Graft-versus-host Disease Grade Research Articles

Higher Proportions of Monocytic-Myeloid-Derived Suppressive Cells (mMDSC) before Allotransplant Predict Relapse in Acute Leukemia Patients

Introduction: Myeloid-derived suppressive cells (MDSC) are an heterogeneous group of immature myeloid cells with strong immunosuppressive activities which made them of particular interest in the context of allogeneic stem cell transplant (Allo-SCT). In mice models, MDSC modulate the function of alloreactive T cells and prevent graft versus host disease (GVHD) without impairing graft versus leukemia (GVL) effect. Data are limited in humans, but higher proportions of MDSC in the graft seem to protect against both acute and chronic GVHD. However, the influence of circulating MDSC is not fully explored especially regarding their impact on post-transplant GVL effect and survivals. Here we focused on the role of peripheral levels of monocytic-MDSC (mMDSC) in a cohort of adults with acute (both myeloid or lymphoid) leukemia (AML or ALL) having received Allo-SCT. Methods: This prospective monocentric study aimed at documenting the impact of the percentage of mMDSC before and after allo-SCT in terms of incidence of acute and chronic GVHD, overall (OS) and leukemia-free (LFS) survivals, (grade 3/4 acute or extensive chronic) GVHD-free relapse-free survival (GRFS), relapse and non-relapse mortality (NRM) in a cohort of ALL or AML patients (pts). Inclusion was performed after informed consent at diagnosis as part of a more global study (Abstract ASH 2021 # 3465), pts who were ultimately transplanted being included in this sub-group analysis. mMDSC were defined by the minimal CD14+/CD11b+/CD33+/HLA-DR-/low immunophenotypic pattern, at variance from granulocytic MDSC that lack CD14 and express bright CD15. Cells were assessed in a lysis-no-wash flow cytometry technique using peripheral blood collected on EDTA before conditioning then at day+60 post-transplant. Data acquisition was performed on a Navios® flow cytometer (Beckman Coulter, Miami, FL). mMDSC were expressed as a percentage (%) of total nucleated cells defined as CD45+. The study was registered at the French Commission Nationale de l'Informatique et des Libertés as CNIL 2016-038 and approved by the Ethic Review Board of Nantes University Hospital. Results: Among 73 AML and 14 ALL pts included at diagnosis, 47 and 9, respectively, were ultimately allografted between February 2018 and October 2021. Pts characteristics are provided in Table 1A. The median follow-up for alive pts from Day 0 was 24 months (range: 8-48). Considering the whole cohort, 2-year OS, LFS and GRFS were 61.9+6%, 55.9+7% and 32.4+6%, respectively, while 2-year NRM and Relapse incidence were 11+4% and 29.6+6%. In pre-graft, 46 pts were evaluated at a median of 20 days from Day 0 (range: 6-83). The median % of mMDSC was 0.45% (range: 0-11.85) with no differences between AML and ALL (p=0.32). The best cut-off assessed by ROC analyses was 0.47%. According to this value, the incidence of cytologic relapse at 2 years was significantly higher in pts with >0.47% of mMDSC (14.5+8% vs 44.4+11%, p=0.02, Figure 1) while no impact on survivals, NRM or GVHD was observed. Of note, the incidence of relapse was similar between AML and ALL (29% vs 37.5%, p=0.95). In multivariate analysis (Table 1B), higher pre-graft mMDSC % remained associated with higher risk of relapse (HR: 3.71; 95%CI: 1.05-13.09, p=0.04). At day+60, 42 pts were evaluated. The mMDSC median level was 0.52% (range: 0-5.03) with no differences between AML and ALL (p=0.32). No best cut-off was determined. Survivals were similar between pts with ≤ or >0.52% of mMDSC at this time. It was also the case for incidences of relapse, NRM and chronic GVHD. However, the incidence of severe acute GVHD (grade 3/4) was significantly and paradoxically higher in the group of pts with >0.52% mMDSC (33% vs 5%, p=0.04) suggesting a possible amplification of immunosuppressive mMDSC as a reaction to GVHD since the median time of GVHD grade 2-4 occurrence was 30 days (range: 20-123) post-transplant. Of note, the kinetics (increases or decreases of mMDSC %) between pre-graft and D60 had no influence on outcomes. Conclusion: This prospective study demonstrates a negative impact of higher proportions of mMDSC before allotransplant in leukemic pts. This higher proportion is predicting relapse, suggesting a protective role and tolerance of tumoral cells by mMDSC themselves. This paves the way to therapeutic intervention to decrease the incidence of relapse in such pts. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Haploidentical Hematopoietic Stem Cell Transplant Plus Add-Back NK Cells in Pediatric High-Risk ALL

Introduction: Natural killer (NK) lymphocytes are cells of innate immunity that protect against tumor and infections. NK cells recognize self and non-self HLA class I ligands, are regulated by a balance between activator and inhibitory signals through surface receptors, and can interact with HLA class I molecules on target cells. Killer-cell Immunoglobulin-like Receptors (KIRs) are inhibitory molecules expressed on NK cells and belong to the immunoglobulin superfamily. KIRs function to "educate" NK cells in effective defense against unhealthy self/non-self cells and tolerance against healthy self cells. NKs are thought to play a key role in preventing early relapse of hematologic malignancies, virus infection and graft versus host disease (GvHD) after haploidentical hematopoietic stem cell transplantation (haplo-HSCT).In B-/T-cell alpha/beta depleted haplo-HSCT, donor-versus-recipient allo-reactive NK cells can exert an efficient graft versus leukemia (GvL) effect, mediated by inhibitory KIRs where the HLA ligand is missing on recipient cells. Donor NK cells after haplo-HSCT are "immature" and not effective as the mature NKs. These immature NK cells are CD56bright, are derived from CD34+ stem cells, and mature to a CD56dim phenotype. The mature CD56dim NK cells are characterized by acquisition of KIRs, CD16 and CD57 in mature stages, which have functional significance in targeting and medicating their cytolytic activity. Based on these considerations, we performed haplo-HSCT with donor NK cell add-back to provide mature, functional immunological surveillance against tumor (MRD) and virus reactivation, which can frequently occur in manipulated haplo-HSCT for pediatric acute lymphoblastic leukemia (ALL). Methods: We evaluated the alloreactive effect of donor-derived NK cells in three pediatric high-risk ALL who underwent B-/T-cell alpha/beta depleted haplo-HSCT followed by donor NK infusion. Patients' characteristics are summarized in the Table. All 3 patients were male; median age was 13 months. Patients 1 and 2 had infant ALL, and patient 3 had refractory-relapsed (r/r) ALL. All patients received a median of 3 lines chemotherapy. Patient 1 received a prior allo-HSCT. Patients 1 and 2 received chemo-based conditioning regimens consisting of thyotepa, and fludarabine; In addition, patient1received treosulfan, and patient 2 received busulfan. Treosulfan was given to patient 1, due to less toxicity profile given prior allo-HSCT. Patient 3 received Total Body Irradiation (TBI), thyotepa, and fludarabine. All patients received rituximab and letermovirfor EBV and CMV prophylaxis, respectively, for all patients. Mother was Donor for all patients. Median CD34+, CD19+, CD3+-alpha/beta cell dose was 8.8, 0.05, 0.41 x 106/kg, respectively. NK cell allo-reactivity was tested by evaluating KIR genotyping and KIR/KIR-ligand mismatch in graft-versus-host direction. All three patients present KIR/KIR-ligand mismatch. Results: Engraftment was day +13, +14 and +19 for ANC, and +14, +18 and +17 for PLT (for both >20K and >50K), for patients 1, 2 and 3, respectively. NK cell number were monitored on day +7, +14, +21 and +28 (data pending). Patients received NK cell infusion on day 30 +/- 2 days. No infusion reactions were observed. MedianNK infused were 256x106/kg. None of the patients developed CMV, EBV or ADV reactivation. Patient 2 developed Grade 2 acute GvHD (skin) treated with steroids. No Grade GvHD 3-4 was observed. Median follow up was 58 days. All patients had full donor chimerism at day 30 ±2. All patients are currently in hematological CR; patient 1 converted to positive MRD at nine months from transplant. Conclusion: Alloreactive NK cell add-back infusion after B-/T-cell alpha/beta depleted haplo-HSCT could represent an effective option to improve transplant outcome and prevent virus reactivation. These NK cells may improve efficacy by enhancing GvL and could contribute to maintain the "disease control" through immunologic surveillance in high-risk ALL. Indeed, NK killing, which is higher in mature NK cells, depends on acquisition of sequential phenotypic maturation. Thus, infusion of mature donor NK cells may help to maintain control of MRD and virus reactivation through immunologic surveillance. Although our preliminary observations seem to be promising, this hypothesis should be confirmed in clinical trial of a larger number of patients. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Effective Treatment of Low Risk Acute Gvhd with Itacitinib Monotherapy

