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There is no consensus on the best donor for children with nonmalignant disorders and immune deficiencies in the absence of a matched related donor (MRD). We evaluated the 2-year overall survival (OS) after umbilical cord blood transplantation (UCBT) in patients with nonmalignant disorders from 2009 to 2020 enrolled in a prospective clinical trial using either 5/6 or 6/6 UCB as the cell source. Patients receive a fully ablative busulfan, cyclophosphamide, and fludarabine without serotherapy. Fifty-five children were enrolled, median age 5 months (range, 1-111 months); primary immune deficiency (45), metabolic (5), hemophagocytic lymphohistiocytosis (1), and hematologic disorders (4). Twenty-six patients had persistent infections before transplant. Nineteen of them (34%) were 6/6 matched, and 36 (66%) were 5/6 human leukocyte antigen–matched. The OS at 2 years was 91% (95% cumulative incidence, 79-96), with a median follow-up of 4.3 years. The median time to neutrophil and platelet recovery were 17 days (range, 5-39 days) and 37 days (range, 20-92 days), respectively. All but one evaluable patient achieved full donor chimerism. The cumulative incidence of acute GVHD grades 2-4 on day 100 was 16% (n = 9). All patients with viral infections at the time of transplant cleared the infection at a median time of 54 days (range, 44-91 days). All evaluable patients underwent correction of their immune or metabolic defects. We conclude that in the absence of MRD, UCBT following myeloablative conditioning without serotherapy is an excellent curative option in young children with nonmalignant disorders. This trial has been registered at www.clinicaltrials.gov as NCT00950846.

Purpose: Viral infections are a major cause of morbidity and mortality following allogeneic hematopoietic cell transplantation (allo-HCT). In the absence of safe and effective antiviral treatments, virus-specific T cells have emerged as a promising therapeutic option. Posoleucel is a multivirus-specific T-cell therapy for off-the-shelf use against six viral infections that commonly occur in allo-HCT recipients: adenovirus, BK virus (BKV), cytomegalovirus, Epstein–Barr virus, human herpes virus-6, and JC virus. Patients and Methods: We conducted an open-label, phase II trial to determine the feasibility and safety of posoleucel in allo-HCT recipients infected with one or more of these viruses. Infections were either unresponsive to or patients were unable to tolerate standard antiviral therapies. Fifty-eight adult and pediatric patients were enrolled and treated. Results: Posoleucel was well tolerated, with no cytokine release syndrome or other infusion-related toxicities; two patients (3.4%) developed Grade 2 and one patient (1.7%) Grade 3 GvHD during the trial. The overall response rate 6 weeks after the first posoleucel infusion was 95%, with a median plasma viral load reduction of 97%. Of the 12 patients who had two or more target viral infections identified at study entry, 10 (83%) had a clinical response for all evaluable viruses. Of the 23 patients treated for refractory BKV-associated hemorrhagic cystitis, 74% had resolution of symptoms and macroscopic hematuria by 6 weeks post-infusion. Conclusions: In this open-label trial, treatment of refractory viral infections/disease in allo-HCT recipients with posoleucel was feasible, safe, and effective.

Cord blood (CB) is the stem cell source of choice for approximately 30% of pediatric patients undergoing hematopoietic cell transplantation. Cord blood is readily available and is a particularly appealing stem cell source for patients who lack appropriate HLA-matched related or unrelated donors. Pediatric cord blood transplant (CBT) recipients have low rates of disease relapse in the malignant setting and very low rates of chronic graft-versus-host disease (GVHD). In addition, CB has unique properties that make it the stem cell source of choice for some nonmalignant conditions such as metabolic disorders. This review provides evidence-based and experience-based pediatric-specific guidelines for CBT including considerations for infectious disease management, CB unit selection and infusion, conditioning regimen selection, and GVHD management. In addition, it covers unique bedside considerations for pediatric patients and CB banking. In concert with the other topic specific CB guidelines previously published in this series, it provides a comprehensive overview of the clinical management of pediatric CBT.

Background Serious viral infections are a leading cause of morbidity and mortality in pediatric recipients of allogeneic hematopoietic cell transplant (allo-HCT). Most available antivirals have significant toxicities and suboptimal efficacy. Posoleucel (PSL) is an allogeneic, off-the-shelf multi-virus specific T cell investigational product to prevent or treat 6 viral infections (AdV, BKV, CMV, EBV, HHV-6, and JCV). In the phase 2 CHARMS trial of PSL in allo-HCT recipients with intractable viral infections, 95% of patients had a clinical response. Here we present the efficacy and safety data in pediatric patients (< 18 years) enrolled in CHARMS. Methods Allo-HCT patients who had failed antiviral therapy or were unable to tolerate antivirals to control BKV, CMV, AdV, EBV, HHV-6, and/or JCV infection received a single PSL infusion of 2×107 cells/m2. Patients with a response could receive up to 4 more doses after 4 weeks, at 2-week intervals. The primary endpoint of the study was safety and feasibility. Other endpoints included complete and partial clinical response, with complete response (CR) as return to normal range and resolution of signs/symptoms and partial response (PR) defined as ≥50% decrease in viral load and/or ≥50% improvement of clinical signs/symptoms assessed by 6 weeks post infusion. Results 18 pediatric patients received PSL (1 was treated for 2 infections separately). Of the 13 with 1 viral infection, 6 (46%) had BKV, 3 (23%) CMV, 2 (15%) AdV, 2 (15%) HHV-6, and none EBV or JCV. Five (38%) had >1 infection: 3 had 2 infections, 1 had 3 infections, and 1 had 1 viral infection at each of 2 enrollments. 56% of patients received one infusion. PSL was generally well tolerated. Besides fever in 7 patients, we observed no toxicities or symptoms of CRS. Five cases of acute graft-versus-host disease (aGVHD) were observed; 3 in patients with history of aGVHD (2 had aGVHD at baseline). Both de novo cases of GVHD were Grade 1. 100% of patients achieved a clinical response (CR or PR) by 6 weeks including all 5 patients infected with multiple target viruses. Four of 6 patients with AdV infection had CR. Conclusion PSL treatment was well tolerated. All pediatric patients receiving PSL had a clinical response. Phase 3 studies including pediatric patients are in progress. Disclosures Ifigeneia Tzannou, MD, AlloVir: Advisor/Consultant Carlos Ramos, MD, Novartis: Advisor/Consultant Swati Naik, MD, Bellicum: Travel, Accomodation, Expenses Iain Fraser, MD, DPhil, AlloVir: Employee|AlloVir: Stocks/Bonds Marshelle Warren, MD, AlloVir: Advisor/Consultant Badrish Patel, MD, AlloVir: Employee|AlloVir: Stocks/Bonds Dany Ward, RN, AlloVir: Employee|AlloVir: Stocks/Bonds Ann Leen, PhD, AlloVir: Advisor/Consultant|AlloVir: Stocks/Bonds Bilal Omer, MD, AlloVir: Grant/Research Support.

