Severe Chronic Graft-versus-host Disease Research Articles

Graft Versus Host Disease Prophylaxis in Matched Donor Stem Cell Transplantation: Post-transplantation Cyclophosphamide Combinations Versus Methotrexate/Tacrolimus

BackgroundThe use of post-transplant cyclophosphamide (PTCy) is highly effective in preventing graft versus host disease (GVHD) for haploidentical allogeneic hematopoietic stem cell transplantation (allo-HSCT). There is limited data on the role of PTCy as GVHD prophylaxis in matched-sibling and fully matched-unrelated donor (MSD/MUD) allo-HSCT. MethodsOur single-center retrospective study aims to compare outcomes of PTCy alone or in combination with mycophenolate mofetil and tacrolimus (PTCy/MMF/TAC) relative to methotrexate and tacrolimus (MTX/TAC). The primary endpoint of our study was GVHD-free, relapse free survival (GRFS). Secondary endpoints were overall survival (OS), disease free survival (DFS), and incidence of severe acute and chronic GVHD. We identified 74 adult patients who underwent MSD/MUD allo-HSCT at our institution from 2015 to 2023. ResultsWithin our cohort, 33.8% (n = 25) received MTX/TAC, while 54.0% (n = 40) received PTCy/MMF/TAC, and 12.2% (n = 9) received PTCy alone. Patients receiving PTCY had the longest time to neutrophil engraftment relative to MTX/TAC (15 days vs. 12 days, P = .010). PTCy/MMF/TAC was associated with improved GRFS relative to MTX/TAC (hazard ratio [HR] = HR 0.42, 95% CI 0.19-0.93, P = .031), which persisted when controlling for age. Incidence of chronic GVHD was lower in the PTCy/MMF/TAC group compared to MTX/TAC (1-year 9.0% vs. 30.1%, HR 0.19, 95% CI 0.06-0.59, P = .005). However, OS and DFS were comparable across all groups. ConclusionsOur results demonstrate decreased rates of severe chronic GVHD resulting in improved GRFS when using PTCy/TAC/MTX as GVHD prophylaxis compared to MTX/TAC in MSD/MUD.

Total Body Irradiation and Fludarabine with Post-Transplantation Cyclophosphamide for Mismatched Related or Unrelated Donor Hematopoietic Cell Transplantation

Allogeneic hematopoietic cell transplantation (HCT) remains the sole curative treatment for most patients with hematologic malignancies. A well-matched donor (related or unrelated) remains the preferred donor for patients undergoing allogeneic HCT; however, a large number of patients rely on alternative donor choices of mismatched related (haploidentical) or unrelated donors to access HCT. In this retrospective study, we investigated outcomes of patients who underwent mismatched donor (related or unrelated) HCT with a radiation-based myeloablative conditioning MAC regimen in combination with fludarabine, and post-transplantation cyclophosphamide (PTCy) as higher-intensity graft-versus-host disease (GVHD) prophylaxis. We retrospectively assessed HCT outcomes in 155 patients who underwent mismatched donor HCT (related/haploidentical versus unrelated [MMUD]) with fractionated-total body irradiation (fTBI) plus fludarabine and PTCy as GVHD prophylaxis at City of Hope from 2015 to 2021. Diagnoses included acute lymphoblastic leukemia (46.5%), acute myelogenous leukemia (36.1%), and myelodysplastic syndrome (6.5%). The median age at HCT was 38 years, and 126 patients (81.3%) were an ethnic minority. The Hematopoietic Stem Cell Transplantation Comorbidity Index was ≥3 in 36.1% of the patients, and 29% had a Disease Risk Index (DRI) of high/very high. The donor type was haploidentical in 67.1% of cases and MMUD in 32.9%. At 2 years post-HCT, disease-free survival (DFS) was 75.4% and overall survival (OS) was 80.6% for all subjects. Donor type did not impact OS (hazard ratio [HR], .72; 95% confidence interval [CI], .35 to 1.49; P = .37) and DFS (HR, .78; 95% CI, .41 to 1.48; P = .44), but younger donors was associated with less grade III-IV acute GVHD (HR, 6.60; 95% CI, 1.80 to 24.19; P = .004) and less moderate or severe chronic GVHD (HR, 3.53; 95% CI, 1.70 to 7.34; P < .001), with a trend toward better survival (P = .099). The use of an MMUD was associated with significantly faster neutrophil recovery (median, 15 days versus 16 days; P = .014) and platelet recovery (median, 18 days versus 24 days; P = .029); however, there was no difference in GVHD outcomes between the haploidentical donor and MMUD groups. Nonrelapse mortality (HR, .86; 95% CI, .34 to 2.20; P = .76) and relapse risk (HR, .78; 95% CI, .33 to 1.85; P = .57) were comparable in the 2 groups. Patient age <40 years and low-intermediate DRI showed a DFS benefit (P = .004 and .029, respectively). High or very high DRI was the only predictor of increased relapse (HR, 2.89; 95% CI, 1.32 to 6.34; P = .008). In conclusion, fludarabine/fTBI with PTCy was well-tolerated in mismatched donor HCT, regardless of donor relationship to the patient, provided promising results, and increased access to HCT for patients without a matched donor, especially patients from ethnic minorities and patients of mixed race.

Associations between acute and chronic graft-versus-host disease

AbstractChronic graft-versus-host disease (GVHD) is 1 of the major complications after allogeneic hematopoietic cell transplantation (allo-HCT). Although various risk factors for chronic GVHD have been reported, limited data are available regarding the impact of acute GVHD on chronic GVHD. We examined the association between acute and chronic GVHD using a Japanese registry data set. The landmark point was set at day 100 after allo-HCT, and patients who died or relapsed before the landmark point were excluded. In total, 14 618 and 6135 patients who underwent allo-HCT with bone marrow or peripheral blood (BM/PB) and with umbilical cord blood (UCB), respectively, were analyzed. In the BM/PB cohort, the risk for chronic GVHD that requires systemic steroids increased with each increase in acute GVHD grade from 0 to 2 (grade 0 vs 1 [hazard ratio (HR), 1.32; 95% confidence interval (CI), 1.19-1.46; P < .001]; grade 1 vs 2 [HR, 1.41; 95% CI, 1.28-1.56; P < .001]), but the risk was similar between acute GVHD grade 2 and grade 3 to 4 (HR, 1.02; 95% CI, 0.91-1.15; P = 1.0). These findings were confirmed in the UCB cohort. We further observed that the risk for severe chronic GVHD increased with each increment in the grade of acute GVHD, even between acute GVHD grade 2 and grade 3 to (grade 2 vs 3-4: HR, 1.70; 95% CI, 1.12-2.58; P = .025). In conclusion, the preceding profiles of acute GVHD should help to stratify the risk for chronic GVHD and its severity, which might be useful for the development of risk-adopted preemptive strategies for chronic GVHD.

Vascular biomarkers reveal a unique toxicity profile of posttransplant cyclophosphamide: secondary analysis of BMT CTN 0402 and 1202

AbstractPosttransplant cyclophosphamide (PTCy)–based graft-versus-host disease (GVHD) prophylaxis regimens are associated with very low rates of severe acute and chronic GVHD after hematopoietic cell transplant (HCT). However, concerns about cardiac and other organ toxicities persist. This study aimed to compare the vascular biomarker profile of PTCy with other GVHD regimens, including tacrolimus/sirolimus (Tac/Sir) and tacrolimus/methotrexate (Tac/MTX), to generate hypotheses for toxicity mitigation strategies. Plasma samples from day +28 after transplant were analyzed against pretransplant baseline measurements in patients receiving PTCy-based GVHD prophylaxis as part of Blood and Marrow Transplant Clinical Trials Network (BMT CTN) 1202 (n = 112) vs Tac/MTX (n = 98) and Tac/Sir (n = 95) regimens from BMT CTN 0402. Compared with Tac/MTX, PTCy was associated with increasing angiopoietin-2 levels and decreasing epidermal growth factor levels at day +28. In contrast, Tac/Sir displayed increasing follistatin and endoglin levels and decreasing vascular endothelial growth factor receptor 2 (VEGFR2) plasma levels after HCT. Across all cohorts, increasing epidermal growth factor was protective from nonrelapse mortality, and decreasing VEGFR2 was associated with subsequent development of extensive chronic GVHD. These distinct biomarker profiles offer insights that could guide strategies to mitigate unique GVHD prophylaxis–associated toxicities.