Introduction The primary treatment of acute graft-versus-host disease (GVHD), prolonged courses of high dose systemic corticosteroids (SCS), cause significant morbidities, including an increased risk of serious infections. We used validated clinical (Minnesota standard [Minn std] risk) and biomarker (Ann Arbor [AA] 1) criteria to identify a group of patients with GVHD that is low risk (LR) for treatment failure and non-relapse mortality (NRM) and who might benefit from less toxic alternatives to SCS. Itacitinib (ita), a novel JAK1 inhibitor, blocks the inflammatory cytokine pathways key to target organ damage without the myelosuppression of JAK1/2 inhibitors such as ruxolitinib. We tested the hypothesis that ita monotherapy would be a safe and effective primary treatment of low risk GVHD in a multicenter phase II trial and compared outcomes to a matched control cohort of MAGIC pts with LR GVHD treated with SCS. Methods From February 2019 to April 2021, 70 pts with LR GVHD (Minn std risk/AA1) GVHD were treated with ita 200mg/day for 28 days; responders were allowed a second 28 day cycle. Ita was discontinued without tapering. Biomarker scores were available within 30 hours from sample collections, and treatment could be delayed up to 4 days after screening to accommodate a mostly outpatient population. A contemporaneous cohort of 140 control pts, matched for key characteristics, including target organ severity, donor type, HLA-match, and GVHD prophylaxis, was created from the Mount Sinai Acute GVHD International Consortium (MAGIC) database and biorepository. Control pts were treated with standard doses of SCS (median starting dose 1.1 mg/kg). ORR at 28 days of treatment was defined as the proportion of pts achieving complete or partial response of GVHD symptoms without additional systemic therapy. Infections required laboratory/imaging proof and were considered serious if they required systemic treatment. Results Both ita and SCS treatment produced excellent ORR (ita: 89%; SCS: 86%; p=0.67) including in pts with lower GI GVHD (86% vs 86%, p=1). Similarly high ORR was observed for both cohorts for all subgroup comparisons including by GVHD grade, target organ involvement, age, donor type, HLA-match, conditioning regimen, GVHD prophylaxis, and number of days post-BMT to treatment initiation. ORR was unaffected by the time from screening to initiation of ita (≤48 hours: 90%; >48 hours: 87%; p=1). Significantly more patients treated with itacitinib achieved a response by day 7 compared to those treated with SCS (81% vs 66%, p=0.02) and among responders, ORR were equally durable up to day 90 in both groups (89% vs 88%; p=1). There were no significant differences between ita and SCS pts for 1-year relapse (18% vs 21%, p=0.64), chronic GVHD (28% vs 32%, p=0.33), NRM (4% vs 11%, p=0.21), or survival (88% vs 80%, p=0.11). Regarding the safety data of ita monotherapy, the incidence of grade ≥3 non-hematologic and non-infectious TEAEs was similar to the SCS cohort with no event occurring in >10% of pts. The incidence of new or worsening grade ≥3 neutropenia, anemia, or thrombocytopenia was similar between ita and SCS cohorts. In fact, grade ≥3 leukopenia occurred less frequently in the ita group (16% vs 31%, p=0.02). Ita treatment resulted in an 91% lower cumulative steroid dose through day 28 compared to SCS (1.9 vs 22.0 mg/kg, p<0.001) and fewer pts developed at least one serious infection within 90 days (27% vs 42%, p=0.02; Fig 1). The mean number of infections per pt was also lower (0.43 vs 0.66; rate ratio 0.65 [0.43-0.97]), as was the likelihood of developing a severe (BMT CTN grade 2 or 3) infection (odds ratio 0.50 [95% CI: 0.27, 0.93]). The reduction in serious infections was driven by fewer viral infections in the ita group (Fig 2), particularly in the first 28 days and not explained by differences in letermovir use. Conclusion A short course of itacitinib monotherapy produced very high response rates that occurred faster than treatment with SCS, were equally durable and with a similar risk for cGVHD in patients treated for LR GVHD. Importantly, ita treatment resulted in significantly less severe leukopenia and a significantly lower incidence of serious infections than SCS, likely a result of dramatically less exposure to systemic steroids. Ita monotherapy should be further studied as primary treatment for LR GVHD. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Graft Versus Leukaemia (GvL): Identification & Characterisation of Alloreactive Antigens and Cognate T Cell Responses in Acute Myeloid Leukemia

Allogeneic stem cell transplantation (allo-SCT) is the most established, curative T cell cancer immunotherapy. The curative effect of allo-SCT relies on a graft-versus-leukemia (GvL) effect; but this can be difficult to dissociate from graft-versus-host disease (GvHD). For decades, the key unsolved challenge has been to identify common alloreactive peptide-human leukocyte antigen (HLA) complexes targeted by T cells that mediate GvL but not GvHD. We developed a workflow for unbiased identification of alloreactive antigens and analysis of cognate donor alloreactive T cells and their T cell receptors (TCRs; Fig 1). We studied sequential bone marrow and peripheral blood samples, collected over 15 years, from 12 high-risk AML patients who remain in continuous complete remission following allo-SCT (all >2 years). All patients had relapsed at least once pre-allo-SCT and/or were AML flow cytometry minimal residual disease (MRD)+ pre-allo-SCT. 7 had received donor lymphocyte infusions. No patients developed >1 grade GvHD. We performed whole exome sequencing of DNA from isolated patient T cells (patient germline), AML blasts and donor DNA to identify: (i) AML-specific coding variants; and (ii) germline coding single nucleotide polymorphisms (SNPs), mismatched between patient and donor. 98.7% of the mismatched variants were germline. More variants were identified in unrelated compared with sibling donors (mean: 5744 vs 3253 variants). To narrow the list of variants taken forward for functional studies, we applied two sequential filtering steps: (i) we restricted analysis to variants expressed in the patients' AML cells (determined by RNA-Seq). 28.7% of all mismatched coding variants were expressed in AML cells; and (ii) we used in silico prediction of HLA-binding affinities of peptides spanning variant amino acids to patient-specific HLA-I and -II using NetMHCpan 4.0 and NetMHCIIpan 3.0. To functionally identify alloreactive antigens, we then screened ~200-900 peptides per patient-donor pair (total 5300 peptides) for recognition by T cells present in patient peripheral blood collected 2-7 years after allo-SCT. This enriches for the identification of long-lived anti-AML responses at a time when patients were both infection- and GvHD- free. Response screening, using IFNγ ELISPOT assays, identified T cell responses to 24 germline, mismatched epitopes. In all cases, responses were only observed when the amino acid encoded by the patient SNP, but not the donor allele, was present in the peptide. The phenotype of the epitope-specific T cells was established by intracellular cytokine staining (ICS) and flow cytometry analysis, and the HLA restriction of each T cell response was determined using HLA-I, -DR, -DP and -DQ blocking antibodies. Of the 24 alloreactive peptides,19 elicited CD4+ HLA class II restricted responses and 3 were targeted by CD8+ class I restricted T cells. Two remain to be characterised (Fig 2). The population allele frequency of the germline variant SNPs targeted varies from 0.5% to 72% in the Caucasian population. Likewise, some of the restricting HLA alleles are very common (e.g. a HLA-DP allele presenting 3 epitope peptides is present in ~66% of the Caucasian population). ICS showed that epitope-specific CD4+ T cells produce Th1 cytokines (IFNg, TNFa) and degranulate (express CD107a) in response to peptide stimulation (Fig 2). Next, we performed single cell 5'RNA-seq with TCR-seq of epitope-restricted T cells (isolated via IFN-g catch assay) for all CD4+ epitope-specific T cells. Alloreactive CD4+ T cells have cytokine-producing and cytotoxic effector potential, expressing MIP1a and b, IFNg, granzyme B and FasL (Fig 2). Finally, lentiviral-based gene transfer of one of the candidate alloreactive epitope-specific TCRs into third party primary T cells confers the capacity to generate IFNg and TNFa in response to peptide stimulation, and to recognise primary AML cell-derived antigen in the presence of monocyte-derived dendritic cells (Fig 2). In vitro and in vivo killing assays are in progress. The high proportion of CD4+ T Cell responses identified by our pipeline is concordant with downregulation of HLA II expression on AML blasts at relapse post-allo-SCT, which is a common mechanism of immune evasion, found in one-third of patients. Our approach dissects the biology of alloreactive anti-AML GvL and GvHD responses and to manipulate them for therapeutic purposes. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Mucosal-Associated Invariant T (MAIT) Cells Are Functionally Impaired in Pediatric Patients Following HCT and Their Recovery Is Associated with the Onset of GvHD

Delayed quantitative and qualitative immune recovery, in particular of the T-cell lineage, is associated with an increased risk of infections, disease relapse and adverse clinical outcomes in patients receiving allogeneic hematopoietic cell transplantation (allo-HCT). This delay is particularly relevant for recipients of T cell-depleted grafts who do not benefit from the adoptive transfer of mature donor T cells and experienced profound and prolonged immunodeficiency which lasts until the T-cell pool is newly generated from donor hematopoietic precursor cells. A better understanding of the reconstitution dynamics of all the components of the immune system after allo-HCT is crucial to optimize the control of infections, leukemia relapse and graft-versus-host disease (GvHD). We performed a longitudinal observational study to explore the kinetics of T-cell recovery in patient peripheral blood by combining multiparameter flow-cytometry and functional ex vivo assays. Ninety-three children with hematological malignancies who received transplantation after myeloablative conditioning regimen were included in the study: 59 patients received T-cell receptor (TCR) alpha-beta/CD19-depleted HLA-haploidentical HCT (alpha/beta-haploHCT), while 34 unmanipulated matched unrelated donor (MUD) HCT (32 MUD recipients received BM and 2 received PBSC). Among the different T-cell populations assessed, we found that mucosal-associated invariant T (MAIT) cells displayed profound alterations in frequency and function across all time points analyzed. MAIT cells are a class of unconventional αβ T cells that recognize microbial proteins presented by non-polymorphic MHC class I related-molecule (MR1) and possess innate-like capacity. While total TCRαβ T cells gradually started to recover approximately from 3 months reaching normal levels between one to two years post transplantation (Figure 1), MAIT cells defined as CD3+ TCRαβ+ MR1-5-OP-RU-tetramer+ showed long-term impaired reconstitution, and their numbers did not reach normal levels up to two-years post-HCT (Figure 1). Compared to MUD HCT, MAIT cell recovery after alpha/beta-haploHCT was significantly delayed, in agreement with the fact that TCRab reconstitution in this clinical setting is primarily driven by de novo T cell formation. Previous studies demonstrated that MAIT cells are characterized by the binding to MR1-Ag tetramers and simultaneous expression of the C-type lectin-like receptor CD161, a marker associated with memory phenotype and trafficking of immune cells. Interestingly, across all time points of the study, we observed that most MAIT cells following were CD161-. We also found increased expression of the activation marker CD38 and the senescence marker CD57, and downregulation of CD28 in MAIT cells following allo-HCT, suggesting a dysfunctional or hyperactivated status. In agreement with these data, ex vivo stimulation of PBMCs at day +360 post allo-HCT with Escherichia Coli or anti-CD3/anti-CD28 showed that MAIT cells had suboptimal upregulation of the activation markers CD25 and CD69, and reduced production of pro-inflammatory cytokines IFNg, TNFa and IL2, when compared to healthy control samples. Previous studies suggested that a low MAIT cell number was associated with an increased risk of acute GvHD, In the MUD cohort of our study, we did not observe significant correlations between the kinetics of MAIT cell recovery and the occurrence of GvHD. On the other hand, we found a significantly higher frequency of CD161+ MAIT cells at day +30 in alpha/beta-haploHCT patients who developed acute GvHD (grade 1 or greater). Trends toward higher frequency of CD161+ MAIT cells in patients developing acute GvHD were also observed at day +60 and +90, although not statistically significant. Our study shows that MAIT cell recovery is delayed in children for up to two years following allo-HCT. MAIT cells exhibited altered functional status as demonstrated by the expression of activation/senescence makers as well as the suboptimal response to TCR stimulation. Interestingly, we found that a large proportion of MAIT cells are CD161- after transplantation, which can be the result of recruitment of CD161+ cells to peripheral tissues or down regulation of CD161 after cell activation. Finally, our data suggested that the evaluation of CD161 expression on MAIT cells after alpha/beta-haploHCT may identify patients at risk of acute GvHD. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Efficacy and Safety of Allogenic Hematopoietic Stem Cell Transplant in Paroxysmal Nocturnal Hemoglobinuria: A Single Centre Study from Pakistan

