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.

Infrequent fractures and resilient bone mineral density: bone health in patients with Fanconi anemia.

Not available.

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.

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.

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.

Hyperdiploid Precursor B-acute Lymphoblastic Leukemia Presenting as a Cavernous Sinus Mass in a 4-Year-old Male.

Risk stratification and appropriate treatment selection for children with precursor B-acute lymphoblastic leukemia (B-ALL) have improved outcomes. We report the case of a 4-year-old male with a lymphomatous cavernous sinus mass, a previously undescribed presentation of newly diagnosed hyperdiploid B-ALL. Few case reports in the literature describe lymphomatous involvement in this region, but none are associated with pediatric B-ALL. This case presented unique treatment and risk assignment challenges given the intracranial location of this tumor and proximity to the central nervous system.

Obinutuzumab (GA101) compared to rituximab significantly enhances cell death and antibody-dependent cytotoxicity and improves overall survival against CD20(+) rituximab-sensitive/-resistant Burkitt lymphoma (BL) and precursor B-acute lymphoblastic leukaemia (pre-B-ALL): potential targeted therapy in patients with poor risk CD20(+) BL and pre-B-ALL.

Obinutuzumab is a novel glycoengineered Type-II CD20 monoclonal antibody. CD20 is expressed in approximately 100% of children and adolescents with Burkitt lymphoma (BL) and 40% with precursor B-cell acute lymphoblastic leukaemia (pre-B-ALL). We evaluated the anti-tumour activity of obinutuzumab versus rituximab against rituximab-resistant (Raji 4RH) and -sensitive (Raji) BL and pre-B-ALL (U698-M) cells in vitro and in human BL or Pre-B-ALL xenografted mice. We demonstrated that obinutuzumab compared to rituximab significantly enhanced cell death against Raji 35·6 ± 3·1% vs. 25·1 ± 2·0%, (P = 0·001), Raji4RH 19·7 ± 2·2% vs. 7·9 ± 1·5% (P = 0·001) and U-698-M 47·3 ± 4·9% vs. 23·2 ± 0·5% (P = 0·001), respectively. Obinutuzumab versus rituximab also induced a significant increase in antibody-dependent cellular cytotoxicity (ADCC) with K562-IL15-41BBL expanded NK cells against Raji 73·8 ± 8·1% vs. 56·81 ± 4·6% (P = 0·001), Raji-4RH 40·0 ± 1·6% vs. 0·5 ± 1·1% (P = 0·001) and U-698-M 70·0 ± 1·6% vs. 45·5 ± 0·1% (P = 0·001), respectively. Overall survival in tumour xenografted mice receiving 30 mg/kg of obinutuzumab was significantly increased when compared to those receiving 30 mg/kg of rituximab in BL; Raji (P = 0·05), Raji4RH (P = 0·02) and U698-M (P = 0·03), respectively. These preclinical data suggest obinutuzumab is significantly superior to rituximab in inducing cell death, ADCC and against rituximab-sensitive/-resistant BL and pre-B-ALL xenografted mice. Taken together, these preclinical results provide evidence to suggest that future investigation of obinutuzumab is warranted in patients with relapsed/refractory CD20(+) BL and/or pre-B-ALL.

Fanconi anemia neuroinflammatory syndrome: brain lesions and neurologic injury in Fanconi anemia.

ABSTRACT: Fanconi anemia (FA) is a complex inherited bone marrow failure syndrome characterized by chromosomal instability and defective DNA repair, causing sensitivity to DNA interstrand crosslinking agents. Our understanding of the full adult phenotype of the disease continues to evolve, because most patients with FA died of marrow failure in the first decade of life before more recent advances in allogeneic hematopoietic cell transplantation. Herein, we report a previously undescribed, clinically concerning, progressive neurologic syndrome in patients with FA. Nine nonimmunosuppressed pediatric patients and young adults with FA presented with acute and chronic neurological signs and symptoms associated with distinct neuroradiological findings. Symptoms included, but were not limited to, limb weakness, papilledema, gait abnormalities, headaches, dysphagia, visual changes, and seizures. Brain imaging demonstrated a characteristic radiographic appearance of numerous cerebral and cerebellar lesions with associated calcifications and often a dominant ring-enhancing lesion. Tissue from the dominant brain lesions in 4 patients showed nonspecific atypical glial proliferation, and a small number of polyomavirus-infected microglial cells were identified by immunohistochemistry in 2 patients. Numerous interventions were pursued across this cohort, in general with no improvement. Overall, these patients demonstrated significant progressive neurologic decline. This cohort highlights the importance of recognizing FA neuroinflammatory syndrome, which is distinct from malignancy, and warrants careful ongoing evaluation by clinicians.

Uncommon BK polyomaviruses detected in allogeneic hematopoietic cell transplant recipients.

The role of viral diversity in the pathogenesis of BK polyomavirus (BKPyV)-associated disease is poorly understood. Here, we report near full-length BKPyV genome sequences from two allogeneic hematopoietic cell transplant recipients infected with BKPyV genotype II, which is uncommon in the USA.