Alteration of Gut Microbiota Composition and Diversity in Acute and/or Chronic Graft-versus-Host Disease Following Hematopoietic Stem Cell Transplantation: A Prospective Cohort Study.

Changes in gut microbiome composition have been implicated in the pathogenesis of graft-versus-host disease (GvHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Our objective was to explore the microbial abundance in patients with GvHD after allo-HSCT. We conducted a single-center, prospective study in patients who underwent allo-HSCT and developed grade II or higher acute GvHD and/or moderate or severe chronic GvHD, to explore the microbial abundance of taxa at the phylum, family, genus, and species level, and we utilized alpha and beta diversity indices to further describe our findings. We collected fecal specimens at -2 to +2 (T1), +11 to +17 (T2), +25 to +30 (T3), +90 (T4), and +180 (T5) days to assess changes in gut microbiota, with day 0 being the day of allo-HSCT. We included 20 allo-HSCT recipients in the study. Compared with timepoint T1, at timepoint T4 we found a significant decrease in the abundance of Proteobacteria phylum (14.22% at T1 vs. 4.07% at T4, p = 0.01) and Enterobacteriaceae family (13.3% at T1 vs. <0.05% at T4, p < 0.05), as well as a significant increase in Enterococcus species (0.1% at T1 vs. 12.8% at T4, p < 0.05) in patients who developed acute GvHD. Regarding patients who developed chronic GvHD after allo-HSCT, there was a significant reduction in the abundance of Eurobactereaceae family (1.32% at T1 vs. 0.53% at T4, p < 0.05) and Roseruria genus (3.97% at T1 vs. 0.09% at T4, p < 0.05) at T4 compared with T1. Alpha and beta diversity analyses did not reveal a difference in the abundance of bacteria at the genus level in GvHD patients at T4 compared with T1. Our study reinforces results from previous studies regarding changes in gut microbiota in patients with acute GvHD and provides new data regarding the gut microbiome changes in chronic GvHD. Future studies will need to incorporate clinical parameters in their analyses to establish their association with specific changes in gut microbiota in patients with GvHD after allo-HSCT.

Anti-T-lymphocyte globulin improves GvHD-free and relapse-free survival in myelofibrosis after matched related or unrelated donor transplantation

Acute and chronic graft-versus-host disease (GvHD) are major complications of allogeneic hematopoietic cell transplantation (alloHCT). In vivo T-cell depletion with anti-T-lymphocyte globulin (ATLG) as part of the conditioning regimen prior to alloHCT is frequently used as GvHD prophylaxis, but data on its role in myelofibrosis is scarce. We took advantage of an international collaborative network to investigate the impact of ATLG in myelofibrosis undergoing first alloHCT. We included 707 patients (n = 469 ATLG and n = 238 non-ATLG prophylaxis). The cumulative incidence of acute GvHD grade II-IV was 30% for the ATLG group vs. 56% for the non-ATLG group (P < 0.001). Acute GvHD grade III-IV occurred in 20% vs. 25%, respectively (P = 0.01). Incidence of mild-to-severe chronic GvHD was 49% vs. 50% (P = 0.52), while ATLG showed significantly lower rates of severe chronic GvHD (7% vs. 18%; P = 0.04). GvHD-free and relapse-free survival (GRFS) at 6 years was 45% for the ATLG group vs. 37% for the non-ATLG group (P = 0.02), driven by significantly improved GRFS of ATLG in matched related and matched unrelated donors. No significant differences in risk for relapse, non-relapse mortality, and overall survival were observed. Multivariable modeling for GRFS showed a 48% reduced risk of GvHD, relapse, or death when using ATLG.

Neurologic Complications of the Central Nervous System after Allogeneic Stem Cell Transplantation: The Role of Transplantation-Associated Thrombotic Microangiopathy as a Potential Underreported Cause

Neurologic complications (NCs), especially those of the central nervous system (CNS), represent a severe complication after allogeneic stem cell transplantation (allo-HSCT) and are associated with relevant morbidity and mortality. We aimed to characterize the potential risk factors for the development of CNS-NC, with a special focus on the role of calcineurin inhibitors (CNIs) as a predisposing factor. For this purpose, we compared cyclosporin A (CsA) versus tacrolimus (TAC) with respect to their influence on the incidence and type of CNS-NC after allo-HSCT. We retrospectively analyzed the incidence, risk factors, and impact on outcomes of CNS-NC diagnosed during the post-transplantation follow-up in patients with different high-risk hematologic malignancies who underwent allo-HSCT at our institution over a 20-year period. All patients included in the analysis received CNI (CsA or TAC) as graft-versus-host disease (GVHD) prophylaxis. We evaluated a total of 739 consecutive patients who underwent transplantation between December 1999 and April 2019. During a median follow-up of 6.8 years, we observed a CNS-NC incidence of 17%. The development of CNS-NC was associated with decreased overall survival (OS) and increased transplantation-related mortality (TRM). The most frequent CNS-NCs were infections (30%) and neurologic adverse events related to the administration of CNI, TAC, or CsA as GVHD prophylaxis (42%). In the multivariable analysis, age, total body irradiation (TBI), and severe acute GVHD and chronic GVHD were significant risk factors in the development of CNS-NCs. TAC compared with CsA emerged as an independent predisposing factor for CNS-NCs. The TAC-associated risk of CNS-NCs was related mostly to the occurrence of transplantation-associated thrombotic microangiopathy (TA-TMA) with neurologic manifestations (neuro-TA-TMA), although the general TA-TMA incidence was comparable in the 2 CNI subgroups. CNS-NCs are associated with poor prognosis after allo-HSCT, with TAC emerging as a potential yet insufficiently characterized predisposing factor.

Evaluation of differences in quality of life in patients with chronic graft-versus-host disease

Objective: To evaluate the status of, differences in, and factors influencing quality of life (QoL) in patients with chronic graft-versus-host disease (GVHD). Methods: From September 2021 to February 2023, a cross-sectional study of 140 patients with chronic GVHD was conducted at our center. Symptom burden was assessed by the Lee Symptomatology Scale (LSS), and QoL was assessed by the Medical Outcome Study 36-Item Short-Form Health Survey (SF-36) (version 1) and five-level EuroQoL five-dimensional questionnaire (EQ-5D-5L). Results: Data from 140 respondents, including 32 (22.9%) with mild chronic GVHD, 87 (62.1%) with moderate chronic GVHD, and 21 (15.0%) with severe chronic GVHD, were analyzed. Of the respondents, 61.4% were male, and the median transplantation age was 34 (15-68) years. The primary diagnoses were acute myeloid leukemia (50.0%), acute lymphoblastic leukemia (20.0%), and myelodysplastic syndrome (15.0%). The common chronic GVHD-affected organs included the skin in 74 patients (52.9%), the eyes in 57 patients (40.7%), and the liver in 50 patients (35.7%). Among the whole cohort, the eye (20.48±23.75), psychological (16.13±17.00), and oral (13.66±20.55) scores were highest in the LSS group. The physiological function (36.07±11.13), social function (36.10±10.68), and role-emotional functioning (38.36±11.88) scores were lowest in the SF-36 group. The EQ-5D index was 0.764. The total LSS scores for mild, moderate, and severe chronic GVHD were 6.51±6.15, 10.07±5.61, and 20.90±10.09, respectively. The SF-36 physical component scores (PCSs) were 43.12±6.38, 40.73±7.14, and 36.97±6.97, respectively, and the mental component scores (MCSs) were 43.00±8.47, 38.90±9.52, and 28.96±9.63, respectively. The EQ-5D values were 0.810±0.124, 0.762±0.179, and 0.702±0.198, respectively. The multivariate analysis showed that the overall symptom burden (β=-0.517), oral symptom burden (β=-0.456), National Institute of Health (NIH) criteria for the eyes (β=-0.376), and nutrition-related symptom burden (β=-0.211) were significantly negatively correlated with the PCS. The NIH score (β=-0.260) was negatively correlated with the MCS score. Oral symptom burden (β=-0.400), joint/fascia NIH criteria (β=-0.332), number of involved systems (β=-0.253), overall NIH criteria (β=-0.205), and number of immunosuppressants taken (β=-0.171) were significantly negatively correlated with the EQ-5D score (all P<0.05). Medium to strong correlations were found between the EQ-5D score and the SF-36 score (|r|=0.384-0.571, P<0.001). Conclusions: The QoL of patients with chronic GVHD is impaired, and the more severe the disease, the poorer the QoL. Overall symptom burden, severity of eyes, and oral symptom burden were the most important factors affecting QoL.

