Reduced Intensity Conditioning Regimen Research Articles

Graft-versus-host-disease prophylaxis with ATG or PTCY in patients with lymphoproliferative disorders undergoing reduced intensity conditioning regimen HCT from one antigen mismatched unrelated donor

Post-transplant cyclophosphamide (PTCY) has been introduced as graft-versus-host disease (GvHD) prophylaxis in mismatched and matched unrelated hematopoietic cell transplant (HCT). However, data comparing outcomes of PTCY or ATG in patients undergoing a 1 antigen mismatched HCT for lymphoproliferative disease are limited. We compared PTCY versus ATG in adult patients with lymphoproliferative disease undergoing a first 9/10 MMUD HCT with a reduced intensity conditioning regimen from 2010 to 2021. Patients receiving PTCY were matched to patients receiving ATG according to: age, disease status at transplant, female to male matching, stem cell source and CMV serology. Grade II-IV acute GvHD at 100 day was 26% and 41% for the ATG and PTCY group, respectively (p = 0.08). Grade III–IV acute GvHD was not significantly different between the two groups. No differences were observed in relapse incidence, non-relapse mortality, progression-free survival, overall survival and GvHD-relapse-free survival at 1 year. The cumulative incidence of 1-year extensive chronic GvHD was 18% in the ATG and 5% in the PTCY group, respectively (p = 0.06). In patients with lymphoproliferative diseases undergoing 9/10 MMUD HCT, PTCY might be a safe option providing similar results to ATG prophylaxis. Due to the limited number of patients, prospective randomized trials are needed.

Nelarabine-containing salvage therapy and conditioning regimen in transplants for pediatric T-cell acute lymphoblastic leukemia and lymphoma.

Therapy for relapsed or refractory (r/r) T-cell acute lymphoblastic leukemia (T-ALL) and T-cell lymphoblastic lymphoma (T-LBL) in children is challenging, and new treatment methods are needed. We retrospectively analyzed eight patients with r/r T-ALL (five patients) and T-LBL (three patients) who were treated with nelarabine (NEL) plus etoposide, cyclophosphamide, and intrathecal therapy, administered 3days apart. Five patients achieved a complete response, and the other three achieved a partial response (PR). All patients underwent hematopoietic stem cell transplantation (HSCT) after two cycles of treatment, except for one patient who received one cycle. Three patients who had previously received HSCT were treated with reduced-intensity conditioning regimens, including fludarabine, melphalan, and NEL; one survived for over 5years after the second HSCT. Grade 2 neuropathy occurred in one patient, but other severe toxicities commonly associated with NEL were not observed during NEL administration in combination with chemotherapy. The 2-year overall survival and event-free survival rates were 60.0% and 36.5%, respectively. The addition of NEL to reinduction chemotherapy was useful in achieving remission and did not lead to excessive toxicity. In addition, a conditioning regimen, including NEL, appeared to be effective in patients who had previously undergone HSCT.

Clofarabine and High-Dose Melphalan Reduced Intensity Conditioning Regimen for Allogeneic Stem Cell Transplantation

Clofarabine and High-Dose Melphalan Reduced Intensity Conditioning Regimen for Allogeneic Stem Cell Transplantation

Hematopoietic stem cell transplantation in children with chronic granulomatous disease: the Spanish experience.

Hematopoietic stem cell transplantation (HCT) can cure chronic granulomatous disease (CGD). However, transplant-associated morbidity or mortality may occur, and it is still controversial which patients benefit from this procedure. The aim of this retrospective study was to evaluate the outcome of pediatric patients who received HCT in one of the Spanish pediatric transplant units. Thirty children with a median age of 6.9 years (range 0.6-12.7) were evaluated: 8 patients received a transplant from a sibling donor (MSD), 21 received a transplant from an unrelated donor (UD), and 1 received a haploidentical transplant. The majority of the patients received reduced-intensity conditioning regimens based on either busulfan plus fludarabine or treosulfan. Relevant post-HCT complications were as follows: i) graft failure (GF), with a global incidence of 28.26% (CI: 15.15-48.88), 11.1% in patients with MSD (1.64-56.70) and 37.08% in unrelated donors (19.33-63.17); and ii) chronic graft-versus-host disease (GVHD), with an incidence of 20.5% (8.9-43.2), 11.1% in patients with MSD (1.64-56.70) and 26.7% in unrelated donors (10.42-58.44). Post-HCT infections were usually manageable, but two episodes of pulmonary aspergillosis were diagnosed in the context of graft rejection. The 2-year OS was 77.3% (55.92-89.23). There were no statistically significant differences among donor types. HCT in patients with CGD is a complex procedure with significant morbidity and mortality, especially in patients who receive grafts from unrelated donors. These factors need to be considered in the decision-making process and when discussing conditioning and GVHD prophylaxis.

Subjective Oral Dryness following Hematopoietic Cell Transplantation: A Report from the Orastem Study

Xerostomia, or subjective oral dryness, is a serious complaint after hematopoietic cell transplantation (HCT). Xerostomia is rated as one of the most bothersome symptoms by HCT recipients, negatively affecting quality of life. This substudy of the Orastem study, a prospective longitudinal, international, observational, multicenter study, aimed to describe the prevalence and severity of xerostomia following HCT. Furthermore, the effect of the conditioning regimen, type of transplantation, and oral mucosal changes related to chronic graft-versus-host disease (cGVHD) in the development of xerostomia were studied. All HCT recipients rated xerostomia on a scale of 0 to 10 before the conditioning regimen, several times early post-HCT, and at 3 months post-HCT, and only allogeneic HCT recipients also rated xerostomia at 6 and 12 months post-HCT. In addition, stimulated whole mouth saliva was collected several times. Linear regression models and longitudinal mixed-effects models were created to investigate the influence of risk indicators on xerostomia. A total of 99 autologous and 163 allogeneic HCT recipients were included from 6 study sites in Sweden, Canada, the Netherlands, and the United States. The prevalence of xerostomia was 40% before the conditioning regimen, 87% early post-HCT, and 64% at 3 months post-HCT. Complaints after autologous HCT were transient in nature, while the severity of xerostomia in allogeneic HCT recipients remained elevated at 12 months post-HCT. Compared to autologous HCT recipients, allogeneic HCT recipients experienced 1.0 point more xerostomia (95% confidence interval [CI], .1 to 2.0) early post-HCT and 1.7 points more (95% CI, .4 to 3.0) at 3 months post-HCT. Allogeneic HCT recipients receiving a high-intensity conditioning regimen experienced more xerostomia compared to those receiving a nonmyeloablative or reduced-intensity conditioning regimen. The difference was 2.0 points (95% CI, 1.1 to 2.9) early post-HCT, 1.8 points (95% CI, .3 to 3.3) after 3 months, and 1.7 points (95% CI, .0 to 3.3) after 12 months. Total body irradiation as part of the conditioning regimen and oral mucosal changes related to cGVHD did not significantly influence the severity of xerostomia. Conditioning regimen intensity was a significant risk indicator in the development of xerostomia, whereas total body irradiation was not. Allogeneic HCT recipients experienced more xerostomia than autologous HCT recipients, a difference that cannot be explained by a reduction in stimulated salivary flow rate or the development of oral mucosal changes related to cGVHD.