Inborn errors of immunity that present with concomitant immunodeficiency and auto-inflammation are therapeutically challenging; furthermore, complexity is added when they are caused by mutations in genes that encode for proteins expressed beyond immune cells. The ubiquitin-proteasome system is the main intracellular proteolytic machinery and participates in most cellular processes by degrading ubiquitinated proteins. Mutations in proteasome subunits resulting in proteasome deficiency cause a severe auto-inflammatory disease characterized by chronic auto-inflammation neutrophilic dermatosis and fever, collectively referred to as Proteasome Associated Auto-inflammatory Syndromes (PRAAS). POMP is a chaperone for proteasome assembly and AD mutations in POMP cause a form of PRAAS with prominent immunodeficiency referred to as POMP-related auto-inflammation and immune dysregulation (PRAID) manifesting with recurrent, severe and opportunistic infections in addition to inflammatory features that are characteristic for all PRAAS disorders, most importantly early-onset neutrophilic dermatosis. JAK inhibitors partially control the disease in individuals with PRAAS, however life-threatening, recurrent and opportunistic infections in patients with POMP mutations limit immunosuppressive therapies and prompted consideration of hematopoietic stem cell transplant (HSCT). We describe successful HSCT in two patients with POMP deficiency. Despite POMP being ubiquitously expressed, the immunologic and auto-inflammatory phenotype were both ameliorated through HSCT which suggests that the clinical and immunological features of PRAID are predominantly derived from a proteasome defect in hematopoietic cells. To our knowledge, these are the first patients with a form of PRAAS cured by HSCT, opening new therapeutic possibilities for these diseases.

Adenosine deaminase (ADA) deficiency causes ∼13% of cases of severe combined immune deficiency (SCID). Treatments include enzyme replacement therapy (ERT), hematopoietic cell transplant (HCT), and gene therapy (GT). We evaluated 131 patients with ADA-SCID diagnosed between 1982 and 2017 who were enrolled in the Primary Immune Deficiency Treatment Consortium SCID studies. Baseline clinical, immunologic, genetic characteristics, and treatment outcomes were analyzed. First definitive cellular therapy (FDCT) included 56 receiving HCT without preceding ERT (HCT); 31 HCT preceded by ERT (ERT-HCT); and 33 GT preceded by ERT (ERT-GT). Five-year event-free survival (EFS, alive, no need for further ERT or cellular therapy) was 49.5% (HCT), 73% (ERT-HCT), and 75.3% (ERT-GT; P < .01). Overall survival (OS) at 5 years after FDCT was 72.5% (HCT), 79.6% (ERT-HCT), and 100% (ERT-GT; P = .01). Five-year OS was superior for patients undergoing HCT at

Infants with inborn errors of immunity (IEI), born in countries where Bacillus-Calmette-Guerin (BCG) vaccination is recommended at birth, are at risk of developing infectious complications following vaccination. A prompt diagnosis of disseminated BCG infection in these infants is essential, as many will require stem cell transplantation (SCT) for the immunologic cure. In patients with IEI, the mortality risk from disseminated mycobacterial infection is high, both before and following SCT.A 7-month-old Qatari infant with an IEI, homozygous IKBKB gene mutation, was evaluated at our institution for SCT. He had a history of recurrent pneumonias, but pretransplant evaluation revealed negative cultures from bronchoalveolar fluid, blood and urine. At 8 months of age, the infant developed skin nodules of unclear etiology, prompting additional evaluation.Given his profound immunosuppression and receipt of broad-spectrum antimicrobials, plasma metagenomic next-generation sequencing (mNGS) was obtained and identified Mycobacterium tuberculosis complex within 72 hours. A skin biopsy was performed, and antimycobacterial therapy was initiated. Mycobacterium bovis-BCG was confirmed from cultures 3 weeks later. Treatment was complicated by elevated serum liver transaminases and aminoglycoside-associated high-frequency hearing loss. The infant completed 14 months of treatment from engraftment. Evaluation for active BCG infection after SCT was negative.In an infant with a unique IEI, plasma mNGS provided the first diagnosis of disseminated BCG infection. We believe that early initiation of antimycobacterial treatment improved the infant's clinical outcome. Plasma mNGS testing should be considered as a noninvasive screen for infectious pathogens in children with IEIs before SCT.

Hematopoietic stem cell transplant (HSCT) is a curative option for patients with high-risk acute lymphoblastic leukemia (ALL), but relapse remains a major cause of treatment failure. To prevent disease relapse, we prepared and infused donor-derived multiple leukemia antigen–specific T cells (mLSTs) targeting PRAME, WT1, and survivin, which are leukemia-associated antigens frequently expressed in B- and T-ALL. Our goal was to maximize the graft-versus-leukemia effect while minimizing the risk of graft-versus-host disease (GVHD). We administered mLSTs (dose range, 0.5 × 107 to 2 × 107 cells per square meter) to 11 patients with ALL (8 pediatric, 3 adult), and observed no dose-limiting toxicity, acute GVHD or cytokine release syndrome. Six of 8 evaluable patients remained in long-term complete remission (median: 46.5 months; range, 9-51). In these individuals we detected an increased frequency of tumor-reactive T cells shortly after infusion, with activity against both targeted and nontargeted, known tumor-associated antigens, indicative of in vivo antigen spreading. By contrast, this in vivo amplification was absent in the 2 patients who experienced relapse. In summary, infusion of donor-derived mLSTs after allogeneic HSCT is feasible and safe and may contribute to disease control, as evidenced by in vivo tumor-directed T-cell expansion. Thus, this approach represents a promising strategy for preventing relapse in patients with ALL.

Despite improvements, mortality after allogeneic hematopoietic cell transplantation (HCT) for nonmalignant diseases remains a significant problem. We evaluated whether pre-HCT conditions defined by the HCT Comorbidity Index (HCT-CI) predict probability of posttransplant survival. Using the Center for International Blood and Marrow Transplant Research database, we identified 4083 patients with nonmalignant diseases transplanted between 2007 and 2014. Primary outcome was overall survival (OS) using the Kaplan-Meier method. Hazard ratios (HRs) were estimated by multivariable Cox regression models. Increasing HCT-CI scores translated to decreased 2-year OS of 82.7%, 80.3%, 74%, and 55.8% for patients with HCT-CI scores of 0, 1 to 2, 3 to 4, and ≥5, respectively, regardless of conditioning intensity. HCT-CI scores of 1 to 2 did not differ relative to scores of 0 (HR, 1.12 [95% CI, 0.93-1.34]), but HCT-CI of 3 to 4 and ≥5 posed significantly greater risks of mortality (HR, 1.33 [95% CI, 1.09-1.63]; and HR, 2.31 [95% CI, 1.79-2.96], respectively). The effect of HCT-CI differed by disease indication. Patients with acquired aplastic anemia, primary immune deficiencies, and congenital bone marrow failure syndromes with scores ≥3 had increased risk of death after HCT. However, higher HCT-CI scores among hemoglobinopathy patients did not increase mortality risk. In conclusion, this is the largest study to date reporting on patients with nonmalignant diseases demonstrating HCT-CI scores ≥3 that had inferior survival after HCT, except for patients with hemoglobinopathies. Our findings suggest that using the HCT-CI score, in addition to disease-specific factors, could be useful when developing treatment plans for nonmalignant diseases.