Severity and organ distribution of chronic graft-versus-host disease with posttransplant cyclophosphamide-based versus methotrexate/calcineurin inhibitor-based allogeneic hematopoietic cell transplantation.

The reduced risk of chronic graft-versus-host-disease (GVHD) with posttransplant cyclophosphamide (ptCy) in the setting of haploidentical related donor and more recently, with HLA-matched related and matched and mismatched unrelated donor allogeneic transplantation has been established. There is, however, paucity of data to show if ptCy impacts chronic GVHD pathogenesis, its phenotype and evolution after HCT regardless of the donor status. We examined the differences in chronic GVHD incidence and presentation in 314 consecutive patients after receiving their first allogeneic transplantation (HCT) using ptCy-based GVHD prophylaxis (ptCy-HCT; n = 120; including 95 with haploidentical related donor) versus conventional calcineurin inhibitor-based prophylaxis (CNI-MUD; n = 194) between 2012 and 2019. The 1-year cumulative incidence of all-grade chronic GVHD and moderate/severe chronic GVHD was 24% and 12%, respectively, after ptCy-HCT and 40% and 23% in the CNI-MUD recipients (p = 0.0003 and 0.007). Multivariable analysis confirmed that use of CNI-based GVHD prophylaxis and peripheral blood stem cell graft as the risk factors for chronic GVHD. The cumulative incidence of visceral (involving ≥1 of the following organs: liver, lungs, gastrointestinal tract, serous membranes) chronic GVHD was significantly higher with CNI-MUD vs. ptCy-HCT (27% vs. 15% at 1 year, p = 0.009). The incidence of moderate/severe visceral chronic GVHD was 20% in CNI-MUD group vs. 7.7% in the ptCy-HCT group at 1 year (p = 0.002). In addition, significantly fewer ptCy-HCT recipients developed severe chronic GVHD in ≥3 organs (0.8%) vs. 8.8% in the CNI-MUD group at 1-year posttransplant (p = 0.004). There was no significant different in relapse, non-relapse mortality, and relapse-free and overall survival between the two groups. Further investigation is needed to confirm that reduced risk and severity of chronic GVHD, less visceral organ distribution with ptCy-HCT leads to improved quality of life.

Outcome of Multiple Myeloma Patients Undergoing Allogeneic Stem Cell Transplant with Post-Transplant Cyclophosphamide - a Single Center Experience

Objective: The survival of multiple myeloma (MM) patients has improved significantly in the past decade with the development of new effective treatments including immunomodulators, monoclonal antibodies, and chimeric antigen receptor T cell (CAR-T) therapy. However, to date, none of the available treatments is curative for MM. In high-risk and relapsed patients, allogeneic stem cell transplant (allo-SCT) achieved long term survival in carefully selected MM patients. Here, we report our experience in MM patients who received allo-SCT at Thomas Jefferson University Hospital (TJUH). We aim to define the role of allo-SCT in the new era of MM treatment. Method: We retrospectively analyzed data of 57 MM patients who received allo-SCT at TJUH from 1996-2023. We used EZR software to analyze post-transplant outcomes including overall survival (OS) and disease-free survival (DFS) with Kaplan Meier method. Cumulative incidence (CI) calculated by EZR was used to determine relapse rate (RR) and non-relapse mortality (NRM). Median time to neutrophil and platelet engraftment was analyzed by Excel 2022. Results: The median age was 53 years old (range from 34-68 years old); 29 females and 28 males. Mean follow up time was 57.9 months (range from 0 to 253.6 months). Thirty-two patients received reduced intensity conditioning, 11 patients received myeloablative conditioning regimen, and 5 patients received non-myeloablative conditioning regimens. Thirty-one patients received matched related donor (MRD), 3 patients received matched unrelated donor (MUD), 21 patients received haploidentical (HI), and 2 patients received mismatched unrelated donor stem cell grafts. Time to neutrophil and platelet engraftment data was available for 33 and 29 patients, respectively. The median time to neutrophil engraftment was 12 days (range from 3-23 days). and the median time to platelet engraftment was 16 days (range from 6-51days). The 3-year and 5-year probabilities of OS were 53.2% (95% confidence interval is 38.7% to 65.7%) and 48.3% (95% confidence interval is 33.9% to 61.3%) respectively. The 3-year and 5-year probability of DFS were 37% (95% confidence interval is 21.6% to 52.5%) and 26.2% (95% confidence interval is 12.6% to 42%) respectively. Since 2009, most of the patients (33/36) in this study received post-transplant cyclophosphamide. Thus, we compared the OS for patients who received allo-SCT before 2009 and after 2009. The 5-years OS was 28.6% (95% confidence interval is 7.8% to 42.5%) and 62.7% (95% confidence interval is 43% to 77.2%) for patients who received allo-SCT before 2009 and after 2009 respectively (P=0.029). Among 43 patients with available relapse date data, the CI of relapse at 3 years was 36.9% (95% confidence interval 21.5%-52.4%) and the CI of NRM at 3 years was 26.1% (95% confidence interval 14%-39.9%). Thirty-five patients were evaluable for acute graft versus host disease (GVHD). Nine patients developed grade I-IV acute GVHD (25.7%) and 2 patients experienced grade III-IV acute GVHD (5.7%). Four out of 35 evaluable patients experienced chronic GVHD (11.4%): 2 patients had mild to moderate scleroderma, one patient had severe chronic skin GVHD and one had severe lung chronic GVHD. For 36 patients received allo-SCT after 2009, 3 died from relapse, 3 patients died from infection, 2 died from GVHD, 2 from unknown cause, one from brain bleeding, one from non-infectious pulmonary failure and one from acute heart failure. Conclusion: In MM patients with high-risk feature or relapsed/refractory disease, allo-SCT can be curative for approximately a third of the patients. Post-transplant cyclophosphamide coupled with contemporaneous MM treatments significantly increased the survival of allo-SCT MM patients in the modern era.

A Prospective Randomized Clinical Trial Comparing a Calcineurin-Free Gvhd Prophylaxis Regimen with Post-Transplant Cyclophosphamide and Abatacept to Methotrexate and Tacrolimus

Background: Chronic Graft Versus Host Disease (GVHD) is one of the major causes of mortality and morbidity after an allogeneic stem cell transplantation. We hypothesized that we could induce post-transplant tolerance by using the combination of post-transplant cyclophosphamide (PTCy) and abatacept (CTLA4Ig) for GVHD prophylaxis. PTCy can eliminate most host-reactive donor T cells. Abatacept (CTLA4Ig) blocks the costimulatory signals given to naïve T cells during immune reconstitution, thus favoring an anergic phenotype and promoting tolerance towards recipient derived antigens. CTLA4Ig gives an activating signal to NK cells and has therefore the ability to preserve the graft-versus-tumor effect. Methods: We conducted a prospective randomized clinical trial. Patients with hematologic malignancies in need of an allogeneic transplant and with an 8/8 matched related or unrelated donor were randomized 1:1 to tacrolimus and methotrexate for GVHD prophylaxis (SOC arm) or PTCy on days +3 and +4 followed by abatacept on an extended schedule: days +5, +14,+28, +56, +84, +112, +140 and +168 (Aba arm). Patients were stratified by conditioning regimen (myeloablative vs reduced intensity) and donor type (matched sibling vs matched unrelated donor). They received peripherally collected stem cells. The primary endpoint was moderate and severe chronic GVHD at 1 year and the secondary endpoints overall chronic GVHD, Grade II-IV and III-IV acute GVHD rate, overall (OS), disease-free (DFS), and GVHD-relapse-free-survival (GRFS) at on year, transplant related mortality and infection rate. The study stopped enrolling on the SOC arm when abatacept was approved for GVHD prophylaxis and the institutional SOC changed to include abatacept. Results: 40 patients were treated on this study, 25 of which on the aba arm. There were two cases of secondary graft failure (one on each arm) that were excluded from further analysis other than OS. The trial met its primary end point: Kaplan-Meier estimates of moderate/severe cGVHD were 0% on the aba and 65.8% on the SOC arm (p &amp;lt; 0.0001). GRFS was 58.3% in the aba and 21.4% in the SOC arm (p=0.043). There were no treatment related deaths on the aba and two on the SOC arm. There was no statistically significant difference in the rates of OS (92% aba, 80% SOC, p=0.28), DFS (62.5% aba, 85.7% SOC, p=0.103) and infection. Grade III-IV acute GVHD rate was 4.1% on the aba and 20% on the SOC arm (p=0.132), whereas Grade II-IV 12.5% on aba and 35.7% on SOC (p=0.117). There were no cases of acute GVHD of the gut or liver on the aba arm. Overall chronic GVHD rate (including mild) was 9.1% on the aba and 74% on the SOC arm (p&amp;lt;0.0001). Conclusions: The calcineurin inhibitor-free combination of PTCy and abatacept for GVHD prophylaxis is feasible, well tolerated and associated with a very low rate of chronic GVHD and a favorable GRFS rate.

