Reduced-intensity Conditioning allo-HSCT Research Articles

High-dose Alemtuzumab-Cyclosporine versus Tacrolimus-Methotrexate-Sirolimus for Chronic Graft-versus-Host Disease Prevention

Chronic graft-versus-host disease (cGVHD) remains a significant problem for patients after allogeneic hematopoietic stem cell transplants (allo-HSCT). While in vivo lymphodepletion by antibodies for cGVHD prophylaxis has been explored in the myeloablative setting, its effects after reduced intensity conditioning (RIC) are not well described. Patients (n=83) with hematologic malignancies underwent targeted lymphodepletion chemotherapy followed by a RIC allo-HSCT using peripheral blood stem cells from unrelated donors. Patients were randomized to two GVHD prophylaxis arms: high-dose alemtuzumab/cyclosporine (AC, n=44) and tacrolimus/methotrexate/sirolimus (TMS, n=39) with the primary endpoint of cumulative incidence of severe cGVHD. The incidence of severe cGVHD was lower with AC vs TMS prophylaxis at 1- and 5-years (0% vs 10.3% and 4.5% vs 28.5%, overall p=0.0002), as well as any grade (p=0.003) and moderate-severe (p<0.0001) cGVHD. AC was associated with higher rates of grade III-IV infections (p=0.02) and relapse (52% vs 21%, p=0.003) with a shorter 5-year PFS (18% vs 41%, p=0.01) and no difference in 5-year GRFS, OS, or NRM. AC severely depleted naïve T-cells reconstitution, resulting in reduced TCR repertoire diversity, smaller populations of CD4 Treg and CD8 Tscm, but a higher ratio of Treg to naïve T-cells at 6 months. In summary, an alemtuzumab-based regimen successfully reduced the rate and severity of cGVHD after RIC allo-HSCT and resulted in a distinct immunomodulatory profile which may have reduced cGVHD incidence and severity. However, increased infections and relapse resulted in a lack of survival benefit after long-term follow-up. ClinicalTrials.gov identifier: NCT00520130.

Long-Term Follow-up of AML Patients Treated Intensively before the Era of Targeted Agents. a Big Data Analysis from the Harmony Collaboration

Background: Due to better understand of biology of acute myeloid leukemia (AML), in 2017 a new era of targeted therapy has began. Before that, since 1973 younger and fit patients were offered the 3+7 regimen (based on anthracyclines and cytarabine) followed by high-dose cytarabine and, generally allogeneic stem cell transplantation in first complete remission (alloHSCT). In 2008 azacytidine, a hypomethylating (HM) agent was approved in Europe for AML patients, who were not candidate for intensive therapy and alloHSCT. In 2010 the European LeukemiaNet (ELN), based on cytogenetic and molecular genetic characteristics, proposed a risk score classification to facilitate decisions, including indications for alloHSCT. In addition to these advances, improved supportive therapies over the last 25 years are thought to have lowered therapy associated mortality. Aims: We aimed to analyse changes in outcome of AML patients treated between 1997-2016 prior to the approval of novel drugs, in order to better understand important factors contributing to patient outcome that might also contribute to the efficacy novel treatment approaches. Methods: Quality controlled, Observational Medical Outcomes Partnership (OMOP) Common Data Model (CDM) harmonized data of the HARMONY alliance database coming from 100 organisations in 18 European countries were used for this study. Out of all AML records, 5359 patients diagnosed and treated with intensive regimens between 1997-2016 were identified. Patients treated with intensive regimens were identified regardless from age by the type of chemotherapy (n=4287) or by the age ≤70 (n=1072) if there was no information concerning the therapy. Patients with acute promyelocytic leukemia and those treated with targeted therapy were excluded from the analysis. Patients were categorized into 4 calendar periods: 1997-2001 (gr1), 2002-2006 (gr2), 2007-2011 (gr3) and 2012-2016 (gr4). The main outcome parameters analyzed were patient characteristics, overall survival (OS) and relapse-free survival (RFS). OS and RFS were determined using Kaplan-Meier analysis. Results: 5359 AML patients were included into the analysis: 1127 in gr1, 1294 in gr2, 1821 in gr3 and 1117 in gr4. The median follow-up of all patients was of 1.9 [0-17.6] while of those who survived of 5.8 [0-17.6] years. 46.6% of patients were female. The median age of all patients was 53 years (18-85). There were 3745 patients <60, 1229 between 60-69 and 385 ≥70 years old. There were no differences in ELN risk between groups. Intensive regimens in ≥70 years AML, were less frequent through calendar period: 12% in gr1 vs 6% in gr2 vs 6% in gr3 vs 7% in gr4. AlloHSCT was performed in first remission in 1770 (33%) patients and according to calendar period: 24.1% in gr1, 37.5% in gr2, 39% in gr3, and 27% in gr4 (p<0.001). OS significantly improved over the time: 15.5 (95CI: 13.8-17.6) in gr1 vs 26.3 (23.7-31.6) in gr2 vs 39.3 (32.5-47.1) in gr3 vs 37.8 (31.6-49.2) months in gr4 (p<0.001). The OS improvement was observed for both sexes, across all 4 calendar periods, but mostly for women: 32.4 (28.8-37.8) vs 25.0 (22.5-27.7) months (p<0.001). A significant improvement in OS across the four groups was observed in AML with alloHSCT: 33 (26-56.8) vs 45.4 (34.1-65.6) vs 63 (46-not-reached) months, with group 4 not yet reaching median survival, Fig A. Interestingly, the median age to perform alloHSCT in group 1 was of 42.1 (18 - 71), while in group 2, 3 and 4 it was 46.9 (16 - 69) vs 49.9 (17 - 75) and 53 (18 - 77) years, respectively (p=0.028), Fig B. Conclusion: Here we report the results of a large cohort of AML patients intensively treated between 1997-2016. Improvement of survival was observed for patients treated between 2007-2016 vs 1997-2007 in parallel with performing alloHSCT at more advanced age, most likely due to better supportive care and a greater proportion of reduced-intensity conditioning alloHSCT. As the majority of AML patients are diagnosed at advanced age, alloHSCT should be considered a curative treatment option. Less frequency of intensive regimens in elder AML since 2002 could be related with introduction of HM agents. Less number of alloHSCT in gr4 most likely represents a bias of our data base or could be related to better patient's selection (ELN criteria) and need to be analysed in a further study. The better improvement in OS in women could be explained by the fact that globally, including AML, women live longer than men. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Myeloablative Versus Reduced Intensity Conditioning Regimens for Allogeneic Hematopoietic Stem Cell Transplant for Acute Myeloid Leukemia and Myelodysplastic Syndrome: A Retrospective Analysis.

The conditioning regimens used for the allo-HSCT include either myeloablative conditioning (MAC) or reduced intensity conditioning (RIC) regimens based on the age, performance status and co-morbidities. Studies comparing the survival outcomes of RIC and MAC allo-HSCT in AML and MDS patients have reported contradictory results. We therefore retrospectively analyzed our data of AML and MDS patients who received MAC and RIC allo-HSCT at our center and compared the long term outcome of the two conditioning regimens. One hundred twenty six consecutive patients were evaluated, 32 (25.4%) underwent MAC allo-HSCT and 94 (74.6%) underwent RIC allo-HSCT. The most common MAC regimen used was busulfan plus cyclophosphamide and the most common RIC regimen used was fludarabine plus melphalan. The median age was higher in RIC group (44years, range 4-75years) compared to MAC group (31 yrs, range 6-51 yrs, p = 0.001). There was no significant difference in terms of overall survival (p = 0.498), relapse-free survival (p = 0.791) and non-relapse mortality (p = 0.366) between the two groups. In multivariate analysis, only chronic graft-versus-host disease resulted in decreased risk of relapse and improved overall survival irrespective of the conditioning regimens used.