Single non-blood-related umbilical cord blood transplantation using a reduced-intensity conditioning regimen for the treatment of severe aplastic anemia

Objective: To evaluated the clinical efficacy of a reduced-intensity preconditioning regimen for single non-blood-related umbilical cord blood transplantation (sUCBT) in the treatment of severe aplastic anemia (SAA) . Methods: The clinical data of 63 patients with SAA who underwent sUCBT from January 2021 to July 2023 at the Department of Hematology of the First Affiliated Hospital of USTC were retrospectively analyzed. Fifty-two patients received total body irradiation/total bone marrow irradiation (TMI) combined with fludarabine or a cyclophosphamide- conditioning regimen (non-rATG group) , while 11 patients received rabbit anti-human thymocyte immunoglobulin (rATG) combined with TMI, fludarabine, or the cyclophosphamide-conditioning regimen (rATG group) . All patients received cyclosporine A and mycophenolate mofetil for graft-versus-host disease (GVHD) prophylaxis. Complications post-transplantation and long-term survival were compared between the two groups. Results: The baseline parameters were balanced between the two groups (P>0.05) . In the rATG group, all patients achieved stem cell engraftment, and in the non-rATG group, five patients had primary graft failure. There was no significant difference in the cumulative incidence of neutrophil engraftment at 42 days after transplantation or platelet engraftment at 60 days between the two groups. The incidence of grade Ⅱ-Ⅳ acute GVHD in the rATG group was significantly lower than in the non-rATG group (10.0% vs. 46.2% , P=0.032) , and the differences in the cumulative incidences of grade Ⅲ/Ⅳ acute GVHD and 1-year chronic GVHD were not statistically significant (P=0.367 and P=0.053, respectively) . There were no significant differences in the incidences of pre-engraftment syndrome, bacterial bloodstream infections, cytomegalovirus viremia, or hemorrhagic cystitis between the two groups (P>0.05 for all) . The median follow-up time for surviving patients was 536 (61-993) days, and the 1-year transplantation related mortality (TRM) of all patients after transplantation was 13.0% (95% CI 6.7% -24.3% ) . Among the patients in the non-rATG and rATG groups, 15.5% (95% CI 8.1% -28.6% ) and 0% (P=0.189) , respectively, had mutations. The 1-year overall survival (OS) rate of all patients after transplantation was 87.0% (95% CI 75.7% -93.3% ) . The 1-year OS rates in the rATG group and non-rATG group after transplantation were 100% and 84.5% , respectively (95% CI 71.4% -91.9% ) (P=0.198) . Conclusion: The preliminary results of sUCBT with a low-dose irradiation-based reduced-intensity conditioning regimen with fludarabine/cyclophosphamide for the treatment of patients with SAA showed good efficacy. Early application of low-dose rATG can reduce the incidence of acute GVHD after transplantation without increasing the risk of implantation failure or infection.

Thrombopoietin mimetic therapy alleviates radiation-induced bone marrow vascular injury in a bone marrow transplant mouse model.

There is a need for therapies that can mitigate bone marrow dysfunction and organ toxicity that occur following myeloablative injury and reduced intensity conditioning regimens used in patients undergoing bone marrow transplantation (BMT). The pathogenesis of adverse effects from BMT conditioning has been linked to injury to the vascular endothelium, bone marrow (BM), and other organs. To evaluate the impact of the thrombopoietin mimetic drug JNJ-26366821 (TPOm) on BM vascular recovery in mice undergoing myeloablative radiation conditioning followed by BMT. TPOm (doses: 0 µg, 300 µg, 1000 µg per Kg body weight) was administered on Days 0 and 7 after BMT, in mice receiving a total body irradiation (TBI) conditioning regimen (5.5 Gy x 2) before congenic BMT. BM donner cell engraftment was analyzed using flow cytometry on Days 7, 14, and 30 post-BMT. The morphological and biophysical properties of the BM vasculature were evaluated by intravital multiphoton microscopy (MPM) and immunofluorescence confocal imaging. Herein, morphological properties involve microvascular density (MVD), vessel diameter, and vascular area, while biophysical properties include transfer rate (Ktrans) of contrast within the BM vascular niche, as well as the fractional volume (vec ) of extracellular extravascular tissue (EES). No significant difference in donor chimerism was observed at days 7, 14, and 30 post-BMT, between TPOm and PBS-treated mice. TPOm intervention improved BM vasculature regeneration in transplanted mice. The MVD, Ktrans, and BM vasculature as well as vascular endothelial growth factor receptor-2 (VEGFR2) in the BM, showed a dose dependent improvement in mice treated with TPOm. On day 14 post-BMT, the group receiving 1000 µg/Kg TPOm showed significant shifts (p-value < 0.05) in MVD, Ktrans, and VEGFR2 expression from their corresponding control types (TPOm dose 0 µg) towards levels comparable to healthy controls. TPOm intervention augments BM vascular structure and function, which may be important for hematopoietic recovery and bone marrow function in radiation conditioned hematopoietic stem cell transplant patients, in addition to enhancing platelet recovery.

Non-invasive Estimation of Microvasculopathy & Endothelial Dysfunction in Stem Cell Transplant Recipients and its Relationship with GVHD.

Microvasculopathy and endothelial dysfunction play important roles in the development of post-transplant complications, including graft-versus-host disease (GVHD). We assessed structural microvasculopathy by employing nailfold video capillaroscopy (NFVC) and endothelial dysfunction via flow-mediated dilatation (FMD) of the brachial artery in recipients of hematopoietic stem cell transplantation. Recipients of stem cell transplantation were included in this study post day+100 and divided into two cohorts. The first cohort consisted of 35 recipients of allogeneic hematopoietic stem cell transplantation (HCT) and the second cohort was comprised of 31 recipients of autologous HCT. A third cohort included 35 healthy individuals. NFVC was conducted on the second to fifth fingers of both hands using an Optilia video capillaroscope at 200× magnification, and the images were analyzed according to the European Alliance of Associations for Rheumatology (EULAR) criteria. The following parameters were used to measure vasculopathy: (a) median capillary density, derived from the capillary density of eight fingers, (b) median capillary diameter, derived from maximum capillary apical diameters of eight fingers, and (c) significant neoangiogenesis (neoangiogenesis present in ≥2 fingers). FMD of the right brachial artery was observed by high-resolution ultrasonography using the principle of post-occlusive reactive hyperemia, and video images were analyzed using edge-detecting software. The median capillary diameter was significantly higher in the allo-HCT cohort (20.56±5.17 micrometer) compared to the auto-HCT cohort (16.19±3.31 micrometer; p<0.001) and healthy controls (14.66±2.61 micrometer; p<0.001). The median capillary density was significantly lower in the allo-HCT cohort (median: 6 capillaries/mm, range: 5-9 capillaries/mm) compared to the auto-HCT cohort (median: 8.5 capillaries, range: 5-12 capillaries/mm; p<0.001) and healthy controls (median: 8 capillaries/mm, range: 7-10.5 capillaries/mm; p<0.001). The allo-HCT cohort had a higher proportion of patients with significant neoangiogenesis (86%) than the auto-HCT cohort (10%) and healthy controls (9%). The presence of significant neoangiogenesis was more frequent in the subgroup of patients with a history of GVHD (93%) compared to the subgroup of patients without any history of GVHD (57%; p=0.044). No significant differences in NFVC parameters or FMD were observed between recipients of myeloablative and reduced-intensity conditioning regimens. There was no significant difference in NFVC parameters between the auto-HCT cohort and healthy controls. There was no significant difference in FMD among the three cohorts; however, a higher proportion of patients in the allo-HCT cohort (28%) had lower FMD than those in the auto-HCT cohort (3%) and healthy controls (6%), suggesting endothelial dysfunction. Our findings demonstrate the presence of structural microvasculopathy in allo-HCT recipients and suggest a possible role of alloreactivity in the pathogenesis of post-HCT microvasculopathy.