TBI-Containing with T-Cell Replete Full Haplotype Mismatched Hematopoietic Stem Cell Transplantation in Adult Patients with De Novo Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is the 2nd most frequent developing hematologic malignancy with deep heterogeneity, but unfortunately the majority of patients relapse even after allogeneic hematopoietic stem cell transplantation (HSCT) in complete remission (CR). We have developed allogeneic HSCT from familial mismatched/haploidentical donors (FMT) in adult patients with a single disease entity of AML lacking of both HLA-identical siblings and well-matched unrelated donors (WMUD) from the mid 1990s. Previously, several pilot studies of FMT performed with various total body irradiation (TBI)-based conditioning regimens (2~12 gray) with or without post-transplant cyclophosphamide (PT-Cy) as a graft-versus-host disease (GvHD) prophylaxis were reported. Here, we demonstrate about the encouraging outcomes of FMT using unmanipulated peripheral blood donor stem cells (PBSCs) and de-escalated dose of TBI (4~8 gray) containing conditioning regimen without T-cell depletion manner. Although PT-Cy as a specific GvHD prophylaxis regimen is increasingly used for both adult and pediatric FMT, our group investigated the clinical outcomes in adult patients with de novo AML who received full haplotype mismatched HSCT after TBI containing preparation regimen consisted of fractionated TBI (total 4 gray for elderly and 8 gray for &amp;lt;60 years old), fludarabine (150 mg/m 2/day), busulfex (6.4mg/kg/day), and anti-thymocyte globulin (ATG). For GvHD prophylaxis, rabbit ATG (thymoglobulin, Genzyme, 1.25mg/kg/day for 4 days at D-4 to D-1) and a combination of tacrolimus and short-term methotrexate was used. G-CSF mobilized unmanipulated PBSCs were used with a median CD34+ dose of 6.5 x 10 6/kg (1~25.6). From 2008 to the end of 2022, total 429 adult patients were enrolled, and data demonstrated that our trial of intermediate-dose of ATG and reduced toxicity of TBI-containing conditioning regimen to reduce graft-failure even for high levels of donor-specific antibody titer, early transplant-related mortality, critical cytomegalovirus (CMV) disease, and emerging post-transplant lymphoproliferative disease with rapid immune recovery has shown very successful outcomes. Briefly, the median absolute neutrophil count recovery was 12 days (10~26) and the platelet of 14 days (5~38). There was no either primary or secondary graft-failures at all. With a median follow-up of 36.5 months (2~242) for survivors, overall survival rate (OS) and relapse-free survival (RFS) for patients in any CR (n=338) and relapse/refractory status (n=91) were 62.9% vs. 34.3% and 59.5% vs. 32.2%, respectively. Although there was no significant difference in the subgroup analysis, de novo and young aged patients in any CR showed the best OS 73% (Figure 1). Cumulative incidences of acute GvHD and chronic GvHD were 66% (59-73), 70% (63-76), respectively. The incidences of moderate to severe acute GvHD and chronic GvHD were 16.1%, 30.5%, respectively. By univariate and multivariate analyses, patient's age &amp;lt;54 (p=0.043), pre-HSCT CR1 (p &amp;lt;0.001), absence of mod to severe chronic GvHD (p &amp;lt;0.001), and use of post-transplant iron-chelating agent (p=0.001) were the statistically significant in the study. The GvHD-free and relapse-free survival rate in CR1 was 62.4% for younger patients (age &amp;lt;54) and 47.9% for older patients (p=ns). The non-relapse mortality rate was 27.2% for all enrolled patients and 16% for CR patients. The rapidity of immune recovery was also compared with our old control cohort when we performed T-cell depletion using the CliniMACS system, and it showed a significant reconstitution of CD4+ cells (&amp;gt;300/ul) at 3 months post-FMT compared to the much delayed T-cell depleted FMT. Of note, CMV DNAemia was relatively higher (76.9%) than reported in other studies, likely due to the use of ATG and the endemic region of our country. Therefore, we suggest that the strategic reduction of fractionated TBI 4~8 gray-based conditioning with unmanipulated PBSCs graft without PT-Cy seems feasible with favorable outcomes for adult patients with de novo AML undergoing FMT in CR, especially even in a certain subgroup of elderly patients with AML.

UM171 Expanded Cord Blood Transplantation Outcomes Compare Favorably to All Different Stem Cell Sources: An EBMT Registry Case-Control Analysis

Background: Cord blood (CB) transplantation (CBT) has several advantages compared with other graft sources, such as permissive human leucocyte antigen (HLA) mismatches, and low risk of chronic graft-versus-host disease (GVHD) and relapse. However, CBT has fallen into disfavor because of its high risk of non-relapse mortality (NRM) and prolonged hospitalization due to its low cell dose. Furthermore, the need for the rare large cord bloods (CBs) leads to selection of poorly HLA-matched CBs, known to further increase NRM. UM171 is a small molecule that expands hematopoietic stem cells. A phase I-II study of a single UM171-expanded, myeloablative and reduced intensity CBT for patients with high-risk hematologic malignancies who lacked a donor, demonstrated prompt neutrophil engraftment, the ability to use smaller, better HLA-matched CBs, and a low NRM of 5% (Cohen S et al. Lancet Haematol 2020). The aim of the current analysis was to compare outcomes after a UM171 CBT to real-world cohorts of 6 other stem cell sources identified in the European Society for Blood and Marrow Transplantation (EBMT) registry. Methods: This is a retrospective study comparing 22 adults who received a single UM171-expanded CBT in the phase I-II study between 2016-2018, to 6 cohorts of patients allografted from different stem cell sources and reported to the EBMT registry. Control patients were eligible if they had received a myeloablative or reduced intensity allogeneic transplant for a hematologic malignancy in Europe during 2010-2021, were between the ages of 18-65 years, and had a Karnofsky performance status (KPS) score ≥70. The different donor control cohorts were: 1) CB, single or double units, with a calcineurin inhibitor (CNI) and mycophenolate mofetil (MMF) for GVHD prophylaxis, 2) 10/10 HLA-matched unrelated donor (MUD) peripheral blood stem cells (PBSC) with a CNI and MMF or methotrexate (MTX), 3) 10/10 MUD bone marrow (BM) with a CNI and MMF or MTX, 4) 9/10 HLA-MUD BM or PBSC (9/10 UD), 5) T cell replete haploidentical donor (haplo) BM or PBSC, and 6) matched sibling donor (MSD) BM or PBSC. Exclusion criteria included in vitro manipulated grafts and CBT recipients who received anti-thymocyte globulin or alemtuzumab. Patients were directly matched for disease and status at transplant and propensity score matching was used for prior allograft, age, KPS, and conditioning regimen. Endpoints included engraftment, GVHD, NRM, relapse, progression-free survival (PFS), overall survival (OS), and GVHD-free relapse-free survival (GRFS). The EBMT attempted to identify 3 controls for each patient. If no control was identified for a UM171 patient, the latter was excluded from the analysis. Results: Between 17 and 21 UM171 CB patients were compared to 36 to 62 controls depending on the donor group as 1-3 controls could not be identified for each patient (Table 1). Median follow-up for the UM171 group was 36 months and generally longer for the controls. Neutrophil engraftment with UM171 CB was similar to all donor groups except slower for CB and MUD BM. Platelet engraftment was consistently slower for UM171 CB except when compared to conventional CB. The incidence of severe acute GVHD was similar across all donor groups. As there was no severe chronic GVHD in the UM171 group, the latter was associated with less extensive/severe chronic GVHD compared to MUD (PBSC and BM) and MSD. There was a trend towards lower NRM for UM171 CB compared to haplo and 9/10 UD but it did not reach statistical significance. PFS, OS and GRFS were all better with UM171 CB compared to haplo. Finally, GRFS was improved with UM171 CB when compared to MUD PBSC (Figue 1), 9/10 UD, and MSD. Conclusions: This registry matched case-control analysis demonstrated real-word evidence suggesting UM171-expanded CBT recipients have improved outcomes compared to other donor types. More specifically and due to the absence of severe chronic GVHD with UM171 CB, GRFS was better with UM171 CB when compared to other graft sources except for CB and MUD BM. Also, OS and PFS were superior with UM171 CB compared to haplo donors. Limitations of this study included the small number of UM171 patients, the inability to identify controls for each case, and certain missing data for the controls. UM171 expansion of CB appeared to achieve the desired outcome of maintaining benefits of CB while removing its disadvantages. Thus, prospective randomized studies are warranted to confirm these results.