Risk Factors for Overall Survival in Children with High Risk Acute Myeloid Leukemia (HR AML) after Allogeneic Hematopoietic Stem Cell Transplantation (allo-HSCT) with Different Intensity of Conditioning Regimens

Background: Traditionally, children with AML undergo аllo-HSCT with myeloablative conditioning (MAC). It is known that MAC is associated with significant transplant-related morbidity and mortality. Reduced-intensity conditioning (RIC) is used in patients not eligible for conventional conditioning therapy due to poor performance status and severe toxic complications after previous chemotherapy. RIC is a well-established treatment strategy in adult patients with comorbidities. But there is no conclusive evidence to support efficacy of RIC allo-HSCT in children suffering from different malignant diseases including AML. The aim: To compare efficacy of different intensity conditioning regimens in children with high risk (HR) AML (according to AML-BFM protocols 1998 and 2004) and to identify factors which have a prognostic significance for overall survival (OS). Patients and methods: Retrospective analysis was performed in 192 patients (pts) with AML (median age of 10 years (0.5-18 y.o.), who received allo-HSCT at R.M. Gorbacheva Research Institute between 08/2000 and 09/2019. MAC (busulfan- or treosulfan-based) were used in 109 pts: 1st CR - 46 pts (MRD+ n=11), 2nd CR - 18 pts, 3rd CR - 1 pt, relapse - 44 pts. Allo-HSCT with RIC were performed in 83 pts: 1st CR - 32 pts (MRD+ n=13), 2nd CR -19 pts, 3rd CR - 4 pts, relapse -28 pts (p=0,674). RIC consisted of fludarabine (30 mg/m2/d x 5 days) + melphalan (70 mg/m2/d x 2 days) or fludarabine (30 mg/m2/d x 5 days) + busulfan (4 mg/kg/d x 2 days). Indication for RIC allo-HSCT was poor performance status (Lansky/Karnofsky score ≤70%), or organ dysfunction due to previous therapy, or infectious complications at the moment of allo-HSCT. Allo-HSCT from matched related donor was performed in 30 pts (16%), from matched unrelated donor - in 98 pts (51%), haploidentical - in 64 pts (33%) and the donor distribution was not different between groups (p=0,878). Post-transplant Cy was included in GVHD prophylaxis regimens in 102 pts (53%). OS were estimated using Kaplan-Meier curves. Univariate analyses were performed using the log rank test for OS, Grey test for cumulative incidences. Multivariate analyses were performed using the Cox proportional-hazard model. Results: Median follow-up was 5 years for МАС, 4.5 years for RIC. In both groups the median time to neutrophil engraftment &amp;gt;=0,5x109/l was D+16 (range D+8-52). Engraftment was observed in 67 pts (81%) after RIC and 94 pts (86%) after MAC (p=0,231). OS after RIC allo-HSCT in the 1st CR was 76% and after MAC - 68% (p=0,014), in 2nd CR 50% after RIC and 54% after MAC (p=0,058), in advanced disease 14% after RIC and 16% after MAC (p=0,394). The transplant-related mortality rate was 19% after RIC and 22% after MAC (p=0,546). Risk of relapse was 28% after RIC and 26% after MAC (p=0,456). Factors influencing OS after MAC were: 1) Remission status at the moment of allo-HSCT (р=0.001); 2) Presence of aGVHD grade I-II (р=0,005); 3) Relapse or MRD+ status after allo-HSCT (р=0.012); 4) Lansky score &amp;gt;70% (р=0,024). Factors influencing OS after RIC were: 1) Remission status at the moment of allo-HSCT (1st remission) (p=0,001); 2) Lansky score &amp;gt;70% (р=0,004). Conclusion: The effectiveness of RIC and MAC is comparable in children with HR AML, but RIC demonstrated better results in 1st CR. The presence of I-II grade aGVHD had positive effect in MAC. Factors influencing OS in both groups were disease status at the moment of allo-HSCT and performance status before allo-HSCT The use of RIC can be effective in patients, especially those who have undergone allo-HSCT in the 1st remission, while minimizing regimen-related toxicity in children who have undergone previous intensive treatment. Multicenter studies are warranted, especially for patients in the first CR, where long-term complications are of most importance. Disclosures No relevant conflicts of interest to declare.

Quality of Life following Allogeneic Stem Cell Transplantation for Patients Age >60 Years with Acute Myelogenous Leukemia.

This study of patients with acute myelogenous leukemia (AML) age ≥60 years analyzed the association between patients' performance indices-Hematopoietic Stem Cell Transplantation Comorbidity Index (HCT-CI), Karnofsky Performance Score (KPS), and European Society for Blood and Marrow Transplantation (EBMT) risk score-before undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT) and quality of life (QoL), quantified using the Functional Assessment of Cancer Therapy-Bone Marrow Transplant Scale (FACT-BMT), in the first year after allo-HSCT. Over a period of 7 years, 48 evaluable patients underwent reduced-intensity conditioning allo-HSCT. The median patient age was 65 years (range, 60 to 74 years), with 2-year and 5-year overall survival (OS) of 65.8% and 52.3%, respectively. A significant improvement across all QoL scores was observed over the 12 months post-HSCT. An HCT-CI of 0 was associated with improved general QoL (FACT-G) score at 6 months compared with patients with an HCT-CI of 1 to 2 (P= .032). At 12 months post-HSCT, a pretransplantation HCT-CI ≥3 was correlated with lower QoL scores across the domains (symptom-related QoL [FACT-TOI], P= .036; FACT-G, P= .05; BMT-related QoL [FACT-BMT], P= .036). A pretransplantation KPS score of 100 versus 80 to 90 was predictive of improved QoL at 6 months post-HSCT (FACT-TOI, P=.009; FACT-G, P= .001; FACT-BMT, P= .002) but not at 1 year post-HSCT. We demonstrate that KPS and HCT-CI can predict QoL in the early post-transplantation period, with a favorable overall survival in a selected cohort of AML patients age ≥60 years.

Dual T-Cell Depletion with a Very Low Dose of ATG and Ptcy Provides an Effective Control of Acute Gvhd in PBSC RIC Allo-HSCT

Introduction As has been described by Dr. Viswabandya et al, the combination of anti-thymoglobulin (ATG), post-transplant cyclophosphamide (PTCy) and cyclosporine (CsA) provides an effective control of graft-versus host disease (GVHD) in peripheral blood (PB) allo-HSCT. We aim to report our experience in reduced intensity conditioning (RIC) allo-HSCT using a novel GVHD prophylaxis composed by a very low dose of ATG, PTCy and CsA for GVHD prophylaxis. Patients and methods Between May 2018 and April 2019, 106 adult patients underwent RIC allo-HSCT with the present GVHD prophylaxis. All these recipients were included in the study. RIC regimen was composed by fludarabine, busulfan, and 200cGy of total body irradiation. For GVHD prophylaxis all recipients received a total dose of 2mg/kg of rabbit-ATG on day -3 (0.5mg/kg) and -2 (1.5mg/kg), PTCy 50mg/m2/day on day +3 and +4, and CsA since day +5. Data was collected retrospectively and updated on July 2019. The median follow-up was 7.6 months (range: 0.4-14.6) and survival percentages were calculated at 6 months. The cum.Inc of GVHD was assessed accounting relapse and death as competing events. Results The main baseline and post-transplant information is summarized in the Table 1 and 2. The cum.Inc of grade II-IV and III-IV acute GVHD at day +100 was 19% and 7.7%. The cum.Inc of grade II- IV was not significantly affected by donor type (P=0.787). However, the cum.Inc of grade III-IV was significantly higher in those recipients who received haploidentical or 9/10 matched unrelated donor (MUD) grafts (p=0.048). Rates of CMV and EBV reactivation were respectively 62.3% and 68.9%. No patients were diagnosed with CMV disease. Biopsy proven post-transplant lymphoproliferative disorder was diagnosed in only 1 recipient and successfully resolved after rituximab. Thirty-two (30.2%) recipients died and 16 (15.1%) relapsed during the follow-up. Main causes of death were relapse 13 (12.3%) and infection 6 (5.7%). The main outcome information is reported in the Table 2 and Plot 1 and 2. Those recipients who received grafts from matched related and unrelated donors had a significant better non-relapse mortality (NRM) (P=0.001), overall survival (OS) (P=0.02), relapse-free survival (RFS) (P=0.03) and GVHD-free/RFS (P=0.006). Table 3 shows the impact of risk factors in transplant outcomes. Those recipients with an HCT-CI score ≥3 had a significant worse OS (HR 2.5; P=0.024) and RFS (HR 2.5; P=0034). Those recipients who received grafts from 9/10 MUD and haploidentical donors had a significant worse RFS (HR 2.1; P=0.049). Disease risk index was not a significant risk factor for OS or RFS. Lastly, those recipients who received grafts from haploidentical donors had a significant worse GRFRS (HR 2.9; P=0.04). Conclusion The dose of ATG for GVHD prophylaxis is not well established. The combination of ATG (2mg/kg), PTCy, and CsA is safe and provides an effective acute GVHD prophylaxis in PB RIC allo-HSCT. Further investigations are required to analyze the effect of this prophylaxis in chronic GVHD to better state long-term outcome conclusions and to improve post-transplant outcomes in those recipients who received grafts from mismatched donor sources (haploidentical and 9/10 matched unrelated donors). Disclosures Michelis: CSL Behring: Other: Financial Support. Mattsson:Celgene: Honoraria; Therakos: Honoraria; Gilead: Honoraria.