Conditioning Intensity in Patients Aged > 50 Years Undergoing Allogeneic Hematopoietic Cell Transplantation for Myelodysplastic Syndrom: A Study on Behalf of the Chronic Malignancies Working Party of the EBMT

Introduction Myelodysplastic syndromes (MDS) affect mainly older individuals, with a median age &amp;gt; 70 years. Reduced intensity conditioning (RIC) is usually used for MDS patients undergoing allo-HCT to balance the toxicity of myeloablative conditioning (MAC), particularly in the more elderly or those with multiple comorbidities. In addition, the clinicians subjective opinion/ experience remains a major guide in choosing the intensity of conditioning. The majority of studies comparing RIC and MAC reported a higher cumulative incidence (CI) of relapse (RP) and lower non-relapse mortality (NRM) in the RIC groups. However, the impact of conditioning intensity on outcome after allo-HCT remains controversial. To gain more insight into the impact of conditioning on outcomes following allo-HCT for MDS, we evaluated RIC versus MAC in MDS patients aged &amp;gt; 50 years in a large EBMT cohort. Patients and methods This was a registry-based retrospective multicenter study that included MDS patients above 50 years, who received a first allo-HCT following RIC or MAC conditioning between 2014 - 2018 and had data on IPSS-R at allo-HCT and RIC/MAC conditioning available. Data collected included disease features, patient, donor and transplantation characteristics. Patients with ex vivo T-cell depletion were excluded. Variables with missing values ≤35% were handled with multiple imputation. OS, DFS, RP and NRM were compared using the Log-rank and Gray's test for CI, and (cause-specific) Cox proportional hazard models for multivariable analyses (MVA). A conditional logistic regression after propensity score matching (PSM) was also performed for potential risk confounders. Results Among the 1393 included patients (from 121 centres), 922 (66%) were men and the median age at allo-HCT was 62.8 (IQR:58.2-66.9) years. The majority of patients (n=884; 64.3%) had RAEB. The IPSS-R was recorded as very low/low (n=598, 43%), intermediate (n=352, 25%) and high/very high (n=443, 32%). Cytogenetic risk score was very good/good (n=932, 66.9%), intermediate (n=250, 17.9%) and poor/very poor (n=211, 15.1%). Karnofsky index was ≥ 90 in 916 pts (69.3%) and HCT-CI ≥ 3 in 292 pts (27.3%). Disease status at transplant was recorded as complete remission (n=486, 34.9%), untreated/stable disease (n=544, 39.0%), and progressive disease (n=310, 22.3%). Donor was HLA-matched (related/unrelated) (n=989, 71.1%), unrelated HLA-mismatched (n=286, 20.5%) or familial HLA haplo-identical donor (n=153, 10.9%). Source of SC was BM (n=112, 8.0%) and PB (n=1255, 90.0%). A RIC regimen was used in 1053 (75.5%) patients. In vivo T-cell depletion with anti-thymocyte globulin (ATG) was used in 941 pts (67.5%). Median time of follow up was 27.9 months (IQR: 26.4-30.6). Median rate of OS in RIC vs MAC group was 54.2(95% CI: 33.5-NA) vs 46.2(95% CI: 32.6-69.4), p=0.84; median rate of DFS was 28.4(95% CI: 19.4-58) vs 28.0 (95% CI: 22.5-39.1), respectively, p=0.64. Cumulative incidence rate of RP and NRM for RIC vs MAC regimen at 36 months were 31.2% vs 29.7% and 29.9% vs 30.4%, respectively (Figure 1). Both in univariable and MVA we did not observe a significant (&amp;gt; 0.05) association between the conditioning regimen on the outcomes. Similar results were obtained using PSM to control potential confounders (such as age, source of SC, stage of disease, HCT-CI, cytogentic risk score, neutrophile and platelet counts and sAML) and conditional logistic regression analysis (Table1). Conclusion To our knowledge, this is the largest retrospective cohort study that highlights a lack of association between RIC/MAC regimen and outcomes in MDS patients undergoing allo-HCT. Our results are in line with the recent published systematic review and metanalysis where evidence for using a one conditioning regimen over another remains weak [1,2]. 1) Rashidi et al. Biology of Blood and Marrow Transplantation. 2020; 26:138-141. 2) Akbar et al. Blood.2020; 136:40-41.

Bone Marrow Versus Peripheral Blood in HLA-Matched Sibling Transplantation: Does the Stem Cell Source Matter in Severe Aplastic Anemia?

Background Selecting a graft source is critical in HLA-matched sibling donor hematopoietic stem cell transplantation (MSD-HCT) for severe aplastic anemia (SAA). Since graft-versus-host-disease (GVHD) is the major cause of mortality after MSD-HCT, and SAA patients do not need the graft-versus-leukemia effect, the selection of a suitable source of stem cells becomes critical. Although bone marrow (BM) is the preferable stem cell source based on the registry-based studies, mobilized peripheral blood stem cells (PBSC) may offer faster engraftment with rapid immune reconstitution. Moreover, the recent advances in conditioning regimens have significantly reduced transplantation-related complications. Here, we compared the long-term outcomes of BM vs PBSC as a graft source in adult patients with SAA who received MSD-HCT with the reduced intensity conditioning (RIC) regimen. Method We conducted a retrospective analysis of 171 consecutive SAA adult patients who received MSD-HCT with Flu6/Cy2/ATG4 RIC regimen (Flu, 30 mg/m 2 IV for 6 days: Cy, 50 mg/kg IV for 2 days; rabbit ATG, 2.5 mg/kg IV for 4 days) or total nodal irradiation (TNI) of 750 cGy combined with ATG as GVHD prophylaxis (TNI-750/ATG) from March 2002 to March 2021 at Seoul St. Mary's Hospital, Seoul, Korea. BM was the primary graft source, but PBSC was used in donors who refused BM harvest, were unsuitable for general anesthesia, or received TNI-750/ATG conditioning. The primary endpoint of this study was to compare the overall survival (OS), and the secondary endpoints included speed of hematologic recovery, primary or secondary graft failure (GF), and failure-free survival (FFS) between the BM and PBSC group. Results The median patient age in the BM group was 38 years (range, 15 - 59) and 44 years (range, 19 - 64) in the PBSC group (p=0.005). There were no differences of baseline characteristics between the two groups except for a donor-to-recipient sex discrepancy (female to male, BM vs. PBSC; 16.4% vs. 30.9%, p=0.029). The majority of BM group (114/116, 98.2%) received the Flu6/Cy2/ATG4 RIC regimen, while 38.2% (21/55) of PBSC group received TNI-750/ATG for the conditioning (p&amp;lt;0.001). The PBSC contained a median 4.71 (range, 1.22 - 17.03) x 10 6/kg CD34 + cells and 368.82 (range, 25.12 - 1234.70) x 10 6/kg CD3 + cells which were about 1.7-fold (BM 2.80 x 10 6/kg CD34 + cells; range, 0.25 - 10.05) and 10-fold (BM 39.61 x 10 6/kg CD3 + cells; range, 1.34 - 463.68) higher than the BM graft (p&amp;lt;0.001). Consequently, the PBSC group exhibited faster engraftment of neutrophils (median 13 vs. 11 days, p&amp;lt;0.001) and platelets (median 18 vs. 12 days, p=0.012). However, there were no differences in the incidence of secondary GF (19.0% vs. 12.7%, p=0.386) and donor-type aplasia (4.3% vs. 10.9%, p=0.178) between two groups. Furthermore, the incidence of acute grade I-II (8.6% vs. 10.9%, p=0.619) and moderate to severe chronic graft-versus-host disease (GVHD) (3.5% vs. 5.5%, p=0.542) were also not significantly different between two groups. However, the BM group has shown more CMV reactivation (44.0% vs. 24.9%, p=0.005), and higher incidence of respiratory infection (14.7% vs. 3.6%, p=0.037) than those of the PBSC group. The incidences of transplantation-related complications between the BM and PBSC group are summarized in Table. The 10-year OS (93.8% vs. 98.1%, p=0.246) and FFS (65.7% vs. 69.0%, p=0.455) were comparable (Figure). Moreover, there was no significant difference in FFS between BM and PBSC group by potential risk factors of patient and donor age at MSD-HCT, sex incompatibility, ABC mismatch, PNH clone presence, HCT-CI ≥3, infused CD34 + cell count, interval from diagnosis to transplant, prior IST history, heavy transfusion before allo-HCT, or severity of AA. Conclusions Our results suggest that survival outcomes of MSD-HCT showed no difference between BM and PBSC as graft sources, and using PBSC may be an efficient alternative offering faster engraftment without significant difference in graft failure or transplantation-related adverse events such as GVHD, and survival. Current analysis and results were drawn from the Asian population with a fludarabine-based conditioning regimen and therefore, need to validate in the Western population. In addition, well-designed prospective studies in a larger cohort are required to confirm our findings.

