Hematopoietic stem cell (HSC)-based gene therapies have seen extraordinary progress since their initial conception, now fundamentally transforming the treatment paradigms for various inherited hematologic, immunologic, and metabolic conditions—with additional use cases under exploration. Decades worth of work with advances in viral vector technologies and cell manufacturing have paved the way for HSC gene therapy with marked improvement in the safety and efficiency of gene delivery into HSCs. These have been augmented by the recent rise of innovative genome-editing techniques, particularly using clustered regularly interspaced short palindromic repeats CRISPR-associated proteins (CRISPR-Cas)-based technologies, which have enabled more precise and reproducible genome alterations in HSCs and fostered opportunities for targeted gene modification or gene correction. These breakthroughs have led to the development of many active clinical trials and culminated in the recent federal regulatory-agency approvals of multiple clinical HSC gene therapies for various indications that are now becoming available across different geographies. These treatments aim to offer significant, long-lasting benefits to patients worldwide without the toxicities of alternative treatment approaches. This review explores the history and advancements in HSC gene therapies and provides a comprehensive overview of the latest clinical innovations and cell-therapy products. Further, it concludes with a discussion of the persistent challenges that have limited adoption and potential future opportunities that aspire to enable curative treatment of many different patients through such personalized medicines.

ABSTRACT:Two autologous hematopoietic stem cell (HSC)-based gene therapies (GTs) are now commercially available for severe sickle cell disease and transfusion-dependent β-thalassemia. However, the safety and efficacy of a subsequent autologous HSC-based GT after graft failure with a previous allogeneic hematopoietic cell transplant (HCT) remains unclear. Some individuals who have experienced a failed first attempt at a potentially curative therapy might seek a second opportunity for cure via GT. In this article, we discuss various factors related to patient and HSC health that may influence feasibility, and shared decision-making regarding whether an individual who has previously received an allogeneic HCT and experienced graft failure could consider an autologous GT. Exposure to chronic inflammatory stress and conditioning chemotherapy may compromise HSC fitness, reduce hematopoietic reserve, accelerate HSC aging, and promote the accumulation of deleterious genetic mutations, all of which may adversely affect the safety and efficacy of the GT.

BACKGROUND:Cardiac complications after haematopoietic cell transplantation in paediatric patients are significant yet under-recognised. Pericardial effusion has been associated with worse outcomes and transplant-related mortality. OBJECTIVES:We aimed to evaluate the incidence, risk factors, and clinical course of pericardial effusion after paediatric allogeneic haematopoietic cell transplantation. We identified transplantation recipients "at risk" for clinically significant pericardial effusion based on our definition, described our clinical experience and provided recommendations for screening and management. STUDY DESIGN:Clinical data of children who underwent allogeneic haematopoietic cell transplantation at Texas Children's Hospital from January 2010 to April 2021 were analyzed retrospectively. Factors potentially contributing to time to pericardial effusion, time to pericardial effusion resolution, and overall survival were evaluated. RESULTS:We included 629 haematopoietic cell transplantation recipients with a median age at transplantation of 8.5 years (0.1-24.3). Seventy-three patients (11.6%) developed pericardial effusion within a median time of 102 days (1-403) post-haematopoietic cell transplantation, and 50 (68.5%) had resolution of pericardial effusion at the time of last evaluation. Older age at the time of haematopoietic cell transplantation, transplant-associated thrombotic microangiopathy, and cytomegalovirus diagnoses independently increased the risk of pericardial effusion development, while cytomegalovirus diagnosis decreased the likelihood of pericardial effusion resolution. Both non-significant pericardial effusion development and clinically significant effusion development were significantly associated with post-haematopoietic cell transplantation mortality, compared to no pericardial effusion development. CONCLUSIONS:Paediatric haematopoietic cell transplantation recipients with malignant diseases, older age at the time of transplantation, cytomegalovirus infection, or transplant-associated thrombotic microangiopathy are at higher risk for pericardial effusion development, which in turn predicts worse outcomes with increased risk of death. We propose a model for improved detection, evaluation, and management of pericardial effusion post-haematopoietic cell transplantation.

BACKGROUND:Immune effector cell (IEC) therapies, including chimeric antigen receptor (CAR)-modified T-cell therapy, have shown efficacy in pediatric B-cell acute lymphoblastic leukemia (B-ALL) and are being investigated for other malignancies. A common toxicity associated with IEC therapy is cytokine release syndrome (CRS), which can lead to cardiovascular decompensation due to systemic inflammation. Data are limited regarding cardiovascular adverse effects in children. This study aims to describe the cardiovascular adverse effect profile of IEC therapies in pediatric patients with hematologic and solid tumor malignancies. METHODS:We retrospectively reviewed patients who received IECs directed towards various targets in patients with hematologic, solid, and brain tumor malignancies from January 2014 to June 2023 at Texas Children's Hospital. The primary end point was hypotension requiring vasoactive support and/or heart failure within 30 days of infusion. RESULTS:A total of 203 patients met inclusion criteria. Pretreatment echocardiogram was available for 142 (70%) pediatric patients, of whom 140 (96%) had normal baseline systolic function. Hypotension requiring vasoactive support occurred in 26 (13%) patients. Hematologic malignancy indications (p = 0.002), total body irradiation (TBI) (p = 0.002), and allogenic hematopoietic stem cell transplants (HCT) (p = 0.035) were associated with increased risk of hypotension requiring vasoactive support. Follow-up echocardiograms were available for 14 patients who met the primary end point, and all showed return to baseline within 6 months. CONCLUSIONS:Significant hemodynamic compromise occurred in a minority of patients treated with IEC therapies. All experiencing cardiac dysfunction had recovery of function, and there was no cardiovascular-related mortality.

