Successful Hematopoietic Cell Transplantation Research Articles

One size does NOT fit all – factoring weight into current stem cell transplant guidelines in multiple myeloma patients

Abstract Autologous hematopoietic stem cell (HPSC) transplantation serves as the standard of care treatment for multiple myeloma patients. The standard ASCT procedures for multiple myeloma (MM) patients often includes induction therapy, stem cell collection via apheresis and autologous hematopoietic cell transplantation (HCT) for eligible patients. The current guideline for HPSC collection for multiple myeloma established that 3x106 cells/kg of actual body weight (ABW) by the 1997 study of stem cell transplants in breast cancer. Recent research indicates that ideal body weight (IBW) utilization is a stronger predictor of post-autotransplantation neutrophil recovery than calculations based on ABW. Reducing the cost of HPSC collection and cryopreservation is critical to mitigate the cost incurred by the transplant center and the patient. This study evaluates whether using a patient’s IBW or Adjusted Ideal Body Weight (AIBW) would be satisfactory in determining the amount of stem cells required for transfusion when compared to ABW. After institutional review board approval, a retrospective chart review study analyzed a cohort of 224 deceased MM patients, who received HCT at the UAB Medicine Hospital within the fiscal years of 2017 to 2019. The ABW for each patient was used to calculate their IBW and AIBW using the formulas shown below. The target CD34+ cell amount for patients was calculated using each body weight parameter. The platelet count and absolute neutrophil count (ANC) defined a successful platelet and neutrophil engraftment. The engraftment date was determined as the day the platelet value exceeded 20 and ANC exceeded 0.5 for three consecutive days (without any transfusion within a seven day window) and a statistical analysis was utilized to determine whether the IBW and AIBW parameters were adequate to achieve successful engraftment and HCT. This study finds that the cohort of multiple myeloma patients are significantly more overweight than the prior study that established the current guidelines for autologous hematopoietic cell transplantation. The results for CD34+/kg cell targets for ideal and adjusted ideal body weight suggests that there are minimal differences in platelet and neutrophil engraftment and number of platelet transfusions when compared to CD34+/kg targets using actual body weight. Some methods to reduce excessive stem cell collection include decreasing target cell dosage from previous standards of 6.0 x 106 cells/kg or calculating total cell dosage with IBW or AIBW instead of ABW. Future studies should evaluate the efficacy of cell dosage decrease to lowered targets and total cell calculations using IBW or AIBW instead of ABW. Equation 1. ABW to IBW Conversion (H = height over 5 ft. in inches) IBW(males) = 50 kg + (2.3 kg x H) IBW(females) = 45.5 kg + (2.3 kg x H) Equation 2. ABW to AIBW Conversion AIBW = IBW + 0.5(ABW-IBW)

Successful Hematopoietic Cell Transplantation in Patients with Fanconi Anemia with Severe Renal Insufficiency

Successful Hematopoietic Cell Transplantation in Patients with Fanconi Anemia with Severe Renal Insufficiency

Residual Mast Cells Can Explain Persistent Molecular Positivity in Difference from Normal Flow Cytometric-Defined MRD Negative Core Binding Factor AML

Introduction: Core binding factor acute myeloid leukemia (CBF-AML) accounts for 30% of pediatric and 15% adult AMLs and is defined by fusions involving RUNX1 or CBFB. RT-PCR is commonly used to monitor measurable residual disease (MRD) in patients with CBF-AML. However, it has been reported that these fusions can be detected in patients during complete remission (CR) or after hematopoietic cell transplant (HCT). This raises the question of if these patients should be considered MRD positive, given they appear otherwise disease free. We utilized flow cytometric cell sorting and fluorescent in situ hybridization (FISH) to determine the source of persistent CBF fusions. Methods: Flow cytometry was used to isolate mast cells (CD117 bright/CD34 negative) from 13 patients with CBF-AML fusions (8 RUNX1:: RUNX1T1 and 5 CBFB:: MYH11) alongside progenitor cells (CD34+/CD117 heterogeneous, 12 patients) and T cells (CD3+, 11 patients) as available for FISH analysis. These patients were fusion positive by RT-PCR but had no evidence of MRD by difference from normal multidimensional flow cytometry (ΔN), the gold standard for determination of residual disease in Children's Oncology Group-sponsored clinical trials for AML. Cells were sorted from 6 additional patients with a history of RUNX1:: RUNX1T1 CBF-AML who were MRD negative by ΔN but without RT-PCR results available. Results: In 11/13 patients, the mast cell fraction was positive for the CBF fusion but all other sorted cell fractions tested were negative. In the remaining two specimens, all cell fractions were negative, likely due to FISH sensitivity compared to RT-PCR. Both CBF fusions exhibited the same pattern, with fusions detected only in the mast cell fractions (7 RUNX1:: RUNX1T1 and 4 CBFB:: MYH11). The additional 6 patients who were MRD negative by ΔN but without RT-PCR data followed the same pattern, with RUNX1:: RUNX1T1 detected by FISH in the mast cells (6/6 patients) and not in other sorted populations (5/6 patients sorted for progenitor and T cells). Two patients had a clinical history of CBF-AML and systemic mastocytosis (SM). ΔN revealed no evidence of residual AML but showed abnormal mast cells with expression of CD2 and CD25, consistent with abnormalities associated with SM. FISH analysis of sorted mast cells revealed the presence of the RUNX1:: RUNX1T1 fusion, while progenitor and T cells were both negative. In all other patients the mast cells showed no phenotypic abnormalities, demonstrating that CBF fusions can be detected in both phenotypically normal and abnormal mast cells in patients who are free of residual AML. Two patients with CBFB:: MYH11 fusions had specimens evaluated by FISH on sorted cells over a month apart where the fusion persisted only in the mast cells. Two patients with RUNX1:: RUNX1T1 fusions had serial specimens analyzed at 4 different timepoints. One patient had fusion positive mast cells for over 8 months after residual disease was last detected by ΔN. The other patient, who had previously undergone HCT, harbored fusion positive mast cells for 13 months. Both patients remained MRD negative by ΔN over the course of testing. Discussion: These data demonstrate that in CBF-AML, fusions can be detected exclusively in the mast cells of otherwise leukemia-free patients, resulting in positive RT-PCR results in the absence of any other disease pathology. These mast cells can be normal or abnormal and can persist after successful HCT. Given that these patients are free of disease by other measures, these fusion positive mast cells do not appear to contribute to AML pathogenesis. Additionally, this post-HCT fusion positive persistence demonstrates a potential clinical implication: if patients such as reported here are assessed pre-transplant using RT-PCR on unsorted specimens alone, they may not be considered candidates for HCT even though the fusion is confined to terminally differentiated cells and successful transplant can be achieved. For these reasons, while RT-PCR is a specific and accurate assay, caution is required for CBF-AML patients. Flow cytometry and cell sorting in combination with genetic testing, in this case FISH, protect against these mast cell driven positive results and provide an accurate assessment of disease status. These data highlight the importance of considering AML biology and combining multiple testing methods to monitor AML patients comprehensively and accurately.