Reduced Intensity Condition of ATG Based Haploidentical Hematopoietic Stem Cell Transplantation in Elderly or Unfit Patients

Aims: Reduced-intensity conditioning (RIC) regimens allogeneic hematopoietic stem cell transplantation (HSCT) was developed for older patients or those with poor functional status. Haploidentical donor was appropriate alternative donor for patients without matched donors or patients with emergency disease state. However, there was few studies report the outcomes of RIC regimen of ATG based haploidentical HSCT. The selection of the appropriate RIC regimen based on age and comorbidities in ATG based haploidentical HSCT remains poorly described. To investigate the safety and efficacy of RIC regimen ATG-based haploidentical HSCT in elderly or unfit patients. Additionally, to explore the potential factors that impact the prognosis of RIC regimen of ATG based haploidentical HSCT. Methods: We included a retrospective cohort of 63 patients with hematologic malignant diseases who underwent their first RIC haploidentical HSCT from November 2016 to June 2022 at our institutions. The conditioning regimen involved fludarabine (Flu) 30mg/m²/kg 6 days combined with busulfan 3.2mg/kg 2 days (Bu2) or 3 days (Bu3). Results: The median age of patients in the entire cohort was 60 (32 - 67) years with a median follow-up of 496 (83 - 2182) days. There were 29 patients with AML, 20 patients with MDS, and 14 patients with ALL. The 2-year overall survival (OS) and 2-year disease-free survival (DFS) in whole cohort were 67.7% (95% confidence interval [CI], 53.8% - 85.1%) and 61.4% (95% CI, 48.8% - 77.3%) respectively. The cumulative incidence rates of grades II to IV and grades III to IV acute graft-versus-host disease (aGVHD) in whole cohort were 15.8 % (95% CI, 4.8% - 19.6%) and 9.7 % (95% CI, 0.0% - 11.8%) respectively. The 2-year cumulative incidence of chronic GVHD was 34.0% (95% CI, 18.9% - 46.3%). The 2-year cumulative incidence rates of relapse (IR) and non-relapse mortality (NRM) rates in whole cohort were 27.5% (95% CI, 14.5% - 33.7%) and 11.6% (95% CI, 2.2% - 21.9 %) respectively. The probability of 2-year OS were 60.2% (95% CI:42.5%-85.3%) in Bu2 and 85.5%（95% CI:73.0%-100%) in Bu3 group respectively(P=0.150). The probability of 2-year DFS were 49.7% (95% CI:33.0%-74.8%) in Bu2 and 72.6% (95% CI:55.5%-95.5%) in Bu3 group respectively (P=0.045). The 2-year IR or 2-year NRM were not significantly different between Bu2 and Bu3 group(P&amp;gt;0.05). In multivariable analysis, RIC regimen of Bu3 had superior DFS and lower RI than Bu2 group respectively [HR 0.41, 95% CI 0.16-1.01; P=0.05; HR 0.33, 95% CI 0.11-0.99; P=0.047]. Conclusion: The RIC regime of ATG based haploidentical HSCT is a safe and effective treatment option for patients who are elderly or have poor functional status, making them unable to tolerate intensive chemotherapy. In particular, a relatively high-intensity pre-treatment regimen consisting of Bu achieves significant improvements in DFS, thus providing more favorable post-transplantation clinical outcomes.

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.

Outcomes of Hematopoietic Cell Transplantation for Patients with Refractory Cytopenia with Multilineage Dysplasia: A Comparison Children with Adolescents and Young Adults

Background: The 2008 World Health Organization (WHO) classification proposed a new entity in childhood myelodysplastic syndrome (MDS), refractory cytopenia of childhood (RCC). The spectrum of patients with RCC is wide, ranging from patients with severe hypocellular bone marrow (BM) and mild dysplasia (hypocellular RCC) to those with normocellular BM and distinct dysplasia meeting the criteria for refractory cytopenia with multilineage dysplasia (RCMD) defined for adults with MDS. The term of RCMD was revised to MDS with multilineage dysplasia in the 2017 WHO classification. In Japan, children who meet the criteria for RCMD have been diagnosed as RCMD distinguished from hypocellular RCC. Although hematopoietic cell transplantation (HCT) is a curative treatment for RCMD in children, there have been few reports of the outcomes of HCT for children with RCMD. Patients and Methods: To clarify the outcomes of HCT for children with RCMD, we retrospectively analyzed the clinical data in children (&amp;lt;16 years) with RCMD who underwent the first HCT from 2010 to 2021 and registered in the Japan Society for Hematopoietic Cell Transplantation Registry, and compared with those in adolescents and young adults (AYA; ≥16, &amp;lt;40 years) with RCMD who underwent the first HCT during the same study period. During the study period, 195 patients with RCMD (children, 69; AYA, 126) underwent HCT. The stem cell source was BM in 138 (children, 58; AYA, 80), peripheral blood (PB) in 27 (children, 2; AYA, 25), and cord blood (CB) in 30 patients (children, 9; AYA, 21). Myeloablative conditioning (MAC) regimen was defined as the use of total body irradiation (TBI) ≥8 Gy (MAC-TBI) and the administration of busulfan (BU) &amp;gt;8 mg/kg (MAC-BU). All other regimens were included in reduced intensity conditioning (RIC) regimen. Results: We retrospectively analyzed 195 patients with RCMD (male, 105; female, 90). The median age at HCT was 8 years (range, 0-15) in children and 29 years (range, 16-39) in AYA. Of the 195 patients, 20 (29%) and 52 (41%) had abnormal karyotypes in children and AYA, respectively. Of the patients who underwent HCT, 68 were from related (children, 22; AYA, 46), and 127 from unrelated (children, 47; AYA, 80) donors. MAC-BU was used for 46 (children, 9; AYA, 37), MAC-TBI for 51 (children, 1; AYA, 50), and RIC for 98 (children, 59; AYA, 39) patients. Of the 195 patients, 8 (children, 3; AYA, 5) developed primary graft failure, 16 (children, 5; AYA, 11) secondary graft failure, 10 (children, 3; AYA, 7) disease relapse, and 11 (children, 2; AYA, 9) secondary tumor. Twenty-four (children, 5; AYA, 19) patients died of HCT-related complications and four AYA of disease relapse. The 5-year overall survival (OS) rate was significantly higher in children (93%) than in AYA (82%) (p = 0.04). The 5-year event-free survival (EFS) rate was 76% in children and 64% in AYA. The 1-month cumulative incidence (CI) of neutrophil engraftment was 93% in children and 94% in AYA. The 5-year CI of relapse was 6% in AYA and 2% in children. The 5-year CI of treatment-related mortality (TRM) was 16% in AYA and 7% in children. The 5-year CI of graft failure was 12% in children and 12% in AYA. The 3-year CI of chronic graft-versus-host disease (GVHD) was significantly higher in AYA (37%) than in children (21%) (p = 0.04), while there was no difference in the 3-month CI of acute GVHD (gradeⅡ-Ⅳ) between children (35%) and AYA (39%). In children, the 5-year OS and EFS rates were significantly lower in CB (67% and 42%) than in BM/PB (97% and 81%) (p &amp;lt; 0.01 and p &amp;lt; 0.01), respectively, while the 5-year OS and EFS rates were not different between CB (91% and 76%) and BM/PB (80% and 62%) in AYA, respectively. Of the 59 children who underwent HCT using RIC, 43 without abnormal karyotypes showed 95% and 16 with abnormal karyotypes showed 88% in the 5-year OS rate. Even in AYA, there was no difference in the 5-year OS rate between RIC and MAC in both groups with (RIC, n = 14, 76%; MAC, n =38, 72%) and without (RIC, n = 25, 81%; MAC, n = 49, 90%) abnormal karyotypes. Conclusions: HCT for children with RCMD showed better OS rate than that for AYA with RCMD. HCT using RIC regimen provided good outcomes for RCMD in children with or without abnormal karyotypes. Even in AYA, HCT using RIC regimen showed OS rate comparable to MAC regimen in both groups with and without abnormal karyotypes.