A Pilot Study of Reduced Intensity HLA-Haploidentical Hematopoietic Cell Transplantation (HaploHCT) with Post-Transplant Cyclophosphamide in Patients with Advanced Myelofibrosis

Allogeneic hematopoietic cell transplantation (HCT) is the only curative option for patients with myelofibrosis (MF); however, a significant obstacle to proceed to HCT is availability a matched donor, especially since MF is most often diagnosed in older adults. The effective development of haploidentical transplant (haploHCT), with post-transplant cyclophosphamide (PTCy) as graft-versus-host disease (GVHD) prophylaxis, has been a major therapeutic advance for patients without an available matched donor. Based on the excellent survival rates seen in older patients with myeloid malignancies using fludarabine/Melphalan-based (Flu/Mel) regimen with PTCy GVHD prophylaxis, we designed a pilot trial (NCT03118492) to evaluate safety and tolerability of reduced intensity condition (RIC) regimen of Flu/Mel and TBI (2Gy) for peripheral blood stem cells (PBSC) HaploHCT with PTCy in patients with advanced MF (Figure 1a). At the time of this report, we have enrolled 17 patients (out of 22) in two cohorts. After treating the first 4 patients in cohort 1 (CH-1), eligibility was updated to exclude accelerated disease, severe pulmonary hypertension, with stricter fluid management for a stricter monitoring and eligibility criteria (cohort 2; CH-2). Our primary objective was to determine safety of this regimen in patients with MF. Key secondary endpoints were grade 2-4 acute GVHD, chronic GVHD, engraftment, overall survival (OS), progression-free survival (PFS), non-relapse mortality (NRM), and relapse. Detailed patient/HCT characteristics are listed in Table 1. Briefly, median age at the time of HCT was 59 years (range: 48-70), and 53% of patients were male. MF diagnosis was primary MF in 53% of patients, and 71% had intermediate-2 risk level. Karnofsky performance status was 80-100 in 94.1% of patients and HCT comorbidity index was 0-2 in 82.4%. Median time from MF diagnosis to HCT was 935 days (range: 27-7651). In CH-1, unacceptable toxicity (UT) was defined as any of the following considered at least possibility related to PTCy: any death; grade 3-4 adverse events (AEs) that does not improve to grade ≤2 within 4 weeks except for hematologic toxicities. For hematologic toxicities, UTs were primary graft failure. Two out of the 4 patients in CH-1 experienced UTs. [UPN1: grade 3 anorexia that did not improve to grade ≤2 within 4 weeks; UPN4: grade 3 kidney injury (per Bearman Scale), and grade 4 neutropenia lasting more than 42 days]. Since &amp;gt;1/6 patients had UTs, per protocol monitoring rules and after a full IRB review, the definition of UT was updated to the following in CH-2: any regimen-related grade 3-4 toxicity per Bearman scale, or for hematologic toxicities, per NCI CTCAE v4.03 toxicity scale, any grade 4 neutropenia associated with fever or infection and lasting for more than 21 days, or grade 4 neutropenia lasting for more than 42 days, or death. In CH-2, one out of 16 patients experienced a UT of acute kidney injury. UPN17 has not reached the 100-day UT period, at the time of this report. One-year OS, PFS and NRM for all patients were 80% (95%CI: 39-95), 68% (95%CI: 30-89) and 21% (95%CI: 3-50), respectively. All patients engrafted (n=12), with the median time to neutrophils engraftment of 19 days (range: 13-23) for CH-1 and 16 days (range: 12-22) for the CH-2. One-year OS for CH-2 was 91% compared to 50% in CH1 and was reduced to 78% and 50% at 2 years, respectively. RFS in CH-2 was 91% at 1 year, and 62% at 2 years compared to 50% in CH-1 at both time points. Relapse was not seen at 1 and 2 years in CH-1, whereas in CH-2 there were no relapses at 1-year but 15% of patients relapsed by the end of year 2. NRM at 100-days was 25% in CH1 vs non in CH-2 and at 2 years-NRM were 50% and 22% in CH-1 and CH-2, respectively. Grade 3-4 GVHD was not seen in either cohort. Similarly moderate and severe chronic GVHD was not seen in either cohort at 1 or 2 years. One and 2 years GRFS was 81 and 61% respectively. In conclusion, early results of this pilot study indicate that HaploHCT in MF patients undergoing HCT is safe and feasible, with low NRM and higher grade acute and chronic GVHD. We are currently accruing in CH2. If successful, this approach can be tested in a multi-center setting as a phase II trial, and likely extend this potentially curative procedure to most patients of minority populations in the United States and to a significant proportion of the Caucasian population without an HLA matched.

Relapse Incidence Post Unrelated Allogeneic Stem Cell Transplantation with Post-Transplant Cyclophosphamide (PTCy) Versus Conventional Anti-Graft Versus Host Disease Prophylaxis in Patients with Acute Myeloid Leukemia: A Study on Behalf of the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation

Background: Recently, the BMT CTN 1703 phase III study compared post-transplant cyclophosphamide with tacrolimus with mycophenolate mofetil (PTCy/TAC/MMF) to TAC /methotrexate (MTX) as graft- versus-host disease (GVHD) prophylaxis post allogeneic transplantation (HSCT), demonstrating a lower incidence of severe acute (a) GVHD and chronic (c) GVHD and better GVHD-free, relapse-free survival (GRFS). The control arm did not include anti-thymocyte globulin (ATG), used in many centers for GVHD prophylaxis. Methods: The study aim was to compare PTCy with TAC or cyclosporine A (CSA) and MMF (PTCy/TAC or CSA &amp; MMF) to ATG combined with TAC and MTX (ATG/TAC/MTX) in acute myeloid leukemia (AML) patients (pts) undergoing HSCT from matched siblings (MSD) or 9-10/10 unrelated donor (UD) in first complete remission (CR1). Statistical tests included a multivariate analysis (MVA) adjusting for potential confounding factors using a Cox proportional-hazards regression model for main outcomes. Results: 6050 pts met the inclusion criteria, 402 received PTCy/TAC or CSA &amp; MMF and 5648 received ATG/TAC/MTX as GVHD prophylaxis. Median follow-up was 23.4 (IQR, 20.3-24.9) and 41.8 (IQR, 39.6-43.3) months (p&amp;lt;0.0001). The median year of the transplant was 2018 (2010-2020) and 2016 (2007-2020) (p&amp;lt;0.0001). Pts in the PTCy/TAC or CSA &amp; MMF group were younger, with a median age of 48.7 (range 18-5.6) versus 51.5 (8-77.8) years (p=0.024). The diagnosis was de novo AML in 84.1% vs 85.3% and secondary (s) AML in 15.9% vs. 14.7% (p=0.49). The cytogenetic risk was categorized as intermediate (70.9% vs. 67.1%), adverse (22.2% vs. 25.7 %), and favorable (6.9% vs. 7.2%) for pts in the PTCy/TAC or CSA &amp; MMF and ATG/TAC/MTX groups, respectively (p=0.35) (data missing for 2214 pts). Karnofsky performance status (KPS) did not differ between the groups. There was a higher frequency of pt cytomegalovirus (CMV) seropositivity and female (F) donor to male (M) pt combination in the PTCy/TAC or CSA &amp; MMF versus the ATG/TAC/MTX groups, 77.8% vs. 71.8% (p=0.009) and 18.4% vs. 14.4% (p=0.029), respectively. More pts in the PTCy/TAC or CSA &amp; MMF group received reduced intensity conditioning (RIC) 51.5% versus 41.1% in the ATG/TAC/MMT group, respectively (p&amp;lt;0001). Day 60 neutrophil engraftment (ANC &amp;gt;0.5 x 10 9/L) was 98.7% vs. 98.6% (p=0.84). Day 180 incidence of a GVHD grade II-IV and III-IV was 21.2% vs. 20.4% (p=0.92) and 8.1% vs. 6% (p=0.1), in pts receiving PTCy/TAC or CSA &amp; MMF versus the ATG/Tac/MTX GVHD prophylaxis, respectively. The 2-year (y) total and extensive chronic (c) GVHD were 33.7% vs. 30% (p=0.09) and 10.7 % vs. 11.2% (p=0.81), respectively. GVHD was the cause of death in 11.6% vs. 13.9% of pts who died. In the MVA, both aGVHD (grade II-IV or III-IV) and cGVHD (total or extensive) did not differ between the groups with hazard ratios (HRs) =1.15 (95% CI 0.86-1.53, p=0.35), HR=0.87 (95% CI 0.56-1.34, p=0.52), HR=0.91 (95% CI 0.7-1.18, p=0. 47 and HR=1.51 (95% CI 0.96-2.36, p=0.074). Two-y NRM was significantly lower in pts that received PTCy/TAC or CSA &amp; MMF versus ATG/TAC/MTX for GVHD prophylaxis, HR=1.57 (95% CI 1.07-2.3, p=0.022). Other HSCT outcome parameters did not differ between the groups. The HR for 2-y RI was 0.99 (95% CI 0.77-127, p=0. 93). The HRs for 2-y leukemia-free survival (LFS), overall survival (OS), and GRFS were HR=1.15 (95% CI 0.94-1.42, p&amp;lt;0.18), HR=1.18 (95% CI 0.94-1.49, p=0.16) and HR=1.12 (95% CI 0.93-1.36, p=0.22), respectively. Donor type and conditioning regimen were poor prognostic factors for grade II-IV, III-IV aGVHD, and total and extensive cGVHD. For cGVHD, additional poor prognostic factors were F donor to M pt combination and pt CMV seropositivity. Poor prognostic factors for LFS, OS, and GRFS were 9/10 UD, age (by 10 y), sAML, adverse-risk cytogenetics, lower KPS, and pt CMV seropositivity. For NRM, factors were the same apart from cytogenetics risk which was not a prognostic factor. In addition, time from diagnosis to HSCT was a prognostic factor for NRM and RI. Other poor prognostic factors for RI were lower KPS and pt CMV seropositivity. Conclusions: In this registry-based retrospective analysis, comparing PTCy in combination with TAC or CSA and MMF to ATG in combination with TAC and MTX as GVHD prophylaxis, we observed a similar incidence and severity of both aGVHD and cGVHD. NRM was significantly lower with the PTCy-based GVHD prophylaxis, while all other transplant outcome parameters were similar.

Patient-Reported Outcomes of BMT CTN 1703: A Randomized Phase III Study for Gvhd Prophylaxis - a Quality of Life Evaluation

Introduction A randomized phase III trial of post-transplantation cyclophosphamide (PTCy), tacrolimus, (Tac), and mycophenolate mofetil (MMF) versus tacrolimus/methotrexate (Tac/MTX) for graft-versus-host disease (GVHD) prophylaxis showed superior graft-versus-host disease-free, relapse-free survival (GRFS) in the PTCy-containing arm (NEJM, 2023). Here, we report the effect of GVHD prophylaxis on patient-reported outcomes and impact on quality of life (QOL). Methods The QOL study component of BMT CTN 1703 employed four primary endpoints: Lee Chronic GVHD Symptom Score and the PROMIS subscales of physical function, gastrointestinal symptoms, and satisfaction with participation in social roles. Secondary endpoints included hemorrhagic cystitis symptoms and Lee symptom subscale differences, with questionnaires to English and Spanish-speaking participants at enrollment and on Days 100, 180, and 365 post-transplant. Given the risk of missing assessments, an inverse probability weighted-independent estimating equations (IPW-IEE) model was applied for score comparison between arms, adjusting for baseline score, assessment time, age, donor type, disease risk index (DRI), planned conditioning regimen, and planned use of post-transplant maintenance therapy. Significance was declared at a 1.25% level for score comparisons between arms after Bonferroni correction for multiple testing. The analysis approach classified patients according to the intention-to-treat principle. Results QOL survey completion rates for patients at each timepoint were similar, exceeding 70% in each study arm. With the Lee Chronic GVHD Symptom Scale, higher scores indicate more severe symptoms. The IPW-IEE models indicated that the Lee Chronic GVHD Symptom Scale total scores were significantly lower in the PTCy arm compared to Tac/MTX at day 100 (mean difference [MD] -2.22, 99% confidence interval [CI] -5.05 to 0.61) and day 365 (MD -1.84, 99% CI -5.13 to 1.45, p=0.01 for overall treatment effect across all timepoints, Figure 1). Nutrition subscores were significantly better with PTCy at day 100 (MD -2.41, 99% CI -5.06 to 0.24, p=0.0014). Mouth scores were significantly better in the PTCy arm at day 365 (MD -7.09, 99% CI -13.21 to -0.98, p=0.0035). Patients over 65 years of age had better psychological subscores across the study population (MD -4.80, 99% CI -8.91 to -0.69, p=0.0026); no interaction was found between age and study treatment. Patient-reported hemorrhagic cystitis symptoms showed no significant difference between the study arms at any post-transplant time point. There was no significant treatment effect observed on the 3 PROMIS subscales. Across the entire study population, both relapse and acute GVHD were associated with worse scores on the Lee Symptom Scale, and PROMIS physical function, gastrointestinal symptoms, and social functions subscales. Chronic GVHD was associated with worse scores on the Lee Symptom Scale only, not the PROMIS subscales. No associations were found between patient-reported QOL at baseline and 1-year GRFS, disease-free survival, or overall survival. Conclusions The PTCy arm of BMT CTN 1703 showed superior GRFS, and this study confirms better patient-reported outcomes with PTCy. Patients who received PTCy showed better nutrition and mouth subscores on the Lee Chronic GVHD Symptom Scale compared to those who received Tac/MTX, possibly due to lower observed rates of severe acute and chronic GVHD in the PTCy arm. No association was found between patient-reported baseline quality of life and survival endpoints, suggesting the necessity of further research to elucidate the interplay of treatment strategies, patient factors, and their impact on long-term outcomes.

