allo-SCT Patients Research Articles

Coordinating expensive, difficult-to-obtain prophylactic medications before discharge: A quality improvement project in an academic stem cell transplant unit.

337 Background: Infections are a significant source of morbidity/mortality in allogeneic stem cell transplant (alloSCT) patients and antimicrobial prophylaxis has reduced deaths. Between July 2022 and July 2023, 21% of new alloSCT recipients were discharged from UVA Medical Center without posaconazole or isavuconazonium +/- letermovir in-hand at the time of hospital discharge necessitating daily oral drug administration at the infusion center until medication could be obtained. This led to excess cost for UVA, burden on clinic staff, missed doses, and patient frustration. We sought to decrease the number of new alloSCT recipients discharged without appropriate prophylaxis in-hand from 21% to 10% by November 2024. Methods: Per the 2023 ASCO Quality Training Program associated with this project, a Model for Improvement and Plan Do Study Act (PDSA) methodology was utilized. The population included alloSCT patients with new prescriptions (Rxs) for posaconazole or isavuconazonium +/- letermovir. The outcome measure was percentage of newly discharged alloSCT patients requiring oral prophylaxis at the infusion center. The process measure was Time to Affordable Medication (TAM) defined as days from Rx prior-authorization (PA) request to paid claim with an affordable copay (defined as a copay the patient was able/willing to pay, including free drug approvals or assistance programs). The counter measure consisted of initiating the Rx PA process 10 days prior to planned admission via a discharge test Rx order set instead of waiting until admission. This standardized process allowed for clearer communication and more time for pharmacy technicians to process the Rx for PA, copays, free drug applications, and pharmacy logistics. Upon admission, the official Rx was released to the discharge pharmacy. If Rx shipment was required, this was set up the week prior to discharge. An I-chart (3-sigma) statistical process control (SPC) chart was used to assess the intervention. Results: The baseline TAM was assessed retrospectively in 22 Rxs over 3 months prior to intervention for a mean of 7.5 days. PDSA cycle 1 was implemented Nov. 2023. TAM for the first 35 Rxs was 4.3 days and the SPC upper control limit decreased from 26.3 days to 13.3 days demonstrating overall markedly decreased variation despite data from early 2024 having greater variability due to new insurance deductibles. Rxs requiring 10 or more days were due to free drug application processes. Importantly, no newly discharged alloSCT patients have required drug administration at the infusion center. Conclusions: PDSA #1 resulted in a decrease in TAM of 3.2 days, decreased variation in the process, and no patients discharged without drug in hand. Since we have already surpassed our aim, next steps include demonstrating sustainability of the process and a survey requesting feedback to identify balance measures.

Characterization of recurrent cytomegalovirus reactivations post allogenic stem cell transplantation in a population with high seropositivity

ObjectivesThis study aimed to characterize incidences of CMV reactivations within one year post-allo-SCT and identify risk factors for CMV second reactivation episode in population with high seropositivity where first CMV reactivation episode deemed to be high.MethodsThis retrospective cohort study analyzed data from 359 allo-SCT patients aged 14 and older admitted to a tertiary academic hospital. Data on demographic and clinical factors, CMV serostatus, conditioning regimens, graft-versus-host disease prophylaxis, engraftment time, and CMV reactivations were collected.ResultsFirst and second CMV reactivations occurred in 88.9% and 18.4% of post-allo-SCT patients respectively. Patients were stratified into two groups based on primary disease necessitating allo-SCT, patients with malignant (Group 1) and non-malignant (Group 2) hematological disease. Factors associated with the second reactivation included cord blood as a stem cell source, human leukocyte antigen mismatch, acute graft-versus-host disease, and hematological malignancies. Patients with non-malignant hematological disease displayed better outcomes, including a higher rate of spontaneous clearance of first CMV reactivation (70% versus 49.4%) and lower rates of second CMV reactivation (9.6% versus 31%) than those with malignant hematological disease. The one-year overall survival rate was 87.7% (95.5% in non-malignant hematological disease and 78.13% in malignant hematological disease).ConclusionOur findings are concordant with previous local study in regard to high rate of first CMV reactivation post-allo-SCT. It appears that patients with nonmalignant hematological disease had better outcomes, such as lower second CMV reactivation and higher survival rates compared to patients with malignant hematological disease. Further investigation is needed to identify other factors affecting recurrent CMV reactivations in allo-SCT in patients with malignant hematological disease.

Effect of pre-transplant functional status on length of hospital stay in patients undergoing allogeneic hematopoietic stem cell transplant in an outpatient transplant program.

6560 Background: The use of reduced intensity conditioning regimens including non-myeloablative regimens in allogeneic hematopoietic stem cell transplant (allo SCT), has expanded the pool of transplant candidates in the United States. Nonetheless, allo SCT, is associated with significant morbidity and mortality especially in patients 65 and older. In our outpatient transplant program, allo SCT patients undergo a comprehensive physical and occupational therapy (PT/OT) evaluation pre-transplant. Methods: We retrospectively reviewed all patients undergoing an allo SCT between January 2019 and December 2022 who had a PT/OT evaluation pre-transplant. We analyzed lower extremity functional scale (LEFS) and fatigue score (FACIT). The FACIT score is a patient reported outcome tool where the lower the score, the less fatigue impacts a patient’s performance. Results: We identified 218 patients who had at least one variable reported. Eighty-one patients were 65 years of age or older. All patients in the 65 and older group had a RIC or NMA conditioning regimen. In the 65 and older group, 72.8% had an HCTCI score of 3 or more compared to 59.1% in the group younger than 65. In patients younger than 65, those who had a lower LEFS (ie less lower extremity strength), had a statistically significant longer hospital stay of 15.5 days compared to 9 days (p=0.003). In patients 65 and older, lower FACIT scores (ie less patient reported fatigue), resulted in a statistically significant shorter hospital stay of 7.5 days compared to 13 days (p=0.019). In addition, there was a trend towards shorter hospital stays in patient 65 and older who had a higher LEFS of 5 days compared to 12.5 days (p=0.07). There was no difference in survival outcomes but there was a trend towards better overall survival in patients 65 and older with high LEFS (p=0.08) and a trend towards better NRM in this group (p=0.11). Conclusions: Our study highlights the need for comprehensive assessments in patients undergoing allo SCT. Geriatric functional status assessments are necessary to determine patients at risk for complications and to optimize such patients with exercise and cognitive rehabilitation programs prior to allo SCT. [Table: see text]

Frameshift Mutations in Leukemia-Associated Genes Correlate With Superior Outcomes in Patients Undergoing Allogeneic Stem Cell Transplant for De Novo Acute Myeloid Leukemia.