Background: Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired disorder of clonal hematopoiesis1 .The resulting abnormalities in complement regulatory proteins can manifest as hemolysis, thrombosis, and marrow failure2. The management and clinical outcomes of patients with PNH significantly changed with the development of complement inhibitor therapies3. Allogenic Hematopoietic stem cell transplant (HSCT) despite being the sole curative option for PNH is not recommended as first line therapy owing to its toxicities 4,5. Current indications for HSCT include a suboptimal response to eculizumab, severe AA/PNH, clonal evolution to myelodysplastic syndrome (MDS), or acute myelogenous leukemia2. However, in low and middle income countries (LMIC) where complement inhibitor therapies are not available, allogenic HSCT still remains the only treatment option for classical PNH as well as for PNH in the setting of another specified bone marrow disorder. Objective: To analyze the efficacy and safety of Allogenic HSCT in patients with paroxysmal nocturnal hemoglobinuria (PNH). Study design: Observational, retrospective study. Place and duration of study: Armed Forces Bone Marrow Transplant Centre/ National Institute of Blood and Marrow Transplant (AFBMTC/NIBMT) Rawalpindi, Pakistan, from June 2008 till February 2022. Methodology: From June 2008 till February 2022, a total of 65 patients of PNH were registered at AFBMTC/NIBMT. Out of these16 patients underwent allogenic HSCT and were included in the final retrospective analysis. PNH diagnosis was confirmed by flow cytometry by the demonstration of GPI-negative cells in at least two cell lineages i.e neutrophils, red blood cells (RBCs) in 62.5% (n=10) patients and by fluorescent aerolysin (FLAER)-based assay in 37.5% (n=6) patients. Median time from diagnosis to transplant was 380 days. All patients received HLA identical sibling donor HSCT. Stem cell source was Bone marrow harvest (BMH), BMH plus peripheral blood stem cell (PBSC) and PBSC alone in 81% (n=13), 12.5% (n=2) and 6% (n=1) patients respectively. Graft versus host disease (GVHD) prophylaxis was with Antithymocyte globulin (ATG) + Cyclosporin (CSA) in patients receiving NMA conditioning or ATG + CSA + short term Methotrexate (MTX) in those receiving MAC. Results: Median age of the study cohort was 24 years (range, 18 to 42 years) and all were male. 68.7% (n=11) patients received immunosuppressive therapy before HSCT with partial or no response. History of thrombosis prior to HSCT was present in only one patient (cPNH). Allogenic HSCT done for classical PNH (cPNH) in 75% (n=12) patients and for PNH in the setting of another specified bone marrow disorder (PNH/AA) in 25% (n=4) patients. Patients with classical PNH received Myeloablative conditioning (MAC) i.e Flu150Bu12.8IV (75%, n=9), Bu16Cy120 (8.3%, n=1), or Flu150Cy200 (8.3 %, n=1) except for one patient who received Flu150Cy160. Patients with PNH/AA, received non myeloablative conditioning (NMA) i.e Flu150Cy120, except for one who received Flu150Bu12.8IV. Out of 16 patients, 94% (n=15) patients achieved successful engraftment with full donor chimerism. One patient (cPNH) had Primary graft failure. Median time to neutrophil and platelet engraftment was day +12 and day +22 respectively. Disease relapse was monitored by donor chimerism till Day +180 post BMT and thereafter by peripheral blood counts. PNH clone post BMT was not tested. Incidence of acute GVHD grade I/II involving skin and gut, was 25% (n=4). No incidence of chronic GVHD was noted. One patient (PNH/AA) had secondary graft failure on Day +46. With a median post-transplant follow-up of 15 months (range, 4 to 157) overall survival (OS) was 93.7% and disease-free survival (DFS) was 87.5%. Conclusion: In resource constrained, LMIC, where complement inhibitor therapies are currently unavailable, allogenic HSCT remains the valid option for treatment of PNH, with good overall survival rate and acceptable treatment related toxicites. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Post-Transplant Cyclophosphamide, Abatacept and Short Course of Tacrolimus (CAST) for Graft-Versus-Host Disease Prevention Following Haploidentical Peripheral Blood Stem Cell Transplantation

Background: Haploidentical blood and marrow transplantation (BMT) substantially expands the pool of potential hematopoietic stem cell donors, including for minority groups. However, the outcomes of haploidentical transplantation remain inferior to matched unrelated donor (MUD) transplants when a standard post-transplant cyclophosphamide (PTCy)-based graft versus host disease (GvHD) prophylaxis regimen is employed in both settings. To address this issue, we sought to develop a more effective GvHD prevention regimen in haploidentical transplantation. While abatacept (Aba) seems to decrease the incidence of acute GvHD, PTCy is particularly effective in the prevention of chronic GvHD. Therefore, we designed a regimen that combines the merits of both agents and examined whether such approach can allow early withdrawal of tacrolimus (Tac). Methods: We enrolled 46 adult patients with hematological malignancies receiving haploidentical transplantation from a relative in a prospective single center pilot phase Ib-II clinical trial. Patients received non-myeloablative, reduced-intensity or myeloablative preparative regimens followed by G-CSF mobilized peripheral blood transplants and a combination of PTCy (50mg/kg on days +3 and +4), Aba (10mg/kg on days +5, +14 and +28) and Tac at a dose adjusted based on blood level. Tac taper was initiated on day +60 and completed by day +90. After treating 30 patients, the study was amended to administer an additional dose of Aba on day +56 based on the noted timing of acute GvHD development and Aba terminal ½ life. Patients received standard supportive care by institutional practice including G-CSF and anti-microbial prophylaxis. Serologically CMV positive patients also received letermovir prophylaxis. Results: Patient characteristics are summarized in table 1. Importantly, 19 out of 46 (41.3%) patients were from racial or ethnic minorities. The data cutoff date was July 29th, 2022. Three patients were excluded from this analysis due to short follow-up. For the remaining patients, median follow-up was 8.9 months. Median time to neutrophil engraftment was 18 days (13-30). One patient died before achieving platelet (plt) engraftment and 2 patients have not yet achieved plt engraftment. For the remaining 40 patients, median time to plt engraftment was 29 days (16-52). All patients achieved full donor chimerism at the time of count recovery. Tac was successfully tapered off as planned in all but 5 patients. Cumulative incidence of acute GvHD grades II-IV, III-IV and IV with death as competing event was 12.8%, 5.1% and 0%, respectively. One-year (y) cumulative incidence of moderate to severe chronic GvHD was 17.1%. All cases of acute GvHD except 1 grade II acute GvHD were observed in the first 30 patients. Cases of chronic GvHD included 2 cases of overlap syndrome. There was no case of steroid-refractory acute GvHD or GvHD-related death. One-y cumulative incidence of relapse (non-relapse mortality as competing event) was 8.3% (95% CI 0%-17.1%). KM estimates of 1-year relapse-free survival (RFS), overall survival (OS) and GRFS (composite end point of grade III-IV acute GvHD-, chronic GvHD requiring systemic therapy- and relapse-free survival) were 91.7% (95% CI 83%-100%), 90.6% (95% CI 80.9%-100%) and 71.8% (95% CI 57.2%-90%), respectively. None of the safety stopping rules was triggered. There was 1 case of thrombotic microangiopathy due to Tac and 2 cases of sinusoidal occlusive disease, 1 requiring treatment with defibrotide; all 3 patients recovered. There were 2 cases of respiratory failure of undetermined etiology. One-y cumulative incidence of non-relapse mortality (relapse as competing event) was 2.6% (95% CI 0%-7.8%). The incidence of CMV and EBV reactivation was 39.5% and 2.3%, respectively. There was no case of adenovirus or HHV-6 virus reactivation. BK viruria occurred in 27.9% of patients with limited symptomatology (1 patient required treatment with cidofovir). Immune reconstitution results are summarized in figure 1. Conclusion: CAST is a new GvHD prevention regimen that seems safe and effective, yielding excellent outcomes. CAST also allows early discontinuation of Tac. Outcomes with longer follow-up will be presented at the meeting. If the results are confirmed, CAST might be a step forward toward closing an important health disparity gap in BMT, equalizing the outcomes of haploidentical transplantation and MUD transplants. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Haploidentical Donor Vs. Mismatch Unrelated Donor in Reduced Intensity Conditioning Transplant: A Study from the Spanish Group of Hematopoietic Transplant and Cell Therapy (GETH-TC)

