Nonmyeloablative Conditioning Regimen Research Articles

211At-Labeled Anti-CD45 Antibody as a Nonmyeloablative Conditioning for Canine DLA-Haploidentical Stem Cell Transplantation.

The α-emitter 211At deposits a high amount of energy within a few cell diameters, resulting in irreparable DNA double-strand breaks while minimizing off-target toxicity. We investigated the use of the 211At-labeled anti-CD45 monoclonal antibody (mAb) 211At-CD45-B10 as a nonmyeloablative conditioning regimen for dog-leukocyte-antigen-haploidentical hematopoietic cell transplantation. Methods: Seventeen healthy dogs were injected with either a 0.50 (n = 14) or 0.75 (n = 3) mg/kg dose of anti-CD45 mAb labeled with 211At (8.436-23.199 MBq [0.228-0.627 mCi/kg]) on day -3. Peripheral blood stem cells from dog-leukocyte-antigen-haploidentical donors were given on day 0. Peripheral blood chimerism was calculated by polymerase chain reaction assays, and blood clearance of the radioimmunoconjugate was studied using enzyme-linked immunosorbent assay and radioactivity measurements of serial blood samples. Results: All dogs achieved donor chimerism by day 28 (range, 27%-100%). The hematopoietic engraftment rate was 100%, though engraftment durability was variable. No difference in absorbed dose to blood was seen for the 2 mAb dosing levels studied. Neutropenia (0-29 cells/μL), lymphocytopenia (36-130 cells/μL), and thrombocytopenia (1.5-9 × 103/μL) with prompt recovery were observed. The main adverse nonhematologic event related to 211At-CD45-B10 was mild reversible transaminitis. Graft-versus-host disease was not seen. Twelve of the 17 dogs survived over 30 d, with donor chimerism ranging from 3% to 99%. Conclusion: The results suggest that nonmyeloablative conditioning with 211At-CD45-B10 could be used in haploidentical hematopoietic cell transplantation though with variable engraftment.

Prognostic impact of the conditioning intensity on outcomes after allogeneic transplantation for MDS with low blasts: a nationwide retrospective study by the adult MDS working group of the Japan Society for Transplantation and Cellular Therapy.

Poor prognostic factors, such as transfusion dependency and chromosomal risk, need to be considered in the indication of allogeneic hematopoietic cell transplantation (allo-HCT) for patients harboring myelodysplastic syndromes with less than 5% marrow blasts (MDS-Lo). We analyzed the post-transplant outcomes of 1229 MDS-Lo patients who received myeloablative (MAC)(n = 651), reduced-intensity (RIC)(n = 397), and non-myeloablative conditioning (NMAC) regimens (n = 181). The multivariate analysis revealed that the RIC group had better chronic graft-versus-host disease (GVHD)- and relapse-free survival (CRFS) (P = 0.021), and GVHD- and relapse-free survival (GRFS) than the MAC group (P = 0.001), while no significant differences were observed between the NMAC and MAC groups. In the subgroup analysis, the MAC group has better overall survival (P = 0.008) than the RIC group among patients with an HCT-comorbidity index (HCT-CI) score of 0, while the RIC group had better overall survival (P = 0.029) than the MAC group among those with an HCT-CI score ≥3. According to the type of conditioning regimen, total body irradiation 12 Gy-based MAC regimen showed better OS and CRFS than the other MAC regimen, and comparable outcomes to the RIC regimen. In conclusion, the RIC and NMAC regimens are promising options for MDS-Lo patients in addition to the MAC regimen.

Chapter 12 - Hematopoietic stem cell transplantation for neuromyelitis optica spectrum disorder. Can immune tolerance be reestablished?

Neuromyelitis optica (NMO), which is also referred to as Devic's disease, was originally considered an aggressive subtype of multiple sclerosis (MS) presenting as optic neuritis and/or extensive transverse myelitis in which 50% of patients become blind or in a wheelchair within 5 years of onset. Subsequently, NMO was categorized as one of a spectrum of inflammatory and demyelinating autoimmune disorders that are distinct from multiple sclerosis and termed neuromyelitis optica spectrum disorder (NMOSD). NMOSD differs from multiple sclerosis by its clinical course, presentation, magnetic resonance imaging findings, clinical presentation, serum biomarker prognosis, and response to treatment. More recently, NMOSD has been subdivided according to auto-antibody status as aquaporin 4 (AQP4) seropositive NMO, myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD), and seronegative NMOSD. The only treatment to date that has resulted in treatment-free remissions, now lasting for more than 5-10 years with posttreatment disappearance of anti-AQP4 antibodies, is hematopoietic stem cell transplantation (HSCT) using either an allogeneic (matched sibling or unrelated) donor with a reduced toxicity conditioning regimen or an autologous stem cell source using a nonmyeloablative conditioning regimen of plasmapheresis (PLEX), cyclophosphamide (Cytoxan®), rabbit antithymocyte (ATG), and rituximab (Rituxan®). Post-HSCT long-term resolution of disease activity and disappearance of AQP4 antibodies is consistent with HSCT-induced immune tolerance.

The range of haploidentical transplant protocols in sickle cell disease: all haplos are not created equally.

The ideal curative therapy for sickle cell disease (SCD) must be applicable across all ages and include individuals with strokes and preexisting heart, lung, and kidney disease. Myeloablative, matched sibling donor hematopoietic stem cell transplant (HCT) for children with SCD has shown excellent outcomes over the past 3 decades but has been restricted due to the limited availability of a human leukocyte antigen-matched sibling donor (10%-15%) and increased treatment-related death in adults with myeloablative conditioning. To overcome these 2 significant barriers to curative therapy in SCD, related haploidentical HCT has become an active area of research. The use of related haploidentical donors (first- and second-degree relatives) increases the donor pool to at least 90% of those eligible across the life span. Importantly, most adults, even with strokes or significant comorbidities, can tolerate the nonmyeloablative conditioning regimen without treatment-related death. Since 2013, at least 3 related haploidentical HCT strategies have emerged as potential curative therapies for SCD: (1) a nonmyeloablative, T-cell replete, bone marrow transplant with thiotepa and posttransplant cyclophosphamide with a goal of complete donor chimerism; (2) a nonmyeloablative, in vivo T-cell depletion, using peripheral blood stem cells (PBSCs) with a goal of stable mixed donor-recipient chimerism; and (3) a myeloablative, ex vivo T-cell depletion using PBSCs and advanced-technology graft manipulation, with a goal of complete donor chimerism. We review the similarities, differences, outcomes, and gaps in knowledge with these 3 haploidentical HCT approaches for SCD.