Allogeneic stem cell transplant (allo-SCT) is a mainstay of treatment for acute myeloid leukemia (AML). Its success depends largely on response of donor T lymphocytes against leukemia cells, known as graft-vs-leukemia (GvL) effect. A key potential driver of GvL is immune response to mutation-derived neoantigens. Previous studies in solid tumors have demonstrated enhanced immunogenicity of frameshift (FS)-derived peptides vs. those from non-synonymous single nucleotide variants (SNVs). We therefore hypothesized that AML cases bearing FS mutations in leukemia-associated genes would be more immunogenic than those with only other types of mutations (non-FS), and thus benefit more from allo-SCT via more robust GvL. We identified AML patients who had undergone allo-SCT between 2010 and 2022 and had next-generation sequencing data available on diagnostic specimens using a 42-gene hot spot panel. We compared the impact of tumor mutations present at diagnosis on overall survival and relapse-free survival based on FS versus non-FS status. Ninety-five AML allo-SCT patients were identified. We observed superior relapse-free survival (P = 0.038, hazard ratio (HR): 0.24) and borderline superior overall survival (P = 0.058, HR: 0.55) post-transplant in de novo AML patients, who had at least one FS mutation (other than NPM1) in one of the 42 assessed genes versus those with only non-FS mutations. Our findings suggest that FS-mutated AML cases may benefit more from allo-SCT than those with only non-FS mutations, possibly due to increased generation of immunogenic neoepitopes. If validated in an expanded study, incorporation of somatic FS mutation status in AML could improve patient selection algorithms for bone marrow transplant and thereby lead to superior outcomes.

Checkpoint Inhibitors and Allo-SCT in Hodgkin Lymphoma: A Matter of Time - a Study By the SFGM-TC

Introduction: Allogeneic stem cell transplantation (allo-SCT) for patients with relapsed/refractory Hodgkin lymphoma (r/R HL) after autologous transplantation is now an established option. Many patients receive Check-Point Inhibitors (CPI) as relapse treatment. Nevertheless, concerns have been previously reported on higher risk of acute graft versus host disease (aGVHD) after CPI exposure, without any control group to elucidate risk factors. Methods: We conducted a multicentric retrospective case control study on behalf of the Francophone Society for Bone Marrow Transplantation and Cell Therapy to compare outcomes after allo-SCT for patients with r/R HL who were exposed or not exposed to CPI. Results: Between 2015 and 2018, 149 patients underwent allo-SCT for r/R HL in 21 centers. CPI was used for 50 patients (n=48 Nivolumab, n=2 Pembrolizumab). We did not identify any differences regarding baseline characteristics. Reduced intensity conditioning (RIC) was commonly used (90.2%), with Peripheral Blood Stem Cells (75.7%). A majority of patients had haploidentical (44.6%), followed by siblings (28.4%), matched unrelated (24.3%) and mismatched unrelated donors (2.7%). Cumulative incidence (CI) of aGVHD grade ≥II in the whole cohort was 39.6% and 14.8% developed a severe form (grade III-IV). There were no differences between CPI (n=50) and no CPI cohorts (n=99), regarding CI of aGVHD of any grade (respectively 58% and 57.6%, p=1.00), grade ≥II (respectively 36% and 41.4%, p=0.65), severe aGVHD (grade III-IV, respectively 12% and 16.2%, p=0.67) and chronic GVHD (respectively 26% and 34.3%, p=0.24), as described in Table 1. We did not observe excess of mortality from GVHD between both groups. The time interval between the last CPI injection and allo-SCT was found to be the only significant factor associated with a higher incidence and severity of aGVHD, as depicted in Figure 1. The median time from the last CPI injection and allo-SCT was 50 days [33;103]. Specifically, within 30 days, the incidence of severe aGVHD was significantly increased at 41.7% compared to only 2.7% in the control group (p=0.002). No severe forms were observed after 60 days, but it persisted a higher risk of aGVHD grade ≥II even after 60 days of delay. Thus, a higher percentage of patients required systemic therapy for aGVHD within 120 days compared to after 120 days (45% vs 0% respectively, p=0.03). The delay of CPI treatment did not impact the CI and severity of chronic GVHD or CI of relapse after allo-SCT. Of note, post-transplant cyclophosphamide did not reduce CI of aGVHD. With a median follow-up of 34.7 months, the 2-year Overall Survival, Relapse Free Survival and GVHD free, Relapse Free Survival (GRFS) were respectively 69.9% (IC95 41.1-78.5), 67.1% (IC95 58.8-76.7) and 48.5% (IC95 40.3-58.4), without differences between CPI and no CPI cohorts. Two-year non relapse mortality was 17.4% in whole cohort, without hepatic sinusoidal obstruction syndrome nor steroid-requiring febrile syndrome in CPI cohort. Conclusion: CPI use before allo-SCT within 60 days before allo-SCT can lead to significant severe aGVHD, with persisting higher risk of aGVHD grade ≥II even after 60 days of delay. This highlights the importance of exercising caution when administering CPI injections within 60 days before allo-SCT. There is need to develop GVHD prophylaxis strategies in this population at risk. The findings from this study may help inform clinical decision-making and management of HL patients undergoing allo-SCT.

A Propensity Score-Matched Analysis on the Outcomes of Brexucabtagene Autoleucel from Zuma-2 Study and Allogeneic Stem Cell Transplantation from the EBMT Database in Relapsed and Refractory Post-Btki Mantle Cell Lymphoma

Introduction Brexucabtagene autoleucel (brexu-cel), an autologous anti-CD19 CAR T-cell therapy, is approved in the US for the treatment of relapsed/refractory (r/r) mantle cell lymphoma (MCL) and in Europe for r/r MCL after ≥2 prior lines of therapies, including Bruton's tyrosine kinase inhibitor (BTKi). The pivotal ZUMA-2 trial demonstrated very good efficacy of brexu-cel in r/r MCL and tolerable safety including cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome (Wang et al. J Clin Oncol. 2022). Allogeneic stem cell transplantation (alloSCT) is potentially curative but is associated with high treatment related mortality (TRM) and clinically significant graft-versus-host disease (GvHD). The optimal choice of treatment between brexu-cel and alloHCTs is unclear. We conducted a propensity score matched (PSM) analysis of brexu-cel and alloSCT in patients (pts) with r/r MCL. Methods Pts from ZUMA-2 were matched with alloSCT pts from the EBMT database. Selection criteria to identify pts in the EBMT registry were: r/r MCL diagnosis and receipt of alloSCT from 2010 to 2020, age ≥18 years, prior treatment with anti-CD20, prior anthracycline- or bendamustine containing regimens, and prior BTKi. We performed a 1:1 nearest neighbor matching without replacement, balanced for 5 baseline parameters: age, sex, number of prior treatment lines, time from diagnosis to cellular immunotherapy, and prior autologous stem cell transplantation (autoSCT). The primary endpoint was overall survival (OS) from cellular immunotherapy. The following secondary endpoints were analyzed: progression-free survival (PFS), TRM, defined as incidence of deaths which are related to the treatment and occurred in absence of disease progression, and rate of GvHD. Competing risks were defined as relapse, progression or treatment-unrelated death for TRM, and death for GvHD. The EBMT registry includes pts who actually underwent alloSCT. To characterize the dropout rate prior to cellular therapy, we conducted a multicenter intent-to-treat (ITT) analysis and identified 77 pts with r/r MCL for whom an unrelated donor search was initiated and an alloSCT was intended. Results Sixty-four of 68 pts from the ZUMA-2 cohort were included in the study; 4 pts were excluded because of inability to anonymize. A total of 270 pts who had undergone alloSCT and met eligibility criteria were identified in the EBMT registry. Patient characteristics between the brexu-cel and the alloSCT cohorts were imbalanced. Brexu-cel pts were older (p<0.001), had more prior lines of treatment (median 3 vs 2, p<0.001), had less prior autoSCT (41% vs 71%, p<0.001), and had longer time between diagnosis and treatment (53 vs 40 months, p=0.01). After 1:1 PSM matching, criteria were well balanced between cohorts. Median follow-up time was 36.5 and 46.4 months for the brexu-cel and the matched alloSCT cohort, respectively. PFS and long-term OS were similar between both cohorts (Fig. 1A). However, the risk of death within the first 12 months was significantly lower in the brexu-cel cohort vs the alloSCT cohort (logistic regression with inverse probability of censoring weighting, risk ratio=0.5, 95% confidence interval [CI] 0.3-0.9, p=0.02). This was mainly attributable to the significantly higher TRM rate in the alloSCT cohort (alloSCT vs brexu-cel: cause specific hazard ratio=7.7, 95% CI 1.9-31.6, p=0.005, Fig. 1B). The cumulative incidence of acute GvHD grade ≥3 at 3 months and chronic GvHD at 24 months was 17.9% (95% CI 9.1-29.0%) and 44.3% (95% CI 30.6-57.2%), respectively. In our ITT analysis, the dropout rate was significantly higher in the cohort intended to receive alloHCT (23%, [18/77]) vs the cohort intended to receive brexu-cel (8% [6/74]; Fisher test, p=0.01). For alloSCT, failure to proceed to cellular therapy was related to progression in 13%, change of patient's preference in 5% and ineligibility in 4%; in the brexu-cel cohort this was due to manufacturing failures in 4% and progression in 3%. Conclusion Brexu-cel is an effective treatment in pts with r/r MCL post-BTKi with a superior safety profile compared with alloSCT, as indicated by lower 12-month mortality, lower TRM, and absence of chronic GVHD-related morbidity. Despite efforts to match pts between the cohorts, the inherent limitations of this study, such as incongruent data sources and case selection bias, have to be considered. Additional analyses will be presented.