Safety and Efficacy of Azacitidine and Chidamide Maintenance after Allogeneic Hematopoietic Stem Cell Transplantation for Patients with High-Risk Acute Myeloid Leukemia: Interim Analysis of a Prospective, Multicenter, Single-Arm, Phase Ⅱ Clinical Trial

Background Although allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the potentially curative therapy for AML, the relapse rate after HSCT is high with 30-60% for patients with high-risk AML. Maintenance therapy with efficacy and low toxicity is needed to mitigate relapse. It has been reported that histone deacetylases inhibitor chidamide exhibits anti-tumor activity against AML cells, and is able to elicit anti-tumor immune response in mouse models. However, efficacy and safety of chidamide as maintenance therapy following allo-HSCT for patients with AML have not been reported. Therefore, we designed a multicenter, single arm, phase II clinical trial for high-risk AML patients to use azacitidine combined with chidamide as maintenance therapy post allo-HSCT to prevent relapse. Methods In this multicenter, single arm, phase II clinical trial, patients aged 18-60 years with high-risk AML, defined as the European LeukemiaNet (ELN) 2017 adverse risk group, refractory, relapsed or secondary AML were given AZA and chidamide as maintenance therapy after 60 days post transplantation (NCT05270200). AZA was given at 100mg/day (days 1-5) for 6 cycles and chidamide 5mg daily (days 1-28) with a cycle of 28 days for up to 2 years. The dose of AZA was amended at 50mg/m 2/day (days 1-3) from Dec 23,2022 due to occurrence of thrombocytopenia. If PLT was below 50×10 9/L or grade 3/4 non-hematological toxicity occurs, maintenance should be interrupted or delayed until PLT count was greater than 75×10 9/L or the non-hematological toxicity resolved to ≦ grade 1. Primary objectives were safety and one year cumulative incidence of relapse. Secondary objections were relapse-free survival (RFS), overall survival (OS) and incidence of severity of acute and chronic graft-versus-host disease (GVHD). Results From February 12,2022 to June 30,2023, seven patients were enrolled, with a median age of 46 years（28-60), four patients (57%) were female. One patient (14%) received matched sibling donor transplantation, six patients (86%) received haploidentical donor transplantation. Five patients (71%) received myeloablative and 2/7 (29%) reduced intensity conditioning regimen. Six (86%) were in ELN 2017 adverse risk with three patients harboring KMT2A rearrangement, one patient with TP53 mutation, one patient with -7, one patient with RUNX1 mutation, while one patient (14%) was diagnosed as secondary AML with broad extramedullary infiltration. All but one patients entered transplant in CR, while five patients (83%) were MRD negative and one patient (17%) were positive. The baseline patient characteristics are summarized in Table1. Outcome data were updated as of June 30,2023 (Figure1). The median time to start maintenance therapy after transplantation was 77 days (range 64-80). The median follow-up time was 9.9 months, only one patient relapsed and the accumulative incidence of relapse of one year was 16.7%（95%CI,0.4%-64.1%). The relapsed patient diagnosed with MLL-AF10 rearrangement had extramedullary infiltration of left tonsil, gum and neck lymph nodes at 197 days post transplantation while bone marrow remained in MRD negative remission. AZA/chidamide were well tolerated, with no severe adverse event was recorded. Two grade 3/4 non-hematologic adverse events were observed, with one increased bilirubin due to cGVHD and one pneumonia. Two patients (29%) experienced grade4 thrombocytopenia requiring platelet transfusion. After amendment of AZA dose, no grade4 thrombocytopenia was recorded. No one discontinued treatment due to toxicity. During follow-up, none of patients had aGVHD. Three patients (43%) experienced mild or moderate cGVHD, no severe cGVHD was observed. The median OS was not reached, with six months and one year OS both of 100%. The median RFS is not reached, with six months and one year RFS of 100% and 83.3%(95%CI,35.9%-99.6%). Conclusions Preliminary results suggest that maintenance of AZA combined with chidamide post allo-HSCT in patients with high-risk AML exhibits promising efficacy and well-tolerated. Recruitment of patients with high-risk AML post allo-HSCT for this trial is ongoing. Disclosures No relevant conflicts of interest to declare.

HLA 1 Allele-Mismatched Unrelated Vs Haploidentical Donor Transplants in Acute Myeloid Leukemia