The most suitable donor for allogeneic stem cell transplant is still a matter for debate when there is no matched related or unrelated donor. In this setting, information comparing MMURD vs. HAPLO remains scarce and do not show differences between both sources (Piemontese, S et al., Hematol Oncol. 2017; Shem-Tov N et al., Leukemia 2020; Battipaglia G et al., BMT 2022). This study analyzes the outcomes of HAPLO vs. MMURD stem cell transplant recipients in reduced intensity conditioning scenarios (allo-RIC) in a retrospective analysis from the GETH-TC study group. Methods: Consecutive patients receiving a first allo-RIC between 1/2012 and 3/2021 at 9 GETH/EBMT centers with HAPLO or MMURD (mismatch at HLA-A, B, C, or DRB1 by molecular techniques) were included. Patients undergoing HAPLO received post-transplant cyclophosphamide (PTCY) based graft vs. host disease (GVHD) prophylaxis associated with rapamycin, tacrolimus, or cyclosporine, +/- mycophenolate. For MMURD, prophylaxis was diverse, including PTCY. Baseline characteristics and outcomes were compared according to the donor type through logistic regression. To balance the two groups, the Propensity Score Weighting method was performed with the variables that were significant in the logistic regression. Survival was calculated using the Kaplan-Meier method and the HR using the Cox model. The primary objective was the comparison of the aGVHD III-IV or severe chronic GVHD-free/relapse-free survival (GRFS). Secondary endpoints were overall survival (OS), relapse/progression-free survival (DFS), non-relapse-related mortality (NRM), relapse, and acute and chronic GVHD. Results: A total of 411 patients were included, 287 HAPLO and 124 MMURD (Table 1), with a median follow-up of 46.1 and 48.2 months, respectively. The GRFS at 24 months was similar in both groups, 48.5% vs. 53.9% in HAPLO and MMURD, respectively [HR 0.9, P=0.79). There were no differences in 2 year-OS 58.9% vs. 60.7% (HR 1.04, P=0.93), or in 2-year DFS 55.1% vs. 55.8% (HR 1.05, P=0.9). Similarly, NRM (32.3% vs. 32.1% (HR 1.09, P=0.85) and relapse (18.6% vs. 17.9% (HR 0.96 [95%CI 0.31;2.96] P=0.94) did not present statistically significant differences between HAPLO and MMURD. In addition, there was no difference between groups in time to neutrophil (19 days [95%CI 18;20] HAPLO vs 18 days [95%CI 15;19] MMURD, P= 0.08) and platelet engraftment (27 days [95%CI 23;29] HAPLO vs 20 days [95%CI 13; 33] MMURD, P= 0.15). Regarding 2-4 acute GVHD, the incidence at 6 months was 51.7% vs. 63.2% in the HAPLO vs. MMURD recipients (HR 1.44 [95%CI 0.8; 2.6], P=0.23), without significant differences in 3-4 acute GVHD grade. Seventy-seven HAPLO patients and 42 MMURD patients developed global chronic GVHD, with no significant differences in incidence between groups. Remarkably, MMURD (1% [95%CI 0; 2.6]) had lower incidence of severe forms of chronic GVHD than HAPLO (6.7% [95%CI 2.5; 10.6]) (HR 0.11 95%CI [0.02;0.57], P=0.01). When the analysis was restricted to PTCY-based prophylaxis patients (48 MMURD vs. 287 HAPLO), the outcomes were similar, with a significantly lower incidence of severe forms of chronic GVHD in the MMURD group. Finally, events defining GRSF were similarly distributed between both groups (Figure 1), except for chronic GVHD. However, the latter had a low incidence in both groups, so this difference did not impact the primary endpoint. Conclusion: In this cohort of patients, no differences in terms of OS, DFS, NRM, relapse, or GRSF were observed between HAPLO and MMURD. Transplantation with MMURD was associated with less severe chronic GVHD, even when considering the group of patients with PTCY prophylaxis exclusively. This advantage of MMURD compared to HAPLO is not translated into an improvement on the GRFS. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Haploidentical Hematopoietic Cell Transplantation of Ex Vivo Tcrαβ-Depleted Grafts with CD45RA-Depleted Memory T Cell Add-Back Reduces Chronic Graft-Versus-Host Disease and Results in Favourable Gvhd-Relapse Free Survival: 5-Year Follow-up of 107 Patients Treated in a Multicenter Study in Singapore

Background: Haploidentical hematopoietic cell transplantation (HCT) provides an alternative option for patients without HLA-matched donors. Graft-versus-host disease (GVHD), engraftment failure, and infectious complications are main causes of non-relapse mortality (NRM). We hypothesized that selective depletion of TCRαβ+ and CD45RA+ naïve T cells will permit hematopoietic engraftment while effectively reducing GVHD and providing donor immune reconstitution through adoptive transfer of donor's mature NK cells, γδ T cells and CD45RO+ memory T cells. Methods: Mobilized PBSC products were divided into two fractions in 8-9 : 1-2 ratio and depleted using CliniMACS device after labelling with TCRαβ and CD45RA reagents (Miltenyi Biotec, Bergish-Gladbach, Germany) respectively. All except 13 patients received the standard conditioning regimen of fludarabine 160mg/m2 divided daily over 4 days, thiotepa 10mg/kg divided twice daily for 1 day, and melphalan 70 - 140 mg/m2 for 1 day, in combination with either total lymphoid irradiation 6 Gy (n=58) or 7.5 Gy (n=12) over 3 equal fractions, total body irradiation of 2 Gy (n=24), or thymoglobuline (n=2). Short term GVHD prophylaxis was given for 30 days to 1 patient using MMF, 95 using tacrolimus, and 2 using sirolimus. Results: Between January 2017 and July 2022, we transplanted 107 patients, including 100 adults (median age, 52 years; range 19- 70) and 7 children (median age, 13 years, range 7 - 17), with high risk AML (n=60), ALL (n=22), MDS (n=10), plasma cell neoplasm (n=3), mast cell leukemia (n=1), acute undifferentiated leukemia (n=1), CMMoL (n=2), CML (n=2), MPN (n=1) and lymphoma (n=5). Patients were infused with TCRαβ and CD45RA depleted grafts containing a median of 6.18 x 106 (range 2.13 - 20.78) CD34+ cells/kg, 0.00 x 104 (range 0 - 0.97) CD45RA+CD3+ cells/kg, and 1.21 x 106 (range 0.15 - 11.67) CD45RO+CD3+ cells/kg. TCRαβ depleted graft fraction contained a median of 0.37 x 104 (range 0 - 11.30) TCRαβ+ cells/kg, and 7.72 x 106 (range 0.62 - 42.00) TCRγδ+ cells/kg. Only 1 patient experienced primary graft failure with no secondary graft failures. All others had engraftment of ANC > 500 cells/µL at median of 12 days (range 8 - 25) and PLT > 20,000 cells/µL at median of 11 days (range 7 - 17). 10 patients with high donor-specific HLA antibodies (DSA) titres engrafted successfully after desensitisation with plasma exchange, rituximab, immunoglobulin, and irradiated donor buffy coat infusion (n=1). 38 patients (35%) developed acute GVHD of grade II - IV, with a cumulative incidence (CI) of grade II-IV and grade III-IV of 34%, and 12% respectively, at 180 days. Chronic GVHD was seen in only 4 patients at a 2-year CI of 5 % . 1-year CI of non-relapse mortality (NRM) and relapse were 18.4 % and 17.2%, respectively. 4 of the 22 NRM were attributed to aGVHD. Viral reactivation included CMV (n=39), HHV-6 (n=28), EBV (n=19), and adenovirus (n=8). 11 patients (11%) out of the 15 infection-related death (15%) occurred within 180 days. At a median follow up of 23 months (range 0.3- 67.1) in surviving patients, 2-year overall (OS), event-free (EFS), and GVHD-free/relapse-free (GRFS) survival were 69.9 %, 58.7 %, and 57.3 %, respectively (Figure 1). In multivariate analysis, HCT-comorbidity index (HCT-CI) has shown significant impact on OS (p=0.008), EFS (p=0.03), and NRM (p=0.002). Disease risk index (DRI) also showed significant impact on OS (p=0.042), EFS (p=0.02) and relapse (p=0.04). In contrast, NRM was only influenced by HCT-CI (p=0.002). In the subset analysis of 63 patients (adults, n= 58; children, n=5) with favorable HCT-CI score of 0/1 and low/intermediate risk DRI, the 2-year OS, EFS, and GRFS were 75.0 %, 68.6%, and 68.0 %, respectively (Figure 2). Conclusions: Our preliminary results suggest that RIC haplo-HCT with TCRαβ and CD45RA+ depleted grafts allow successful allograft in patients with high-risk haematological malignancies lacking suitable matched donors, including patients with high levels of DSA. Acute GVHD was generally abortive, leading to low incidence of chronic GVHD and favorable GRFS. Best outcomes are seen in patients with favourable HCT-CI and low/intermediate risk DRI. Further efforts are needed to reduce the risk of infection-related death in patients with high risk HCT-CI, and relapse risk in patients with high risk DRI, through optimization of conditioning regimen intensity, anti-microbial prophylaxis or prophylactic infusion of memory-cell DLI. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Interventional Antibiotic Treatment Replacing Antibiotic Prophylaxis during Allogeneic Hematopoietic Stem Cell Transplantation Is Safe and Feasible: A Single-Center Analysis

