Median Donor Chimerism Research Articles

Hypomethylating Agents are Effective in Treatment for Relapsed Myelofibrosis After Allogeneic Hematopoietic Cell Transplantation

Myelofibrosis (MF) is a myeloproliferative neoplasm with a relapse rate of 10% to 30% after allogeneic transplantation (alloHCT). Current recommendations to treat relapse include withdrawal of immunosuppression, donor lymphocyte infusion, and potentially a second alloHCT. Hypomethylating agents (HMAs) have shown efficacy as salvage therapy by inducing an immune response and improving donor chimerism for myeloid neoplasm post-HCT. Data is limited on use of HMAs for MF post-alloHCT relapse. To determine the benefit of using HMAs for MF patients relapsing after alloHCT, we retrospectively analyzed 12 patients with MF post-alloHCT relapse who received HMA to determine response via restoration of donor chimerism and clearance of molecular mutation. The median age was 61 years (range 41-72) with 92% classified as intermediate-2/high-risk by the Dynamic International Prognostic Scoring System (DIPSS) and 83% as high/very high risk by the MIPSS70+ (Molecular International Prognostic Scoring System). The median time to relapse post-alloHCT was 282.5 days (range 96-2388) with median donor chimerism 57.82% (range 2.48-84.0) prior to starting an HMA. After two cycles of HMA, 58% experienced restoration of donor chimerism. Molecular clearance of pre-HCT driver mutations occurred in 50% of patients at the most recent follow-up. New chronic graft-vs.-host disease (cGVHD) occurred in 50% of patients, with most being mild to moderate that resolved after treatment. HMA was safe and effective in a high-risk population after post-alloHCT relapse and is an option for patients in the future.

Frequency and Clinical Significance of Mixed T-Cell Chimerism Following Myeloablative Busulfan and Cyclophosphamide Conditioning in HLA -Matched Donor Transplants for Myeloid Malignancies: An Analysis of 179 Patients Transplanted at a Single Center

Myeloablative busulfan and cyclophosphamide (BuCy2) is one of the most used preparative regimens for allogeneic hematopoietic cell transplantation for myeloid malignancies from HLA-identical (MRD) and 8 of 8 HLA-A, B, C and DRB1 allele matched unrelated (MUD) donors. However, mixed T-cell chimerism may be relatively common during the early post-engraftment phase using this regimen. The significance of early incomplete donor T-cell chimerism following BuCy2 allotransplants with respect to post-transplant outcomes is unclear. Methods: We analyzed 179 consecutive patients who underwent allotransplants for myeloid malignancies using myeloablative BuCY2 conditioning at our center. Cyclophosphamide was administered at 60mg/m2/d x 2 and busulfan was administered over four days with pharmacokinetically targeted exposure (usually 4.9 mgxhr/L) based on test dosing. Tacrolimus/methotrexate was used for GVHD prophylaxis. Uniform institutional supportive care protocols were employed for all patients. Lineage specific chimerism on T-cell (CD3) and myeloid (CD33) peripheral blood (PB) cells separated using immunomagnetic beads was performed monthly through d 100 following transplant. Patients with < 50% donor CD3 chimerism on d30 were scheduled to receive low dose DLI if available (starting at 5-10 x 10e5 CD3 cells /kg) while maintaining therapeutic tacrolimus levels. No intervention was performed if d30 donor CD3 chimerism was > 50%. Outcomes were analyzed using data extracted from our institutional database where information had been prospectively entered. GVHD diagnosis and grading were determined by a single dedicated practitioner. Results: Patient characteristics were: median age 50 (18-66), male 51%; diagnosis AML (65%), CML (23%) MDS/MPS (12%); MRD (52%) MUD (48%); graft source- PBSC 81%, BM18%, both 1%; DRI - low 12%, intermediate 57%, high 25%, very high 6%; donor CMV pos 51%, neg 49%; year of transplant- 2004-2012 (35%), 2013-2016 (32%) 2017-2021(33%). Median follow-up for surviving patients was 84 months (6-213). Kaplan-Meier (K-M) estimates for survival and relapse-free survival at 5 years for all patients were 66% (95%CI 58-73%) and 59% (51-66%). Median (range) donor chimerism on d 30 for CD3 cells was 80% (6-100%) and for CD33 cells was 100% (84-100%). Median CD3 chimerism on d 60, d 100 and d 180 were 86%(7-100%), 91% (8-100%) and 95% (12-100%) respectively. Twenty-four patients (13%) had CD3 <50% on d30 of which 9 received DLI. On multiple regression modeling (Table1) the following factors were associated with higher d 30 CD3 chimerism - diagnosis (AML vs other) (difference 0.104, p=0.001), DRI (high/v.high vs low/intermediate)(diff 0.070, p=0.03) and graft CD3 dose (>15.5x 10e7/kg vs < 15.5) (diff 0.105, p<0.001) For patients who had > 80% vs <80% donor CD3 chimerism on d 30, 5-year K-M estimates of survival and RFS were 56% vs 76% (p=0.003) and 54% vs 64% (p=0.16). Five-year cumulative incidences of NRM and relapse were 20% vs 8% (p=0.010) and 26% vs 28% (p=0.85). Cumulative incidences of grade 2-4 and grade 3-4 acute GVHD at 6 months were 49% vs 27% (p=0.002) and 20% vs 4% (p=0.001) respectively. Cumulative incidences of moderate to severe and severe chronic GVHD at 3 years were 81% vs 64% (p=0.017) and 53% vs 34% (p=0.008). On a Cox proportional-hazards model adjusting for significant patient, disease and transplant covariates, d 30 CD3 chimerism > 80% was associated with a significantly higher risk of NRM (HR 3.42, p=0.007), aGVHD gd 2-4(HR1.79, p=0.013), aGVHD gd 3-4 (HR 2.66, p=0.008) and severe cGVHD (HR 1.84, p=0.011). However, d 30 CD3 chimerism was not significantly associated with relapse, survival and relapse-free survival (Fig 1). Conclusions: These data suggest that while pharmacokinetically-targeted BuCy2 as administered is almost always myeloablative (CD33 chimerism 100%), early mixed T-cell chimerism is relatively common (CD3 chimerism < 80% in 50% of patients). d30 CD3 chimerism ≥80% is not associated with lower relapse rates or better survival outcomes, but is associated with higher rates of acute and chronic GVHD. No intervention to improve CD3 chimerism appears necessary for patients with d 30 CD3 chimerism between 50 and 80%. Patients with ≥ 80% CD3 chimerism at d 30 may benefit from more aggressive measures to prevent acute and chronic GVHD Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Optimizing Myeloablative Fractionated Busulfan, Fludarabine and Thiotepa Regimen: Results of Two Parallel Cohorts in a Phase 2 Prospective Clinical Trial

Background: Myeloablative conditioning can be given safely to older patients by simply administering busulfan (Bu) over a longer period (fractionated (f)-Bu) with fludarabine (Flu) than the standard four-day regimen. (Popat et al Lancet Haematology 2018). We added thiotepa (Thio) to this f-Bu/Flu regimen in patients with haploidentical (haplo) donors to promote engraftment and to reduce relapse. With encouraging results, Thio was then added in matched unrelated (MUD) and sibling (MSD) donor recipients also. However, the optimal doses of Thio and Bu were undefined. To further optimize the regimen, we tested two different f-Bu/Flu/Thio regimens in parallel prospective cohorts: (a) higher dose Bu with lower dose Thio, and (b) lower dose Bu with a higher dose Thio. Patients were enrolled on these cohorts based on age and co-morbidity index (HCT-CI). Herein, we report on the safety and preliminary efficacy of these regimens (NCT02861417).Methods: Patients <60 years with HCT-CI <3, or >60 years with HCT-CI <2 received IV f-Bu to target an area under the concentration vs time curve (AUC) of 20,000 ± 12% μmol.min with Thio 2.5 mg/kg (Bu20K/Thio2.5; Cohort 1). Patients <60 years with an HCT-CI >3, or >60 years with HCT-CI >2, or >70 years irrespective of HCT-CI received f-BU to target AUC of 16,000 with Thio 5mg/kg (Bu16K/Thio5; Cohort 2). In both cohorts, the first two doses of Bu (80 mg/m2 IV each) were given as outpatient on days -20 and -13. The last four Bu doses were given as inpatient following each dose of Flu 40 mg/m2 on days -6 through -3. Thio was given on day -7. GVHD prophylaxis was post-transplant cyclophosphamide (PTCy) 50mg/kg on days 3 and 4, tacrolimus and MMF.Results: 66 patients were enrolled - 25 in cohort 1 and 41 in cohort 2, with a median age 60 years (range, 22-69) vs 62 years (range, 30-74), respectively (P=0.14). Diagnoses were AML/MDS (64% vs 54%), CML/MPD (24% vs 22%), ALL (12% vs 22%) and 1 myeloma; P=0.24. Most had intermediate disease risk index (80% vs 73%, P=0.57); median HCT-CI was 1 (range, 0-6) vs 3 (range, 0-9); P<0.0001. Donor was haplo (60% vs 19%), MUD (24% vs 54%) or MSD (16% vs 27%); P=0.002; BM graft was used in 56% vs 27%; p=0.02, respectively, in cohorts 1 and 2. The median follow-up among survivors was 18.7 months.Primary graft failure occurred in 1 patient in cohort 1 and none in cohort 2. The median time to neutrophil engraftment was 17.5 days (range, 14-26) vs 18 days (range, 12-26); P=0.12, respectively; platelet engraftment > 20K was 30 days in both groups; P=0.75. Median donor chimerism at day 30 was 100% in both groups. The incidence of acute GVHD grade III-IV was 4% vs 5%; P=0.88 at day 100; extensive chronic GVHD at 1 year was 13% vs 10%; P=0.83. At 1-year overall survival was 72% vs 78%; P=0.95; relapse was 12% each; non-relapse mortality was 20% vs 17%; P=0.97 [Table 1, Fig 1]. Common grade >3 toxicities were neutropenic fever (64% vs 42%; P=0.13), bacterial infection (44% vs 34%; P=0.45), nausea (12% vs 2%; P=0.15), mucositis (8% vs 5%; P=0.63), pneumonitis (12% vs 7%; P=0.67), hemorrhagic cystitis (8% vs 5%) and sinusoidal obstructive syndrome (8% vs 2.4%).Conclusion: In this population of older patients and/or high co-morbidities, both myeloablative regimens with f-Bu/Flu with thiotepa and PTCy were well tolerated and led to low NRM, low risk of relapse and encouraging survival. Although both regimens led to similar outcomes, the f-Bu/Flu/Thio regimen with Bu16K and thiotepa 5 mg/kg dose may be preferred as this was used in patients who were older and/or had high co-morbidities. [Display omitted] DisclosuresPopat: Bayer: Research Funding; Abbvie: Research Funding; Novartis: Research Funding; Incyte: Research Funding. Mehta: CSLBehring: Research Funding; Kadmon: Research Funding; Syndax: Research Funding; Incyte: Research Funding. Hosing: Nkarta Therapeutics: Membership on an entity's Board of Directors or advisory committees. Rezvani: Caribou: Other: Scientific Advisory Board; Virogin: Other: Scientific Advisory Board ; AvengeBio: Other: Scientific Advisory Board ; GSK: Other: Scientific Advisory Board ; Bayer: Other: Scientific Advisory Board ; Navan Technologies: Other: Scientific Advisory Board; GemoAb: Other: Scientific Advisory Board ; Takeda: Other: License agreement and research agreement, Patents & Royalties; Pharmacyclics: Other: Educational grant, Research Funding; Affimed: Other: License agreement and research agreement; education grant, Patents & Royalties, Research Funding. Qazilbash: Oncopeptides: Other: Advisory Board; Janssen: Research Funding; Bristol-Myers Squibb: Other: Advisory Board; NexImmune: Research Funding; Amgen: Research Funding; Angiocrine: Research Funding; Biolline: Research Funding. Shpall: Affimed: Patents & Royalties; Adaptimmune: Consultancy; Novartis: Consultancy; Magenta: Consultancy; Magenta: Honoraria; Axio: Consultancy; Takeda: Patents & Royalties; Navan: Consultancy; Novartis: Honoraria; Bayer HealthCare Pharmaceuticals: Honoraria.