Outcomes of Allogenic Hematopoietic Stem Cell Transplantation in Patients Aged 70 Years and Older

Background: Allogeneic hematopoietic cell transplantation (Allo-HCT) is a highly effective method of achieving prolonged disease control for many types of blood cancers. However, historically, older adults were not considered eligible candidates for Allo-HCT due to concerns about increased toxicity and mortality. This is a significant issue, as the proportion of cancer patients with comorbidities, disability, and geriatric syndromes increases by 3-5% for every 5-year increase in age beyond 65 years. This systematic review aims to address this gap in literature by analyzing survival prognosis in patients aged 70 years and above who have undergone Allo-HCT. Methods: As per the preferred reporting items for systemic reviews and meta-analysis (PRISMA) guidelines, a comprehensive literature search was performed on 3 databases (PubMed, Cochrane Register of Controlled Trials and Clinicaltrials.gov) using MeSH terms and keywords for “Hematopoietic Stem Cell Transplantation” AND “Outcome Assessment” AND “>70 years old” from the date of inception to Feb 13, 2023. Our research produced 101 articles. After excluding irrelevant and review articles during primary and secondary screening, six original studies reporting outcomes of Allo-HCT in patients over 70 years were included. The methodological quality of the included studies was evaluated using NIH quality assessment tool. Inter-study variance was calculated using the Der Simonian-Laird Estimator. Proportions along with 95% confidence Interval (CI) were extracted to compute pooled analysis using the ‘meta’ package by Schwarzer et al. in the R programming language (version 4.16-2). Results: A total of 2292 patients aged 70 years or more were included for this systematic review and meta-analysis. (Table 1) The median age was 71.75 (70-84) years and 67.5% (n=1547) patients were male. Median follow-up time was 22.1 (5-37.1) months. The underlying diagnosis was acute myeloid leukemia (AML) 63% (n=1445), myelodysplastic syndrome (MDS) 20.9% (n=480), non-Hodgkin lymphoma (NHL) 5% (n=115), acute lymphocytic leukemia (ALL) 4.2% (n=96), and chronic lymphocytic leukemia (CLL) 3.1 % (n=71). The source of stem cells was peripheral blood, bone marrow, and cord blood in 90.2% (n=2068), 6.2% (n=142), and 3.1% (n=70) of the patients, respectively. Myeloablative conditioning (MAC) was used in 17.8% of patients, reduced-intensity conditioning (RIC) was used in 77.4% of patients, and a non-myeloablative conditioning regimen (NMA) was used in 4.6% of patients. The Hematopoietic Cell Transplantation-specific Comorbidity Index (HCT-CI) of the included patients was 0 (25.7%), 1-2 (30.1%), and 3 or more (44.2%). The pooled overall survival (OS) at a median of 2 years (1-3) was 41.8% (95% CI 0.34-0.49, I2=88%, p<0.01, n=2292). The pooled progression-free survival (PFS) was 36.4% (95% CI 0.31-0.43, I2=75%, p<0.01, n=1979) at a median of 2 (1-2) years while the pooled incidence of relapse and non-relapse mortality (NRM) was 33.7% (95% CI 0.29-0.38, I2=69%, p<0.01, n=2292) and 28.7% (95% CI 0.22-0.36, I2=88%, p<0.01, n=2292), respectively. The pooled incidence of acute graft versus host disease (GvHD) grade II-IV at a median of 6 months (3-24) and grade III-IV at median of 4.5 months (3-24) was 25.8% (95% CI 0.20-0.31, I2=84%, p<0.01, n=2270) and 11.1% (95% CI 0.10-0.13, I2=2%, p=0.39, n=1979), respectively, while the pooled incidence of chronic GvHD at a median of 1.5 years (1-2) was 33.6% (95% CI 0.28-0.40, I2=84%, p<0.01, n=2292). Conclusion: Our meta-analysis shows that allo-HCT offers promising outcomes for elderly patients aged 70 or greater, and should be considered more frequently for those with transplant eligible disease. It also shows that age can be a restrictive factor due to co-existing comorbidities and poor performance status. Several other factors such as the availability of matched donors, conditioning regimen can play a role in the final outcome of disease progression and associated adverse effects such as GVHD.

Favorable Fertility Outcome in a Large Cohort of Sickle Cell Disease Patients Undergoing Allogeneic Hematopoietic Stem Cell Transplantation

