increased by a quarter. As the median cell dose infused remains unchanged, this most likely reflects increasing rates of storage for subsequent transplants. Finally, serial cohort analysis reveals rising rates of OS and PFS over the 25 years, reflecting the deeper responses achieved pre-transplant and the increasing availability of novel agents, whether in the setting of consolidation or maintenance. Figure 1 Disclosures Hayden: Alnylam: Honoraria; Amgen: Honoraria. Goldschmidt:MSD: Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; John-Hopkins University: Research Funding; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Molecular Partners: Research Funding; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Chugai: Honoraria, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive Biotechnology: Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Research Funding; Dietmar-Hopp-Stiftung: Research Funding; John-Hopkins University: Research Funding; Amgen: Consultancy, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Mundipharma: Research Funding. Blaise:Pierre Fabre medicaments: Honoraria; Molmed: Consultancy, Honoraria; Sanofi: Honoraria; Jazz Pharmaceuticals: Honoraria. Byrne:Ariad/Incyte: Honoraria, Speakers Bureau. Hulin:celgene: Consultancy, Honoraria; Janssen, AbbVie, Celgene, Amgen: Honoraria. Benjamin:Gilead: Honoraria; Takeda: Honoraria; Novartis: Honoraria; Amgen: Honoraria; Eusapharm: Consultancy; Servier: Research Funding; Allogene: Research Funding; Pfizer: Research Funding. Cook:Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; Karyopharm: Consultancy, Honoraria, Speakers Bureau; Sanofi: Consultancy, Honoraria, Speakers Bureau; Takeda: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau. Gribben:Acerta/Astra Zeneca: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding. Mayer:AOP Orphan Pharmaceuticals AG: Research Funding. Beksac:Celgene: Consultancy; Amgen: Consultancy; Janssen & Janssen: Consultancy; Takeda: Consultancy. Schönland:Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Prothena: Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Medac: Other: Travel Grant.

Abstract: Reactivation of the Epstein-Barr virus (EBV) after allogeneic stem cell transplantation (allo-SCT) may evoke a protective cellular immune response or may be complicated by the development of EBV-lymphoproliferative disease (EBV-LPD). So far, very little is known about the incidence, recurrence, and sequelae of EBV reactivation following allo-SCT. EBV reactivation was retrospectively monitored in 85 EBV-seropositive recipients of a T-cell–depleted (TCD) allo-SCT and 65 EBV-seropositive recipients of an unmanipulated allo-SCT. Viral reactivation (more than 50 EBV genome equivalents [gEq]/mL) was monitored frequently by quantitative real-time plasma polymerase chain reaction until day 180 after SCT. Probabilities of developing viral reactivation were high after both unmanipulated and TCD-allogeneic SCT (31% ± 6% versus 65% ± 7%, respectively). A high CD34+ cell number of the graft appeared as a novel significant predictor (P = . 001) for EBV reactivation. Recurrent reactivation was observed more frequently in recipients of a TCD graft, and EBV-LPD occurred only after TCD-SCT. High-risk status, TCD, and use of antithymocyte globulin were predictive for developing EBV-LPD. Plasma EBV DNA quantitatively predicted EBV-LPD. The positive and negative predictive values of a viral load of 1000 gEq/mL were, respectively, 39% and 100% after TCD. Treatment-related mortality did not differ significantly between TCD and non-TCD transplants, but the incidence of chronic graft-versus-host disease was significantly less in TCD patients. It is concluded that EBV reactivation occurs frequently after TCD and unmanipulated allo-SCT, especially in recipients of grafts with high CD34+ cell counts. EBV-LPD, however, occurred only after TCD, and EBV load quantitatively predicted EBV-LPD in recipients of a TCD graft.