Allogeneic Hematopoietic Stem Cell Transplantation (allo-HSCT) with Different Intensity Conditioning Regimens in Children with Very High Risk Acute Lymphoblastic Leukemia (VHR ALL): A Single-Center Experience

Background: Allo-HSCT with myeloablative conditioning (MAC) has traditionally been performed in patients with ALL and has been associated with significant transplant-related morbidity and mortality. Reduced-intensity conditioning (RIC) is used in patients not eligible for conventional conditioning therapy due to poor performance status and severe toxic complications after previous chemotherapy. RIC is a well-established treatment strategy in adult patients with comorbidities or in elderly patients. In contrast to the adults, the RIC pediatric experience is still sparse. The aim: to compare efficacy of reduced intensity conditioning (RIC) and myeloablative conditioning (MAC) for allo-HSCT in children suffering from very high risk (VHR) ALL. Patients and methods: This was a retrospective analysis performed in 233 patients (pts) with ALL (age - from 4 month till 18 y.o. (mediana 11 y.o.)), who received allo-HSCT at R.M. Gorbacheva Memorial Institute of Children Oncology, Hematology and Transplantation between 12/2000 and 12/2017. MAC (busulfan or treosulphan containing) was used in 159 pts: 1st CR - 26 pts, 2nd CR -57 pts, 3rd or 4th CR 23 - pts, relapse -53 pts. Allo-HSCT with RIC was performed in 74 pts: 1st CR - 14 pts, 2nd CR -29 pts, 3rd or 4th CR - 12 pts, relapse -20 pts. RIC consisted of fludarabine (30 mg/m2/d x 5 days) + melfalan (70 mg/m2/d x 2 days) or fludarabine (30 mg/m2/d x 5 days) + busulfan (4 mg/kg/d x 2 days). The disease status was not different between groups (p=0.674) Indication for RIC allo-HSCT was poor performance status (Lanskoy/Karnovsky&lt;70%), organ dysfunction due to previous therapy or infectioous complications at the moment of allo-HSCT. Allo-HSCT from matched related donor was performed in 41 pts, from matched unrelated donor - in 131 pts, haploidentical - in 61 pts. Post-transplant Cy was included in GVHD prophylaxis regimens in 102 pts (44%). Results: Median follow-up was 5 years for МАС, 4.5 years for RIC. In both groups the median time to neutrophil engraftment &gt;=0,5x109/l was D+18 (range D+8-48). Transplant engraftment was observed in 64 pts (86%) after RIC and 150 pts (93%) after MAC (p=0,224). OS pts after RIC allo-HSCT performed in 1 CR 70% and after MAC - 85% (p=0,043), in 2 CR 56% after RIC and 49% after MAC (p=0,436), in 3 or 4 CR 34% after RIC and 25% after MAC (p=0,394). OS in patients with active disease was 16% in RIC-group and 18% in MAC-group (p=0,432). The transplant-related mortality rate was 18% after RIC and 20% after MAC (p=0,40). Risk of relapse was 37% after RIC and 42% after MAC (p=0,39). Acute GVHD II-IVgr developed in 32% pts after RIC and 33% after MAC (p=0,883), early infections were diagnosed in 63% in RIC-group, and 59% in MAC-group (p=0,356). Early toxic complications were observed (CTC): mucositis III-IV gr in 13% pts after RIC and in 54% pts after MAC (p=0,001), nephrotoxicity in 7% pts and in 21% pts (p=0,042), hepatitis gr II-III in 24% pts and in 57% pts, respectively (p=0,034), neurological complications in 22% pts and 42% pts, resp. (p=0,046). Conclusion: RIC allo-HSCT of VHR ALL in 2,3 or 4 CR pts ≤ 18 y.o. is effective and comparable with MAC allo-HSCT. Early toxic complications after RIC were less frequent. Possibly, the use of RIC can maintain efficacy while minimizing regimen-related toxicity in children who have undergone previous intensive treatment. Disclosures Moiseev: Pfizer: Other: Travel grants; BMS: Other: Travel grants; MSD: Other: Travel grants; Novartis: Consultancy, Honoraria, Other: Travel grants, Speakers Bureau; Celgene: Consultancy, Other: Travel grants; Takeda: Other: Travel grants.

Largest Single Center Experience Using Dual T-Cell Depletion with ATG and Ptcy for Gvhd Prophylaxis in Peripheral Blood RIC Allo-HSCT