Transplantation-associated thrombotic microangiopathy (TA-TMA) is a complication of hematopoietic stem cell transplant (HSCT) that causes severe multiorgan injury. The kidneys are almost universally affected. There is no proven therapy, but therapeutic plasma exchange (TPE) is commonly used to treat TA-TMA at Texas Children's Hospital (TCH). To date, there have been no studies assessing the long-term efficacy of TPE in preventing the development of chronic kidney disease (CKD) in TA-TMA patients. In this study we retrospectively analyzed the incidence of CKD in TA-TMA pediatric patients treated with TPE to determine if this treatment modality improves renal morbidity. We reviewed records between January 2007 and June 2017 of pediatric HSCT patients diagnosed with TA-TMA, identified through an internal database maintained at TCH. To be included patients must have completed a course of TPE per the "TPE in TA-TMA" institutional protocol at TCH. CKD was defined as kidney damage for at least 3 months and stratified into stages 1 through 5 according to estimated glomerular filtration rate. Stages 4 and 5 were considered "severe CKD." In the 10-year timeframe 15 patients with TA-TMA completed a course of TPE per our institutional protocol and were subsequently followed for a median of 963 days. Fourteen patients developed CKD, and 5 of these 14 patients developed severe CKD. The cumulative incidence of severe CKD development was 33% (95% confidence interval. 11% to 57%). 6 patients required dialysis, and 2 patients received a renal transplant. 5 patients received eculizumab in addition to TPE. In our patients a TPE course of at least 7 weeks (and up to 25 weeks) was not effective in the prevention of CKD. Our data indicate a need for alternative therapeutic measures to prevent the development of CKD in TA-TMA patients.

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare X-linked disorder caused by a loss of function mutation in the FOXP3 gene. It manifests early in infancy with clinical symptoms including autoimmune enteropathy, type 1 diabetes mellitus, and eczema. While aberrant FOXP3 expression has been associated with several types of cancer, little is known regarding the risk of cancer in patients with IPEX harboring the characteristic FOXP3 mutation. Here, we present a unique case of a primary signet ring gastric adenocarcinoma in a pediatric patient with IPEX syndrome.

Chronic granulomatous disease (CGD) is a primary immune deficiency due to defects in phagocyte respiratory burst leading to severe and life-threatening infections. Patients with CGD also suffer from disorders of inflammation and immune dysregulation including colitis and granulomatous lung disease, among others. Additionally, patients with CGD may be at increased risk of systemic inflammatory disorders such as hemophagocytic lymphohistiocytosis (HLH). The presentation of HLH often overlaps with symptoms of systemic inflammatory response syndrome (SIRS) or sepsis and therefore can be difficult to identify, especially in patients with a primary immune deficiency in which incidence of infection is increased. Thorough evaluation and empiric treatment for bacterial and fungal infections is necessary as HLH in CGD is almost always secondary to infection. Simultaneous treatment of infection with anti-microbials and inflammation with immunosuppression may be needed to blunt the hyperinflammatory response in secondary HLH. Herein, we present a series of X-linked CGD patients who developed HLH secondary to or with concurrent disseminated CGD-related infection. In two patients, CGD was a known diagnosis prior to development of HLH and in the other two CGD was diagnosed as part of the evaluation for HLH. Concurrent infection and HLH were fatal in three; one case was successfully treated, ultimately receiving hematopoietic stem cell transplantation. The current literature on presentation, diagnosis, and treatment of HLH in CGD is reviewed.

The Primary Immune Deficiency Treatment Consortium (PIDTC) performed a retrospective analysis of 662 patients with severe combined immunodeficiency (SCID) who received a hematopoietic cell transplantation (HCT) as first-line treatment between 1982 and 2012 in 33 North American institutions. Overall survival was higher after HCT from matched-sibling donors (MSDs). Among recipients of non-MSD HCT, multivariate analysis showed that the SCID genotype strongly influenced survival and immune reconstitution. Overall survival was similar for patients with RAG, IL2RG, or JAK3 defects and was significantly better compared with patients with ADA or DCLRE1C mutations. Patients with RAG or DCLRE1C mutations had poorer immune reconstitution than other genotypes. Although survival did not correlate with the type of conditioning regimen, recipients of reduced-intensity or myeloablative conditioning had a lower incidence of treatment failure and better T- and B-cell reconstitution, but a higher risk for graft-versus-host disease, compared with those receiving no conditioning or immunosuppression only. Infection-free status and younger age at HCT were associated with improved survival. Typical SCID, leaky SCID, and Omenn syndrome had similar outcomes. Landmark analysis identified CD4(+) and CD4(+)CD45RA(+) cell counts at 6 and 12 months post-HCT as biomarkers predictive of overall survival and long-term T-cell reconstitution. Our data emphasize the need for patient-tailored treatment strategies depending upon the underlying SCID genotype. The prognostic significance of CD4(+) cell counts as early as 6 months after HCT emphasizes the importance of close follow-up of immune reconstitution to identify patients who may need additional intervention to prevent poor long-term outcome.

There is a lack of consensus regarding the role and method of hematopoietic stem cell transplantation (HSCT) on patients with chronic granulomatous disease (CGD). Long-term follow-up after HSCT in these patient population is essential to know its potential complications and decide who will benefit the most from HSCT. We report the outcome of HSCT and long-term follow-up in 24 patients with CGD, transplanted in our center from either related (n = 6) or unrelated (n = 18) donors, over a 12-year period (2003 to 2015), using high-dose alemtuzumab in the preparative regimen. We evaluated the incidence and timing of adverse events and potential risk factors. We described in detailed the novel finding of increased autoimmunity after HSCT in patients with CGD. At a median follow-up of 1460 days, 22 patients were full donor chimeras, and 2 patients had stable mixed chimerism. All assessable patients showed normalization of their neutrophil oxidative burst test. None of the patients developed grades II to IV acute graft-versus-host disease, and no patient had chronic graft-versus-host disease. Twelve of 24 patients developed 17 autoimmune diseases (ADs). Severe ADs (cytopenia and neuropathy) occurred exclusively in the unrelated donor setting and mainly in the first year after HSCT, whereas thyroid AD occurred in the related donor setting as well and more than 3 years after HSCT. Two patients died due to infectious complications after developing autoimmune cytopenias. One additional patient suffered severe brain injury. The remaining 21 patients have long-term Lansky scores ≥ 80. The outcome of HSCT from unrelated donors is comparable with related donors but might carry an increased risk of developing severe AD. A lower dose of alemtuzumab may reduce this risk and should be tested in further studies.

Hematopoietic stem cell transplantation (HSCT) is the only curative option for a subset of patients with high-risk or relapsed acute lymphoblastic leukemia (ALL). Given evolving practices, it is important to continually evaluate outcomes for pediatric ALL following HSCT. Outcomes after HSCT are influenced by the type of donor used as this determines the degree and method of T cell depletion used and, consequently, specific transplant-related morbidities. We retrospectively analyzed HSCT data from our center for transplants performed between January 2008 and May 2016, comparing outcomes among different donor types. One hundred and twenty-four pediatric patients underwent HSCT from a matched sibling donor (MSD; n = 48), an unrelated matched donor (UMD; n = 56), or a haploidentical donor (n = 20). We observed a similar 3-year event-free survival (EFS) for MSD recipients (of .64) and for UMD recipients (.62), but a significantly lower EFS for recipients of haploidentical transplants (.35; P = .01). Relapse was the main cause of HSCT failure and was significantly higher in the haploidentical donor group (.47 versus .19 for MSD and .24 for UMD; P = .02). Treatment-related mortality was evenly distributed among the donor groups (.17, .16, and .15 for the MSD, UMD, and haploidentical groups, respectively). Rates of infection-related mortality were lower than previously reported. Relapse is the main obstacle for successful HSCT in the contemporary era, and this effect is most evident in recipients of haploidentical donor grafts. Newer methods to improve graft-versus-leukemia effect are being evaluated and will need to be incorporated into the management of high-risk patients.