Introduction: Fertility preservation is an important consideration for individuals with sickle cell disease (SCD) who may face reproductive challenges. While SCD itself does not directly affect fertility, certain complications and its treatment such as hematopoietic cell transplantation (HCT) can impact the reproductive health in SCD patients. HCT is a potential curative therapy for SCD, however, one of the negative outcomes is the premature gonadal failure and infertility. Both male and female patients have different risk factors that may impact the fertility post-transplant. Therefore, these patients should undergo fertility preservation counselling pre transplant. In this study, we report the fertility outcome of large transplant cohort undergoing Non-myeloablative (NMA) conditioning regimen. Methods: We retrospectively collected the data for all SCD patients who were ≥ 14 years old and who underwent allogeneic HCT in our center from 2015 until 2022 with a minimum of 1 year follow up post-transplant. All patients received hydroxyurea for 2 to 3 months pre- transplant at maximum tolerated dose. The conditioning regimen was alemtuzumab 1 mg /kg divided over 5 days from day - 7 to day -3 and Total Body Irradation 200 cGy on day -2 (with testicular shielding for male patients). Graft versus host disease prophylaxis with sirolimus started from day -1 and continued for at least 1 year post-transplant. We started the fertility program in October 2019 where all patients get counselled for fertility preservation methods. Male patients undergo sperm cryopreservation after holding hydroxyurea for 3 months and female patients were referred to a specialized oncology fertility clinic for either oocyte cryopreservation or treatment with Gonadotropin-releasing hormone (GnRH) agonists pre transplant. Primary objective of the study was to assess post-transplant fertility (defined by either ability to conceive for married patients, or development of azoospermia for male patient or secondary amenorrhea for female patients). Secondary objectives were to assess pre transplant fertility, assess the success of different fertility preservations methods and finally to assess for risk factors (pre- transplant and transplant) that affect the fertility potential. Results: We identified a total of 200 SCD patients who underwent HCT. Out of these 200 patients, 107 (54%) were included in our fertility program. The median post-transplant follow up was 3.5 years (1 - 7.5). One hundred and twelve patients (56%) were male, and eighty eight (44%) were female patients. All patients were on hydroxyurea pre transplant with average dose 1000 mg and a duration of less than 2 years in 47 (23.5%) patients, 2 to 5 years in 94 (47%) patients and more than 5 years in 59 (39.5%) patients. Other baseline characteristics are shown in table 1. In the pre-transplant fertility assessment; 58 patients were married and 48 (82%) of them had children pre transplant. 36 male patients attempted sperm cryopreservation and were successful in 33 (91%). 39 female patients received Leuprolide (GNRH agonists) pre-transplant with no complications and 6 female patients attempted oocyte cryopreservation and all were successful. One patient developed cerebral venous thrombosis during the oocyte cryopreservation course. For the post-transplant fertility assessment; out of 57 married patients 26 (45%) were able to conceive. From these 26 pregnancies; 20 ended with successful live-births, 1 ended with abortion and 5 are still pregnant. 6 patients were able to conceive twice and one patient had one twin babies. For male patients 74 did semen analysis at minimum 1 year post-transplant; 35 (47%) had azoospermia and 39 (53%) had viable sperms. Majority recovered spermatogenesis after 1 year (24 patients), at 2 years (9 patients) and after 3 years (3 patients). Three male patients had Azoospermia at one year but was able to conceive successfully without repeating the test. For female patients 71 (80.7%) were able to regain menses and 17 (19.3%) developed secondary amenorrhea. Table 2 shows the pre and post-transplant fertility measures outcome. In conclusion In this study, we have shown the fertility outcomes of male and female patients with SCD undergoing NMA conditioning HCT can be preserved in a significant proportion of patients. All adult patients should be counselled for fertility preservation methods before undergoing curative allogeneic HCT.

A Novel and Cost-Efficient Measurable Residual Disease (MRD) Detection Assay Using a Single Molecule Molecular Inversion Probe-Based Next Generation Sequencing (NGS) Assay Predicts Overall Survival in Patients with Acute Myeloid Leukemia Undergoing Allogeneic Stem Cell Transplantation

Introduction Relapse remains the main reason for poor outcomes of patients (pts) with acute myeloid leukemia (AML). Allogeneic hematopoietic stem cell transplantation (HSCT) is the preferred post-remission treatment in pts at high risk of relapse. The presence of measurable residual disease (MRD) after intensive frontline treatment or before or after HSCT has emerged as an important predictor of relapse. Various methods are used for MRD detection, including flow cytometry and molecular assays detecting individual gene mutations (mut) such as NPM1mut. Next generation sequencing (NGS)-based assays covering multiple genes commonly mutated in AML may allow sensitive MRD detection in a broad range of pts with diverse genetic characteristics. Methods We established a targeted, error corrected NGS MRD assay utilizing single-molecule molecular inversion probes (smMIPs). The smMIP protocol uses a hybridization-capture approach to selectively enrich and amplify both DNA strands of 92 regions in 32 genes in a single reaction. Unique molecular identifiers (UMIs) facilitate computational correction of sequencing errors to enable reliable detection of variants ≥0.5% variant allele frequency (VAF), with the additional advantage of relatively low reagent and sequencing costs of < $100 per sample. The smMIP assay was used to evaluate MRD status on pre-HSCT bone marrow samples from 98 AML pts who received an HSCT in first (n=83) or second (n=15) complete remission with or without count recovery. Median age at HSCT was 59 (range 20-75) years, 42% were female; 70% had de novo AML, 19% had an antecedent myeloid neoplasm and 11% had AML post cytotoxic therapy. European LeukemiaNet (ELN)-2022 risk groups at diagnosis were favorable in 11%, intermediate in 33%, adverse in 20% and unknown in 22%. All pts had received intensive induction chemotherapy. Twenty-nine percent received a myeloablative conditioning regimen (MAC), while 23% received reduced intensity conditioning (RIC) and 48% a non-myeloablative (NMA) conditioning regimen. Donors were matched related (18%), haploidentical (6%), or matched (55%) or mismatched (21%) unrelated. The median follow-up for pts alive was 34.8 months. Results Overall, we detected 190 variants in 71 (72%) of 98 pre-HSCT remission samples. The most commonly affected genes were DNMT3A (in 37% of pts), TET2 (21%), PPM1D (12%), IDH2 (10%) and TP53 (5%). Twenty-nine percent of pts had only variants affecting the clonal hematopoiesis-related genes DNMT3A, TET2 or ASXL1 (‘DTA‘), while 44% of patients had ≥1 variant involving a non-DTA gene. MRD-positive pts, defined as those with ≥1 non-DTA variant, had similar baseline and HSCT-related characteristics (includingage, sex, ELN risk group, de novo vs. secondary AML) compared to pts without non-DTA variants. Overall survival (OS) was significantly inferior in NGS MRD-positive pts compared to those with no non-DTA variant (Figure A, 5-year OS, 49% vs. 85%, P=.011). MRD-positive pts also had a non-significant higher cumulative incidence of relapse at 5 years (46% vs. 24%, P=.14), while non-relapse mortality was similar in both groups (P=.72). We next performed multivariable analyses, considering variables associated with OS at an univariable P<.10 (MRD status, patient sex, therapy-related AML, conditioning intensity), and using stepwise backward variable selection to identify factors significantly associated with OS (Figure B). In the final multivariable model, pre-HSCT MRD detection remained associated with inferior OS (hazard ratio 2.51; 95% confidence interval, 1.07 - 5.91; P=.035). Female sex associated with favorable OS, while myeloablative conditioning (MAC) showed a borderline significant association with superior OS. Of note, we did not detect an interaction between conditioning intensity and detection of MRD with regard to OS, i.e. the prognostic association of MRD detection was not different between pts receiving myeloablative or less-intensive conditioning. However, this analysis was limited by the small patient number. Conclusion Detection of MRD by targeted NGS using the smMIPs approach provides prognostic information in pts undergoing allogeneic HSCT, including those without established molecular markers such as NPM1mut. This method is applicable to a large proportion of AML pts and is cost-efficient for broad clinical use. S.M.K. and T.H., and M.J. and K.H.M. contributed equally to this abstract.

