Successful Hematopoietic Stem Cell Transplantation Research Articles

Successful Haematopoietic Stem Cell Transplantation for LRBA Deficiency with Fludarabine, Treosulfan, and Thiotepa-Based Conditioning

LRBA deficiency is an inborn error of immunity defined by autoimmunity, lymphoproliferation, recurrent infections, cytopenia, and inflammatory bowel disease. Despite recent advances in managing this disease with targeted biologic therapy, haematopoietic stem cell transplant (HSCT) remains the only cure. However, great variability exists between protocols used to transplant patients with LRBA deficiency. We describe a cohort of seven patients with LRBA deficiency who underwent HSCT using a myeloablative, reduced toxicity regime of fludarabine, treosulfan, and thiotepa at two transplantation centres from 2016 to 2019. Data were collected both retrospectively and prospectively, measuring time to engraftment, infectious complications, incidence of graft versus host disease, and post-transplantation chimerism. Six of seven patients survived transplantation, and four of six surviving patients achieving treatment-free survival. We thus recommend that HSCT with fludarabine, treosulfan, and thiotepa-based conditioning be considered in patients with LRBA deficiency.

COMPARATIVE ANALYSIS OF TREC AND KREC ASSAYS FOR DIAGNOSIS OF PID IN DIFFERENT COUNTRIES

Nationwide neonatal screening programs of lymphocyte production using T-cell recombination excision circles (TREC) and kappa-deleting element recombination circle (KREC) have been important tools for the timely diagnosis of primary immunodeficiency (PID). Diagnosis and treatment of congenital defects of the immune system have made significant strides in many countries. However, a significant part of the children with severe immunodeficiency in the first year of life are diagnosed posthumously. Immunodeficiencies are under diagnosed primarily due to the lack of opportunities for early diagnosis and low awareness of these pathologies in doctors and the other healthcare professionals. Therefore, the issue and importance of early SCID detection using newborn screening assays become an essential public health problem. Newborn screening, particularly through TREC and KREC assays, has emerged as a promising avenue for identifying PID in its nascent stages. Early diagnosis not only facilitates prompt and targeted intervention, but also offers the opportunity to provide improved long-term outcomes for individuals facing these complex disorders. Screening for severe combined immunodeficiency (SCID) was introduced in the Swedish newborn screening program in August 2019, and according to the results from the first year, TREC, KREC and actin beta (ACTB) levels were measured by multiplex qPCR in dried blood spots (DBS) that obtained from 115,786 newborns and children under two years of age. On the basis of low TREC levels, 73 children were requested to undergo further clinical evaluation, resulting in the diagnosis of T-cell lymphopenia in 21 children. The DEPISTREC pilot study in France compared 190,517 infants screened for TREC with a control group of 1,400,000 children. TREC screening identified three patients with SCID, compared to 28 in the control group. Unfortunately, five children in the control group died of SCID before waiting for HSCT, which could potentially have been prevented by TREC screening. An economic analysis showed that the main cost factors were morbidity and cost per test and demonstrated that routine SCID screening was feasible and effective. In addition, two US states, Wisconsin and Massachusetts, have conducted pilot projects funded by the Center for Disease Control to evaluate the feasibility and effectiveness of newborn screening (NBS) for severe combined immunodeficiency (SCID) using the TREC assay. In Wisconsin, 71,000 infants were screened in 2008, identifying eight infants with T-lymphocytopenia, including one successfully treated with cord blood hematopoietic stem cell transplantation (HSCT). In Massachusetts, 100,597 infants were screened in 2009-2010 where twenty-nine infants with T-lymphocytopenia were identified, one of whom had SCID due to a compound heterozygous mutation in JAK3 and also received successful HSCT from an unrelated donor. After successfully identifying T lymphocytopenia in these experiments, the Advisory Committee on Hereditary Diseases of Newborns and Children of the Health and Human Services recommended that SCID be included in a uniform newborn screening panel. Therefore, newborn screening based on TREC and KREC assay programs is expected to provide early detection, prevent infections and prompt treatment, eventually improving overall survival. The ability to detect and intervene in the early stages of immunodeficiency diseases not only improves the prognosis for affected individuals but also enhances our understanding of the prevalence and spectrum of PID in the newborn population.