Post-Transplant Cyclophosphamide Eliminates Disparity in GvHD-Free, Relapse-Free Survival and Overall Survival between 8/8 Matched and 7/8 Mismatched Unrelated Donor Hematopoietic Cell Transplantation in Adults with Hematologic Malignancies

Background: Post-transplant cyclophosphamide (PTCy) has become a standard of care for graft-versus-host disease (GvHD) prophylaxis in recipients of human leukocyte antigen (HLA)-matched and mismatched unrelated donor (MMUD) allografts, generating new opportunities for successful hematopoietic cell transplantation (HCT) regardless of patient ancestry. The National Marrow Donor Program (NMDP)-sponsored 15-MMUD study, which used PTCy-based GvHD prophylaxis (PMID 3390526), demonstrated encouraging overall survival (OS) in adult patients receiving MMUD bone marrow grafts matched at ≤7/8 HLA alleles. Currently, the follow-up ACCESS study (NCT04904588) will determine if similar outcomes can be achieved using MMUD peripheral blood stem cell allografts. As part of its 5-year strategic plan, the NMDP aims to determine the extent of differences in GvHD-free, relapse-free survival (GRFS) between 8/8 and 7/8 URD allografts using PTCy and seeks to develop approaches over time to close the presumed gap in URD outcomes. Methods: The primary objective was to compare GRFS between 8/8 and 7/8 URD HCT using the Center for International Blood & Marrow Transplant Research (CIBMTR) database. After analyzing primary results, secondary objectives were added to compare GRFS, OS, and other clinical outcomes among 8/8 URD, 7/8 URD, and haploidentical-related donor (Haplo) HCT. The study included adult patients (age≥18y) with hematologic malignancies (ALL, AML, MDS) undergoing first URD or Haplo HCT between 2017-2020 using PTCy-based GvHD prophylaxis. Kaplan-Meier curves were used to estimate probability of GRFS and OS. Cox regression examined the independent effect of HLA match controlling for other clinical factors on outcomes referenced to 8/8 URD HCT. A priori clinically selected factors considered as possible confounders in the regression model included disease risk index, comorbidity risk, pre-HCT Karnofsky score, conditioning regimen intensity, graft source, donor/recipient CMV serostatus, year of HCT, donor/recipient age and race/ethnicity. Final models were stratified by factors violating the proportional hazards assumption. Factors were eliminated in a backwards fashion if p-values were >0.10 unless inclusion affected the hazard ratio (HR) of HLA match by more than 10%. Interactions were tested against a p-value of <0.01. Results: Table 1 shows demographics for the three patient cohorts: Haplo (n=2772), 8/8 URD (N=1517), and 7/8 MMUD (N=540). Notable differences among the cohorts included: 8/8 URD recipients had younger, predominantly Caucasian donors and were more likely to receive myeloablative conditioning. Haplo recipients had more donor/recipient CMV seropositivity and received more reduced intensity conditioning. Otherwise patient characteristics were similar. Contrary to our expectations, multivariable regression analysis (MVA) showed no significant differences in either GRFS or OS between recipients of 8/8 and 7/8 URD HCT at 1, 2 and 3-years post-HCT ( Figure 1). Outcomes, including relapse and NRM, between 8/8 and 7/8 URD HCT were similar irrespective of conditioning intensity. However, 8/8 URD HCT associated with lower two-year moderate/severe chronic GvHD than 7/8 URD [1.30 (1.00-1.68), p=0.049]. We next compared GRFS and OS among 8/8 and 7/8 URD and Haplo at 3y after HCT. On MVA, GRFS [HR 1.15 (1.04-1.26), p=0.005] and OS [HR 1.15 (1.03-1.29), p=0.013] were significantly better in 8/8 URD compared to Haplo HCT. Differences between 8/8 URD and Haplo appeared to be driven by significantly higher NRM [HR 1.46 (1.22-1.74), p<0.001)] and two-year moderate/severe chronic GvHD [HR 1.28 (1.07-1.54), p=0.007] in Haplo. No significant differences were seen in GRFS or OS at 3 years when comparing 7/8 URD to Haplo. Causes of death among donor types were similar with primary disease relapse/progression, infection and organ failure being the most frequent. Conclusions: Use of PTCy-based GvHD prophylaxis seems to have resolved previously observed differences in GRFS and OS between 8/8 and 7/8 URD HCT. HCT using an 8/8 URD HCT, if available, continues to be the best option for patients lacking a matched sibling donor. Further studies comparing Haplo to 7/8 URD HCT are warranted, but will require larger numbers of 7/8 URD HCT. Both mismatched donor sources substantially increase access to HCT for patients regardless of their ancestry.