Introduction: Dual T-cell depletion with ATG and PTCy combined with cyclosporine (CsA) in peripheral blood (PB) reduced intensity conditioning (RIC) allo-HSCT results in an impressive control of clinically relevant GVHD. We aim to share the largest and unique single center experience using this novel GVHD combination in allo-HSCT for hematological malignancies. Methods Between October 2015 and April 2019, 365 consecutive adult recipients underwent PB RIC allo-HSCT. Conditioning regimen consisted on fludarabine, busulfan and 200 cGy of total body irradiation. For GVHD prophylaxis all cases received ATG, PTCy (50mg/kg/24h x 2 doses on day +3 and +4) and CsA since day +5. Two hundred fifty-nine (71%) recipients, transplanted between 2015 and May 2018, received a total dose of 4.5mg/kg of rabbit-ATG (given on day -3,-2 and -1). In May 2018, the protocol was reviewed and refined decreasing the dose of ATG to a total of 2mg/kg (given on day -3 and -2). A total of 106 (29%) recipients received the lowered dose of ATG. Data was collected retrospectively and updated on July 2019. Cumulative incidence (Cum.Inc) of GVHD, CMV and EBV reactivation analysis was assessed accounting relapse and death as competing events. The multivariate analysis for OS and RFS was controlled by the following significant variables in the univariate analysis: age at transplant, disease risk index (DRI) (low and moderate v's high and very high), Karnofsky performance status (&gt;80% v's ≤80%), HCT-CI score ≥3 and donor type. Results Baseline characteristics and main post-transplant information and outcome are summarized in Table 1 and 2. The cum.Inc of grade II-IV and grade III-IV at day +100 was respectively 14% (95 confidence interval (CI) 11.1-18.4) and 4.7% (95% CI 2.8-7.2). The cum.Inc of moderate and severe chronic GVHD at 1 year was 13% (95% CI 9.7-16.8). ATG dose and donor type did not influence acute/chronic GVHD rates (Table 3). The cum.Inc of CMV and EBV reactivation at day +180 was comparable between the two cohorts that received different dose of ATG (P&gt;0.05). However, in the cohort that received a lower dose of ATG (2mg/kg), no CMV disease was documented and the percentage of probable or proven EBV-post-transplant lymphoprolipherative disease (P/P-PTLD) was only 3.7%. The percentages of CMV disease and P/P-PTLD in the group that received a dose of ATG of 4.5 mg/kg were respective 4.6% and 8.8%. Overall survival (OS), relapse-free survival (RFS), non-relapse mortality (NRM) and the cumulative incidence (cumInc) of acute GVHD of the entire cohort and according to the ATG dose are shown in the Table 2 and the Table 3. OS and RFS curves of all 365 patients and stratified according to donor type are shown in the Plots 1 to 4. In the multivariate analysis, age at transplant [(HR 1 (95% CI 1.01-1.02); P=0.046], high and very high DRI score [HR 1.8 (95% CI 1.2-3.6); P=0.001], KPS ≤80% [HR 1.8 (95% CI 1.2-2.7); P=0.001], and HCT-CI score ≥3 [HR 1.4 (95% CI 1.01-2.09); P=0.042] were significant risk factors for worse OS. Donor type was not a significant parameter for OS (P&gt;0.05). In the multivariate analysis of risk factors for RFS, high DRI score [HR 1.7 (95% CI 1.2-2.4); P=0.002], and a KPS ≤80% prior allo-HSCT [HR 2 (95% CI 1.4-2.8); P&lt;0.001] were significant risk factors for worse RFS. To receive grafts from a 10/10 MUD was a significant parameter for better RFS [HR 0.6 (95% CI 0.4-0.9); P=0.046]. Conclusions Dual T-cell depletion with ATG and PTCy provides an impressive control of GVHD with acceptable relapse rates using PB stem cell grafts independently of the donor type. This observation suggests that the present combination overcomes the HLA-barrier and its effect on GVHD. Acute GVHD rates are effectively controlled with a dose of ATG of only 2mg/kg when it is combined with PTCy and CsA. Further investigations need to be done to better define the efficacy of a lower dose of ATG controlling chronic GVHD in this setting. Further investigations and refinements need to be done to improve survival rates in those recipients with higher DRI score and worse KPS ≤80% prior transplantation. Disclosures Michelis: CSL Behring: Other: Financial Support. Mattsson:Gilead: Honoraria; Therakos: Honoraria; Celgene: Honoraria.

Improved Gvhd Free, Relapse Free Survival Using Dual T-Cell Depletion with ATG and Ptcy in Matched Unrelated Donor RIC Allo-HSCT

Introduction The combination of anti-thymoglobulin (ATG), post-transplant cyclophosphamide (PTCy) and cyclosporine (CsA) provides an effective control of graft-versus host disease (GVHD) in allo-HSCT using peripheral blood stem cell (PBSC) grafts, as has been reported by Dr. Viswabandya et al. We aim to report a large, single center experience in reduced intensity conditioning (RIC) allo-HSCT using dual T-cell depletion with ATG and PTCy combined with CsA for GVHD prophylaxis using grafts from 10/10 matched unrelated donors. Patients and methods Between October 2015 and April 2019, 167 adult patients diagnosed with hematological malignancies underwent first 10/10 MUD RIC allo-HSCT. RIC regimen was composed by fludarabine, busulfan, and 200cGy of total body irradiation. For GVHD prophylaxis all recipients received rabbit-ATG, PTCy 50mg/m2/day on day +3 and +4, and CsA since day +5. One hundred sixteen (69.5%) recipients, transplanted between 2015 and May 2018, received a total dose of 4.5mg/kg of rabbit-ATG (given on day -3,-2 and -1). In May 2018, the dose of ATG was lowered to a total of 2mg/kg (given on day -3 and -2). A total of 51 (30.5%) recipients received the lowered dose of ATG. The median follow-up of the entire cohort was 14 months (range: 0.4-44.5). For those patients who got a higher dose of ATG was 20 months and for those who received a lower dose of ATG was 8.8 months. Data was collected retrospectively and updated on July 2019. Cumulative incidence (Cum.Inc) of GVHD analysis was assessed accounting relapse and death as competing events. Results Baseline and post-transplant information are summarized in the Table 1 and 2. Ninety-three (55.7%) recipients were diagnosed with acute myeloid leukemia (AML). The cum.Inc of grade II-IV and grade III-IV acute GVHD at day +100 was respectively 15.6% (95% confidence interval (CI) 10.6-21.6) and 3.6% (95% CI 1.5-7.3). The cum.Inc of acute GVHD was not significantly affected by the dose of ATG (P&gt;0.05). The cum.Inc of chronic GVHD was 10.9% (95% CI 6.6-16.4). Due to the shorter median follow up of the cohort that received a lower dose of ATG, the impact of the reduction of the dose in the cum.Inc of chronic GVHD was not explored. Overall, 48 (28.7%) recipients died and 35 (20.4%) relapsed. Main causes of death were relapse (14.4%) and infection (9.6%). Outcome information is reported in the Table 2 and Plot A, B and C. One-year overall survival (OS), relapse-free survival (RFS) and GVHD-free/RFS (GFRFS) were respectively 75.6%, 70.3%, 60.4%. Table 3 summarizes the impact of the use of a different dose of ATG in acute GVHD and post-transplant outcome. No significant differences were found between the two groups that receive a different dose of ATG. However, median follow-up was shorter in the cohort that received 2mg/kg of ATG. Table 4 reports the main post-allo-HSCT information of patients diagnosed with AML. One-year OS, RFS and GRFRS for this subgroup of patients were 76.8%, 71.9% and 65.9%. Conclusion The unique and modern combination of RIC PB allo-HSCT using ATG, PTCY and CsA for GVHD prophylaxis results in impressive post-transplant outcomes using 10/10 MUD. The use of dual T-cell depletion with ATG and PTCy is safe and provides an extraordinary control of GVHD with acceptable relapse rates using PB stem cell 10/10 MUD grafts. ATG of only 2mg/kg when it is combined with PTCy and CsA, results in an effective control of acute GVHD rates. The optimal dose of ATG for GVHD prophylaxis is not well established. Further investigations need to be done to determine the efficacy of a lower dose of ATG controlling chronic GVHD in this setting. For patients diagnosed with AML, this protocol is safe and an effective approach when a 10/10 MUD is available. Disclosures Michelis: CSL Behring: Other: Financial Support. Mattsson:Celgene: Honoraria; Gilead: Honoraria; Therakos: Honoraria.

Time-Restricted Versus Standard Duration Immunosuppression after Allogeneic Hematopoietic Stem Cell Transplantation: Results from the Prospective Randomized Phase III HOVON-96 Trial