Abstract: Background: The antiphospholipid syndrome is characterized by the occurrence of vascular thrombosis combined with the presence of antiphospholipid antibodies (aPL) in plasma of patients. Recently it was published that aPL with lupus anticoagulant activity (LAC), caused by anti-beta2-glycoprotein I (beta2GPI) antibodies, highly correlate with a history of thrombosis. aPL-related resistance against activated protein C (APC) is one of the proposed mechanism responsible for thrombosis. We investigated a possible correlation between a beta2GPI-dependent LAC and increased APC-resistance in a population of 22 plasma samples with LAC activity. Methods: Twenty-two LAC-positive plasma samples were tested for beta2GPI-dependence (titration of cardiolipin into an APTT-based assay), increased APC-resistance, anti-beta2GPI IgG/IgM antibodies, anti-prothrombin IgG/IgM antibodies and anti-protein C IgG/IgM antibodies. In addition, a monoclonal anti-beta2GPI antibody and patient-purified IgG (both with LAC activity) were diluted in plasma with/without protein C and tested for occurrence of a beta2GPI-dependent LAC (normalization of clotting time by the addition of cardiolipin). To study aPL-induced APC-resistance in more detail, surface plasmon resonance analysis was used to investigate binding between APC and beta2GPI in the presence/absence of a mouse-derived monoclonal anti-beta2GPI antibody. Results: Eleven plasma samples that displayed a beta2GPI-dependent LAC also showed increased APC resistance. In contrast, only 1 of the 11 plasma samples with a beta2GPI-independent LAC displayed increased APC-resistance. None of the other serological parameters (antibodies against beta2-glycoprotein I, prothrombin or protein C) displayed the same association with increased APC resistance as a beta2-glycoprotein I dependent LAC. Furthermore, we found a linear correlation between the potency of a beta2GPI-dependent LAC and the level of APC-resistance. When a monoclonal anti-beta2GPI antibody and a patient-purified IgG were tested for a beta2GPI-dependent LAC, both antibodies did not display a beta2GPI-dependent LAC when diluted in protein C deficient plasma. In literature it has been proposed that direct binding of beta2GPI to APC results in a decreased activity of APC. By using surface plasmon resonance analysis, we found that beta2GPI displayed a higher affinity for coated APC in the presence of the monoclonal anti-beta2GPI antibody (4 nM) compared to beta2GPI alone (400 nM). Conclusion: The results of this study indicate that by adding cardiolipin into an APTT-based clotting assay, one can detect beta2GPI-dependent LAC based on increased resistance against APC. Increased resistance against activated protein C might result from direct binding of beta2GPI to activated protein C. In conclusion, our observations indicate a direct correlation between a major clinical symptom of APS (thrombosis), a diagnostic assay (beta2GPI-dependent LAC) and a potential mechanism responsible for thrombosis in the antiphospholipid syndrome (increased APC-resistance).

Abstract: Introduction: Although the majority of Acute Myeloid Leukemia (AML) patients achieve a complete morphological remission (CR) after induction therapy, relapse rates remain high. Molecular Minimal Residual Disease (MRD) detection by PCR-based technologies has been shown to improve relapse prediction but has been restricted to specific genetically-defined subsets of AML only. Next-Generation Sequencing (NGS) has the advantage that it allows for the assessment of a broad range of disease-related gene mutations in a single assay. Residual leukemia-specific mutations in bone marrow in morphological CR after induction therapy are supposed to represent the source of relapse. However, persistent mutations may also represent clonal hematopoiesis, analogous to