HLA-Matched Related Hematopoietic Stem Cell Transplantation in Adolescents and Adults with Sickle Cell Disease: Comparison of Myeloablative Versus Non Myeloablative Approaches. Report from the Société Francophone De Greffe De Moelle Et De Thérapie Cellulaire

IntroductionAllogeneic hematopoietic stem cell transplantation (HSCT) is a curative therapy for sickle cell disease (SCD) allowing a SCD-free survival over 95% among children with matched HLA-identical donor (Gluckman E. Blood, 2017; Bernaudin F. Haematologica, 2020). In adults, myeloablative HSCT is associated with more graft-versus host disease (GVHD) and higher toxicity (Cappelli B. Haematologica, 2019). More recent approaches using non myeloablative (NMA) conditioning regimen (3 gray (Gy) total body irradiation (TBI) plus alemtuzumab) followed by HLA-identical peripheral blood stem cells (PBSC) and post-transplant sirolimus appear safe in adults (Hsieh MM. JAMA, 2014), but incidence of graft failure might be higher than the one reported after myeloablative conditioning (MAC) (Alzahrani M. Br J Haematol, 2021). Here, we compare outcomes after MAC or NMA conditioning regimens in patients over 15 years old transplanted from a matched related donor (MRD).Patients and methodsAll consecutive patients transplanted for SCD from a MRD from January 2015 to October 2020 were eligible if they were over 15 years old and received a busulfan-based MAC conditioning regimen or a NMA conditioning regimen.Chimerism was studied by analyzing various polymorphisms after polymerase chain reaction (PCR) amplification of DNA obtained from whole blood cells. Rejection was defined as donor chimerism <5%. Event-free survival (EFS) was defined as the probability to be alive with blood donor chimerism over 20%.ResultsThirty-four patients were included: 20 in the MAC and 14 in the NMA groups. Median age at transplant was 17 years (range 15-46) without difference between groups. Forty four percent of patients had a history of cerebral vasculopathy, 79% of recurrent vaso-occlusive crises and 76% of acute chest syndrome. ABO major incompatibility was present in 15% of patients. There was no difference in patient characteristics according to the conditioning regimen group except for pre-transplant cerebral vasculopathy, more frequently reported in the MAC group: 70% versus 6% in the NMA group (p<0.001).In the MAC group, conditioning regimen associated busulfan (12.8 mg/kg IV), cyclophosphamide (N=17) or fludarabine (N= 3) and anti-thymoglobulin (ATG, mostly 20mg/kg). Stem cell source was bone marrow and post-transplant immunosuppression combined cyclosporine and mycophenolate or methotrexate. In the NMA group, conditioning regimen associated 3Gy TBI and alemtuzumab (1mg/kg), followed by PBSC and post-transplant sirolimus.All patients engrafted and no secondary graft failure was observed. One MAC group patient died from GVHD. The 2-year overall and EFS were 95% (CI 95%: 85.9-100) in the MAC group (median follow-up of 39 months (range 8-63)) and 100% (CI 95%: 100-100) in the NMA group (median follow-up of 17 months (range 9-39)). Incidence of grade II-IV acute GVHD was 0% in the NMA group versus 20% in the MAC group (p=0.12). Incidence of chronic GVHD was 0% in the NMA group versus 25% in the MAC group (p=0.06). From the 27 patients with follow-up>12 months, 17/17 discontinued immunosuppressive therapy in the MAC group versus 8/10 in the NMA group. Hematopoietic recovery was faster in the NMA group with less platelet and red blood cell units transfused (Table). Throughout the follow-up, median donor chimerism was higher after MAC transplantation than after NMA transplantation: 98% (range 69-100) and 86 % (range 50-97) respectively at 1 year (p=0.017). Donor chimerism remained above 50% throughout the follow-up in all patients except 1 of the NMA group who displayed stable chimerism between 40 and 50%. All patients achieved HbS level close to the one of their donors. There was no difference between the 2 groups regarding occurrence of infections. MAC transplant was more often associated with hypertension, neurological complications, severe mucositis and need of enteral or parenteral nutrition. Moreover, duration of hospitalization was longer in MAC group: 54 days (range 39-192) versus 35 days in the NMA group (range 21-52) (p<0.001) (table).ConclusionIn this series of adolescents and adults transplanted for SCD, the survival without SCD was excellent with a faster hematological recovery and a lower toxicity after NMA HSCT. Longer follow-up is required to confirm stable mixed donor chimerism and the cure of SCD after NMA approach. [Display omitted] DisclosuresJoseph: bluebird bio: Consultancy. Boissel: Servier: Consultancy, Honoraria; JAZZ Pharma: Honoraria, Research Funding; Incyte: Honoraria; Amgen: Consultancy, Honoraria, Research Funding; SANOFI: Honoraria; CELGENE: Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; PFIZER: Consultancy, Honoraria. Pondarré: ADDMEDICA: Honoraria.

Fludarabine–Cyclophosphamide-Based Conditioning with Antithymocyte Globulin Serotherapy Is Associated with Durable Engraftment and Manageable Infections in Children with Severe Aplastic Anemia

Severe aplastic anemia (SAA) is a bone marrow failure syndrome that can be treated with hematopoietic cell transplantation (HCT) or immunosuppressive (IS) therapy. A retrospective cohort of 56 children with SAA undergoing transplantation with fludarabine–cyclophosphamide–ATG-based conditioning (FluCyATG) was analyzed. The endpoints were overall survival (OS), event-free survival (EFS), cumulative incidence (CI) of graft versus host disease (GVHD) and CI of viral replication. Engraftment was achieved in 53/56 patients, and four patients died (two due to fungal infection, and two of neuroinfection). The median time to neutrophil engraftment was 14 days and to platelet engraftment was 16 days, and median donor chimerism was above 98%. The overall incidence of acute GVHD was 41.5%, and that of grade III-IV acute GVHD was 14.3%. Chronic GVHD was diagnosed in 14.2% of children. The probability of 2-year GVHD-free survival was 76.1%. In the univariate analysis, a higher dose of cyclophosphamide and previous IS therapy were significant risk factors for worse overall survival. Episodes of viral replication occurred in 33/56 (58.9%) patients, but did not influence OS. The main advantages of FluCyATG include early engraftment with a very high level of donor chimerism, high overall survival and a low risk of viral replication after HCT.