Role of Measurable Residual Disease (MRD) Testing for the Prediction of Late Relapses Following Allogeneic Hematopoietic Cell Transplantation in Adult Acute Myeloid Leukemia

BACKGROUND: Measurable residual disease (MRD) before and/or shortly after allogeneic hematopoietic cell transplantation (HCT) is an independent indicator of high post-HCT relapse risk in acute myeloid leukemia (AML). However, many relapses, particularly among patients with MRD, occur within the first 3 months after allografting, and the role of MRD testing in the identification of patients at risk of relapses occurring at later times is unknown. METHODS: To address this uncertainty, we studied all adults ≥18 years with AML or MDS/AML based on 2022 International Consensus Classification criteria who received a first allograft while in first or second morphologic remission at a single institution between 4/2006 and 3/2023 and underwent MRD testing via multiparameter flow cytometry during the pre-HCT evaluation. In line with the performance characteristics of the assay, any detectable MRD was considered positive. RESULTS: One thousand two hundred and sixty-two patients with AML (n=1,112 [88%]) or MDS/AML (n=150 [12%])underwent allograft following myeloablative (n=732 [58%]) or non-myeloablative (n=530 [42%]) conditioning regimens. Of these, 260 (21%) tested positive for MRD during the pre-HCT evaluation. With a median follow-up of 60.6 (range: 1.9-196.3) months after HCT among survivors, there were 589 deaths, 381 relapses, and 259 NRM events contributing to the probability estimates for relapse, overall survival (OS), relapse-free survival (RFS), and non-relapse mortality (NRM) in this cohort. 239/1,262 patients (19%) experienced disease recurrence (n=181 [14%]) and/or death (n=89 [7%]) within the first 100 days after allografting. Relapse ( P<0.001) and death ( P=0.002) but not NRM ( P=0.29) before day +100 were more common among patients with pre-HCT MRD. Of patients alive without relapse at day +100, 93% (954 of 1,023) underwent bone marrow restaging studies between day 70 and 100 post-HCT. Among these 954 patients, 146 (15%) had MRD before HCT, whereas only 25 (3%) had MRD at day +70-100 testing. The latter had a significantly higher 3-year relapse risk (37% vs. 18%; P=0.002), and worse RFS (17% vs. 68%; P<0.001) OS (16% vs. 72%; P<0.001) and NRM (46% vs. 14%; P<0.001) relative to the 929 patients without MRD; for results of univariate regression models, see Table 1. Importantly, however, while 130 of the 146 patients (89%) with MRD before HCT tested negative for MRD at day +70-100, their outcomes were substantially worse compared to patients who tested negative for MRD before HCT and at day +70-100, with 3-year relapse risk of 38% vs. 15% ( P<0.001), 3-year RFS of 47% vs. 71% ( P<0.001), and 3-year OS of 53% vs. 75% ( P<0.001), whereas 3-year NRM estimates were similar (14% vs. 14% ( P=0.21). Qualitatively similar results were obtained when the cohort was restricted to patients with AML, and also when comparing patients undergoing myeloablative conditioning with those undergoing non-myeloablative conditioning, with a statistically significantly higher relapse risk and lower RFS and OS but not NRM for patients with MRD before HCT but no MRD at day +70-100 compared to those who tested negative for MRD before HCT and at day +70-100 (Table 1). CONCLUSION: For AML and MDS/AML patients alive without relapse at day +100 after allografting, MRD testing at day +70-100 post-HCT identifies patients at increased risk of relapse and worse survival, but only a small number of patients will test positive at this post-HCT timepoint. While a high proportion of patients with MRD before HCT will test negative for MRD at day +70-100, their outcomes are substantially inferior to patients without MRD both before and at day +70-100 after HCT. These data suggest that all patients with pre-HCT MRD should be considered for pre-emptive therapeutic strategies, ideally in the setting of well-controlled clinical trials, given their high risk of disease recurrence regardless of the post-HCT MRD information.

Application Gene Variation Detection before and after Hematopoietic Stem Cell Transplantation to Predict the Relapse of Hematopoietic Neoplasm Patients after Transplantation: Retrospective Data from a Single Center in China

Objective: To evaluate the changes of gene variation in patients with hematological neoplasms at the time of diagnosis and after allogeneic hematopoietic stem cell transplantation (allo-HSCT), and the relationship between gene mutation and recurrence after transplantation. Methods: 76 patients with hematological neoplasms were analyzed retrospectively, including 69 acute myeloid leukemia, 21 acute lymphoblastic leukemia, 5 myelodysplastic syndrome, 1 mixed acute leukemia and 1 chronic myelomonocytic leukemia. The median age was 37 (7-63) years, with 52 males and 45 females. Among 97 patients, 21 were matched sibling donor HSCT (MDS-HSCT), 14 were matched unrelated donor HSCT (MUS-HSCT), and 62 were haploidentical HSCT (haplo-HSCT). There were 88 cases of myeloablative conditioning regimen and 9 cases of non-myeloablative conditioning regimen. All patients underwent next generation sequencing (NGS) of hematological neoplasms variation genes at the time of diagnosis and 28 days after transplantation. Results: Primary and Secondary variations were detected in 89 of 97 patients during diagnosis. Common variations include CEBPA (18/97), NRAS (13/97), FLT3 (12/97), DNMT3A (11/97), TP53 (9/97), etc. After transplantation, only 29 patients had primary and Secondary variations, including ABCB1 (30/97), CYP2C19 (13/97); The number of other variations did not exceed 3 cases. The above NGS detection results suggest that the number of primary and Secondary variations after transplantation is significantly reduced (p=0.019), and ABCB1 and CYP2C19 are the main variation forms. The membrane related protein encoded by ABCB1 is a member of the ATP binding cassette (ABC) transporter superfamily, and CYP2C19 is a drug metabolizing enzyme, both of which are involved in drug metabolism. Single Nucleotide Polymorphisms (SNP) variations were detected in 52 of 97 patients at diagnosis, and GATA2 (27/97) and TET2 (25/97) variations were the most common variation forms. SNP variations of GATA2 and TET2 increased significantly after transplantation, 59/97 and 54/97 respectively. The increase of GATA2/TET2 double variation was more significant after transplantation (19/97 vs. 46/97, P<0.001). The increased variation frequency of GATA2 and TET2 after transplantation may be related to the mixed chimerism at the early stage of transplantation, which needs to be observed for a long time. Furthermore, we analyzed the relationship between gene variation and recurrence of 97 patients with hematological neoplasms at the time of diagnosis and after allo-HSCT. Eleven of 97 patients recurred after transplantation. The single factor competitive risk model showed that the presence of primary and Secondary variations after transplantation was an independent risk factor for recurrence (P=0.017) (Figure 1). The primary and secondary variations before transplantation, SNP variations before and after transplantation had no effect on recurrence after transplantation. The schemes of transplantation in 29 patients with primary and secondary variations after transplantation were analyzed, including 9 cases of MSD-HSCT, 14 cases of haplo-HSCT, and 6 cases of MUD-HSCT. It suggests that relative donors are more likely to have primary and secondary variations related to diseases. We used Fisher's Exact Test to analyze the relationship between ASXL1, TP53, GATA2, RUNX1 and other high-risk variations at the time of diagnosis/after transplantation and recurrence, and did not find that the presence of these gene variations would increase the risk of recurrence after transplantation. Conclusion: The NGS gene variation detection before and after transplantation can predict the recurrence after transplantation. Large samples and long-term monitoring are also needed to find a more accurate variation pattern to predict the recurrence of hematological neoplasms after transplantation.