IntroductionGenetically modified cellular therapies (GMCT) using autologous hematopoietic stem cells are under investigation for various inherited disorders including inborn errors of immunity (IEI) and non-IEI indications. Disease and conditioning related defects in immunity vary across indications for GMCT and contribute to appropriate variations in practice. Nonetheless, evidence-based guidance for infection prevention is lacking. We sought to understand current practices around GMCTs from clinicians participating in GMCT clinical trials.MethodsWe identified individuals potentially experienced with GMCTs based on clinical trial participation on ClinicalTrials.GOV. After obtaining IRB approval electronic surveys were distributed via email.ResultsWe approached 94 individuals in 11 countries. Seven of 21 responses for IEI and 19 of 25 for non-IEI from 6 countries (IEI: 3, non-IEI: 5) reported based on clinical experience with GMCTs. Figure 1SurveillanceAll IEI GMCT respondents (n=7) reported standardized viral surveillance including weekly cytomegalovirus (CMV) monitoring (n=7), and regular Epstein-Barr virus (EBV) (n=6) and adenovirus (ADV) (n=5) monitoring. Some respondents also reported regular aspergillus antigen surveillance (n=4) and following IgG levels (n=5). Of the non-IEI GMCT respondents (n=19), CMV, EBV, and ADV were followed by 13, 12, and 9, respectively. Aspergillus antigen surveillance was not common practice (n=5). IgG levels were followed by 10 respondents. Table 1ProphylaxisFor IEI GMCT, all respondents reported use of Pneumocystis jirovecii (PJP) and fungal prophylaxis (ppx). Four reported using CMV ppx, 4 herpes simplex virus (HSV) ppx, and 3 varicella zoster virus (VZV) ppx. For non-IEI GCMT, use of ppx for PJP (n=18), fungus (n=15), and HSV (n=17) was common. Standard CMV and VZV ppx was infrequent. Encapsulated bacteria ppx was used by 11 respondents primarily for hemoglobinopathies (n=10). Table 2Preferred agent, and duration of ppx and surveillance were variable for both groups.Vaccination practicesMost respondents acknowledge need for re-vaccination and use a universal protocol irrespective of pre-exiting immunity (IEI: 3, non-IEI: 9) or based on serology (IEI: 2; non-IEI: 7). Across both groups start of re-vaccination varied from 3 to 12 months after GMCT.ConclusionReported infection prevention strategies are similar across respondents treating IEIs, but widely variable for non-IEI GMCT. Frequency and duration of monitoring and ppx were particularly inconsistent. Addressing re-vaccination is common albeit with variable implementation. Inherent variability and absence of evidence-based guidance has resulted in lack of standardization and difficulty in determining the ideal approach to infection protection. There is a need for development of rational guidelines based on harmonized assessment of risk after GMCTs.

There is lack of guidance for immune monitoring and infection prevention after administration of ex vivo genetically modified hematopoietic stem cell therapies (GMHSCT). We reviewed current infection prevention practices as reported by providers experienced with GMHSCTs across North America and Europe, and assessed potential immunologic compromise associated with the therapeutic process of GMHSCTs described to date. Based on these assessments, and with consensus from members of the International Society for Cell & Gene Therapy (ISCT) Stem Cell Engineering Committee, we propose risk-adapted recommendations for immune monitoring, infection surveillance and prophylaxis, and re-vaccination after receipt of GMHSCTs. Disease-specific and GMHSCT-specific considerations should guide decision making for each therapy.