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the curative treatment for acute Myeloid Leukemia (AML) patients. When there is no HLA-identical sibling or unrelated donor, alternative donors such as 1 allele-mismatched unrelated donors (1-MMUD) or haploidentical donors (HID) may be considered. While there have been reports that the outcomes of these two donors are comparable with those of HLA-matched unrelated donors, there is limited data directly comparing the outcomes between 1-MMUD and HID transplantation. Therefore, we conducted an analysis of the outcomes of allo-HSCT from 1-MMUD and HID in AML patients. This study is a retrospective cohort study at a single institution, including patients with AML who underwent first allo-HSCT in complete remission (CR) or CR with incomplete hematologic recovery between 2002 and 2022, from 1-MMUD or HID. For HID transplantation, patients were administered fludarabine 30mg/BSA for 4 days, intravenous busulfan 3.2mg/kg for 2 days, and depending on the condition, they received either total body irradiation (TBI) at 400cGy or fractionated TBI at 800cGy (400cGy for 2 days). Graft-versus-host disease (GVHD) prophylaxis for HID transplantation consisted of antithymocyte globulin total 5.0mg/kg, methotrexate 5mg/BSA 3 or 4 times, and calcineurin inhibitors. In 1-MMUD transplantation, various myeloablative or reduced-intensity conditioning regimens were used. All patients received T-cell replete peripheral blood stem cells. A total of 108 patients who underwent 1-MMUD transplantation and 447 patients who underwent HID transplantation were included. The 1-MMUD group showed a tendency to be younger (median 42 years vs. 51 years, Wilcox rank-sum test p &amp;lt; 0.01) and had a lower proportion of ABO-matched transplantations (28.7% vs. 51.7%, Chi-square test p &amp;lt; 0.01). Other patient characteristics were similar between the two groups. In terms of survival, the median OS in the 1-MMUD group was 60.1 months, and in the HID group was 58.7 months, showing no significant difference between the two groups (Log rank test p = 0.81). Similarly, the median RFS was 54.8 months in the 1-MMUD group and 40.9 months in the HID group, with no statistically significant difference (Log rank test p = 0.96). The cumulative incidence of relapse and NRM at 60 months after allo-HSCT showed no significant difference between the two groups, with 26.1% and 25.7% for relapse and 23.9% and 26.3% for NRM in the 1-MMUD and HID groups, respectively (Gray's test p for relapse: 0.81, p for NRM: 0.82). Although the cumulative incidence of grade 2 or higher acute GVHD did not show a significant difference between the two groups (38.0% in 1-MMUD, 45.4% in HID, Gray's test p = 0.41), the incidence of chronic GVHD was significantly higher in the HID transplantation group (63.6%) compared to the 1-MMUD transplantation group (52.0%) (Gray's test p &amp;lt; 0.01). Finally, in a multivariate Cox model In conclusion, both 1-MMUD and HID can be considered equivalent alternative donors, and caution should be exercised regarding the occurrence of chronic GVHD in HID transplantation. Further comparisons between the two donors, including in different settings such as post-transplantation cyclophosphamide, warranted.

Evaluation of the Impact of the Disease Risk Index and Pre-Transplant Measurable Residual Disease By Flow Cytometry As Prognostic Factors in Allogeneic Hematopoietic Cell Transplantation in Patients with Acute Myeloid Leukemia

Introduction: Allogeneic hematopoietic cell transplantation (HCT) is the therapy with the best curative potential for patients with intermediate/high-risk acute myeloid leukemia (AML). Although many factors may influence the outcomes of allogeneic HSCT, risk stratification and disease status at the time of transplant are two of the strongest prognostic factors of post-transplant survival². In this context, the Disease Risk Index (DRI) was developed and validated in a cohort of more than 13.000 patients and stratifies patients into 4 groups with different overall survivals (OS)². Measurable residual disease (MRD) is also an important and consolidated biomarker for the prognosis, monitoring, and treatment effectiveness evaluation³. Objective: To compare the impact of the pre-transplant DRI and MRD in patients with AML in OS and leukemia-free survival of patients treated with allogeneic HSCT in a private institution in Brazil from January 2017 to May 2023. Methods: This is a retrospective, unicentric study. MRD was evaluated immediately before transplantation by 10-color flow cytometry and was considered positive if ≥0.1%. DRI was grouped into two groups: low/intermediate risk and high/very high risk. Statistical analyzes were performed using the Cox regression model. Results: With a median follow-up of 18 months, a total of 57 patients were included, 34 of whom had negative MRD and 23, positive. The mean ages in these groups were 55 and 60 years, respectively. HCT-CI was 0-2 in 91% of the patients in the MRD-negative group, and in 78% of the MRD-positive group. The type of donors was similar in both group (MRD positive or negative): 20-30% of related donors, 25-40% of haploidentical and 40-45% unrelated donors. The reduced-intensity conditioning regimen (RIC) was the used in 70% of the patients. In the MDR + group, peripheral stem cell source was more used than in the MDR negative group. In univariate analysis, DRI had an impact on overall survival (OS) with an HR=3.52 (95%CI 1.46 - 8.5) and p=0.075 for low/intermediate risk compared with high/very high risk, while in the multivariate analysis this impact was not maintained with HR=2.31 (95%CI 0.92 - 5.82) and p=0.075. A pre-transplant positive MRD was a risk factor for death in univariate analysis, with an HR=5.99 (95%CI 2.93- 26.82) and p&amp;lt;0.001. The impact of MRD HR 8.87 (2.93 - 26.83) and p &amp;lt; 0.001, age HR 1.09 (1.04 - 1.15) with p = 0.001 and bone marrow source HR 0.29 (0.08 - 1.06) are prognostic factors even when controlled for age, cell source and type of transplant. One-year overall survival in the MRD-negative group was 90% (79-100%), and 53% (36-80%) in the MRD-positive group. Additionally, one-year leukemia-free survival in the MRD-negative group was 70% (55-89%) and 45% (28-72%) in MRD-positive. Conclusion: Our results show that both DRI and pre-transplant MRD may have an impact on OS and LFS, although pre-transplant MRD seemed to perform better than DRI in multivariable analysis in patients with acute myeloid leukemia undergoing hematopoietic cell transplantation.

A Multicentre, Randomized, Double-Blinded, Phase 2b Study Evaluating the Efficacy and Safety of MaaT033, an Oral, Pooled Microbiome Ecosystem Therapy in Patients Undergoing Allogenic Hematopoietic Cell Transplantation to Improve Overall Survival: The Phoebus Trial

Background and significance: Allogenic hematopoietic cell transplantation (alloHCT) is a well-established therapy for various life-threatening hematologic malignancies. The use of alloHCT is constantly increasing, with nearly 20 000 transplantations reported to the European Society for Blood and Marrow Transplantation (EBMT) per year. However, this treatment is limited by high morbidity and mortality, mainly related to relapse, infection, graft-versus-host disease (GvHD), and conditioning-related toxicity. Several pioneering studies have shown that the diversity of the gut microbiota of patients not only correlates with the occurrence of medical complications after alloHCT, including GvHD (Jenq et al. 2012, Stein-Thoeringer et al. 2019) and bloodstream infections (Taur et al. 2012), but also with relapse of the underlying disease (Peled et al. 2017). Gut microbiota diversity restoration with fecal microbiotherapy could be an effective treatment to improve patients' clinical outcomes including overall survival (OS) after alloHCT, through the prevention and resolution of gut microbiota dysbiosis. MaaT033 is a freeze-dried, full-ecosystem, high-diversity, fecal microbiota medicinal product, formulated as delayed-release capsules and derived from pooled allogenic human fecal material. The PHOEBUS trial is a phase 2b study to evaluate the efficacy of MaaT033 in improving survival of adult alloHCT patients (Clinicaltrials.gov identifier: NCT05762211) Study design and Methods: 387 subjects aged ≥ 50 years with hematologic malignancies for which an alloHCT is indicated will be randomized 1:1 to receive either MaaT033 (experimental arm) or placebo (control arm) before initiation of the conditioning regimen and after hematopoietic recovery following alloHCT. Stratification of patients will be performed based on disease risk index (low-intermediate versus high-very high) and donor-host compatibility (HLA-identical versus HLA-mismatch). Inclusion criteria include age ≥ 50 years, alloHCT with a reduced-toxicity or reduced-intensity conditioning regimen, neutrophils &amp;gt; 0.5 G/L, and administration of broad-spectrum antibiotics within the last 90 days prior to inclusion. Exclusion criteria comprise non-myeloablative conditioning regimen, conventional myeloablative conditioning regimen, in-vitro T-cell depletion, alloHCT with cord blood cells, alloHCT from an unrelated donor with ≥ 3/10 HLA-mismatches, use of alemtuzumab, vedolizumab or abatacept for GvHD prophylaxis, history of chronic digestive disease. The primary endpoint is to evaluate OS at 12 months after randomization. Secondary endpoints will include evaluation of the safety of MaaT033, GvHD-free survival, cumulative incidence of acute GvHD and chronic GvHD, non-relapse mortality, relapse-free survival, GvHD-free, relapse-free survival, the proportion of patients with severe infections, gut microbiota composition, and quality of life. Exploratory endpoints will describe the impact of MaaT013 on immune recovery, the nutritional status of the patients, and resource utilization. Patients will receive MaaT033 or placebo (3 capsules per day) for 1 week before the start of the conditioning regimen. Experimental treatment (3 capsules per day) will be resumed at neutrophil recovery and pursued up to 90 days after alloHCT. Patients will be followed monthly up to 6 months post alloHCT and then every 3 months up to 12 months. The study is approved in France and Germany; expansion to other countries is planned for 2024. Study start is expected in September 2023.