Background: Patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) are at increased risk of infection-related mortality during the pre-engraftment period. Systemic antibiotic prophylaxis (SAP) is widely used during the period of neutropenia but is associated with disruption of the intestinal microbiome, an increased risk of Clostridium difficile infection (CDI) and colonization with multi-drug resistant (MDR) bacteria. Aims: We retrospectively assessed the safety and efficacy of a change in our center policy from SAP to an exclusively interventional antibiotic treatment (IAT) in adult patients undergoing allogeneic HSCT. Outcome measures were overall survival (OS) and non-relapse mortality (NRM) at 3 years, antibiotic administration, incidence of blood-stream infections (BSI) and incidence and severity of acute and chronic graft-versus-host disease (GVHD). Methods: Cefotaxime was used as standard of care prophylaxis during neutropenia after HSCT prior to January 2018. After a 12 months transition time during which both strategies were employed in parallel, SAP was replaced by an IAT strategy with meropenem being administered immediately by nursing staff in case of neutropenic fever or any other signs of infection, and subsequently deescalated to piperacillin/tazobactam (pip/taz) when appropriate. We compared 67 consecutive patients undergoing HSCT in 2017, all of whom received antibiotic prophylaxis (SAP cohort) with all patients in 2019 comprising the IAT cohort (n=68). Use of antibiotics is reported as number of daily doses per 100 care days (DDD/100CD) until discharge after HSCT. Results: Patient characteristics are summarized in table 1. Median age was 56 years, 82% of patients were grafted with peripheral blood stem cells (PBSC) for acute leukemia (74%) from a matched unrelated or related donor (MUD, 61%; MRD 17%). Patient characteristics were well balanced between the SAP and IAT cohorts, except those patients transplanted in 2019 were more likely to have an HCT-CI ≥ 3 (56% vs 36%, p=0.025) and receive reduced-intensity conditioning (62% vs 40%, p=0.025). In the SAP and IAT cohort, neutropenic fever was observed in 46% and 62% of patients (p=0.085). However, the cumulative incidence (CI) of BSI by day +100 post-HSCT was significantly higher in the IAT vs SAP cohort (40% vs 13%, p<0.001), which did not result in more patients admitted to the intensive care unit (13% vs 6%, p=ns) and did not translate into a higher CI of NRM at 3 years (10% vs 9%, p=ns). With a median follow-up of 1052 days, 3-year OS was 70% and 69% for the SAP and IAT cohort, resp. (p=ns, figure 1). CI of acute GVHD grade II-IV or chronic GVHD of any grade at 3 years was 34% (p=ns) and 45% (p=ns), resp., resulting in identical survival free of acute GVHD grade III-IV, chronic GVHD requiring systemic immunosuppressive therapy and relapse-free survival (GRFS) of 36% (p=ns) in both groups. We observed a tendency to a higher CI of severe chronic GVHD in the SAP cohort (27% vs 13%, p=0.08). There was no significant difference between the two cohorts in terms of newly detected colonization with MDR bacteria during conditioning and after HSCT (VRE 17%; ESBL 5%; 3/4 MRGN 5%; MRSA 0%) and the incidence of CDI was likewise equal in both cohorts (13%, p=ns). Compared to SAP, IAT resulted in significantly fewer days of antibiotic therapy (24 vs 18, p<0.001) and accordingly less administration of cefotaxime (12.8 vs 3.8 DDD/100CD), teicoplanin (26.2 vs 6.3 DDD/100CD), vancomycin (11.5 vs 8.3 DDD/100CD) and meropenem (23.1 vs 16.7 DDD/100CD). Solely use of pip/taz increased (14.3 vs 23.6 DDD/100CD), while the amount of imipenem remained unchanged (7.6 versus 7.8 DDD/100CD). Thus, we observed a significant 40% reduction of the median antibiotic consumption (p=0.0312) in 2019. In the multivariate analysis, only age > 60 years and a high or very high disease risk index were identified as negative prognostic factor for OS. Conclusion/Summary: Our single center experience in conducting HSCT without antibiotic prophylaxis but with strict guidelines for prompt antibiotic intervention demonstrated no disadvantage in OS and NRM, despite a higher CI of BSI. IAT resulted in considerably less consumption of cefotaxime, but also carbapenem and glycopeptide antibiotics. We conclude that the proposed procedure of IAT replacing SAP is safe and feasible. Larger patient numbers are needed to confirm a possible benefit of IAT on GVHD. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Bodyweight and Absolute Lymphocyte Count Based Dosing of Rabbit Anti-Thymocyte Globulin Results in Early CD4+ Immune Reconstitution in Patients with Inborn Errors of Metabolism Undergoing Umbilical Cord Blood Transplantation

Background Rabbit anti-thymocyte globulin (rATG) is used in allogeneic hematopoietic cell transplantation (HCT) to prevent graft failure through depletion of host T cells and decrease the risk of graft-versus-host disease (GVHD) through partial depletion of donor T cells. However, it has highly variable pharmacokinetics. Previous reports suggest rATG dosing should be based on recipient bodyweight and absolute lymphocyte count (ALC) prior to initiating rATG. This new dosing nomogram reduces rATG overexposure, potentially leading to faster immune reconstitution and subsequently superior overall outcomes. Methods Since January 12, 2017, we use a previously described rATG dosing nomogram based on bodyweight and ALC before administering rATG in patients with inborn errors of metabolism receiving an umbilical cord blood transplant at the University of Minnesota Masonic Children's Hospital. The proposed rATG dosing varied from 2 to 10 mg/kg based on bodyweight and recipient ALC prior to initiating rATG, starting 8 or 9 days before HCT. The myeloablative conditioning regimen was Busulfan based, with addition of Fludarabine and Cyclophosphamide for lymphodepletion, as well as Rituximab and/ or Bortezomib for prevention of immune-mediated cytopenia. For GVHD prophylaxis cyclosporin A or tacrolimus were used with methylprednisolone. The primary endpoint was CD4+ immune reconstitution (>50 CD4+ T-cells/mL) within 100 days after transplantation. Secondary endpoints included overall survival, graft failure, acute and chronic GVHD, myeloid and T cell donor chimerism at one year post transplant, time to neutrophil engraftment and viral reactivations of cytomegalovirus, adenovirus and Epstein Barr virus. The study protocol was approved by the Institutional Review Board of University of Minnesota. Results Between February 20, 2017, and June 28, 2021, 27 patients were included in the study. Median follow-up time was 31 months (IQR 22.0 to 38.5) and median age was 1.45 years (IQR 0.7 to 3.9). Ten (37%) of 27 patients were female. The baseline characteristics are presented in Table 1. rATG dose was adjusted below 10 mg/kg recipient body weight in 7 (26%) of 27 patients on average by 29% (SD 14.9%). The CD4+ recovery at 100 days post HCT was reached in 22 (85%) of 26 patients (Figure 1A). Overall, four (15%) patients died resulting in overall survival of 83% (95%CI 67% to 100%). Causes of death were intracranial bleeding due to immune-mediated thrombocytopenia (this patient was transplanted before introduction of bortezomib and rituximab for immune-mediated cytopenia prevention), diffuse alveolar hemorrhage, respiratory syncytial virus infection and disease progression. Median time to neutrophil engraftment was 14 days (IQR 12.5 to 18.0), and no graft failure was observed. All surviving patients had full myeloid chimerism and 14 of 23 (61%) of patients had full T cell donor chimerism at one year post HCT. Two (7%) patients developed acute GVHD grade II to IV (Figure 1B), and no patients had chronic GVHD. Six patients (22%) had cytomegalovirus viremia, five of them were seropositive before transplant, one patient was seronegative as was the mother of the donor. One patient, who was seronegative before transplant, had Epstein-Barr virus reactivation requiring treatment, no patient had adenovirus reactivation. Conclusion In pediatric patients with inborn errors of metabolism individualized dosing of rATG was associated with a robust and early CD4+ immune reconstitution, with low therapy related mortality, low GVHD incidence compared to historical findings and stable full myeloid chimerism. These results are in line to the findings of the PARACHUTE trial previously published. However, the PARACHUTE trial included only small number of patients with inborn errors of metabolism. Table 1. Baseline characteristicsFigure 1A. Cumulative incidence of CD4+ immune reconstitutionFigure 1B. Cumulative incidence of acute Graft-versus-host disease Grade 2 to 4Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Improved T-Cell Chimerism and Successful Withdrawal of Immunosuppression after Non-Myeloablative Stem Cell Transplantation for Sickle Cell Disease with Azathioprine/Hydroxyurea Preconditioning Added to Alemtuzumab/TBI Conditioning

Background: Allogeneic hematopoietic stem cell transplantation (HSCT) is currently the only established curative treatment option for sickle cell disease (SCD). In adult SCD patients, myeloablative conditioning is associated with significant toxicity, primarily because of cumulative organ damage. Recently, matched sibling donor (MSD) transplantation with non-myeloablative conditioning (alemtuzumab/3 Gy total body irradiation (TBI)) showed promising outcomes in adult SCD patients. This chemotherapy-free regimen, typically resulting in mixed chimerism, is associated with mild toxicity with no reports of graft-versus-host disease (GvHD). Despite mixed chimerism, the red blood cell (RBC) phenotype is completely donor-derived. However, in a large series, 13% of patients experienced graft failure. Another 8.2% of patients could not stop their immunosuppression (sirolimus) after one year, because of low donor T-cell chimerism (<50%). Reported mean donor T-cell chimerism at 12-months post-transplantation was 48% (Br J Haematol. 2021 Feb;192(4): 761-768). We hypothesized, that the addition of azathioprine and hydroxyurea as preconditioning to the alemtuzumab/TBI conditioning regimen will reduce the risk of graft failure and improve donor T-cell chimerism, enabling successful withdrawal of sirolimus in all patients. Aim: To investigate the effects of adding azathioprine/hydroxyurea preconditioning to alemtuzumab/TBI conditioning on donor chimerism levels and the occurrence of graft failure in adult SCD patients receiving non-myeloablative MSD-HSCT. Methods: Adult SCD patients with an available HLA-identical sibling donor were eligible for this treatment. All patients received three months of azathioprine 150mg qd and hydroxyurea 25mg/kg qd preconditioning. After exchange transfusion (target HbS <30%), conditioning with alemtuzumab 1mg/kg total dose and 3Gy TBI started on day -7, followed by unmanipulated peripheral hematopoietic stem cell infusion on day 0. Sirolimus as GvHD and rejection prophylaxis started on day -1. Results: Twenty SCD patients (median age 26 (range 19-49) years) were transplanted with a median follow-up of 24.5 months (range 1-52 months). Patient and transplant characteristics are shown in Table 1. Median donor myeloid and T-cell chimerism of engrafted patients was 100% (range 87-100%) and 68.5% (range 37-89%) at 12-months post-transplantation and 94% (range 86-100%) and 78.5% (range 68-88%) at 18-months post-transplantation, respectively (Figure 1). These donor T-cell chimerism percentages are higher than previously reported with alemtuzumab/TBI conditioning only. All engrafted patients had a corrected SCD phenotype with normalized hemoglobin levels. Importantly, all patients with a follow-up of ≥ 12 months (n=12) could successfully taper and stop sirolimus without decreases in donor chimerism. One year estimated disease-free survival and overall survival were 94.7%. and 93.3%, respectively. One patient (5%) experienced graft failure without autologous regeneration and subsequently died after a series of complications, including EBV reactivation, post-transplantation lymphoproliferative disease, and systemic aspergillosis. Acute gastrointestinal GvHD grade 2 occurred in one patient (5%) and resolved quickly after treatment with prednisolone. Summary/Conclusion: Azathioprine/hydroxyurea preconditioning prior to alemtuzumab/TBI resulted in improved donor T-cell chimerism, potentially reducing the risk of graft failure after non-myeloablatieve MSD transplantation in SCD patients. Importantly, all engrafted patients reached donor T-cell chimerism >50% and were able to stop immunosuppressives as scheduled. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Phase IIa Study of Adding Itacitinib to Tacrolimus/Sirolimus Gvhd Prophylaxis after Fludarabine/Melphalan-Based Conditioning Hematopoietic Cell Transplantation for Acute Leukemias, Myelodysplastic Syndrome, or Myelofibrosis