IntroductionData on the use of vedolizumab (a monoclonal antibody blocking α4β7 integrin) for treatment of lower gastrointestinal (LGI) acute graft versus host disease (aGVHD) post allogeneic hematopoietic stem cell transplantation (HCT) in pediatrics is restricted to case reports or single center studies with limited subject number and variable response rates.ObjectiveWe report the real-world outcomes on the safety and efficacy of vedolizumab for treatment of steroid refractory LGI aGVHD in children and young adults in a multi-center setting.MethodsAll patients who received vedolizumab for treatment of steroid refractory LGI aGVHD from 2017-2022 at 5 institutions were included. Descriptive statistics were used to analyze the data.ResultsTwenty-four patients with a median age 12.75 (range 0.25-25.17) years at HCT were included; majority were male (54%), with a malignant indication (69%) who received a myeloablative conditioning (67%). The median onset of aGVHD was 36.5 days (range 12-202 days) post-HCT with most patients (98%) having Grade III-IV aGVHD. Organ involvement at time of start of vedolizumab therapy were GI only (n=7), GI+ skin (n=11), GI + liver (n=1) and GI+ skin+ liver (n=5). A median of 4 doses (range 1-27) of vedolizumab were given starting at a median 115 days (32-330 days) post-HCT. Vedolizumab was given as 2nd line therapy (n=2) or as an adjunct 3-8th line agent (n=22). In patients surviving through day(D)+100 (n=23) post-vedolizumab therapy (Figure 1), D+28 intestinal responses showed an overall response rate (ORR) of 74% [complete response (CR): 6, very good partial response (VGPR): 6, partial response (PR):5] with 6 non-responders (NR). At D+100, the ORR was 69% (CR: 12, VGPR:4,) with 7 NR. Intestinal responses were sustained through D+180 (with 1 additional VGPR). Amongst D+28 responders (n=17), the mean baseline steroid dose decreased from 1.5 mg/kg (range 0-2.5 mg/kg) to 0.79 mg/kg (range 0-2.4mg/kg) at D+28 and 0.2 mg/kg (range 0-0.8 mg/kg) at D+100. Thirteen (54%) patients developed chronic GVHD (7 with GI or Liver involvement). No patient had infusion-related side effects. Post-vedolizumab therapy, twenty-three new infection events (10 bacterial,12 viral and 1 fungal) were observed in 15 (63%) patients. At a median follow up of 16 months (range 0.6-53), mortality was 37%, (n=9), with 11 of the fifteen surviving patients still receiving systemic immunosuppression (1 on vedolizumab).ConclusionOur data support the use of vedolizumab for ameliorating steroid refractory LGI aGVHD in children and young adults. However, its use in the real-world setting was mostly as an adjunct with multiple other lines of therapy, with an expected high incidence of infections due to use of extensive immune suppression in this cohort.

Pediatric hematopoietic cell transplant (HCT) is associated with significant morbidity and mortality despite advances in management of HCT-related complications. Cardiac complications, including pericardial effusion (PEF), are an underestimated subset of complications post-HCT, reported in 5-17% of adult HCT recipients. Pediatric literature is limited but suggests a prognostic impact on survival. We report a retrospective review study evaluating incidence, associations, and clinical course of clinically significant PEF (cPEF) following HCT in a large cohort comprised of 703 allogeneic HCT recipients at a single tertiary pediatric institution between January 2010 and December 2020.We defined cPEF as: symptomatic with moderate-large effusion on echocardiogram, clinical or echocardiographic evidence of tamponade, necessity of medical interventions or pericardiocentesis, or a combination of these.PEF was diagnosed in 141 patients; 68 were excluded based on PEF diagnosis: pre-HCT, after relapse or after second HCT. PEF was diagnosed in 10% (73/703) of patients, while ∼6% (40/703) had cPEF. Median time to PEF development was 92 days post-HCT.Of 40 patients with cPEF, 58% (n=23) were male and median age at transplantation was 13 years. The indication for HCT was hematological malignancy in 68% (n=27). Myeloablative conditioning was used in 70% (n=28). We identified cPEF within 100 days post-HCT in 53% (n=21). Half of patients with cPEF (n=20) were managed with observation alone. Twelve patients were managed medically either with diuretics, corticosteroids, NSAIDs or other anti-inflammatory drugs. Pericardiocentesis was performed in 20% (n=8), six of whom were initially managed with medications. Pericardial fluid analysis was unrevealing except for positive CMV PCR in 1 patient with known CMV viremia. Acute GVHD was noted in 30% (n=12) and chronic GVHD in 5% (n=2). TA-TMA was present in 45% (n=18) and CMV infection in 43% (n=17). Ultimately, 24 patients (60%) had resolution of cPEF. At 1-year post-HCT, 19/40 of patients (48%) with cPEF were alive .Landmark analysis demonstrated that out of the patients that remained alive at day 92, the patients that had already developed clinically significant PEF had a significantly higher risk of death (HR=2.579, p=0.0167) compared to those that had not yet developed any PEF. Further analyses using a control cohort of 502 patients without PEF are ongoing.The incidence of PEF in our cohort was comparable to what has been reported, with around half of patients developing cPEF. Clinically significant PEF post pediatric HCT is multifactorial. TA-TMA, CMV infection, and aGVHD commonly co-occurred with cPEF, and cPEF development within 92 days post-HCT was associated with increased mortality. Prospective studies identifying optimal screening, associations, and management of cPEF after pediatric HCT are necessary.