Differences in Acute Graft-Versus-Host Disease (GVHD) Severity and Its Outcomes Between Black and White Patients

Acute graft-versus-host disease (GVHD) is a significant complication following hematopoietic stem cell transplantation (HCT). Although recent advancements in GVHD prophylaxis have resulted in successful HCT across HLA barriers and expanded access to HCT for racial minorities, less is known about how race affects the severity and outcomes of acute GVHD. This study examines differences in the clinical course of acute GVHD and the prognostic value of GVHD biomarkers for Black and White recipients. We conducted a retrospective analysis of patients in the Mount Sinai Acute GVHD International Consortium (MAGIC) database who underwent HCT between 2014 and 2021 to describe the difference in clinical course of acute GVHD and significance of GVHD biomarkers between Black and White recipients. We used propensity score matching to generate a 1:3 matched cohort of 234 Black patients and 702 White patients with similar baseline characteristics. In the first year after HCT Black patients experienced a higher cumulative incidence of grade III-IV acute GVHD (17% versus 12%, P = 0.050), higher nonrelapse mortality (NRM; 18% versus 12%, P = .009), and lower overall survival that trended toward statistical significance (73% versus 79%, P = .071) compared to White patients. The difference in NRM in the first year was even greater among Black patients who developed GVHD than White patients (24% versus 14%, P = .041). The distribution of low, intermediate, and high MAGIC biomarker scores at the time of treatment was similar across racial groups (P = .847), however, Black patients with high biomarker scores experienced significantly worse NRM than White patients (71% versus 32%, P = .010). Our data indicate that Black patients are at a higher risk of NRM following HCT, primarily from a higher incidence of severe GVHD. Serum biomarkers at treatment initiation can stratify patients for risk of NRM across races, however Black patients with high biomarker scores had a significantly greater NRM risk. These results suggest a need for strategies that mitigate the higher risk for poor GVHD outcomes among Black patients.

Deciphering bone marrow engraftment after allogeneic stem cell transplantation in humans using single-cell analyses.

BACKGROUNDDonor cell engraftment is a prerequisite of successful allogeneic hematopoietic stem cell transplantation. Based on peripheral blood analyses, it is characterized by early myeloid recovery and T and B cell lymphopenia. However, cellular networks associated with bone marrow engraftment of allogeneic human cells have been poorly described.METHODSMass cytometry and CITE-Seq analyses were performed on bone marrow cells 3 months after transplantation in patients with acute myelogenous leukemia.RESULTSMass cytometric analyses in 26 patients and 20 healthy controls disclosed profound alterations in myeloid and B cell progenitors, with a shift toward terminal myeloid differentiation and decreased B cell progenitors. Unsupervised analysis separated recipients into 2 groups, one of them being driven by previous graft-versus-host disease (R2 patients). We then used single-cell CITE-Seq to decipher engraftment, which resolved 36 clusters, encompassing all bone marrow cellular components. Hematopoiesis in transplant recipients was sustained by committed myeloid and erythroid progenitors in a setting of monocyte-, NK cell-, and T cell-mediated inflammation. Gene expression revealed major pathways in transplant recipients, namely, TNF-α signaling via NF-κB and the IFN-γ response. The hallmark of allograft rejection was consistently found in clusters from transplant recipients, especially in R2 recipients.CONCLUSIONBone marrow cell engraftment of allogeneic donor cells is characterized by a state of emergency hematopoiesis in the setting of an allogeneic response driving inflammation.FUNDINGThis study was supported by the French National Cancer Institute (Institut National du Cancer; PLBIO19-239) and by an unrestricted research grant by Alexion Pharmaceuticals.

Silencing endomucin in bone marrow sinusoids improves hematopoietic stem and progenitor cell homing during transplantation.

Efficient homing of infused hematopoietic stem and progenitor cells (HSPCs) into the bone marrow (BM) is the prerequisite for successful hematopoietic stem cell transplantation. However, only a small part of infused HSPCs find their way to the BM niche. A better understanding of the mechanisms that facilitate HSPC homing will help to develop strategies to improve the initial HSPC engraftment and subsequent hematopoietic regeneration. Here, we show that irradiation upregulates the endomucin expression of endothelial cells in vivo and in vitro. Furthermore, depletion of endomucin in irradiated endothelial cells with short-interfering RNA (siRNA) increases the HSPC-endothelial cell adhesion in vitro. To abrogate the endomucin of BM sinusoidal endothelial cells (BM-SECs) in vivo, we develop a siRNA-loaded bovine serum albumin nanoparticle for targeted delivery. Nanoparticle-mediated siRNA delivery successfully silences endomucin expression in BM-SECs and improves HSPC homing during transplantation. These results reveal that endomucin plays a critical role in HSPC homing during transplantation and that gene-based manipulation of BM-SEC endomucin in vivo can be exploited to improve the efficacy of HSPC transplantation.