Graft-versus-host disease (GVHD) is the primary cause of non-relapse mortality (NRM) after allogeneic hematopoietic cell transplant (HCT). Itacitinib is a novel, potent, and selective Janus kinases-1 (JAK1) inhibitor that has shown activity in treatment of acute and chronic GVHD. We hypothesized that adding Itacitinib to the standard tacrolimus/sirolimus GVHD prophylaxis is safe and can potentially improve GVHD-free, relapse-free survival (GRFS). Here, we are reporting outcomes of our single arm, single center phase 2a study (NCT04339101) investigating the safety and efficacy of itacitinib administration in patients with acute leukemias, myelodysplastic syndrome (MDS), or myelofibrosis (MF) who underwent PBSC-HCT from a matched donor. Patients received fludarabine (125 mg/m2) and melphalan (140 mg/m2 or 100 mg/m2 for patients ≥70 years) as reduced intensity conditioning. GVHD prophylaxis was sirolimus/tacrolimus (target levels: 5-10ng/ml for both), with itacitinib at 200 mg/day starting from day -3 pre-HCT and continued until day +100. (Figure 1a) Our primary objective was to investigate the safety of itacitinib (Safety lead-in segment; n=6) and estimate 1-year GRFS. Ultimately a total of 59 patients were treated with itacitinib at 200 mg/day dose. Primary endpoint for the safety lead-in segment was toxicity; scored on both the Bearman and NCI CTCAEv5.0 scales. Primary endpoint for the expansion segment was 1-year GRFS. Key secondary endpoints included grade 2-4 acute GVHD, engraftment, infection, overall survival (OS), progression-free survival (PFS), NRM, relapse, chronic GVHD, and itacitinib pharmacokinetics (PK). The enrollment goal was 59 including 6 in the safety lead-in to estimate GRFS at 45% with precision of 0.13. We completed the enrollment (n=59; 36 males [61%] and 23 [39%] females) in May 2022. Median age at the time of HCT was 63 years (range: 23-75), with 14 patients being ≥70 years old at the time of HCT. Patients received HCT from a matched related (n=22) or unrelated (n=36) donor for acute leukemias (n=38; 64.4%), MDS (n=17; 28.8%), or MF (n=4; 6.8%). HCT-CI was 0 in 37 (62.7%) and 1 in 14 (23.7%) of patients. At the time of this report, 57 patients have completed the 100-day observation. The current report is focused on the early data and endpoints with a median follow up duration of 5.9 months (range: 0.6-12.4). There was no case of protocol-defined unacceptable toxicity in the safety lead-in phase. All 59 patients engrafted with a median time to neutrophil and platelet engraftment of 15 days (range: 11-23) and 16 days (range: 8-80), respectively. There were no deaths in the first 100 days except for one patient who passed due to severe sepsis and resultant multiple organ failure. Grade 3-4 adverse events (by CTCAEv5.0) within 100 days, reported as at least possibly related to itacitinib, were anemia (n=1), febrile neutropenia (n=2), abdominal pain (n=1), lymphocytopenia (n=8), neutropenia (n=1), thrombocytopenia (n=3), leukopenia (n=3), and hypertriglyceremia (n=1). There were 19 microbiologically documented infections during the first 100 days (12 bacterial, 5 viral, and 2 fungal infections). Acute GVHD grade 2-4 and 3-4 were observed in 6 (10%) and 5 (8%) patients, respectively. With the limited follow up duration (5.9 months) and observed events including all-cause mortality (n=9, NRM=6), grade 3-4 acute GVHD (n=5), moderate/severe chronic GVHD (n=2), and disease relapse (n=8), the estimated GRFS at 6-months and 1-year were 0.71 (95%CI: 0.56-0.81) and 0.51 (95%CI: 0.31-0.68), respectively. (Figure 1b) Results of our preliminary PK studies (n=18) showed average itacitinib trough levels between days -2 and +5 of 25.2.6 ± 39.1 nM. Average Cmax, AUC 0-inf, T1/2, and CL/F around the dose on Day +5 were 11362.0 ± 852.9 nM, 4905.6 ± 2422.8 nM x hr, 4.4 ± 1.7 hr, and 90.3 ± 39.6 L/hr (Figure 1c). The measured itacitinib exposure is significantly higher than previously reported results, indicating a potential drug interaction with sirolimus. In conclusion, early results of this phase 2 study indicated that itacitinib (200 mg daily) with tacrolimus/sirolimus GVHD prophylaxis was safe and tolerated with 100% engraftment and low rate of acute GVHD without excessive toxicities. Early survival data including preliminary GRFS are promising. The study follow up is ongoing, and mature clinical data and immune reconstitution analyses will be updated. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Endothelial Complications of Hematopoietic Cell Transplantation for Sickle Cell Disease

Introduction Hematopoietic cell transplantation (HCT) is a curative therapy for sickle cell disease (SCD), with especially favorable outcomes in young patients from HLA-identical donors. Unfortunately, HCT is associated with endothelial injury syndromes (EIS), including veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS), transplant-associated thrombotic microangiopathy (TA-TMA), and also acute graft-versus-host disease (GVHD), that increase transplant risk. This is further complicated by hemolysis-mediated endothelial dysfunction in patients with SCD. The impact of EIS in this population is not certain. We thus sought to better evaluate endothelial complications of HCT for SCD in a large, international registry. Methods We examined de-identified records of HCT for SCD that were retrieved from data on patients transplanted between 1991 and 2020 in the United States submitted to the Center for International Blood and Marrow Transplant Research (CIBMTR) obtained through curesickle.org. Patients were followed longitudinally until death, loss to follow-up, or last contact through June 2021 at 3, 6, 12, and 24 months after HCT, and then every 2 years. Donors included HLA-matched siblings, haploidentical relatives, and HLA-matched and HLA-mismatched unrelated donors. We examined overall survival, event-free survival, and acute and chronic GVHD. Cox regression models were used to examine for risk factors associated with TMA and VOD. In addition, one-factor (univariate) analysis was used to identify factors associated with higher risk complications. Results A total of 1641 unique patients underwent a first allogeneic HCT between 1991 and 2020, with a median year of HCT of 2014. Of HCT recipients, 67.7% were below the age of 18 years at HCT and 74.7% had Karnofsky performance score ≥ 90. Acute GVHD grades II-IV developed in 18.3% and 22.3% developed chronic GVHD. Graft failure was reported in 17.6% following HCT, which was from an HLA-identical sibling in 61.5%, mismatched relative in 17.6%, matched unrelated donor in 10.2%, and mismatched unrelated donor in 10.7%. Conditioning regimen was myeloablative (50.8%), reduced intensity (23%), or non-myeloablative (22.3%). Patients were followed for a median of 47.8 months (0.3 - 312.9), with 3-year overall survival 91.2% and 3-year event-free survival 85.2%. Median time to death was 9.6 months for 152 patients. Estimated hazard ratio (HR) of death in 7/8 vs. 8/8 HLA matching was 1.5 (95% CI: 0.752, 2.445), which was not statistically significant. However, HR of death for ≤ 6/8 vs. 8/8 HLA matching was 1.7 (95% CI: 1.215, 2.445), indicating a statistically significant increased risk of death. TA-TMA was reported in 27 patients at a median of 2.8 months post-HCT. Univariate analysis of risk factors for TA-TMA indicated increasing incidence with the year of HCT. Age at HCT, HLA matching, and conditioning regimen intensity were not significantly associated. VOD was reported in 24 cases; Cox proportional hazards analysis indicated decreasing incidence with year of HCT. Estimated HR for VOD of patients who developed grade II-IV AGVHD group was 2.965, (95% C.I. 1.089, 8.074). Age at HCT, conditioning intensity, and donor type were not significant. Acute and chronic GVHD were associated with recipient age > 10 years and donors other than HLA-matched siblings; non-myeloablative conditioning was protective against GHVD development. Conclusion Incidence of endothelial complications following HCT for SCD is low, although TA-TMA has been increasingly recognized in recent years. VOD has been observed less frequently over time and correlates with acute GVHD. Donor type, recipient age, and conditioning intensity have the greatest impact on GVHD development.

Allogeneic Hematopoietic Cell Transplantation (Allo-HCT) in Patients with Calr-Mutated Myelofibrosis