The Blood and Marrow Transplant Clinical Trials Network (BMT CTN) 1507 leadership and the data safety monitoring board (DSMB) established incremental entry criteria for children aged 5 to 14.99 years with sickle cell disease (SCD) enrolling in a phase 2 trial of HLA-haploidentical hematopoietic stem cell transplantation. First, the enrollment was limited to overt stroke in the first 10 participants (stage 4). Subsequently, the DSMB reviewed the interim results and expanded the eligibility to include children with silent cerebral infarcts or abnormal transcranial Doppler velocities with magnetic resonance angiography-defined cerebral vasculopathy (stage 3). A third cohort was enrolled after the DSMB reviewed the clinical outcomes in these cumulative initial enrollments (n = 18) and additions were made to the entry criteria that included nonneurologic morbidities (stage 2). Added eligibility criteria included the heart catheterization confirmed pulmonary hypertension; (3) persistent systemic hypertension despite maximum medical therapy; (4) acute pain despite maximum medical therapy in the absence of psychosocial factors and unmanaged asthma after adjudication; and (5) 2 major priapism episodes in 12 months or 3 in 24 months. Children with SCD who did not meet the criteria for stages 4, 3, and 2 were not eligible. To our knowledge, for the first time, we introduce a staged strategy for eligibility in a curative therapy trial for children with SCD concordant with 45 Code of Federal Regulations 46.405(b). The research governance-mandated eligibility strategy used within the BMT CTN 1507 phase 2 study may apply to future pediatric SCD curative therapy trials. This trial was registered at www.ClinicalTrials.gov as #NCT032635590.

IntroductionPeople with sickle cell disease (SCD) experience deficits in executive functioning in the areas of attention, inhibitory control, planning, and working memory. As a pilot evaluation to understand executive function deficits in individuals with SCD with and without hematopoietic stem cell transplant (HSCT) we measured task inhibition with Go/No-Go (GNG) task-based functional magnetic resonance imaging (fMRI).MethodsParticipants underwent GNG fMRI at a single timepoint. GNG is designed to measure response inhibition of a prepotent task and correlates with activation within the inferior frontal gyrus. Participants view a series of letters on a screen during fMRI and are instructed to push a button when they see any letter (Go) except for the letter X (No-Go). A higher number of Go tasks with interspersed No-Go tasks maintains a prepotency to push the button and causes purposeful effort for inhibition. Because of variance associated with commission errors, analyzing activation that is associated only with correct response inhibitions (No Go Correct > Go Correct) is most valuable. Response inhibition data were correlated to the mean change in activation percent in blood oxygen level dependent (BOLD) signal on fMRI within the posterior cingulate cortex, and bilateral caudate, pars triangularis, and pars opercularis during the isolated time points when No Go Correct > Go Correct.ResultsFive individuals with SCD underwent fMRI, 2 post successful HSCT 22 and 29 months prior (Table 1). GNG task analysis results are shown in Table 2. Data from this sample showed that when No Go Correct > Go Correct, activation within the inferior frontal gyrus (pars opercularis and pars triangularis) was statistically equivocal. However, there appeared to be a trend toward relative activation in HSCT participants as expected compared to healthy subjects in the literature and relative deactivation in SCD participants, suggesting aberrant connectivity in the latter (Figure 1).ConclusionNeurocognitive outcomes are a challenging aspect of SCD to study despite the important impact deficits play on quality of life. fMRI is a tool to measure neurocognitive function, particularly executive function, with more nuance than battery testing alone. This pilot was not powered to conduct meaningful between-group analysis. However, the trend toward aberrant activation patterns in individuals with SCD that was not appreciated in the post HSCT subjects suggests a potential for improved connectivity in patients who have undergone HSCT and may indicate possible neurologic healing in this context. A longitudinal prospective pre-post intervention study following patients over multiple timepoints is necessary to better understand a causal relationship to the differences observed.

While matched related donor (MRD) allogeneic hematopoietic stem cell transplantation (HSCT) is a curative option for transfusion-dependent beta-thalassemia (TDT), the use of alternative sources has increased, resulting in the exploration of novel transplant-conditioning regimens to reduce the contribution of graft-versus-host disease (GVHD) and graft failure (GF) to transplant-related morbidity and mortality. Alemtuzumab is a CD52 monoclonal antibody that has been successfully incorporated into myeloablative conditioning regimens for other hematologic conditions, yet there have been limited studies regarding the use of alemtuzumab in HSCT for TDT. The purpose of this study was to evaluate engraftment, incidence of GVHD, and transplant related morbidity and mortality in patients with TDT who received alemtuzumab in addition to standard busulfan-based conditioning. The primary endpoint was severe GVHD-free, event-free survival (GEFS). Our cohort included 24 patients with a median age of 6.8 years (range 1.5-14.9). Eleven patients received a 10/10 MRD HSCT, eleven 10/10 unrelated donor (UD), and two mismatched UD. All patients achieved primary engraftment. For all patients, 5-year GEFS was 77.4% and 5-year overall survival (OS) was 91%. The 5-year cumulative incidence of GF (attributed to poor graft function) without loss of donor chimerism was 13.8% (95% CI: 4.5, 35.3). We report low rates of significant acute GVHD grade II-IV (12.5%) and chronic GVHD (4.4%). Younger age and MRD were associated with significantly improved GEFS, OS and EFS. Our results show that the use of alemtuzumab promotes stable engraftment, may reduce rates of severe GVHD, and results in acceptable GEFS, OS, and EFS.