Increased Body Mass Index Augments Endothelial Injury and Clinical Outcomes after Hematopoietic Stem Cell Transplantation.

Higher body mass index (BMI) is characterized as a chronic inflammatory state with endothelial dysfunction. Endothelial injury after allogeneic hematopoietic stem cell transplantation (allo-HSCT) puts patients at risk for such complications as transplantation-associated thrombotic microangiopathy (TA-TMA) and acute graft-versus-host-disease (aGVHD). To evaluate the impact of increased BMI on endothelial injury after allo-HSCT in pediatric and young adult patients, we conducted a retrospective cohort study evaluating 476 consecutive allo-HSCT children and young adult recipients age 0 to 20 years. Our analysis was subdivided based on distinct age categories (<2 years and 2 to 20 years). BMI was considered as a variable but was also expressed in standard deviations from the mean adjusted for age and sex (z-score), based on established criteria from the World Health Organization (age <2 years) and the Centers for Disease Control and Prevention (age 2 to 20 years) to account for differences associated with age. Primary endpoints included the incidences of TA-TMA and aGVHD. Increased BMI z-score was associated with TA-TMA after allo-HSCT in patients age <2 years (median, 18.1; IQR, 17 to 20; P = .006) and in patients age 2 to 20 years (median, 18.7; IQR, 16 to 21.9; P = .02). Higher BMI z-score correlated with TA-TMA risk in both age groups, with a BMI z-score of .9 in the younger cohort and .7 (IQR, -.4 to 1.6; P = .04) in the older cohort. Increased BMI z-score was associated with an increased risk of TA-TMA in a multivariate analysis of the entire cohort (odds ratio [OR], 1.2; 95% confidence interval [CI], 1.05 to 1.37; P = .008). Multivariate analysis also demonstrated that patients with BMI in the 85th percentile or greater had an increased risk of developing TA-TMA compared to those with a lower BMI percentile (OR, 2.66; 95% CI, 1.62 to 4.32; P < .001). Baseline and day +7 ST2 levels were elevated in subjects with TA-TMA compared to those without TA-TMA in both age groups. Baseline sC5b-9 concentration was not correlated with BMI z-score, but sC5b-9 concentration was increased markedly by 7 days post-allo-HSCT in patients age <2 years who later developed TA-TMA compared to those who never developed TA-TMA (P = .001). The median BMI z-score was higher for patients with aGVHD compared to patients without aGVHD (.7 [range, -3.9 to 3.9] versus .2 [range, -7.8 to 5.4]; P = .03). We show that high BMI is associated with augmented risk of endothelial injury after HSCT, specifically TA-TMA. These data identify a high-risk population likely to benefit from early interventions to prevent endothelial injury and prompt treatment of established endothelial injury.

Bone Health Outcomes at 1 Year after Hematopoietic Stem Cell Transplantation in a Heterogeneous Pediatric Population.

Impaired bone mineral density (BMD) is a known complication of hematopoietic stem cell transplantation (HSCT) in adults and may lead to increased fracture risk. Less is known in children about the risks for impaired BMD and fragility (low trauma) fractures after HSCT. In this study, we evaluated the incidence of fragility fractures in a large diverse pediatric HSCT recipient population and identified risk factors for both fracture and impaired BMD. We reviewed the records of 237 patients age ≤21 years at the time of transplantation who underwent HSCT at our institution between January 2015 and March 2018. The primary endpoint was the incidence of fragility fractures, and the secondary endpoint was assessment of BMD on dual-energy X-ray absorptiometry (DXA). DXA studies were available for analysis in 79 of 206 patients who were alive at 1 year after HSCT, and the median height-for-age adjusted z-score for spine BMD was 0.15. Among the 237 patients in this study, 25 (10.5%) had evidence of at least 1 fragility fracture on imaging. In the patients with at least 1 fragility fracture, 18 (72%) sustained spine fractures. The median time to fracture was 5.9 months after HSCT. Mortality at 1 year was proportionally higher, although not statistically significantly so (P = .11) in patients who had at least 1 fragility fracture (24%; 6 of 25) compared with patients without a fragility fracture (12%; 25 of 212). Vitamin D status at 1 year post-HSCT was sufficient (>20 ng/mL) in 94% of the patients assessed (160 of 171). There was no difference in the incidence of fracture between vitamin D-sufficient patients and vitamin D-insufficient patients (P = 1.0). The incidence of fracture was significantly higher in patients with graft-versus-host disease (GVHD) compared with those without GVHD (15% vs 6%; P = .02). There was no significant difference in fracture occurrence between patients who received reduced-intensity conditioning and those who received myeloablative conditioning. The cumulative glucocorticoid dose was significantly associated with fracture in patients exposed to glucocorticoids for >3 months (P = .03). The incidence of fragility fractures, especially vertebral compression fractures, after pediatric HSCT is striking. Furthermore, there may have been additional, asymptomatic patients in our cohort with undetected, occult fractures. The high incidence of fragility fractures seen in this study advocates for establishing bone health screening protocols with attention to spinal imaging in pediatric patients undergoing HSCT.