Monocyte Subpopulations and Their Expression of HLA-DR and CD300e after Allogeneic Stem Cell Transplantation in Patients with or without GvHD

Introduction: Graft versus host disease (GvHD) is a complex immune process that can affect up to 50% of patients undergoing allogeneic stem cell transplantation (allo-SCT). Even though prophylactic immunosuppressive regimens have been established over the last decades, GvHD is still one of the main causes of morbidity and mortality among these patients. Monocytes are cells of the innate immune system, that represent, as professional antigen-presenting cells, a connection to the adaptive immune system, and play a role in several autoimmune disorders. They are classified according to the expression of CD14 and CD16 into classical (CD14++/CD16-), intermediate (CD14++/CD16+), and non-classical (CD14+/CD16++) monocytes. Previous research has shown higher levels of intermediate monocytes in pediatric patients with GvHD. Furthermore, non-classical monocytes in allogenic bone marrow grafts have also been correlated with the development of GvHD. The expression of other surface markers such as HLA-DR and CD300e (IREM-2) are related to monocyte function and engagement in inflammatory processes. Nevertheless, the role of CD300e in GvHD remains unclear. Here, we present a description of monocyte subgroups and their expression of HLA-DR and CD300e in allo-SCT patients with or without GvHD as well as in healthy subjects. Methods: Transversal observational study with patients undergoing allo-SCT. Peripheral blood of patients was collected once after engraftment. Both acute and chronic GvHD patients were enrolled. Five healthy volunteers served as controls. Flow cytometry was performed to determine the immunophenotype of monocytes according to their expression of CD14 and CD16 stratifying into classical, intermediate, and non-classical subgroups as described above. In addition, the expression of HLA-DR and CD300e was analyzed for all monocytes and individual subgroups. Clinical characteristics are described in the table below. Statistical analysis was performed using GraphPad Prism 9. Comparisons between groups were made using non-parametrical tests and tests for multiple comparisons (Mann-Whitney and Kruskal-Wallis respectively). Results: 29 patients were enrolled. Two patients with GvHD were excluded due to neutropenia. 19 patients presented GvHD grade II or higher. Of those, ten had acute GvHD, five had prolonged acute GvHD, two had late onset acute GvHD, and two had chronic GvHD. Eight patients did not show GvHD or had only mild skin disease (grade one). The mean age was 60 years for all patients, 62.5 and 58.5 years among GvHD and non-GvDH patients, respectively. The image summarizes patient characteristics and comparisons. We compared transplant recipients with and without GvHD which each other and with healthy controls. In single comparisons, patients with GvHD showed significantly lower percentages of total monocytes as well as CD14+/HLA-DR+, total HLA-DR+, and intermediate monocytes compared to patients without GvHD. In addition, we observed a trend toward lower levels of CD16+/HLA-DR+ and CD300e-expressing monocytes in GvHD patients. When compared to healthy controls, allogeneic recipients without GvHD showed significantly higher levels of total monocytes, intermediate monocytes, and CD16+/HLA-DR+ monocytes and lower levels of classical and non-classical monocytes. Compared to controls, patients with GvHD showed significantly lower levels of total monocytes expressing CD300e (also true in all subgroups) as well as lower levels of classical monocytes, but higher levels of intermediate and non-classical monocytes. P values are shown in Table 1. Means and ranges for all groups are represented in Image 1. Conclusions: In our cohort, patients with GvHD showed higher levels of intermediate and non-classical monocytes compared to controls, however, these populations were lower when compared to allogeneic recipients without GvHD. This could indicate a consumption process similar to that observed in COVID-19 patients and a direct involvement of these monocytes in the GvHD process. In addition, we report for the first time the involvement of CD300e in GvHD, which was significantly lower expressed in the GvHD patients, compared to controls. However, there was only a strong trend compared to transplanted non-GvHD patients. This indicates a possible contribution of CD300e in the pathogenesis of GvHD. Further studies are needed in order to confirm these findings.

Multiparametric Flow Cytometry Based Quantification of the Marrow Hematopoietic Stem and Progenitor Compartment in Post Allogeneic Stem Cell Transplant Recipients with Poor Graft Function to Evaluate Hematopoietic Stem Cell Quality and Predict Clinical Outcomes: A Pilot Study