Haploidentical Hematopoietic Cell Transplant with Post-Transplant Cyclophosphamide Expedites Donor-Derived Immune Reconstitution in a Pediatric Severe Aplastic Anemia Cohort

Severe aplastic anemia (SAA) is a life-threatening, idiopathic process involving the immune-mediated destruction of hematopoietic stem cells. Treatment involves immunosuppressive therapy (IST) and/or allogeneic hematopoietic cell transplantation (HCT). The latter has recently been optimized with use of a post-transplant cyclophosphamide (PTCy) based graft-versus-host disease (GvHD) platform, permitting successful HCT with only half-HLA-matched haploidentical donors. In pediatrics, this platform results in >90% overall survival with low rates of GvHD and graft failure. However, reports on donor chimerism and immune reconstitution are limited. We hypothesized that a PTCy platform would expedite CD3 donor engraftment and CD4 T cell recovery. In a phase III clinical trial, we treated three cohorts of pediatric (age </=25 years) patients with SAA requiring alloHCT: MUD, MSD, and HAPLO. The MUD cohort included n=15 recipients of 7-8/8 HLA-matched unrelated donor grafts (n=5 7/8, n=10 8/8) with median age 14 years (range 2-17 years), following cyclophosphamide (Cy) 50 mg/kg, fludarabine (Flu) 200 mg/m 2, rabbit anti-thymocyte globulin (rATG) 9 mg/kg total dose rabbit and low dose total body irradiation (TBI) at 200 cGy. The MSD cohort included n=9 recipients of 8/8 HLA-matched sibling donor grafts with median age 15 years (range 12-24 years), following Cy 200 mg/kg and 9 mg/kg rATG. The HAPLO cohort included n=4 recipients of 4/8 HLA-matched related donor grafts with median age 8.5 years (range 2-21 years) following Cy 29 mg/kg, Flu 150 mg/m 2, 9 mg/kg rATG, and low dose TBI at 200 cGy. GvHD prophylaxis consisted of 30 days of mycophenolate mofetil, and 100 days of a calcineurin inhibitor (followed by an 8-10 week taper), with the HAPLO cohort additionally receiving post-transplant Cy (PTCy) 50 mg/kg/day on days +3 and +4. Peripheral blood lymphocyte counts and peripheral blood and bone marrow donor chimerism were evaluated on days +100, +180 and +365. Recipient characteristics were largely equivalent between cohorts, with 43% receiving IST prior to HCT. Clonality was overrepresented in the HAPLO cohort (2 of 4, 1 with monosomy 7 myelodysplastic syndrome and 1 with a large PNH clone), with only 2 of 15 in the MUD and none in the MSD cohorts. Active controlled infections at the time of HCT were additionally overrepresented in the HAPLO cohort, with disseminated pseudomonas in 1. The MUD cohort had 1 with Rhizopus invasive sinusitis (none in the MSD cohort). Achievement of neutrophil engraftment was statistically significantly delayed in the HAPLO cohort at a median of 17 days compared to 12 for MSD and 14 for MUD, p=0.004), however there were no episodes of primary or secondary graft failure. With only a single late death from intracranial hemorrhage in the MUD cohort, OS was equivalent at 2 years (100% in MSD and HAPLO cohorts, 93.3% in MUD). GvHD rates were low with only 1 (MUD) experiencing grade II acute GvHD, and 1 (MUD) experiencing mild chronic GvHD. Immune reconstitution varied by cohort with statistically significantly greater CD3 peripheral blood donor chimerism (p<0.001) as well as CD4 (p=0.04) and CD8 (p=0.03) T cell counts over time for the HAPLO recipients (CD3 chimerism in Fig 1, CD4 count in Fig 2; 2-way ANOVA fixed effects model). Considering a CD4 >200 cell/uL as clinically meaningful, we assessed the proportion of each cohort achieving this milestone at each timepoint. While each cohort had an increase in proportion achieving CD4>200 over time, the HAPLO cohort reached 50% with CD4 >200 at day +100, compared to 11% MUD and 0% MSD (p=0.09). At day +180, the proportion with CD4 >200 were 36% MUD, 25% MSD and 75% HAPLO (1 yr: 90% MUD, 100% MSD and HAPLO). Donor availability remains a challenge to successful transplant for patients with SAA, and haploidentical matches overcome donor limited accessibility. PTCy as GvHD prophylaxis is associated with low incidences of graft failure and severe GvHD. While PTCy might be anticipated to inhibit donor T cells and immune reconstitution, our data, albeit limited by small cohorts, demonstrates superior and more efficient CD3 donor engraftment and CD4 T cell count recovery following HAPLO HCT with PTCy compared to non-PTCy based MUD and MSD cohorts.

Metformin pretreatment ameliorates busulfan-induced liver endothelial toxicity during haematopoietic stem cell transplantation.

The success of Haematopoietic cell transplantation (HCT) is often limited by regimen-related toxicity (RRT) caused by conditioning regimen drugs. Among different conditioning drugs, busulfan (Bu) and treosulfan (Treo), although widely used in HCT, exhibit different toxicity profiles, the mechanism of which is still unclear. Here we investigated the effects of Bu and Treo in endothelial cells. While both Bu and Treo induced DNA damage in endothelial cells, we observed Bu alone to induce oxidative stress and sustained activation of phospho-ERK1/2, leading to apoptosis. However, Treo-treated cells exhibited no oxidative stress/apoptosis of endothelial cells. Screening of pharmacological inhibitors of both ROS and p-ERK revealed that metformin effectively ameliorates Bu-mediated toxicity in endothelial cells. In Balb/c mice, we observed a significant reduction in bone marrow endothelial cells in Bu-treated mice compared to Treo-treated mice. Further, liver sinusoidal endothelial cells (LSEC) was damaged by Bu, which is implicated in liver vasculature and their functional capacity to uptake FITC-albumin. However, Treo-treated mice liver vasculature was morphologically and functionally normal. When mice were pretreated with metformin followed by Bu, LSECs damage was ameliorated morphologically and functionally. Bone marrow transplants done on these mice did not affect the engraftment of donor cells.