Wiskott-Aldrich syndrome (WAS) is a rare X-linked disorder characterized by a triad of immunodeficiency, eczema, and thrombocytopenia. Currently, hematopoietic stem cell transplantation (HSCT) is the most reliable curative treatment with excellent results for patients with HLA-matched family or unrelated donors. However, even after fully myeloablative preparative regimens, mixed donor chimerism is a potential concern. We performed a retrospective chart review of 12 children who underwent allogeneic HSCT for WAS to report our experience. The median age at transplant was 10.5 months (range, 3 to 39). The median nucleated cell dose from the marrow was 4.55 × 109/kg (range, .3 to 7.9). The median times to neutrophil and platelet engraftment were 19 days (range, 13 to 27) and 18.5 days (range, 12 to 31), respectively. The rate of overall survival was 92% with median follow-up of 67 months (range, 3 to 146). Two patients developed grade IV acute graft-versus-host disease, and 1 died on day +99. Five of 12 patient's (42%) had mixed donor chimerism (range, 12% to 85%) at day +180. None of the pretransplant patient parameters was predictive of mixed chimerism. Nonetheless, of these 5 patients, 2 had normalization of the platelet count despite the mixed chimerism, 2 had full donor chimerism after receiving a second transplant with the same donor, and 1 remains transfusion dependent awaiting a second transplant. Hence, even with a significant rate of mixed chimerism, HSCT provides substantial benefit to WAS patients, with excellent overall survival.

Introduction: Transplant-associated thrombotic microangiopathy (TA-TMA) is an increasingly recognized hematologic complication after allogeneic hematopoietic cell transplantation (HCT). While few studies have reported germline association with rare variants in complement genes using targeted next generation sequencing (NGS) method, they were limited by small sample size (≤40 TMA cases) and lack of analysis of non-complement genes (PMIDs 26603840, 32131130). In the present study, we employed whole exome sequencing (WES) to assess rare variant contribution to the development of TMA in a hypothesis-driven pathway-specific approach. Methods: In the current case-control genetic association study conducted at Fred Hutchinson Cancer Research Center, we selected 100 patients with a diagnosis of TMA and pre-transplant DNA samples (case definition described previously in PMID 30940363, 33836868). We then performed incidence density sampling to randomly select 100 non-TMA controls after allogeneic HCT matching by age, sex, race, and year of HCT. WES (germline variant detection 40x) was conducted using Illumina NovaSeq. Sequence reads were mapped to hg38 reference genome followed by deduplication and base quality score recalibration. Joint-genotyping was performed to call single nucleotide polymorphism (SNPs) and insertion/deletion (indels) using the GATK v3.3 and Atlas2. Variants were filtered during quality control (QC) and variant quality score recalibration (VQSR) and annotated using ANNOVAR and Ensembl VEP. To optimize signal detection by reducing neutral background variation, we defined qualifying variants as those meeting all 3 criteria: 1) novel or rare variants with a minor allele frequency (MAF) We then focused on the exome profiles of 5 a priori selected genetic pathways: complement regulation (17 genes), VWF and coagulation (7 genes), VWF clearance (10 genes), ADAMTS13 mimics or interacting proteins (10 genes), and angiopoietin family and endothelial activation (7 genes). Pathway-based and gene-based collapsing association tests were performed using the Optimized Sequence Kernel Association (SKAT-O) test as an optimal test combining burden test and SKAT. Results: After joint variant calling, 91 TMA cases and 93 non-TMA controls passed all QC filters (Table 1). Among 1,485 variants detected in the 5 pathways after QC, 60 variants (73 total mutations) were considered as qualifying variants with MAF Conclusion: Contrary to the initial hypothesis, we did not observe pathogenic germline rare variants in the complement regulation pathway in patients with TA-TMA. Instead, we found a significant association in the VWF clearance pathway, particularly that of the LRP1 gene. In recent years, researchers have shown that VWF can bind to and activate complement proteins. Impaired VWF clearance could lead to the higher predisposition for complement activation observed in patients with TA-TMA. Future functional studies are needed to determine the impact of VWF clearance on the pathogenesis of the disease. Figure 1 Figure 1. Disclosures Sartain: Alexon Pharamaceuticals: Membership on an entity's Board of Directors or advisory committees. Lee: Incyte: Research Funding; Janssen: Other; Takeda: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Research Funding; Kadmon: Research Funding; National Marrow Donor Program: Membership on an entity's Board of Directors or advisory committees; Syndax: Research Funding; AstraZeneca: Research Funding; Amgen: Research Funding.