Background Allogeneic hematopoietic stem cell transplantation (alloHSCT) has been established as a powerful treatment modality for patients with hematological malignancies. The graft-versus-leukemia effect, however, is strongly associated with the occurrence of graft-versus-host disease (GVHD) and subsequent transplant-related mortality. The current standard Dutch regimen for prevention of GVHD in T-cell replete (TCR) alloHSCT following reduced intensity conditioning (RIC) consists of mycophenolic acid (MA) and cyclosporine A (CyA) for three and six months post-transplant, respectively. However, as approximately 30% of patients will never develop GVHD, immunosuppressive overtreatment is of concern and might impair outcome. Aims In the present prospective randomized, multicenter, phase III trial we set out to compare time-restricted immunosuppression versus a standard immunosuppressive regimen. The primary objective was to increase the proportion of patients with non-severe GVHD (either acute GVHD grades I-II without gut involvement or chronic GVHD not requiring systemic treatment) within 180 days after transplantation and to reduce the relapse rate, without increasing severe GVHD. Secondary endpoints included time to acute and chronic GVHD, progression-free survival (PFS), GVHD-free/relapse-free survival (GRFS), overall survival (OS), and adverse events. Methods Hematological patients planned to undergo TCR alloHSCT with a related or unrelated 8/8 HLA matched donor were included. The trial randomized patients between three treatment arms. The current analysis includes all patients randomized between arms A and B. Immunosuppression consisted of CyA twice daily aiming for serum trough levels of 250-350 µg/L and MA 16 mg/kg twice daily with a maximum dose of 2160 mg a day. The standard regimen (arm A) prescribed to discontinue MA at day 84 post-transplant and CyA was continued until day +120 followed by tapering until day +180. In those randomized for the time-restricted regimen (arm B) MA was discontinued at day 28 post-transplant and CyA was continued until day +84 followed by tapering. Results A total of 389 patients were randomized 1:1 between arms A and B, of whom 95% (184 in arm A versus 185 in arm B) proceeded to transplant. The median age was 55 (range: 18-71), 57% were male. Fifty-one patients received myeloablative conditioning and 318 (86%) patients RIC. Donors were matched siblings for 135 patients and matched unrelated donor (MUD) for 233 patients. The majority of patients received peripheral blood stem cells, consisting of median 6.46x106/kg CD34+ cells/kg (range: 0.94-26.3) and median 230x106/kg CD3+ T cells (range: 0-936). Baseline patient and transplantation characteristics were equally distributed between the treatment arms. The proportion of patients developing non-severe GVHD within 180 days post-alloHSCT was 24% in both treatment arms, with an odds ratio (OR) of 1.01 (95% confidence interval 0.61-1.67, p 0.98). The cumulative incidence (CI) of grade II-IV and grade III-IV acute GVHD at 6 months post-alloHSCT was not significantly different between the two arms (47% and 15% versus 52% and 18%), nor was the maximum grade or organ involvement of acute GVHD. In addition, no difference was seen in the two-year CI of chronic extensive GVHD between the two treatment arms (51% versus 49%). The three-year estimate of PFS was 51% (44-59%) versus 52% (44-59%), respectively. The three-year CI of progression/relapse was 28% in arm A versus 27% in arm B. OS at three years was 59% (0.51-0.66%) versus 57% (0.50-0.64%). The one-year estimate of the composite endpoint GRFS was 14% (9-19%) in arm A, and 17% (12-22%) in arm B. Incidences and nature of adverse events were comparable in both arms. Conclusion A time-restricted combination of MA and CyA did not increase the proportion of patients with non-severe GVHD within 180 days after transplantation and resulted in similar outcome as compared to standard immunosuppression following alloHSCT using sibling and well-matched unrelated donors. Given the observed high CI of acute grade II-IV and chronic extensive GVHD and low GRFS for both the time-restricted and standard regimen, recipients of TCR RIC alloHSCT should be considered for more intensive immunosuppression. Figure Disclosures Nur: Novartis: Consultancy. Deeren:Alexion, Amgen, Janssen, Roche, Sunesis, Takeda, Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.

Comparison of Two Doses of Antithymocyte Globulin in Reduced-Intensity Conditioning Allogeneic Hematopoietic Stem Cell Transplantation.

The appropriate dose of antithymocyte globulin (ATG) to be used in reduced-intensity conditioning (RIC) allogeneic hematopoietic stem cell transplantation (allo-HSCT) is yet to be determined. We retrospectively analyzed the outcomes of patients who underwent unrelated or mismatch related RIC allo-HSCT for hematologic malignancies and received r-ATG (4.5 mg/kg, 141 patients) versus R-ATG (6 mg/kg, 216 patients). There was a higher incidence of cytomegalovirus (P < .001) and Epstein-Barr virus viremia (P =.03) in the R-ATG group than in the r-ATG group. The cumulative incidences of acute graft-versus-host disease (aGVHD) grades II to IV at day 180 in the r-ATG and R-ATG groups were 59% and 44% (P = .006) and grades III to IV 20% and 12% (P = .029), respectively. In multivariable models adjusting for disease diagnosis, the risk of aGVHD grades III to IV did not reach statistical significance (P = .087). The respective cumulative incidences of chronic GVHD in the r-ATG and R-ATG groups were 26% and 15% (P = .10), respectively. There were no significant differences in relapse rate (P = .24), nonrelapse mortality (P = .96), progression-free survival (P = .24), overall survival (P = .70), and GVHD-free relapse-free survival (P = .24). In this retrospective analysis, aGVHD incidence was higher in those treated with r-ATG compared with R-ATG, but this did not translate into significant differences of clinical outcome. Given the increasing use of RIC allo-HSCT for treating malignant hematologic conditions, the correct dose and schedule of ATG administration should be defined by prospective randomized controlled trials.

Long-Term Outcomes after Reduced-Intensity Conditioning Allogeneic Hematopoietic Stem Cell Transplantation for Acute Myeloid Leukemia and Myelodysplastic Syndrome

Introduction Reduced-intensity conditioning (RIC) regimens have expanded allogeneic hematopoietic stem cell transplantation (allo-HSCT) to patients (pts) with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) who are unfit for myeloablative regimens. Several RIC regimens are typically used. We and others have previously shown that fludarabine-melphalan (FM) has a lower risk of relapse compared to fludarabine-busulfan (FB). Objectives Herein, we re-examine these findings with a larger cohort and longer follow-up. We also compare the composite endpoint graft-versus-host disease (GVHD)-free, relapse-free survival (GRFS), and elucidate factors that predict for relapse and NRM. Methods After IRB approval, we conducted a study of pts (age ≥18) diagnosed with AML or MDS who underwent allo-HSCT from January 1st, 2008 to March 1st 2017 at Mayo Clinic Rochester. Only pts who received FM (melphalan 140 mg/m2) or FB (busulfan 0.8 mg/kg IV for 10 doses with therapeutic AUC target of 900-1500 mcmol/L[min]) were included. Grade III-IV acute GVHD, systemic therapy-requiring chronic GVHD, relapse, or death counted as events for GRFS. Statistical analyses were performed using JMP 13 and EZR 1.36. Results We identified 184 pts who underwent RIC allo-HSCT: 135 with AML and 49 with MDS. The median age for the entire cohort was 61 (range, 18-74). FM was used in 123 pts, while 61 received FB. Baseline characteristics were comparable (Table 1a). The median follow-up was 5 years (95% CI, 4-5.6). In line with previous findings, the cumulative incidence of relapse (CI-R) was significantly higher with FB compared to FM: 3-year CI-R was 31.7% for FB vs. 17.3% for FM (p= .04)(Figure 1a). On the other hand, there was a nonsignificant trend towards an increased CI-NRM in the FM group; at Day +100, CI-NRM was 6.5% for FM vs. 1.6% for FB (p= .24). Acute and chronic GHVD were comparable (Table 1b). The median GRFS for the entire cohort was 7.3 months (95% CI, 6.1-8.4); there was no difference between the two regimens (p=.94). Overall survival (OS) was comparable (p= .61), as were causes of death (Figure 1b). In a multivariate Fine-Gray proportional hazard model for relapse vs. NRM, which included factors in Table 2; disease status (CR1 vs. CR2 or active disease) predicted relapse (HR 0.42, 95% CI 0.21-0.84, p=.01). There was also a trend towards a decreased risk of relapse with FM (HR 0.54, 95% CI 0.28-1.03, p=.06). On the other hand, age was predictive of NRM (HR 1.05 per year, 95% CI 1.01-1.09, p=.01). Conclusion In the present follow-up study, there were no significant differences in GRFS or OS between FM and FB regimens for RIC allo-HSCT in AML/MDS, despite FB having a significantly higher risk of relapse. Likely, the OS was balanced by continuing NRM after FM conditioning, particularly in older pts. Further studies, ideally prospective, are required to elucidate the optimal RIC regimen matched to disease biology and pt fitness.