Poor graft function (PGF) is a poorly defined, commonly occurring (estimated 5 to 27%) 1 and difficult to treat complication of allogeneic stem cell transplantation (Allo-HSCT). Thrombopoietin agonists such as eltrombopag (EPAG) or CD34-selected cell infusions are treatments offered for persistent cytopenias. However, with limited knowledge of pathophysiology, there is a lack of reliable prognostic biomarkers. We aimed to investigate if assessment of the BM hematopoietic stem and progenitor cell (HSPC) landscape by multiparametric flow cytometry (MP-FCM) could help evaluate stem cell quality and predict clinical outcomes in PGF patients. We screened the UHN biobank repository to identify banked BM samples of patients who underwent diagnostic BM aspirate for PGF post allo-HSCT. Patients who had progressive cytopenia in one or more lineages after achieving engraftment while having full donor chimerism were included. Relapse as a cause of cytopenia was excluded. Controls in 1:1 ratio were Allo-SCT recipients with stable counts with banked day 60 BM aspirate. The blinded BM samples were analyzed with a 14-parameter FCM adapted from panels previously utilized to assess HSPC and mature lineages in cord blood xenograft studies (2). We selected 12 each of PGF and controls. The mean age of all recipients was 50 years and donors was 30.5 years. 23/24 cases had AlloSCT for hematological malignancies with 15 having AML or MDS. There were 14 unrelated (9 matched, 5 mismatched) and 10 related (5 matched sibling, 5 haploidentical) donors. Mean cell dose of infused graft was 6.66(± 1.98)x 10E6/kg CD34 cells. The significant difference between PGF and controls were recipient age (median 57y vs 28y), allo-SCT number (3 vs 0 with 2 nd transplant), intensity of conditioning regimen (myeloablative in 16% PGF vs 83% controls), and incidence of ≥ grade 3 acute graft vs host disease (GVHD) (n=3 vs 0). Most common causes of PGF were GVHD (n=6), infections (n=4) and drug effects (n=5). 11 PGF patients were treated with EPAG with 5 patients (A3, B2, B3, B5, C4) showing complete response, 3 (A6, B6, C5) showing partial response, and 3 (A2, A4, C9) showing no response. Patient C1 showed complete recovery without the use of EPAG, while C9, who initially did not respond to EPAG, showed a slow spontaneous recovery almost a year later. Amongst non-responders A2 and A4 received CD34 boost; with A4 showing a good response to the second boost. Analyzing the HSPC population by MP-FCM, we found that the PGF vs control groups show significant differences in the percentage of CD34+CD19+ B-Lymphoid precursors (B-LP) and CD19+ B lymphocytes. The mean ± SD percentage of B Lymphocytes and B-LPs in the PGF cohort were 6.76% ± 0.096% and 0.39% ± 0.005% respectively, while in the control group they were 20.09% ± 0.136% and 1.17% ± 0.012% respectively. When the 50 th centile value of the B-LPs (0.375%) or CD19+ B cells (10.89%) was investigated as a cut off to predict the clinical syndrome, this strategy achieved a 75% success rate with 3 PGF (blue bars) or control (black bars) samples misclassified (Fig1). Next, we investigated if these HSPC fractions could help predict the clinical outcome of PGF cases. The cases A2 and A4 who demonstrated no count recovery and needed CD34 boost lie in the lower quartile of both B Lymphocytes as well as B Lymphoid precursors content (Fig 1 red arrows). Conversely the three PGF cases in the upper 50 centile of these cell populations (patient B3, C4 and C9) all showed either a spontaneous or EPAG induced recovery of counts. We further investigated if the proportion of immunophenotypic CD34+CD38-CD45RA-CD90+CD49f+ long-term HSC (LT-HSC) could provide additional prognostic information (Fig2). Again, patients A2 and A4 had LT-HSC in the lower 50 th centile. Patient C1 who showed a spontaneous recovery of counts without the need of EPAG had the highest proportion of LT-HSCs despite lying in the second quartile of the cohort for both B cells as well as B-LPs. In conclusion, MP-FCM based analysis of the HSPC landscape in PGF marrow could be a robust prognostic biomarker in Allo-SCT patients.

Clofarabine and High-Dose Melphalan Reduced Intensity Conditioning Regimen with Methotrexate-Based GvHD Prophylaxis

Introduction: Reduced-intensity conditioning (RIC) allogeneic stem cell transplant (allo-SCT) remains a curative option for elderly and/or unfit patients with hematologic malignancies. Fludarabine-containing regimens make up the cornerstone of RIC regimens, however, during the nation-wide fludarabine shortage in 2022, many institutions used fludarabine-free RIC regimens out of necessity though data was extremely limited. Clofarabine is a second-generation purine analog with more potent anti-leukemic activity and a different adverse effect profile compared to fludarabine. We report our experience with clofarabine-based RIC conditioning for adult patients with non-Hodgkin's lymphoma (NHL) and myeloid malignancies. Methods: In this retrospective single-center matched cohort study at Stanford Health Care, we compared adult RIC allo-SCT patients receiving clofarabine and melphalan (CloMel) with a matched cohort receiving fludarabine and melphalan (FluMel) from January 1, 2022 to December 31, 2022. CloMel consisted of clofarabine 30 mg/m 2 on days -6 to -2 followed by melphalan 140 mg/m 2 on day -1, while FluMel consisted of fludarabine 30 mg/m 2 on days -5 to -2 followed by melphalan 140 mg/m 2 on day -1. Clofarabine dose adjustments were made in patients with renal dysfunction according to the following institutional guidelines based on creatinine clearance (CrCl): 22.5 mg/m 2 for CrCl 60 to 79 mL/min, 15 mg/m 2 for CrCl 30 to 59, and avoiding clofarabine for CrCl less than 30 mL/min. Dose modifications for fludarabine and melphalan due to renal dysfunction were at the discretion of the care team. Patients received graft versus host disease (GvHD) prophylaxis with tacrolimus and methotrexate. Efficacy and safety outcomes were assessed. Data were analyzed using Mann-Whitney U and chi-square tests. Results: We identified 9 matched pairs for a total of 18 patients. Most patients received an allo-SCT for a myeloid malignancy (8 patients with AML, 8 patients with MDS, and 2 patients with NHL). All patients received a peripheral blood stem cell transplant, with 89% receiving a matched unrelated donor and 11% receiving a matched related donor transplant. Baseline characteristics were balanced between groups. There was no difference in time to neutrophil engraftment (mean 14 vs 14 days; p=0.42), time to platelet engraftment (mean 16 vs 24 days; p=0.33), or 100% donor whole blood chimerism (71% vs 78%; p=0.32) at 6 months in the CloMel and FluMel groups, respectively. No statistically significant difference was observed for the number of patients who experienced acute (2 vs 0; p=0.13) and chronic GvHD (0 vs 4, p=0.09) at 6 months between groups. At 6 months, 2 patients in the CloMel group and no patients in the FluMel group experienced early non-relapse mortality (p=0.13). Both patients who died experienced acute renal failure secondary to conditioning chemotherapy with a median onset of renal dysfunction 6 days after initiation of clofarabine, followed by sepsis and multi-organ failure. Both patients required initiation of external renal replacement therapy and ultimately passed 12 days and 29 days post-transplant, prior to engraftment. Notably, both patients had a history of kidney dysfunction prior to transplant, one patient with chronic kidney disease (CKD) stage 3 and the other patient with lymphomatous involvement of the kidneys, and received appropriate clofarabine renal dose adjustments per institutional standards. Conclusion: CloMel demonstrated similar efficacy outcomes at 6 months and represents a feasible alternative to FluMel as a RIC regimen. However, given the notable occurrence of renal failure and early death in the CloMel arm, careful consideration and particular caution in administering to patients with a prior history of renal disease is recommended.