Background: Hematopoietic stem cell transplant (HSCT) is a curative option for patients with high-risk Acute Lymphoblastic Leukemia (HR-ALL), but relapse remains a major cause of treatment failure. Strategies to enhance the graft-versus-leukemia (GVL) effect have been employed to prevent relapse, including modulating immune suppression post-HSCT to hasten immune reconstitution or with the use of donor lymphocyte infusions (DLIs). However, DLIs carry a significant risk of graft-versus-host disease (GVHD) due to the concurrent transfer of alloreactive T cells. To enhance the GVL effect while minimizing GVHD, we developed a protocol for the generation of ex vivo expanded, donor-derived T-cell lines targeting PRAME, WT1 and Survivin - tumor associated antigens that are frequently expressed in both B- and T-cell ALL. These multi-antigen-targeted T cells (multiTAAs) were adoptively transferred to pediatric and adult patients with HR-ALL who had undergone an allogeneic HSCT. Methods: Donor-derived multiTAA-specific T cells were generated by co-culturing PBMCs with autologous DCs loaded with pepmixes (15 mer peptides overlapping by 11 amino acids) spanning all 3 target antigens in the presence of a Th1-polarizing/pro-proliferative cytokine cocktail. Following 2-4 rounds of stimulation these multiTAA-specific T cells were infused to patients with ALL who had undergone an HSCT but remained at a high risk for disease relapse. Results: We have generated 15 clinical grade multiTAA-specific T cell lines comprising CD3+ T cells (mean 95.1±1.9%) with a mixture of CD4+ (mean 22.8±6.3%) and CD8+ (mean 52.5±5.3%) cells, which expressed central [CD45RO+/CD62L+: 13.5±2.8%] and effector memory markers [CD45RO+/CD62L-: 56.4±3.8%]. The expanded lines recognized the targeted antigens PRAME (range 0-370 SFC/2x10 5), WT1 (0-363 SFC/2x10 5), and Survivin (0-65 SFC/2x10 5) in an IFNg ELIspot. None of the lines reacted against non-malignant patient-derived cells (3.7±0.8% specific lysis; E: T 20:1) - a study release criterion indicating lack of alloreactivity. We have infused 11 HR-ALL patients (8 pediatric and 3 adult) with donor-derived multiTAA-specific T cells to prevent disease relapse (Table 1). Patients were administered with up to 4 infusions of cells at 3 escalating dose levels, ranging from 0.5 - 2x10 7 cells/m 2. Infusions were well tolerated with no dose-limiting toxicity, GVHD, cytokine release syndrome or other adverse events. Three patients were not evaluable per study criteria as they received >0.5mg/kg of steroids (2 patients received stress doses for septic shock and 1 for elevated liver enzymes presumed to be GVHD that was later ruled out) within 4 weeks of infusion and were replaced. Six of the 8 remaining patients infused remain in CR on long-term follow up at a median of 46.5 months post-infusion (range 9-51 months). In patients who remained in long term CR we detected an expansion of tumor-reactive T cells in their peripheral blood post-infusion against both targeted (WT1, Survivin, PRAME) and non-targeted antigens (SSX2, MAGE-A4, -A1, -A2B, -C1, MART1, AFP and NYESO1) reflecting epitope and antigen spreading, which correlated temporally (within 4 weeks) with multiTAA infusions. By contrast in the two patients who relapsed we saw no evidence of in vivo T cell amplification within the first 4 weeks after infusion. Conclusion: The preparation and infusion of donor-derived multiTAA-specific T cells to patients with B- and T-ALL post allogeneic HSCT is feasible, safe and as evidenced by in vivo tumor-directed T cell expansion and antigen spreading in patients, may contribute to disease control. This strategy may present a promising addition to current immunotherapeutic approaches for prophylaxis for leukemic relapse in HSCT recipients. Figure 1 Figure 1. Disclosures Vasileiou: Allovir: Consultancy. Tzannou: Gileas: Honoraria; Allovir: Current equity holder in publicly-traded company. Kuvalekar: Allovir: Consultancy. Watanabe: Allovir: Consultancy. Grilley: QB Regulatory Consulting: Other: Ownership, project management support, Research Funding; Marker: Consultancy, Other: Regulatory and project management support; Allovir: Current equity holder in publicly-traded company, Other: Leadership. Hill: Incyte: Membership on an entity's Board of Directors or advisory committees. Omer: Allovir: Research Funding. Gottschalk: Tessa Therapeutics: Consultancy; Immatics: Membership on an entity's Board of Directors or advisory committees; Other: Other: patents and patent applications in the field of cancer cell and gene therapy ; Tidal: Consultancy; Novartis: Consultancy; Catamaran Bio: Consultancy. Heslop: Gilead: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Kiadis: Membership on an entity's Board of Directors or advisory committees; Kuur Therapeutics: Research Funding; GSK: Membership on an entity's Board of Directors or advisory committees; Allovir: Current equity holder in publicly-traded company; Tessa Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Marker Therapeutics: Current equity holder in publicly-traded company; Fresh Wind Biotherapies: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees. Rooney: Allogene: Patents & Royalties; Bellicum: Patents & Royalties; Bluebird: Current equity holder in publicly-traded company; Allovir: Current equity holder in publicly-traded company; Alimera: Consultancy; Memgen: Consultancy; TScan Therapeutics: Consultancy; Takeda: Patents & Royalties; Marker: Current equity holder in publicly-traded company; Tessa: Consultancy, Other: Leadership, Research Funding. Vera: Allovir: Consultancy, Current equity holder in publicly-traded company, Other: Leadership, travel , accomodations, expenses, Patents & Royalties; Marker: Current Employment, Other: Travel, Accomodations, Expenses, Patents & Royalties, Research Funding. Leen: Allovir: Consultancy, Current equity holder in publicly-traded company; Marker: Current equity holder in publicly-traded company.

Purpose Improvement of cure rates for patients treated with allogeneic hematopoietic stem-cell transplantation (HSCT) will require efforts to decrease treatment-related mortality from severe viral infections. Adoptively transferred virus-specific T cells (VSTs) generated from eligible, third-party donors could provide broad antiviral protection to recipients of HSCT as an immediately available off-the-shelf product. Patient and Methods We generated a bank of VSTs that recognized five common viral pathogens: Epstein-Barr virus (EBV), adenovirus (AdV), cytomegalovirus (CMV), BK virus (BKV), and human herpesvirus 6 (HHV-6). The VSTs were administered to 38 patients with 45 infections in a phase II clinical trial. Results A single infusion produced a cumulative complete or partial response rate of 92% (95% CI, 78.1% to 98.3%) overall and the following rates by virus: 100% for BKV (n = 16), 94% for CMV (n = 17), 71% for AdV (n = 7), 100% for EBV (n = 2), and 67% for HHV-6 (n = 3). Clinical benefit was achieved in 31 patients treated for one infection and in seven patients treated for multiple coincident infections. Thirteen of 14 patients treated for BKV-associated hemorrhagic cystitis experienced complete resolution of gross hematuria by week 6. Infusions were safe, and only two occurrences of de novo graft-versus host disease (grade 1) were observed. VST tracking by epitope profiling revealed persistence of functional VSTs of third-party origin for up to 12 weeks. Conclusion The use of banked VSTs is a feasible, safe, and effective approach to treat severe and drug-refractory infections after HSCT, including infections from two viruses (BKV and HHV-6) that had never been targeted previously with an off-the-shelf product. Furthermore, the multispecificity of the VSTs ensures extensive antiviral coverage, which facilitates the treatment of patients with multiple infections.

Human metapneumovirus (hMPV) is a respiratory virus detected in ≥9% of allogeneic hematopoietic stem cell transplant (HSCT) recipients, in whom it can cause significant morbidity and mortality. Given the lack of effective antivirals, we investigated the potential for immunotherapeutic intervention, using adoptively transferred T cells. Thus, we characterized the cellular immune response to the virus and identified F, N, M2-1, M, and P as immunodominant target antigens. Reactive T cells were polyclonal (ie, they expressed CD4 and CD8), T-helper type 1 polarized, and polyfunctional (ie, they produced interferon γ, tumor necrosis factor α, granulocyte-macrophage colony-stimulating factor, and granzyme B), and they were able to kill autologous antigen-loaded targets. The detection of hMPV-specific T cells in HSCT recipients who endogenously controlled active infections support the clinical importance of T-cell immunity in mediating protective antiviral effects. Our results demonstrate the feasibility of developing an immunotherapy for immunocompromised patients with uncontrolled infections.

Parainfluenza virus type 3 (PIV3) infections are a major cause of morbidity and mortality in immunocompromised individuals, with no approved therapies. Our group has demonstrated the safety and efficacy of adoptively transferred virus-specific T cells for the prevention and treatment of a broad range of viral infections including BK virus, cytomegalovirus, adenovirus, human herpesvirus 6, and Epstein-Barr virus. However, this approach is restricted to well-characterized viruses with known immunogenic/protective T-cell target antigens, precluding extension to PIV3. We now characterize the cellular immune response to all 7 PIV3-encoded antigens in 17 healthy donors and define a hierarchy of immunogenicity based on the frequency of responding donors and the magnitude of specific cells. We show that reactive populations of both CD4+ and CD8+ T cells are capable of producing Th1-polarized effector cytokines and killing PIV3-expressing targets. Furthermore, we confirm the clinical relevance of these cells by demonstrating a direct correlation between the presence of PIV3-specific T cells and viral control in allogeneic hematopoietic stem cell transplant recipients. Taken together, our findings support the clinical use of PIV3-specific T cells produced with our Good Manufacturing Practice-compliant manufacturing process, in immunocompromised patients with uncontrolled infections.