Stem cell therapy: Advances and future directions in regenerative medicine: A review

Stem cell treatment, an important part of regenerative medicine that may change the way many illnesses and injuries are treated in the future. This review article gives an in-depth analysis of the many kinds of stem cells, including adult, induced pluripotent, and embryonic stem cells, as well as their background, properties, and potential for differentiation. Successful hematopoietic stem cell transplantation, tissue engineering, medications for neurological illnesses, and management of autoimmune diseases are only a few of the current applications of stem cells in therapy that we explore. The report also discusses cutting-edge techniques in stem cell research, such as 3D bioprinting, the game-changing CRISPR-Cas9 gene-editing approach, and the manipulation of stem cells using tiny chemicals. However, there are several obstacles on the road to stem cell treatment. We explain how ethical concerns, immunological rejection, and tumorigenicity have influenced public opinion. Future developments in stem cell therapy will be discussed, including the role of stem cell banking, tissue engineering, personalized medicine, and artificial intelligence. In conclusion, despite substantial progress, barriers still need to be eliminated before stem cell treatment can realize its promise to fundamentally alter regenerative medicine.

WITHDRAWN: Host SPHK1 deficiency ameliorates acute graft-versus-host disease by attenuating ER stress-induced gastrointestinal injury

Graft-versus-host disease (GVHD) remains a major obstacle in successful allogeneic hematopoietic stem cell transplantation (allo-HSCT). Here, we report that inhibiting sphingosine kinase 1 (SPHK1), an enzyme that phosphorylates sphingosine to bioactive sphingosine-1-phosphate (S1P), effectively ameliorates acute GVHD (aGVHD). The absence of SPHK1 in the host exerts a beneficial effect on maintaining gut homeostasis by limiting intestinal epithelial cell (IEC) injury, thus reducing gut permeability and preventing bacterial translocation, which in turn decreases the activation of antigen-presenting cells and T cell infiltration. Persistent ER stress is observed during GVHD in the gastrointestinal tract and contributes to IEC injury. SPHK1 deficiency attenuates IEC damage by alleviating ER stress, a process that can be reversed by supplementation with exogenous S1P. FTY720, an S1P receptor antagonist, significantly inhibits ER stress-induced IEC injury. Additionally, host SPHK1 deficiency helps in shaping the gut microbiota by diminishing the presence of MHC II inducer-associated bacteria, such as Lactobacillus murinus, and increasing the abundance of the IFN-γ suppressor Akkermansia muciniphila. This leads to decreased MHC II expression in IECs, contributing to an overall reduction in aGVHD severity. Together, our data reveal a pathogenic role of host SPHK1 in gastrointestinal injury during aGVHD.

Treatment Patterns and Clinical Outcomes of Patients with Moderate to Severe Acute Graft-Versus-Host Disease: A Multicenter Chart Review Study.

Acute graft-versus-host disease (aGVHD) remains a barrier to successful allogeneic hematopoietic stem cell transplantation (HSCT) outcomes. Contemporary comprehensive analyses of real-world clinical outcomes among patients who develop aGVHD post-HSCT are needed to better understand the unmet needs of this patient population. This multicenter, retrospective chart review describes treatment patterns and clinical outcomes among patients (≥18 years old) from Finland, Sweden, and France who developed grades II-IV aGVHD after their first HSCT (January 2016-June 2017). From 13 participating centers, 151 patients were included. The median (Q1, Q3) age at HSCT was 56 (45, 62) years old. One line of aGVHD treatment was received by 47.7%, and the most common first-line treatment was methylprednisolone (alone or in a combination regimen, 74.2%; monotherapy, 25.8%). Among patients treated with methylprednisolone, 79.5% achieved a complete or partial response. The median (Q1, Q3) number of treatment lines was 2.0 (1.0, 3.0). The median (Q1, Q3) time to obtain an aGVHD diagnosis from transplant was 29.5 (21.0, 44.0) days, and 14.5 (7.0, 34.0) days to achieve the best response for 110 evaluable patients. At 6 and 12 months, 53.6% and 49.0%, respectively, achieved a complete response. Chronic GVHD occurred in 37.7% of patients, and aGVHD reoccurred in 26.5%. Following aGVHD diagnosis, mortality rates were 30.0% at 6 months and 37.3% at 12 months. Findings from this study demonstrate a continuing unmet need for new therapies that control aGVHD and improve mortality.

FLAG with Bortezomib Salvage Therapy in Relapsed/Refractory Childhood Leukemia—A Reliable Bridge to Transplantation with Limited Toxicity

Relapsed refractory leukemia represents a difficult-to-treat population of patients. The balance between perceived benefit and potential side effects along with the significant financial burden of managing multidrug-resistant sepsis are factors that determine the choice of salvage regimen. Here, we present our experience with the combination of fludarabine, cytarabine, granulocyte-colony stimulating factor with bortezomib. The morphological complete response rate was 58% with 50% of the patients achieving complete remission. With only three patients requiring intensive care unit admission during remission induction, 66.6% of the patients went on to undergo successful hematopoietic stem cell transplantation. Thus, it proved to be a possible, safer alternative to other salvage regimens, while enabling a significant percentage of patients to achieve remission and proceed to allogenic stem cell transplantation.

