A prospective multi-institutional study of eculizumab to treat high-risk stem cell transplantation-associated TMA.

ABSTRACT: High-risk, complement mediated, untreated transplant-associated thrombotic microangiopathy (hrTMA) has dismal outcomes due to multi-organ dysfunction syndrome (MODS). The complement C5 blocker eculizumab shows promising results in hrTMA, but has not been prospectively studied in hematopoietic stem cell transplant (HCT) recipients. We performed the first multi-institutional prospective study in children and young adults to evaluate eculizumab as an early targeted intervention for hrTMA/MODS. We hypothesized that eculizumab would more than double survival in HCT recipients with hrTMA, compared to our prior study of prospectively screened, untreated hrTMAs serving as historical controls. HrTMA features (elevated terminal complement (sC5b-9) and proteinuria measured by random urine protein/creatinine ratio (≥1mg/mg)) were required for inclusion. The primary endpoint was survival at 6 six-months from hrTMA diagnosis. Secondary endpoints were cumulative incidence of MODS 6 months after hrTMA diagnosis and 1-year posttransplant survival. Eculizumab dosing included intensive loading, induction, and maintenance phases for up to 24 weeks of therapy. All 21 evaluated study subjects had MODS. Primary and secondary study endpoints were met by demonstrating survival of 71% (P < .0001) 6 months after hrTMA diagnosis and 62% 1 year after transplant. Of fifteen survivors, 11 (73%) fully recovered organ function and are well. Our study demonstrates significant improvement in survival and recovery of organ function in hrTMA using an intensified eculizumab dosing and real time biomarker monitoring. This study serves as a benchmark for planning future studies that should focus on preventative measures or targeted therapy to be initiated prior to organ injury. This trial was registered at www.clinicaltrials.gov as #NCT03518203.

A randomized phase 2 trial of oral vitamin A for graft-versus-host disease in children and young adults.

ABSTRACT: Vitamin A plays a key role in the maintenance of gastrointestinal homeostasis and promotes a tolerogenic phenotype in tissue resident macrophages. We conducted a prospective randomized double-blinded placebo-controlled clinical trial in which 80 recipients of hematopoietic stem cell transplantation (HSCT) were randomized 1:1 to receive pretransplant high-dose vitamin A or placebo. A single oral dose of vitamin A of 4000 IU/kg, maximum 250 000 IU was given before conditioning. The primary end point was incidence of acute graft-versus-host disease (GVHD) at day +100. In an intent-to-treat analysis, incidence of acute GVHD was 12.5% in the vitamin A arm and 20% in the placebo arm (P = .5). Incidence of acute gastrointestinal (GI) GVHD was 2.5% in the vitamin A arm (P = .09) and 12.5% in the placebo arm at day +180. Incidence of chronic GVHD was 5% in the vitamin A arm and 15% in the placebo arm (P = .02) at 1 year. In an "as treated" analysis, cumulative incidence of acute GI GVHD at day +180 was 0% and 12.5% in recipients of vitamin A and placebo, respectively (P = .02), and cumulative incidence of chronic GVHD was 2.7% and 15% in recipients of vitamin A and placebo, respectively (P = .01). The only possibly attributable toxicity was asymptomatic grade 3 hyperbilirubinemia in 1 recipient of vitamin A at day +30, which self-resolved. Absolute CCR9+ CD8+ effector memory T cells, reflecting gut T-cell trafficking, were lower in the vitamin A arm at day +30 after HSCT (P = .01). Levels of serum amyloid A-1, a vitamin A transport protein with proinflammatory effects, were lower in the vitamin A arm. The vitamin A arm had lower interleukin-6 (IL-6), IL-8, and suppressor of tumorigenicity 2 levels and likely a more favorable gut microbiome and short chain fatty acids. Pre-HSCT oral vitamin A is inexpensive, has low toxicity, and reduces GVHD. This trial was registered at www.ClinicalTrials.gov as NCT03202849.

Detection of Bronchiolitis Obliterans Syndrome after Pediatric Hematopoietic Stem Cell Transplantation: An Official American Thoracic Society Clinical Practice Guideline.