Background With >36 years of data collected, PIDTC prospective (6901) and retrospective (6902) natural history studies provide an unprecedented opportunity to study hematopoietic cell transplantation (HCT) outcomes for SCID over time. Methods Patients in this 6901/6902 analysis met PIDTC diagnostic criteria for SCID and underwent HCT. Categorial variables were analyzed between decades (a) 1982-89 (b) 1990-99 (c) 2000-09 (d) 2010-18 using the chi-square test. Continuous outcomes were compared using the Kruskal-Wallis test. Kaplan-Meier method was used for estimates of overall survival (OS). Results 896 children with typical (n=742) and atypical (n=154) SCID requiring HCT between 1982-2018 were enrolled. Diagnosis of SCID for reasons other than family history or newborn screening was common (60%) in early cohorts (a-c) dropping to 30% in cohort (d). Distribution of SCID genotypes changed over time (Fig 1), and novel/unknown genotypes also decreased from (a) 53% to (d) 13%, p Conclusion This longitudinal data set, spanning the implementation of NBS and advancements in diagnostics and supportive care, highlights improved OS after HCT for SCID, including alternative donors. Exploration of decreased toxicity approaches that maintain high OS and engraftment are warranted.

Allogeneic hematopoietic stem cell transplant (HSCT) for relapsed pediatric non-Hodgkin lymphoma (NHL) is often reserved for patients with certain NHL subtypes or high-risk disease whereas the remainder receive autologous HSCT. Given the aggressive nature of pediatric NHL, we performed allogeneic HSCTs for all patients regardless of disease risk. We report overall survival (OS) and prognostic variables in 36 pediatric patients who underwent allogeneic HSCT between 1998 and 2016. OS at 3 years was 67%. The 3-year OS varied based on NHL subtype: 100% for anaplastic large cell lymphoma (n = 14), 63% for diffuse large B-cell lymphoma (n = 8), 17% for lymphoblastic lymphoma (LL; n = 9) and 80% for other subtypes combined (n = 5). Disease status influenced outcome with 3-year OS of 100% for patients in complete remission (n = 15), 59% with partial remission (PR; n = 17), and 0% with progressive/stable disease (n = 3) (P = .004). Of the 17 patients in PR, all 6 with LL died of relapsed disease, whereas the other 11 attained remission after HSCT and remained disease-free. The cumulative incidence of relapse after HSCT for LL was 78% compared with 15% for all other NHL subtypes combined (P < .0001). Cumulative incidence of nonrelapse mortality (NRM) was low in our cohort at 6%. Hence, allogeneic HSCT is a well-tolerated and useful therapeutic option with low rates of NRM and relapse for all NHL subtypes except LL with active disease at HSCT.

Cytomegalovirus (CMV) infections remain a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT), and standard antiviral therapies are associated with significant side effects and development of drug-resistant mutants. Adoptively transferred donor-derived CMV-specific T cells (CMVSTs) can provide an alternative treatment modality with few side effects but are not widely available due to their patient-specific nature. Here we report the establishment and use of a bank of CMVSTs derived from just 8 CMV-seropositive donors, with HLA types representing the diverse US population, as an “off-the-shelf” therapy to treat drug-refractory infections. To date, we have screened 29 patients for study participation and identified a suitable line, with ≥2 of 8 shared HLA antigens, for 28 (96.6%) patients with a median of 4 shared HLA antigens. Of these, 10 patients with persistent/refractory CMV infections or disease were eligible for treatment; a single infusion of cells produced 3 partial responses and 7 complete responses, for a cumulative response rate of 100% (95% confidence interval, 69.2-100) with no graft-versus-host disease, graft failure, or cytokine release syndrome. Potential wider use of the tested CMVSTs across transplant centers is made more feasible by our ability to produce sufficient material to generate cells for >2000 infusions from a single donor collection. Our data indicate that a “mini” bank of CMVSTs prepared from just 8 well-chosen third-party donors can supply the majority of patients with an appropriately matched line that produces safe and effective anti-CMV activity post-HSCT.

Wiskott-Aldrich syndrome (WAS) is an X-linked disease caused by mutations in the WAS gene, leading to thrombocytopenia, eczema, recurrent infections, autoimmune disease, and malignancy. Hematopoietic cell transplantation (HCT) is the primary curative approach, with the goal of correcting the underlying immunodeficiency and thrombocytopenia. HCT outcomes have improved over time, particularly for patients with HLA-matched sibling and unrelated donors. We report the outcomes of 129 patients with WAS who underwent HCT at 29 Primary Immune Deficiency Treatment Consortium centers from 2005 through 2015. Median age at HCT was 1.2 years. Most patients (65%) received myeloablative busulfan-based conditioning. With a median follow-up of 4.5 years, the 5-year overall survival (OS) was 91%. Superior 5-year OS was observed in patients 95%) vs low-level (5%-49%) donor myeloid engraftment. In summary, HCT outcomes for WAS have improved since 2005, compared with prior reports. HCT at a younger age continues to be associated with superior outcomes supporting the recommendation for early HCT. High-level donor myeloid engraftment is important for platelet reconstitution after either myeloablative or busulfan-containing reduced intensity conditioning. (This trial was registered at www.clinicaltrials.gov as #NCT02064933.)

Serious viral infections, due to delayed immune reconstitution, are a leading cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). Thus, many transplant centers prospectively track cellular immune recovery by evaluating absolute cell numbers and the phenotypic profile of reconstituting T cell subsets to identify individuals who are at highest risk of infection. Conventional assessments, however, fail to measure either the antigen specificity or functional capacity of reconstituting cells—both factors that correlate with endogenous antiviral protection. In this pilot study, we sought to address this limitation by prospectively investigating the tempo of endogenous immune reconstitution in a cohort of 23 pediatric HSCT patients using both quantitative (flow cytometry) and qualitative (IFNγ ELISpot) measures, which we correlated with either the presence or absence of infections associated with cytomegalovirus, adenovirus, Epstein-Barr virus, BK virus, human herpes virus 6, respiratory syncytial virus, parainfluenza, influenza, and human metapneumovirus. We present data spanning 12 months post-transplant demonstrating the influence of conditioning on immune recovery and highlighting the differential impact of active viral replication on the quantity and quality of reconstituting cells. Judicious use of standard (phenotypic) and novel (functional) monitoring strategies can help guide the clinical care and personalized management of allogenic HSCT recipients with infections.