Stem Cells Collection and Mobilization in Adult Autologous/Allogeneic Transplantation: Critical Points and Future Challenges.

Achieving successful hematopoietic stem cell transplantation (HSCT) relies on two fundamental pillars: effective mobilization and efficient collection through apheresis to attain the optimal graft dose. These cornerstones pave the way for enhanced patient outcomes. The primary challenges encountered by the clinical unit and collection facility within a transplant program encompass augmenting mobilization efficiency to optimize the harvest of target cell populations, implementing robust monitoring and predictive strategies for mobilization, streamlining the apheresis procedure to minimize collection duration while ensuring adequate yield, prioritizing patient comfort by reducing the overall collection time, guaranteeing the quality and purity of stem cell products to optimize graft function and transplant success, and facilitating seamless coordination between diverse entities involved in the HSCT process. In this review, we aim to address key questions and provide insights into the critical aspects of mobilizing and collecting hematopoietic stem cells for transplantation purposes.

Successful Hematopoietic Stem Cell Transplantation in a Child with Thalassemia major and Moderate Haemophilia A.

Successful Hematopoietic Stem Cell Transplantation in a Child with Thalassemia major and Moderate Haemophilia A.

Persistent hypersplenism following successful hematopoietic stem cell transplantation: unraveling the cellular components of extramedullary residual disease and donor hematopoiesis—a case report

In this study, we report an unprecedented case of graft failure following hematopoietic stem cell transplantation (HSCT) in a patient with a myeloproliferative neoplasm (MPN) who had achieved bone marrow (BM) remission. We outline the intricate cellular components of splenic hematopoiesis, which are derived from both the recipient and the donor, underpinning the persistence of fibrosis. Our investigation characterizes the distinct cellular populations that play a pivotal role in graft exhaustion and introduces an unusual hypothesis regarding the perpetuation of a malignant niche in extramedullary sites within the context of HSCT.

Reduced human leukocyte antigen mismatching is associated with more favourable outcomes after unrelated donor haematopoietic stem cell transplantation.

The patient-donor human leukocyte antigen (HLA) match remains the most important prognostic factor for successful unrelated donor haematopoietic stem cell transplantation (UD-HSCT). This single-centre study comprised 125 adult patients with malignant haematological diseases undergoing their first UD-HSCT. The primary goal of this study was to validate the impact of HLA matching on HSCT outcomes, specifically at the HLA-DPB1 and HLA-DRB3/4/5 loci. A multivariable Cox regression analysis with a backward selection algorithm was employed to assess the associations of selected prognostic factors with outcomes after UD-HSCT. Any HLA locus mismatch was found to be associated with an increased incidence of grade II-IV acute graft versus host disease (aGvHD) at 100 days (p=.031; hazard ratio [HR] 1.935) and 6 months (p=.004; HR 2.284) after HSCT. The results of the following analyses also confirmed the strong impact of HLA-DPB1-only mismatch on the incidence of grade II-IV aGvHD at 100-day (p=.006; HR 2.642) as well as at 6-month (p=.007; HR 2.401) time periods. The HLA-DPB1-only mismatch was also shown to be statistically significantly associated with lower relapse incidence (p=.034; HR 0.333). The impact of the HLA-DRB3/4/5 mismatch on outcomes was inconclusive, though the two and more HLA-DPB1+DRB3/4/5-only mismatches showed a trend towards worse outcomes than a single mismatch. Based on our findings and those of more comprehensive studies, the extended HLA loci typing of patients and donors is suggested to avoid unexpected HLA mismatches during the UD selection.

Neurodevelopmental outcomes in two cases of artemis deficiency

Background: Severe Combined Immunodeficiency (SCID) is a category of inborn errors of immunity where there is impaired T and B cell development and/or function. Artemis SCID (Art-SCID) is characterized by dysfunctional Artemis protein, which is crucial for V(D)J recombination in T and B cell maturation. Art-SCID is fatal without management, and current definitive treatment involves hematopoietic stem cell transplantation (HSCT) or gene therapy. As the prognosis and survival of SCID patients improves, current research has begun unveiling long-term complications and morbidities. Previous literature has reported neurodevelopmental abnormalities in SCID patients, such as developmental delay and Autism Spectrum Disorder (ASD). However, it remains unknown whether these neurodevelopmental differences are linked to the SCID mutation, an adverse outcome of treatment and hospitalization, or comorbid social isolation and psychosocial challenges. Aims: In this case series, we discuss two cases of Art-SCID which presented with neurodevelopmental deficits following successful HSCT. Results: In both cases, SCID was detected on Newborn Screening (NBS), and Art-SCID was confirmed with genetic testing. Both patients were successfully treated with HSCT at 80 days of life, and followed up clinically well, with robust cell counts. Both patients later presented in toddlerhood with developmental, speech and language delay, however only one patient met diagnostic criteria for ASD. Conclusion: The definitive relationship between SCID, HSCT, and neurodevelopmental outcomes remain unclear, and warrants further study to allow for early intervention. We are currently working with colleagues across the country to further investigate and define this complex relationship. Statement of Novelty: We are investigating the complex relationship between SCID, HSCT, and potential neurodevelopmental outcomes. We present two cases of patients with Artemis SCID who were successfully treated with HSCT, and later presented in toddlerhood with developmental, speech, and language delay.