Phase 1 Trial Results for Patients with Advanced Hematologic Malignancies Undergoing Reduced Intensity Allogeneic HCT with Orca-T Donor Cell Therapy Product and Single Agent Tacrolimus

Introduction: Reduced intensity conditioning hematopoietic bone marrow stem cell transplantation (HSCT-RIC) is the only curative option for many hematological malignancies in older/unfit patients. Strategies to minimize complications such as graft versus host disease (GVHD) in HSCT include donor graft engineering but this approach has not been widely tested to the RIC setting due to a potential trade-off between engraftment and reduced GVHD with T cell depletion strategies. Here we present the interim results of our single center Phase I trial evaluating the T cell reduced Orca-T cell therapy product and single agent tacrolimus in the RIC setting. Methods: The trial is a single-center open-label phase 1 feasibility and safety study for dose escalation of conventional T cell (Tcon) infusion. Primary objectives included measuring the incidence of grade III-IV acute GVHD, time of engraftment and donor T cell chimerism at day +30. Secondary objectives are measuring relapse free survival, severity of GVHD and incidence of serious infections. While the study has three independent trial arms depending on donor type (HLA matched related and unrelated, 9/10 HLA matched or haploidentical matched), accrual has focused on the HLA-matched cohort which is reported here. The first 11 patients on this arm were conditioned with fludarabine 40mg/m 2, melphalan 50 mg/m 2 and 4 Gy of total body irradiation (TBI), an additional 4 patients have been treated with thiotepa 10 mg/kg replacing the melphalan. All patients received single agent tacrolimus with a target goal of 6-8 ng/ml. Results: A total of 15 HLA-matched patients have been recruited thus far in this interim dose escalation analysis. The median patient age is 68.0 years (range 62 to 72), with 73% male (11/15) patient distribution. Pre transplant, 53% had acute myeloid leukemia (8/15), 20% had myelodysplastic syndrome (3/15), 13% had acute lymphoblastic leukemia (2/15) and 13% had a myeloproliferative neoplasm (2/15). Prior to transplant, all acute leukemia patients were in complete remission (CR) or CR with incomplete count recovery. Median follow up was 10.4 months for the entire cohort (range 2 to 20 months). 14/15 patients had engraftment by day 20 and 1/15 at day 39 post-transplant. Based on these findings, no dose escalation of Tcon infusion was needed. None of the patients had infusion reactions on day of transplant nor engraftment syndrome. Median percent donor chimerism for CD15 was high, with 100% at day 30 (15/15, range 94% to 100%) and 99% (13/15, patients with available data, range 98% to 100%) at day 90. Median CD3 chimerism at days 30 and 90 of transplant were also high at 99% (15/15, range 68% to 100%) and 99% (for 13/15 patients with available data, range 78% to 100%) respectively. No patients developed grade III-IV acute GVHD ( Fig.), defined &amp;lt;100 days post-transplant. One patient developed grade II aGVHD. In 12 months, the incidence for moderate to severe chronic GVHD was 7%. The 12-month relapse free survival (RFS) is thus far 79% ( Fig.). The cumulative incidence for grade 2 and 3 infections in the first 90 days was 26.7%, where 2 patients died. One patient died at day 180 from liver biopsy complications for late onset hepatic sinusoidal obstruction syndrome. No surviving patient has had disease relapse. Conclusions: These early results demonstrate that Orca-T is a safe and feasible transplant strategy in the RIC setting for patients with advanced hematological malignancies. Patients showed robust and early donor myeloid and eventual full donor T cell engraftment. The low incidence of acute and chronic GVHD with low rates of disease relapse, suggest retention of graft versus leukemia effect. Few studies of donor graft-engineered products have been successfully evaluated in the RIC setting and merits larger multicenter studies evaluatingGVHD-free and RFS post-transplant to validate these findings.

The Presence of Somatic Mutation in Donor Does Not Affect Long-Term Outcomes in 339 Patients Following Allogeneic Hematopoietic Stem Cell Transplantation Using Uniform Fludarabine/Busulfan Myeloablative Conditioning and Cyclosporine/Methotrexate and ATG Gvhd Prophylaxis

Introduction: Clonal hematopoiesis with indeterminate potential (CHIP) constitutes a part of the biological aging process and comprises the acquisition of somatic mutations in hematopoietic stem cells (HSCs). In the context of allogeneic hematopoietic stem cell transplantation (HCT), the potential transfer of CHIP from donor to recipient may raise concerns on HCT-related complications. There are contradictory data on donor CHIP's impact on long-term transplant outcomes using very diverse conditioning regimen as well as various graft-versus-host disease (GVHD) prophylaxis. This study aims to evaluate the impact of donor CHIP on allogeneic HCT outcomes in a cohort of the patients transplanted using a uniform, myeloablative intensity conditioning of Fludarabine-Busulfan (4 days) as well as Cyclosporine/Methotrexate with 4.5 mg/kg rabbit antithymocyte globulin (ATG) over 3 days for GVHD prophylaxis. Patients and methods: Peripheral blood samples were obtained from recipients and their corresponding donors who underwent allogeneic HCT at Tom Baker Cancer Centre, Calgary, Canada. Samples were archived from 339 patients and 255 donors prior to HCT, and additional patient sampling was done on day 28 (D28), day 56 (D56), or day 84 post allogeneic HCT (D84). As a result, paired recipient-donor samples were available for 255 HCTs. This study was approved by the institutional review boards of Princess Margaret Cancer Centre, Toronto, and Tom Baker Cancer Centre, Calgary. For the detection of CHIP, we have applied a bar-coded error-corrected sequencing protocol, a single-molecule molecular inversion probe capture protocol (NAR Genom Bioinform, 2022), which was performed at Wiesmann Institute of Science (Rehovot, Israel). We designed probes targeting 34 genes covering CHIP mutations along with other AML related mutations. Bar-coded NGS library was generated and processed. All statistical analyses were performed using R statistical software 3.5.0 and EZR version 1.41. Results: Sixty-seven clonal mutations in 56 recipients (18.2%) and 22 clonal mutations in 18 donors (7.1%) were detected prior to HCT. For recipients, TET2, JAK2, RUNX1, PPM1D, and DNMT3A were detected in at least 2 patients or more. For donors, the most frequently mutated gene was TET2 (3.1%), and the seconds were DNMT3A and PTPN11 (1.2% for both). Baseline characteristics of 255 patient-donor pairs did not show any difference between D-CHIP and no D-CHIP groups except donor age. Donor CHIP status was distributed evenly throughout most of the demographics of recipients, type of disease, pre-transplant status, and transplant procedure. Most of the pts received peripheral blood stem cells (97%). With a median follow up duration 6.02 years, the 5-year OS rates tend to be higher in no D-CHIP group than D-CHIP group (63.1% vs 42.8%) with a HR of 1.73 (95% CI [0.90-3.35]), although it was not statistically significant (p=0.096). The cumulative incidence of relapse for both groups were not different in 5 years (28.1% vs. 28.4%, p=0.849). The cumulative incidence of NRM within 5 years in D-CHIP group was slightly higher than no D-CHIP group (28.4% vs 17.5%), but it was not statistically significant (p=0.250). Neutrophil engraftment by day 28 was 99.1% vs. 100%, without statistical difference between the two groups (p=0.785). The cumulative incidence of grade II-IV acute GVHD within day+100 seemed to be higher in D-CHIP group compared to no D-CHIP group, but it was not statistically significant (24.8% vs. 34.5%, p=0.148; Figure A). In terms of chronic GVHD, cumulative incidence of moderate to severe GVHD was significantly higher in 5 years after transplant (29.4% vs. 58.8%; HR 2.55 [1.331-4.96], p=0.006; Figure B). Even when we set the cut off level of donor CHIP positivity up to &amp;gt;1% or &amp;gt;10%, the association between donor CHIP and risk of chronic GVHD remained significant. The impact of donor CHIP on the cumulative incidence of moderate to severe GVHD was confirmed in multivariate analysis (HR 2.3 [1.3-4.1], p=0.003). Other factors associated with moderate to severe chronic GVHD were previous history of grade II-IV acute GVHD (p=0.008) and donor type (p=0.054). Conclusion: Under clinical setting of uniform conditioning regimen and GVHD prophylaxis incorporating ATG (4.5mg/kg), donor CHIP was found to be associated with higher risk of moderate to severe chronic GVHD, while it does not affect other allogeneic HCT outcomes.