IntroductionInflammatory bowel disease (IBD) affects approximately 1/3 of patients with chronic granulomatous disease (CGD). Comprehensive investigation of the effect of allogeneic hematopoietic cell transplantation (HCT) on CGD IBD and the impact of IBD on transplant outcomes is lacking.MethodsWe collected data retrospectively from 145 patients with CGD who had received allogeneic HCT at 26 Primary Immune Deficiency Treatment Consortium (PIDTC) centers between January 1, 2005 and June 30, 2016.ResultsForty-nine CGD patients with IBD and 96 patients without IBD underwent allogeneic HCT. Eighty-nine percent of patients with IBD and 93% of patients without IBD engrafted (p = 0.476). Upper gastrointestinal acute GVHD occurred in 8.5% of patients with IBD and 3.5% of patients without IBD (p = 0.246). Lower gastrointestinal acute GVHD occurred in 10.6% of patients with IBD and 11.8% of patients without IBD (p = 0.845). The cumulative incidence of acute GVHD grades II-IV was 30% (CI 17-43%) in patients with IBD and 20% (CI 12-29%) in patients without IBD (p = 0.09). Five-year overall survival was equivalent for patients with and without IBD: 80% [CI 66-89%] and 83% [CI 72-90%], respectively (p = 0.689). All 33 surviving evaluable patients with a history of IBD experienced resolution of IBD by 2years following allogeneic HCT.ConclusionsIn this cohort, allogeneic HCT was curative for CGD-associated IBD. IBD should not contraindicate HCT, as it does not lead to an increased risk of mortality. This study is registered at clinicaltrials.gov NCT02082353.

Adoptive transfer of virus-specific T cells (VSTs) has been shown to be safe and effective in stem cell transplant recipients. However, the lack of virus-experienced T cells in donor cord blood (CB) has prevented the development of ex vivo expanded donor-derived VSTs for recipients of this stem cell source. Here we evaluated the feasibility and safety of ex vivo expansion of CB T cells from the 20% fraction of the CB unit in pediatric patients receiving a single CB transplant (CBT). In 2 clinical trials conducted at 2 separate sites, we manufactured CB-derived multivirus-specific T cells (CB-VSTs) targeting Epstein-Barr virus (EBV), adenovirus, and cytomegalovirus (CMV) for 18 (86%) of 21 patients demonstrating feasibility. Manufacturing for 2 CB-VSTs failed to meet lot release because of insufficient cell recovery, and there was 1 sterility breach during separation of the frozen 20% fraction. Delayed engraftment was not observed in patients who received the remaining 80% fraction for the primary CBT. There was no grade 3 to 4 acute graft-versus-host disease (GVHD) associated with the infusion of CB-VSTs. None of the 7 patients who received CB-VSTs as prophylaxis developed end-organ disease from CMV, EBV, or adenovirus. In 7 patients receiving CB-VSTs for viral reactivation or infection, only 1 patient developed end-organ viral disease, which was in an immune privileged site (CMV retinitis) and occurred after steroid therapy for GVHD. Finally, we demonstrated the long-term persistence of adoptively transferred CB-VSTs using T-cell receptor-Vβ clonotype tracking, suggesting that CB-VSTs are a feasible addition to antiviral pharmacotherapy.

High risk or relapsed pediatric acute myeloid leukemia (AML) is potentially curable with allogeneic hematopoietic stem cell transplantation (HSCT). Significant improvements have been made with supportive care practices, but there are limited HSCT outcome data for pediatric AML patients in the contemporary era. We report retrospective data in 87 pediatric patients with high risk or relapsed AML, who underwent HSCT at a single institution between 2008 and 2018. The median age at time of HSCT was 8 years (range: 0.6-20 years). Forty three patients (49%) were transplanted in CR1, 18 (21%) in CR2, and 26 (30%) with active disease (defined as any evidence of disease at the time of HSCT). Patients were transplanted using matched related (MRD, n=21), matched unrelated (MUD, n=25), mismatched unrelated (MMUD, n=15), haplo-identical (haplo, n=12) or umbilical cord blood (UCB, n=14) grafts. The majority of patients (78/87, 90%) received myeloablative conditioning. MRD and UCB graft recipients did not receive serotherapy. All other graft recipients (n=52) received serotherapy, the majority using an alemtuzumab-based conditioning regimen, 42/52 (81%). Haplo-identical transplants were performed using CD34+ selected grafts. Three-year overall survival (OS) and disease free survival (DFS) for the entire cohort were 52% (95% CI: 41-62%) and 49% (95% CI: 38-59%) respectively. OS differed significantly according to disease status at time of transplant (p=0.018), with 3 year OS: 60%, (95% CI: 43-74%) for those in CR1, 56%, (95% CI: 31-75%) for those in CR2 and 34% (95% CI: 17-52%) for those with active disease. OS differed by donor type (p=0.058). OS was comparable for patients with MRD (71%, 95% CI: 46-86%) and 10/10 MUD (59%, 95% CI: 37-75%) (p=0.67). Patients with alternate donor sources had worse outcomes (MMUD 33%, 95% CI: 10-59%; UCB 43%, 95% CI: 18-66%; Haplo 33%, 95% CI: 10-59%) as compared to MRD (MMUD vs MRD, p=0.042, UCB vs MRD, p=0.046, haplo vs MRD p=0.017). There was a low incidence of Grade III-IV acute GVHD (8%, n=7) and extensive chronic GVHD (9%, n=7) likely secondary to the use of alemtuzumab-based conditioning regimens. The 3-year non-relapse mortality was low at 11% (95% CI: 5-19%). The primary cause of death was relapse, with a 3-year cumulative incidence of relapse of 40%, (95% CI: 30-50%). Patients with active disease at HSCT had significantly higher cumulative incidence of relapse (sHR: 2.42, 95% CI: 1.18-4.95, p=0.016) compared to patients in remission. In the contemporary era, outcomes after allogeneic HSCT are comparable for MRD and 10/10 MUD for pediatric AML. Myeloablative and alemtuzumab based conditioning regimens were well tolerated with low rates of NRM and GVHD. Relapse remains the major cause of treatment failure. Future trials evaluating use of cellular therapies and targeted agents post-HSCT will be needed.

Introduction There is no consensus regarding the best donor for children undergoing stem cell transplantation in the absence of a matched related donor (MRD), especially for patients with nonmalignant diseases. The incidence of infections, GvHD, and graft failure remain major problems. Objectives Evaluate outcome for patients undergoing UCBT conditioned without serotherapy, which is as an attractive option for these patients because of immediate availability, lower incidence of GvHD, and high probability of adequate cell dose for young patients. Methods From 2008-2019, we performed UCBT in 84 children, median age 10 mo. (range, 2–108 mo.) with: ALL (13), AML (15), MDS (5), SCID (36), IPEX (2), LAD (1), WAS (1), CGD (1), metabolic disorders (4), HLH (2), and hematologic disorders (4). Eleven patients (30%) with malignancies had minimal residual disease present before UCBT. Five patients with AML had chloromas present prior to UCBT. 26 patients with immune deficiencies had persistent infections at transplant. All patients were enrolled on prospective clinical trials. Pts with AML/ MDS/ or nonmalignant disorders received busulfan, cyclophosphamide, and fludarabine; pts with ALL received TBI (12Gy), cyclophosphamide, and fludarabine. No patient was treated with serotherapy. All cord blood units were matched 5 or 6/6 HLA antigens at A, B and allele at DR. Results Infused cord blood contained median TNC 15 × 107 kg (range, 5.1 – 26.4). All evaluable patients engrafted by day 42. The median time to neutrophil and platelet recovery were 18 days (range, 6-42d) and 35 days (range,22-85d), respectively. All evaluable patients achieved full donor chimerism (defined as > 95% donor cells in peripheral blood by day +42). The overall survival (OS) at 2 years was 75% with a median follow up of 5 years (range: 0.5 – 11yr). The OS for patients with SCID was 92% (33/36) at 2 years with engraftment of all lineages. The cumulative incidence of aGvHD grade II-IV by day 100 was 9% (n=8) with only 3 patients having grade IV. No pt developed cGvHD. Twenty-one patients died, 13/21, 62% died from disease relapse or disease progression. Treatment related mortality occurred for 7 patients; severe GvHD (n=2) and MOF (n=5). No infection related mortality was seen. Conclusion We conclude that lacking a MRD, UCBT following myeloablative conditioning without serotherapy is an excellent curative option in young children. Our experience highlights minimal treatment related mortality, rapid engraftment, resolutions of antecedent infections, and a low incidence of GvHD. These results translate in a better quality of life for these young patients.