Background: Between 50-65% of myelofibrosis (MF) patients who undergo allogeneic hematopoietic cell transplantation (allo-HCT) are cured. Patient age, performance status, comorbidities, donor type, and HLA compatibility are established risk factors for allo-HCT outcomes. However, prognostic information after transplant in MF is largely based on JAK2-mutated patients, as this molecular abnormality is by far the most common and the first to be described. Since there is evidence suggesting that CALR-mutated patients could have a better outcome (Kroger et al., BBMT 2017), a study evaluating prognostic factors in this specific molecular subtype may be of clinical interest. Method: This is a retrospective, registry-based study approved by the Chronic Malignancies Working Party (CMWP) of the European Society for Blood and Marrow Transplantation (EBMT). For the present study, inclusion criteria were adult patients with CALR-mutated MF undergoing first allo-HCT between 2005 and 2019. Patients transplanted from umbilical cord blood or with history of leukemic transformation were excluded. Primary study outcomes were OS, progression-free survival (PFS), relapse, non-relapse mortality (NRM) and graft-versus-host disease (GVHD)-free and relapse-free survival (GRFS). Results: 346 patients transplanted in 123 centers were included, of whom 207 (59.8%) were male. A total of 244 (70.5%) patients had primary MF (PMF) and 102 patients had MF secondary to prior essential thrombocythemia (SMF). Median interval from diagnosis to allo-HCT was 50.9 months (IQR: 17.2-155.6). Median age was 57.4 years (IQR: 51.2-63). DIPSS score at time of allo-HCT was available in 256 (74%) patients and was high, intermediate-2, intermediate-1 and low in 17%, 46%, 35%, and 2%, respectively. Sixty-nine patients (21%) had a high comorbidity index (HCT-CI) > 3. Seventeen patients (7.5%) had been splenectomized before transplant. Reduced intensity (RIC) regimens were utilized in 63% of patients and the donor source was peripheral blood in 95% of cases. Regarding donor type, an HLA-matched sibling donor (MSD), mismatched related donor (MMRD), matched unrelated donor (MUD) and mismatched unrelated donor (MMUD) was used in 92 (27%), 18 (5%), 167 (48%) and 48 (14%) of patients, respectively. T cell depletion was used in 77% of patients. Median time to neutrophil engraftment was 17 days. Incidence of acute GVHD grades II-IV at 100 days and extensive chronic GVHD at 60 months were 27% and 28%, respectively. After a median follow-up of 40 months from transplant, the estimated 5-year OS rate, PFS, GRFS, NRM and relapse incidence was 63%, 57%, 35%, 25% and 18%, respectively. Causes of death were relapse/progression (n=11), GVHD (n=36), infection (n=27), organ failure/toxicity (n=11), secondary malignancy (n=6), other (n=9), and unknown (n=3). The estimated 3-year OS rate was 79%, 37%, 72% and 62% for allo-HCT from MSD, MMRD, MUD and MMUD, respectively (p=0.09; Figure 1). The estimated 5-year OS rate in patients transplanted from an HLA identical donor was 64%. In univariable analysis, a high comorbidity index (47% vs. 66%; p=0.013) and a PMF diagnosis (55% vs. 79%; p=0.008) correlated with inferior 5-year OS rate. These two factors were associated with higher NRM rate at 5 years after transplant (HCT-CI > 3: 28% vs. 19%, p=0.033; PMF: 31% vs. 12%, p=0.012), with no difference in relapse incidence. Table 1 shows the results of the multivariable analyses for the main outcomes. As can be seen, older age (HR: 1.37, 95% CI: 1.08-1.74; p=0.009) was the only factor significantly associated with a worse OS, whereas PMF (HR: 1.58, 95% CI: 0.96-2.62; p=0.07) and transplant from a mismatched donor (HR: 1.55, 95% CI: 0.95-2.52; p=0.08) had a near-to-significant trend for decreased OS. Conclusion: this is the largest series of allo-HCT for CALR-mutated MF patients. Overall, the results seem favorable, especially in patients with SMF or transplanted from an HLA-identical donor, where the 5-year OS in this multicenter series was 79% and 64%, respectively. NRM was the main cause of treatment failure. Figure 1. Overall survival after transplant in 346 CALR-positive myelofibrosis patients depending on the donor type. Table 1. Results of the multivariable analyses for the main study outcomes. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Improved Post-Transplant Outcomes in Recent Years for AML Patients with Intermediate Karyotype, FLT3-ITD and Wild Type NPM1: A Report from the EBMT Acute Leukemia Working Party

Rationale: Allogeneic hematopoietic cell transplantation (allo-HCT) is recommended in first complete remission (CR1) in acute myeloid leukemia (AML) patients harboring FLT3 internal tandem duplication (FLT3-ITD). However, historically, long-term survival has been poor due to early relapse, particularly for patients with wild-type NPM1. Recently, FLT3 inhibitors in combination with chemotherapy before allo-HCT, or as post-transplant maintenance, have significantly reduced the risk of relapse and improved survival. Here, we assessed real-world changes over time in transplant characteristics and post-transplant outcomes in young AML patients with FLT3 ITD and either NPM-1 mutated or wild type, using a large dataset from the European Society of Blood and Marrow Transplantation (EBMT) registry. Patients and Methods: We identified 1827 adult AML patients (54% female; median age 49 years, range 18-60) with FLT3 ITD, intermediate karyotype and available NPM1 mutation status, allografted between 2012 and 2021 in CR1 from a matched related (32%), matched unrelated (56%) or haploidentical donor (12%). NPM1 was mutated in 72% of patients. At transplant, 834 patients were measurable residual disease (MRD) positive, 464 MRD negative, and 529 were not evaluated or missing. Comorbidity index (CI) was zero in 59% of patients with available data. Conditioning was myeloablative (MAC) in 64% of patients. In vivo T cell depletion (TCD) graft was given to 62% of patients, post-transplant cyclophosphamide (PTCy) to 17%, and 87% received peripheral blood stem cells (PBSC). Most patients (66%) and donors (54%) were cytomegalovirus (CMV) positive. Median follow-up of alive patients was 30 months (IQR 28-32). Results: We compared changes in patient and transplant characteristics over time in 688 (38%) patients transplanted between 2012 and 2016 and 1139 (62%) patients transplanted between 2017 and 2021. Patients transplanted in recent years had a shorter follow up, were more likely to have NPM1 mutation, to be MRD positive, to have a higher CI, to receive a transplant from a haploidentical donor, a CMV positive donor, and to receive PBSC and PTCy. For patients with wild-type NPM1, day 100 acute graft-versus-host disease (GVHD) grade II-IV and grade III-IV were encountered in 29% and 11% of patients transplanted in 2021-2016, respectively, and 21% and 7% for patients transplanted in 2017-2021, respectively. The 2-year cumulative incidence of chronic and extensive chronic GVHD were 32% and 16%, respectively for 2012-2016 and 36% and 20%, respectively for 2017-2021. Over time, the 2-year cumulative incidence of relapse (CIR) significantly decreased from 43% to 31% between the two time periods (p<0.04) and non-relapse mortality (NRM) significantly decreased from 14% to 8% (p<0.05). The 2-year leukemia free survival (LFS) and overall survival (OS) significantly improved over time from 54% to 64% (p<0.02) and from 63% to 71% (p<0.05) respectively, whereas GVHD-free, relapse-free survival (GRFS) improved from 39% to 46% (p=0.08). In multivariate Cox analysis (MVA), transplantation in recent years significantly reduced the CIR (hazard ratio [HR]=0.65; p<0.01), and acute GVHD grade II-IV (HR=0.6; p<0.01) and significantly improved LFS (HR=0.67; p=0.02), OS (HR=0.66; p<0.03), and GRFS (HR=0.77; p<0.05). The use of unrelated donors increased the risk of acute GVHD but reduced the CIR whereas the use of haploidentical donors increased NRM. In vivo TCD reduced the risk of chronic GVHD whereas female donors to male recipients increased it. PTCy decreased the risk of NRM whereas MAC reduced the CIR. For patients with NPM1 mutation, no significant changes over time in post-transplant outcomes were noted except for decreased NRM from 15% for 217 patients transplanted in 2012-2016, to 10% for 288 patients transplanted in 2017-2021 (p<0.02). In MVA, transplantation in recent years did not significantly affect any of the post-transplant outcomes. Conclusion: In AML patients with FLT3 ITD and wild-type NPM1, we noticed a significant decrease over time in the CIR and a significant improvement of LFS, OS and GRFS, likely reflecting the efficacy of FLT-3 inhibitors, including when used as post-transplant maintenance, in this high-risk setting. On the contrary, no significant change over time was noticed in post-transplant outcomes of patients harboring NPM1 mutation.

Improved Outcomes of UM171-Expanded Cord Blood Transplantation Compared with Other Graft Sources: Real World Evidence

Background: Cord blood (CB) transplantation (CBT) has several advantages compared with other graft sources. CBT has low rates of chronic graft-versus-host disease (GVHD) and allows for several human leukocyte antigen (HLA) mismatches, thus expanding donor availability. However, CBT has fallen into disfavor because of its low cell dose and associated prolonged cytopenias, which result in prolonged hospitalization and higher risk of non-relapse mortality (NRM). Furthermore, the need for large CBs leads to selection of poorly HLA matched CBs, further increasing NRM. UM171 is a small molecule that expands hematopoietic stem cells. From 2016 to 2018, 22 patients with high-risk malignancies who lacked a donor were transplanted on a phase I-II clinical trial with a single UM171-expanded CB (Cohen S et al. Lancet Haematol 2019) after a myeloablative conditioning. The goal was to accelerate engraftment while selecting smaller, better HLA matched CBs to decrease NRM while preserving the benefits of CBT. Results demonstrated that indeed UM171-expanded CB has the potential to overcome slow neutrophil engraftment and diminish NRM. The aim of the current analysis was to examine outcomes after conventional single/double ≥ 4/6 HLA-matched CB and 8/8-matched unrelated donor (MUD) peripheral blood stem cell (PBSC) transplantation with UM171-expanded CBT. Methods: Data on UM171-expanded adult CBT recipients were drawn from the phase I-II trial. Data for adult recipients of myeloablative CB and PBSC transplants for hematologic malignancies (acute myeloid and lymphoblastic leukemia, chronic myeloid leukemia, non-Hodgkin and Hodgkin lymphoma) in the United States and Canada during 2014-2019 with a Karnofsky performance status (KPS) score ≥70 were obtained from the Center for International Blood and Marrow Transplant Research (CIBMTR) database. CB recipients who received anti-thymocyte globulin or alemtuzumab in the conditioning were excluded from the CIBMTR population. Patients were directly matched for the number of prior allogeneic transplants (alloHCT), refined disease risk index (for 1st alloHCT), disease status (for 2nd alloHCT), and acute myeloid leukemia cytogenetic risk. Patients were matched by propensity score for age, comorbidity index and KPS. CIBMTR attempted to identify 4 controls per UM171 patient. Clinical outcomes included engraftment, NRM, progression-free survival (PFS), overall survival (OS), relapse, GVHD-free, relapse-free survival (GRFS), acute GVHD grade III-IV, and chronic GVHD. PFS, OS, and GRFS were estimated by Kaplan-Meir method; other outcomes were calculated using cumulative incidence estimates; marginal Cox regression models were used for analyzing NRM and GRFS. Results: Overall, 137 CIBMTR (67 CB, 70 PBSC) and 22 UM171-expanded CBT patients participated. Univariate analysis and marginal Cox regression analysis results are shown in Tables 1 and 2, respectively. Median time to neutrophil engraftment was 18 days (range 10-30) for UM171-expanded CB recipients compared to 21 days (range 8-53) for CIBMTR CB recipients (p<0.01) (data not shown). Univariate analysis revealed less 1- and 2-year NRM, improved 2-year PFS, improved 1-year OS, and 1- and 2-year GRFS for UM171-expanded CBT compared to CIBMTR CB controls. The UM171 cases had less 1- and 2-year NRM, improved 2-year PFS, and improved 1- and 2-year GRFS compared to CIBMTR PBSC controls. Furthermore, UM171-expanded CB patients experienced less acute GVHD III-IV and chronic GVHD compared to PBSC recipients. In marginal Cox regression analysis, UM171-expanded CBT recipients were 87% and 63% less likely than CIBMTR CB controls to experience NRM and GRFS events, respectively, and 73% less likely to experience GRFS events than CIBMTR PBSC recipients. Conclusions: This real-word evidence suggests that UM171-expanded CB recipients have select improved outcomes compared to conventional CB and MUD PBSC recipients. While this study was limited by the small number of UM171 CB trial participants and inability to identify the planned number of controls for each case, UM171 expansion of CB appeared to achieve the desired outcome of maintaining CB's benefits while removing its disadvantages. Thus, prospective randomized studies of UM171-expanded CBT compared to MUD PBSC alloHCT are warranted to confirm these results. Study Support: This study was funded by ExCellThera. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