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

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

A 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 > 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.

Comparison of Non-Myeloablative Conditioning Regimens Flu/Bu2, Flu/Mel 100 and Flu/TBI in Patients with AML and MDS

Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative treatment modality for patients with myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). Non-myeloablative (NMA) conditioning regimens are used to decrease toxicity, making HSCT more tolerable and available to older patients or patients with co-morbidities. It remains unclear as to which NMA regimen leads to superior outcomes. Methods: We retrospectively compared outcomes of 3 NMA regimens in 98 patients with AML or MDS undergoing allogeneic HSCT from January 2017 to December 2021. The 3 regimens were: Flu/Mel 100: fludarabine 40 mg/m2 days -5 to -2, melphalan 100 mg/m2 day -2; Flu/Bu2: fludarabine 30 mg/m2 days -6 to -2, busulfan 130 mg/m2 days -3 to -2; Flu/TBI: fludarabine 30 mg/m2 days -4 to -2, total body irradiation 200-300 cGY on day-1. Patients conditioned with Flu/Mel 100 or Flu/Bu2 also received rabbit anti-thymocyte globulin 4-6 mg/kg. Graft versus host disease (GVHD) prophylaxis consisted of tacrolimus and low dose methotrexate for patients receiving Flu/Mel 100 or Flu/Bu2, and sirolimus, cyclosporine and mycophenolate mofetil for patients conditioned with Flu/TBI. Continuous variables were compared between conditioning regimens using Pearson's Chi-squared test or Fisher's exact test. PFS and OS survival probability and survival times were estimated with Kaplan-Meyer(K-M) procedure. To compare survival distributions between conditioning regimens, a log-rank test was used. We report 24-month survival probabilities in months with corresponding 95% confidence intervals. Results: Patient demographics were balanced between the 3 groups including age (range 54-80), gender, disease risk and cell source (Table 1). 24-month progression free survival (PFS) was not different between the groups: Flu/Mel 100 was 70% (47%-100%), Flu/Bu2 was 49% (39%-63%), and Flu/TBI was 33% (18%-61%) (p=0.3). For Flu/Mel 100 the 24-month overall survival (OS) was 70% (47%-100%), Flu/Bu2 was 53% (42%-66%), Flu/TBI was 32% (17%-61%) which was not statistically different ( p=0.3) (Figure 1). There was no difference between the 3 groups for non-relapse mortality (NRM) ( p=0.46). The incidence of all grade acute GVHD was 70% for Flu/Mel 100, 66% for Flu/Bu2 and 76% for Flu/TBI ( p=0.70). There was no difference in the incidence of chronic GVHD between the groups; Flu/Mel 100 50%, Flu/Bu2 55%, Flu/TBI 57% (p>0.99). Conclusions: All three NMA regimens were found to be statistically equivalent. NRM, PFS, OS and the incidence of acute and chronic GVHD was not statistically different between the groups. A limitation of the study is the relatively small number of patients in the Flu/Mel 100 group. Further study with a larger sample size is needed to evaluate for small differences between the regimens.

Outcomes of Treosulfan Vs. Busulfan Based Conditioning Regimens in Adult Patients Undergoing Allogeneic HSCT: Real Life Data from a Single Center

Introduction The type of conditioning regimen has a great impact on the outcome of patients who undergo allogeneic HSCT since graft versus host disease (GVHD), infections, regimen related organ and tissue toxicities are among the most important causes of post-transplant mortality. Despite the regimen related toxicity profile of busulfan, supported by information from the results of clinical trials and real-world data, it is still commonly used worldwide. Treosulfan has advantages in terms of dose of administration, lower incidence of sinusoidal obstruction syndrome and lower neurotoxicity. We aimed to retrospectively investigate outcomes and compare results of patients who underwent matched and haploidentical allogeneic HSCT with treosulfan based or busulfan based reduced intensity conditioning, non-myeloablative conditioning and myeloablative conditioning regimens in our institution. Methods From September 2016 to November 2022, treosulfan was administered to 94 patients while 85 patients received busulfan. We analyzed outcomes as regimen related-toxicity, chronic and acute GVHD, overall survival, non-relapse mortality, relapse related mortality and fungal infection. The myeloablative dose of busulfan was 12.8 mg/kg while it was 9.6 mg/kg for the non myeloablative regimen which was combined with fludarabine. The myeloablative dose of treosulfan was 42 mg/m2 while a dose range of 30-36 mg/m2 was administered for the reduced intensity conditioning. Results The median follow up was 14 months for the treosulfan group while it was 11 months for the busulfan group (p = 0.16). Regimen related toxicity, which was monitored during the hospital stay and 3 months after discharge were 11.7% and 7.1% for treosulfan and busulfan respectively and were similar between two groups. Extensive chronic GVHD was encountered in 15.7% of the patients in the treosulfan group compared to 32.1% in the busulfan group (p < 0.001). Similarly, chronic skin GVHD was observed in 3.6% of the patients who received treosulfan while it was seen in 22.6% of the busulfan group (p < 0.001). Acute GVHD (grade 3 or higher) was encountered in 32.2% of the patients within the treosulfan group while it was encountered in 31.6% of the patients in the busulfan group. Overall survival was 47.5% and 36.5 % in the treosulfan group and busulfan groups respectively. The relapse-related mortality was 17 % in the treosulfan group while it was 34% in the busulfan group. Fungal infection was observed in 23.4% and 36.5% of the patients in treosulfan and busulfan groups respectively. Conclusion Treosulfan, with a lower chronic GVHD incidence and similar regimen related toxicity profile appears to be a safe alternative to busulfan and prospective randomized controlled trials are needed to confirm the results in our study. Keywords: Busulfan; treosulfan; conditioning regimen; stem cell transplantation