age-related clonal hematopoiesis of indeterminate potential (CHIP) present in healthy individuals. It is currently unknown which and to what extent the persisting somatic mutations after induction therapy contribute to AML relapse. Here, we present a comprehensive study, detailing the value of molecular MRD detection by NGS, in a large prospective cohort of newly diagnosed AML. Methods: 482 AML patients ( & lt;65 years) were treated with 2 cycles of standard induction chemotherapy followed by consolidation in HOVON-SAKK clinical trials (www.hovon.nl). NGS was performed to detect mutations in a panel of 54 genes frequently mutated in myeloid malignancies (Illumina) at diagnosis and in bone marrow in morphological CR after completion of induction therapy. Thompson-Tau outlier testing was performed to reliably detect persisting mutations above background error rates. The primary and secondary endpoints of the study were relapse and overall survival, respectively. To establish and subsequently test our definition of NGS MRD, the cohort was split into a representative training (n=283) and validation cohort (n=147). The Cumulative Incidence of Relapse (CIR) was estimated with competing-risks regression analyses according to the method of Fine & Gray. The Cox proportional hazard model was used to calculate overall survival estimates. P-values & lt;0.05 were considered significant. Results: In 430 out of 482 (89.2%) AML patients somatic driver mutations were present at diagnosis. In 51.4% of subjects persisting mutations were detected in bone marrow in morphological CR at highly variable variant allele frequencies (VAF 0.0002-0.47), predominantly persisting in DNMT3A (78.7%), TET2 (54.2%) and ASXL1 (51.6%). These persistent mutations in DNMT3A, TET2 and ASXL1 (DTA) in the training cohort did not associate with the incidence of relapse at any VAF cut-off, indicating a stage of clonal hematopoiesis rather than a condition of impending relapse. In contrast, in the subset of AML patients with persisting DTA mutations, a significant correlation with relapse was observed when any other persistent non-DTA mutation was considered (training cohort: 5-years CIR 76.4% vs. 39.4%; p=0.002). In the training cohort NGS MRD, as defined by persistent non-DTA mutations, was found to be highly associated with the risk of relapse (SHR:1.85 [95%CI 1.27-2.70]; p=0.001), which was confirmed in the validation set (SHR:2.81 [95%CI 1.64-4.79] ; p & lt;0.001) (Fig. 1). In fact, NGS MRD was significantly associated with CIR when the training and validation series were combined (5-years CIR 58.3% versus 33.9% (p & lt;0.001)) (Fig. 2). In addition, NGS MRD predicted for reduced survival in both cohorts (training: HR:1.64 [95%CI 1.12-2.42]; p=0.012 and validation: HR:3.08 [95%CI 1.87-5.08] ; p & lt;0.001). Finally, multivariable analysis including the data of all 430 AML patients, with adjustment for age, WBC, ELN2017 risk and number of induction cycles needed to achieve CR, revealed that NGS MRD expresses profound independent prognostic significance for relapse (SHR:1.89 [95%CI:1.34-2.65]; p & lt;0.001) and overall survival (HR:1.64 [95%CI:1.18-2.27]; p=0.003). In sensitivity analysis with time-dependent correction for allogeneic stem cell transplantation NGS MRD remained highly prognostic for relapse and survival. Conclusions: In an unprecedentedly large prospective study including training and validation cohorts, targeted NGS MRD detection is established as a powerful and independent predictor for relapse and survival. NGS MRD is applicable in virtually all newly diagnosed adults with AML while persistent CHIP-related mutations lack prognostic value. Disclosures Ossenkoppele: J & J: Consultancy, Honoraria; Celgene: Honoraria, Research Funding; Karyopharm: Consultancy, Research Funding; Roche: Honoraria; Novartis: Research Funding.