Impact of antithymocyte globulin doses in reduced intensity conditioning before allogeneic transplantation from matched sibling donor for patients with acute myeloid leukemia: a report from the acute leukemia working party of European group of Bone Marrow Transplantation.

Antithymocyte globulin (ATG) is commonly used for graft-vs.-host disease (GVHD) prophylaxis in unrelated donor allogeneic transplantation (Allo-HSCT). However, its use is still controversial in matched sibling donor (MSD) Allo-HSCT, notably after reduced intensity conditioning (RIC). ATG dose may influence the outcome, explaining in part the discordant conclusions in MSD Allo-HSCT. We, therefore, analyzed the impact of ATG doses in patients with acute myeloid leukemia in first complete remission undergoing RIC Allo-HSCT from a MSD. We analyzed 234 patients from the EBMT registry and compared outcome according to given ATG dose (high dose: ≥ 6 mg/kg, n = 39 or low dose: < 6 mg/kg, n = 195). No difference was found in the cumulative incidence of acute (grade 2-4: high dose vs. low dose: 21% vs. 13%, p = 0.334; adjusted hazard ratio (HR): 1.20, p = 0.712) and chronic GVHD (extensive: high dose vs. low dose: 19% vs. 18%, p = 0.897; adjusted HR: 1.01, p = 0.980). In contrast, high dose of ATG significantly increased the incidence of relapse (52% vs. 26%, p = 0.011; adjusted HR: 1.31, p = 0.001) leading to impaired outcome (HR progression-free survival (PFS): 1.23, p = 0.002; HR overall survival (OS): 1.17, p = 0.029; HR GVHD and relapse-free survival (GRFS): 1.20, p = 0.005). We conclude that an ATG dose <6 mg/kg is sufficient for GVHD prophylaxis, while higher doses impair disease control and outcome.

A Time-to-Event Model for Acute Kidney Injury after Reduced-Intensity Conditioning Stem Cell Transplantation Using a Tacrolimus- and Sirolimus-based Graft-versus-Host Disease Prophylaxis

There is a paucity of data evaluating acute kidney injury (AKI) incidence and its relationship with the tacrolimus–sirolimus (Tac-Sir) concentrations in the setting of reduced-intensity conditioning (RIC) after allogeneic stem cell transplantation (allo-HSCT). This multicenter retrospective study evaluated risk factors of AKI defined by 2 classification systems, Kidney Disease Improving Global Outcome (KDIGO) score and “Grade 0-3 staging,” in 186 consecutive RIC allo-HSCT recipients with Tac-Sir as graft-versus-host disease prophylaxis. Conditioning regimens consisted of fludarabine and busulfan (n = 53); melphalan (n = 83); or a combination of thiotepa, fludarabine, and busulfan (n = 50). A parametric model, with detailed Tac-Sir consecutive blood levels, describing time to AKI was developed using the NONMEM software version 7.4. Overall, 81 of 186 (44%) RIC allo-HSCT recipients developed AKI with a cumulative incidence of 42% at a median follow-up of 25 months. Time to AKI was best described using a piecewise function. AKI-predicting factors were melphalan-based conditioning regimen (HR, 1.96; P < .01), unrelated donor (HR, 1.79; P = .04), and tacrolimus concentration: The risk of AKI increased 2.3% per each 1-ng/mL increase in tacrolimus whole blood concentration (P < .01). In multivariate analysis, AKI grades 2 and 3 according to KDIGO staging were independent risk factors for 2-year nonrelapse mortality (HR, 2.8; P = .05; and HR, 6.6; P < .0001, respectively). According to the KDIGO score, overall survival decreased with the increase in severity of AKI: 78% for patients without AKI versus 68%, 50%, and 30% for grades 1, 2, and 3, respectively (P < .0001). In conclusion, AKI is frequent after Tac-Sir–based RIC allo-HSCT and has a negative impact on outcome. This study presents the first predictive model describing time to AKI as a function of tacrolimus drug concentration.

Addition of More Immunosuppressive Drugs As Graft-Versus-Host Disease (GVHD) Prophylaxis Does Not Improve Gvhd Outcomes in Reduced Intensity Allogeneic Hematopoietic Cell Transplantation from Unrelated Donors

Background:Reduced-intensity conditioning (RIC) regimens have led to a dramatic reduction of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The concept of RIC is to deliver adequate immunosuppression with manageable graft-versus-host disease (GVHD) and the eventual development of a potent graft-versus-leukemia effect. Nevertheless, GVHD prophylaxis remains a challenging task after allo-HSCT. While the combination of cyclosporine A (CsA) and a short course of methotrexate (Mtx) after transplantation is considered as the gold standard for GVHD prophylaxis after conventional myeloablative allo-HSCT from HLA-identical siblings, there is no consensus on the optimal preventive GVHD prophylaxis after RIC allo-HSCT. On the other hand, recent and ongoing studies are evaluating a promising GVHD prophylaxis strategy using post-transplantation cyclophosphamide (PTCy). The aim of this study is to evaluate the impact of different GVHD prophylaxis used after RIC allo-HSCT in patients receiving peripheral blood stem cells (PBSC) from unrelated donors for hematological malignancies.Patients and methods:We evaluated 127 consecutive patients with hematological malignancies who received RIC allo-HSCT and were followed in our center between January 2008 and January 2016; 74 (58%) were males, median age was 58 years (range: 18-70), 52 (41%) had acute myeloid leukemia, 36 (28%) myelodysplastic syndrome, 12 (10%) myeloproliferative syndrome, 9 (7%) Non-Hodgkin lymphoma, 9 (7%) chronic lymphocytic leukemia, 6 (5%) multiple myeloma and 3 (2%) chronic myeloid leukemia. At transplantation, 65 (51%) patients were in complete response (CR) or chronic phase (CP). RIC regimen consisted on fludarabine, intermediate doses of IV busulfan and anti-thymocyte golbulins (ATG) (Thymoblobulin) in 56 (44%) patients and a sequential FLAMSA regimen in 71 (56%) patients and who also received similar doses of ATG (Thymoglobulin). PBSC donors were 10/10 HLA matched in 81 (64%) patients and 9/10 HLA mismatched in 46 (36%) patients. Patients were divided according to GVHD prophylaxis into 3 groups: group 1 consisted on CsA alone with 23 (18%) patients, group 2 include patients who received either CsA + mycophenolate mofetil (MMF), n= 64 (50%) or CsA + Mtx, n= 20 (16%) or CsA + cyclophosphamide n= 5 (4%), and group 3 included patients receiving CsA + MMF + tacrolimus n= 15 (12%) patients.Results:After transplantation, all patients in group 1 engrafted after a median of 17 (3-25) days, 81/89 (91%) engrafted in group 2 after a median of 17 (5-58) days and 14/15 (94%) engrafted in group 3 after a median of 16 (9-24) days. We did not observe any significant impact of the type of GVHD prophylaxis on the 100-day incidence of grade II to IV acute GVHD, which occurred in 6/15 (40%), 34/81 (42%) and 7/14 (50%) for the groups 1, 2 and 3 respectively (p=0.18). Grade III-IV acute GVHD occurred in 3 (20%), 24 (29%) and 5 (33%) in the three groups respectively (p=0.11). Similarly, cumulative incidence of 1 year chronic GVHD was not different between groups 1, 2 and 3 reaching 46%, 43% and 46% respectively (p=0.6) among them 3/15 (20%), 18 (22%) and 3/14 (21%) patients had an extensive form. After a median follow-up of 22 months for surviving patients, although there was no significant difference between the three groups in terms of non-relapse mortality, we observed more infection-related mortality with 45% and 83% in groups 2 and 3 respectively compared to 47% in group 1. The cumulative incidence of relapse at 2 years was 22%, 31 and 26% for the three groups respectively (p=0.23). Overall survival rates at two years were 43%, 31% and 44 % for groups 1, 2 and 3 respectively (p=0.42). The multivariate analysis taking into account the type of disease, donor HLA matching, disease status at transplantation, type of RIC and the type of prophylaxis, showed that the incidence of acute GVHD was influenced only by the use of FLAMSA regimen from mismatched donors, HR= 2.2 [1.3-3.1], p=0.05 which had also the same impact on the occurrence of chronic GVHD.Conclusion:Despite its limitations and the need for prospective randomized studies, the results of our study suggest that in the RIC allo-HSCT from unrelated donors, the different GVHD prophylaxis associations lead to similar GVHD outcomes. Patients with more immunosuppressive drugs had a higher incidence of infection-related mortality and in which PTCy could be a better option. DisclosuresNicolini:BMS: Consultancy, Honoraria; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Ariad: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Analysis of allogeneic hematopoietic stem cell transplantation with high-dose cyclophosphamide-induced immune tolerance for severe aplastic anemia