Impact of Publicly Reported Center Specific Analysis on Patient Selection Practices for Hematopoietic Stem Cell Transplantation

Introduction Public reporting of outcomes drives healthcare improvement in many fields, including hematopoietic cell transplantation (HCT), although with possible unintended consequences. The Center for International Blood & Marrow Transplant Research (CIBMTR) publishes an annual Center-Specific Survival Analysis (CSA), which compares HCT centers' observed 1-year overall survival (OS) with their statistically modeled expected 1-year OS, with 95% confidence intervals (CI). Centers with OS within their 95% CI receive a 0 score, indicating as expected outcomes. Those with OS below / above their 95% CI receive a -1 / +1 score, indicating below / above expected OS, respectively. After a -1 report, centers may change their patient selection criteria, causing unintentional systematic exclusion of patient populations who could benefit from HCT. We analyzed how the CSA report influences patient selection practices among centers receiving a -1 score. Methods Centers receiving a -1 report between 2012 and 2016 that had ‘as expected’ survival in the preceding 2 years were classified as newly below expected OS centers (NBCs). The year of their -1 report was used as the index year. Centers with ‘as expected’ OS in the 3 years before and after each index year were identified as control centers, reflecting expected evolution of patient selection in the HCT field. The patient population variables analyzed are shown in Table 1. The difference in patient population characteristics in the 3 years before vs the 3 years after the index years defined the change in patient selection behavior at the NBCs and the controls. A multivariate model adjusting for baseline patient population characteristics and center size was used to compare the change in patient population from before and after the index year in the NBCs and that of the controls. The difference in differences (ΔinΔ) were calculated as ΔNBC - ΔControl. A significance threshold of p<0.01 was used to account for multiple testing. Results After adjusting for overall trends, center size, and baseline patient population characteristics, no differences in patient selection behavior meeting the pre-specified threshold for statistical significance were identified when comparing the NBCs (n=24 centers) with the controls (n=195 centers). In the 3 years following the index years, 4,150 and 25,013 patients were transplanted at NBCs and controls, respectively. The proportion of patients receiving reduced intensity or non-myeloablative conditioning regimens decreased 4.1% in NBCs and increased 5.0% in controls, for a net difference of -9.1% (95% CI: -16.7% to -1.6%, p=0.02). All other patient characteristic proportions changed in the same direction at NBCs and controls, albeit to varying degrees (Table 1). In some high-risk characteristics, (e.g. HCT-CI > 3), a greater increase was seen at NBCs vs controls (ΔinΔ 2.1% 95% CI: -2.8% to 6.9%, p=0.40). In others, (e.g. age 60+ years), a greater increase was seen at controls vs NBCs (ΔinΔ -2.6% 95% CI: -5.9% to 0.7%, p=0.12). To capture a holistic measure of centers' patient population risk, the predicted 1-year survival was compared in the NBCs vs controls using the logistic regression model generated for each year's CSA. The predicted OS increased by 3.08% and 3.30% in the NBCs and controls respectively, with no statistically significant difference (-0.23%, 95% CI: -1.4% to 0.9%, p=0.70, Figure 1). The observed overall survival (adjusted for predicted 1 year OS) also increased in both BECs and controls by 0.9% and 4.5% respectively, without statistically significant difference (-3.6%, 95% CI: -6.7% to -0.7%, p=0.02). Discussion For centers receiving a -1 report, no statistically significant changes were seen in patient population characteristics in the following 3 years when compared to centers with OS was as expected. There was variability in the changes in high-risk patient characteristics at the NBCs relative to the controls, and in some cases more patients with high-risk characteristics were selected at these centers compared to those at controls. The change in predicted overall survival at 1 year, a summary indicator of survival risk, was similar between BECs and control centers. Although the number of patients in centers with below expected OS was small, these findings suggest the public reporting of outcomes in HCT in the US does not unintentionally affect access to HCT for high-risk patients at NBCs.

Acute Pulmonary Toxicity after Allogeneic Stem Cell Transplantation Using Total Body Irradiation-Based Conditioning- Myeloablative vs. Non-Myeloablative Regimens

Allogeneic hematopoietic stem cell transplantation (HSCT) is associated with a high risk of acute pulmonary toxicity, especially with total body irradiation-based (TBI) conditioning regimens. High-grade acute pulmonary toxicity occurs in ∼30% of patients when a myeloablative regimen is utilized (∼12-14 Gy). The risk of pulmonary toxicity with non-myeloablative regimens (∼2 Gy) is not well described. We evaluated the incidence and predictors of acute pulmonary toxicity after HSCT comparing myeloablative and non-myeloablative TBI-based conditioning regimens. All adult (≥ 18 y/o) patients undergoing allogeneic HSCT with TBI (1995-2020) at our institution were evaluated. The dose to the lungs was attenuated to 7-10 Gy in all patients undergoing myeloablative TBI. Acute pulmonary toxicity, occurring within 6 months of HSCT, was scored using CTCAE v5.0. The incidence of acute pulmonary toxicity was calculated using the Kaplan-Meier method, and logistic regression was performed to assess for independent risk factors. Five hundred fifty-two patients were included the analysis (myeloablative- 378; non-myeloablative- 174). Myeloablative TBI was most commonly 13.5 Gy/9Fx (335/378), while non-myeloablative TBI was delivered most often as 2 Gy/1Fx (165/174). Patients undergoing myeloablative TBI were younger than non-myeloablative patients (43 vs 58 years, p<0.001), but baseline pulmonary function parameters were similar. At 6 months after transplant, the cumulative incidences of any acute pulmonary toxicity for patients receiving myeloablative and non-myeloablative TBI were 39% and 33%, respectively (p = 0.11). The risk of low-grade (1-2) and high grade (3-5) pulmonary toxicity was 10% vs 12% (p = 0.59) and 28% vs 21% (p = 0.05), respectively, comparing myeloablative and non-myeloablative TBI. Proportions of high-grade toxicities among the myeloablative and non-myeloablative cohorts were as follows: infectious pneumonia (31% and 49%), bronchopulmonary hemorrhage (25% and 3%), respiratory failure NOS (17% and 10%), pleural effusion (5% and 1%), and pneumonitis (4% and 0%). Female sex (OR 1.52, p = 0.05) and refractory disease at the time of transplant (OR 2.25, p = 0.03) were associated with a higher risk of severe pulmonary toxicity on logistic regression. Younger age (OR 0.99, p = 0.35) and non-myeloablative TBI (OR 0.21, p = 0.60) were not significantly associated with a lower risk. The risk of acute pulmonary toxicity was high with both myeloablative and non-myeloablative TBI-based regimens, though high-grade toxicity was modestly higher in the myeloablative cohort. A better understanding of pulmonary toxicity in the setting of non-myeloablative TBI (∼2 Gy) is needed.