Pre-Graft Immune Status Predicts Survivals and Relapse in Adults Receiving Matched Peripheral Blood Stem Cell Allotransplants for Myeloid Malignancies

Background The impact on outcomes of pre-graft immune status has not been explored so far in recipients of allogeneic stem cell transplant (allo-SCT). Patients and Methods This was a retrospective and monocentric study including all consecutive adults who underwent a peripheral blood stem cell (PB) allo-SCT for a hematological malignancy between May 2017 and December 2021 in our Hematology Department. Immune status was routinely evaluated before transplant in each patient. Absolute lymphocyte (ALC) and monocyte counts were obtained from complete blood counts, while absolute counts of lymphocyte subsets (CD3+, CD4+ and CD8+ T cells, B and NK cells) were assessed by multiparameter flow cytometry, and gamma globulin levels by standard serum electrophoresis. We evaluated the impact of these parameters, considered as continuous variables, on overall survival (OS), progression-free survival (PFS), graft-versus-host disease (GVHD)-free, progression-free survival (GRFS), non-relapse mortality (NRM), and relapse incidence (RI), according to the type of the disease (myeloid vs. lymphoid) and the type of the donor (matched vs. haploidentical). Results This study included 264 patients with a median age of 59 years old (range 20-73, Table). A majority had a myeloid malignancy (75%, n=196) and received a graft from a matched donor (64%, n=170, sibling n=46; matched unrelated n=124) and a reduced-intensity conditioning regimen (80%, n= 211). Almost all (96%) patients with a matched donor received anti-thymoglobulin as GVHD prophylaxis while it was the case for 79% of those receiving a graft from a haploidentical donor. With a median follow-up of 32 months estimated by reversed Kaplan Meier analysis, 3-year (y) OS, PFS, and GRFS were respectively 53%, 46% and 31%, while 3-y NRM and RI were 28% and 25%, for the whole cohort. Pre-graft immune status was evaluated at a median of 20 days before transplant, showing significant higher median T and B cell counts and gamma globulin level in patients with myeloid malignancy, reflecting probably the less immunosuppressive intensity of chemotherapies received before transplant ( Table). Considering myeloid malignancies, OS and NRM were not impacted by the pre-graft immune status. In multivariate analysis, adjusting for disease type, status, donor type (sibling versus [vs] unrelated), and conditioning (RIC vs MAC vs sequential), a higher ALC was associated with significant lower PFS (hazard ratio [HR] 1.39, 95%CI: 1.11-1.74, p=0.004) and GRFS (HR: 1.30, 1.07-1.59, p=0.009), and a significant higher risk of relapse (HR 1.85, 1.32-2.59, p=&amp;lt;0.001), but this was true only in case of a matched transplant. Interestingly, T-cell subsets were associated with relapse (CD3: HR 1.94, p&amp;lt;0.001; CD4: HR 2.34, p=0.004; CD8: HR 2.34, p&amp;lt;0.001), but not B-cells (HR 2.23, p=0.56), gamma-globulin levels (HR 0.98, p=0.68), nor NK-cells (HR 2.72, p=0.17). T cell subsets, B cells, NK cells, gamma-globulin and monocytes were not associated with PFS and GRFS. Also, to highlight the adverse effect of an elevated ALC, and using a ROC curve, a threshold of 1.23 Giga/L was retained as the best cut-off to predict relapse. This was then applied to create a visual comparison of PFS, GRFS and RI ( Figure), revealing an early increased RI in patients with ALC &amp;gt; 1.23 Giga/L (3-month relapse rate: 13% vs 2.3%, p=0.03). Finally, the pre-graft immune status did not impact the outcomes of patients receiving a PB haplotransplant for a myeloid malignancy. This was true also for those who received a PB matched or again a haploidentical transplant for a lymphoid disease. Conclusions This retrospective analysis suggests that higher ALC at transplant predicts lower PFS and GRFS due to higher RI in adults receiving a PB matched transplant for a myeloid malignancy. Patients with a myeloid malignancy had also a better immune status at transplant which may reflect less immunosuppressive treatments received before transplant. Paradoxically, this better immune status may interfere with allogeneic T lymphocytes by reducing the graft-versus-leukemia effect. Thus, increasing immunosuppression (via the conditioning or drugs used for GVHD prophylaxis) may improve outcome in some specific sub-groups of patients with higher autologous T lymphocytes at transplant.

Higher CD34+ Cell Doses Correlate with Reduced Incidence of Relapse and Better Event-Free Survival after KIR-Ligand Mismatch Cord Blood Transplantation for Childhood Acute Myeloid Leukemia