Introduction: Secondary cytopenias occurring after hematopoietic cell transplant (HCT) are an observed complication of graft-versus-host disease (GVHD). Causes include peripheral immune mediated destruction (hemolytic anemia or thrombocytopenia), usually associated with autoantibody production, and peripheral destruction associated with microangiopathy (TMA). However, cases have been observed where marrow production of the affected lineage is abnormal. Immune-mediated cases are treated with increased immunosuppression, e.g., steroids or calcineurin inhibitors (CNI), and TMA with complement inhibition. To better understand the mechanisms and treatment of hypoproductive cytopenias in GVHD, we combined analyses of hematopoietic stem and progenitor cells (HSPC) and peripheral blood and marrow activated T cells. We describe 3 cases of GVHD-associated cytopenias marked by HSPC depletion and presence of CD25 (IL-2R alpha subunit)-positive activated T cells in the marrow that responded to combinations of immunosuppression containing basiliximab (basil) anti-CD25 monoclonal antibody blockade. Methods/Results: We describe combined HSPC and T cell analyses in 3 patients (P) with severe GVHD-associated cytopenias. P1 was at 5 years post-HCT for acute lymphoblastic leukemia, P2 at 2 years post-HCT for severe aplastic anemia (SAA), and P3 at 1.5 months post-liver transplant for alcohol use disorder-associated cirrhosis and hepatocellular carcinoma ( Table 1). Because of refractory cytopenias, all were being considered for HCT. However, marrow analyses revealed that each had normal frequencies of phenotypic HSC, with variable decreases in cellularity and frequencies of committed progenitors ( Table 2). Chimerism analyses showed that 100% of CD34+ cells in P1 and P2 were of donor origin, and in P3 of host origin. All 3 marrows had activated CD3+ T cells per expression of CD69 and/or CD38, and frequency of CD25 on >10% of T cells. In addition, P1 had evidence of IgG bound to committed progenitor populations. The treatment strategy was to block IL-2 signaling with basil (induction of 20 mg on day 1, 4, 7, 14, 21, 28, followed by alternate week and then monthly dosing for 2-9 months), combined with suppression of IL-2 production with steroid and/or CNI. After induction, repeat analyses of the blood and marrow T-cells confirmed complete blockade of CD25. Therapy was also individualized for specific clinical conditions or as noted on marrow evaluation. P1 received prednisone, CNI, and rituximab for a presumed anti-HSPC autoantibody. At 9 months he was weaned off all therapy and remains on no immunosuppressive treatment 2 years later. P2 did not receive CNI due to chronic renal failure but received steroids and later sirolimus. At ~18 months, his cytopenias recurred, but subsequently responded to basil re-induction and steroids. P3 has received prednisone, CNI, and sirolimus indefinitely for prevention of liver rejection and/or hepatocellular carcinoma relapse. P1 had no viral reactivation; P2 had CMV pneumonia with his second course responsive to antiviral therapy, completion of basil, and tapering of steroids; and P3 had CMV reactivation responsive to antiviral therapy and EBV viremia. P3 has a recent diagnosis of EBV+ intrahepatic B cell lymphoma. In all cases, blood counts normalized except P2 who has anemia due to CKD. Discussion: HSPC analyses in these patients with GVHD and cytopenias demonstrate that peripheral changes are not due to loss of HSC, but instead to quantitative and/or qualitative defects in committed progenitor populations, likely mediated by activated CD25+ T cells. In addition, the presence of IgG on HSPCs in P1 demonstrates a novel role for antibody-mediated humoral suppression in some cases. The presence of HSC indicates that there may be no need for re-transplant. Previous studies of SAA have shown activated T cells to be drivers of aplasia and is the basis for immune suppressive therapy (anti-thymocyte globulin and CNI). Our analyses of patients with GVHD-associated cytopenias demonstrates that targeting of IL-2 signaling via combined CD25 receptor blockade and pharmacologic inhibition of IL-2 production can correct the marrow defects and cytopenias, albeit with need for attention to viral infections. Targeting CD25 in patients with evidence of CD25+ activated T cells is a rational approach to the difficult problem of GVHD-associated marrow suppression and cytopenias.