Role of Nutrition Support in Improving Outcomes in Allogeneic Stem Cell Transplant Patients

Introduction: Allogeneic hematopoietic stem cell transplant (Allo-SCT) can be associated with several complications related to the cytotoxic conditioning regimen, infections associated with immune suppression, and GVHD. Malnutrition amongst Allo-SCT patients has been reported to be an independent negative prognostic factor. It may be evident on presentation or develop as a sequela of decreased appetite, mucositis, and digestive GVHD. Whether supportive nutrition (enteral feeding or total parenteral nutrition (TPN)) contributes to favorable transplant outcomes is yet to be determined. Methods: We conducted a retrospective single-center study that evaluated patients who underwent Allo-SCT from Jan 2018 through Sept 2021. A chart review was conducted, and relevant data was collected. Primary outcomes were the impact of nutrition support (enteral feeding, TPN or both) among malnourished patients during the first 100 days post-transplant (T+100) on mortality and the composite outcome of acute GVHD incidence, infection rate, and days to engraftment. A higher composite score indicated worse outcomes. GVHD grading was based on the CIBMTR grading system (I-IV). The data was analyzed using Chi-Square and two-sample t-test. Results: A total of 70 Allo-SCT patients were identified. Of them, 42 (60%) were diagnosed with malnutrition, of which 23 (55%) received nutrition support. The mortality rate in patients who required nutrition support was significantly higher compared to those who did not receive nutrition support (83% (19/23) vs 11% (2/19)) with an odds ratio of 40 for this association (CI 6.5-248.9, p-value < 0.0001). The composite outcome was statistically higher amongst patients requiring nutrition support (mean 2.0, median score 1.8, SD 0.6) compared to those who did not need nutritional support (mean 1.6, median score 1.5, SD 0.4). These differences were found to be statistically significant using the Satterthwaite method (p-value 0.0218). Conclusion: Based on this data, we found that a reactive approach of nutrition support in the setting of malnutrition had no benefit on mortality and our pre-defined composite outcome during the first 100 days of allogeneic stem cell transplantation. This is fuel for conducting a prospective study using a preemptive enteral feeding approach to prevent the development of malnutrition and related complications.

Bacterial and Bacteriophage Consortia Are Associated with Protective Intestinal Immuno-Modulatory Metabolites in Allogeneic Stem Cell Transplantation Patients

The human microbiome is a predictor of clinical outcome in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-SCT). Besides bacteria, fungi and viruses as well as intestinal microbiota-derived metabolites are involved. However, it is still unclear how dynamic shifts in these three kingdoms contribute to the production of intestinal metabolites, how metabolites are impacted by graft-versus-host disease (GvHD) or antibiotics and whether they are associated with clinical outcome. We report the two-year follow-up of a prospective, observational, longitudinal cohort of allo-SCT patients (n=78) at two German transplantation centers that combined three-kingdom (bacteria, fungi, viruses) analysis of intestinal microbial communities with targeted metabolomics ( Figure 1). Using Multi-omics factor analysis (MOFA), we uncovered a functional microbiome signature of bacteria from the Lachnospiraceae and Oscillospiraceae families and their associated bacteriophages, which correlated with the production of immuno-modulatory metabolites (IMMs) including short-chain fatty acids (SCFAs), branched-chain fatty acids (BCFA), metabolites associated with induction of type-I IFN signaling (IIMs) and immuno-modulatory secondary bile acids ( Figure 2). We established an Immuno-modulatory Metabolite Risk Index (IMM-RI) consisting of five index IMMs, which was associated with improved survival, less transplant-related mortality and reduced relapse rate. Onset of gastrointestinal GvHD and exposure to antibiotics significantly impacted intestinal levels of protective IMMs. Using whole shotgun metagenomic sequencing, we observed that in IMM-RI low-risk patients, sustained production of protective IMMs was associated with a high abundance of microbial SCFA biosynthesis pathways, specifically butyric acid via butyryl-CoA:acetate CoA-transferase (BCoAT). Through genome assembly from viral metagenomic sequencing data, we detected two distinct bacteriophages which encoded BCoAT as an auxiliary metabolic gene. They were more abundant in IMM-RI low-risk patients and positively correlated with intestinal butyric acid levels, suggesting that these bacteriophages may modulate bacterial metabolite biosynthesis. Our study identifies a specific microbiome signature associated with protective IMMs that could improve fecal microbiota transplantation (FMT) donor selection and provides a rationale for the development of engineered metabolite-producing consortia and defined metabolite combination drugs as novel microbiome-based therapies for cancer patients.

Monitoring of strength, inflammation and muscle function in allogenic stem-cell transplantation patients - a pilot study for novel biomarker and risk stratification determination.

Low aerobic capacity is associated with an increased mortality risk in allogenic stem-cell transplantation (alloSCT) patients, but currently used risk scores in the pre-transplantation workup are still underestimating physical activity as a prognostic factor. To examine the physical condition, muscle function, blood inflammation and training adherence of alloSCT patients during inpatient time to identify potential biomarkers associated with development of myopathy and sarcopenia. Patients undergoing alloSCT were examined at four time points (T0: before alloSCT; Tha: hospital admission; T1: engraftment; T2: inpatient discharge). T0 included cardiopulmonary performance, body composition, grip and knee strength, motor skill tests (One-leg stand/Tinetti/Chair-rising), blood sampling (blood cell profiling and inflammation targets (Kynurenin/high sensitivity C-reactive Protein (hsCRP)/Tumor necrosis factor alpha (TNF-alpha)/Musclin/Galectin-3) and quality of life, state of health, fatigue, muscle weakness and physical activity by questionnaires (IPAQ/BSA/SARC-F/Fatigue). At T1 and T2, blood samples, grip strength and motor skill tests were repeated. Glucocorticoid dose and daily physical activity were documented during inpatient stay. 26 of 35 included patients (4 females; age 55.58 ± 12.32 years; BMI 24.70 ± 3.27 kg/m2; VO2peak 16.55 ± 4.06 ml/min/kg) could proceed to alloSCT. Grip strength and Tinetti decreased from T0 until T2, no difference in Chair-rising test, One-leg and Tandem stand. All patients engrafted after 24.9 days ± 3.9 days. HsCRP and Kynurenine increased from T0 to T1, decreased at T2. TNF-alpha (T0vsT2/T1vsT2) and Musclin (T0vsT1) decreased. At T2, Galectin-3 was higher compared to T0/T1. Correlation analysis of grip strength and inflammatory markers revealed a positive correlation with TNF-alpha at T2. 50% of patients documented physical activity and questionnaire and reported a 50%-reduction of daily endurance and strength training between T1 to T2. Allogeneic stem-cell transplantation is associated with immune system vulnerability due to conditioning, increased inflammation and fatigue, and loss of muscle strength and function. In addition to hsCRP, Kynurenine seems to be a reliable biomarker to monitor acute and regenerative inflammation status of alloSCT patients, while Musclin and Galectin-3 may be added to physiological assessment regarding myopathy and sarcopenia. Grip strength and daily activity level should be documented by professionals to identify risk patients early and support them with optimal (exercise) therapy.

Risk factors and characteristics influencing humoral response to COVID-19 vaccination in patients after allogeneic stem cell transplantation.