The Transplantation Ecosystem: A New Concept to Improve Access and Outcomes for Older Allogeneic Hematopoietic Cell Transplantation Patients

Allogeneic hematopoietic cell transplantation (HCT) is increasingly offered to older adults with hematologic malignancies, even though nonrelapse mortality remains a major concern in older patients owing to more comorbidities and greater frailty compared with their younger counterparts. The importance of patient fitness, a well-matched donor, and disease control to the success of allogeneic HCT have been well documented; however, these factors fail to account for the impact of the complex transplantation ecosystem (TE) that older adult HCT candidates must navigate. We propose a definition of the TE modeled after the social determinants of health. Furthermore, we outline a research agenda aimed at increasing understanding of the roles of individual social determinants of transplantation health in the larger ecosystem and how they may benefit or harm older adult HCT candidates. Herein we define the TE and its individual tenets, the social determinants of transplantation health. We review the available literature while incorporating the expertise of the membership of the American Society for Transplantation and Cellular Therapy (ASTCT) Special Interest Group for Aging. The membership of the ASTCT Special Interest Group for Aging identify knowledge gaps and strategies to address them for each of the described social determinants of transplantation health. The ecosystem is an essential but underappreciated pillar for transplant access and success. We put forth this novel research agenda seeking to gain a better understanding of the complexity of HCT in older adults and develop strategies to improve access to HCT, survival, and quality of life.

384 - Vaso-Occlusive Pain Requiring Hospitalization or Treatment Is Rare Following Successful Hematopoietic Cell Transplantation for Sickle Cell Disease

384 - Vaso-Occlusive Pain Requiring Hospitalization or Treatment Is Rare Following Successful Hematopoietic Cell Transplantation for Sickle Cell Disease

Combined IFN-γ and JAK inhibition to treat hemophagocytic lymphohistiocytosis in mice

Familial hemophagocytic lymphohistiocytosis is a life-threatening hyperinflammatory disease caused by genetic defects in the granule-mediated cytotoxic pathway. Success of hematopoietic cell transplantation, the only cure, is correlated with the extent of disease control before transplantation. Unfortunately, disease refractoriness and toxicities to standard chemotherapy-based regimens are fatal in a fraction of patients. Novel targeted immunotherapies, such as IFN-γ blocking antibodies or ruxolitinib, a Janus kinase (JAK) 1/2 inhibitor, are promising but only partially effective at controlling disease. We asked whether combinations of cytokine-targeted therapies, using antibodies or JAK inhibitor, work synergistically to counteract HLH. Genetically predisposed mice were infected and treated with distinct combinations of immunotherapies. Disease outcome was monitored and compared to monotherapies. We showed that inhibiting IL-6 or IL-18 signaling in combination with IFN-γ blockade or ruxolitinib did not increase disease control compared to anti-IFN-γ antibodies or ruxolitinib monotherapies. In contrast, clinically relevant doses of ruxolitinib combined with low doses of anti-IFN-γ blocking antibodies corrected cytopenias, prevented overt neutrophilia, limited cytokinemia, and resolved HLH immunopathology and symptomatology. Our findings demonstrate that IFN-γ blockade and ruxolitinib act synergistically to suppress HLH progression. This supports the use of combined cytokine-targeted therapies as a bridge to hematopoietic cell transplantation in severe familial hemophagocytic lymphohistiocytosis.

Conditioning regimens for inborn errors of immunity: current perspectives and future strategies.

Inborn errors of immunity (IEI) are caused by germline genetic mutations, resulting in defects of innate or acquired immunity. Hematopoietic cell transplantation (HCT) is indicated for curative therapy especially in patients with IEI who develop fatal opportunistic infections or severe manifestations of immune dysregulation. The first successful HCT for severe combined immunodeficiency (SCID) was reported in 1968. Since then, the indications for HCT have expanded from SCID to various non-SCID IEI. In general, HCT for IEI differs from that for other hematological malignancies in that the goal is not to eradicate certain immune cells but to achieve immune reconstitution. European Society for Blood and Marrow Transplantation/European Society for Immunodeficiencies guidelines recommend reduced-intensity conditioning to avoid treatment-related toxicity, and the optimal conditioning regimen should be considered for each IEI. We review conditioning regimens for some representative IEI disorders in Japanese and worldwide cohort studies, and future strategies for treating IEI.

JSP191 As a Single-Agent Conditioning Regimen Results in Successful Engraftment, Donor Myeloid Chimerism, and Production of Donor Derived Naïve Lymphocytes in Patients with Severe Combined Immunodeficiency (SCID)

JSP191 As a Single-Agent Conditioning Regimen Results in Successful Engraftment, Donor Myeloid Chimerism, and Production of Donor Derived Naïve Lymphocytes in Patients with Severe Combined Immunodeficiency (SCID)

Assessment of Cardiac Abnormalities in Sickle Cell Disease Patients Using Cardiac Magnetic Resonance Imaging (CMR)