Treatment of Molecular Relapses in Pediatric AML Saves Toxicities Prior to Hematopoietic Stem Cell Transplantation (HSCT) - Results of AMoRe2017 Trial

Introduction The long-term survival for children with AML has increased to 70 % - but relapsed AML patients still have a poor prognosis (about 30 %). Recent data suggest that in AML residual leukemic cells below the 5 % limit required for a morphologic CR can adversely affect outcome and that increasing levels of Minimal Residual Disease (MRD) are almost always followed by clinical relapse. Early MRD detection provides an opportunity to implement pre-emptive therapies as a bridge-to-transplant approach, to potentially prevent hematological relapse and increase the probability of successful HSCT. A promising approach is the use of Azacitidine (Aza) for treatment of molecular relapse which we evaluated within the clinical trial “AMoRe2017”. Aza has been shown to reverse epigenetic changes in malignant cells, restoring the normal function of genes critical for differentiation and cell cycle control. The trials' primary objective was the evaluation of the effect of Aza treatment in AML subjects at molecular relapse after CR1 regarding molecular response prior to further treatment (reinduction/HSCT). Patients and Methods AMoRe2017 enrolled children with AML (N=20), >3 months < 21 yrs., of which n=1 dropped out due to laboratory measurement error. The median age was 10.9 yrs. (range 1.7-18.9 yrs.). N=10 (53 %) had a CBFB-AML, n=5 (27 %) KMT2A-rearrangement, n=1 (5 %) NUP98::NSD1, n=1 (5 %) FLT3-ITD, n=1(5 %) PICALM::MLLT10 and n=1 (5 %) NPM1. N=8 (42 %) were classified to subgroup M2, n=4 (21 %) to M5, n=3 (16 %) into M1 and n=4 (21 %) to M4/M4 Eo. At baseline, the white blood cell count averaged 3.8x10 9/l (range 0.1-6.6x10 9/l), without leukemic blasts in PB or BM. Each patient had at least one quantifiable genetic marker (rt-PCR), achieved CR with molecular remission, following initial therapy, and subsequently had a molecular relapse (defined as an increase of the MRD level by at least 1 log, less than 5 % BM myeloblasts and absence of proven extramedullary disease). Patients were treated for up to 6 cycles with 75 mg/m 2 i.v. Aza on days 1 to 7 in a 28-day cycle. Molecular response was categorized as molecular stabilization (< 1 log decrease or increase from baseline), molecular progression (≥ 1 log increase from baseline without hematological relapse), molecular improvement (≥ 1 log decrease from baseline), and hematological relapse (at least 5 % blasts in PB and/or BM and/or proven histological extramedullary relapse). Results During Aza treatment, 10 patients (53 %) had an open relapse, which occurred in n=9 after 1 st or 2 nd cycle. These patients were monitored for KMT2A::SEPTIN6 (n=1), KMT2A::MLLT3 (n=2), PICALM::MLLT10 (n=1), FLT3-ITD (n=1), NUP98::NSD1 (n=1), CBFB::MYH11 (n=1) and RUNX1::RUNX1T1 (n=3). 9 patients (47 %; RUNX1::RUNX1T1 n=5, CBFB::MYH11 n=1, NPM1 n=1, KMT2A::ELL n=2) showed a molecular response to Aza and proceeded to HSCT without receiving intensive re-induction treatment. 16 out of the 19 patients are alive (overall survival 84 %), 2 died from HSCT-associated side effects (VOD, infection), and 1 from disease progression. Considering genetics, 7 out of 11 patients with favorable genetics (core-binding leukemia n=10 or NPM1 n=1) responded to the Aza therapy ( RUNX1::RUNX1T1 n=5, CBFB::MYH11 n=1, NPM1 n=1). By contrast, in cases with KMT2A-rearrangements, NUP98::NSD1 or FLT3-ITD, 2 out of 8 patients showed improvement or stabilization. In total 152 adverse events (AEs) associated to Aza were reported, the majority classified as grade 1 or 2 (n= 114; 75 %). Mainly affected was the hematopoietic system (40 %), the gastrointestinal tract (15 %), kidney and liver (14 %). Cardiotoxicity was not reported. Discussion The use of Aza as pre-emptive “bridge-to-transplant” approach treating the molecular relapse showed efficacy in patients with RUNX1::RUNX1T1, CBFB::MYH11, NPM1, and KMT2A::ELL, who could be transplanted directly. This pilot provided proof of principle that molecular relapses could be treated, and MRD levels be reversed, at least in subgroups. In addition, avoiding intensive re-induction therapy prior to HSCT is feasible. Conversely, the relatively slow-acting mechanism of epigenetic therapy seems to be ineffective in highly proliferative subgroups of AML with KMT2A-rearrangements or FLT3-ITD. Further studies are mandatory to define treatment options for molecular relapses of non-favorable pediatric AML and to confirm potential improvement of outcome post-HSCT.