Background: Many children undergo allogeneic hematopoietic stem cell transplantation (HSCT) for the treatment of malignant and nonmalignant conditions. Unfortunately, pulmonary complications occur frequently post-HSCT, with bronchiolitis obliterans syndrome (BOS) being the most common noninfectious pulmonary complication. Current international guidelines contain conflicting recommendations regarding post-HSCT surveillance for BOS, and a recent NIH workshop highlighted the need for a standardized approach to post-HSCT monitoring. As such, this guideline provides an evidence-based approach to detection of post-HSCT BOS in children. Methods: A multinational, multidisciplinary panel of experts identified six questions regarding surveillance for, and evaluation of, post-HSCT BOS in children. A systematic review of the literature was undertaken to answer each question. The Grading of Recommendations, Assessment, Development, and Evaluation approach was used to rate the quality of evidence and the strength of recommendations. Results: The panel members considered the strength of each recommendation and evaluated the benefits and risks of applying the intervention. In formulating the recommendations, the panel considered patient and caregiver values, the cost of care, and feasibility. Recommendations addressing the role of screening pulmonary function testing and diagnostic tests in children with suspected post-HSCT BOS were made. Following a Delphi process, new diagnostic criteria for pediatric post-HSCT BOS were also proposed. Conclusions: This document provides an evidence-based approach to the detection of post-HSCT BOS in children while also highlighting considerations for the implementation of each recommendation. Further, the document describes important areas for future research.

Third-party virus-specific T cells for the treatment of double-stranded DNA viral reactivation and posttransplant lymphoproliferative disease after solid organ transplant.

Reactivation or primary infection with double-stranded DNA viruses is common in recipients of solid organ transplants (SOTs) and is associated with significant morbidity and mortality. Treatment with conventional antiviral medications is limited by toxicities, resistance, and a lack of effective options for adenovirus (ADV) and BK polyomavirus (BKPyV). Virus-specific T cells (VSTs) have been shown to be an effective treatment for infections with ADV, BKPyV, cytomegalovirus (CMV), and Epstein-Barr virus (EBV). Most of these studies have been conducted in stem cell recipients, and no large studies have been published in the SOT population to date. In this study, we report on the outcome of quadrivalent third-party VST infusions in 98 recipients of SOTs in the context of an open-label phase 2 trial. The 98 patients received a total of 181 infusions, with a median of 2 infusions per patient. The overall response rate was 45% for BKPyV, 65% for cytomegalovirus, 68% for ADV, and 61% for Epstein-Barr virus. Twenty percent of patients with posttransplant lymphoproliferative disorder had a complete response and 40% of patients had a partial response. All the VST infusions were well tolerated. We conclude that VSTs are safe and effective in the treatment of viral infections in SOT recipients.

Quercetin ameliorates XIAP deficiency-associated hyperinflammation.

XIAP (X-linked inhibitor of apoptosis) deficiency is a rare inborn error of immunity. XIAP deficiency causes hyperinflammatory disease manifestations due to dysregulated TNF (tumor necrosis factor)-receptor signaling and NLRP3 (NOD- [nucleotide-binding oligomerization domain], LRR- [leucine-rich repeat] and pyrin domain-containing protein 3) inflammasome function. Safe and effective long-term treatments are needed and are especially important to help prevent the need for high-risk allogeneic hematopoietic cell transplantation. Here we evaluated inflammasome inhibitors as potential therapeutics with a focus on the natural flavonoid antioxidant quercetin. Bone marrow (BM)-derived macrophages were derived from XIAP-deficient or wild-type (WT) mice. Human monocytes were obtained from control or XIAP-deficient patients. Cells were stimulated with TLR (Toll-like receptor) agonists or TNF-α ± inhibitors or quercetin. For in vivo lipopolysaccharide (LPS) challenge experiments, XIAP-deficient or WT mice were fed mouse chow ± supplemental quercetin (50 mg/kg per day exposure) for 7 days followed by a challenge with 10 ng/kg LPS. IL-1ß (interleukin-1ß) and IL-18 were measured by ELISA (enzyme-linked immunosorbent assay). In murine studies, quercetin prevented IL-1ß secretion from XIAP knockout cells following TLR agonists or TNF-α stimulation (P < .05) and strongly reduced constitutive production of IL-18 by both WT and XIAP-deficient cells (P < .05). At 4 hours after in vivo LPS challenge, blood levels of IL-1ß and IL-18 were significantly decreased in mice that had received quercetin-supplemented chow (P < .05). In experiments using human cells, quercetin greatly reduced IL-1ß secretion by monocytes following TNF-α stimulation (P < .05). Our data suggest that quercetin may be an effective natural therapeutic for the prevention of XIAP deficiency-associated hyperinflammation. Clinical trials, including careful pharmacokinetic and pharmacodynamic studies to ensure that effective levels of quercetin can be obtained, are warranted.