IntroductionSickle cell disease (SCD) is characterized by chronic hemolytic anemia which predisposes patients to high output heart failure. Recently it has been recognized that repetitive microvascular ischemic insults and reperfusion injury result in diffuse myocardial fibrosis and cardiac remodeling that eventually leads to irreparable myocardial injury. Superimposed on these cardiac insults, patients with SCD often have iron overload related to chronic transfusions. Together, these insults produce a unique SCD-related cardiomyopathy characterized by restrictive physiology with LV dilation. Cardiac Magnetic Resonance Imaging (CMR) is the only non-invasive technique for assessing and quantifying diffuse myocardial fibrosis with simultaneous highly accurate assessment of heart size and systolic and diastolic function. Diffuse myocardial fibrosis is measured by a CMR technique called T1 mapping and calculated as extracellular volume (ECV), which may serve as an early marker of sickle cell related cardiomyopathy. An early marker for SCD-related cardiomyopathy would allow for efficient screening, prevention, and institution of treatment strategies. We describe utilization of CMR to evaluate cardiac pathology in a cohort of pediatric SCD patients.MethodsTwenty-six children with SCD underwent CMR, as clinically indicated, between January 2020 and July 2021 at our institution. We analyzed cardiac chamber size (left atrium [LA], left ventricle [LV], right ventricle [RV]), systolic and diastolic function parameters, and quantitative myocardial parametric mapping values (T1 pre- and post-contrast and T2*) for these patients. ECV was calculated for all patients using T1 pre- and post-contrast values in conjunction with current hemoglobin values. Four patients underwent an allogeneic hematopoietic cell transplant (HCT) for SCD and had serial CMR performed before and 1 month after HCT.ResultsMedian age of patients was 17 years; 12 (70%) were female; 22 (84%) had HbSS, 3 (12%) had HbSC and 1 (4%) had Hb S beta thalassemia. 15 (58%) patients had LA enlargement and only a few had ventricular enlargement (LV, 11 [42%]; RV, 9 [35%]). Patients rarely had had LV (4 [15%]) or RV (1 [4%]) systolic dysfunction. Twenty-five (96%) patients had increased ECV; median 30.5% (IQR 28-34%, reference normal 20.8% +/- 2.4). All patients had normal myocardial T2* values indicating no myocardial iron deposition. Additional details are provided in Table. Among those who underwent HCT, all 4 had elevated ECV at baseline, which improved in 1 patient 1-month post-HCT (27% [pre] to 21% [post]). One patient had a dilated LA at baseline with the other 3 developing LA dilation at 1-month post HCT.ConclusionCMR provides accurate and reproducible measurements of chamber sizes/ventricular volumes, myocardial mass, and ventricular function. Multiparametric mapping enabled quantitative evaluation of myocardial fibrosis in patients with SCD. We found that diffuse myocardial fibrosis is often present in children with SCD, even those with apparently normal cardiac function.This indicates damage to the myocardium occurs before symptoms or measurable changes on echocardiography, calling into question our current screening procedures. T1 mapping to monitor the progression of fibrosis could help evaluate response to current therapies including SCD directed therapies, cardioprotective medications, and curative options such as HCT and gene therapy. Hence, we believe that cardiac MRI is complementary to echocardiography and provides additional clinically relevant information that will help guide treatment in patients with SCD.Additionally, it has been shown that patients with SCD who undergo successful HCT exhibit significant improvements in cardiac size, function, and diastolic filling parameters as early as 3 months after the procedure, with improvements continuing slowly up to 1 year after HCT. Early post-HCT evaluation in our cohort did show moderate improvement in ECV in one HCT recipient. Further follow up with serial monitoring is ongoing to evaluate long term changes in these patients. Data on additional patients who have undergone serial CMR monitoring after HCT will be presented at the ASH annual meeting. [Display omitted] DisclosuresSharma: CRISPR Therapeutics: Other, Research Funding; Medexus Inc: Consultancy; Spotlight Therapeutics: Consultancy; Novartis: Other: Salary support paid to institution; Vertex Pharmaceuticals/CRISPR Therapeutics: Other: Salary support paid to institution; Vindico Medical Education: Honoraria. Hankins: UpToDate: Consultancy; Global Blood Therapeutics: Consultancy; Vindico Medical Education: Consultancy; Bluebird Bio: Consultancy. Triplett: Miltenyi: Other: Travel, meeting registration.

Therapeutic Vaccination of Hematopoietic Cell Transplantation Recipients Improves Protective CD8 T-Cell Immunotherapy of Cytomegalovirus Infection.

Reactivation of latent cytomegalovirus (CMV) endangers the therapeutic success of hematopoietic cell transplantation (HCT) in tumor patients due to cytopathogenic virus spread that leads to organ manifestations of CMV disease, to interstitial pneumonia in particular. In cases of virus variants that are refractory to standard antiviral pharmacotherapy, immunotherapy by adoptive cell transfer (ACT) of virus-specific CD8+ T cells is the last resort to bridge the “protection gap” between hematoablative conditioning for HCT and endogenous reconstitution of antiviral immunity. We have used the well-established mouse model of CD8+ T-cell immunotherapy by ACT in a setting of experimental HCT and murine CMV (mCMV) infection to pursue the concept of improving the efficacy of ACT by therapeutic vaccination (TherVac) post-HCT. TherVac aims at restimulation and expansion of limited numbers of transferred antiviral CD8+ T cells within the recipient. Syngeneic HCT was performed with C57BL/6 mice as donors and recipients. Recipients were infected with recombinant mCMV (mCMV-SIINFEKL) that expresses antigenic peptide SIINFEKL presented to CD8+ T cells by the MHC class-I molecule Kb. ACT was performed with transgenic OT-I CD8+ T cells expressing a T-cell receptor specific for SIINFEKL-Kb. Recombinant human CMV dense bodies (DB-SIINFEKL), engineered to contain SIINFEKL within tegument protein pUL83/pp65, served for vaccination. DBs were chosen as they represent non-infectious, enveloped, and thus fusion-competent subviral particles capable of activating dendritic cells and delivering antigens directly into the cytosol for processing and presentation in the MHC class-I pathway. One set of our experiments documents the power of vaccination with DBs in protecting the immunocompetent host against a challenge infection. A further set of experiments revealed a significant improvement of antiviral control in HCT recipients by combining ACT with TherVac. In both settings, the benefit from vaccination with DBs proved to be strictly epitope-specific. The capacity to protect was lost when DBs included the peptide sequence SIINFEKA lacking immunogenicity and antigenicity due to C-terminal residue point mutation L8A, which prevents efficient proteasomal peptide processing and binding to Kb. Our preclinical research data thus provide an argument for using pre-emptive TherVac to enhance antiviral protection by ACT in HCT recipients with diagnosed CMV reactivation.