Abstract: Background Platelet concentrates (PCs) are stored at room temperature to preserve their biological activity. To minimize the risk of bacterial outgrowth, storage time is limited to 7 days. It is well-established that prolonged storage of PCs results in modifications that result in a decreased hemostatic efficacy. This loss of platelet functionality during storage is commonly referred to as the platelet storage lesion (PSL). Typical events linked to development of the PSL are shape changes, platelet activation and loss of receptors crucial for platelet functionality. Two-dimensional (2D) differential gel electrophoresis (DIGE), isotope tagging and isotope-coded affinity tagging (ICAT) have been previously used to monitor changes in protein composition during storage. These studies have provided valuable insights into the changes associated with the PSL, however, these studies generally focused on a limited set of proteins. Aim We aimed to generate an overview of changes in the platelet proteome during storage using label free quantitative mass spectrometry. Furthermore, we employed Gene ontology (GO) enrichment analysis to identify pathways and biological processes that were linked to development of the PSL. Methods Three independently pooled PCs were stored in plasma under standard blood bank conditions for 16 days. Tryptic peptides were separated by nanoscale C18 reverse phase chromatography coupled on line to an Orbitrap Fusion Tribrid mass spectrometer. The RAW mass spectrometry files were processed with the MaxQuant computational platform. The global changes in protein level during platelet storage were assessed employing the analysis-of-variance functions of PERSEUS. Gene ontology enrichment analysis of biological processes, molecular functions and cellular compartments of the significantly different proteins was performed using the Cytoscape plug-in BiNGO. Results A total number of 2501 proteins was detected in all 3 biological replicates in at least one of the time points analyzed. The analysis showed that 18 proteins were down-regulated over time, whereas the level of 3 proteins was found to increase. CytoScape BinGo analysis of these significantly downregulated proteins revealed that the majority of this set was linked to GO-terms platelet degranulation, secretion and regulated exocytosis. This set of proteins included von Willebrand factor (VWF), serglycin (SRGN), SPARC, amyloid beta A4 protein (APP), multimerin-1 (MMRN1) and platelet factor 4 (PF4). A significant decline in these protein levels was observed at day 5 of storage, suggesting that release of α-granules is a relatively early event during platelet storage. At day 5 also a marked decline in S100A9 was observed. S100A9 has been implicated in degranulation in neutrophils, and may therefore also be linked to platelet granule release. Levels of membrane surface platelet glycoproteins such as glycoprotein Ibα did not significantly change at day 5. Only one single protein, histone H2A, was found to be consistently decreased already at two days of storage, but the significance of this finding is not clear. Upon prolonged storage (13 and 16 days) an increase in the level of α-2-macroglobulin (A2M), immunoglobulin M (IGM) and glycogenin-1 (GYG1) was observed suggesting that platelets acquire an (increased) potential to bind and/or internalize proteins from their environment. Consistent with this notion we also detected significant levels of several serine protease inhibitors, although levels of these proteins did not change upon storage. Conclusions Overall, our findings highlight dynamic changes in protein composition of platelets during storage. Our data provide evidence for sustained release of α-granules over time which becomes significant at day 5. Our data also suggest that during storage, platelets can bind or ingest proteins from their environment which may have impact on the hemostatic properties of stored platelets. Disclosures Leebeek: CSL Behring: Membership on an entity's Board of Directors or advisory committees, Research Funding; Baxalta: Consultancy, Membership on an entity's Board of Directors or advisory committees; Dutch Hemphilia Foundation: Research Funding.