Sickle cell disease (SCD) is an inherited hemoglobin (Hb) disorder which leads to significant morbidity and early mortality. Hematopoietic cell transplantation (HCT) is the only curative treatment with long-term outcome data, demonstrating excellent symptom-free survival particularly when a matched related donor (MRD) is available. Most MRD have sickle cell trait (Hb AS), but trait donor HCT is considered acceptable by the FDA and without negative impact. Further, initial gene addition and editing approaches for SCD have resulted in a trait-like status with benefit. Sickle trait, however, is associated with complications such as papillary necrosis, bacteriuria, splenic infarction, and exercise-induced death. The primary aim of this study was to compare long-term outcomes following MRD HCT for SCD based on donor Hb genotype, to objectively describe any impact on outcomes. Retrospective data was available for this analysis on 182 SCD patients ≥1 year post MRD HCT at 10 participating Sickle Transplant Advocacy and Research (STAR) Alliance centers. Summary statistics were presented as mean (standard deviation) for continuous variables and count (%) for categorical variables. Comparisons were made between Hb AA and Hb AS donor groups using both parametric and non-parametric tests for continuous variables and Chi-square test/exact test for categorical variables, with p-value <0.05 set as significant. Amongst 182 patients undergoing MRD HCT, 67% (n=122) had a Hb AS donor ( Table). In the overall cohort, median age at HCT was 8.7 (4.8) years and most patients had HbSS (n=174; 96%) with a severe clinical phenotype (n=97; 54%). HCT was performed using bone marrow (n=166; 92%) with myeloablative conditioning (n=156; 86%) in the majority. Patients with a severe disease phenotype and Hb AS donor were significantly more likely to have recurrent vaso-occlusive pain crises as an indication for HCT (p=0.033), otherwise there were no differences in baseline patient or HCT characteristics between cohorts. With mean post-HCT follow up of 4.5 (3.9) and 5.1 (4.1) years in Hb AA and Hb AS donor cohorts (p=0.145), no significant differences were seen in recipient outcomes including time to neutrophil and platelet engraftment, number of or time to last platelet transfusion, myeloid or unsorted % donor chimerism, number with acute (day 100) or chronic GVHD (1 year), or time to discontinue immunosuppression (data not shown). Disease recurrence and need for 2 nd HCT were rare in both cohorts (AA: 2 [3%] and 2 [3%]; AS: 3 [3%] and 4 [3%]; p=0.665 and 1.0, respectively). Two (3%) and 5 (4%) patients died in the AA and AS cohorts, respectively (p=1.0). Aside from a statistically (but not clinically) significant difference in Hb at day 30 (p=0.044), no difference was seen in longitudinal Hb or markers of hemolysis (LDH and ARC; Figure). No significant difference was seen in median number of RBC units transfused (AA: 4.0 [2.0-6.0]; AS: 3.0 [2.0-6.0]; p=0.454) or days to last transfusion (AA: 23.0 [14.0-77.0]; AS: 22.0 [13.0-75.0]; p=0.86). SCD complications were rare post-HCT, with no difference seen between cohorts in number (%) with VOC (AA: 1 [2%; had 2 separate VOC events]; AS: 3 [3%]; p=1.0), ACS (none reported), chronic pain (AA: 0 [0%]; AS: 1 [<1%]; p=1.0), or other SCD-related complications (AA: 2 [3%]; AS: 9 [7%; had 11 separate other events]; p=0.456). Stroke occurred in a significantly higher proportion with an AA versus AS donor (5 [8%] and 2 [2%], respectively; p=0.04). No significant differences were seen in longitudinal (1 and 2 years and at last follow up) post-HCT cardiac (EF, SF, TRJ velocity), pulmonary (FEV1, FVC, DLCO), or renal (GFR) function between cohorts (data not shown). Our results indicate that in MRD HCT for SCD, AS and AA donors yield comparable long-term outcomes. In this retrospective and registry-based study design, detailed analyses did not show differences between the two cohorts at baseline or at any timepoint post-HCT. While there were some outcome differences between the cohorts, they were either not clinically significant or did not have a scientific rationale, and thus were likely due to chance alone (denoted by bolding in Table). Given the young age of our cohort at HCT and thus a smaller proportion with SCD-related organ dysfunction, our results may not be applicable to an older cohort with significant organ dysfunction which will require a separate analysis.