A Second Haploidentical Stem Cell Transplantation (HAPLO-SCT2) after Relapse from First Haplo-SCT Is Feasible and Produces Results That Are Comparable to Data Reported after Second SCT in an HLA-Matched Setting - a Study on Behalf of the Acute Leukaemia Working Party (ALWP) of the European Society for Blood and Marrow Transplantation (EBMT)

Introduction For patients with high-risk acute leukemia (AL) lacking a matched sibling donor (MSD) or matched unrelated donor (MUD), an allogeneic stem cell transplant (alloSCT) from a haploidentical (HAPLO) donor is an increasingly used alternative. However, available data on the treatment of relapse after HAPLO-SCT is scarce. After a first transplant from MSD/MUD, a second allogeneic SCT (alloSCT2) using either MSD or MUD achieved 2-year overall survival (OS) in 20-30% of patients, independently of donor type for alloSCT2 and donor change. In contrast, there is little information supporting the feasibility and efficacy of a second HAPLO-SCT (HAPLO-SCT2) in patients with AL transplanted from a HAPLO donor at alloSCT1. On behalf of the Acute Leukaemia Working Party (ALWP) of the European Society of Blood and Marrow Transplantation (EBMT), we report here on the outcome of 82 patients with AL that underwent HAPLO-SCT2 after relapse from a first HAPLO- SCT in Europe. Methods This was a registry-based analysis of adults with acute myeloid leukemia and acute lymphoblastic leukemia (AML/ALL). All consecutive patients that had received a HAPLO-SCT2 without ex-vivo manipulation after hematologic relapse from HAPLO-SCT1 between 2007 and 2021 were included. Outcomes of interest were engraftment, OS, leukemia-free survival (LFS), non-relapse mortality (NRM), relapse incidence (RI), graft-versus-host disease (GvHD), and GvHD-free, relapse-free survival (GFRS) rates after HAPLO-SCT2. Results Eighty-two patients (AML, n=63, 77%; ALL, n=19, 23%) were identified. The median age at HAPLO-SCT2 was 47.2 years (range, 18.3-69.3) for AML and 33.5 (range, 19.7-58.2) for ALL (p=0.002), median interval from HAPLO-SCT1 to relapse was 7.5 months. A donor change between HAPLO-SCT1 and 2 was chosen in 35 (62.5%) of AML and 17 (89.5%) of ALL patients (p=0.042). Cell source was peripheral blood/bone marrow (PB/BM) in 15/67 (18%/82%), respectively. At HAPLO-SCT2, 21 (33.3%) AML patients had a complete remission (CR) and 49 (59.8%) an active disease, whereas 12 (63.2%) ALL patients were in CR (p=0.02). Reduced intensity conditioning (RIC) was used for HAPLO-SCT2 in 57% of patients, and post-transplant cyclophosphamide (PTCy) was the most frequent GvHD prophylaxis (82%). Following HAPLO-SCT2, median follow-up was 38/19 months for AML/ALL patients, respectively. In the entire cohort, 87% of patients engrafted. Cumulative incidences (CI) at day 180 of acute GvHD grade 2-4 and 3-4 were 23.9% and 15.3%, respectively. The CI of chronic GvHD and extensive chronic GvHD at 2 years was 22.6% and 11.2%, respectively. Overall, 2-year OS and LFS from HAPLO-SCT2 were 34.3% and 25.4%; 2-year NRM, RI, and GRFS rates were 17.6%, 57% 15.1%, respectively (Figure 1). When analysed separately by diagnose, 2-year OS/LFS were 28.7%/22.3% for AML and 55.3%/38.4% for ALL, respectively. NRM was relatively low (16.2%/23.5% in AML/ALL), while RI was considerable, reaching 61.6%/38.2% for AML/ALL, respectively. Consequently, leukemia was the most frequent cause of death. Among the 63 patients with AML, an analysis of risk factors for OS/LFS from HAPLO-SCT2 identified disease status at HAPLO-SCT1 (p=0.008/p=0.026), and at Haplo-SCT2 (p=0.047/p=0.043) as well as the interval from HAPLO-SCT1 to relapse (p=0.001/p=0.001) as most important variables. In contrast, conditioning intensity and change of donor did not make a significant difference. No clear risk factor was identified for NRM. Conclusion This is the largest cohort of patients undergoing double HAPLO-SCT analysed so far. Within the limits of a registry-based analysis, the data show the feasibility of a second HAPLO-SCT after relapse from HAPLO-SCT1 with high engraftment rates and acceptable NRM. Outcome data as well as risk factors are comparable to results reported after alloSCT2 in a matched donor setting. Results were encouraging among patients with ALL (n=19, only 2 with Philadelphia chromosome positive [Ph+] disease), who were younger and more often received HAPLO-SCT2 in CR and from a new donor. HAPLO-SCT2 is a viable option for AL patients relapsing after a HAPLO-SCT1. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Association between gene polymorphisms in the cyclophosphamide metabolism pathway with complications after haploidentical hematopoietic stem cell transplantation.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative treatment for patients with hematologic malignances. Haploidentical HSCT (Haplo-HSCT) is an alternative option for patients who do not have an HLA-matched donor. The use of post-transplantation high dose cyclophosphamide (PT-Cy) is commonly employed for graft-versus-host disease (GVHD) prophylaxis in haplo-HSCT. Cyclophosphamide (Cy) is an alkylating agent with antineoplastic and immunosuppressive activity, whose bioactivation requires the activity of polymorphic enzymes in the liver to produce phosphoramide mustard, which is a DNA alkylating agent. To identify polymorphisms in the genes of Cy metabolism and correlate them with post-HSCT complications [GVHD, sinusoidal obstruction syndrome (SOS), hemorrhagic cystitis (HC) and transplant-related mortality (TRM)], we designed a custom next-generation sequencing panel with Cy metabolism enzymes. We analyzed 182 patients treated with haplo-HSCT with PT-Cy from 2007 to 2019, detecting 40 variants in 11 Cy metabolism genes. Polymorphisms in CYP2B6, a major enzyme involved in Cy activation, were associated with decreased activity of this enzyme and a higher risk of Graf-versus-host disease (GVHD). Variants in other activation enzymes (CYP2A6, CYP2C8, CYP2C9, CYP2C19) lead to decreased enzyme activity and were associated with GVHD. Polymorphisms in detoxification genes such as glutathione S-transferases decreased the ability to detoxify cyclophosphamide metabolites due to lower enzyme activity, which leads to increased amounts of toxic metabolites and the development of III-IV acute GVHD. GSMT1*0 a single nucleotide polymorphism previously recognized as a risk factor for SOS was associated with a higher risk of SOS. We conclude that polymorphisms of genes involved in the metabolism of cyclophosphamide in our series are associated with severe grades of GVHD and toxicities (SOS and TRM) after haplo-HSCT and could be used to improve the clinical management of transplanted patients.

Posttransplant cyclophosphamide-based anti-graft-vs-host disease prophylaxis in patients with acute lymphoblastic leukemia treated in complete remission with allogeneic hematopoietic cell transplantation from human leukocyte antigen-mismatched unrelated donors versus haploidentical donors: A study on behalf of the ALWP of the EBMT.

Both mismatched unrelated donor (MMUD) and haploidentical (haplo) transplantation are valid options in patients with high-risk acute lymphoblastic leukemia (ALL) lacking a matched donor. The study compared the outcomes of adult patients with ALL in complete remission (CR) who underwent 9/10 MMUD versus haplo transplantation with posttransplant cyclophosphamide (PTCy) as graft-vs-host disease (GVHD) prophylaxis in 2010-2020. The study included 781 patients (MMUD, 103; haplo, 678). The median age was 40 (19-73) and 38 (18-75) years, respectively (p= .51). The most frequent immunosuppression agents added to PTCy were mycophenolate mofetil (MMF)/cyclosporine A and MMF/tacrolimus. In vivo T-cell depletion (anti-thymocyte globulin) was administered to 21% and 8% of the transplants, respectively (p< .0001). Neutrophil (absolute neutrophil count >0.5 × 109 /L) recovery was achieved in 97.1% versus 96.7% versus (p= 1) in MMUD and haplo, respectively. Nonrelapse mortality and relapse incidence were not significantly different between MMUD and haplo, hazard ratio (HR)=1.45 (95% confidence interval [CI], 0.81-2.62; p= .21) and HR=0.81 (95% CI, 0.52-1.28, p= .38), respectively. HRs for leukemia-free survival, overall survival, and GVHD-free, relapse-free survival were respectively, HR=1.05 (95% CI, 0.73-1.50, p= .8), HR=1.17 (95% CI, 0.77-1.76, p= .46), and HR=1.07 (95% CI, 0.78-1.46, p= .7) for haplo compared to MMUD. Acute (a)GVHD grade 2-4 was significantly higher with haplo, HR=1.73 (95% CI, 1.08-2.76, p= .023), whereas aGVHD grade 3-4 and chronic GVHD did not differ significantly between the two transplant groups. Outcomes of MMUD and haplo transplants with PTCy-based GVHD prophylaxis for ALL patients in CR are similar, apart from a higher incidence of aGVHD with haplo transplants.