Abstract: Abstract 3464 Introduction: Monitoring hematopoietic chimerism following allogeneic hematopoietic stem cell transplantation (alloSCT) after non-myeloablative (NMA) conditioning is commonly used to document engraftment. While mixed chimerism (MC) is frequently observed after NMA alloSCT, it occurs only rarely after myeloablative (MA) alloSCT. Persistent mixed chimerism is generally considered a risk factor for both relapse and rejection of the donor graft, irrespective of the type of conditioning regimen. However, it is still unknown to what extent mixed chimerism quantitatively predicts for relapse and whether patients at high risk for relapse can accurately be identified by assaying chimerism in either blood, marrow, and/or T cells. Therefore, we prospectively evaluated the establishment of complete and mixed chimerism in blood, marrow, and CD3+ selected T cells at 3, 6 and 12 months following alloSCT to investigate the predictive value of mixed chimerism in either subset for relapse. Methods: The study cohort included 152 recipients of an alloSCT, performed between October 2005 and December 2009 because of hematological malignancies (AML: n=61, ALL: n=25, NHL: n=18, Myeloma: n=15, CML: n=5, CLL: n=18, MDS: n=6, MPN: n=4). Median age was 50 years (range 17–67). Seventy-eight patients received a sibling donor transplant, 74 a transplant from a matched related donor. MA and NMA conditioning consisted of Cyclophosphamide/TBI 1200 cGy (n=45) and Fludarabine/TBI 200cGy (n=107), respectively. Chimerism tests were routinely performed in bone marrow (BM), peripheral blood (PB) and CD3 selected samples at 3, 6 and 12 months post transplant, using PCR and electrophoresis of variable number of tandem repeats or fluorescent in-situ hybridization by sex-chromosome specific probes. Complete (donor) chimerism (CC) was defined as 〉 95% donor hematopoiesis, MC as ≤95% donor hematopoiesis. The cumulative incidence of disease recurrence/progression and progression free survival by chimerism status was evaluated as from 3, 6 and 12 months post transplant and adjusted for type of conditioning, donor type, patient/donor sexe and age. Results: MC appeared very rare after MA conditioning, but was more frequently observed after NMA alloSCT with incidences of BM-MC of 28, 22 and 9% at the 3, 6 and 12 month timepoints, respectively. MC in BM as well as PB samples at 6 and 12 months post transplant was highly predictive for disease recurrence/progression, both after univariate and multivariate analyses (BM: hazard ratio (HR) at 6 months: 3.52 (1.30-9.53 95% confidence interval (CI)), p-value 0.013; at 12 months: 5.42 (1.17-25.13 95%CI), p-value 0.031). The probability to develop a relapse increased to 40% in time if MC was detected at 6 months following transplantation, as compared to 15% in the CC group. MC detected at 12 months resulted in a relapse incidence of ≥50% (Figure 1). Moreover, MC at these timepoints also predicted for decreased progression free survival (BM: HR at 6 months: 2.35 (1.04-5.27 95%CI), p-value 0.039; at 12 months: 9.36 (2.94-29.92 95%CI), p-value 0.000). Chimerism results in CD3+ selected T cell fractions did not show a significant association with relapse/progression or progression free survival. Conclusion: These results show that patients with MC at 6 and 12 months post transplant in either BM or PB are at a 3 to 9 fold higher risk of disease recurrence/progression. T cell chimerism appeared not associated with relapse, which may be explained by a significant different and protracted pattern of kinetics after transplantation as compared to kinetics of PB and BM chimerism, thereby identifying different subgroups of patients. Collectively, this study highlights the need to rapidly establish complete donor chimerism both after MA and NMA alloSCT. The preferred medical intervention in patients with MC after NMA conditioning, however, remains to be established in a prospective study. Disclosures: No relevant conflicts of interest to declare.