Susceptibility to BK polyomavirus-associated hemorrhagic cystitis in children undergoing allogeneic transplant.

Not available.

Pre-transplant glomerular hyperfiltration is not a risk factor for increased renal morbidity and mortality in pediatric stem cell transplant patients.

Low glomerular filtration rate (GFR) prior to stem cell transplant (SCT) is associated with increased morbidity and mortality. The implications of abnormally high GFRs, or glomerular hyperfiltration, prior to SCT are unknown. Twenty-two of 74 consecutive pediatric SCT patients over 2 years old at a single center were hyperfiltrating prior to SCT, median nuclear medicine GFR 154 mL/min/1.73 m2 [interquartile range: 146-170]. There was no association between hyperfiltration and any transplant demographics, nor between hyperfiltration and acute kidney injury (p = .8), renal replacement therapy (p = .63), 1-year event-free survival (p = 1), or abnormal creatinine-based estimated GFR at a median follow-up of 4.7 years (p = .73).

Invasive fungal infections are rare in pediatric and young adult autologous hematopoietic stem cell transplant patients.

BACKGROUND: Pediatric and young adult patients undergoing autologous hematopoietic stem cell transplant (auto-HSCT) face a crucial, yet understudied, risk of invasive fungal infections (IFI), especially compared to allogeneic transplants. This gap underscores the need for research in pediatric patients undergoing auto-HSCT. Our objective was to evaluate the incidence of IFI in pediatric and young adult patients during the first year after auto-HSCT. MATERIALS AND METHODS: We conducted a single-center retrospective analysis of 150 pediatric and young adult auto-HSCT patients who underwent transplant from January 2013 to January 2023. We focused on IFI incidence within the first-year post transplant, using the European Organization for Research and Treatment of Cancer/Mycoses Study Group (EORTC/MSG) criteria for IFI identification. RESULTS: Among the 150 patients analyzed, with 240 unique transplant episodes, the primary indication was neuroblastoma (37.3%), and micafungin was extensively used for prophylaxis (82.7%). There was an absence of IFI from yeast and mold species, suggesting a low IFI risk in this cohort. The incidence of IFI in pediatric auto-HSCT recipients receiving micafungin primary antifungal prophylaxis is rare. CONCLUSIONS: The findings advocate for further research to refine prophylaxis guidelines and highlight the need for individualized risk assessment to optimize post-transplant care.

Social determinants of health predict health outcomes following pediatric allogeneic hematopoietic stem cell transplant.

BACKGROUND: Pediatric hematopoietic stem cell transplantation (HCT) is an intensive medical procedure that places substantial financial and logistical burdens on families and is associated with significant health risks, such as graft-versus-host disease (GVHD), and infections. The influence of the social determinants of health (SDoH) on outcomes following pediatric HCT is understudied. This study aimed to examine whether SDoH predicts outcomes following pediatric HCT. PROCEDURE: Data were collected from 84 children who received HCT (Mage  = 5.8 years, SD = 3.7) and their primary caregiver. Detailed demographic information was collected from caregivers at baseline, and child health information was extracted from the electronic medical records. Multivariate logistic regression was used to examine the association between SDoH and health outcomes within a 24-month period following pediatric HCT. RESULTS: After controlling for malignancy as reason for transplant and donor type, lower family income predicted the incidence of chronic GVHD. Neighborhood deprivation, total family income, public health insurance, caregiver relationship status, caregiver educational attainment, and perceived family financial difficulties did not predict acute GVHD or the number of infections. CONCLUSIONS: Total family income is a simple family indicator of SDoH that predicts chronic GVHD after pediatric allogeneic HCT. These findings provide further support for the importance of screening of child and family SDoH risks to ensure that fundamental needs can be met to mitigate potential health disparities for up to 2 years following pediatric HCT.