Increased Proportion of Sickle Cell Disease Patients Develop Cardiovascular Disease Risk Factors Following Successful Hematopoietic Cell Transplantation

Background: Hematopoietic cell transplantation (HCT) is currently the only proven curative treatment for sickle cell disease (SCD), with >90% event-free survival using a matched related donor (MRD). Long-term follow up in patients transplanted for malignant disease demonstrates a 4-fold increase in risk of developing cardiovascular disease (CVD). Risk factors for CVD include obesity, hypertension, diabetes, and dyslipidemia, which are reported in a higher incidence in both survivors of HCT and childhood malignancy. While patients with SCD typically have lower weight and blood pressure (BP) for age, cure of SCD may lead to decreased metabolic demand as well as increased weight and BP, thus uniquely predisposing post-transplant SCD subjects to CVD risk. Further, because of premature mortality due to SCD, true risk of CVD in these patients may be unknown.Objective: To investigate the development of CVD risk factors in SCD subjects who underwent HCT with myeloablative conditioning.Methods: We performed a retrospective data collection on SCD subjects who underwent allogeneic HCT at Children's Healthcare of Atlanta (CHOA) and survived to ³1 year post-HCT. Data on baseline patient and transplant characteristics as well as CVD risk factors (body mass index [BMI], BP, and cholesterol) were collected. BMI was categorized per CDC definition as underweight (<5th%), healthy weight (5th% to <85th%), overweight (85th% to <95th%), or obese (≥95th%). BP was categorized as >50th% and >90th% for patients with SCD, as per Table 1 in Pegelow et al. Pre- and post-HCT values were compared using Wilcoxon signed-rank tests or McNemar's tests, with p-values <0.05 considered statistically significant.Results: Sixty-seven SCD subjects underwent allogeneic HSCT from December 1993 to March 2016 at CHOA, 63 of whom survived to ≥1 year post-transplant. Fourteen patients did not have pre- or post-HCT BMI data available, thus were excluded from the analyses. Majority had clinically severe SCD (77.8%) and received bone marrow (93.3%) from a matched sibling donor (91.1%). Conditioning was myeloablative in all, majority using a combination of busulfan, cyclophosphamide, and anti-thymocyte globulin ± fludarabine. Patients underwent HCT at a median age of 8.8 years (range 1.8-20.3), at which time 40 (88.9%) were healthy weight, while 3 of each (6.7%) were underweight, overweight, and obese (Table 1). At last follow up (median age 10.3 years; range, 3.8-21.8), 27 patients (60.0%) were healthy weight, while 6 (13.3%) were underweight, 5 (11.1%) overweight, and 7 (15.6%) obese. When pre- and post-transplant BMI categories were compared, 66.7% of patients had no change, whereas 17.8% increased and 15.6% decreased. Of the 8 patients whose BMI category increased, 6.7% became overweight and 11.1% obese. Of the 7 patients who BMI category decreased, 2 obese patients (28.6%) became overweight, 2 overweight patients (28.6%) became obese, and 3 normal weight patients (42.9%) became underweight. BMI significantly increased from a median of 16.2 kg/m2 pre- to 19.0 kg/m2 post-HCT (p<0.001). There was no increase in the proportion of patients exceeding either the 50th or 90th percentile for systolic BP post-HCT (Figure 1). The proportion with diastolic BP exceeding 50th or 90th percentile for age for SCD was increased post-HCT compared to baseline. Five patients were diagnosed with hypertension ≥6 months post-transplant, 4 of whom were receiving treatment for chronic graft-versus-host disease (GVHD; steroids, cyclosporine [CSA], or steroids plus CSA) and 1 of whom was overweight. Routine cholesterol testing was rare, consistent with a pediatric cohort, with only 2 patients having hypercholesterolemia, both of whom were receiving treatment for chronic GVHD. Two patients had mildly elevated hemoglobin A1c levels post-HCT and none were diagnosed with diabetes. Ten patients developed chronic GVHD (22.0%), 8 of whom remained in a stable BMI category, with 1 of each either increasing or decreasing.Discussion: Following successful HCT, patients with SCD developed relative diastolic hypertension and increased BMI, both of which are known risk factors for CVD. Patients who developed chronic GVHD were more likely to be diagnosed with hypertension and/or hypercholesterolemia, although BMI category was not impacted. These data provide the rationale for longer term follow up for CVD risk factors and CVD in patients with SCD following HCT. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

International retrospective study of allogeneic hematopoietic cell transplantation for activated PI3K-delta syndrome

Background:Activated phosphoinositide 3-kinase delta syndrome (APDS) is a combined immunodeficiency with a heterogeneous phenotype considered reversible by allogeneic hematopoietic cell transplantation (HCT).Objectives:This study sought to characterize HCT outcomes in APDS.Methods:Retrospective data were collected on 57 patients with APDS1/2 (median age, 13 years; range, 2–66 years) who underwent HCT.Results:Pre-HCT comorbidities such as lung, gastrointestinal, and liver pathology were common, with hematologic malignancy in 26%. With median follow-up of 2.3 years, 2-year overall and graft failure–free survival probabilities were 86% and 68%, respectively, and did not differ significantly by APDS1 versus APDS2, donor type, or conditioning intensity. The 2-year cumulative incidence of graft failure following first HCT was 17% overall but 42% if mammalian target of rapamycin inhibitor(s) (mTORi) were used in the first year post-HCT, compared with 9% without mTORi. Similarly, 2-year cumulative incidence of unplanned donor cell infusion was overall 28%, but 65% in the context of mTORi receipt and 23% without. Phenotype reversal occurred in 96% of evaluable patients, of whom 17% had mixed chimerism. Vulnerability to renal complications continued post-HCT, adding new insights into potential nonimmunologic roles of phosphoinositide 3-kinase not correctable through HCT.Conclusions:Graft failure, graft instability, and poor graft function requiring unplanned donor cell infusion were major barriers to successful HCT. Post-HCT mTORi use may confer an advantage to residual host cells, promoting graft instability. Longer-term post-HCT follow-up of more patients is needed to elucidate the kinetics of immune reconstitution and donor chimerism, establish approaches that reduce graft instability, and assess the completeness of phenotype reversal over time.