Background: Allogenic hematopoietic stem cell transplantation (HCT) and ex vivo autologous gene therapies (GT) are potentially curative treatments for sickle cell disease (SCD). However, there is debate around how to define cure including what degree of donor chimerism or level of functional hemoglobin constitutes a cure. Information on red cell function post-HCT/GT and how it relates to donor chimerism and resolution of SCD complications is scarce. Red cell function tests are not currently part of follow-up care post-HCT but may provide helpful information on the degree of red cell correction and risk of SCD complications. To address this knowledge gap, we report rheology and whole blood viscosity data on HbSS patients post-HCT or GT. Methods: Blood samples were collected under an IRB-approved protocol at Baylor College of Medicine and Emory University School of Medicine. We analyzed elongation index maximum and minimum (EImax, EImin), point of sickling (PoS), hematocrit-viscosity ratio at shear rates of 45 and 225 s-1(HVR45 & HVR225), and dense red blood cell % (DRBC%). EImax, EImin, and PoS were measured using a Laser Optical Rotational Red Cell Analyzer (Lorrca, RR Mechatronics, The Netherlands). Chimerism was measured by short tandem repeat testing (STR) after cell density sorting and DRBC% was measured on ADVIA cell counter (Siemens, Germany). HCT patients were compared with controls matched to the donor's genotype, and patients post-GT were compared with HbAS controls (HCT: HbAA donor =8, HbAS donor=19, GT=2, HbAA controls=42, and HbAS controls=15). Stata 18.0 (College Station, Texas, USA) was used to perform statistical analyses. Median values and ranges were used to describe the data. Wilcoxon rank sum test was used to compare groups and a mixed model was for the longitudinal data. A p-value <0.05 was considered statistically significant. Results: There were 29 patients with a median age of 6.6 years (range: 2.0-16.3) at HCT/GT and a median follow-up of 2.4 years (range: 0.1-7). A total of forty-three samples were analyzed. Median donor myeloid chimerism was 94% (33-100). Overall, the HbS% ranged from 28.9 - 45.2% with HbAS donors and 0% with HbAA donors. Two HbAS HCT patients had myeloid chimerism ≤ 50% with a follow-up period of 3.3 and 1.9 years, respectively. The myeloid donor% and HbS% were 33% and 50%, and 45.2% and 41.6%, respectively. At the first post-HCT/GT time-point (median 1 year, range: 0.1-6.9), DRBC%, EImax, and EImin were lower in HbAA donor HCT patients compared to HbAA controls (0.593 vs 0.604, p=0.008; 0.581 vs 0.604, <0.001; and 0.75 vs 0.20, p=0.02, respectively). RBC function improved with a longer follow-up from HCT/GT (median 2.9 years, range 1.3-7) with EImax showing a trend of statistical significance (p=0.07). Patients with HbAS donors had significantly higher point of sickling (PoS) values compared to the patients with HbAA donors (p=0.02). There was a trend for a lower HVR225 in patients with HbAS donors compared to the patients with HbAA donors (p=0.08). Seven patients (24%) had one or more red cell function test values outside the genotype-matched control range despite having myeloid donor chimerism of > 25-30% - a value commonly used in clinical practice to define cure (Table & Figure). Conclusion: A substantial number of patients had abnormal red cell function tests following HCT/GT despite achieving donor engraftment. Donor myeloid chimerism ≥ 25% has been reported protective from SCD complications while a chimerism ≥50% normalized tests for hemolysis. Higher odds of SCD-related complications have been reported with higher PoS and lower EImax/EImin. Thus, we propose that red cell function should be included in follow-up care of HCT/GT patients until values normalize and clinical relevance is further assessed.

Men with type 2 diabetes are often characterized by abnormal plasma testosterone levels. This study was aimed at investigating whether testosterone treatment has an impact on cardiovascular risk factors in patients with type 2 diabetes and late-onset hypogonadism (LOH), chronically treated with hypoglycemic agents.This study included 51 men with type 2 diabetes, 26 of whom had already been treated with metformin and 25 with glimepiride for at least 6 months. On the basis of patient preference, 15 men receiving metformin and 12 receiving glimepiride were treated with intramuscular testosterone enanthate (100 mg weekly) for 12 weeks. Plasma lipids, glucose homeostasis markers, as well as plasma levels of androgens, uric acid, high-sensitivity C-reactive protein (hsCRP), homocysteine and fibrinogen were determined before and at the end of the study.With the exception of insulin sensitivity, plasma hsCRP and homocysteine, there were no differences between patients treated with metformin and glimepiride. Testosterone enanthate administered to both groups of patients increased plasma testosterone, reduced plasma hsCRP and improved insulin sensitivity. Testosterone-metformin combination therapy reduced also circulating levels of uric acid, homocysteine and fibrinogen. These effects, stronger in patients treated with metformin than glimepiride, correlated with the impact of testosterone on insulin sensitivity.Our results suggest that testosterone may bring more clinical benefits to metformin- than sulfonylurea-treated men with diabetes and LOH.

The MECOM gene encodes multiple protein isoforms that are essential for hematopoietic stem cell self-renewal and maintenance. Germline MECOM variants have been associated with congenital thrombocytopenia, radioulnar synostosis and bone marrow failure; however, the phenotypic spectrum of MECOM-associated syndromes continues to expand and novel pathogenic variants continue to be identified. We describe eight unrelated patients who add to the previously known phenotypes and genetic defects of MECOM-associated syndromes. As each subject presented with unique MECOM variants, the series failed to demonstrate clear genotype-to-phenotype correlation but may suggest a role for additional modifiers that affect gene expression and subsequent phenotype. Recognition of the expanded hematologic and non-hematologic clinical features allows for rapid molecular diagnosis, early identification of life-threatening complications, and improved genetic counseling for families. A centralized international publicly accessible database to share annotated MECOM variants would advance their clinical interpretation and provide a foundation to perform functional MECOM studies.