Selecting the Right Alternative Donor: Comparison of Outcomes of HLA-Mismatched Alternative Donor Hematopoietic Cell Transplantations in Adult Patients with Acute Lymphoblastic Leukemia Regarding KIR-Ligand Mismatch

Background: Allogeneic hematopoietic cell transplantation from cord blood (CBT) or haploidentical donor (HIDT) has proved to be a viable option for patients unable to find a human leukocyte antigen (HLA)-matched conventional donor. However, few single-centered studies have compared outcomes of the two alternative donor transplantations in adult acute lymphoblastic leukemia (ALL). Aim: Our aim is to compare outcomes of adult ALL patients treated with CBT with those treated with HIDT. Secondly, we tried to find out factor that could be considered in selecting donor for alternative donor transplantation to improve clinical outcomes. Methods: We compare outcomes of adult ALL patients treated with CBT (n=134) between 2008 and 2022 with those treated with HIDT (n=47) between 2018 and 2022.Conditioning regimen for CBT consisted of total body irradiation (12Gy) plus cytarabine (9g/m 2) plus fludarabine (150mg/m 2). Graft-versus-host disease (GVHD) prophylaxis was attempted using tacrolimus and mycophenolate mofetil. For HIDT, we used reduced toxicity conditioning (RTC) regimen including fludarabine (150mg/m 2) plus busulfan (6.4mg/kg). GVHD prophylaxis was done with ATG 1.5mg for 4 days plus short course methotrexate (MTX) (15mg/m 2) plus tacrolimus. Killer cell immunoglobulin-like receptor (KIR) ligand mismatch was calculated in both GVH and HVG direction using HLA-KIR ligand database, and its effect on clinical outcomes of alternative donor transplantation was investigated. Results: In HIDT, CD34+ cell count (´10 6/kg) was significantly higher (7.4 vs. 0.1, P&amp;lt;0.001), and the patients were older (49 vs. 33.5, P&amp;lt;0.001) compared to CBT. Other characteristics, such as cytogenetic risk and leukocyte count at diagnosis, did not show significant difference between the two groups. Incidence of acute GVHD II-IV (51.1% vs. 50.0%), III-IV (25.5% vs. 17.9%), and moderate to severe chronic GVHD (10.8% vs. 11.0%) between HIDT vs. CBT were similar. After median follow-up of 39.4 months (range: 5.5-167.4), HIDT showed higher cumulative incidence of relapse (CIR) compared to CBT (47.9% vs. 18.9%, P&amp;lt;0.001), which remained true even after stratifying by age subgroup (Age&amp;lt;40: P=0.033, Age≥40: P=0.002). Conversely, CBT showed higher non-relapse mortality (NRM) than HIDT (22.8% vs. 9.0%, P=0.038), but the same was true only in the older age subgroup (Age&amp;lt;40: P=0.484, Age≥40: P=0.002). These effects summed up to produce comparable results in estimated 3-year disease-free survival (DFS) of CBT and HIDT (58.4% vs. 43.5%, P=0.103), especially in the older subgroup (38.7% vs. 40.7%, P=0.897). Multivariate analysis also revealed that HIDT was related with higher relapse (HR 3.47; 95%CI 1.92-6.27, P&amp;lt;0.001), and CBT with higher NRM (HR 4.18; 95%CI 1.42-12.3, P=0.009). GVH direction KIR ligand mismatching worked for lower 3-year DFS in CBT (40.3% vs. 74.4%, P=0.007), although CIR and NRM did not show significant difference (27.8% vs. 15.6%, P=0.178; 35.0% vs 18.4%, P=0.057, respectively). On the other hand, the mismatch resulted in lower incidence of acute GVHD II-IV (32.0% vs. 54.2%, P=0.011). The trend remained when such effect was investigated separately in CBT and HIDT, but it was not statistically significant (33.3% vs. 53.1%, P=0.082; 28.6% vs. 57.6%, P=0.053, respectively). Conclusions: Our data shows higher NRM in CBT, and unexpected higher relapse rate in HIDT. Age of the patient should be considered when choosing CBT, because in older patients CBT showed notably worse NRM compared to HIDT. Higher incidence of relapse in HIDT may be attributable to ALL disease characteristics itself or insufficient elimination of leukemic cells by RTC regimen with stronger GVHD prophylaxis. Similar to what is known in acute myeloid leukemia, GVH direction KIR incompatibility showed protective effect against acute GVHD in ALL. However, the mismatch resulted in worse DFS in ALL patients treated with CBT, but not in those treated with HIDT. Possible explanation to this phenomenon is that the number of NK cells in cord blood was insufficient for mismatch-induced graft-versus-leukemia effect, while its immune response against infected cells was suppressed by the same mechanism that resulted in lower acute GVHD. Keywords: Acute lymphoblastic leukemia, Cord blood transplantation, Haploidentical donor transplantation, HLA-mismatched transplantation, Killer-cell immunoglobulin like receptor

Higher Infused CD34+ Cell Dose Does Not Influence Clinical Outcomes in Allogeneic Peripheral Blood Stem Cell Transplantation Using Post-Transplant Cyclophosphamide in Children with High-Risk Leukemia

Background: The impact of infused graft cell dose on outcomes, including graft-versus-host disease (GVHD) and relapse, which have been major challenges in allogeneic hematopoietic stem cell transplantation (HSCT), remains unclear. Post-transplant cyclophosphamide (PTCy) has emerged as an effective and safe GVHD prophylaxis strategy, with improved GVHD incidence and relapse-free survival (RFS). Early practice of unmanipulated peripheral blood stem cell transplantation (PBSCT) using PTCy was commonly performed with a restriction on the CD34 + cell dose to minimize the risk of GVHD. However, recent studies demonstrated the protective effect of CD34 + cells on relapse, with no association with GVHD, thereby raising questions about the optimal cell dose. In this context, we aimed to study the impact of infused cell dose on outcomes in children with high-risk leukemia who underwent allogeneic PBSCT using PTCy. Methods: A retrospective analysis was conducted on 50 pediatric patients (median age at diagnosis : 9.3 years, range, 0.3-17.3) with hematologic malignancy (33 acute myeloid leukemia, 12 acute lymphoblastic leukemia, and 4 myelodysplastic syndrome/myeloproliferative neoplasm, 1 other) in first or second remission between 2019 and 2023. They received their first allogeneic PBSCT and donors included matched or mismatched unrelated donors (n=12) and haploidentical family donors (n=38). Conditioning was myeloablative, and PTCy-based GVHD prophylaxis (50mg/kg/day on days 3 and 4) was used for all patients. The patients were divided into three groups based on infused CD34 + cell dose: high dose group (&amp;gt;10 × 10 6/kg, N=10), intermediate dose group (5-10 × 10 6/kg, N=24), and low dose group (&amp;lt;5 × 10 6/kg, N=16). Results: The median age at HSCT was 11.6 years (range, 0.7-24.9). The median dose of infused CD34 + cells and CD3 + cells was 6.5 x 10 6/kg and 48.6 x 10 7/kg, respectively. There was a tendency for the mean dose of infused CD3 + cells to increase in the group with higher infused CD34 + cell dose: 47.6 x 10 7/kg for low dose group, 57.5 x 10 7/kg for intermediate dose group, and 73.4 x 10 7/kg for high dose group ( P=0.053). Patients receiving a higher dose of CD34+ cells had significantly shorter median time to neutrophil engraftment (13 days in high dose group vs. 14 days in intermediate dose group vs. 17 days in low dose group, P&amp;lt;0.001). The time to platelet engraftment was similar among the three groups. There was no difference among high dose, intermediate dose, and low dose groups in the cumulative incidence (CI) of day+100 grades II-IV acute GVHD and moderate to severe chronic GVHD (grades II to IV acute GVHD: 60.0% vs. 63.6% vs. 73.3% [ P=0.988], respectively; moderate to severe chronic GVHD: 22.2% vs. 29.2% vs. 25.0% [ P=0.961], respectively). With a median observation period of 20.4 months (range, 3.0-46.8) from transplant, RFS and overall survival (OS) showed a non-significant trend towards a higher survival rate in the high dose group compared to the other groups (RFS: 76.2% in high dose group vs. 62.1% in intermediate dose group vs. 62.6% in low dose group, P=0.694; OS: 88.9% in high dose group vs. 63.0% in intermediate dose group vs. 76.0% in low dose group, P=0.788). Conclusions: Higher number of infused CD34 + cell dose was associated with faster neutrophil engraftment. For patients in the high dose group (CD34 + cell dose &amp;gt; 10 x 10 6/kg with a relatively higher number of CD3 + cells), a non-significant trend toward a higher survival rate was observed, with no detrimental impact on GVHD. PBSCT in a pediatric patient from an unrelated or haploidentical adult donor may result in a high infused cell dose. Our findings suggest that restricting the number of infused CD34 + cell dose may not be necessary in the setting of allogeneic PBSCT with PTCy. Larger cohort studies are needed to confirm the potential benefits and drawbacks of a higher cell dose in children who receive PBSCT within a PTCy setting.