The Effect of Allogeneic Hematopoietic Stem Cell Transplantation on Sickle Cell Disease-Related Organ Damage: A Systematic Review and Meta-Analysis

Background Allogeneic hematopoietic stem cell transplantation (HSCT) is the only established curative treatment option for patients with sickle cell disease (SCD). One of the main indications for HSCT is SCD-related organ damage, which is a major cause of morbidity and early mortality. However, whether HSCT is effective in recovering SCD-related organ dysfunction has not been systematically reviewed. Methods This is a systematic review and meta-analysis investigating the effects of HSCT on organ function in patients with SCD. We performed a comprehensive search in MEDLINE/PubMed and EMBASE up to June 2023, focusing on studies reporting pulmonary, cardiac, renal, splenic, and/or cerebral function parameters, as well as retinopathy and/or avascular osteonecrosis (AVN) before and after HSCT. Continuous data were analyzed using the weighted inverse-variance random effects meta-analyses, reported as standardized mean difference (SMD) and 95% confidence intervals (95%-CI). Binomial data were analyzed using the Mantel-Haenszel random effects meta-analyses, reported as risk ratio (RR) and 95%-CI. A negative SMD indicates an improvement and a positive SMD indicates a worsening of the measured parameter post-HSCT. A RR <1 indicates a result in favor of the transplantation and a RR >1 indicates a worsening of the measured parameter after HSCT. The ‘Newcastle-Ottawa Quality Assessment Scale’ and the ‘Clinical Diversity in Meta-analysis’ (CDIM) tool were used to assess the quality and the clinical heterogeneity of the studies. Results Thirty-two of 476 studies met our inclusion criteria, of which 17 were used for the meta-analyses and 15 for the qualitative part of the review. Of the studies that were included in the meta-analyses, 4 comprised adult patients (n=184) and 13 pediatric and/or young adults <22 years old (n=591). The majority of donors were matched sibling donors (86.4%), and studies with both myeloablative and/or reduced intensity conditioning regimens were included. The CDIM score was low or moderate for all performed meta-analyses, suggesting fair clinical comparability among the studies. Summary plots of the meta-analyses are shown in Figure 1. Pulmonary function test parameters remained stable following HSCT (SMD -0.08, p=0.64 for forced expiratory volume in 1 second; SMD -0.13, p=0.35 for forced vital capacity; and SMD -0.95, p=0.30 for diffusing capacity). Mean tricuspid regurgitation velocity (TRV) did not change significantly in the meta-analysis (SMD -0.34, p=0.14). However, 3 studies used for the qualitative review reported normalization in patients with prior elevated TRV. Whole brain cerebral blood flow improved significantly after transplantation (SMD -1.39, p=<0.01). Several studies reported an absent or very low incidence of new (silent) cerebral infarcts and a decrease of transcranial Doppler velocities following successful HSCT. In pediatric patients, creatinine clearance decreased significantly after HSCT (SMD -0.80, p=0.01) and the presence of proteinuria increased (RR 2.00, p=<0.01). Furthermore, splenic uptake ( 99mTc) and phagocytic function of the spleen improved (RR 0.31, p=<0.01 and RR 0.23, p=<0.01, respectively). Retinopathy and AVN before and after HSCT were investigated in only 1 study in children with SCD, both showing no significant changes post-HSCT. Discussion and Conclusion Allogeneic HSCT has the potential to stabilize or recover pulmonary and cardiac function parameters in SCD patients. In pediatric patients, splenic function parameters showed impressive improvement following HSCT. On the other hand, creatinine clearance decreased significantly in children. This might be a reflection of either normalization of SCD-related hyperfiltration or transplantation-related toxicity, which may also have contributed to the increased prevalence of proteinuria after HSCT. With respect to cerebral damage, cerebral perfusion parameters improved and progression of silent cerebral infarctions was prevented following HSCT. Last, we demonstrate a paucity of evidence regarding the course of renal function, retinopathy, and AVN in adult SCD transplant recipients. More research is needed to define which patients with SCD-related organ damage might benefit most from HSCT and which organs are less likely to recover.