Introduction In children with acute myeloid leukemia (AML), hematopoietic stem cell transplantation (HSCT) is an important treatment, and cord blood units from unrelated donors provide a well-established source of stem cells for HSCT. The main advantages of using cord blood include rapid availability, allowance of greater HLA disparities due to a relatively low risk of severe graft-versus-host disease (GVHD), and possibly a greater graft-versus-leukemia (GVL) effect. Killer cell immunoglobulin-like receptors (KIRs) are the main receptors on natural killer cells that play an important role in GVL after HSCT. Previous studies on the effects of KIR-ligand (KIR-L) incompatibility in unrelated cord blood transplantation (CBT) for leukemia have resulted in conflicting results, and in some studies, this has led to an increased incidence of acute GVHD. Furthermore, the impact of KIR-L mismatch on outcomes in children with AML remains poorly understood. In this study, we explored the association of KIR-L incompatibility and other clinical factors with patient outcomes in children with AML who received CBT. Methods Data were collected from the Transplant Registry Unified Management Program sponsored by the Japanese Society for Transplantation and Cellular Therapy and the Japanese Data Center for Hematopoietic Cell Transplantation. The patients were selected according to the following criteria: (1) de novo non-M3 AML, (2) age &amp;lt; 16 years and CR1 or CR2 at the time of receiving HSCT, (3) no prior HSCT, and (4) HSCT performed between 2000 and 2021. Patients without information on survival and disease recurrence or those with Down syndrome were excluded. KIR-L mismatch in the graft-versus-host direction was defined as lacking a donor KIR-L group (HLA-C1, C2, Bw4, or A3/A11) in a recipient. A myeloablative conditioning regimen was defined as total-body irradiation (TBI) at &amp;gt; 8 Gy, melphalan at &amp;gt; 140 mg/m 2, or busulfan at ≥ 9 mg/kg. All other regimens were analyzed as reduced-intensity conditioning regimens. Adverse cytogenetics were defined as previously described [Creutzig et al. Blood, 2012]. Results A total of 299 patients were included. The median age at HSCT was 5 years (range, 0-15), and the median follow-up period for survivors was 7.2 years (range, 0.1-22.4). The median total nucleated cell and CD34+ cell doses were 6.7 x 10 7/kg (range 0.01-12.3) and 1.9 x 10 5/kg (range 0.01-59.4), respectively. The study cohort consisted of 240 patients in the KIR-L match group and 59 patients in the KIR-L mismatch group. The background characteristics of these two groups did not differ significantly, except for a trend indicating that the KIR-L mismatch group received CBT more recently ( p = 0.063). The cumulative incidence rates of neutrophil recovery at Day 42 were 93.3% (95% CI, 89.3-95.9%) and 91.5% (95% CI, 80.0-96.5%) ( p = 0.980), and the cumulative incidence rates of platelet engraftment at 6 months were 91.5% (95% CI, 87.1-94.5%) and 89.8% (95% CI, 77.9-95.5%) ( p = 0.314) for the KIR-L match and mismatch groups, respectively. The cumulative incidence rates of grade II-IV acute GVHD at Day 100 were 40.9% (95% CI, 34.6-47.1%) and 40.7% (95% CI, 28.0-52.9%) ( p = 0.709), whereas those of chronic GVHD at one year after transplantation were 15.6% (95% CI, 11.2-20.6%) and 15.9% (95% CI, 7.8-26.6%) ( p = 0.914) for the KIR-L match and mismatch groups, respectively. In univariate analyses, the 5-year event-free survival (EFS) was 70.1% (95% CI, 63.6-75.6%) for the KIR-L match group and 72.9% (95% CI, 59.0-82.8%) for the KIR-L mismatch group ( p = 0.609). Stratification by CD34+ cell doses showed a significant correlation between higher CD34+ cell doses and better EFS in the KIR-L mismatch group (Figure 1), attributed not only to reduced nonrelapse mortality but also to a lower incidence of relapse. In multivariate analysis of EFS, KIR-L mismatch with high CD34+ cell doses (&amp;gt; the median doses) was identified as an independent favorable prognostic factor (Table 1; hazard ratio = 0.21, p = 0.037). Conclusion Our study demonstrates that higher CD34+ cell doses were associated with a lower relapse rate and better EFS in KIR-L mismatch CBT for childhood AML. This finding is noteworthy, as previous literature has primarily emphasized the role of higher CD34+ cell doses in reducing nonrelapse mortality. Our results suggest that higher CD34+ cell doses are also crucial for achieving a high GVL effect in the context of KIR-L mismatch CBT.

Impact of Conditioning Intensity and Regimen on Outcomes after Unrelated Cord Blood Transplantation for Patients with Myelodysplastic Syndrome

Introduction Allogeneic hematopoietic stem cell transplantation (allo-HSCT) provides curative outcomes in patients with myelodysplastic syndromes (MDS). Unrelated cord blood transplantation (CBT) is an alternative donor option in MDS patients who lack an HLA-matched donor, and the increased availability of CBT expand indications for allo-HSCT in MDS patients. Because concerns have been expressed regarding decreased hematopoietic recovery and increased relapse after CBT, many studies have been conducted to develop the conditioning regimen in CBT. The optimal intensity of conditioning regimen needs to be addressed based on patient- and disease-related factors. However, the optimal intensity of conditioning regimen in CBT for MDS remains unclear. We here conducted a nationwide retrospective study to clarify the optimal conditioning intensity for MDS in CBT. Methods This study included patients diagnosed with de novo MDS according to the WHO classification. The clinical data of 856 de novo MDS patients (i) who were 16-69 years old and (ii) who underwent their initial single-unit CBT between 2001 and 2020 were collected from the Japanese Data Center for Hematopoietic Cell Transplantation. Cox proportional hazards regression models were used to evaluate variables potentially affecting overall survival (OS), chronic graft-versus-host disease (GVHD)- and relapse-free survival (CRFS), and GVHD- and relapse-free survival (GRFS). Fine and Gray proportional hazards models were used to evaluate variables potentially affecting cumulative incidences of relapse (CIR) and non-relapse mortality (NRM), using cumulative incidence curves to accommodate competing events. Results In this study, 501 and 355 patients received myeloablative conditioning (MAC) and reduced-intensity conditioning (RIC), respectively. The median age at CBT was 53 (range,17-69) and 62 years (range,18-69) in MAC and RIC groups, respectively. The most frequently used MAC regimen consisted of total body irradiation &amp;gt;8 Gy-based regimen (n=209, 41.7%), followed by fludarabine (Flu) with myeloablative doses of busulfan (Bu 9.6 to 12.8 mg/kg)-based regimen (n=93, 18.6%). The most frequently used RIC regimen consisted of Flu with reduced doses (80 to 120 mg/m 2) of melphalan-based regimen (n=245, 96.1%), followed by Flu with reduced doses of Bu (6.4 mg/kg)-based regimen (n=63, 17.7%). The 3-year OS were 44.3 % and 48.8 % in MAC and RIC groups, respectively; the 3-year CRFS were 33.8 and 37.2%; the 3-year GRFS were 19.2 % and 26.9%; the 3-year CIR were 27.1% and 30.0%; and the 3-year NRM were 18.6% and 18.2 %. The univariate analysis revealed that RIC group tended to correlate with higher GRFS than MAC group (Hazard ratio (HR) 0.86 [95% confidential interval 0.74-1.00]; P=0.057), but there was no significant difference of OS (HR 0.95 [0.79-1.13]; P=0.552), CRFS (HR 0.95 [0.80-1.12]; P=0.522), CIR (HR 1.11 [0.87-1.41]; P=0.401) and NRM (HR 0.96 [0.77-1.20]; P=0.735) between MAC and RIC groups. The multivariate analyses confirmed the better GRFS in RIC group than MAC group (HR, 0.73 [0.61-0.89]; P=0.001). Apart from the conditioning intensity, the following six factors were associated with worse overall mortality: patient's age (40-60 years; P=0.039 and &amp;gt;60 years; P&amp;lt;0.001), patient's sex (male; P=0.038), performance status (PS) at CBT (PS 2-4; P=0.033), hematopoietic cell transplantation-specific comorbidity index (HCT-CI) (HCT-CI ≥3; P=0.035), high number of platelet transfusion before HSCT (≥20 times; P&amp;lt;0.001) , and cytogenetic risk group (poor risk; P=0.001). We next performed the subgroup analysis stratified by the patient's characteristic affecting OS, such as age, sex, PS, HCT-CI, the number of platelet transfusion, and cytogenetic risks. The subgroup analysis showed the better OS (HR, 0.74 [0.59-0.92]; P&amp;lt;0.007), CRFS (HR 0.74, [0.60-0.94]; P=0.012), and GRFS (HR 0.62, [0.50-0.78]; P&amp;lt;0.001) of RIC group than MAC group among patients with patients aged &amp;gt;60 years, but no significant impact on CIR and NRM. Conclusion This study showed no significant difference of OS, CRFS, CIR and NRM between MAC and RIC groups, but RIC group correlated with better GRFS in the entire population. Furthermore, the subgroup analysis showed that RIC regimen may be preferable for patient aged &amp;gt;60 years. These findings would improve the management for CBT candidates with MDS.