Vaccination against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is approved and recommended for immunocompromised patients such as patients after allogeneic stem cell transplantation (allo-SCT). Since infections represent a relevant cause of transplant related mortality we analyzed the advent of immunization to SARS-CoV-2 vaccination in a bicentric population of allogeneic transplanted patients. We retrospectively analyzed data of allo-SCT recipients in two German transplantation centers for safety and serologic response after two and three SARS-CoV-2 vaccinations. Patients received mRNA vaccines or vector-based vaccines. All patients were monitored for antibodies against SARS-CoV2-spike protein (anti-S-IgG) with an IgG ELISA assay or an EIA Assay after two and three doses of vaccination. A total of 243 allo-SCT patients underwent SARS-CoV-2 vaccination. The median age was 59 years (range 22-81). While 85% of patients received two doses of mRNA vaccines, 10% had vector-based vaccines and 5% received a mixed vaccination. The two vaccine doses were well tolerated with only 3% patients developing a reactivation of graft versus host disease (GvHD). Overall, 72% of patients showed a humoral response after two vaccinations. In the multivariate analysis age at time of allo-SCT (p=0.0065), ongoing immunosuppressive therapy (p= 0.029) and lack of immune reconstitution (CD4-T-cell counts <200/μl, p< 0.001) were associated with no response. Sex, intensity of conditioning and the use of ATG showed no influence on seroconversion. Finally, 44 out of 69 patients that did not respond after the second dose received a booster and 57% (25/44) showed a seroconversion. We showed in our bicentric allo-SCT patient cohort, that a humoral response could be achieve after the regular approved schedule, especially for those patients who underwent immune reconstitution and were free from immunosuppressive drugs. In over 50% of the initial non-responders after 2-dose vaccination, a seroconversion can be achieved by boostering with a third dose.

215b. Real-World Experience of Letermovir Use at an Academic Transplant Center

Abstract Background Letermovir (LMV) is indicated for cytomegalovirus (CMV) prophylaxis in seropositive adults after allogeneic hematopoietic stem cell transplants (alloSCT). LMV is well tolerated compared to its alternatives. Our institution restricts LMV use to high-risk patient groups to maximize the cost/benefit of LMV. Despite these restrictions, LMV was in our institution’s top 50 drug expenditures, prompting a formal evaluation of its use. We describe a real-world experience with LMV at a 576-bed academic transplant center. Methods This was a single center, retrospective, descriptive study of LMV use at a transplant center. Any hospitalized patient who received ≥ 1 dose of LMV between August 2021 and January 2022 was eligible for analysis. Data collection included age, LMV administration data, length of stay, transplant status, Infectious Diseases (ID) consultation, documented rationale for non-criteria uses, and drug cost. The primary outcome was incidence of use not aligning with restriction criteria. The secondary outcome was institutional drug expenditure for non-criteria uses compared to approved uses. Results Over 6 months, 388 doses of LMV were administered to 31 unique patients during 41 admissions. LMV use during 12/41 admissions (31.7%) fell outside the institutional criteria. ID consult occurred in 58.3% (7/12) of cases. 27/31 (87%) were alloSCT patients, including 1 pediatric patient. There was also 1 liver and 1 heart transplant recipient. Reasons for non-criteria use were: primary prophylaxis in the heart transplant patient to avoid ganciclovir toxicity and in 2 alloSCT patients without high risk for CMV, pre-emptive therapy due to CMV reactivation (n=2), and step-down therapy for CMV viremia (n=4). LMV was used for extended periods ( &amp;gt; 100 days from transplant) in 2 cases. Non-criteria use of LMV accounted for $20 414 in drug cost over 6 months, 29% of total expenditure. Conclusion Our data suggest real world use of LMV often differs from the patient types enrolled in the phase 3 trials. Use of LMV as an alternative to available CMV therapies to avoid drug toxicities appears to drive much of this use. In addition, use outside of criteria was frequent and incurred a nontrivial cost. Modification of our criteria, such as requiring an ID consultation for off-label use, should be considered. Disclosures James S. Lewis, PharmD, FIDSA, Cidara: Advisor/Consultant|Merck: Advisor/Consultant|SeLux Diagnostics: Advisor/Consultant.

Role of Autologous or Allogeneic Stem Cell Transplantation in Patients with Peripheral T Cell Lymphomas (PTCLs)

Background Peripheral T cell lymphomas (PTCLs) are heterogeneous group which present diverse clinical and molecular characteristics. Stem cell transplantation (SCT) has been known to improve survival outcomes. However, there are still no standard guidelines for choosing high-dose chemotherapy followed by autologous-SCT (auto-SCT) or allogeneic-SCT (allo-SCT) in patients with up-front or salvage setting. Methods We retrospectively analyzed data from 599 patients with PTCLs who underwent auto-SCT or allo-SCT over the past 10 years. Patients between 15 and 70 years were included in this study. Event-free survival (EFS) was determined from the date of SCT to the date of disease progression or death from any cause. Overall survival (OS) was determined from the date of SCT to the date of death or last follow-up. Results A total of 446 patients were analyzed, and the median age at the time of SCT was 49.6 (range, 15.2-69.7) years old. Histology subtypes were PTCL-NOS (n=184), NK/T lymphoma (n=89), angioimmunoblastic T lymphomas (AITL, n=79), anaplastic large cell lymphoma (ALCL, n=64), enteropathy-associated T cell lymphoma (EATL, n=15), and adult T cell leukemia/lymphoma (ATLL, n=15). Up-front SCT was conducted in 379 patients in which CR1 were 229 patients, PR1 were 89, and primary refractory were 61, respectively. As a part of front-line therapy, 302 patients received auto-SCT while 77 patients underwent allo-SCT. Auto-SCT showed significantly superior OS than allo-SCT in patients with CR1 or PR1 at the time of SCT (p=0.026). Survival outcomes in patients with primary refractory disease were also statistically superior in auto-SCT group (EFS, p=0.049; OS, p=0.018). In patients with CR≥2, PR≥2, patients who underwent salvage chemotherapy followed by auto-SCT reported better OS (p=0.011). However, in patients who underwent SCT in a relapsed state, allo-SCT group showed better survival tendency in terms of EFS (p=0.077) and OS (p=0.058). Majority cause of poor outcomes in allo-SCT group was treatment related mortality (TRM). In the allo-SCT group, total body irradiation (TBI) and CR or PR status at the time of SCT were identified as favorable factors in the multivariate analysis. Donor type and conditioning regimen were not affected the transplantation outcomes. Conclusion Auto-SCT was effected as a part of front-line therapy or as a part of salvage setting. Allo-SCT could be considered in relapsed state patients with TBI based conditioning regimen.