Treatment of Secondary Post-Transplant Engraftment Failure with Donor CD34+ Enriched, T-Cell Depleted Peripheral Blood Stem Cells Isolated By the Clinimacs® System

Introduction: Secondary engraftment failure after hematopoietic stem cell transplant (HSCT) is characterized by pancytopenia and 1-year mortality reported to reach as high as 75% (1) secondary to infectious and bleeding complications. It is frequently associated with treatment of CMV reactivation. Reinfusion of a second graft from the original donor is the preferred treatment but carries the risk of graft versus host disease (GVHD) given high T lymphocyte graft content. The CliniMACS® CD34 reagent system permits in vitro selection and enrichment of CD34+ cells from heterogeneous hematologic cell populations and is used for T cell depletion of HSCT. We report the results of a pilot study of infusion of CD34+ selected stem cell boost for treatment of post-transplant secondary engraftment failure.Methods: Eligible patients were 0 - 80 years of age, treated with a prior HSCT and diagnosed with secondary engraftment failure (defined as a decrease in donor chimerism by ≥ 50%) or incomplete graft function (anemia ≤8g/dL or transfusion dependent; neutropenia ≤1000/mcl or requiring growth factor support; thrombocytopenia ≤20,000/mcl or transfusion dependent). Subjects were excluded if the original donor was not available or if they had reversible causes for engraftment failure, including active viral infections, continued use of myelosuppressive medications or uncontrolled acute or chronic GVHD. Once collected, peripheral blood stem cell (PBSC) donor grafts were processed using the CliniMACS® System and CD34 reagent to enrich CD34+ cell content and decrease CD3+ cell content. After enrichment, the product was considered acceptable for infusion if CD34+ cell content was ≥ 1x106 cells/kg and CD3+ content was ≤ 5x104 cells/kg. The CD34+ enriched stem cell boost was infused without a preceding conditioning regimen.Results: 10 patients were enrolled; median age was 53.5 years (range 7 - 69), 6 patients were male. Diagnoses included: aplastic anemia (n=1), acute lymphoblastic leukemia (n=1), acute myeloid leukemia (n=3), myelodysplastic syndrome (n=2) and non-Hodgkin lymphoma (n=3). The original graft source was PBSC from a matched related donor (MRD) in 3 subjects, matched unrelated donor in 6 cases, and one haploidentical related donor. GVHD prophylaxis included tacrolimus and methotrexate (n=8), tacrolimus, methotrexate and mycophenolate (n=1); one subject did not receive GVHD prophylaxis as part of a T cell depleted transplant. Eight patients had resolved or controlled GVHD. Median donor chimerism before engraftment failure was 98% (range 96 - 100).The cause of engraftment failure was known in 5 cases (irreversible medication toxicity [n=3], recurrence of aplastic anemia [n=1], viral infection [n=1]). Median time to diagnosis of secondary engraftment failure was 4 months (range 2-21). Median donor chimerism before boost was 2.5% (range 0-91%). Neutrophil engraftment failure was present in 6 patients; red blood cell (RBC) and platelet engraftment failure was present in 8 patients. Median time from transplant to boost infusion was 7.5 months (range 2-27)Median infused CD34+ cell dose was 3.15 x 106 CD34+ cells/kg (range1.67-10.9); median CD3+ cell dose was 1.9 x 103 CD3+ cells/kg (range 1.43 - 26.2). There were no infusion reactions and all patients tolerated the procedure without adverse events. Thirty days after boost infusion, 7 subjects (70%) had resolution of their cytopenias, 1 patient had platelet engraftment but remained dependent on RBC transfusions and 2 did not respond. We observed 2 cases of recurrence of GVHD; in both cases, the recurrence was at a lower grade than before the boost infusion. One responsive patient presented subsequent engraftment failure after boost (refractory aplastic anemia). Five patients remain alive at a median of 37 months after CD34+ enriched stem cell boost, with 1 - year estimated survival of 56%.Conclusions: Secondary engraftment failure can be safely and effectively treated with infusion of a CD34-enriched boost using the CliniMACS® System.Davies SM, Weisdorf DJ, Haake RJ, et al. Second infusion of bone marrow for treatment of graft failure after allogeneic bone marrow transplantation. Bone Marrow Transplant 1994;14:73-7. DisclosuresCaimi:Abbvie: Equity Ownership; Incyte: Equity Ownership; Seattle Genetics: Equity Ownership; Celgene: Speakers Bureau. Malek:Takeda: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi: Membership on an entity's Board of Directors or advisory committees; Celgene: Speakers Bureau. Cooper:Novartis: Research Funding. de Lima:Celgene Corporation: Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees.

Donor Lymphocyte Infusion after Allogeneic Haematopoietic Stem Cell Transplant, a Single Centre Retrospective Study

IntroductionAllogeneic haematopoietic stem cell transplant (allo-HSCT) is the only curative treatment for many haematological malignancies, however, relapse remains the main cause of treatment failure. Relapse is associated with dismal prognosis and poor survival, therefore, post allo-HSCT strategies to monitor, recognise and prevent impending relapse are of major value. Donor lymphocyte infusions (DLI) are used pre-emptively in patients with mixed donor chimerism (MDC) to enhance the graft-versus-leukaemia effect, in high risk patients as a prophylactic measure to prevent relapse and in relapsed patients with or without salvage chemotherapy.Patients and MethodsOne hundred and twenty-five patients received DLI between January 2010 and June 2017 in our institution. Median age at transplant was 57 years (range 25-74). Sixty-three patients had acute myeloid leukaemia (AML), 16 had myelodysplastic syndrome (MDS), 17 had multiple myeloma (MM), 12 had lymphoproliferative disorders, 11 had myeloproliferative disorders (MPD) and 6 had acute lymphoblastic leukaemia (ALL). Sixty-five percent of patients were in complete remission at the time of allo-HSCT, 24% in partial remission and 11% underwent an allo-HSCT without any previous treatment. Fifty-eight patients had a matched sibling donor, 56 a matched unrelated donor and 11 a mismatched unrelated donor. Ninety percent of patients received a reduced intensity conditioning regimen and 83% with T-cell depletion. MDC was defined as donor CD3 percentage less than 95%. DLI was given pre-emptively in patients with MDC, prophylactically for high risk AML/MDS patients and to patients with haematological relapse. DLI was administered using escalating doses.ResultsSixty-six patients received pre-emptive DLI, 9 patients prophylactic DLI and in 50 patients DLI was a part of their salvage treatment. Median doses were 0.1 x107/kg for the first DLI, 0.5 x107/kg for the second, 1.0 x107/kg for the third, 5 x107/kg for the fourth and >5 x107/kg for the subsequent doses. Median follow up from day of first DLI was 12 months (range 1-88).In the pre-emptive group median donor chimerism for CD3 at the time of DLI was 64.5% (range 5-94), median days from transplant to first DLI was 161 days (range 74-715) and median DLI administration was 1 (range 1-6). A total of 32 patients (48%) developed graft-versus host disease (GvHD) post-DLI; grade 1-2 in 21 patients (32%), grade 3 in 8 (12%) and grade 4 in 3 (4%). Two patients died due to GvHD. Median time between the last DLI and GvHD was 51 days (range 13-112). Seventy percent achieved full donor chimerism. Relapse was seen in 13 patients (20%), among them 4 are still alive.In the prophylactic group all patients but 1 received FLAMSA-TBI as a conditioning regimen. All had full donor chimerisms when they received DLI. Median time from transplant to DLI was 173 days (range 43-263) with a median of 2 DLI (range 1-4). Only two patients developed GvHD, there was no grade 3-4 GvHD. Five patients (56%) relapsed and died, and one patient died due to a secondary malignancy being in complete remission.In the treatment group, DLI was combined with Azacitidine in 14 patients, with Lenalidomide in 13 patients and with chemotherapy in 10 patients, 13 patients received DLI without any salvage treatment. Median time to DLI was 271 days (range 67-2476) with a median of 2 DLI (range 1-6). GvHD occurred in 13 patients (26%), one patient had grade 3 GvHD, all others had grade 1-2 GvHD. Sixty-eight percent died because of disease progression.Overall survival (OS) for the whole cohort at 1, 2 and 5 years after the first DLI was 65%, 52% and 39% respectively. Patients receiving pre-emptive DLI had better survival (OS of 83% at 1 year, 74% at 2 years and 57% at 5 years) compared to the treatment group (OS of 75% at 1 year, 55% at 2 years and 24% at 5 years) and to the prophylactic group (OS of 44% at 1 year, 33% at 2 years and 16% at 54 months) (p < 0.005). GvHD was associated with better survival for the entire group (p=0.009).ConclusionsIn our cohort of patients pre-emptive DLI showed better results when compared to prophylactic and treatment DLI, although the numbers in the prophylactic group are scanty. GvHD post-DLI was associated with better outcomes. DisclosuresTholouli:Jazz Pharmaceuticals: Honoraria, Speakers Bureau; MSD: Honoraria, Speakers Bureau; Pfizer: Honoraria, Speakers Bureau. Dignan:Mallinckrodt Pharmaceuticals: Other: Travel expenses and speakers fees, Research Funding.

Reduced Toxicity Conditioning for Nonmalignant Hematopoietic Cell Transplants.

Allogeneic hematopoietic cell transplantation (HCT) for children with nonmalignant disorders is challenged by potential drug-related toxicities and poor engraftment. This retrospective analysis expands on our single pediatric medical center experience with targeted busulfan, fludarabine, and intravenous (IV) alemtuzumab as a low-toxicity regimen to achieve sustained donor engraftment. Sixty-two patients received this regimen for their first HCT for a nonmalignant disorder between 2004 and 2018. Donors were matched sibling in 27%, 8/8 HLA allele-matched unrelated in 50%, and 7/8 HLA allele-mismatched in 23% (some of whom received additional immunoablation with thiotepa or clofarabine). Five patients experienced graft failure for a cumulative incidence of 8.4% (95% CI, 1 to 16%). In engrafted patients, the median donor chimerism in whole blood and CD3, CD14/15, and CD19 subsets at 1-year were 96%, 90%, 99%, and 99%, respectively. Only one patient received donor lymphocyte infusions (DLIs) for poor chimerism. Two patients died following disease progression despite 100% donor chimerism. The 3-year cumulative incidence of treatment-related mortality was 10% (95% CI, 2 to 17%). Overall survival and event-free-survival at 3-years were 87% (95% CI, 78 to 95%) and 80% (95% CI, 70 to 90%), respectively. The 6-month cumulative incidence of grade II to IV acute graft-versus-host disease (GVHD) was 7% (95% CI, 3 to 13%), while the 3-year cumulative incidence of chronic GVHD was 5% (95% CI, 0 to 11%). These results suggest that use of targeted busulfan, fludarabine and IV alemtuzumab offers a well-tolerated option for children with nonmalignant disorders to achieve sustained engraftment with a low incidence of GVHD.