Immune Dysregulation in Human ITCH Deficiency Successfully Treated with Hematopoietic Cell Transplantation

Mutations in ITCH, which encodes an E3 ubiquitin-protein ligase, can result in systemic autoimmunity and immunodeficiency. The clinical phenotype and mechanism of disease have not been fully characterized, resulting in a paucity of therapeutic options for this potentially fatal disease. We aimed to (1) expand the understanding about the phenotype of human ITCH deficiency (2) further characterize the associated immune dysregulation, and (3) report the first successful hematopoietic cell transplant (HCT) in a patient with ITCH deficiency. Disease profiling was performed in a patient with multisystem immune dysregulation. Whole exome sequencing with trio analysis and functional validation of candidate disease variants were performed, including mRNA and protein expression. Analyses to further delineate the immunophenotype included quantitative evaluation of lymphoid and myeloid subsets with flow cytometry and mass cytometry. A patient with multisystem immune dysregulation presenting with growth failure, very-early-onset inflammatory bowel disease, arthritis, uveitis, psoriasis, and type 1 diabetes mellitus underwent whole exome sequencing, which identified novel compound heterozygous mutations in ITCH. Reduced expression of ITCH mRNA and absent ITCH protein were found. Abnormalities in both lymphoid and myeloid lineages were identified. The patient underwent HCT. He demonstrated excellent immune reconstitution and resolution of many manifestations of his systemic disease. Here we report ITCH deficiency with unique clinical features of colonic very-early-onset inflammatory bowel disease, arthritis, and uveitis in the setting of immune dysregulation and further characterize the underlying immune dysregulation. We demonstrate that HCT can be an effective, and potentially curative, therapy for ITCH deficiency.

Maternal microchimerism and cell-mediated immune-modulation enhance engraftment following semi-allogenic intrauterine transplantation.

Successful intrauterine hematopoietic cell transplantation (IUT) for congenital hemoglobinopathies is hampered by maternal alloresponsiveness. We investigate these interactions in semi-allogenic murine IUT. E14 fetuses (B6 females × BALB/c males) were each treated with 5E+6 maternal (B6) or paternal (BALB/c) bone marrow cells and serially monitored for chimerism (>1% engraftment), trafficked maternal immune cells, and immune responsiveness to donor cells. A total of 41.0% of maternal IUT recipients (mIUT) were chimeras (mean donor chimerism 3.0±1.3%) versus 75.0% of paternal IUT recipients (pIUT, 3.6±1.1%). Chimeras showed higher maternal microchimerism of CD4, CD8, and CD19 than non-chimeras. These maternal cells showed minimal responsiveness to B6 or BALB/c stimulation. To interrogate tolerance, mIUT were injected postnatally with 5E+6 B6 cells/pup; pIUT received BALB/c cells. IUT-treated pups showed no changes in trafficked maternal or fetal immune cell levels compared to controls. Donor-specific IgM and IgG were expressed by 1%-3% of recipients. mIUT splenocytes showed greater proliferation of regulatory T cells (Treg) upon BALB/c stimulation, while B6 stimulation upregulated the pro-inflammatory cytokines more than BALB/c. pIUT splenocytes produced identical Treg and cytokine responses to BALB/c and B6 cells, with higher Treg activity and lower pro-inflammatory cytokine expression upon exposure to BALB/c. In contrast, naïve fetal splenocytes demonstrated greater alloresponsiveness to BALB/c compared to B6 cells. Thus pIUT, associated with increased maternal cell trafficking, modulates fetal Treg, and cytokine responsiveness to donor cells more efficiently than mIUT, resulting in improved engraftment. Paternal donor cells may be considered alternatively to maternal donor cells for intrauterine and postnatal transplantation to induce tolerance and maintain engraftment.

Hematopoietic Cell and Solid Organ Transplantation in the Same Patient: Long-Term Experience at the University of Minnesota

There is a growing population of transplant survivors receiving both a solid organ transplantation (SOT) and a hematopoietic cell transplantation (HCT). This group remains underreported and not well described. We conducted a single-center retrospective study aimed at assessing safety and long-term survival outcomes of 40 patients receiving both HCT and SOT at the University of Minnesota. Twenty-seven patients underwent HCT followed by SOT (13 kidney, 10 lung, 2 liver, 1 heart, 1 heart/kidney) with a median age of 40 years (range, 5 to 72) at the time of SOT at a median of 88 months (range, 24 to 302) following the HCT. The 1-, 5-, and 10-year overall survival (OS) from the SOT was 93%, 76%, and 49%, respectively, with only 4 organ failures reported. Thirteen other patients received a HCT following a prior kidney (n=8), liver (n=4), or pancreas/kidney (n=1) SOT with a median age of 42 years (range, 3 to 66) at the time of the HCT and a median 154 months (range, 1 to 304) from the SOT. The 1-, 5-, and 10-year OS from HCT were 46%, 46%, and 17% respectively. In patients receiving SOT followed by HCT, survival outcomes were better in kidney transplant recipients and patients subsequently requiring an autologous rather than an allogeneic HCT. There were no HCT engraftment failures. Our findings show that in a select patient population, undergoing a second transplant at a specialized center can lead to favorable outcomes with long-term survival and low incidence of graft rejection, organ failure, and malignant disease relapse. A large-scale study is needed to determine the incidence and risk factors preferred for a successful subsequent SOT or HCT. Those studies are crucial to further guide selection and management of patients who would benefit most from a second transplant.