Expansion of Plasmablasts at Day 90 after Allogeneic Stem Cell Transplantation Predict Chronic Gvhd

Chronic GVHD (cGVHD) is characterized by a dysregulation of the adaptive immune system with an aberrant B cell homeostasis after allogeneic hematopoietic stem cell transplantation (allo-SCT). It is unclear, whether B cell dysregulation is solely a consequence of cGVHD or a predictive indicator of cGvHD development. Several studies have shown an increase in CD21low B cells in cGVHD patients. CD21low B cells are heterogeneous comprising three distinct B cell populations, CD10+CD38hi immature B cells, CD10- CD11c+ B cells expressing T-bet, and CD38hi CD27hi CD20- plasmablasts. To elucidate the development of B cell dysregulation before the manifestation of cGVHD a prospective multicenter study exploring B cell phenotype and frequencies starting at d56 after allo-SCT, was initiated, a time point when first B cells are detectable in peripheral blood. We included 172 allo-SCT patients and excluded patients with EBV reactivation >10,000 copies/ml, post-transplant treatment with rituximab. After completion of follow-up, study patients were assigned retrospectively with respect to onset of GVHD based on Glucksberg criteria for acute GVHD (aGVHD) and NIH consensus criteria 2014 for cGVHD. For GVHD grouping only patients with a follow-up of at least 180 days after allo-SCT were evaluated. Patients without any form of GVHD or with aGVHD alone at day 180 or day 365 required at least 3 months of follow-up to exclude subsequent onset of cGVHD. Thus, three groups were evaluated: 1) no GVHD (n=17), 2) acute GVHD without subsequent cGVHD (n=32) and 3) cGVHD with a median onset of 180 days after allo-SCT (n=59, maximum severity: mild n = 17, moderate n= 30, severe n = 12). Multiparameter flow cytometry of the three subpopulations of CD21low B cells revealed that already 56 days after allo-SCT the frequency of immature B cells was significantly elevated and remained increased until day 365 after allo-SCT in all patients, whereas CD11c+ B cells were significantly reduced at day 56 and raised subsequently until these cells were found expanded at day 180 and day 365. In contrast, plasmablasts showed a transient significant increased frequency 90 days and 180 days after allo-SCT. The frequency of plasmablasts was significantly elevated already 90 days after allo-SCT in patients developing subsequent cGVHD, as compared to patients without GVHD or aGVHD patients (median 5.9% vs 2.2% vs 2.2% of CD19+ cells; p=0.0016 and p=0.0304, respectively). The proportion of CD11c+ B cells in patients with cGVHD increased later in the course of time but was not significantly different between cGVHD patients at d+365 and patients without GVHD or aGVHD patients (median 4.4% vs 2.2% vs 4.0% of CD19+ cells, respectively). Frequencies of immature B cells did not correlate with the occurrence of aGVHD or cGvHD at any time point. Multivariate analysis with clinical transplant parameters revealed that elevated frequencies of plasmablasts (>3% of CD19+) at 90 days after allo-SCT are an independent risk factor for subsequent cGVHD in a Cox proportional hazards model excluding HLA-matching as covariable (hazard ratio, 4.08; 95% CI, 1.4 to 11.86). To obtain insight into the origin of plasmablast expansions we performed single-cell B cell receptor (BCR) sequencing of plasmablasts (n=5) from cGVHD patients. These analyses revealed prominent clonal expansions, a high frequency of somatic mutations, a low Shannon index of the BCR repertoire and overrepresentation of certain selected VHgenes. Most plasmablasts were found class switched to IgG and even more frequently to IgA. Recombinant expression of plasmablast-derived IgA antibodies revealed recognition of bacterial antigens in most cases of expanded clones. Regarding IgG antibodies analysis of sera from four cGvHD patients on protein arrays covering more than 7,000 human proteins established binding of a hitherto unknown spectrum of multiple autoantigens including RNA-binding proteins overlapping between patients. In summary, our prospective study demonstrates an early oligoclonal expansion of hypermutated plasmablasts already 90d after allo-SCT in patients subsequently developing cGvHD, in a manner similar to systemic autoimmune diseases. Our findings strongly suggest an antigen-driven process induced by auto- or allo-antigens and indicate a pathogenic contribution of plasmablasts to cGvHD development.

The Potential of E-Health in Patients after Allogeneic Stem Cell Transplantation

Introduction Modern information and communication technologies (ICT) have become increasingly important in daily life as well as in patient-physician interaction, health monitoring and health related information (E-Health). Progress in allogeneic stem cell transplantation (allo-SCT) has led to improved survival and increasing numbers of patients. However, with a multitude of potential complications, follow-up of allo-SCT patients remains complex requiring close monitoring, support and treatment with a plethora of medical fields involved. Early studies have shown that E-Health can benefit caretaking of these patients. So far, only little information is known about the patients’ current use of E-Health and their perspective on its potential. Yet, this knowledge is of particular importance for re-structurization of follow-up after allo-SCT including the standardized use of E-Health and its comprehensive acceptance. This multicenter study aims to close this knowledge gap by investigating the patients’ view towards E-Health and use of telemedicine after allo-SCT. The results will help to facilitate the implementation of E-Health in standard follow-up after allo-SCT and other cellular therapies with a focus on patients’ perspective. Methods and Results Between May 2021 and June 2022, 237 patients after allo-SCT were asked to answer a structured questionnaire at the university hospitals Aachen, Bonn, Cologne and Duesseldorf (Center for Integrated Oncology, CIO ABCD) in Germany. Overall, 219 patients returned the questionnaire leading to a response rate of 92%. Of these, 34% were female and 66% were male with a median age of 59 years (range 18-81). In our patient cohort, the current distribution of internet-enabled computers/smartphones is over 90% and the electronic devices are mainly used for daily life activities. Nevertheless, the use of ICT in medical monitoring and patient-physician interaction is still limited. Only a minority of patients have digitized medication plans, use digital monitoring of health data/fitness-apps or own wearables for health monitoring such as smartwatches. In contrast, the majority of patients favors additional online patient-physician interaction such as scheduling and transmission of medical reports and 65% of the patients support real-time transmission of health data through wearables to the physician for a limited time period. Of note, 40-50% of patients have concerns regarding data safety, even more when using messenger services (67%). The majority of patients considers online chats or video calls with their physician to be beneficial and expects an improvement of the treatment quality through increased use of E-Health. Additionally, most patients favor local treatment with online correspondence between their local practitioner and a specialized center, especially if the patients are present during the online communication or with intermittent personal patient contact to the center. Subgroup analyses revealed that in most areas there is no gender difference in use and perspective on E-Health. However, male patients consider online chats more beneficial and expect an improved patient-physician interaction through increased use of ICT compared to females. Age and educational attainment are very significant factors in patients’ view on E-Health. Younger (<60 years) as well as higher educated patients favor increased use of online communication, applications and devices in almost all regards and expect benefits of patient-physician interaction and treatment quality, which is in significant contrast to the views of older or less educated patients. Hometown size or distance to a specialized center does not show a relevant impact on the view on E-Health. This is also true for time after allo-SCT or frequency of outpatient visits at the time of questioning. Conclusions Dissemination of internet-enabled devices is wide and the potential of E-Health is high in patients after allo-SCT. The majority of patients favors further standardized implementation of E-Health technologies and telemedically supported caretaking post allo-SCT and potentially other cellular therapies to improve patient-physician interaction and cross-sectoral care. Future research should focus on patients’ needs in the context of data safety and exchange of medical information in interdisciplinary care processes to successfully integrate new E-Health technologies.