The study was aimed to explore the efficacy and safety of allo-HSCT with high-dose cyclophosphamide-induced immune tolerance for SAA. In the present study, 20 cases (12 male, 8 female; average age=17.8years) received reduced-intensity conditioning allo-HSCT from August 2012 to August 2014 in the Beijing Military Region General Hospital. All were HLA mismatched and received CSA; 11 received ATG-intensive immune therapy. Donors underwent mobilization with cell colony-stimulating factor. The modified preconditioning regimen included reduced-strength fludarabine combined with Busulfex and cytarabine, cyclophosphamide. Cyclophosphamide (50mg/kg/d) induced immune tolerance 3days after transplantation and was combined with immunosuppressive agents, including CSA, MTX, and FK506, for GVHD prophylaxis and the management of observed toxicity, GVHD and DFS. Hematopoietic reconstitution was achieved in 17 cases and engraftment after a second transplantation in an additional three cases. The average times to engraftment were 17.4 and 21.3days, respectively, with neutrophils ≥0.5×109/L and platelets ≥20×109/L. Engraftment was confirmed by the evidence of 100% donor hematopoiesis; T lymphocyte subset counts also increased significantly after transplantation. During follow-up monitoring to April 2015 (median duration=17.7months), three patients died of complications, while the other 17 showed disease-free survival (DFS rate=85%; longest DFS period=32months). Reduced-intensity allo-HSCT with high-dose cyclophosphamide-induced immune tolerance treatment is effective for SAA and can be the key technology extensively used in clinic, but its efficacy needs to be confirmed further with prospective randomized study with increased sample size.

A Phase I Study of Reduced-Intensity Conditioning and Allogeneic Stem Cell Transplantation Followed by Dose Escalation of Targeted Consolidation Immunotherapy with Gemtuzumab Ozogamicin in Children and Adolescents with CD33+ Acute Myeloid Leukemia

Myeloablative conditioning and allogeneic hematopoietic stem cell transplant (alloHSCT) in children with acute myeloid leukemia (AML) in first complete remission (CR1) may be associated with significant acute toxicity and late effects. Reduced-intensity conditioning (RIC) and alloHSCT in children is safe, feasible, and may be associated with less adverse effects. Gemtuzumab ozogamicin (GO) induces a response in 30% of patients with CD33+ relapsed/refractory AML. The dose of GO is significantly lower when combined with chemotherapy. We examined the feasibility and toxicity of RIC alloHSCT followed by GO targeted immunotherapy in children with CD33+ AML in CR1/CR2. Conditioning consisted of fludarabine 30 mg/m2 × 6 days, busulfan 3.2 to 4 mg/kg × 2 days ± rabbit antithymocyte globulin 2 mg/kg × 4 days followed by alloHSCT from matched related/unrelated donors. GO was administered ≥60 days after alloHSCT in 2 doses (8 weeks apart), following a dose-escalation design (4.5, 6, 7.5, and 9 mg/m2). Fourteen patients with average risk AML received RIC alloHSCT and post-GO consolidation: median age 13.5 years at transplant (range, 1 to 21), male-to-female 8:6, and disease status at alloHSCT 11 CR1 and 3 CR2. Eleven patients received alloHSCT from 5-6/6 HLA-matched family donors: 8 received peripheral blood stem cells, 2 received bone marrow, and 1 received related cord blood transplantation. Three patients received an unrelated allograft (two 4-5/6 and one 9/10) from unrelated cord blood unit and bone marrow, respectively. Neutrophil and platelet engraftment was observed in all assessable patients (100%), achieved at median 15.5 days (range, 7 to 31) and 21 days (range, 10 to 52), respectively. Three patients received GO at dose level 1 (4.5 mg/m2 per dose), 5 at dose level 2 (6 mg/m2 per dose), 3 at dose level 3 (7.5 mg/m2 per dose), and 3 at dose level 4 (9 mg/m2 per dose). Three of 14 patients received only 1 dose of GO after alloHSCT. One patient experienced grade III transaminitis, which resolved; no grade IV transaminitis, no grade III/IV hyperbilirubinemia, or sinusoidal obstructive syndrome were observed. The second dose of GO was given at median of 143 days (range, 120 to 209) after alloHSCT. Probability of grades II to IV acute and chronic graft-versus-host disease were 21% and 33.5%, respectively. Probability of overall survival after RIC alloHSCT and GO consolidation at 1 and 5 years was 78% and 61%, respectively. Probability of 5-year event-free survival after RIC alloHSCT and GO consolidation in patients in CR1 was 78%. No dose-limiting toxicities probably or directly related to GO were observed in this cohort. This preliminary data demonstrate that RIC followed by alloHSCT and consolidation with GO appears to be safe in children and adolescents with CD33+ AML in CR1/CR2. A phase II trial is currently underway investigating this approach with a GO dose of 9 mg/m2 per dose.

Impact of age on outcomes of allogeneic hematopoietic stem cell transplantation with reduced intensity conditioning in elderly patients with acute myeloid leukemia.

Previous studies have repeatedly reported that increasing age is a significant risk factor for worse outcomes after allogeneic hematopoietic stem cell transplantation (allo-HSCT) among patients with acute myeloid leukemia (AML). However, more recent studies reported conflicting results regarding the association between age and outcomes in elderly patients. Therefore, we conducted a large-scale, nationwide retrospective study to examine the impact of age on outcomes of allo-HSCT with reduced intensity conditioning (RIC) for AML patients who were older than 50 years. Of the 757 patients, 89 patients (11.8%) were 50-54, 249 patients (32.9%) were 55-59, 301 patients (39.8%) were 60-64 and 118 patients (15.6%) were ≥65 years old. The 3-year overall survival (OS) (47.8, 45.2, 37.9, and 36.6% for patients aged 50-54, 55-59, 60-64, and ≥65 years, respectively, P = 0.24) and nonrelapse mortality (NRM) (24.0, 22.8, 29.2, and 27.6% for patients aged 50-54, 55-59, 60-64, and ≥65 years, respectively, P = 0.49) were not significantly different among the four age groups. Multivariate analysis revealed that increased age had no significant effect on OS or NRM after adjusting for covariates. These results suggested that advanced patient age is not a contraindication for RIC allo-HSCT in elderly AML patients.