Introduction Allogeneic hematopoietic stem cell transplantation (HSCT) is a curative treatment for transfusion-dependent b-thalassemia (TDT). Application of alternative donor HSCT for TDT is more accepted as rates of graft failure (GF) and GVHD decline. Alemtuzumab is a CD52 monoclonal antibody with potent lymphocytic activity that can reduce GVHD risk, though infectious associations have limited its use. We hypothesize that the addition of alemtuzumab to standard myeloablative conditioning in HSCT for TDT will reduce rates of GVHD without affecting engraftment or transplant-related mortality (TRM). Methods We retrospectively reviewed engraftment, GVHD, and survival for TDT patients (pts) who underwent HSCT at Texas Children's Hospital between 2004-2018. All pts received myeloablative conditioning with IV targeted busulfan (AUC of 800-1200 μM per minute), cyclophosphamide 50 mg/kg daily for 4 days, and IV alemtuzumab (5-15kg= 3mg; 15-30kg=5mg; >30kg=10mg) from d -5 through d -2. Pts receiving MUD/MMUD HSCT additionally received fludarabine 30 mg/m2 for 4 days. GVHD prophylaxis included methotrexate (d +1,3,6,11) and a calcineurin inhibitor. Results Twenty-one consecutive pts underwent MRD (10), MUD (9), or MMUD (2) HSCT with a median age at HSCT of 6.5 yrs (range: 1.5-14.9). Stem cell source consisted of bone marrow (17), peripheral blood (3), MRD umbilical cord and marrow (1). Neutrophil engraftment (ANC>500/ml x 3 d) was achieved in all patients at a median of 19 d (range: 13-29). Median platelet engraftment (platelet > 20,000 × 7 d without transfusion) was 35.5 d (range: 15-123). Median RBC engraftment (Hb >8 g/dL x 7 d without transfusion) was 24 d (range: 10-115). No GF was observed. Poor graft function (PGF) was seen in 2 pts (9.5%) requiring stem cell boost or 2nd HSCT. Overall incidence of acute (grade II-IV) and chronic GVHD (all limited) of 9.5% and 14.2%, respectively. Five-year overall survival was 89.9% with a median follow-up of 3.6 yrs (range: 0-14.4). Two deaths occurred secondary to infections complications in the setting of PGF and GVHD, respectively. Conclusion Myeloablative conditioning with alemtuzumab minimized the incidence of severe GVHD with good overall survival. GF, GVHD, and TRM rates were improved from previous reports in TDT. PGF in our UD cohort was comparable to previous reports of engraftment complications. The addition of Alemtuzumab is a reasonable strategy to reduce GVHD risk in MRD and UD HSCT for TDT, though durability of engraftment after UD HSCT requires further investigation.

Introduction Hematopoietic stem cell transplant (HSCT) is a curative strategy for pediatric patients with high risk and relapsed Acute Lymphoblastic Leukemia (ALL), including those with Central Nervous System (CNS) involvement. There are limited data on the outcomes following HSCT in pediatric patients with ALL and CNS disease and no consensus on optimal CNS prophylaxis and treatment Methods We performed a retrospective chart review of pediatric patients who underwent HSCT for ALL from 2006-2016 at our institution. We compared outcomes for patients with CNS positive and CNS negative ALL. CNS positivity was defined as any CNS leukemic involvement either at original diagnosis of leukemia or relapse prior to HSCT. Results One hundred and thirty two patients were evaluated of which 82 (62%) were CNS negative and 50 (38%) were CNS positive. Patient and transplant characteristics were similar in both group except for disease status (Table 1). There was a higher proportion of patients with CR2/> relapse (36, 72%) in the CNS positive group compared to the CNS negative group (43, 52%) (p=0.029). Majority received myeloablative conditioning (MAC) that was TBI based in all but 3 patients. Cranial boost (CB) was given prior to HSCT to 30/50 CNS positive patient per institutional standards. Outcomes for both CNS positive and CNS negative patients were comparable (OS, DFS and Cumulative Incidence (CI) of relapse in patients that were CNS positive was 58%, 50% and 26% respectively and for CNS-negative: 68%, 66%, 23% respectively; P-values: 0.301,0.297, 0.896). In the CNS negative group, 0/23 relapses after transplant occurred in the CNS compared to 4/14 relapses in the CNS positive group. All 4 patients with CNS relapse post-transplant were in CR3 and had relapsed in the CNS at referral to HSCT. Two of the 4 received a reduced intensity regimen and 1 had not received a CB pre-HSCT due to prior CNS irradiation. Conclusion Our experience demonstrates that the outcomes after HSCT for pediatric patients with ALL with and without CNS involvement are comparable. For CNS positive patients the use of TBI-based MAC regimens with CB pre-transplant is associated with similar rates of DFS and relapse without deleterious effect on OS compared to the CNS negative group, despite a higher proportion coming to HSCT in CR2/> relapse. No additional CNS prophylaxis is required for patients that are CNS negative.

Relapse of hematological malignancies after hematopoietic stem cell transplantation (HCT) is associated with poor prognosis. A second HCT represents one of the few therapeutic options for these high-risk patients. For children undergoing second HCT, the outcome data are particularly limited. We, therefore, conducted a retrospective single-institution study and report the outcomes and prognostic variables associated with overall survival (OS) and relapse in 43 pediatric patients who underwent a second HCT between 2000 and 2013. Eleven of the 43 patients who underwent transplantation remain alive and disease-free at a median follow-up of 49 months (range, 5 to 127 months). The 5-year probability of OS for the entire cohort was 24%. Patients who had early relapse (6 months), with 5-year OS at 11% versus 34%, respectively (hazard ratio [HR], 2.24; 95% confidence interval [CI], 1.21 to 4.93; P = .013). Active disease at time of second HCT was also associated with a significantly increased risk of relapse (subdistribution hazard ratio [SHR], 2.36; P = .049) for the entire cohort and relapse was the most frequent cause of death (23 of 32; 72%). On subgroup analysis for the 34 patients with leukemia alone, presence of active disease was associated both with a significant decrease in OS (SHR, 2.28; 95% CI, 1.02 to 5.09; P = .044) and significant increase in the rate of relapse (SHR, 2.46; P = .046). By contrast, underlying disease, donor source, conditioning regimen, or development of GVHD did not modify OS or rate of relapse. Hence, a second HCT appears to be a useful therapeutic option in children with relapsed hematological malignancies that is most likely to benefit those individuals with late onset of relapse and with low disease burden at the time of transplantation.