Immunomodulatory Microbial Metabolites Identified in Allo-SCT Patients Protect from GvHD By Sting Dependent Modulation of Intestinal Tissue Homeostasis

Background: Graft-versus-host disease (GVHD) is a dreaded complication after allogeneic stem-cell transplantation (ASCT). Previously, we and others showed that activation of type I interferon (IFN-I) inducing pathways such as RIG-I/MAVS or cGAS/STING can promote the integrity of the intestinal barrier and limit GVHD. However, the signals that drive these protective IFN-I responses are poorly understood. Commensal microbiota can (i) have distant effects on immune responses through modulation of IFN-I signaling and (ii) predict mortality in ASCT patients. We hypothesized that microbiota-derived products such as microbial metabolites engage IFN-I signaling in immune and non-immune cells poising them for induction of protective responses. We established a prospective, multi-centric clinical study in patients newly diagnosed with acute leukemia and performed longitudinal stool sampling to track changes in microbial community composition and metabolites expression levels (Submitted as a separate abstract to ASH 2022 (Orberg & Meedt et al.)). We showed that patients with high metabolite expression are less likely to develop GVHD. In this study, we translated our clinical observations to mouse models of acute GVHD and human and mouse intestinal organoid models to uncover the molecular mechanisms of protective metabolites during ASCT. Methods: Stool samples from ASCT patients were obtained in Munich and Regensburg in accordance to IRB-approved study protocols. Patients were sampled at initial diagnosis (Dx), prior to conditioning and weekly after ASCT up to day 28. We analyzed samples by 16S rRNA sequencing and mass spectrometry. Next, we tested metabolites detected in patients in vitro in murine and human intestinal crypt-derived organoids and organoid/T cell coculture assays. To obtain a mechanistic understanding, we stimulated WT or IFN-I-signaling-impaired organoids or used small molecule inhibitors and analysed them regarding growth performance, cell composition and by scRNAseq. Finally, Metabolites were applied as treatment in preclinical intestinal damage models and GVHD mouse models. Outcomes were assessed by a novel organoid recovery assay in addition to established read-outs. Results: Here, we present expression profiles of metabolites including short-chain fatty acids, DAT, ICA and secondary bile acids. Following ASCT, and especially at the early time-points, metabolite expression declined drastically. We confirmed this trend in our multi-centric cohort of ASCT patients by comparing levels of DAT and ICA sampled at admission to the transplantation ward (Conditioning) versus at clinical diagnosis of GVHD: in patients with GVHD, metabolite levels were drastically reduced. Metabolite stimulation of mouse small intestinal organoids promoted organoid growth and required intact STING signaling. Additionally, organoids showed an increased stemness and resistance to T cell mediated damage. Both healthy donor and GvHD patient derived human colon organoids also responded to DAT and ICA, however the metabolite effect was lost when co-administered with the STING-inhibitor H151. Next, we prophylactically administered metabolites in a major mismatch mouse ASCT model. Metabolite-treated mice showed significantly better outcomes in barrier integrity and organoid based intestinal regeneration assays. Additionally, metabolite treatment was associated with an increased regulatory T cell infiltration. These effects were abrogated in STING-/- recipients, but not in IFNaR-/- recipients. Finally, metabolite treatment was protective in major mismatch GVHD mouse models. Conclusions: We identify that microbial-derived metabolites detected in patients can engage the STING pathway in humans and mice to confer resistance from immune damage. Thus, prophylactic administration of metabolite cocktails or bacterial consortia may reduce occurrence of GVHD in ASCT patients.

Statin-based endothelial prophylaxis and outcome after allogeneic stem cell transplantation.

Allogeneic haematopoietic stem cell transplantation (alloSCT) often remains the only curative therapy for hematologic malignancies. Although the management of transplant-associated adverse events considerably improved over the last decades, nonrelapse mortality (NRM) remains a challenge, and endothelial dysfunction was identified as a major contributor to NRM. Statin-based endothelial prophylaxis (SEP) has been implemented in the standard of care in our transplant centre to reduce NRM caused by endothelial injury. Here, we retrospectively analysed the impact of SEP on clinical outcome in a cohort of 347 alloSCT patients. SEP (n=209) was associated with significantly reduced NRM (hazard ratio 0.61, 95% CI 0.38-0.96) and better overall survival (OS) after acute graft-versus-host disease (HR 0.59, 95% CI 0.37-0.93). Subgroup analyses showed that the NRM benefit was mainly found in patients with an intermediate endothelial activation and stress index (EASIX), while relapse risk was not affected. On day 100 post-alloSCT, patients receiving SEP had significantly higher levels of the rate-limiting enzyme of tryptophan metabolism, indoleamine 2,3-dioxygenase (IDO), higher kynurenine to tryptophan ratios as a proxy of IDO activity and tended to have lower levels of the endothelial injury marker ST2 (p=.055). No significant differences in interferon-gamma or IL18 levels were observed. These biomarker signatures suggest that the beneficial effects of SEP might be mediated by both endothelial protection and immunomodulation. Together, these data suggest that SEP improves NRM and OS post-alloSCT in particular in patients with intermediate endothelial risk and provide first mechanistic clues about its potential mode of action.

Durable Engraftment and Excellent Overall Survival After CD34-Selected Peripheral Blood Stem Cell Boost in Pediatric Patients With Poor Graft Function Following Allogeneic Stem Cell Transplantation

Poor graft function (PGF) is a life-threatening complication after allogeneic stem cell transplantation (alloSCT). Historically, outcomes of patients with PGF have been very poor, and there are no standardized approaches to treatment. Furthermore, few outcomes after CD34-selected stem cell boost (CD34+SCB) for PGF in pediatric alloSCT recipients have been reported. Here we report on a single center experience with CD34+SCB for PGF after alloSCT in patients treated on the Pediatric Transplant and Cellular Therapy Service at MSK Kids, Memorial Sloan Kettering Cancer Center. A retrospective analysis of patients transplanted for malignant and nonmalignant disorders who received a CD34+SCB between 2008 to 2020 for treatment of PGF defined as the need for granulocyte colony-stimulating factor (G-CSF) and/or packed red blood cell or platelet transfusion support with bone marrow donor chimerism ≥85%. Peripheral blood stem cells from the original donor were the source for CD34+SCB. Durable complete recovery (durable CR) was defined as recovery of peripheral blood counts without recurrent need for G-CSF or transfusion support. The main outcomes of interest were recovery of hematopoiesis and overall survival. Development of graft versus host disease (GVHD) was an additional outcome of interest. Fourteen patients with PGF received a boost. Six patients had no known infection, while 8 patients had PGF associated with an infection. The probability of CR at 60 days was 79% (95% confidence interval [CI], 57%-100%). The overall survival at both 2 and 5 years was 78% (95% CI, 56%-100%). One patient developed GVHD, which was fatal. No other CD34+SCB-related toxicities were observed. While including patients with PGF as recently defined by the American Society for Transplantation and Cellular Therapy, as well as PGF in patients with concomitant infections, we demonstrate that CD34+SCB is safe and can provide for durable trilineage hematopoietic recovery and long-term survival in pediatric patients after alloSCT.