Universal Sensitive, Accurate and Precise Microchimerism Surveillance Solution for Allogeneic Hematopoietic Cell Transplant

The success of hematopoietic cell transplantation (HCT) is limited by a high rate of disease relapse. Post-HCT chimerism analysis is typically used to evaluate donor cell engraftment and success of therapy in allogeneic HCT. The detection of microchimerism, especially in the early period after allogeneic HCT, is an important high-risk factor for disease relapse (Ahci et al, 2017). However, common approaches based on semi-quantitative fluorescent PCR of short tandem repeats (STRs) suffer from low sensitivity and high result variability and often fail to detect microchimerism and predict patient outcomes (Schuurhuis et al, 2018). Here, we describe development and characterization of AlloHemeTM, a novel sensitive and precise chimerism surveillance solution with high accuracy for detection and quantification of low levels of patient cells which ultimately can lead to clinical disease recurrence. The method is compatible with chimerism assessment in whole blood, bone marrow, or specific cell subtypes. CD3, CD15, CD33 and CD34 markers are used to separate T cells, myeloid progenitors and granulocytes from blood and hematopoietic stem cells from bone marrow, respectively. A minimum of 8ng genomic DNA is used to amplify hundreds of single nucleotide polymorphisms (SNPs) using target specific primers in a single multiplex reaction. Because there is no need to select genetic variants that differ for specific donor-patient pair, the method is universally applicable to any allogeneic HCT. Relative contribution of SNP alleles is measured by Next Generation Sequencing (NGS) and % chimerism of post-HCT samples is calculated using an analysis pipeline incorporating open source and custom bioinformatics tools. To evaluate reproducibility of cell subtype separation, blood from 3 healthy volunteers was subjected to cell separation for CD3, CD15 and CD33 cells at four different timepoints after draw (24, 48, 72 and 96 hours). Flow cytometry analysis using non-competing antibodies targeting same cell populations demonstrated that the cell subtype isolation step consistently yields sub-populations with an average purity of 96% across all cell subtypes and timepoints evaluated (93-99% range). To evaluate assay sensitivity, accuracy and precision, genomic DNA samples (gDNA, Coriell Institute) were used to prepare 2 panels, A and B, each containing different mixtures of gDNAs to simulate post-HCT samples with varying contribution of patient's cells. Panel A contained mixtures of gDNA samples from unrelated individuals ranging from 0.01-50% and panel B from related (parent-child) ranging from 0.01-75%. Each mixture was tested in 6 (Panel A) or 5 (Panel B) independent replicates. The results show that the assay is accurate from 0.03% through 50% for panel A and 0.1% through 75% for panel B with minimal proportional and systematic bias (Figure 1). The assay precision is high, with a mean coefficient of variation (CV) of 2.6% for panel A and 6.1% for panel B across the entire linear range. For sample mixtures with chimerism levels greater than 1%, mean CV was 0.76% for panel A and 1.62% for panel B. AlloHeme results show that the test can detect microchimerism down to 0.03%. High result reproducibility is achieved through the use of a proprietary NGS process and automated data analysis and workflow, generating results in the CLIA lab with a turnaround time of 3 days. The test was developed with rigorous QC steps to ensure high purity and accuracy for each cell population analyzed, increasing confidence and sensitivity of results. Given previously published data on clinical value of microchimerism, AlloHeme has the potential for early relapse detection post-HCT. Future studies will evaluate the utility of AlloHeme in clinical setting with the goal to improve patient outcomes and survival rates. In summary, we have developed a sensitive, accurate and precise method for the universal detection and quantification of chimerism and potential early disease recurrence detection for allogeneic HCT patient surveillance. Because the method provides high sensitivity and consistent results for microchimerism detection, it may be particularly suited to help identify recurrence of primary disease in hematologic cancer patients with or without known cancer-associated genetic determinants. Disclosures Egidio: CareDx: Current Employment, Current equity holder in publicly-traded company. Janakiraman:CareDx: Current Employment. Mao:CareDx: Current Employment. Gulbahce:CareDx: Current Employment, Current equity holder in publicly-traded company, Research Funding. Wong:CareDx: Current Employment, Current equity holder in publicly-traded company, Research Funding. Marchis:CareDx: Current Employment, Current equity holder in publicly-traded company, Research Funding. Ghosh:CareDx: Current Employment. Grskovic:CareDx: Current Employment, Current equity holder in publicly-traded company, Patents &amp; Royalties, Research Funding.

Collection and Processing of Mobilized Mouse Peripheral Blood at Lowered Oxygen Tension Yields Enhanced Numbers of Hematopoietic Stem Cells.

Mobilized peripheral blood (mPB) hematopoietic stem (HSCs) and progenitor (HPCs) cells are primary sources for hematopoietic cell transplantation (HCT). Successful HCT requires threshold numbers of high-quality HSCs to reconstitute hematopoiesis long-term. Nevertheless, considerable percentages of patients and healthy donors fail to achieve required thresholds of HSCs with current mobilization regimens. In this present study we demonstrate that similar to mouse bone marrow (BM) and human cord blood, collection and processing of mouse Granulocyte Colony Stimulating Factor (G-CSF)-, AMD3100/Plerixafor- or G-CSF plus AMD3100/Plerixafor-mobilized HSCs in 3% O2 results in enhanced numbers of rigorously-defined phenotypic and for G-CSF - and G-CSF plus AMD3100/Plerixafor - mPB enhanced functionally-engrafting HSCs. These results may be of potential clinical utility. Graphical Abstract.