BK Polyomavirus Diversity After Hematopoietic Stem Cell Transplantation.

BK polyomavirus (BKPyV) infection is common after hematopoietic stem cell transplantation (HSCT) and is associated with the development of hemorrhagic cystitis (HC). The role that BKPyV plays in the pathogenesis of HC is not well characterized. We investigated the impact of BKPyV diversity on the development of HC using a previously established cohort of pediatric HSCT patients. There were 147 urine samples with quantifiable BKPyV at month 1 after HSCT; 137 (93.2%) were amplified using our in-house polymerase chain reaction approach and sent for next-generation sequencing. Subtype Ia was most frequent (61.3%), followed by subtype Ib1 (31.4%). The median viral load of subtype Ia samples was higher than for subtype Ib1 at month 1. Across the protein coding regions, APOBEC-induced mutations and signature patterns associated with HC were identified. This is the largest sequencing study of a single cohort of HSCT patients, providing a vast resource of sequence data for future analyses.

Phenotypes of adults with Fanconi anaemia.

The long-term outcomes of adults with Fanconi anaemia (FA) have improved with advances in haematopoietic stem cell transplantation (HSCT) and more detailed follow-up and screening guidelines. The phenotype of those who survive to adulthood may differ from the typical presentation of FA. We collected retrospective clinical data on adults with FA who received their care at the Cincinnati Children's Hospital Medical Center. In our final cohort of 52 patients, there were 29 females and 23 males, with median (range) age of 21 (18-37) years. Overall, 42 patients (81%) were alive at last follow-up. In all, 36 adults (69%) had undergone HSCT, including eight who had developed myelodysplasia or acute myeloid leukaemia. Eight (15%) developed squamous cell carcinoma. Endocrine complications were common, including hypothyroidism (42%), diabetes (10%), low body mass index (31%) and low bone mineral density (51%). The majority of adults with FA were employed (52%) or full-time students (13%). A significant subset of patients with FA are surviving into adulthood without requiring HSCT. Endocrine abnormalities and the development of solid tumours complicate adulthood. With improved survival outcomes following HSCT and more aggressive malignancy screening protocols, ongoing longitudinal analysis will be important to further characterise this cohort and the phenotype of untransplanted adults with FA.

Gonadal function in pediatric Fanconi anemia patients treated with hematopoietic stem cell transplant.

Gonadal dysfunction and reduced fertility are clinical manifestations well described in patients with Fanconi anemia (FA) and following hematopoietic stem cell transplantation (HSCT). It is difficult to differentiate gonadal dysfunction from the primary disease itself or from HSCT procedures. Therefore, it is important to manage expectations about gonadal failure and infertility for all patients with FA, regardless of the HSCT status. We performed a retrospective analysis of 98 pediatric patients with FA who were transplanted between July 1990 and June 2020 to evaluate the incidence of gonadal dysfunction in female and male patients with FA. New-onset premature ovarian insufficiency (POI) was diagnosed in a total of 30 (52.6%) patients. Follicle-stimulating hormone and luteinizing hormone levels were increased in patients diagnosed with POI. Anti- Mullerian hormone levels declined in POI patients after HSCT (r2=0.21; P=0.001). Twenty (48.8%) male patients were diagnosed with testicular failure. Follicle-stimulating hormone levels increased after HSCT even in patients without testicular failure (r2=0.17; P=0.005). Inhibin B levels decreased over time after HSCT in patients with testicular failure (r2=0.14; P=0.001). These data indicate brisk decline in already impaired gonadal function in transplanted children with FA.

Transcriptome analysis in acute gastrointestinal graft-versus host disease reveals a unique signature in children and shared biology with pediatric inflammatory bowel disease.

We performed transcriptomic analyses on freshly frozen (n=21) and paraffin-embedded (n=35) gastrointestinal (GI) biopsies from children with and without acute acute GI graft-versus-host disease (GvHD) to study differential gene expressions. We identified 164 significant genes, 141 upregulated and 23 downregulated, in acute GvHD from freshy frozen biopsies. CHI3L1 was the top differentially expressed gene in acute GvHD, involved in macrophage recruitment and bacterial adhesion. Mitochondrial genes were among the top downregulated genes. Immune deconvolution identified a macrophage cellular signature. Weighted gene co-expression network analysis showed enrichment of genes in the ERK1/2 cascade. Transcriptome data from 206 ulcerative colitis (UC) patients were included to uncover genes and pathways shared between GvHD and UC. Comparison with the UC transcriptome showed both shared and distinct pathways. Both UC and GvHD transcriptomes shared an innate antimicrobial signature and FCγ1RA/CD64 was upregulated in both acute GvHD (log-fold increase 1.7, P=0.001) and UC. Upregulation of the ERK1/2 cascade pathway was specific to GvHD. We performed additional experiments to confirm transcriptomics. Firstly, we examined phosphorylation of ERK (pERK) by immunohistochemistry on GI biopsies (acute GvHD n=10, no GvHD n=10). pERK staining was increased in acute GvHD biopsies compared to biopsies without acute GvHD (P=0.001). Secondly, plasma CD64, measured by enzyme-linked immunsorbant assay (n=85) was elevated in acute GI GvHD (P<0.001) compared with those without and was elevated in GVHD compared with inflammatory bowel disease (n=47) (P<0.001), confirming the upregulated expression seen in the transcriptome.

Durable remissions achieved with reinfusion of CD19-directed CAR-T despite failure to induce or maintain B-cell aplasia and single-center experience with reinfusion of tisagenlecleucel.

CD19-directed chimeric antigen receptor T lymphocytes (CAR-T) have led to durable remissions in children with refractory and/or multiply relapsed B-lymphoblastic leukemia. For those who relapse or lose B-cell aplasia post CAR-T, the role of CAR-T reinfusion is unclear. We report two cases of durable remission with tisagenlecleucel reinfusion despite failure to achieve or maintain B-cell aplasia, and compare these cases to six additional children who received multiple tisagenlecleucel infusions at our institution. Our experience suggests that reinfusion is safe and may be a definitive therapy for a small subset of patients. Reinfusion can also reintroduce remission and/or B-cell aplasia, allowing for subsequent therapies.

Complement blockade for TA-TMA: lessons learned from a large pediatric cohort treated with eculizumab.

Overactivated complement is a high-risk feature in hematopoietic stem cell transplant (HSCT) recipients with transplant-associated thrombotic microangiopathy (TA-TMA), and untreated patients have dismal outcomes. We present our experience with 64 pediatric HSCT recipients who had high-risk TA-TMA (hrTA-TMA) and multiorgan injury treated with the complement blocker eculizumab. We demonstrate significant improvement to 66% in 1-year post-HSCT survival in treated patients from our previously reported untreated cohort with same hrTA-TMA features that had 1-year post-HSCT survival of 16.7%. Responding patients benefited from a brief but intensive course of eculizumab using pharmacokinetic/pharmacodynamic-guided dosing, requiring a median of 11 doses of eculizumab (interquartile range [IQR] 7-20). Treatment was discontinued because TA-TMA resolved at a median of 66 days (IQR 41-110). Subjects with higher complement activation measured by elevated blood sC5b-9 at the start of treatment were less likely to respond (odds ratio, 0.15; P = .0014) and required more doses of eculizumab (r = 0.43; P = .0004). Patients with intestinal bleeding had the fastest eculizumab clearance, required the highest number of eculizumab doses (20 vs 9; P = .0015), and had lower 1-year survival (44% vs 78%; P = .01). Over 70% of survivors had proteinuria on long-term follow-up. The best glomerular filtration rate (GFR) recovery in survivors was a median 20% lower (IQR, 7.3%-40.3%) than their pre-HSCT GFR. In summary, complement blockade with eculizumab is an effective therapeutic strategy for hrTA-TMA, but some patients with severe disease lacked a complete response, prompting us to propose early intervention and search for additional targetable endothelial injury pathways.

Test-dose pharmacokinetics guided melphalan dose adjustment in reduced intensity conditioning allogeneic transplant for non-malignant disorders.

AIMS: We studied melphalan pharmacokinetics (PK) and feasibility of melphalan full-dose adjustment based on test-dose PK in children and young adults with non-malignant disorders (NMD) undergoing allogeneic hematopoietic cell transplantation (HCT) using reduced intensity conditioning (RIC) containing alemtuzumab, fludarabine and melphalan. METHODS: Patients received test-dose melphalan (10% of planned full-dose) prior to conditioning. Blood samples for PK were obtained around test and full-dose melphalan (140 mg/m2 or 4.7 mg/kg in patients <10 kg). Melphalan concentration was measured by liquid chromatography electrospray ionization tandem mass-spectrometry assay and data were analysed using a population-PK model and Bayesian estimation. Test and full-dose melphalan clearance estimates were evaluated by pairwise Wilcoxon test and Bland-Altman plot. RESULTS: Twenty-four patients undergoing 25 transplants were included in the final analysis. Patients received standard full-dose melphalan in 17 transplants, with median area under the concentration-time curve (AUC) of 5.5 mg*h/L (range, 3.0-9.5 mg*h/L). Patients received test-dose melphalan in 23 transplants with a test-dose PK predicted full-dose AUC range of 2.9-16.8 mg*h/L. In seven transplants where patients had baseline organ impairment, test-dose PK predicted higher exposure for standard full-dose (median AUC 13.8 mg*h/L). Melphalan full-dose was adjusted in these patients, with achievement of desired target AUC (3.6-5.4 mg*h/L) and no excess toxicity. Mean ratio of test-dose clearance to full-dose clearance was 1.03. Twenty of 22 patients (91%) were within the 95% confidence intervals of the clearance ratio. CONCLUSION: Melphalan test-dose PK reliably predicts full-dose PK and allows for accurate adjustment of full-dose melphalan in RIC-HCT for NMD. This approach can avoid excess toxicity from increased systemic exposure, especially in patients with organ impairment.

Comparison of the clinical phenotype and haematological course of siblings with Fanconi anaemia.

Fanconi anaemia (FA) is a genetic disorder due to mutations in any of the 22 FANC genes (FANCA-FANCW) and has high phenotypic variation. Siblings may have similar clinical outcome because they share the same variants; however, such association has not been reported. We present the detailed phenotype and clinical course of 25 sibling sets with FA from two institutions. Haematological progression significantly correlated between siblings, which was confirmed in an additional 55 sibling pairs from the International Fanconi Anemia Registry. Constitutional abnormalities were not concordant, except for a moderate degree of concordance in kidney abnormalities and microcephaly.

Experience with a Reduced Toxicity Allogeneic Transplant Regimen for Non-CGD Primary Immune Deficiencies Requiring Myeloablation.

PURPOSE: A need exists for reduced toxicity conditioning regimens that offer less toxicity while maintaining myeloablation, especially for primary immune deficiencies where myeloablation or high donor myeloid chimerism is required to achieve cure. We adapted a busulfan and fludarabine regimen by Gungor et al. for children and young adults undergoing allogeneic HCT for non-CGD primary immune deficiencies requiring myeloablation or high donor myeloid chimerism, and herein report our experience. METHODS: We retrospectively reviewed records of 41 consecutive patients who underwent allogeneic HCT for Wiskott-Aldrich syndrome (n = 12), primary HLH/XLP (n = 10), CD40L deficiency (n = 7), or other (n = 12) primary immune deficiencies with a conditioning regimen containing pharmacokinetic-guided busulfan dosing which achieved a cumulative AUC between 57 and 74 mg/L × h (65-80% of conventional myeloablative exposure), along with fludarabine and alemtuzumab or anti-thymocyte globulin at 3 transplant centers between 2014 and 2019. RESULTS: Forty-one patients underwent a first (n = 33) or second (n = 8) allogeneic HCT. Median age was 2.3 years (range, 0.3 years-19.8 years). All but one patient (97.5%) achieved neutrophil recovery at a median of 14 days (range, 11-34 days). One patient developed sinusoidal obstruction syndrome and two patients developed diffuse alveolar hemorrhage. Four patients developed grades II-IV acute GVHD. Three patients developed chronic GVHD. One-year overall survival was 90% (95% confidence interval [CI] 81-99%) and event-free survival was 83% (95% CI 71-94%). CONCLUSIONS: Our experience suggests that a reduced toxicity busulfan-fludarabine regimen offers low toxicity, low incidence of grades 2-4 GVHD, durable myeloid engraftment, and excellent survival, and may be considered for a variety of primary immune deficiencies where myeloablative HCT is desired.

Endothelial injury, F-actin and vitamin-D binding protein after hematopoietic stem cell transplant and association with clinical outcomes.

Endothelial injury after hematopoietic stem cell transplant is an important initiating factor for early transplant toxicities of thrombotic microangiopathy and acute graft versus host disease. We hypothesized that release of the angiopathic molecule filamentous actin from hematopoietic cells lysed during conditioning prior to stem cell transplant would be associated with clinical outcomes. We detected filamentous actin in the blood of 52% of stem cell transplant recipients in the first 14 days after transplant, and children with detectable filamentous actin had significantly elevated risk of thrombotic microangiopathy (p= 0.03) and non-relapse mortality (p= 0.04). Filamentous actin is cleared from the circulation by vitamin D binding protein so we expected that higher levels of vitamin D binding protein would improve outcomes. In a cohort of 190 children receiving allogeneic transplant, risk of thrombotic microangiopathy was reduced in those with serum concentrations of vitamin D binding protein above the median at day 30 (10% vs 31%, p=0.01), and graft versus host disease and non-relapse mortality were reduced in those with levels above the median at day 100 (3% vs 18%, p=0.04 and 0% vs 15%, p=0.002). Western blot analyses demonstrated actin-vitamin D binding protein complexes in the blood, which cleared by day 21-28. Our data support modulation of cytokine secretion and macrophage phenotype by vitamin D binding protein later after transplant. Taken together, our data identify an association between filamentous-actin, a mediator of endothelial damage, and vitamin D binding protein, an actin scavenger, as modifiers of risk of clinical consequences of endothelial injury.

Comparison of total body irradiation versus non-total body irradiation containing regimens for de novo acute myeloid leukemia in children.

With limited data comparing hematopoietic cell transplant outcomes between myeloablative total body irradiation (TBI) containing and non-TBI regimens in children with de novo acute myeloid leukemia, the aim of this study was to compare transplant-outcomes between these regimens. Cox regression models were used to compare transplant-outcomes after TBI and non-TBI regimens in 624 children transplanted between 2008 and 2016. Thirty two percent (n=199) received TBI regimens whereas 68% (n=425) received non-TBI regimens. Five-year non-relapse mortality was higher with TBI regimens (22% vs. 11%, p<0.0001) but relapse was lower (23% vs. 37%, p<0.0001) compared to non-TBI regimens. Consequently, overall (62% vs. 60%, p=1.00) and leukemia-free survival (55% vs. 52%, p=0.42) did not differ between treatment groups. Grade II-IV acute GVHD was higher with TBI regimens (56% vs. 27%, p<0.0001) but not chronic GVHD. The 3-year incidence of gonadal or growth hormone deficiency was higher with TBI regimens (24% vs. 8%, p<0.001) but there were no differences in late pulmonary, cardiac or renal impairment. In the absence of a survival advantage, the choice of TBI or non-TBI regimen merits careful consideration with the data favoring non-TBI regimens to limit the burden of morbidity associated with endocrine dysfunction.