Abstract: Rationale Autologous stem cell transplantation for adult acutemyelogenousleukemia (AML) is a therapeutic option for good and intermediate risk patients. New compounds and new formulations in conjunction with pre andpost transplant targeted therapy may improve outcome. A recent EBMT retrospective survey investigating on Busulfan administered IV (Nagler A et al:Haematologica. 2014 ) pre autologous stem cell transplantation (ASCT) suggested that the combination of Busulfan and High dose Melphalan (BUMEL) was associated with the best overall survival. To address this question, we compared this regimen with the historical Busulfanand Cyclophosphamide (BUCY) association. Methods Eligibilitycriteria consistedof all adult patients (age 〉 18 years) with AMLautograftedin CR1, following a preparative regimen consisting of either BUCY or BUMEL, reported to the EBMT registry in the period from January 2005 to December 2013. The doses of Busulfan were either oral at 16 mg/kg over 4 days or IV at 12.8 mg/kg over 4 days. High dose Melphalan was 140mg/m². The data came from 231 centers 23 ofwhich usedboth regimens. The relationships between outcomes and patient, disease and transplant characteristics was evaluated in multivariate analyses using the Cox model. Results 1120 patients received BUCY and 436 BUMEL prior to autografting in first remission. Patients receiving BUMEL were older (median 52 years versus 50 years, p=0.01) with less good risk diseases by cytogenetics (16% versus 28%, p=0.001). They were autografted with a longer interval from CR1 to autografting (120 days versus 104 days, p=0.001) and they were more frequently in a negative minimal residual disease (MRD) status by molecular biology (89% versus 82%, p= 0.03). The nature of the pretransplant regimen interacted with the interval from diagnosis to autografting on both relapse incidence (p=0.005) and leukemia free survival (p= 0.02): the outcome post BUMEL was superior to BUCY only in patients transplanted within less than six months post diagnosis. In these patients, following BUMEL and BUCY respectively, the RI was 35%versus 50.6% (p 〈 10-3), the LFS 61.1% versus 46.2% (p 〈 10-3) and the OS 79.4% versus 64.8% (p= 0.003). There was no difference for NRM. When considering only patients autografted at the time when MRD detection was negative, the LFS at two years was 75.8% for 134 patients receiving BUMEL and 58.6% in the 371 patients receiving BUCY, with no significant difference (p= 0.1). The major cause of death in the two groups was leukemia recurrence. Conclusion We conclude that the BUMEL combination pre ASCT in AML CR1 is superior to BUCY when the transplant is performed less than 6 months after diagnosis. These registry data should be confirmed in a well designed two arm study assessing the role of ASCT in good risk and possibly intermediate -1 risk adult patients with AML. Table. p HR 95% CI NRM BUMEL vs BUCY 0.450 1.376 0.599 3.16 Age atTx/ 10years 0.001 1.064 1.025 1.10 Time from diagnosis to Transplant. 0.900 0.999 0.984 1.01 Cytogenetics :Intermediatevs good 0.610 0.709 0.191 2.63 Poor versus good 0.710 0.708 0.112 4.46 Missing 0.420 0.591 0.164 2.11 centre (frailty) 0.360 RI BUMEL vs BUCY 0.001 0.602 0.445 0.816 Age at Transplant / 10years 0.005 1.012 1.003 1.020 Time from diagnosis to Transplant: 0.720 1.000 0.996 1.004 Cytogenetics : Intermediatevs good 0.510 1.145 0.764 1.714 Poor versus good 0.031 1.799 1.055 3.067 Missingversus good 0.480 1.150 0.779 1.699 centre (frailty) 0.110 OS BUMEL vs BUCY 0.002 0.614 0.449 0.841 Age at Transplant / 10years 〈 10-4 1.025 1.014 1.036 Time from diagnosis toransplant 0.94 0.999 0.995 1.004 Intermediatevs good 0.88 1.036 0.649 1.653 Poor versus good 0.11 1.632 0.901 2.956 Missingversus good 0.81 1.058 0.672 1.665 centre (frailty) 0.29 LFS BUMEL vs BUCY 0.002 0.649 0.490 0.858 Age at Transplant / 10years 〈 10-4 1.015 1.006 1.023 Time from diagnosis to Transplant 0.740 1.000 0.996 1.004 Cytogenetics : Intermediatevs good 0.590 1.110 0.755 1.630 Poor vs good 0.046 1.679 1.008 2.796 Missingversus good 0.590 1.106 0.763 1.604 centre (frailty) 0.170 Multivariate analyses of prognostic factors in patients autografted within 6 months Figure 1. Leukemia free survival and overall survival of patients with AMLautograftedwithin 6 months from initial diagnosis, in first remission following high dose consolidation by BUMEL or BUCY in the period fromfromJanuary 2005 to December 2013 (EBMT registry). Figure 1. Leukemia free survival and overall survival of patients with AMLautograftedwithin 6 months from initial diagnosis, in first remission following high dose consolidation by BUMEL or BUCY in the period fromfromJanuary 2005 to December 2013 (EBMT registry). Disclosures Nemet: Celgene: Honoraria; Pliva: Honoraria; Amgen: Honoraria; Sanofi: Honoraria; Pfizer: Honoraria; Janssen: Honoraria. Mohty:Janssen: Honoraria; Celgene: Honoraria. Nagler:Biokine LTD: Consultancy.