Comparison of Two Doses of Antithymocyte Globulin (ATG) in Reduced Intensity Conditioning (RIC) Allogeneic Hematopoietic Stem Cell Transplant (alloHSCT)

Introduction: The appropriate dose of antithymocyte globulin (ATG) to be used in reduced-intensity conditioning (RIC) allogeneic hematopoietic stem cell transplantation (allo-HSCT) is yet to be determined. In our previous retrospective analysis we compared two dosing schedules of ATG (7.5 mg/kg vs 6 mg/kg) in 136 patients who had undergone RIC allo-HSCT, and found no significant differences in the incidence of acute or chronic graft-versus-host disease (GVHD), non-relapse mortality (NRM), relapse, progression-free survival (PFS) or overall survival (OS). As of October 2013, our ATG dosing was lowered from 6.5 to 4.5 mg/kg. We now compare the outcomes of patients who received ATG at a dose of 4.5 mg/kg (r-ATG) to 6 mg/kg (R-ATG)Methods: We retrospectively analyzed the outcomes of patients who underwent unrelated or mismatch related RIC allo HSCT for hematologic malignancies and received r-ATG (40 patients) vs R-ATG (216 patients) at The Ohio State University Comprehensive Cancer Center between October 2007 and September 2014. Cumulative incidences of GVHD, infection, NRM, and relapse were analyzed using Gray's test, accounting for competing risks. PFS and OS were analyzed using the log-rank test.Results: Patients with hematologic malignancies included AML/MDS (53%), NHL/Hodgkin's (19%), CLL (12%), and other hematologic malignancies including ALL (16%). There was a significant association between disease group and ATG dose (p<0.001), with none of the patients diagnosed with CLL receiving r-ATG and a higher percentage of those with other malignancies receiving r-ATG vs R-ATG than expected. Secondary to the imbalance in disease groups, those receiving r-ATG were younger (median 50 vs 59 yrs, p=0.01) and more likely to have bone marrow stem cell source (18% vs 5%, p=0.008). There were no significant differences in recipient or donor sex, degree of HLA match, prior autografts, comorbidity index, donor/recipient CMV status and CD34 cell dose between the two groups. The cumulative incidences of acute GVHD grade II-IV at day 180 in the r-ATG and R-ATG groups were 63% and 44% (p=0.009), and of grade III-IV 18% and 11% (p=0.25) respectively (Figure 1A and B). When controlling for differences in underlying disease, the estimated risk of acute GVHD grade II-IV was 1.6 times higher with r-ATG (p=0.04). The respective cumulative incidences at 6 months of chronic GVHD were 14% and 16% (p=0.65), and of extensive chronic GVHD 14% and 13% (p= 0.29). With limited follow-up in patients receiving r-ATG (median 10 months), significant differences were not observed in longer-term outcomes between the two groups including relapse rate (p=0.83), NRM (p=0.91), PFS (p=0.92), and OS (p=0.996). The incidence of CMV reactivation at day 180 was lower in the r-ATG group (5% vs 26%, p=0.005), though the incidence of competing risks including GVHD, relapse and death prior to documented reactivation was higher in the r-ATG group (p<0.0001). No statistically significant differences were seen in Epstein-Barr virus reactivation (p=0.74), BK-virus associated hemorrhagic cystitis (p=0.79), bacterial infections (p=0.11), or Clostridium Difficile infections (p=0.22).ConclusionsWhile there was an increase in grade II-IV acute GVHD with r-ATG, there was no significant difference in acute GVHD grade III-IV, relapse, NRM, PFS and OS between the two cohorts. r-ATG resulted in a lower proportion of CMV reactivation, but in a higher proportion of other competing risks. Given the increasing use of RIC allo-HSCT for treating malignant hematologic conditions, the correct dose and schedule of ATG administration should be defined by prospective randomized controlled trials. [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

The Role of Spleen Directed Therapy and Predictors of Outcomes with Reduced Intensity Conditioning Allogeneic Hematopoietic Stem Cell Transplantation for Patients with Primary Myelofibrosis and Splenomegaly

Background: Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative treatment for primary myelofibrosis (PMF). Reduced intensity conditioning (RIC) allows otherwise ineligible patients to proceed with HSCT. Host factors in PMF such as bone marrow (BM) fibrosis, massive splenomegaly, and transfusion related allo-immunization increase the risk of engraftment failure, especially with RIC. Spleen directed therapy (SDT) is often used in PMF patients with splenomegaly to help with engraftment, however little data exists supporting this practice. This study was carried out to investigate the role for SDT and the predictors of outcomes with RIC HSCT for PMF.Methods :After IRB approval, the Mayo Clinic HSCT registry was queried for patients with PMF that underwent RIC allo-HSCT from 2005-2014. Disease and transplant related data were retrospectively abstracted and analyzed for HSCT related outcomes. SDT was defined as a therapeutic strategy with specific intent to overcome an enlarged spleen prior to HSCT and included splenectomy, splenic artery embolization, splenic irradiation, or JAK inhibitor therapy that was stopped <30 days before HSCT. Survival estimates were calculated using the Kaplan-Meier method and means were compared using the log-rank test. Univariate and multivariate analyses were performed using Cox regression modeling.Results :51 patients (67% males) with WHO defined PMF with palpable splenomegaly that underwent RIC allo-HSCT were included in the study; median age 57 years (range, 35-68). The median follow-up was 12.2 months, and at last follow up, 19 deaths (37%) and 4 relapses (8%) were documented. The median OS for the group was not reached (mean 34.2 months); 88% at 100 days and 60% at 2 years. 17 deaths were attributed to non-relapse mortality (NRM). There were 3 engraftment failures (6%). 32 patients (63%) developed acute GVHD (grades II-IV) and 24 patients (47%) developed chronic GVHD (all grades).Twenty-one patients (41%) received SDT; 10 (48%) splenectomy, 2 (9%) splenic irradiation, and 9 (43%) JAK inhibitor therapy (ruxolitinib). The SDT group had a median spleen size of 14.5 cm (range, 1-29 cm) below the left costal margin (LCM) and 13 patients (62%) with spleen size >10 cm below LCM, while the no SDT group had a median spleen size of 7 cm (range, 1-19 cm) and 12 patients (40%) with spleen size >10 cm below LCM; p = 0.01. Seven (64%) of 11 patients receiving splenic irradiation (n = 1) or JAK inhibitor therapy (n = 6) were eligible for IWG-MRT spleen response, and 2 (29%) responded (both in JAK inhibitor group). Of the remaining 5 patients, 2 had a response not meeting IWG-MRT criteria.There were no differences in age (p = 0.09), gender (p = 1.0), DIPSS + score (p = 0.35), or HCT-CI (p = 0.61) between the two groups. There was a statistically significant difference in engraftment failure, with all 3 engraftment failures occurring in the SDT group (2 splenectomy patients, 1 splenic irradiation patient; p = 0.02). Engraftment failures were not attributable to insufficient cell dose, donor specific antibodies, or identifiable host factors. The patient with engraftment failure who underwent splenic irradiation had persistent massive splenomegaly. There were similar outcomes with regards to relapse rates, NRM, and acute and chronic GVHD. In the SDT group, the median OS was 13.3 months; 81% at 100 days and 33% at 2 years. In the no SDT group, the median OS was not reached; 94% at 100 days and 68% at 2 years; p=0.13.In a univariate survival analysis that included age, gender, SDT, DIPSS+ score, HCT-CI, CMV status, ABO status, HLA matching, donor source, graft source, engraftment status, and acute and chronic GVHD, predictors of survival were engraftment failure (p = 0.02) and major/bidirectional ABO incompatibility (p = 0.02). Similar results were obtained when JAK inhibitor therapy was considered separately from other forms of SDT. In a multivariate analysis, engraftment failure (HR 8.2, 1.8-27.2; p = 0.01) and major/bidirectional ABO incompatibility (HR 4.1, 1.4-10.9; p = 0.009) retained independent prognostic significance.Discussion:In patients with PMF and splenomegaly, there was no demonstrable benefit from SDT. Predictors of post-HSCT survival included engraftment failure and major/bidirectional ABO incompatibility. These findings need validation in a larger cohort of patients. DisclosuresAl-Kali:Celgene: Research Funding. Mesa:Gilead: Research Funding; Incyte Corporation: Research Funding; Pfizer: Research Funding; Genentech: Research Funding; CTI Biopharma: Research Funding; Promedior: Research Funding; Novartis Pharmaceuticals Corporation: Consultancy; NS Pharma: Research Funding.