Efficacy of the Allosteric MEK Inhibitor Trametinib in Relapsed and Refractory Juvenile Myelomonocytic Leukemia: A Report from the Children's Oncology Group

Background: Juvenile myelomonocytic leukemia (JMML) is an aggressive myeloproliferative neoplasm of infants and toddlers. Upfront therapies typically include high-dose cytarabine or azacitidine, but the only definitive treatment is hematopoietic stem cell transplantation (HSCT). While HSCT cures ~50% of patients, the prognosis is dismal for those who relapse. In the absence of a second HSCT, patients who relapse have a 2-year overall survival of ~10%. JMML is initiated by germline and somatic driver mutations in NF1, KRAS, NRAS, PTPN11, and CBL. These mutations converge on Ras signaling, leading to elevated levels of active Ras-GTP in specific cell lineages. Genetically engineered mouse (GEM) models accurately model key molecular, biologic, and biochemical features of JMML. Preclinical trials of the allosteric MEK inhibitors in Kras and Nf1 mutant mice demonstrated dramatic phenotypic responses with reduction in white blood cell counts, resolution of splenomegaly, and reversion to normal erythropoiesis. Based on the promising efficacy signal in GEM models, we evaluated trametinib, an orally bioavailable allosteric inhibitor of MEK1/2, in a prospective clinical trial in children with relapsed or refractory JMML to determine the overall response rate to trametinib. Results: Ten infants and children with JMML (median age 23.6 months) were enrolled and all were evaluable for safety and efficacy. Patients received age-adjusted dosing of trametinib for 28-day cycles and could remain on study for up to 12 cycles in the absence of disease progression or toxicity. A clonal Ras pathway mutation was confirmed in the blood and/or bone marrow of all patients. The objective response rate was 50% (two complete and three partial clinical responses). Four patients proceeded to HSCT after receiving protocol therapy and remain alive in complete remission with undetectable levels of the Ras pathway mutation identified at enrollment. Three additional patients completed 12 cycles of trametinib and continue to receive off-protocol therapy 6-24 months later with no change in the variant allele frequency of the underlying Ras pathway mutation. The remaining three patients had progressive disease with two demonstrating molecular evolution by the end of cycle 2. Paired pre- and post-trametinib RNASeq and proteomic analyses confirmed on-target biochemical effects of trametinib with down-regulation of both Ras/MAPK pathway related gene expression and MEK1/2 kinase activity, respectively. To gain deeper insight into how trametinib might affect distinct populations of hematopoietic cells, we generated single cell RNASeq data before and after treatment. The most prominent finding was a reduction in the proportions of classical and non-classical monocytes and broad downregulation of immune-related pathways in all cell populations. However, the downregulation of MAPK signaling genes was confined to specific cell types including, macrophages, classical monocytes, and granulocyte-monocyte progenitors, which uniquely displayed downregulated KRAS-related signatures following treatment. High DNA methylation and the presence of >1 mutation at enrollment correlated with lack of response to trametinib. Conclusions: We conducted an open label, phase 2 trial of trametinib in children with relapsed or refractory JMML. This is the first completed study of a MEK inhibitor in any hematologic malignancy in children. The trial met its primary objective and demonstrated a 50% objective response rate with 70% of patients bridging to a successful HSCT or completing the maximum 12 cycles permitted on study. The three patients who completed 12 cycles continue to receive trametinib off study for as long as 2 years. Although limited by a small number of patients, the long-term survival, and correlative molecular analyses from this trial raise provocative questions about whether certain patients with JMML might be spared the long-term adverse health risks of genotoxic HSCT conditioning regimens based on favorable molecular characteristics at diagnosis. This hypothesis will now be tested in a national, risk-stratified therapeutic trial (NCT05849662) of trametinib in combination with azacitidine in newly diagnosed patients. The authors would like to acknowledge funding and support from: NCTN Operations Center Grant (U10CA180886), NCTN Statistics & Data Center Grant (U10CA180899), and the St. Baldrick's Foundation.

Reclassification of ETS Family Transcription Factor Fusions in Pediatric AML Based on Molecular Drivers