Abstract: Abstract 1196 Poster Board I-218 Introduction: Allogeneic hematopoietic stem cell transplantation (alloSCT) from volunteer unrelated donors (URD) may be associated with a higher non-relapse mortality (NRM) and worse outcome as compared to alloSCT using HLA-identical sibling donors. However, many parameters next to donor type define NRM. The impact on outcome of allele-matching for HLA-A, -B, -C and -DRB1 between donor and recipient has clearly been demonstrated. The prognostic impact of the EBMT risk score, that takes into account age, stage of disease, time from diagnosis to transplantation, donor type and donor-recipient gender combination, has recently been validated in a variety of hematological malignancies including acute leukemia and myelodysplastic syndrome (MDS). We evaluated the relative prognostic value of high-resolution HLA matching and the EBMT risk score for patients with poor-risk acute leukemia and MDS who received an URD transplant. Patients and methods: Between 1987 and 2006, 327 patients (≥16y) with poor-risk acute leukemia and MDS underwent URD alloSCT in the Netherlands. Patients were in 1st complete remission (CR1, n=129), 2nd CR (CR2, n=91), beyond CR2 or not in remission (n=107). The leukemia-risk was considered to be poor if patients had adverse cytogenetics or were not in CR1. The majority of the grafts was T-cell depleted (94%). High-resolution typing of HLA-A, -B, -C, and -DRB1 alleles was available for analysis in 270 donor-recipient pairs and had in part been performed retrospectively. Results: We evaluated the impact of high-resolution matching for HLA-A, -B, -C and -DRB1 on progression free survival (PFS) and overall survival (OS). Patients who were fully matched (8/8) with their donors (n=170) hadsignificantly superior PFS (40+/-4% vs 26+/-5%, hazard ratio (HR)=0.68; 95%CI 0.50–0.92, p=0.01) and OS (39+/-4% vs 29+/-5%, HR=0.70; 95%CI 0.51-0.96, p=0.03), compared to patients with mismatched (≤7/8) donors (n=100). Superior OS in the 8/8 group appeared to be due to a lower NRM (24+/-4% vs 39+/-5%, HR=0.54; 95%CI 0.35-0.85, p=0.008), while the relapse mortality rate was identical in both groups (37+/-4% vs 32+/-5%). Patients with EBMT risk scores of 1-2 (n=71), 3 (n=77), 4 (n=76) and 5-7 (n=103) had a predicted 5 year OS of 52%, 41% (HR=1.57; 95%CI 0.98-2.52), 29% (HR=2.07; 95%CI 1.32-3.26) and 19% (HR=2.69; 95%CI 1.76-4.11), respectively (p 〈 0.001). Relapse mortality rate and NRM increased with increasing EBMT risk score. As shown in the table, the impact of allele-matching on OS was most evident in the EBMT low-risk group. EBMT low-risk (1-2) patients with 8/8 donors showed excellent 5 year OS compared to EBMT low-risk patients with ≤7/8 donors (73+/-8% vs 35+/-12%). The favorable impact of a fully matched donor was absent in patients with higher EBMT risk scores. Conclusions: Both the EBMT risk score and the degree of allele-matching independently predicted outcome after URD alloSCT. The predictive value of allele-matching was especially evident in EBMT low-risk patients, while patients with the highest EBMT risk scores ( 〉 4) had a dismal outcome, despite allele-matching. These results emphasize the importance of incorporating age, disease stage, donor-recipient gender combination and time interval from diagnosis to transplantation (EBMT risk score parameters) as well as high-resolution HLA-typing in the risk assessment prior to URD alloSCT. As excellent OS was noted in well matched EBMT low-risk patients, our data underscore the importance of an immediate search for an unrelated donor in poor-risk leukemia patients in CR1 below the age of 40, who should then receive their alloSCT as early consolidation therapy following induction chemotherapy. Disclosures: No relevant conflicts of interest to declare.

Abstract: ADAMTS13 contains complex type N-linked glycans, which contain terminal mannose, sialic acids, and fucose residues. TSP1 repeats are modified by O-fucosylation and C-mannosylation; O-fucosylation was also observed in the disintegrin domain.