Reduced Toxicity Conditioning for Non-Malignant Hematopoietic Cell Transplants

Background. Reduced-intensity conditioning (RIC) regimens are commonly used for hematopoietic cell transplantation (HCT) in non-malignant disorders to minimize potential drug-related toxicity from myeloablative conditioning (MAC). However, melphalan-based RIC regimens are associated with poor engraftment and need for second HCT or donor lymphocyte infusions (DLIs). This study expands on our previous experience with targeted busulfan, fludarabine, and intravenous (IV) alemtuzumab as a low-toxicity but myeloablative regimen to achieve sustained donor engraftment. Methods. We conducted a retrospective analysis of patients ≤25 years of age with non-malignant disorders who received targeted busulfan, fludarabine and IV alemtuzumab as conditioning for their first HCT between 2004 and 2018. Graft-versus-host disease (GVHD) prophylaxis included calcineurin inhibitors in all patients, plus methotrexate (n=59), methylprednisolone (n=2), or mycophenolate (n=1). The primary end point was 3-year overall survival (OS). Secondary end points included treatment-related mortality (TRM), event-free survival (EFS) defined as alive without second HCT or disease progression, and incidence of acute and chronic GVHD (aGVHD and cGVHD). Other end points included incidence of graft failure (GF) defined as &lt;5% donor chimerism in whole blood, sinusoidal obstruction syndrome (SOS) and CMV viremia. Analysis was stratified by era of HCT (2004-2011 vs. 2012-2018). Results. We identified 62 patients with a median age of 5.5 years and male:female of 46:16. Diagnoses included primary immune deficiencies (60%), hemoglobinopathies (22%), bone marrow failure disorders (8%) and inherited metabolic disorders (10%). The median busulfan cumulative area-under-the-curve (cAUC) was 70 mg*h/L (range, 57-108 mg*h/L). Donors were matched sibling (MSD) in 27%, 8/8 allele-matched unrelated (MUD) in 50% and Class I allele-mismatched (MM) in 23%. All but 2 of the Class I allele-MM donors were unrelated. The source was bone marrow (BM) in 74% and peripheral blood stem cells (PBSC) in 26%. The cumulative incidence (CI) of GF was 8% (95% CI, 1-16%). In engrafted patients, the median donor chimerism in whole blood, CD3, CD14/15, and CD19 at 1-year was 96%, 90%, 99%, and 99%, respectively. Only 1 patient required DLIs for poor chimerism. T-cell reconstitution (CD4 &gt;200 x 109/L and PHA response &gt;50% control) was achieved at a median of 182 days (range, 76-585 days). Two patients died following disease progression despite 100% donor chimerism. The CI of TRM was 10% (95% CI, 2-17%). Causes of TRM included infectious complications (n=2), hemorrhage (n=1), respiratory failure (n=3 with 2 following subsequent transplants after graft rejection). TRM incidence was significantly higher in patients with Class I MM compared to those with MSD or 8/8 allele-MUD (29% vs 6% vs 3%; p=0.024; Figure 1A). SOS occurred in 5% of patients and all resolved with supportive therapy (n=1) or defibrotide (n=2). Post-transplant CMV viremia occurred in 26% of all patients and in 71% of CMV seropositive patients. None developed CMV disease and all infections resolved with anti-viral therapy. OS and EFS at 3-years were 87% (95% CI, 78-95%) and 80% (95% CI, 70-90%), respectively. HCTs performed in the more recent era showed an OS of 97% compared to 79% in HCTs performed earlier (p=0.057; Figure 1B). OS was 97% in patients with 8/8 allele-MUD compared to 79% in those with MSD and 71% in those with Class I allele-MM (p=0.051). The 6-month CI of grade II-IV aGVHD was 7% (95% CI, 3-13%), while the 3-year CI of cGVHD was 5% (95% CI, 0-11%). GVHD incidence was higher in patients receiving PBSC compared to BM (25% vs 0%; p&lt;0.001) and in patients ≥5 years of age compared to those &lt;5 years of age (13% vs 0%; p=0.043). Patients with inherited metabolic disorders showed significantly worse OS (44%, p=0.016), EFS (33%, p=0.001) and aGVHD (33%, p=0.008) than those in other disease groups. Univariate analysis did not show any significant differences in survival or GVHD incidence by race or sex. Conclusions. Use of targeted busulfan, fludarabine and IV alemtuzumab as myeloablative conditioning in pediatric patients with primary immunodeficiencies, hemoglobinopathies, and bone marrow failure syndromes undergoing matched sibling or well-matched unrelated donor HCT provides a well-tolerated option to achieve sustained engraftment with low incidence of GVHD and toxicities such as SOS. Figure 1 Disclosures Shimano: Pfizer: Research Funding; Daiichi Sankyo: Research Funding; Novartis: Research Funding. Huang:Novartis: Research Funding. Cowan:Homology Medicine: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Leadiant: Consultancy; California Institute Of Regenerative Medicine: Research Funding; NIH NIAD: Research Funding; Rocket Pharma: Consultancy; UpToDate: Honoraria; bluebird bio: Consultancy. Dvorak:Alexion Inc: Consultancy; Jazz Pharmaceuticals: Consultancy.

A phase II clinical trial of adoptive transfer of haploidentical natural killer cells for consolidation therapy of pediatric acute myeloid leukemia

Consolidation therapies for children with intermediate- or high-risk acute myeloid leukemia (AML) are urgently needed to achieve higher cure rates while limiting therapy-related toxicities. We determined if adoptive transfer of natural killer (NK) cells from haploidentical killer immunoglobulin–like receptor (KIR)–human leukocyte antigen (HLA)-mismatched donors may prolong event-free survival in children with intermediate-risk AML who were in first complete remission after chemotherapy. Patients received cyclophosphamide (Day − 7), fludarabine (Days − 6 through − 2), and subcutaneous interleukin-2 (Days − 1, 1, 3, 5, 7, and 9). Purified, unmanipulated NK cells were infused on Day 0, and NK cell chimerism and phenotyping from peripheral blood were performed on Days 7, 14, 21, and 28. As primary endpoint, the event-free survival was compared to a cohort of 55 patients who completed chemotherapy and were in first complete remission but did not receive NK cells. Donor NK cell kinetics were determined as secondary endpoints. Twenty-one patients (median age at diagnosis, 6.0 years [range, 0.1–15.3 years]) received a median of 12.5 × 106 NK cells/kg (range, 3.6–62.2 × 106 cells/kg) without major side effects. All but 3 demonstrated transient engraftment with donor NK cells (median peak donor chimerism, 4% [range, 0–43%]). KIR–HLA-mismatched NK cells expanded in 17 patients (81%) and contracted in 4 (19%). However, adoptive transfer of NK cells did not decrease the cumulative incidence of relapse (0.393 [95% confidence interval: 0.182–0.599] vs. 0.35 [0.209–0.495]; P = .556) and did not improve event-free (60.7 ± 10.9% vs. 69.1 ± 6.8%; P = .553) or overall survival (84.2 ± 8.5% vs. 79.1 ± 6.6%; P = .663) over chemotherapy alone. The lack of benefit may result from insufficient numbers and limited persistence of alloreactive donor NK cells but does not preclude its potential usefulness during other phases of therapy, or in combination with other immunotherapeutic agents.Trial registrationwww.clinicaltrials.gov, NCT00703820. Registered 24 June 2008.

Reduced Intensity Conditioned Bone Marrow Transplant with Post-Transplant Cyclophosphamide and Donor-Derived Mesenchymal Stromal Cell Infusions for Recessive Dystrophic Epidermolysis Bullosa

Introduction: Recessive dystrophic epidermolysis bullosa (RDEB) is a severe, life-limiting systemic genodermatosis, characterized by COL7A1 mutation(s) yielding inadequate type VII collagen to maintain the integrity of the cutaneous basement and mucosal membranes. The mainstay of therapy for RDEB is supportive care to minimize the daily morbidity of blistering/scarring, pain/pruritis, systemic inflammation, and high metabolic demand. Leveraging the pluripotency of bone marrow cells, investigations of BMT as a systemic therapy for RDEB showed promise in pre-clinical murine (Tolar J, et al., Blood 2009, 113(5): 1167-74) as well as early phase human clinical trials utilizing fully myeloablative conditioning (Wagner J, et al., NEJM 2010, 363(7): 629-39). However, regimen-rated toxicity limited dampened enthusiasm for the clinical approach.Methods: In an effort to modulate disease activity with decreased toxicity, we investigated the safety of and preliminary responses to BMT with a reduced-intensity conditioning regimen (rabbit anti-thymocyte globulin 2.5 mg/kg with a methylprednisolone taper, cyclophosphamide 28 mg/kg, fludarabine 150 mg/m2, and low dose total body irradiation 300-400 cGy). Graft-versus-host disease (GvHD) prophylaxis included post-transplant cyclophosphamide (PTCy, 50 mg/kg recipient weight/dose on days +3 and 4) and mycophenylate mofetil from day +5 to 35. All except HLA-matched related donor recipients received tacrolimus from day +5 until tapered at day +100. Immunomodulatory donor-derived mesenchymal stromal cells (MSCs, 2 x 106 cells/kg recipient weight/dose) were infused at 60, 100 and 180 days post-BMT. Skin biopsies, medical photography, and dynamic assessments of RDEB disease activity by providers and parents were completed at baseline, day +100, +180 and 1 year post-BMT.Results: Ten RDEB patients were transplanted at a median age of 9.9 years (range 1.8 to 22.1), with a median follow-up of 16 months (1 year evaluations available for only 4 of 10). Donors were haploidentical related (n=6), HLA-matched related (n=3), and HLA-matched unrelated (n=1). BMT complications included graft failure in 3 patients (2 elected to pursue a 2nd PTCy BMT), veno-occlusive disease in 2, posterior reversible encephalopathy in 1, and chronic GvHD in 1, the latter deceased. Infectious complications in the first 100 days were limited to 3 viremia, 7 bacteremia, and 0 fungemia episodes. No serious adverse events were observed with MSC infusions. In the 9 ultimately engrafted patients, median donor chimerism at day +180 was 100% in both myeloid and lymphoid fractions of peripheral blood and 27% in skin. Skin biopsies at day +180 show stable (n=7) to improved (n=2) type VII collagen protein expression by immunofluorescence (IF) and gain of anchoring fibril components by transmission electron microscopy in 4 of 9 patients. Early clinical response included a trend toward reduced body surface area of blisters/erosions from a median of 45.5% at baseline to 27.5% at day +100 (p=0.05), with parental measures indicating stable quality of life. Select medical photography and skin biopsy results are shown for Patient 1 [IF: 40x merged dapi (blue) and C7 collagen antibody (red); immunoelectron microscopy with C7 collagen-directed immunostain (black)].Conclusions: BMT using reduced-intensity conditioning, PTCy and donor-derived MSC infusion for RDEB was largely well tolerated with low rates of GvHD and death from regimen-related toxicity in 1 of 10 patients undergoing 12 total BMTs. Early follow-up suggests this treatment modulates RDEB disease activity but requires longer follow-up for evaluation of efficacy. Importantly, the PTCy BMT platform provides a means of attaining immunotolerance for future donor-derived cellular grafts. [Display omitted] DisclosuresWagner:Magenta Therapeutics: Consultancy, Research Funding; Novartis: Research Funding.

Familial Haploidentical (FHI) Allogeneic Stem Cell Transplantation (AlloSCT) Utilizing CD34 Enrichment and PB MNC Addback in Children and Adolescents with High Risk Sickle Cell Disease (SCD): Rapid Engraftment, Immune Cell Reconstitution, and Sustained Donor Chimerism (IND 14359)

▪Background: SCD is characterized by chronic vaso-occlusive crises and multiorgan failure resulting in poor quality of life and early mortality (Bhatia/Cairo et al, BMT 2014). There is presently no curative therapy for patients with high risk SCD other than HLA-identical sibling AlloSCT. (Freed/Cairo et al BMT 2012). However, less than 15% of eligible SCD patients have an unaffected MSD with a 10-15% increase of graft failure and TRM (Talano/Cairo et al, EJH, 2015). Similarly, most patients lack a matched related donor and UCB is an inferior source in SCD recipients (Radhakrishman/Cairo et al, BBMT 2013). Haploidentical familial donors with SCD trait offers an opportunity for a new donor source for children with high risk SCD. To overcome HLA barriers, Geyer/Cairo et al (BJH, 2012) demonstrated that T cell depletion using CD34 enriched HPC products with PB MNC addback transplanted in pediatric recipients utilizing MUD was associated with sustained engraftment, low risk of aGVHD but limited by delayed immune reconstitution. Efforts to use FHI donors and T replete AlloSCT in patients with SCD were associated with high rates of graft failure (Bolanes-Meade J et al Blood 2012; Ruggieri et al BBMT 2011). We previously reported FHI CD34 enriched/PB MNC addback AlloSCT is feasible and well tolerated in patients with high risk SCD (Abikoff/Cairo, ASBMT 2015).Objective: To characterize immunological reconstitution following FHI AlloSCT with CD34 enriched grafts with PB MNC addback in children and adolescents with high risk SCD.Methods: 15 patients were evaluatedpretransplant at D+30, 60, 100 and 180 following FHI AlloSCT. GCSF mobilized HPC were collected by apheresis (Spectra OPTIA, Terumo BCT) and products underwent CD34 enrichment using the CliniMACS cell separation system (materials generously supplied by Miltenyi Biotec, Cambridge , MA) with a PB MNC addback dose of 2x10*5 CD3/kg. Immune cell and subset reconstitution was assessed by flow cytometry. NK function was determined by cytotoxic activity against K562 tumor targets at 10:1 E:T ratio by europium release assay and intracellular LAMP-1 (CD107a) and granzyme B expression by flow cytometry. Whole blood, T cell and RBC chimerism (CD71) determined by flow cytometry and by STR.Results: Patients achieved neutrophil and platelet engraftment in a median time of 10 and 16 days, respectively. By D+30, median whole blood donor chimerism was ≥93% and ≥95% at most recent followup (D+30-730). Median donor chimerism in the erythroid lineage was 95% by D+60, with 7 of 13 patients ≥99% at D+30. This was maintained at most recent followup (D+30-730). Median T cell chimerism was 90% (D+60-550) and median NK cell chimerism was 90% by D+30 and maintained at ≥95% through D+730. NK (CD3-/56+) and NKT (CD3+/56+) cell reconstitution following FHI AlloSCT was rapid and peaked at D+30 (35.5±8.6%, 271x10*3/ul; 14.2±4%, 179x10*3/ul, respectively). Moreover, there was robust NK cell receptor expression reconstitution with high levels of activating receptors, NKp46, NKG2D and KIR2DS and inhibitory receptors NKG2A, CD94 and KIR2DL2/3 at D+30 [Fig 1]. NK cytotoxicity against K562 at E;T 10:1 peaked at D+30 (26±3%) and D+180 (28±3%) compared to pretransplant (16±2%, p<0.01). NK activation marker, CD107a, peaked at D+30 (37±9%) and D+180 (41±6%) and there was robust granzyme B degranulation at D+30. CD3+, CD4+, CD8+ and CD19+ immune reconstitution occurred between D+180 and D+270. One year absolute (mean±SEM) cells/ul of CD3+, CD4+, CD8+, CD19+ and CD56+ was 795±168, 408±102, 375±90, 815±352 and 204±37, respectively. [Fig 2]Conclusion: Immune reconstitution and donor chimerism was relatively rapid after FHI AlloSCT with CD34 enriched grafts with PB MNC addback in high risk SCD patients. The donor MNC addback after CD34 selection may in part contribute to rapid engraftment and immune reconstitution along with sustained donor chimerism.This research was supported by FDA grant 5R01FD004090. [Display omitted] [Display omitted] DisclosuresCairo:Celgene: Research Funding.

Allogeneic Stem Cell Transplantation Using In Vivo T-Cell Depletion in Myeloid Disorders

Introduction:Alemtuzumab is used for in vivo T-cell depletion to reduce graft versus host disease in allogeneic Stem Cell Transplantation (SCT). Profound lymhotoxicity of this monocloncal antibody can potentially increase morbidity and mortality in SCT due to excessive viral infections and increased risk of graft rejection. We retrospectively analysed outcome of patients with myeloid disorders (acute myeloid leukaemia and myelodysplasia) who received in vivo T-cell depletion using Alemtuzumab based conditioning for allogeneic SCT over a period of 3 years in our centre.Methods:Patients were identified from department transplant data base. Data was collected for 73 consecutive patients over a period of three years using patient medical records, clinical work station and electronic patient records. The conditioning regimen included Fludarabine 30mg/m2 x5 (days -7 to -3), Alemtuzumab 10mgx5 (days -8 to -4) and Melphalan 140mg/m2 (day -2). Chimerism analysis was performed by polymerase chain reaction (PCR) to identify short tandem repeats within peripheral blood leucocytes and CD3 fraction. The quantification of donor chimerism was done by using gel photography system and LabWroks software. Viral testing was performed by PCR analysis.Results:Median age for the patients was 59 years (range 41-71). Median duration of follow up was 19 months (4-49 months). The majority of patients (67%) received SCT from a voluntary unrelated donor. Sixty four patients (88%) had AML whilst 9 had myelodysplasia. Sixty five (89%) patients were in morphological complete remission (<5% blasts) at the time of SCT. Median HCT-Comorbidity index was 2 (range 1-5). Median time to neutrophil engraftment was 13 days (range 9-23) and platelet engraftment 14 days (median 8-48). During the course of transplantation, 50 patients were treated for neutropenic fever with broad spectrum antibiotics and 16 for presumed fungal infection. Forty three patients (59%) reactivated cytomegalovirus (CMV), 10 (13%) had Ebstein Barr Virus (EBV) viremia and 4 (5%) were found to have adenovirus on peripheral blood PCR analysis after SCT. Denovo acute graft versus host disease (grade 2-4) required treatment in 12 patients (16%) whilst chronic GVHD was seen in 14% (n=10). 20 patients required donor lymphocyte infusion due to mixed chimerism after SCT. Total incidence of acute GVHD (grade 2-4) was 23% (n=17) and that of chronic GVHD was 15%. Median donor chimerism in peripheral blood leucocyte fraction was 100% at day 30, 60, 90 and 180 after SCT. Chimerism analysis on CD3 compartment showed 100%, 96%, 95.5% and 95% donor fraction respectively at these time points. Predicted overall survival at 2 years was 53% and Event Free Survival 49%. Non relapsed mortality in this cohort was 18% at one year. One patient had primary graft rejection with no secondary graft rejections. Overall survival was not statistically different between those who were treated for viremia (CMV, EBV, adenovirus) when compared to those who did not have viremia (p=0.31). No deaths were attributed to either CMV or EBV.Conclusion:Our retrospective data show that Alemtuzumab based conditioning regimen in myeloid disorders have low incidence of GVHD, very low risk of graft rejection and comparable overall survival to those conditioning regimens which utilize in vivo T-cell depletion strategies other than Alemtuzumab. Moreover, a high incidence of viremia, in our cohort, did not translate into worse overall survival. DisclosuresSaif:Novartis: Honoraria; Alexion: Honoraria. Dignan:Jazz pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Honoraria, Speakers Bureau; Pfizer: Honoraria, Speakers Bureau; Therakos: Honoraria, Speakers Bureau. Tholouli:Jazz Pharmaceuticals: Honoraria, Speakers Bureau; MSD: Honoraria, Speakers Bureau; Pfizer: Honoraria, Speakers Bureau.

Post-Transplant Cyclophosphamide (PTCY) Versus Anti-Thymoglobulin (ATG) As Part of the Gvhd Prophylaxis for Fludarabine/Clofarabine/Busulfan Reduced Intensity Conditioning (RIC) Allogeneic Stem Cell Transplantation (allo-SCT): Influence on Early Outcomes

Introduction: Recently, theuse of high-dose post-transplant cyclophosphamide (PTCY) has contributed to reconsider T-replete haplo-identical allo-SCT because of the lower incidence of severe graft-versus-host disease (GVHD) observed in patients. However, the influence of PTCY on early outcomes has been poorly studied so far, especially in comparison to the standard use of anti-thymoglobulin (ATG) as GVHD prophylaxis.Patients and Methods: This retrospective study was conducted at the University Hospital of Nantes with the aim to compare the incidence of early outcomes (engraftment, neutrophils and platelets recovery, viral infections (HHV-6, CMV, EBV, BKv, ADV), acute GVHD, relapse or deaths and day+100 non-relapse mortality (NRM)) between patients receiving either PTCY (n=30) or ATG (n=46) as part of GVHD prophylaxis for a RIC allo-SCT. In the PTCY group, RIC was the Baltimore regimen (Luznic, BBMT 2008) in 17 patients while 9 patients received clofarabine instead of fludarabine because of a myeloid malignancy and 4 patients a sequential approach. In this group, 6 and 24 patients received 1 or 2 days of PTCY, respectively, while donors were matched (sibling n=2, unrelated n=5) in 7 cases and haplo-identical in 23, respectively. All patients received cyclosporine + MMF with PTCY as GVHD prophylaxis. In the ATG group (2 days of ATG for siblings and 10/10, 3 days for 9/10), 13, 11 and 22 patients received respectively a FB2, FB3 or CloB2 RIC regimen (Chevallier, Haematologica, 2014). Donors were siblings in 18, matched unrelated in 23 and mismatched unrelated (9/10) in 5. GVHD prophylaxis was cyclosporine alone in case of sibling donors and cyclosporine +MMF for all other cases. The characteristics of both groups (PTCY vs ATG) were similar in terms of gender (male: 63% vs 54%), type of disease (myeloid: 67% vs 63%) and disease status at transplant (complete remission: 43% vs 67%). PTCY patients were significantly younger (median age: 55.5 vs 63 years, p=0.01) and had been previously allografted in a significantly higher proportion (40% vs 4%, p=0.003). Patients were transplanted between March 2012 and April 2015 and were considered up to day+100 post-transplant. All patients received peripheral blood stem cells as stem cell source except one patient in the PTCY group who received bone marrow.Results: All patients engrafted except one in the ATG group. The median time of neutrophils recovery was similar between both groups (PTCY 18 days vs ATG 19 days, p=0.9). Conversely, median time of platelets recovery was significant higher for the PTCY group (27 vs 13 days, p<0.0001). Median donor chimerism was significantly higher in the PTCY group at day +30 on whole blood (99.9% vs 99.1%, p=0.01), and at day +60 and +90/100 on CD3+ T cells (100% vs 95.4%, p<0.0001; and 100% vs 87.4%, p=0.0002, respectively). At day+100, PTCY and ATG patients shared similar rates of acute GVHD (20% vs 26%, grade 2-4: 13% vs 22%, p=0.7), relapses (3% vs 2.1%, p=0.7), deaths (3% vs 0%, p=0.7) and NRM (3% vs 0%, p=0.7). Also similar incidences of CMV (20% vs 37%, p=0.19), BKv (33% vs 19.5%, p=0.3) and ADV (7% vs 4%, p=0.9) infections were observed between both groups. Incidence of HHV-6 reactivations was higher in the PTCY group (53% vs 19.5%, p=0.7) while ATG patients developed significantly more EBV infections (79% vs 27%, p<0.0001). Interestingly, in the PTCY group, patients who were transplanted with a matched donor did not develop any HHV-6, CMV or ADV reactivation compared to 79% (p=0.004), 21% (p=NS) and 8% (p=NS) of the patients with haplo-identical donors, respectively. Also, among patients who received 1 day of PTCY, none developed HHV-6, CMV or BKv reactivation compared to 67% (p=0.007), 25% (p=NS) and 8% (p=NS), respectively, for the patients who received 2 days of PTCY.Conclusion: When considering early outcomes, PTCY is associated with a longer time to platelets recovery and higher early median donor chimerism compared to the use of ATG for GVHD prophylaxis after allo-SCT. The dosage of PTCY and type of donor when using PTCY may also influence the occurrence of viral infections. Prospective larger studies are warranted to confirm these results in the future. DisclosuresMoreau:Celgene, Janssen, Takeda, Novartis, Amgen: Membership on an entity's Board of Directors or advisory committees.

Robust Immune Reconstitution in Children with Severe Primary Immunodeficiency after Reduced-Intensity Conditioning Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation (HSCT) is a potentially curative therapy for severe primary immunodeficiency diseases (PID), but it is still unclear what is the optimal transplant approach. To help answer this question, the stem cell transplant team at Ann & Robert H. Lurie Children’s Hospital of Chicago (formerly Children’s Memorial Hospital) evaluated the risks and benefits of a reduced-intensity conditioning (RIC) transplant approach for treatment of severe PID. Between 2000 and 2013, 42 children with severe PID were treated with allogeneic HSCT following a RIC regimen consisting of fludarabine (30mg/m2/day x 6), rabbit anti-thymocyte globulin (once daily x 4), and intravenous busulfan (once daily x 2). Total busulfan exposure, as measured by the plasma concentration-time area-under-the-curve (AUC), was targeted individually for each patient at 4000 µM*min/day in an earlier cohort (n=14), and 5000 in a later cohort (n=28). Patients were treated in an ambulatory setting and were hospitalized only for specific medical or social reasons. There were 31 male and 11 female patients. The median age at the time of transplant was 8.2 months (range 1 month-17.4 years). The median weight was 7.6 kg (range 2.5-81.5 kg). Patients were diagnosed with severe combined immunodeficiency (n=17), Wiscott-Aldrich syndrome (n=7), hyper-IgM syndrome (n=5), major histocompatibility complex II deficiency (n=3), X-linked lymphoproliferative disease (n=3), NEMO syndrome (n=2), Omenn syndrome, reticular dysgenesis, Chediak-Higashi syndrome, IPEX (immune dysregulation, polyendocrinopathy, enteropathy, X-linked) syndrome, and IPEX-like syndrome (n=1 each). Fourteen patients had related donors and 28 had unrelated donors. Twenty-eight patients received peripheral blood HSC, 12 received cord blood, and 2 received bone marrow as the source of HSC. All patients tolerated the conditioning regimen with minimal nausea, vomiting, or pain. No severe mucositis, sinusoidal occlusion syndrome, seizure, grade III/IV acute GVHD or extensive chronic GVHD were seen. In most patients, the engraftment was rapid, with ANC ≥ 500 at a median of +15 days post-transplant, following a nadir at day +10 with a median ANC nadir of 60. In the AUC 4000 cohort, 2 patients (14%) developed primary graft failure and 2 patients (14%) developed immune-mediated secondary graft failure; in the AUC 5000 cohort, 2 patient (7%) developed primary graft failure and 1 patient developed secondary graft failure after primary EBV infection. Two patients died from complications associated with primary graft failure, 2 from complications caused by EBV infections, and 2 from complications related to their underlying diseases in the early post-transplant period. Kaplan–Meier analysis shows overall and event-free survival rates of 81.9% and 73.6%, respectively, at a median follow-up of 4.3 years. Most engrafted patients have stable donor chimerism over time. At a mean of 3.5 years post-transplant, the median donor chimerism in total white blood cells was 97% and the first and third quartiles were 77% and 99%, respectively. Engrafted patients demonstrated robust immune reconstitution with B and T cell counts normalized by 3 months and 9 months post-transplant, and CD45RA+ naive T cells by 1 year. Between 1 to 4 years post-transplant, the median absolute CD4+, CD8+ and CD19+ cell counts were 1388, 976 and 720 per mm3, respectively, percentage of CD45RA+ naive CD4 and CD8 cells were 68% and 81%, and endogenous IgG and IgM levels were 840 and 97 mg/dL. T cells showed regular responses to antigen and mitogen stimulation and exhibited normal TCRVβ repertoires. Endogenous IgG levels returned to normal by day +100, and no intravenous immunoglobulin infusion was required after day +100 in all but 1 patients. Positive vaccine-specific antibody responses were seen in patients after reimmunization at 12-24 months post-transplant. Clinically, patients have normal growth and development and do not exhibit increased susceptibility to infection. Our data showed that HSCT after RIC offers an optimal treatment for severe PID by providing robust post-transplant immune reconstitution while minimizing side effects. To reduce the risk of graft failure, we recommend a targeted busulfan AUC of 5000 µM*min/day for 2 days. DisclosuresNo relevant conflicts of interest to declare.

Alemtuzumab/Low Dose Radiation Conditioning Regimen in Allogeneic Hematopoietic Stem Cell Transplantation for Adult Patients with Sickle Cell Disease (SCD)

Allogeneic hematopoietic stem cell transplantation (HSCT) can cure SCD but chemotherapy-based conditioning regimens are associated with substantial morbidity and mortality, particularly in adult patients. A chemotherapy-free, non-myeloablative HSCT with alemtuzumab 1mg/kg divided over 5 days followed by total body irradiation (TBI) 300cGy was recently developed at the National Institute of Health and obtained stable mixed chimerism and clinical cure in 90% of SCD patients receiving an HLA and ABO-matched, related HSCT. The same study was replicated in high risk SCD adult patients at the University of Illinois at Chicago.Thirteen patients aged 17 - 40 years were transplanted between November 2011 and June 2014. Indications included ≥3 vaso-occlusive crises (VOC) per year (n=7), stroke (n=4) and >1 episode of acute chest syndrome (ACS) requiring intensive care (n=2). Unmanipulated, G-CSF mobilized peripheral blood cells were collected from HLA-matched, related donors (MRD) with Hb AS (n=4) or Hb AA (n=9). Four patients had red blood cell (RBC) alloimmunization and 2/13 patients received a graft with major ABO incompatibility. The median number of CD34+ cells infused was 8.1 x 106 cells/kg. Of 13 patients, 10 had severe neutropenia for a median duration of 5 days (range: 1 - 14) and 3 patients had a platelet count < 50 x109/L requiring a platelet transfusion. All patients engrafted and are alive with a median follow-up of 337 days (range: 53 – 986). Cytokine levels involved in T-cell regulation (IL-5, IL-10, and IL-13) increased post-alemtuzumab compared to pre-HSCT levels while no differences were observed in IL-2, IL-4, IL-12 or TNF-α. One secondary graft failure occurred in a patient not compliant with sirolimus and no acute or chronic GVHD has been observed. The median donor chimerism at 1 and 6 months was 96% (range: 63 – 98%) and 84% (range: 41 – 96%), respectively, in blood mononuclear cells; and 48% (range: 20 – 97%) and 25% (range: 20 – 48%), respectively, in CD3+ T cells (Figure 1a). Median hemoglobin concentration increased from 8.4 g/dL (range: 6.6 – 12.4 g/dL) to 12.9 g/dL (range: 11.0 – 16.8 g/dL) and the median reticulocyte percentage decreased from 12.1% (range: 4.8 – 19.6%) to 1.9% (range: 1.3 – 6.2%). Changes in hemoglobin fractionation in HSCT recipients from Hb AA donors are shown in Figure 1b. No episodes of ACS or stroke have been observed following hospital discharge after HSCT. Two patients have been tapered off of sirolimus with stable chimerisms, laboratory values, and no repeat episodes of SCD-related complications.Non-myeloablative HSCT from MRD with alemtuzumab and TBI in SCD adult patients provides a clinical cure in the majority of patients with low toxicity and no transplant-related mortality. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Extended CCR5 Blockade in Graft-Versus-Host Disease Prophylaxis – a Phase II Study

Background: Blocking lymphocyte trafficking after allogeneic stem cell transplantation (alloSCT) may prevent graft-versus-host disease (GvHD) without interfering with graft-versus-tumor (GvT) activity. We previously reported that brief (up to day+30) CCR5 blockade using maraviroc (MVC, Pfizer) after reduced-intensity conditioned (RIC) alloSCT resulted in a low incidence of acute GvHD and absence of early liver and gut GvHD, although delayed GvHD still occurred. We designed a phase II study to test the hypothesis that extended administration of MVC would be feasible, safe and provide protection against late-onset GvHD without impairing immune reconstitution or GvT responses.Patients and Methods: In April 2013 we initiated a 37-patient (pt) phase II study to test an extended course of MVC in recipients of RIC alloSCT from unrelated donors. Pts receive fludarabine 120 mg/m2 and busulfan i.v. 6.4 mg/kg followed by peripheral blood stem cells. MVC 300 mg b.i.d. is orally administered from day -3 to day +90 in addition to standard prophylaxis with tacrolimus and methotrexate. The primary endpoint is the cumulative incidence of grade 2-4 acute GvHD by day 180. As of July 2014 we enrolled 20 pts at high risk for transplant-related toxicity by virtue of age (median=64, range 55–72), donor source (matched unrelated 80%, single-antigen mismatch unrelated 20%) or comorbidities (comorbidity index: low 15%, intermediate 35%, high 50%). Underlying diseases were AML (16), MDS, MPD, ALL and CTCL (1 each).Feasibility and Safety: The median follow-up on surviving patients is 5.7 months. The 3-month course of MVC was well tolerated with no increased toxicity; two pts did not complete their treatment due to early disease relapse and one patient discontinued therapy due to a skin reaction with eosinophilia where the histological features favored a drug reaction and the attribution to MVC was possible. Postural hypotension, a known dose-dependent toxicity, was observed in one pt who completed the course with a 50% dose reduction.Engraftment and Immune Reconstitution: The median time to ANC>500/μL was 12 d (range 10-21) and platelets>20k/μL was 14 d (range 9-28). The median whole blood and T-cell donor chimerism levels at day 100 were 95% (range 12–100%) and 80% (range 23–94%) respectively, which are similar to historical rates. Median CD4 counts on day 30 were 341 (range 206-424). Only 3/16 evaluable pts had Ig levels<500 mg/dL in the first 100 days.GvHD: Sixteen pts are evaluable with > 3 mo of follow-up. The day-180 cumulative incidence rates (± s.e.) of grade 2-4 and grade 3-4 acute GvHD are 25 ± 11% and 6 ± 6% respectively (Fig. 1). Of patients who developed acute GvHD in the first 180 days, there have been no cases of liver GvHD, 2 cases of stage 1 steroid-responsive gut GvHD and 1 case of severe diarrhea with combined features of GvHD and leukemic infiltrates in the gut. These results are comparable to the GvHD rates in our phase I/II MVC study (grade 2-4: 23.6% and grade 3-4: 5.9%), which included related and unrelated donor transplants. These results also compare favorably with a 45% day-180 acute GvHD rate seen in similar patients treated with our standard GvHD prophylaxis alone. Notably, there has been no treatment-related mortality. Five patients have relapsed at a median of 2.6 months post-transplant (range 0.93 – 3.5), which is similar to our historical rates after RIC alloSCT.PD analysis: We developed a phosphoflow assay to assess in real-time the activity of MVC in fresh blood samples. The assay quantifies the activation of CCR5 by measuring the phosphorylation of C-terminal serine residues as a result of CCL4 stimulation. In 15 evaluable patients, we observed diminished pCCR5 levels with CCL4 stimulation on day 0 as compared to day -6 (Fig. 2).In summary, our preliminary results support the feasibility, safety and protective activity of the CCR5 antagonist MVC against acute GvHD, with preferential activity against visceral GvHD. Continued pt enrollment and follow-up are ongoing. Updated safety, efficacy and PD results will be presented. A multi-center study (BMT-CTN 1203) will be initiated later this year to further clarify the role of this novel strategy in improving the outcome of alloHSCT. [Display omitted] [Display omitted] DisclosuresReshef:Pfizer: Research Funding. Off Label Use: Maraviroc for graft-versus-host disease prophylaxis.

Phase II Trial of Busulfan-Based Tandem High-Dose Chemotherapy with Autologous Stem Cell Transplantation Followed By Reduced Intensity Allogeneic Stem Cell Transplantation for Patients with High-Risk Lymphoma