Background: Serotherapies such as anti-thymocyte globulin (ATG) and alemtuzumab (AL) are added to conditioning chemotherapy for matched related donor (MRD) hematopoietic cell transplantation (HCT) for sickle cell disease (SCD) to facilitate engraftment and prevent graft-vs-host disease (GVHD). Most reports show ATG added to myeloablative (MA) conditioning; however, the use of AL has increased with investigation of different intensity regimens. The aim of this study was to compare HCT-related outcomes across common conditioning approaches to determine superiority. Methods: Retrospective data on baseline patient and HCT characteristics, and HCT outcomes were collected on 352 SCD patients >1 yr post-HCT at 14 Sickle cell Transplant Advocacy and Research (STAR) Alliance centers. Patients with a non-MRD (n=117) or without serotherapy (n=26) were excluded, leaving 209. MA included busulfan (BU) cumulative dose (CD) >8mg/kg or TBI ≥800 cGy; other regimens were termed non-MA (nMA). Summary statistics were presented as median (IQR) for continuous variables and count (%) for categorical variables. Comparisons were made using two-sample hypothesis tests, with p-value of < 0.05 as significant. Time-to-event analyses followed out to 3 years (censored after) and considered 4 outcomes. The first 3 were estimated via the Kaplan-Meier method: (1) overall survival (OS); (2) rejection-free survival (RFS); with death and rejection as events; (3) severe GVHD-free, RFS (GRFS), with death, RFS and severe GVHD as events; and (4) GVHD was estimated by Fine-Gray competing risk analyses, considering death as a competing event and censoring for rejection. Results: 209 patients received MRD HCT with MA+AL (66, 32%), nMA+AL (49, 23%), MA+horse (hATG) (71, 34%), or MA+rabbit (rATG) (23, 11%). Median recipient and donor age at HCT were 8.4yr (IQR: 5.1, 13.0) and 9.3 (5.1, 15.0) and similar across cohorts. MA+AL had a less severe clinical phenotype and nMA+AL had decreased pulmonary function; other baseline characteristics were similar (data not included). Conditioning for MA+AL included bu/cyclophosphamide (cy) (64%) or bu/fludarabine (flu) (36%), for MA+hATG bu/cy (68%) or bu/cy/flu (32%), for MA+rATG bu/cy (83%) or bu/flu (17%), and for nMA+AL melphalan/flu (92%) plus thiotepa (TT) (8%). GVHD prophylaxis was primarily calcineurin inhibitor and methotrexate or mycophenolate mofetil (91.4%). In MA, serotherapy was proximal timed with AL starting day -5 or -6 at a median (IQR) CD of 1.05mg/kg (0.8, 1.5), hATG starting day -3 at 90mg/kg (90), or rATG starting day -5 at 10mg/kg (9.6, 10.1); in nMA, AL was distal timed starting day -22 at a CD of 1.98mg/kg (1.0, 2.8). Stem cells were bone marrow in all, and GCSF primed in 15.4% of MA+AL and 4% of nMA+AL. Total nucleated and CD3 cell doses were similar across cohorts. nMA+AL had shorter median follow up at 2y (1, 4) vs 3y (2, 6) overall. nMA+AL had earliest time to neutrophil engraftment, required less platelet infusions, and had a shorter hospital stay at median 13d (12, 15), 8 infusions (4,13), and 21d (18, 26), respectively. Readmissions were highest for MA+AL at 77% (vs 64% overall). Graft rejection occurred only in nMA+AL (4, 8.2%) and MA+rATG (2, 8.7%). Table 3-yr CI of grade III/IV aGVHD was highest in nMA at 12% (CI: 0.05, 0.23) vs 0-7%, p=0.130 and for any cGVHD was significantly higher in nMA+AL at 33% (0.19, 0.46) vs 9-19%, p=0.001. 3-year OS was excellent at 94.4% (91.3, 97.7) and comparable per cohort. 3-year RFS was lowest though not significantly in nMA+AL at 87% (0.78, 0.97) vs 91-97%, p=0.260. 3-year GRFS was significantly lower in nMA+AL at 69% (0.57, 0.83) vs 83-94%, p=0.001. When age controlled GRFS in nMA+AL ≥13y was significantly lower at 59% (0.40, 0.88) vs 74-100%, p=0.007. Figure Conclusions: Despite small cohort sizes and retrospective nature, this study allowed for direct comparison of common approaches to MRD HCT for SCD. Outcomes were collectively excellent. nMA had earlier engraftment, less transfusion needs, and shorter hospital stay, although significantly more cGVHD and lower 3-yr GRFS influenced by older age. Current clinical trials in nMA+AL include TT and abatacept to mitigate this difference. We previously reported an association between MA and cardiac dysfunction (Stenger et al. Transplant Cell Ther 2023). Potential benefit of nMA must be balanced against risk of rejection and GVHD, thus providers should carefully consider such when selecting conditioning.