ATG versus PTCy in matched unrelated donor haematopoietic stem cell transplantations with non-myeloablative conditioning.

Graft-versus-host disease (GvHD) is a serious complication of allogeneic haematopoietic stem cell transplantation (HSCT). Both anti-thymocyte globulin (ATG) and post-transplant cyclophosphamide (PTCy) are used as lymphocyte-depleting strategies, yet a systematic comparison of transplantation outcomes between these two methods in matched unrelated donors (MUD) transplantations with non-myeloablative conditioning (NMC) is lacking. Adult patients with haematological malignancies who had undergone MUD HSCT with NMC regimens between 2014 and 2021 at 2 centres in Amsterdam (ATG: n = 95, PTCy: n = 90), were included in this retrospective study. Patient characteristics were comparable between the groups. The cumulative incidence of acute GvHD grade II-IV was 48% in the ATG group compared to 21% in the PTCy group (p < 0.001). The 3-year moderate/severe chronic GvHD was similar in both groups (p = 0.69). While the relapse rate was comparable between the groups (ATG 31% vs. PTCy 34%, p = 0.94), non-relapse mortality tended to be higher in the ATG group (17% vs. 9%, p = 0.069). Overall survival was similar in both groups (p = 0.12). In conclusion, PTCy-based regimens resulted in a significantly lower rate of acute GvHD than ATG-containing regimens in MUD transplantations with NMC. Whether PTCy results in improved overall survival as compared to ATG needs to be elucidated in larger prospective studies.

The treatment of relapsed/refractory anaplastic large cell lymphoma expressing the anaplastic lymphoma kinase: a single-center experience

The treatment of relapsed/refractory anaplastic large cell lymphoma expressing the anaplastic lymphoma kinase: a single-center experience

Comparison of reduced intensity and nonmyeloablative conditioning for adults with acute myeloid leukemia undergoing allogeneic hematopoietic cell transplantation in first or second remission.

Reduced intensity conditioning (RIC) and nonmyeloablative (NMA) conditioning regimens have expanded use of allogeneic hematopoietic cell transplantation (HCT) in AML to include older and medically less-fit patients, but relative efficacies and toxicities remain poorly defined. Here, we analyzed outcomes from 343 adults transplanted in remission after RIC (n = 137) or NMA (n = 206) conditioning between 2006 and 2021. The characteristics of RIC and NMA HCT patients were similar except that RIC patients were younger and their time between most recent remission achievement and allografting was shorter. There were no significant differences in relapse risk, relapse-free survival (RFS), overall survival (OS), and non-relapse mortality (NRM) between RIC and NMA HCT patients, both overall (relapse: hazard ratio [HR] = 0.80, P = 0.27; RFS: HR = 0.93, P = 0.61; OS: HR = 0.93, P = 0.66; NRM: HR = 1.13, P = 0.59) and when patients were stratified by pre-HCT measurable residual disease (MRD) status. After multivariable adjustment, there was no statistically significant association between conditioning intensity and relapse (HR = 0.69, P = 0.088), RFS (HR = 0.86, P = 0.37), OS (HR = 0.89, P = 0.49), or NRM (HR = 1.37, P = 0.19). In this non-randomized cohort of adults undergoing allografting for AML in first or second remission at our center, we could not detect statistically significantdifferences in outcomes between those assigned to RIC and those assigned to NMA conditioning.

Efficacy and Safety of a Novel Non-Myeloablative Conditioning Regimen for Hematopoietic Cell Transplantation in Adults with Severe Aplastic Anemia

