Primary Engraftment Research Articles

Interim Results of a Phase 2 Clinical Trial Using Mb-IL21 Ex Vivo Expanded NK Cells to Enhance Graft Versus Leukemia Effect for Patients with Myeloid Malignancies after Haploidentical Transplantation

▪Background: Disease relapse has emerged as the most common cause of treatment failure after transplantation. Natural killer (NK) cells have potent antitumor and antiviral effects. We hypothesized that multiple infusions of ex vivo expanded NK cells administered in early post-transplant will enhance graft-versus-leukemia (GVL) effect and began a phase 1/2 clinical trial in haploidentical transplant patients (clinicaltrials.gov NCT01904136).Methods: Results from the phase 1 clinical trial were recently reported. The aim was to determine the maximum tolerated dose of ex vivo expanded NK cells with a K562 expressing mb-IL21 feeder cell system in patients with myeloid malignancies (AML/MDs/CML). Patients received conditioning with melphalan 140mg/m2, fludarabine 160mg/m2 and 2GyTBI, and GVHD prophylaxis with post-transplant cyclophosphamide, tacrolimus and mycophenolate. All patients had bone marrow graft. NK cells were generated from peripheral blood mononuclear cells of the same donor and infused fresh on Day -2, and cryopreserved on Day +7 and +28 (up to 90). Having an NK-cell alloreactive donor or certain KIR genotype was not a requirement to participate in this study, although these characteristics were evaluated in all patients. In the phase 1 study dose escalation patients received NK cells starting at 1x105 to 1x108/Kg/dose for 3 doses. No dose limiting toxicities were observed in the phase 1 study. 1x108/kg/dose was chosen for the phase 2 trial.Results: Twenty patients were treated to date, 13 on the phase 1 study and 7 on the phase 2 part. The median age was 45 years (range 18-59), the median follow-up survivors was 16.5 months. Twelve patients (60%) were females. The median HCT-CI was 2 (range 0-8). Ten patients (50%) had AML (9 in CR1 and 1 beyond CR2), 3 (15%) had MDS (2 with induction failure, 1 untreated), and 7 (35%) had advanced CML (4 in CP2 after progression to blast-phase of which 2 in CNS, 1 in CP1, 1 clonal evolution). Of the patients with AML 4 patients with AML had poor-risk cytogenetics and 6 had intermediate with high-risk mutations except one (2 had FLT3, 2 had NRAS, 1 had ASXL1) and 3 patients had primary induction failure. Two MDS patients had complex cytogenetics and one diploid with high percent of bone marrow blasts. DRI was very high/high in 10 patients and intermediate/low in 10 patients. All patients received all 3 NK cell infusions as planned except one patient. Eight patients received the maximum dose of 1x108/kg/dose.One patient had early death due to hemorrhage. Nineteen patients were evaluable for engraftment and all achieve primary engraftment after a median time of 19 days (range 16-42). Nine of 12 female patients (75%) had donor-specific anti-HLA antibodies. Chimerism was 100% donor in all patients except one who had mixed chimerism. The cumulative incidence (CI) of all aGVHD at Day100 and 1 year post-transplant was 26.1% and 48% (3 patients had late acute GVHD), exclusively grade 2 and exclusively GI tract. No grade 3 or grade 4 aGVHD, and no chronic GVHD was observed. Also, none of the patients developed liver GVHD. The CI of TRM at 1 and 2 years post-transplant was 5.6% and 16.7%, respectively. Only one patient relapsed to date for a CI of relapse at 1 and 2 years on 5.6%. The only patient who relapsed was an advanced FLT3+AML patient (beyond CR2) who received the lowest NK cells dose. None of the patients who received ≥1x105/kg dose relapsed. The median overall survival and progression-free survival (PFS) were not reached. The 1-year and 2-years PFS was 84.4% and 74%, respectively (Figure 1). Eight of 19 patients (42%) reactivated CMV and 4 patients (21%) had grade 1 transient BKV cystitis.Conclusions: Multiple infusions of high doses of donor-derived ex vivo expanded NK cells with a K562 feeder cell system and mbIL-21 administered early post-transplant are safe and are associated with low relapse rate and low incidence of viral reactivation. A randomized trial is needed to confirm these results. [Display omitted] DisclosuresOran:Celgene: Research Funding; AROG: Research Funding; Astex: Research Funding. Lee:Courier Therapeutics, Inc: Membership on an entity's Board of Directors or advisory committees; Cyto-Sen Therapeutics, Inc: Other: Founder, Vice President, Medical Director; Intellia Therapeutics, Inc: Consultancy; Miltenyi: Speakers Bureau.

First-Line Choice for Severe Aplastic Anemia in Children: Transplantation from a Haplo-Identical Donor Versus Immunosuppressive Therapy

Background: Severe aplastic anemia (SAA) is a fatal disorder in children if treated inappropriately. According to the current algorithm, transplantation from a matched related donor (MRD) is recommended as the first-line option in children with SAA, if a MRD is unavailable, IST with a combination of anti-thymocyte globulin (ATG) and cyclosporine (CsA) represents the first-line choice. However, numerous limitations of immunosuppressive therapy (IST) exists. IST children may have incomplete recovery, and appear to be associated with an increased risk of clonal evolution and subsequent relapse. Additionally, the unavailability of horse-ATG in China also make the response of IST at a discount greatly. At the same time, great progresses in recent years in haploidentical transplantation might also promote changes in the algorithm of SAA treatment.Methods: We retrospectively compared the outcomes of children with SAA who received IST or who underwent hematopoietic stem cell transplantation (HSCT) from a haplo-identical donor (HID) as first-line choice between 2007 and 2016. The conditioning regimen for SCT from a haploidentical donor consisted of intravenous busulfan, cyclophosphamide and rabbit ATG. All of children were administered with granulocyte colonystimulating factor (G-CSF)-primed bone marrow (BM) combined with G-CSF-primed peripheral blood (PB) hematopoietic stem cells.Results: A total of 52 SAA children under the age of 17 years were initially treated with IST (n=24) or haplo-identical HSCT (n=28) as first-line choice. The last follow-up for all surviving patients was June 1, 2017. In IST group, by 6 months, 15 of the 21 subjects (71.4%) improved with first-line IST and achieved a partial response (n=10) or complete response (n=5). In SCT group, 27 patients (96.4%) achieved primary engraftment at a median of 12 (range, 10-21) days except one suffered from primary graft failure. The cumulative incidences (CI) of grade II-IV and of grade III-IV acute graft versus host disease (GVHD) were 48.1±1.0% and 11.1±0.4%, respectively. The 3-year CI of extensive chronic GVHD was 3.7±0.1%. The estimated 10-year overall survival were 73.4±12.6% and 89.3±5.8% in patients treated with IST or HID-HSCT (P=0.806). However, the failure-free survival was significantly inferior in patients receiving IST than in those undergoing transplantation from a HID [52.6±10.5% versus 89.3±5.8, P=0.008]. In univariate analysis, the choice of first-line immunosuppressive therapy was the only adverse predictor for failure-free survival. At the last follow-up, completely normal blood count was observed in 11 of 20 (55.0%) and 24 of 25 (96.0%) alive cases in IST and HID-HSCT cohort (P=0.003).Conclusions: Based on the superior FFS, high rate of engraftment and acceptable incidence of GVHD, the choice of HID HSCT for SAA children without a matched related donor as a first choice option seems reasonable. These suggest that SCT from a haplo-identical donor could be considered as first-line choice in children who lack a matched related donor, especially in experienced transplantation centers. DisclosuresNo relevant conflicts of interest to declare.

Supplement Yogurt for Patients during Early Phase of Unrelated Cord Blood Transplantation: A Safety and Feasibility Pilot Study

Background: During last few years, intestinal microbiota, as a vital biological regulatory substance after hematopoietic stem cell transplantation (HSCT), has been attached with growing importance. Probiotics in yogurt may have positive effect in protecting intestinal microbiota diversity and improving the prognosis of patients after HSCT. However, the safety of supplement yogurt has not been evaluated in the early phase of HSCT. In order to evaluate the safety and feasibility of yogurt, we conducted a pilot study in patients who had undergone unrelated cord blood transplantation (UCBT).Method: Between February and June 2017, patients receiving UCBT was divided into two groups randomly. The experimental group (20 patients; mean age 17y, r 1-59; male 11) and control group (26 patients; mean age 24.3y, r 1-59; male 12) have no significant differences in age, gender, weight, underlying diseases and conditioning intensity (Table 1). Patients in experimental group (n=20) take in 200ml yogurt while children take in 100ml every day on day -7 and continue until day +30 (xinxiwang yogurt, including lactobacillus bulgaricus, streptococcus thermophilus, lactobacillus plantarum, lactobacillus rhamnosus, the number of lactobacillus≥108CFU/100g, produced at Jinrong Road 33rd, Shuangfeng economic industrial zone, Changfeng, Hefei, Anhui), while patients in control group (n=26) taking in nothing. All patients received CsA plus mycophenolate mofetil as GVHD prophylaxis.Results: we compared some indicators related to UCBT between the two group (Table 2). The primary engraftment rate is 95.0% (experimental group) and 96.2% (control group). The mortality in 60 day is 10% and 7.7% and the median time to 0.5×109/L ANC was 17 days (r 12-30) and 18.5 days(r 12-24). The incidence of acute GVHD gradeⅠ-Ⅳ (55.0% vs.57.7%, P= 0.972), bacteremia (45.0% vs.46.2%, P= 0.972), diarrhea (35.0% vs.53.8%, P= 0.444), and pre-engraftment syndrome (55.0% vs.80.8%, P= 0.154) show no significant differences between two group. While, the continuous change of CRP (P= 0.343), weight(P= 0.738), and albumin(P= 0.345) from day -7 to day +30 is also no significant difference between two groups. We don't observe any case of lactobacillus bacteremia (0%) in experimental group, together with none occurrence of lactobacillus-related unexpected adverse events through the whole study.Conclusion: Our data show it is safe and feasible to supplement yogurt during early phase of unrelated cord blood transplantation. It will not result in an increasing related risks including infection, diarrhea, aGVHD, and also not influence the nutritional status of patients. However, due to the limitation of the number of cases and short observation duration, we can not evaluate the effectiveness of the supplement yogurt. Further conclusion requires larger sample size and longer observation duration.No conflict of interest to declare. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Unmanipulated Haploidentical Transplant for Acquired Severe Aplastic Anemia Achieved Comparable Outcomes with Unrelated Donor Transplant in Adult and Children Patients

Background: Salvage BMT is considered for patients with refractory SAA if an HLA-matched unrelated donor (URD) is available, but many patients, especially minorities, are unable to find an URD in the registry . Donor availability has remained an important limitation to the success of BMT in SAA . Haploidentical donor(HID) are available for nearly all patients and can be performed immediately particularly crucial for patients with vSAA who need prompt therapy .so the past ten years ,HID has been widely used as a considered donor in HSCT for SAA. but in the early years the high rate of the primary graft failure and severe GVHD limited its clinical application.However in the recent years , with advances in in vivo regulation of T-cells, optimized conditioning regimens, and improved supportive care.The results of HID-HSCT not only have significantly increased.but also in the treatment status of SAA is increasing prominence,Even in some multicenter study,HID-HSCT be used as first line treatment for newly diagnosied SAA and achieved similar outcome to MSD-HSCT. But there are not comparable studies on HID and MUD HSCT in SAA.In order to further evalued the therapeutic effect and safety of HID SCT for the SAA, We retrospectively analysed the outcomes of 89 patients with acquired SAA who had received HID and MUD HSCT between 2012and 2016 in our single center.Materials and methods: Between September 2012 and September 2016, total 89 patients with SAA who received unmanipulated alternative HSCT in our center were analyzed retrospectively.male to female was 52:37 . The median disease course from diagnosis to HSCT was 17(range,2 ∼ 192)months. The median age 11(range,2-42)years .64/89(71.9%)cases had heavy transfusion. 30/89(33.7%)patients received one course of ATG before transplant. Conditioning regimen consisted of busulfan (3.2 mg/kg per day) for 2 days; fludarabine (30 mg/m2 per day) for 4 days; cyclophosphamide (500 mg/m2 per day) for 4 days; and either ATG (Thymoglobuline, SANOFI, total dose 7.5 mg/kg in 42 cases; ATG-F, total dose 20 mg/kg in 47 cases) .For GVHD prophylaxis, Tacrolimus, MMF and MTX were used in all patients .Results: Fourty-seven patients received haploidentical donors HID, and Fourty -two patients received URD for HSCT.The median times for myeloid engraftment in the HID and URD cohorts were 14 (range, 10-21) and 13 (range, 10-18)days respectively . all patients achieved primary engraftment .HID recipients had an increased cumulative incidence of grades II-IV acute GVHD (43.9± 3.48% vs 12.5± 5.52%,P=0.001), and chronic GVHD at 1 year (48.8± 3.11% vs 31.2± 2.81%.P=0.038) but similar extensive cGVHD (14.6± 2.60% vs 8.3±2.37%.P=0.244). The surviving patients with a median follow-up 26 (6-45) months, three-years overall survival (OS) was 87.8±1.46%. There were no significant differences between HID and MUD cohorts in three-year estimated OS [82.9±2.39% vs 91.7±1.70%,P=0.210], and also similar in the three-year estimated failure-free survival (FFS) [80.5±2.49% vs 91.7±1.70%,P=0.127] and GVHD free survival (GFS) [82.9±2.45% vs 81.3±2.26%,P=0.976] respectively. In multivariate analysis, survival outcome for the entire population was significantly adversely associated with VSAA (SAA vs VSAA,P=0.003) and with Ⅱ ∼ ⅣaGVHD (Yes vs No,P=0.001).but have no difference in age(< 18 years vs ≥18 years,P=0.045);disease course before HSCT(< 17 months vs ≥17 months,P=0.031);Previous Therapy before HSCT(received ATG or not, P=0..21); heavily pre-transfused before(Yes vs No,P=0.31);Type of ATG(ATG-F vs Thymoglobuline,P=0.34 );donor-patient sex match(p=0.54);donor-patient ABO blood type (P=0.23).Conclusion: This study showed favorable outcome of Haplo-HSCT for SAA, which was comparable with UD-HSCT.Haploidentical donor can be an important alternative donor. DisclosuresNo relevant conflicts of interest to declare.

HLA-haploidentical TCRαβ+/CD19+-depleted stem cell transplantation in children and young adults with Fanconi anemia

AbstractWe report on the outcome of 24 patients with Fanconi anemia (FA) lacking an HLA matched related or unrelated donor, given an HLA-haploidentical T-cell receptor αβ (TCRαβ+) and CD19+ cell-depleted hematopoietic stem cell transplantation (HSCT) in the context of a prospective, single-center phase 2 trial. Sustained primary engraftment was achieved in 22 (91.6%) of 24 patients, with median time to neutrophil recovery of 12 days (range, 9-15 days) and platelet recovery of 10 days (range, 7-14 days). Cumulative incidences of grade 1 to 2 acute graft-versus-host disease (GVHD) and chronic GVHD were 17.4% (95% confidence interval [CI], 5.5%-35.5%) and 5.5% (95% CI, 0.8%-33.4%), respectively. The conditioning regimen, which included fludarabine, low-dose cyclophosphamide and, in most patients, single-dose irradiation was well tolerated; no fatal transplant-related toxicity was observed. With a median follow-up of 5.2 years (range, 0.3-8.7 years), the overall and event-free survival probabilities were 100% and 86.3% (95% CI, 62.8%-95.4%), respectively (2 graft failures and 1 case of poor graft function were considered as events). The 2 patients who experienced primary graft failure underwent a subsequent successful HSCT from the other parent. This is the first report of FA patients given TCRαβ+/CD19+-depleted haplo-HSCT in the context of a prospective trial, and the largest series of T-cell–depleted haplo-HSCT in FA reported to date. This trial was registered at www.clinicaltrials.gov as #NCT01810120.

Serotherapy-Free Regimen Improves Non-Relapse Mortality and Immune Recovery Among the Recipients of αβ TCell–Depleted Haploidentical Grafts: Retrospective Study in Childhood Leukemia

Depletion of αβ T cells from the graft prevents graft-versus-host disease (GVHD) and improves the outcome of hematopoietic stem cell transplantation (HSCT) from haploidentical donors. Delayed recovery of adaptive immunity remains a problem, which can be approached by adoptive T-cell transfer. In a randomized trial, we have assessed the safety and efficacy of low-dose memory (CD45RA-depleted) donor lymphocytes (mDLI) after HSCT with αβ T-cell depletion. Antithymocyte globulin (ATG) is viewed as an essential component of preparative regimen, critical for both prevention of graft failure and GVHD. Variable pharmacokinetics of ATG may significantly affect lymphocyte subpopulations after HSCT. To uncover the potential of mDLI, we replaced rabbit ATG with tocilizumab and abatacept. Here we compare post hoc the immune recovery and the key clinical outcomes, including nonrelapse mortality (NRM), overall- and event-free survival (OS and EFS), between the cohort enrolled in the prospective randomized trial and a historical cohort, comprised of patients grafted with a conventional ATG-based HSCT with αβ T cell depletion. A cohort of 149 children was enrolled in the prospective trial and 108 patients were selected as historical controls from a prospectively populated database. Patient population was comprised of children with high-risk hematologic malignancies, with more than 90% represented by acute leukemia. Median age at enrollment was 8.8 years. In the prospective cohort 91% of the donors were haploidentical parents, whereas in the historical cohort 72% of the donors were haploidentical. Conditioning was based on either 12Gy total body irradiation or treosulfan. Thiotepa, fludarabine, bortezomib, and rituximab were used as additional agents. Patients in the historical cohort received rabbit ATG at 5 mg/kg total dose, while prospective cohort patients received tocilizumab at 8 mg /kg on day -1 and abatacept at 10 mg/kg on days 0, 7, 14, and 28. Patients in the prospective trial cohort were randomized 1:1 to receive mDLI starting on day 0, whereas 69% of historical cohort patients received mDLI after engraftment, as part of previous trials. Primary engraftment rate was 99% in the prospective cohort and 98% in the historical cohort. The incidence of grade II-IV aGVHD was 13% in the prospective cohort and 16 % in the control group. Chronic GVHD developed among 13% (historical) and 7% (prospective) cohorts (P=.07). The incidence of cytomegalovirus viremia was 51% in the prospective cohort arm and 54% in the historical control arm (p=ns). Overall, in the prospective cohort 2-year NRM was 2%, incidence of relapse was 25%, EFS was 71%, and OS was 80%, whereas in the historical cohort 2-year NRM was 13%, incidence of relapse was 19%, EFS was 67%, and OS was 76%, difference non-significant for relapse and survival. NRM was significantly improved in the ATG-free cohort (P=.002). Recovery of both αβ- and γδ- T cells was significantly improved at days +30 and +60 after HSCT in recipients of ATG-free preparative regimens, as well as recovery of naïve T cells. Among the recipients of αβ T-cell-depleted grafts, replacement of ATG with nonlymphodepleting abatacept and tocilizumab immunomodulation did not compromise engraftment and GVHD control and was associated with significantly lower NRM and better immune recovery early after HSCT.

Long-term results of allogeneic peripheral blood hematopoietic stem cell transplantation for severe aplastic anemia

ObjectiveAplastic anemia (AA) is a life-threatening disorder and may be associated with significant morbidity and mortality Currently, the first treatment option is allogeneic hematopoietic stem cell transplant (allo-HSCT) for patients younger than 40 years. Bone marrow is recommended as the stem cell source due to less graft versus host disease (GVHD) risk and better outcomes than peripheral blood (PB)-derived stem cell. The aim of this study is to share the data of AA patients who have underwent PB-derived allo-HSCT in our bone marrow transplantation center. MethodsTwenty-seven patients who underwent PB-derived allo-HSCT from human leukocyte antigen matched sibling donors were analyzed retrospectively. ResultsThe median follow-up time was 95.2 months (range, 4.8–235 months). The 10-year survival was 89 %. The median neutrophil and platelet engraftment time was 11 days (range, 9–16 days) and 13 days (range, 11–29 days), respectively. Primary platelet engraftment failure was observed in 1 patient (3.7 %). Acute and chronic GVHD observed in 2 (7.4 %) and 3 (11.1 %) patients, respectively. Neutropenic fever was observed in 13 (44.8 %) of patients until the engraftment after allo-HSCT. One patient died due to CMV infections, two died due to septic shock secondary to fungal infection. ConclusionAlthough there is no prospective data directly comparing BM with PB as stem cell source in AA, observational studies indicates better OS with BM. PB can be used in certain situations such as higher risk for graft failure and donor preference. This study demonstrated that PB-derived stem cell seems to be a reasonable alternative to BM.

Outcome of Children with Different Non-Malignant Disorders Given Alphabeta T and B-Cell Depleted HLA-Haploidentical Hematopoietic Stem Cell Transplantation (TBdepl-haploHSCT)

Background: allogeneic HSCT is the only potentially curative treatment for many non-malignant diseases (NMD), either inherited or acquired. However, many patients lack an HLA-matched donor (familiar (MFD) or unrelated (MUD)) and the outcome of children transplanted from an HLA-haploidentical relative (haplo) was historically inferior to that of transplants from a MFD or a MUD. We previously published promising results in a cohort of 23 children with NMD given this type of allograft (Bertaina et al., Blood 2014), demonstrating a low transplant-related mortality (TRM) and high cure rates. Here, we report the outcome of a large cohort of children affected by NMD who received a TBdepl-haploHSCT at our Center (NCT01810120). Patients and methods: Between February 2011 and June 2020, 80 consecutive patients affected by NMD received TBdepl-haploHSCT from an HLA-partially matched relative at Ospedale Pediatrico Bambino Gesù in Rome, Italy. Patients had many different disorders (see Table for details on patient- and transplant-related characteristics). Median time from diagnosis to transplant for the whole cohort was 12 months (range 1-177), while it was 2.5 months (range 1.3-11.2) for SCID patients. All patients, including children with SCID, received a conditioning regimen, which varied according to the original disease. Pre-transplant anti-thymocyte globulins (from day -4 to day -2) were given to modulate bi-directional donor/recipient alloreactivity, while rituximab (on day -1) was administered to prevent PTLD. Moreover, no post-transplant pharmacological GvHD prophylaxis was given. Results: fifty-eight patients (72.5%) achieved primary donor cell engraftment, while 3 patients experienced secondary graft failure (GF); the cumulative incidence of either primary or secondary GF was 27.8% (95% CI 17.2-37.0). Median time to neutrophil and platelet recovery was 13.5 (range 9-33) and 10 days (range 7-51), respectively. As expected, GF occurred more frequently in children with disorders known to be associated with an increased GF risk (i.e., HLH, thalassemia, SAA or osteopetrosis) (see also Figure 1A). Three children (4%) experiencing GF died because of infectious complications before retransplant. Sixteen of the 22 patients with either primary or secondary GF were successfully retransplanted (2 with a mismatched unrelated cord blood unit, the other having received a second TBdepl-haploHSCT from either the same donor or the other parent). Since 3 other patients died [all because of infectious complications, 2 due to disseminated adenovirus infection and 1 to CMV pneumonia)], TRM is 7.8% (95% CI 1.6-13.7). Eighteen patients experienced acute GVHD of any grade, the cumulative incidence of this complication being 22% (95% CI 13.5-31.8); 10/18 patients developed grade II acute GVHD (no patient developed grade III or IV aGVHD), this resulting into a cumulative incidence of 12.9% (95% CI 6.6-21.4). Only one patient at risk developed mild chronic GVHD. Twenty-two and 7 patients developed clinically-relevant (i.e., with a viral load &amp;gt; 1000 copies/ml and/or requiring specific antiviral-treatment) CMV and adenovirus infection, respectively, at a median time of 4 (range 0-16) and 1 (range 1-4) weeks from HSCT. Time averaged area under the curve (i.e., viral burden under the curve/weeks at risk for infection) for CMV and ADV are reported in Figure 1B. With a median follow-up of 36 months (range 2 - 110), the 5-year probability of overall survival and event-free survival for the entire cohort of patients is 92.1% (95% CI 83.3-96.4) (Figure 1C) and 68.1% (95% CI 56.4-77.2), respectively. Considering the 16/22 given a successful 2nd allograft, the 5-year disease-free survival is 88.4% (95% CI 78.9-93.8). Details on reconstitution of CD3+, CD4+ and CD8+ lymphocytes are reported in Figure 1D. Conclusions: TBdepl-haploHSCT is an effective option for children with different NMD. GF (either primary or secondary) is a challenging problem in a sub-group of patients at risk (i.e., those with HLH, thalassemia, SAA or osteopetrosis): thus, new strategies to overcome this problem are desirable. However, a second transplant is able to rescue most of these patients. Prompt availability of this type of transplant, limiting infectious risk, low incidence of both acute and chronic GvHD preserving a good quality of life in patients makes this strategy an attractive choice in patients with NMD. Figure 1 Disclosures Merli: Bellicum Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; SOBI: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz: Honoraria; Sanofi-Genzyme: Honoraria; Atara Therapeutics: Honoraria. Algeri:BlueBird Bio: Membership on an entity's Board of Directors or advisory committees; Atara Therapeutics: Membership on an entity's Board of Directors or advisory committees. Locatelli:Jazz Pharmaceeutical: Speakers Bureau; Medac: Speakers Bureau; Miltenyi: Speakers Bureau; Bellicum Pharmaceutical: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

Comparison of Frontline Haploidentical Hematopoietic Stem Cell Transplantation and Salvage Haploidentical Hematopoietic Stem Cell Transplantation for Patients with Severe Aplastic Anemia

To compare the clinical efficacy between frontline haplo-identical hematopoietic stem cell transplantation (haplo-HSCT) and salvage haplo-HSCT for patients with severe aplastic anemia (SAA). A total of 39 patients with severe aplastic anemia or very severe aplastic anemia from May 1st, 2013 to December 31st, 2018 were analyzed retrospectively. All of them underwent bone marrow + peripheral blood hemopoietic stem cell transplantation. There were 20 cases who accepted frontline haplo-HSCT for a median course of 1 (1-3) month, and 19 cases who accepted salvage haplo-HSCT for a median course of 72 (6-168) months. Conditioning regimen: 22 cases received Flu/Cy+ATG, and 17 cases received Bu/Cy+ATG. The time of hematopoietic reconstitution, infection rate, and grade I-Ⅱ and Ⅲ-Ⅳ acute/chronic graft versus host disease showed no statistically significance between the frontline haplo-HSCT group and the salvage haplo-HSCT group. In the frontline haplo-HSCT group, 1 case (5%) failed in second engraftment, in the salvage haplo-HSCT group 2 cases (10.5%) failed in primary engraftment and 4 cases (21.1%) in second engraftment. The incidence of engraftment failure was higher in the salvage haplo-HSCT group than that in the frontline haplo-HSCT group (P=0.04). The median time of follow-up after allo-HSCT was 45 months (ranging from 3 to 92). The mortality was 10% (2/20) in the frontline haplo-HSCT group, and 42.1% (8/19) in the salvage haplo-HSCT group. The estimated 5-year failure-free survival rate (FFS) of the frontline haplo-HSCT group was higher than that of the salvage haplo-HSCT group (90% vs 57.4%) (P=0.02). The frontline haplo-HSCT is an effective and safe approach for the patients with severe aplastic anemia who lack a HLA-matched sibling donor.

Long-term results of allogeneic peripheral blood hematopoietic stem cell transplantation for severe aplastic anemia

Abstract Objective Aplastic anemia (AA) is a life-threatening disorder and may be associated with significant morbidity and mortality Currently, the first treatment option is allogeneic hematopoietic stem cell transplant (allo-HSCT) for patients younger than 40 years. Bone marrow is recommended as the stem cell source due to less graft versus host disease (GVHD) risk and better outcomes than peripheral blood (PB)-derived stem cell. The aim of this study is to share the data of AA patients who have underwent PB-derived allo-HSCT in our bone marrow transplantation center. Methods Twenty-seven patients who underwent PB-derived allo-HSCT from human leukocyte antigen matched sibling donors were analyzed retrospectively. Results The median follow-up time was 95.2 months (range, 4.8–235 months). The 10-year survival was 89 %. The median neutrophil and platelet engraftment time was 11 days (range, 9–16 days) and 13 days (range, 11–29 days), respectively. Primary platelet engraftment failure was observed in 1 patient (3.7 %). Acute and chronic GVHD observed in 2 (7.4 %) and 3 (11.1 %) patients, respectively. Neutropenic fever was observed in 13 (44.8 %) of patients until the engraftment after allo-HSCT. One patient died due to CMV infections, two died due to septic shock secondary to fungal infection. Conclusion Although there is no prospective data directly comparing BM with PB as stem cell source in AA, observational studies indicates better OS with BM. PB can be used in certain situations such as higher risk for graft failure and donor preference. This study demonstrated that PB-derived stem cell seems to be a reasonable alternative to BM.

Secondary failure of platelet recovery in patients treated with high-dose thiotepa and busulfan followed by autologous stem cell transplantation.

Autologous stem cell transplantation (ASCT) with high-dose thiotepa and busulfan is a treatment option for patients with central nervous system (CNS) lymphoma. We report here the occurrence of secondary failure of platelet recovery (SFPR) in three out of 24 patients who received high-dose thiotepa and busulfan followed by ASCT. Although there was no obvious abnormality in the primary platelet engraftment as well as the recovery of other blood cells, they developed SFPR with a median time to onset of day 38, and the platelets gradually recovered over several months with steroid therapy. During the same period, there was no development of SFPR among 50 patients who received ASCT with a conditioning regimen of MEAM (ranimustine, etoposide, cytarabine, and melphalan) or high-dose melphalan. However, one of the two patients who received a conditioning regimen of busulfan and melphalan developed SFPR, suggesting that the use of a busulfan-based conditioning regimen may be one of the risk factors for SFPR. It is important to be aware of this possible adverse effect of ASCT with high-dose thiotepa and busulfan to ensure timely diagnosis and prevention of subsequent serious complications.

Favorable outcomes of hematopoietic stem cell transplantation in children and adolescents with Diamond-Blackfan anemia

AbstractDiamond-Blackfan anemia (DBA) is a congenital pure red cell aplasia associated with congenital abnormalities and cancer predisposition. Allogeneic hematopoietic stem cell transplantation (HSCT) can correct the hematological phenotype and is indicated in transfusion-dependent patients. In 70 children reported to the German DBA and French HSCT registries, HSCT was performed from 1985 to 2017. Median age at HSCT was 5.5 years (range, 0.9-17.3 years). Two-thirds of patients (64%) were transplanted from a matched sibling donor (MSD), and most procedures were performed after the year 1999 (73%). Primary engraftment was achieved in all patients. One patient developed secondary graft failure. Cumulative incidence of acute graft-versus-host disease (GVHD) was 24% for °II-IV (95% confidence interval [CI], 16% to 37%) and 7% for °III-IV (95% CI, 3% to 17%); cumulative incidence of chronic GVHD was 11% (95% CI, 5% to 22%). The probability of chronic GVHD-free survival (cGFS) was 87% (95% CI, 79% to 95%) and significantly improved over time (<2000: 68% [95% CI, 47% to 89%] vs ≥2000: 94% [95% CI, 87% to 100%], P < .01). cGFS was comparable following HSCT from a MSD and an unrelated donor (UD). Of note, no severe chronic GVHD or deaths were reported following MSD-HSCT after 1999. The difference of cGFS in children transplanted <10 years of age compared with older patients did not reach statistical significance (<10 years: 90% [95% CI, 81% to 99%] vs 10-18 years 78% [95% CI, 58% to 98%]). In summary, these data indicate that HSCT is efficient and safe in young DBA patients and should be considered if a MSD or matched UD is available. HSCT for transfusion dependency only must be critically discussed in older patients.

A Prospective Pilot Study of Graft-versus-Host Disease Prophylaxis with Post-Transplantation Cyclophosphamide and Ruxolitinib in Patients with Myelofibrosis

Introduction: This prospective study evaluated a calcineurin inhibitor-free graft-versus-host disease (GVHD) prophylaxis regimen of ruxolitinib in combination with post-transplant cyclophosphamide (PTCy). Patents and Methods: Twenty patients with primary or secondary myelofibrosis were prospectively enrolled. Reduced intensity conditioning was performed, followed by allogeneic stem cell transplantation from related (n = 7) or unrelated (n = 13) donors. GVHD prophylaxis included only PTCy and ruxolitinib (45 mg) from day–7 to day–2, and 15 mg from day+5 to day+100. This trial was registered at www.clinicaltrials.gov as #NCT02806375. Results: Primary engraftment was documented in 17 patients. One patient experienced primary graft failure and 2 died before engraftment. Eleven patients demonstrated severe poor graft function (SPGF), which required ruxolitinib dose reduction. The regimen was well tolerated, with grade 3–4 non-haematological toxicity in 30%, viral reactivation in 45%, and severe sepsis in 15% of patients. The incidence of acute GVHD grade II–IV was 25%, grade III-IV GVHD was 15%, and moderate chronic GVHD was 20%, with no severe cases. Only 2 patients required systemic steroids. Haematological relapse was documented in 1 patient. Two-year non-relapse mortality was 15%, 2-year overall survival was 85%, and 2-year event-free survival was 72%. Conclusion: GVHD prophylaxis with PTCy and ruxolitinib is associated with low toxicity, good acute and chronic GVHD control, and low relapse incidence. However, the relatively high rate of SPGF should be taken into account. SPGF could possibly be mitigated by ruxolitinib dose reduction.

Establishment of Pediatric Bone Marrow Transplant Unit in Public Sector Hospital, a Dream Accomplished.

<h3>Background</h3> Bone Marrow Transplant (BMT) is a highly sophisticated curative treatment of many Hematological, immunological, metabolic and Oncological conditions. Pakistan is a Lower middle income country. The treatment facilities are very limited as compared to the need of the region. Our Pediatric Hematology/Oncology unit is in one of the busy center of the country. We decided to start the First ever Public sector Pediatric Bone Marrow Transplant. <h3>Objective</h3> This study was done to know & enlighten the hurdles in establishment of BMT unit in Public Sector Hospitals in LMIC. The task to start BMT was taken as a challenge in collaboration with NIBD & BMT, Karachi, Pakistan in 2016. The Physicians and other supportive Team were sent for short term training.On return the Team started renovation of old building. In next step arrangement of instrumentation was done step by step, includes Cell separators, Platelet Aphresis Machines, HEPA Filters, CBC Analyzer, Handy Electrolyte Machine, Fridge (-80C⁰) for Cryopreservations & Plasma Storage, PRBC storage fridge and Blood grouping/Cross matching reagents and Gel Cards arranged. Then two patients with Beta Thalassemia Major were selected who had full matched sibling donors. The standard Conditioning Protocol of BU/Cy/ATG with GVHD prophylaxis Steroids/MTx and Cyclosporine started after saving the Autologus Bone Marrow Harvest. The Bone Marrow Harvest was done on both donors on same day and Infusion was done. The MNC and CD34 count were appropriate. The senior team members of Pediatric Hem/Onco department were involved and senior most staff nurses had taken care of the patients along with mothers of the patients. But unfortunately one patient died of Severe Pneumonia along with Pharyngeal abscess on day +11 and the second on +25 due to Primary engraftment Failure and severe Pulmonary Hemorrhage. The initial two patient's mortality depressed the Hospital administration as well as the Treating Team. We decided to review the supportive care techniques, restricted the entry and limited the Treating staff. After getting these improvements we again decided to start the BMT unit again in March 2018 and selected Aplastic Anemia patient of 8 years who had 6/6 matched sibling donor.The five days conditioning was done with Fludarabine, Cyclophsphamide and GVHD prophylaxis with Cyclosporin, MTX and steroids. PBSC was done on cell separator and stem cell infusion done. Patient engrafted Neutrophil on +10, Platelets on +18 and RBC on +45. Th immnunosupression was tapered off 6 months post BMT and now free of medication. Since then we have done so far total 23 patients including Aplastic Anemia, Thalassemia, Fanconi Anemia.Our success rate is 60%. I know it is far behind the international data but we are thriving to improve it day by day. <h3>Conclusion</h3> The persistent struggle is needed for establishment of BMT units in LMICs. <h3>Recommendation</h3> When there is a will, there is a way.

A Prospective Phase III Trial for Comparing Cyclophosphamide and Fludarabine Conditioning Regimen in Severe Idiopathic Aplastic Anemia

Our previous study showed that a less toxic regimen comprising reduced cyclophosphamide (Cy), fludarabine and anti-thymocyte globulin (ATG) (Cy-Flu-ATG), was less toxic for allogeneic hematopoietic cell transplantation (alloHCT) compared with standard Cy-ATG in patients with adult severe aplastic anemia (AA). We postulated that replacing Cy with Flu (Flu-ATG) would be more beneficial. Therefore, we performed a randomized phase III study to compare the regimen-related toxicities (RRTs) of two different conditioning regimens: Cy-ATG vs. Flu-ATG. Pre-defined RRTs were defined as pulmonary complications, hepatic sinusoidal obstruction syndrome (SOS), hemorrhagic cystitis and death of any causes. We present the final analysis. Patients in the Cy-ATG arm received Cy at 200 mg/kg. Those in the Flu-ATG arm received fludarabine (Flu) at 180 mg/m2. Bone marrow (BM) as allowed when the donor was matched sibling donor and otherwise stem cell source was mobilized peripheral blood (PB). Regimen for graft-versus-host disease (GvHD) was cyclosporine and short-course methotrexate. A total of 63 patients (31 patients in Cy-ATG and 32 patients in Flu-ATG) were enrolled. The basic patients'characteristics were similar between both arms in terms of gender, age, prior immune suppression therapy history, stem cell source, stem cell dose, donor type and HLA-matching. There were 36 unrelated donors in each arm (p=1.000). All predefined RRTs were similar between Cy-ATG and Flu-ATG (33.3% vs. 21.9%; p=0.691). There was no difference between Cy-ATG and Flu-ATG in terms of pulmonary complications (12.9% vs. 3.1%; p=1.000), SOS (0% vs. 3.1%; p=1.000), hemorrhagic cystitis (6.5% vs. 3.1%; p=0.607) and death of any causes (23.3% vs. 15.6%; p=0.443). Primary engraftment failure was not found in Flu-ATG arm but 2 patients in Cy-ATG (p = 0.230), one of which died of treatment-related hepatic toxicity before engraftment. However, there was higher secondary engraftment failure inFlu-ATG arms compared with Cy-ATG (2nd GF; 21.9% vs. 6.9%; p=0.098). Therefore, any engraftment failure was not different between Cy-ATG vs. Flu-ATG (13.3% vs. 21.9%; p=0.379). The incidence of all grades acute GvHD was significantly higher in Cy-ATG arm (35.7% vs. 9.4%; p=0.013). The incidence of chronic GvHD was lower in Cy-ATG arm but was not statistically significant (11.5% vs. 23.1%; p=0.271). Any significant treatment-related toxicities including RRTs were similar between Cy-ATG and Flu-ATG arms (43.3% vs. 43.8%; p=0.974). The 3-year survival rate did not differ between Cy-ATG and Flu-ATG (72.9% vs. 79.3%; p=0.329). In conclusion, Flu-ATG can be comparable with Cy-ATG in terms of RRT and survival.

Single Center Experience with Hematopoietic Cell Transplantation in Young Children with Chronic Granulomatous Disease

Rationale Chronic granulomatous disease (CGD) is a primary immune deficiency due to defects in the phagocyte oxidative burst leading to life-threatening infections and inflammatory disorders. Due to high mortality and morbidity, hematopoietic cell transplantation (HCT) is now considered a potentially curative option. We evaluated outcomes of HCT at our institution over 13 years. Methods Retrospective chart review of CGD HCTs performed at John Hopkins All Children's Hospital between August 2005-October 2018. Results Eight patients (median age=2.2 years, range=1.1-4.3 years) with CGD underwent HCT: 6 patients had X-linked (CYBB, gp91phox), 2 patients had autosomal recessive (CYBA, p22phox). Pre-HCT infections were controlled including; pneumonia (n=3, 2 Aspergillus, 2 requiring lobectomy) and staphylococcal lymphadenitis/skin abscesses(n=3). Five of eight (62%) had inflammatory disease pre-HCT: lung granulomas (n=2), autoimmune hepatitis (n=3), and colitis (n=2). Myeloablative conditioning was used in 3 and reduced intensity/toxicity (RIC) in 5. Four received matched related donor and 4 received matched unrelated-donor HCTs. Median neutrophil engraftment was 18.5 days (range=10-21 days). Overall survival was 87.5%. One patient died (day +21) from disseminated Trichosporon. All patients achieved primary engraftment; 42% (3/7) maintained full donor chimerism (≥99%) with normalization of DHR, median follow-up 4.3 years (range=4-8.3 years); 42% (3/7) are mixed chimera (58-84% myeloid donor), median follow-up of 0.9 years (range=0.8-1.2 years). One patient who received RIC (Fludarabine/Melphalan/Campath) had secondary graft failure 1 year after HCT, has since developed inflammatory colitis, uveitis, and pneumonitis and is awaiting second HCT. There was no grade III-IV GVHD; 2 had acute grade I GVHD. Post-HCT complications included EBV viremia (without PTLD) in 1, pericarditis in 1, autoimmune cytopenias in 1 and hypothyroidism in 1. Conclusions Patients with CGD are at high risk of early mortality. HCT is a viable treatment option but has considerable risk, often deterring providers and patients from pursuing HCT early. Our institution's experience shows safety and efficacy with early HCT approach.

Rescue treatment with eltrombopag in refractory cytopenias after allogeneic stem cell transplantation.

Background:Patients with post-transplant cytopenias due to poor graft function or primary engraftment failure show poor prognosis with a high mortality rate mainly because of graft versus host disease (GVHD), infection and/or bleeding. Treatment options are scarce and a CD34+ stem cell boost or a second bone marrow transplantation may be required to restore adequate haematopoiesis.Methods:In the present study patients with primary engraftment failure (n = 1) and refractory poor graft function (n = 11) were treated with eltrombopag in a single centre. The reason for eltrombopag treatment was trilineage cytopenia in six patients, bilineage cytopenia in three patients and single lineage cytopenia in three patients. Eltrombopag was initiated at a median of 214 (range: 120–877) days after haematopoietic stem cell transplantation (HCST) and administered for a median time of 114 (range: 12 days to >490) days. In 8/12 patients eltrombopag was introduced at a dose of 75 mg/day and then increased to 150 mg/day after 1 week; 1 patient was given 50 mg eltrombopag per day, and 3 patients received 75 mg daily.Results:In 10/12 patients eltrombopag significantly enhanced blood count values and patients became transfusion independent. Once stable haematological response was obtained, treatment was tapered until final discontinuation in 9/10 responding patients. No grade 3 or 4 toxicities were observed. At time of last follow up, 3/12 patients were dead, 2 due to disease relapse, 1 due to GVHD and pneumonia. All patients except one maintained their complete response and remain transfusion independent at a median of 858 (range: 429–1119) days.Conclusion:These preliminary data confirm that eltrombopag is able to rescue multilineage haematopoiesis in patients with treatment-refractory cytopenias after allogeneic HSCT.

Haploidentical Stem Cell Transplantation with TCR Alpha/Beta and CD19 Depletion in Adult Patients with Hematological Malignancies

Introduction In most cases, haploidentical stem cell transplantation (haplo-HSCT) with negative depletion of α/β(+) T cells and CD19+ B lymphocytes from the graft is used to treat pediatric patients. The results are promising. However, the results of this method in adult patients is controversial. The accumulation of experience in haplo-HSCT with TCRαβ / CD19 + depletion in the group of adult patients is relevant. Aim Evaluation of the effectiveness and characterization of the most frequent complications in adult patients with hematological malignancies who underwent allo-HSCT from a haploidentical donor with depletion of TCRαβ/CD19 + cells. Patients and methods The analysis included 32 patients (14 males/18 females) with acute myeloid leukemia (AML, n=12), acute lymphoblastic leukemia (ALL, n=11), myelodysplastic syndrome (MDS, n = 6), chronic myeloid leukemia (CML, n = 1), primary myelofibrosis (PMF, n = 1), lymphoproliferative disease (LPD, n = 1). Median age was 28 years (range, 17-58). Disease status of acute leukemia at the beginning of pre-transplant conditioning was first complete remission (CR1) in 14 patients, CR2 in 7 and active disease in 2 patients. Pre-transplant conditioning regimen: RIC (Treosulfan 42 g/m2, Melphalan 140 mg/m2, Fludarabine 150mg/m2), MAC (Treosulfan 42 g / m2, Thiophosphamide 10 mg / kg, Fludarabine 150 mg / m2). Immunosuppressive therapy: Rituximab, Bortezomib, Tocilizumab, Abatacept. Immunomagnetic separation was performed using a CliniMACS Plus device. Descriptive statistics methods were used for analysis. The probabilities of survival and graft versus host disease (GVHD) rate were estimated using the Kaplan-Meier method. Results Log of TCRαβ + depletion was 1.61-5.33 (Me = 3.66). The median dose of CD34+ cells in transplant was 6.8 * 106/kg (range, 2.0-10.8). The median time to white blood cells recovery was +13 days after haplo-HSCT (range, 9-26). Median follow-up was 6.4 months. Transplant related mortality was 3.1%. Primary engraftment - 96.8%. Graft hypofunction - 16.2%. The probabilities of overall and disease-free survival for 12 months were 94.1% and 70,5%, respectively. The probability of relapse was 24.4% (Fig. 1). The probability of developing acute GVHD was 25%, GVHD rate was 18,75% including grade I (n=1), grade II (n=2), grade III (n=3) (data not shown). In 4 cases complete response was achieved with administration of first line immunosuppression therapy. 1 case (grade III GVHD) required administration of second line immunosuppression therapy - methylprednisolone, and the response was complete. 1 patient developed chronic GVHD. Nonclassical infectious complications prevail: viral infections (CMV, HHV6 and EBV) was 58.8%, fever with an unverified infectious agent was 15.6%, and tuberculosis in two cases (6.2%). Immunological events not associated with GVHD - 21.8% (TMA, TTP, myasthenia gravis, AIHA, PRCA). Conclusion In some cases, haplo-HSCT is the only HSCT option for an adult patient. The frequency of viral infectious complications and relapses in adult patients after haplo-HSCT TCRαβ / CD19 + depletion is comparable to the results in the pediatric population. Haplo-HSCT with TCRαβ / CD19 + depletion is characterized by minimal toxicity and a short period of myelotoxic agranulocytosis. Among the undesirable phenomena in the first place are infectious complications and frequent immunological events that do not fit into the criteria for GVHD, but affect the patient's quality of life and length of hospital stay. Figure 1 Disclosures Maschan: Miltenyi Biotec: Other: lecture fee.

Targeting Bcl-2 and CD38 As Part of Personalized HSCT Conditioning Regimen in Chemorefractory Acute Leukemia in Children

Introduction The outcome HSCT in a cohort of children with chemorefractory acute leukemia (AL) is poor. The incidence of relapse exceeds 50% and survival varies from 10 to 40%. Additional attempts at remission induction with various combinations of chemotherapy are unlikely to improve the outcome and may contribute to toxicity. We hypothesized that personalized targeted therapy combined with high-dose preparative regimen may improve the outcome of alloHSCT in a cohort of pediatric patients with refractory AL. Bcl-2 and CD38 were chosen as potential targets due to frequent expression in pediatric acute leukemia, availability of marketed targeted therapies, venetoclax and daratumumab, and expected non-overlapping toxicity profile of these agents and the conditioning regimen. Materials and methods A total of 26 pts with chemorefractory acute leukemia (AML-18, T-ALL-6, ABL-2, primary refractory - 9, refractory relapse - 17, 18 male, 8 female, median age 11.3 years), underwent HSCT between November 2017 and May 2019. All patients were transplanted from haploidentical donors, all patients had active disease (AD) at the moment of SCT. For 19 (73%) pts it was the first alloHSCT, for 7 (27%) pts it was the second HSCT. Median bone marrow leukemia burden before cytoreduction was 11% (3-90). Bcl-2 expression on the tumor cells was detected in 23 pts with the median expression of 58% (1.5-99), CD38 expression was detected in 24 pts with the median expression of 88% (11-100). Thirteen pts received treosulfan-based conditioning and 13 - TBI-based (12 Gy). TBI was used among patients with second HSCT (n=7), patients with T-ALL (n=4) and patients with massive extramedullary disease (n=2). GvHD prophylaxis included tocilizumab at 8 mg/kg on day -1 and abatacept at 10 mg/kg on day -1, +7, +14, +28. According to the expression of Bcl-2 and CD38 on tumor cells, 24pts (92%) received daratumumab (anti-CD38 monoclonal antibody) on day -7 at 10-16 mg/kg, 21 pts (81%) received venetoclax at 300 mg/m2/day on days -7 to -2 and 12 pts additionally received plerixafor at 240 mcg/kg x 3 on days -7 to -5. TCRαβ+/CD19+ depletion of PBSC with CliniMACS technology was implemented in all cases. The median dose of CD34+ cells in the graft was 9.5 x106/kg (range 4.9-13.3), αβ T cells - 26.5x103/kg (range 5.6- 84). Modified (CD45RA-depleted) donor lymphocyte infusions (DLI) were administered prophylactically in all pts. Results Two patients died before engraftment due to septic event. Primary engraftment was achieved in 24 of 24 evaluable pts (100%), the median time to neutrophil and platelet recovery was 12 and 13 days. All pts achieved complete remission on day +30. There were no significant toxic effects after targeted therapy, 4 pts (21%) had daratumumab-related infusion reactions, one patient with T-ALL died after engraftment due to septic event. aGVHD grade I-II developed in 5 pts (20%), two of them required systemic immunosuppressive therapy. There were no cases of aGVHD &amp;gt; grade II, neither cases of cGVHD. The median NK- cells count by the day +30 was 0.07 x 106/ml (range 0.01- 0.4), the median levels of αβ T cells and gd T cells were 0.018 x 106 /ml (range 0 - 1.1) and 0.015 x 106 /ml (range 0,01 - 1.3), respectively. Nine (37.5%) pts (5 with T-ALL, 1 with ABL, 3 with AML) relapsed, median interval to relapse was 103 days (55-345). At the moment of reporting 14 (53%) patients are alive in complete remission with a median follow up of 12.7 months (1.9-23m). Event-free and overall survival at 1 year for AML are 76% (SE13) and 76% (SE14), all patients with T-ALL and one with ABL died of disease progression. Conclusion We suggest that addition of venetoclax and daratumomab to the backbone of myeloablative haploidentical HSCT with αβ T cell depletion is not associated with increased toxicity and may lead to improved outcome in a cohort of pediatric patients with chemorefractory AML. In a subgroup of patients with T-ALL this approach does not seem to produce visible benefit. This approach can be further tested in a prospective trial with the goal to increase the anti-leukemic efficacy of HSCT. Figure Disclosures Maschan: Miltenyi Biotec: Other: lecture fee. Off Label Disclosure: venetoclax daratumomab plerixafor

TCR α+ β+ /CD19+ cell-depleted hematopoietic stem cell transplantation for pediatric patients.

TCR α+ β+ /CD19+ cell depletion is an emerging technique for ex vivo graft manipulation in HSCT. We report 20 pediatric patients who underwent TCR α+ β+ /CD19+ cell-depleted HSCT in four Australian centers. Conditioning regimen was dependent on HSCT indication, which included immunodeficiency (n=14), Fanconi anemia (n=3), and acute leukemia (n=3). Donor sources were haploidentical parent (n=17), haploidentical sibling (n=2), or matched unrelated donor (n=1). Mean cell dose was 8.2×108 /kg TNC, 12.1×106 /kg CD34+ cells, and 0.4×105 /kg TCR α+ β+ cells. All patients achieved primary neutrophil and platelet engraftment, with average time to neutrophil engraftment 11days (range 8-22) and platelet engraftment 24days (range 12-69). TRM at 1year was 15%. Rate of grade II-IV aGVHD at 1year was 20% with no grade III-IV aGVHD seen. CMV reactivation occurred in 81% of CMV-positive recipients, with one patient developing CMV disease. Average time to CD4 recovery (>400×106 /L) was 258days. Overall survival for the cohort at 5years was 80%. This report highlights the initial experience of TCR α+ β+ /CD19+ cell-depleted HSCT in Australian centers, with high rates of engraftment, low rates of aGVHD, and acceptable TRM.