Pediatric Acute Myeloid Leukemia (pAML) patients with a fusion involving an E26 transformation-specific (ETS) transcription factor have traditionally been considered high-risk. The most common fusions include ETV6::MNX1 t(7;12)(q36;p13) and FUS::ERG t(16;21)(p11;q22), yet primary fusion alone has proven incapable of predicting response to treatment. Indeed, within the 60 pAML patients with ETS fusions from the Children's Oncology Group (COG) trials AAML0531 and AAML1031, there were 25 unique fusions and diverse outcomes between patients who did share a primary fusion. A molecular based reclassification of ETS fused pAML could prove beneficial in the development of novel therapeutic additions to standard induction. Here, using genetic and RNAseq data from over 1,400 pediatric patients from AAML0531 and AAML1031, we reclassified ETS patients based on oncogenic transcriptional profiles as well as access to hematopoietic stem cell transplant (HSCT) ( Figure 1A). (19/60) patients presented with an enhanced MYC transcriptional signature (p-val < 0.00) independent of fusion partners [EP300::ETV6, ETV6::CCND3, ETV6::FAM133B, ETV6::FOXO1, ETV6::INO80D, ETV6::LMBR1, ETV6::MNX1, EWSR1::FEV, FLI1::IFIT2, FUS::ERG, FUS::FEV, FUS::FLI1]. Median event-free survival (EFS) was 293.5 days; median overall survival (OS) was 620.5 days. Notably, 100% (19/19) of patients with a MYC-driven signature relapsed; of the six patients who received HCST, five died within 3 years of diagnosis. Preliminary in vitro data in ETS cell lines with an enhanced MYC transcriptional signature (YNH-1, TSU-1621) suggests that the BET bromodomain inhibitor JQ1 may dampen MYC and induce anti-proliferative effects. (7/60) patients were defined by an EZH2-driven “immune-cold” signature characterized by global loss of immune receptors. Patients presented at diagnosis with significantly elevated EZH2 and low levels of MHC I and II receptors typically observed at relapse; additionally, there was significant downregulation in T cell and natural killer cell ligands and a 100% failure rate for HSCT. Median EFS was 255 days and median OS was 339 days. We have previously discussed the mechanism of leukemogenesis as well as proposed therapeutic interventions for this subset (Buteyn, ASH 2021). (34/60) patients did not possess either a MYC-driven or EZH2-driven signature. These “other” ETS were instead defined by whether or not the patient underwent HCST. (21/34) patients did not receive HCST and had median EFS and OS of 429 and 1194 days, respectively. The relapsed or refractory rate in this population was still 75%; (8/14) of R/R patients were deceased within three years. The remaining (13/60) ETS patients did receive HSCT in first remission. (11/13) are still alive and at a rate higher than the general pAML population post-HSCT (62.6%). Despite a survival rate at approximately 85%, ‘Other ETS +HSCT’ patients were all still categorized as ‘High Risk’ at the end of AAML1031. Overall, reclassification based on molecular drivers appears to not only be more accurate in predicting relapse and final outcome, but also in proposing novel agents for pAML patients who overwhelmingly do not respond to standard regimens. Reinvigoration of immune recognition by inhibition of EZH2 and/or inhibition of MYC-driven proliferation via BET inhibitors may prove an essential step in setting the stage for successful HSCT for a significant portion of pAML ETS patients.

Case report: Successful autologous hematopoietic stem cell transplantation in a patient with GAD antibody-spectrum disorder with rapidly progressive dementia

The prevalence of neurological syndromes associated with antibodies to glutamic acid decarboxylase is increasing. While cognitive impairment is a common feature of this condition, it seldom emerges as the primary symptom. In this study, we discuss a case of refractory dementia associated with the glutamic acid decarboxylase spectrum disorder. Interestingly, this case showed a favorable outcome following autologous hematopoietic stem cell transplantation. We also provide an in-depth review of the current literature on the use of this therapeutic approach for the treatment of this disease.

A successful second allogeneic hematopoietic stem cell transplantation from an alternative donor in a patient with loss of HLA heterozygosity relapse of juvenile myelomonocytic leukemia: case series analysis

Juvenile myelomonocytic leukemia (JMML) is a rare and aggressive myeloproliferative/myelodysplastic neoplasm of early childhood characterized by activation of the Ras signaling pathway. Allogeneic hematopoietic stem cell transplantation (alloHSCT) is the only proven curative treatment for JMML. However, the 5-year overall survival is about 52–64%. In this work, we analyzed 4 clinical cases of patients with relapses of JMML with loss of heterozygosity in HLA (LoH) after allo-HSCT. The patients' parents gave their consent to the use of their children's data, including photographs, for research purposes and in publications. Two patients received a second allo-HSCT from an alternative donor, two patients – from the same donor. A positive result in the form of a durable remission was observed in one patient who underwent a second allo-HSCT from an alternative donor and restored HLA genetic heterozygosity. At the same time, immunotherapy with infusions of donor lymphocytes led to the development of graft-versus-host disease without potentiating the antileukemic effect. Thus, a second allo-HSCT from an alternative donor for the treatment of relapsed JMML with HLA LoH is necessary to restore the “graft-versus-JMML” response. The study was approved by the Independent Ethics Committee and the Scientific Council of the I.P. Pavlov First Saint Petersburg State Medical University of Ministry of Healthcare of the Russian Federation.