Introduction The distinct "age effect" that exists in severe aplastic anemia (SAA) following hematopoietic cell transplantation (HCT) favors the use of reduced intensity conditioning regimens in patients >40 years. For older adults, overall survival and disease-free survival (DFS) is reduced with increasing age and unrelated donor transplant are associated with higher rates of graft failure, Epstein-Barr virus (EBV) reactivation, and post-transplant lymphoproliferative disorders (PTLD) (Rice C, et al. BBMT 2019.). To overcome this, a novel, non-myeloablative conditioning regimen called FCR, which consists of fludarabine, cyclophosphamide, and rituximab, was designed at Vanderbilt University Medical Center (VUMC) and the associated VA Tennessee Valley Healthcare System (TVHS) for use in all SAA patients. This regimen was subsequently evaluated in the first 11 SAA patients treated at VUMC/TVHS and found to result in lower toxicity, graft-versus-host disease (GVHD), and viral reactivation with no graft failure or relapse compared to historical controls (Gatwood KS, et al. BMT 2018.). Given these initial favorable results, FCR has now been expanded as the preferred conditioning regimen for all SAA patients undergoing HCT at our center, warranting follow-up evaluation in a larger cohort. Methods Utilizing institutional registries, all SAA patients were identified who underwent first allogeneic HCT using an FCR regimen (Figure 1) between January 2016 and May 2022. VUMC and TVHS Institutional Review Boards approved this retrospective analysis. Outcomes analyzed included time to engraftment, incidence of graft failure, incidence of acute GVHD (aGVHD) and chronic GVHD (cGVHD), rate of viral reactivation, post-HCT disease status, and number of inpatient hospital days through day +100. An analysis of 1-year GVHD-free, relapse-free survival (GRFS) was conducted in evaluable patients, with differences between the curves determined using log-rank tests. Results Twenty-four SAA patients underwent HCT from January 26, 2016 to May 11, 2022, the majority of which were male with a median age of 43.5 years (range: 22-62). All patients received at least one line of therapy prior to HCT with the most common treatment being the combination of cyclosporin A with anti-thymocyte globulin with or without eltrombopag and/or corticosteroid. Median time from diagnosis to transplantation was 434.5 days (range: 84-6408). Patients received transplants from matched related (n=8), haploidentical (n=2), and matched unrelated donors (n=14) using either a peripheral blood (PB) or bone marrow (BM) stem cell source (PB=15, BM=9). Median time to neutrophil and platelet engraftment was 14 days (range: 10-25) and 18 days (range: 10-38), respectively. No patients experienced graft failure. At median follow-up of 806.5 days (range: 72-2180) post-transplant, all patients were alive and in remission. No patients developed grade III-IV aGVHD and no differences in grade I-II aGVHD rates were noted based on stem cell source. By date of last follow-up, mild to moderate cGVHD graded per 2014 NIH criteria developed in 7 and 3 patients, respectively. There were no cases of severe cGVHD. Only 2 patients experienced a viral reactivation (cytomegalovirus [CMV]=1, EBV=1) by date of last follow-up. The case of EBV reactivation did not require treatment and did not progress to PTLD. The median number of inpatient hospital days required post-engraftment through the first 100 days post-transplant was 5 days (range: 0-21). The unadjusted Kaplan-Meier estimate of 1-year GRFS was 86.3% (95% CI: 72.8%-100%) (Figure 2), with moderate cGVHD accounting for all GFRS events in the study cohort. Conclusions The use of our novel non-myeloablative conditioning regimen in SAA is well tolerated with 0% non-relapse mortality and 100% DFS with low GVHD rates at 1-year post-transplant. Despite a high-risk population with median age >40 years, using primarily matched unrelated donors, and majority peripheral blood stem cell source, there were no deaths and rates of complications remained low. This study further supports the findings of our previous study, redemonstrating low rates of toxicity, severe GVHD and viral reactivation with no graft failure, relapse, or mortality. The use of these regimens needs to be validated in a larger cohort as they have the potential to provide a new standard of care for pre-HCT conditioning in SAA patients. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Naïve T Cell-Depleted Hematopoietic Graft Combined with Solid Organ Transplantation As Strategy to Induce Tolerance By Transient Mixed Chimerism

BACKGROUND The major challenge of solid organ transplantation (SOT) is to prevent graft rejection. The chronic use of pharmacological immunosuppression has been associated with increased rates of infection, cardiovascular, metabolic, endocrine disorders, and cancer. The induction of chimerism by donor hematopoietic stem cell transplantation (HSCT) together with SOT is an active tolerance induction approach. Here, we present a new model for inducing transient mixed chimerism in 2 patients undergoing SOT employing a non-myeloablative conditioning (NMA) regimen and a partially T cell-depleted (TCD) graft consisting of CD34+ hematopoietic progenitor cells and CD45RA− memory lymphocytes. METHODS SOT and HSCT were performed at University Hospital La Paz, Madrid. Bone marrow harvesting was performed on the iliac crest and lumbar and dorsal vertebrae of the deceased donor for patient#1 and mobilized leukoapheresis from sibling donor for patient#2. First we obtained the enriched by CD34+ selection using the CliniMACS system (Miltenyi Biotec) and afterwards the CD45RA− cells were purified. Lineage-specific chimerism analysis was analyzed using quantitative real-time polymerase chain reaction. Immune cell recovery was monitored by multiparametric flow cytometry. We obtained the permission of the Organización Nacional de Trasplantes and the informed consent was obtained from the patient and donor and/or caregivers. RESULTSPatient 1 A 15-year-old boy was diagnosed with intestinal epithelial dysplasia in 2008. After two previous intestinal and multivisceral acute cellular rejections forced a third MVT. With the imptemption to induce donor tolerance, a T cell-depleted bone marrow graft from the same deceased donor was employed. Bone marrow harvesting was performed obtaining a total volume of 141 ml with 4x109 total nucleated cells. Peripheral blood was obtained after unclasping the thoracic aorta. The stem cell fraction from bone marrow was enriched by CD34+ selection, obtaining 8.75x105/kg CD34+cells/kg. Memory lymphocytes were purified and aliquots containing 1x106/kg CD3+CD45RO+ and 2.1x104/kg CD3+CD45RA+ T cells. Both products were cryopreserved. The conditioning regimen before HSCT included fludarabine and cyclophosphamide. On day 88 after MVT, we infused all the CD34+ cells and 1x106/Kg CD3+CD45RO+ T cells. The CD3+CD45RO+ T cells were also infused periodically on a monthly basis for 1 year. Donor chimerism in CD3+ T cells ranged from 0.05 to 5.1 during the first year after HSCT. We observed a peak of the percentage of regulatory T cells (Tregs). No degree of graft-versus-host disease (GvHD) was observed, and the patient became independent of total parenteral and enteral nutrition. Serial follow-up intestinal biopsies did not show any sign of immune rejection. The patient continued to receive sirolimus to maintain drug concentrations at 6 ng/ml as the only immunosuppression treatment. No signs of rejection were detected after 27 months of follow-up. Patient 2 A 49-year-old woman was diagnosed with chronic kidney failure secondary to rapidly progressive glomerulonephritis. The patient had received 3 previous kidney transplants from deceased donors. A kidney transplant from her sibling was performed in March 2021. Hematopoietic progenitor cells were obtained from mobilized peripheral blood leukapheresis. A NMA conditioning regimen employing total lymphoid irradiation (8 Gy) with antithymocyte globulin (7.5 mg/kg). Two weeks after the kidney transplantation, we infused a graft consisting of 1.27x107/kg CD34+, 4.43x106/kg CD3+CD45RO+, and 5x104/kg CD3+CD45RA+ cells. Controls for hematopoietic chimerism demonstrated the presence of transient mixed hematopoietic chimerism during the first 2 months after SOT of between 0.1% and 40% CD3+ cells. The patient continued on monotherapy with tacrolimus. Immune reconstitution analysis showed a Treg peak. The patient did not have acute rejection, GvHD, viral reactivations or episodes of bacterial infection during the 17 months of follow-up. CONCLUSIONS We describe for the first time the use of non-myeloablative conditioning and a CD45RA− T cell-depleted graft to induce transitory mixed chimerism using both hematopoietic progenitors and a solid organ coming from the same donor, for tolerance induction purposes. The patients continue to progress favorably 17 months or more after SOT, receiving immunosuppressive monotherapy. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal