Emapalumab therapy for hemophagocytic lymphohistiocytosis prior to reduced-intensity transplantation improves chimerism.

Hemophagocytic lymphohistiocytosis (HLH) is a hyperinflammatory disorder driven by interferon-gamma (IFN-γ). Emapalumab, an anti-IFN-γ antibody, is approved for the treatment of patients with primary HLH. Hematopoietic stem cell transplantation (HSCT) is required for cure of HLH. Reduced intensity conditioning (RIC) HSCT is associated with improved survival but higher incidences of mixed chimerism and secondary graft failure. To understand the potential impact of emapalumab on post-HSCT outcomes we conducted a retrospective study of pediatric patients with HLH receiving a first RIC-HSCT at our institution between 2014 and 2022 after treatment for HLH, with or without this agent. Mixed chimerism was defined as <95% donor chimerism and severe mixed chimerism as <25% donor chimerism. Intervention free survival (IFS) included donor lymphocyte infusion, infusion of donor CD34-selected cells, second HSCT or death within 5-years post-HSCT. Fifty patients met inclusion criteria, 22 received emapalumab within 21 days prior to the conditioning regimen and 28 did not. Use of emapalumab was associated with a markedly lower incidence of mixed chimerism (48% vs. 77%, p=0.03) and severe mixed chimerism (5% vs. 38%, p<0.01). IFS was significantly higher in patients receiving emapalumab (73% vs. 43%, p=0.03). Improved IFS was even more striking in infants <12 months, a group at highest risk for mixed chimerism (75% vs. 20%, p<0.01). While overall survival was higher with emapalumab, this difference was not significant (82% vs. 71%, p=0.39). We show that the use of emapalumab for HLH pre-HSCT mitigates the risk of mixed chimerism and graft failure following RIC-HSCT.

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.

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

Not available.

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.

Reeling in complement in transplant-associated thrombotic microangiopathy: You're going to need a bigger boat.

Over the last decade there have been numerous advances in both the diagnosis and treatment of transplant-associated thrombotic microangiopathy (TA-TMA). These are largely the result of an improved understanding of complement activation in TA-TMA and the ability to prevent end organ injury and death with timely initiation of complement-blocking therapies. In this article, we review our current understanding of the pathophysiology of TA-TMA, particularly as it pertains to complement activation, endothelial injury, and clinical management. We then review novel complement-blocking therapies that are currently under investigation for use in TA-TMA, as well as discuss special considerations for complement-blocking therapy in hematopoietic stem cell transplant recipients. Through these reviews we aim to answer or at least provide an educated discussion on the most commonly posed TA-TMA management questions and dilemmas.

What complements complement in transplant-associated thrombotic microangiopathy?

Transplant-associated thrombotic microangiopathy remains a lethal complication of haematopoietic stem cell transplant and not all patients respond to terminal complement inhibitors. Qi et al. show that hypoxia-inducible factor-1α (HIF-1α) may be a previously unrecognized driver of this endothelial injury syndrome. Commentary on Qi et al. Upregulation of HIF-1α contributes to complement activation in transplantation-associated thrombotic microangiopathy. Br J Haematol. 2022 199:603-615.

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.

Diagnostic Considerations in H1N1 Influenza-induced Thrombotic Microangiopathy.

Influenza virus can trigger atypical hemolytic uremic syndrome and present with complement-driven thrombotic microangiopathy (TMA). When administered promptly, complement-blocking therapies can spare organ injury and be lifesaving. However, diagnosing TMA in the setting of a severe viral infection can be challenging, as a significant overlap of symptoms and disease complications exists. This is particularly true in influenza virus infections and more recently, Coronavirus disease 2019 (COVID-19) infections. We present a 16-year-old male with H1N1 influenza-induced atypical hemolytic uremic syndrome who quickly improved with complement-blocking therapy, highlighting an urgent need to include TMA in the differential diagnosis of severe viral infections.

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.

Testicular thrombotic microangiopathy: An unrecognized complication.

Thrombotic microangiopathy (TMA) causes global endothelial damage and multiorgan injury. No study has described reproductive organ involvement in TMA. Our study aimed to characterize testicular involvement in TMA. We reviewed autopsies from four patients who underwent hematopoietic cell transplant (HCT) complicated by TMA. Three patients had striking histologic evidence of TMA, while the fourth had normal testicular histology. This suggests that TMA injures the testicles and may adversely affect fertility. There is now an urgent need for a larger analysis of reproductive organ involvement in TMA.

Single-center results reporting improved hematopoietic stem cell mobilization success in pediatric and young adult patients with solid tumors and lymphoma.

BACKGROUND: High-dose chemotherapy with autologous hematopoietic stem cell transplantation (auto-HSCT) is an established treatment for pediatric and young adult patients with solid tumors and lymphomas. Plerixafor is a CXC chemokine receptor type 4 (CXCR4) antagonist that can be used with granulocyte colony stimulating factor (G-CSF) to amplify the mobilization of hematopoietic stem cells (HSCs). METHODS: We performed a retrospective analysis of 167 pediatric solid tumor and lymphoma patients from January 2010 to July 2020 in whom HSCs were mobilized using G-CSF alone or with plerixafor. RESULTS: Thirteen heavily pretreated patients (33.3%) required twice-daily dosing of G-CSF compared to five patients (3.9%) in the not heavily pretreated group (p = .0005). Fourteen heavily pretreated patients (35.9%) required plerixafor compared to four patients (3.1%) in the comparison cohort (p = .0002). The number of mobilization days was similar between both cohorts, with 5 days (range 3-11 days) in the heavily pretreated group and 5 days (range 3-13 days) in the not heavily pretreated group (p = .55). The number of harvest days was 2 days (range 1-5 days) in the heavily pretreated group and 1 day (range 1-4 days) in the not heavily pretreated group (p = .0025). The final cluster of differentiation (CD)34+ /kilogram (kg) count was 9.52 × 106 /kg among heavily pretreated patients compared to 34.99 × 106 /kg CD34+ cells in the comparison group (p < .0001). Three heavily pretreated patients (7.7%) failed HSC mobilization. CONCLUSIONS: Patients at the highest risk for poor HSC mobilization can be successfully treated with more frequent G-CSF dosing or G-CSF with plerixafor in a large majority of cases.

The Natural History of BK Polyomavirus and the Host Immune Response After Stem Cell Transplantation.

BACKGROUND: BK polyomavirus (BKPyV) is associated with symptomatic hemorrhagic cystitis after hematopoietic cell transplantation (HCT). Little is known about the host immune response, effectiveness of antiviral treatment, or impact of asymptomatic replication on long-term kidney function. METHODS: In children and young adults undergoing allogeneic HCT, we quantified BKPyV viruria and viremia (pre-HCT and at Months 1-4, 8, 12, and 24 post-HCT) and tested associations of peak viremia ≥10 000 or viruria ≥109 copies/mL with estimated kidney function (glomerular filtration rate, eGFR) and overall survival at 2 years posttransplant. We examined the factors associated with viral clearance by Month 4, including BKPyV-specific T cells by enzyme-linked immune absorbent spot at Month 3 and cidofovir use. RESULTS: We prospectively enrolled 193 participants (median age 10 years) and found that 18% had viremia ≥10 000 copies/mL and 45% had viruria ≥109 copies/mL in the first 3 months post-HCT. Among the 147 participants without cystitis (asymptomatic), 58 (40%) had any viremia. In the entire cohort and asymptomatic subset, having viremia ≥10 000 copies/mL was associated with a lower creatinine/cystatin C eGFR at 2 years post-HCT. Viremia ≥10 000 copies/mL was associated with a higher risk of death (adjusted hazard ratio, 2.2; 95% confidence interval, 1.1-4.2). Clearing viremia was associated with detectable BKPyV-specific T cells and having viremia <10 000 copies/mL, but not cidofovir exposure. CONCLUSIONS: Screening for BKPyV viremia after HCT identifies asymptomatic patients at risk for kidney disease and reduced survival. These data suggest potential changes to clinical practice, including prospective monitoring for BKPyV viremia to test virus-specific T cells to prevent or treat BKPyV replication.

Association between Vitamin D and Risk for Early and Late Post-Transplant Complications.

Vitamin D (VD) deficiency is a well-described phenomenon in pediatric patients undergoing hematopoietic stem cell transplant (HSCT). VD modulates inflammation, and deficiency pre-HSCT and at day +100 has been associated with graft-versus-host disease (GVHD) and poorer survival. However, a paucity of data has specifically described the association between VD status and immune-mediated complications including GVHD and veno-occlusive disease (VOD). Additionally, data to guide recommendations for VD monitoring and supplementation during HSCT are scarce. Our primary objective was to evaluate the association between VD and post-HSCT complications. The key secondary aim was to evaluate the routine use and efficacy of VD monitoring and supplementation practices. To our knowledge, this is the largest study of its kind in the pediatric population. This retrospective study evaluated VD level (VDL) before and 1 year after HSCT, VD supplementation practices, and their association with acute GVHD, VOD, and survival in pediatric patients who received autologous and allogeneic HSCT for both malignant and nonmalignant diseases from January 2013 to April 2018. Of 314 HSCTs, 43% of patients (n = 136) had VDL measured before HSCT; 61% of this cohort had pre-HSCT VD insufficiency (<30 ng/mL). Neither pre-HSCT nor follow-up VDL was associated with the incidence of GVHD or VOD. Supplementation did not result in significantly different post-HSCT VDL.VDL was correlated with overall survival; every 10-ng/mL increase in VDL was associated with a 28% decreased risk of death (P = .01). Current accepted VD supplementation regimens for pediatric HSCT do not achieve sufficient VDL in most patients after HSCT. VD status was associated with all-cause mortality but not with individual comorbidities; prospective studies are required to establish the connection between VD status, inflammatory-mediated HSCT complications, and potential benefit of VD supplementation before and after HSCT. These studies are needed to inform evidence-based guidelines for monitoring and supplementing VD during HSCT.

Improving the Timeliness of Chemotherapy Administration in the Bone Marrow Transplant Unit.

Patients undergoing hematopoietic stem cell transplantation (HSCT) are often admitted to the hospital the day they are due to begin their conditioning regimen. Timely initiation of chemotherapy during regular work hours is important for patient safety, because during the night shift fewer physicians and pharmacists are available for urgent or unexpected matters. A review of the data at our institution from October 2017 to August 2018 showed that approximately one-third of our chemotherapy was started during the night shift (after 19:00), and the average time from admission to start of chemotherapy was over 8 hours. There are currently no well-defined benchmarks for timeliness of chemotherapy initiation. The aim of this quality improvement initiative was to increase the percentage of patients who start chemotherapy in the bone marrow transplant unit before 19:00 from 65% to >80% by March 31, 2019. We identified barriers to timely initiation of chemotherapy through process mapping and analysis of failures. The primary barriers were late admissions (after 12:00 pm) and time from admission to preparation of chemotherapy. We addressed mechanisms to mitigate these barriers through Plan-Do-Study-Act testing. Interventions included providing families specific admission times and their rationales and process for notifying pharmacy of admissions immediately on arrival. We used standardized control charts to measure the impact of the interventions on change. We also monitored medication errors before and during the intervention. From September 2018 to March 2019 the percentage of patients who started preparative chemotherapy before 19:00 increased from 65% to 85%, the percentage of patients who were admitted after 12:00 remained similar before (31%) and after the interventions (33%), and the average time from admission to start of chemotherapy decreased from 8.6 hours (513 minutes) to 6.4 hours (382 minutes). Medication errors were similar before (n = 50) and after the interventions (n = 43). Using standardized processes, we demonstrated a substantial decrease in the percentage of HSCT patients starting their preparative regimen after 19:00 without a concurrent increase in errors. We believe these interventions and measurements can be used in all transplant centers and have the potential to influence patient safety and outcomes.

Acute Kidney Injury in Children after Hematopoietic Cell Transplantation Is Associated with Elevated Urine CXCL10 and CXCL9.

Acute kidney injury (AKI) is nearly universally associated with worse outcomes, especially among children after hematopoietic stem cell transplant (HCT). Our objective was to examine urinary immune biomarkers of AKI after HCT to provide insights into novel mechanisms of kidney injury in this population. Studying patients undergoing allogeneic HCT provides a unique opportunity to examine immune markers of AKI because the risk of AKI is high and the immune system newly develops after transplant. Children (>2 years old) and young adults undergoing their first allogeneic HCT and enrolled in a prospective, observational cohort study at 2 large children's hospitals had urine collected pre-HCT and monthly for the first 4 months after HCT. Urine samples at each monthly time point were assayed for 8 immune-related biomarkers. AKI was defined as a 1.5-fold increase in the monthly serum creatinine value, which was recorded ±1 day from when the research urine sample was obtained, as compared with the pre-HCT baseline. Generalized estimating equation regression analysis evaluated the association between the monthly repeated measures (urinary biomarkers and AKI). A total of 176 patients were included from 2 pediatric centers. Thirty-six patients from 1 center were analyzed as a discovery cohort and the remaining 140 patients from the second center were analyzed as a validation cohort. AKI rates were 18% to 35% depending on the monthly time point after HCT. Urine CXCL10 and CXCL9 concentrations were significantly higher among children who developed AKI compared with children who did not (P < .01) in both cohorts. In order to gain a better understanding of the cellular source for these biomarkers in the urine, we also analyzed in vitro expression of CXCL10 and CXCL9 in kidney cell lines after stimulation with interferon-γ and interferon-α. HEK293-epithelial kidney cells demonstrated interferon-induced expression of CXCL10 and CXCL9, suggesting a potential mechanism driving the key finding. CXCL10 and CXCL9 are associated with AKI after HCT and are therefore promising biomarkers to guide improved diagnostic and treatment strategies for AKI in this high-risk population.

Thinking Beyond HLH: Clinical Features of Patients with Concurrent Presentation of Hemophagocytic Lymphohistiocytosis and Thrombotic Microangiopathy.

Hemophagocytic lymphohistiocytosis (HLH) is a syndrome of excessive immune system activation driven mainly by high levels of interferon gamma. The clinical presentation of HLH can have considerable overlap with other inflammatory conditions. We present a cohort of patients with therapy refractory HLH referred to our center who were found to have a simultaneous presentation of complement-mediated thrombotic microangiopathy (TMA). Twenty-three patients had therapy refractory HLH (13 primary, 4 EVB-HLH, 6 HLH without known trigger). Sixteen (69.6%) met high-risk TMA criteria. Renal failure requiring renal replacement therapy, severe hypertension, serositis, and gastrointestinal bleeding were documented only in patients with HLH who had concomitant complement-mediated TMA. Patients with HLH and without TMA required ventilator support mainly due to CNS symptoms, while those with HLH and TMA had respiratory failure predominantly associated with pulmonary hypertension, a known presentation of pulmonary TMA. Ten patients received eculizumab for complement-mediated TMA management while being treated for HLH. All patients who received the complement blocker eculizumab in addition to the interferon gamma blocker emapalumab had complete resolution of their TMA and survived. Our observations suggest co-activation of both interferon and complement pathways as a potential culprit in the evolution of thrombotic microangiopathy in patients with inflammatory disorders like refractory HLH and may offer novel therapeutic approaches for these critically ill patients. TMA should be considered in children with HLH and multi-organ failure, as an early institution of a brief course of complement blocking therapy in addition to HLH-targeted therapy may improve clinical outcomes in these patients.

Circulating dsDNA, endothelial injury, and complement activation in thrombotic microangiopathy and GVHD.

Transplant-associated thrombotic microangiopathy (TA-TMA) is a common and poorly recognized complication of hematopoietic stem cell transplantation (HSCT) associated with excessive complement activation, likely triggered by endothelial injury. An important missing piece is the link between endothelial injury and complement activation. We hypothesized that neutrophil extracellular traps (NETs) mechanistically link endothelial damage with complement activation and subsequent TA-TMA. Neutrophil activation releases granule proteins together with double-stranded DNA (dsDNA) to form extracellular fibers known as NETs. NETs have been shown to activate complement and can be assessed in humans by quantification of dsDNA in serum. We measured levels of dsDNA, as a surrogate for NETs in 103 consecutive pediatric allogeneic transplant recipients at day 0, +14, +30, +60, and +100. A spike in dsDNA production around day +14 during engraftment was associated with subsequent TA-TMA development. Peak dsDNA production around day +14 was associated with interleukin-8-driven neutrophil recovery. Increased dsDNA levels at days +30, +60, and +100 were also associated with increased mortality and gastrointestinal graft-versus-host disease (GVHD). NETs may serve as a mechanistic link between endothelial injury and complement activation. NET formation may be one mechanism contributing to the clinical overlap between GVHD and TA-TMA.

Lower levels of vitamin A are associated with increased gastrointestinal graft-versus-host disease in children.

Vitamin A promotes development of mucosal tolerance and enhances differentiation of regulatory T cells. Vitamin A deficiency impairs epithelial integrity, increasing intestinal permeability. We hypothesized that higher vitamin A levels would reduce the risk of graft-versus-host disease (GVHD) through reduced gastrointestinal (GI) permeability, reduced mucosal injury, and reduced lymphocyte homing to the gut. We tested this hypothesis in a cohort study of 114 consecutive patients undergoing allogeneic stem cell transplant. Free vitamin A levels were measured in plasma at day 30 posttransplant. GI GVHD was increased in patients with vitamin A levels below the median (38% vs 12.4% at 100 days, P = .0008), as was treatment-related mortality (17.7% vs 7.4% at 1 year, P = .03). Bloodstream infections were increased in patients with vitamin A levels below the median (24% vs 8% at 1 year, P = .03), supporting our hypothesis of increased intestinal permeability. The GI mucosal intestinal fatty acid-binding protein was decreased after transplant, confirming mucosal injury, but was not correlated with vitamin A levels, indicating that vitamin A did not protect against mucosal injury. Expression of the gut homing receptor CCR9 on T-effector memory cells 30 days after transplant was increased in children with vitamin A levels below the median (r = -0.34, P = .03). Taken together, these data support our hypothesis that low levels of vitamin A actively promote GI GVHD and are not simply a marker of poor nutritional status or a sicker patient. Vitamin A supplementation might improve transplant outcomes.

Haptoglobin degradation product as a novel serum biomarker for hematopoietic stem cell transplant-associated thrombotic microangiopathy.

BACKGROUND: Hematopoietic stem cell transplant (HSCT)-associated thrombotic microangiopathy (TA-TMA) is a well-known complication of HSCT and carries high risk of morbidity and mortality. A lack of consistent non-invasive diagnostic criteria can delay diagnosis and lead to irreversible organ damage. METHODS: Serum samples of 100 patients that underwent HSCT at Cincinnati Children's Hospital were serially collected. Unbiased proteomic profiling by SELDI-TOF-MS was performed on serum from TA-TMA patients at baseline (pre-HSCT), 2 weeks before TMA diagnosis (pre-TMA), and at clinical TMA diagnosis. Two proteins with mass to charge ratios of 12-13 kDa were consistently elevated at the 2 week pre-TMA time point by SELDI-TOF, compared to control samples. Potential peptides were isolated and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) on the Linear Trap Quadropole (LTQ). A MASCOT search identified haptoglobin fragments in the 12-17-kDa range. Western blot was performed to validate haptoglobin fragments as a potential biomarker. RESULTS: Western blot of TA-TMA patients showed haptoglobin fragments at 12, 14, and 17 kDa that varied between baseline, pre-TMA, and TMA time points for each patient. By densitometric analysis, the 17-kDa fragment in the pre-TMA samples differed significantly from TMA diagnosis (p < 0.0001). There was no significant difference in the concentrations of the 12-kDa and 14-kDa fragments. CONCLUSION: The 17-kDa haptoglobin degradation product may represent a novel early serum biomarker for TA-TMA that could potentially allow for earlier diagnosis and intervention.

Combination of High-Dose Methylprednisolone and Defibrotide for Veno-Occlusive Disease in Pediatric Hematopoietic Stem Cell Transplant Recipients.

Veno-occlusive disease (VOD) is a serious complication of hematopoietic stem cell transplant (HSCT), with high mortality in severe cases and until recently very limited therapeutic options consisting largely of supportive care. Defibrotide was recently approved in the United States for the treatment of severe VOD in patients with renal or pulmonary dysfunction after HSCT. Our group previously published on the use of high-dose methylprednisolone (500 mg/m2 per dose every 12 hours for 6 doses) in patients with VOD, showing good success. A small subset of these individuals were also treated with defibrotide, but additional studies using the combination of high-dose methylprednisolone and defibrotide for the treatment of VOD are lacking. We present a single-institution retrospective chart review of 15 HSCT patients with VOD treated with the combination of high-dose methylprednisolone and defibrotide. VOD developed at a median of 17 days post-HSCT, and combination therapy was initiated within 1 day of VOD diagnosis. Twelve of 15 patients (80%) had multiorgan failure. Our single-center experience using both high-dose methylprednisolone and defibrotide showed a day +100 survival rate of 73% and an overall VOD complete resolution rate of 66.7%, higher than the rates reported in the recent literature using defibrotide alone (40% to 50% day +100 overall survival). These data suggest that the combination of high-dose steroids and defibrotide may be superior to defibrotide alone and warrant further investigation.