Many patients with high-risk lymphoma will experience relapse after autologous stem cell transplantation (AutoSCT). There are no therapies given to patients in remission after AutoSCT which are of proven benefit. At time of disease relapse after AutoSCT, patients are often considered for allogeneic stem cell transplantation (AlloSCT) if remission can be achieved by salvage strategies. We conducted a phase II clinical trial of tandem AutoSCT followed by reduced intensity conditioning (RIC) AlloSCT for patients with high-risk lymphoma. High-dose chemotherapy was BuCyE: busulfan (11.2 mg/kg IV total), cyclophosphamide (120 mg/kg IV total), and etoposide (30 mg/kg IV total). RIC AlloSCT was performed any time between 40 days and 6 months after AutoSCT if disease had not progressed. RIC was busulfan (3.2 mg/kg IV total) with fludarabine (120 mg/kg IV total) with GVHD prophylaxis comprised of tacrolimus, sirolimus, and methotrexate. A total of 42 patients were enrolled. All patients had at least a partial remission to their last therapy. Eligible patients in the up-front setting included T-cell lymphoma, mantle cell lymphoma, and B-cell lymphoma with concurrent c-MYC and BCL-2 overexpression or translocations. Other histologies were required to be relapsed / refractory as defined by number of lines of therapy or remission duration < 12 months. All patients underwent BuCyE AutoSCT. RIC AlloSCT was performed in 29 patients, 16 from a matched related donor and 13 from a matched unrelated donor. RIC AlloSCT was not performed in 13 patients because of patient choice (n=4), lack of a suitably matched donor (n=2), disease progression (n=6), and therapy-related AML (n=1). There has been no transplant-related mortality from AutoSCT. Of the 29 patients who underwent both HSCT procedures, median time from AutoSCT to AlloSCT was 96 days (range 48-169). All patients engrafted successfully with day 100 median donor chimerism being 95% (range 85-99). The 6-month cumulative incidence of grades II-IV acute GVHD was 7% (95% CI, 0.3%, 20%). Cumulative incidence of chronic GVHD at one year was 36% (17%, 56%). Non-relapse mortality at one year was 4.6% (0.3%, 20%) with one death from sepsis. Cumulative incidence of disease relapse was 20% (9%, 33%) for the entire group and 8% (1%, 23%) for patients after AlloSCT. At a median follow-up after 15.9 months (range, 3.5-36.5) after AutoSCT for the entire group, 1-yr progression-free survival was 77% (60%, 87%) and 1-yr overall survival was 87% (72%, 95%). For the 28 survivors after AlloSCT, median follow-up is 11.8 months (range, 0.2-33.6), 1-yr PFS is 87% (66%, 96%) and 1-yr OS is 95% (72%, 99%). Busulfan based tandem AutoSCT followed by RIC AlloSCT appears safe and effective in patients with high-risk lymphoma. Prospective trials comparing such a strategy to either AutoSCT or RIC AlloSCT alone in specific lymphoma subtypes are warranted.

Successful Engraftment In Children With Severe Aplastic Anemia After Transplantation Of HLA-Identical Hematopoietic Donor Cells With Shorter Telomere Length

Telomere length measurement is recommended in donors of patients with severe aplastic anemia (SAA) to screen for silent inherited telomeropathy. This was based on prior reports of delayed engraftment and graft failure after hematopoietic stem cell transplantation (HSCT) when donors had short telomeres or were silent carriers of dyskeratosis congenita (DC)-causative mutations (Fogarty et al. Lancet 2003 and Awaya et al. Biol Blood Marrow Transplant. 2002). The challenging question is, in the absence of a known causative mutation, how short the donor's telomere length could be to be labeled as not suitable. Here, we summarize our patients with SAA who have been transplanted with HLA-matched related hematopoietic donor cells that were of variable telomere length. A total of eight patients were transplanted using the following conditioning in 6 patients (cases 2, 4, 5, 6 in table, and two with undetermined telomere length) that included fludarabine (35mg/m2) on day -6 to -2, cyclophosphamide (40mg/kg) on day -6 and -5, and rabbit antithymocyte globulin (thymoglobulin) (2.5mg/kg) on day -5 to -2. GVHD prophylaxis was mycophenolate mofetil and cyclosporine (CSA). Two patients (cases 1 and 3) had cyclophosphamide (50mg/kg) on day -5 to -2 and thymoglobulin (2.5mg/kg) on day -4 to -2 with CSA and methotrexate or steroids as GVHD prophylaxis.All eight patients (5 females and 3 males) with an average age of 7 (range 0.8-13.3 years) had bone marrow failure as a predominate feature and except for one patient (case 4) who had short stature, mental retardation and a brain MRI with bilateral encephalomalacia there were no abnormal physical findings, specifically no classical features of DC i.e. nail dystrophy, leukoplakia, and skin pigmentation. All donors had normal physical examination and normal CBC. History of consanguinity was reported in all patients except one. Patients had normal chromosomal fragility test, but the telomere length values for six of the patients and their donors were in the lower reference range of healthy Caucasian individuals (Table). Three patients had very short telomeres in practically all lymphocytes subsets (cases 3, 4, and 6) similar to the pattern observed in patients with DC. The telomere length results of the six donors were variable (table). One donor had very short telomeres (case 3) in all lymphocyte subsets. The telomere length result was not available for this donor prior to commencing conditioning, however, CD34 cell dose infused was adequate (9.29 X106/kg recipient weight). Genetic tests are ongoing to identify causative mutations. One patient with undetermined telomere length had a heterozygous mutation in the TINF2 gene that was not present in his donor.All eight patients engrafted successfully, median time to neutrophil engraftment was 22 (range, 11-29 days) and platelet engraftment 30 (range, 15-62 days). Median infused nucleated cell dose was 2.8 (range, 1.6-6.5 X108/kg) and CD34 cell dose was 5.8 (range, 1.1-11.2 X106/kg). Median donor chimerism was 100% for myeloid cells and 62% for T cells around 100 days post HSCT. None of our patients had acute GVHD and one patient had mild classic chronic GVHD of the skin. All patients are alive with median follow-up duration of 377 days (range, 152-907 days).In conclusion, fludarabine-based conditioning using reduced dose cyclophosphamide (80mg/kg) seems safe and feasible in our SAA patients with shorter telomeres. Hematopoietic stem cells obtained from related donors with shorter telomeres successfully rescued patients with SAA without signs of graft failure over a median follow-up of 377 days. It is not clear yet, whether these patients and donors have an inherited telomeropathy or whether the reference range of telomere lengths established from Caucasians is also applicable for Arabs or other ethnic groups as this could possibly exclude donors unnecessarily. These studies are ongoing and an update will be presented. Disclosures:No relevant conflicts of interest to declare.

Double-Unit Cord Blood (CB) Transplantation Combined With Haplo-Identical CD34+ Cell-Selected PBSC Results In 100% CB Engraftment With Enhanced Myeloid Recovery

BackgroundDouble-unit CB transplantation (DCBT) has provided high rates of sustained donor engraftment in patients with hematologic malignancies. However, delayed engraftment is frequent with a median neutrophil & platelet recovery of 25 & 48 days, respectively, in adult DCBT recipients at our center. This delay is associated with increased transplant-related mortality (TRM). It is also associated with prolonged hospitalization with a median discharge time of +42 days (range 25-76) in recent adult myeloablative DCBT recipients. MethodsWe investigated the combined transplantation of a 4-6/6 HLA-A,-B antigen, -DRB1 allele matched double-unit CB allograft (infused on day 0) with peripheral blood stem cell derived Miltenyi column selected haplo-identical CD34+ cells (haplo-CD34+, infused on day 0 or +1) to speed myeloid recovery. We used DCB grafts to facilitate comparison with historic/concurrent DCB controls transplanted without haplo-CD34+. ResultsOf 23 protocol eligible patients, 6/23 (26%) underwent DCBT only due to the lack of any suitable haplo-identical donor. Thus, 17 patients [median 39 years (range 16-69), median 78 kg (range 63-133)] were transplanted 9/2012-6/2013 with DCB plus haplo-CD34+ cells for high-risk hematologic malignancies. Diagnoses included 12 acute leukemias & 5 lymphomas. Conditioning was myeloablative with CSA/MMF immune suppression & no ATG. Median infused CB TNC x 107/kg was 2.29 (larger unit, range 1.73-2.95) & 1.82 (smaller unit, range 1.26-2.48). Haplo-identical donors (median 37 years, range 19-71) had a median donor-recipient HLA-match of 5/10 (range 5-7). 15 patients received the targeted infused haplo-CD34+ cell dose of 3 x 106/kg whereas 2 each received haplo-CD34+ cell doses of 1 x 106/kg. The median infused haplo-CD3+ dose was 0.6 x 103/kg (range 0.3-1.6). One patient died on day 14. Of 16 remaining evaluable patients, all (100%) engrafted with a median neutrophil recovery of 13.5 days (range 11-31) in 14 patients who received 3 x 106/kg haplo-CD34+ cells, and 26 and 18 days in the 2 patients who received 1 x 106/kg haplo-CD34+ cells. Platelet recovery ≥ 20 × 109/l has occurred in 12/15 patients (median 27 days, range 18-46) to date. Serial chimerism results demonstrating the contribution of haplo-CD34+ cells & each CB unit to date is shown (Table). While myeloid recovery on day 14 was predominantly haplo-CD34+ cell mediated, one CB unit dominated by day 28 in both neutrophil & T-cell subsets. The median total donor chimerism was 100% the dominant CB unit by day 100. With a median follow-up of survivors of 5 months (range 1-10), to date 9 of 15 evaluable patients have developed grade II-IV aGVHD by day 100 (7 grade II, 1 grade III, 1 grade IV). One patient with refractory leukemia transplanted with disease has relapsed, & 4 have died of TRM (2 organ failure, 1 grade IV aGVHD, 1 CMV infection). Excluding early deaths, of patients who were discharged in the first 100 days (n = 13), the median day of discharge was day +33 (range 21-60). ConclusionsDouble-unit CBT supplemented by haplo-CD34+ cells is safe. The incidence of neutrophil engraftment is high & the speed of neutrophil recovery is enhanced compared with recent DCBT controls. A shorter time of initial hospitalization (9 days) has offset the cost of the addition of haplo-CD34+ cells. It is intriguing that the dominant CB unit can rapidly reject the haplo-identical donor. This may be facilitated by omission of ATG, and the determinants of the speed of haplo-donor rejection are under investigation. Whether the same results could be achieved with a single CB unit plus haplo-CD34+ cells requires investigation. Addition of haplo-CD34+ cells is also an alternative to expansion, although expansion remains an important strategy to augmenting myeloid recovery given some patients do not have any suitable haplo-identical donors. Disclosures:No relevant conflicts of interest to declare.