Myeloablative Transplantation Research Articles

Real-World Impact of Routine Addition of Antithymocyte Globulin to Standard GVHD Prophylaxis in Myeloablative Unrelated Donor Transplants: Important Gains in Graft-versus-Host Disease Prevention though No Difference in Overall Survival

Introduction: Antithymocyte globulin (ATG) has been demonstrated to reduce the incidence of graft-versus-host disease (GVHD); however, it remains controversial whether these gains are offset by an increase in relapse. Methods: We conducted a retrospective historical control study consisting of patients (n = 210) who underwent myeloablative allogeneic hematopoietic stem-cell transplantation (HSCT) from 2014 to 2020. Results: The incidence of acute GVHD was lower in the ATG group (51.4%) than the non-ATG group (control) (70.0%, p = 0.010). The incidence of chronic GVHD was also lower in the ATG group at 1-year (36.4% vs. 62.9%, p < 0.001) and 2-year (40.0% vs. 65.7%, p < 0.001) post-HSCT. The mortality due to GVHD was higher in the control (18.5%) than the ATG group (4.3%; p = 0.024). The severe GVHD-relapse-free survival was higher in the ATG group (36.4%) than the control (12.9%; p < 0.001). Nevertheless, the 2-year overall survival was similar. Conclusion: Our results confirm the effectiveness of ATG in prevention of GVHD in the real-world setting and enhanced GVHD-free survival. An important result is the equalization of overall survival between the ATG and control groups at 1- and 2-year post-HSCT and implies that earlier GVHD-associated mortality may be offset by later relapse mortality producing similar overall survival over time.

Incidence, risk factors and therapy response of acute graft-versus-host disease after myeloablative hematopoietic stem cell transplantation with posttransplant cyclophosphamide.

Posttransplant cyclophosphamide, sirolimus and mycophenolate mofetil (PTCy/siro/MMF) constitutes an innovative and well-tolerated acute graft-versus-host disease (aGVHD) prophylaxis after allogeneic stem cell transplantation (allo-HSCT), but risk factors for aGVHD incidence and therapy failure in this setting are scarce. This study prospectively registered all consecutive adult patients with hematologic malignancies who received a myeloablative allo-HSCT using PTCy/siro/MMF prophylaxis at our institution between 2017 and 2023. A total of 385 patients were included, of whom 44%, 34% and 22% were transplanted from matched sibiling, matched unrelated and haploidentical donors, respectively. The 180-day cumulative incidence of aGVHD was 21% (95% confidence interval [CI] 17-25%) for grade II-IV and 11% (95% CI 8-14%) grade III-IV aGVHD. The use of haploidentical donors was associated with an increased risk of severe aGVHD. Among 75 patients receiving first-line systemic corticosteroids, 49% achieved a sustained complete response, while 23% and 24% developed steroid-dependent (SD-aGVHD) and steroid-refractory aGVHD (SR-aGVHD), respectively. SR-aGVHD was associated with worse salvage treatment response and overall survival compared to SD-aGVHD. The 1-year cumulative incidence of aGVHD-related mortality was 5.4% (95% CI, 3.3-8.1). Risk factors for aGVHD-related mortality included haploidentical donors, older donors, diagnosis of myeldysplastic neoplasms, and grade IV aGVHD. This study confirms a low incidence aGVHD with PTCy/siro/MMF prophylaxis. SR-aGVHD showed poorer response to salvage therapies and worse survival, while haploidentical donors and older donor age were negative predictors for aGVHD-related deaths.

From Marrow to Bone and Fat: Exploring the Multifaceted Roles of Leptin Receptor Positive Bone Marrow Mesenchymal Stromal Cells.

The bone marrow (BM) stromal cell microenvironment contains non-hematopoietic stromal cells called mesenchymal stromal cells (MSCs). MSCs are plastic adherent, form CFU-Fs, and give rise to osteogenic, adipogenic, chondrogenic progenitors, and most importantly provide HSC niche factor chemokine C-X-C motif ligand 12 (CXCL12) and stem cell factor (SCF). Different authors have defined different markers for mouse MSC identification like PDGFR+Sca-1+ subsets, Nestin+, or LepR+ cells. Of these, the LepR+ cells are the major source of SCF and CXCL12 in the BM microenvironment and play a major role in HSC maintenance and hematopoiesis. LepR+ cells give rise to most of the bones and BM adipocytes, further regulating the microenvironment. In adult BM, LepR+ cells are quiescent but after fracture or irradiation, they proliferate and differentiate into mesenchymal lineage osteogenic, adipogenic and/or chondrogenic cells. They also play a crucial role in the steady-state hematopoiesis process, as well as hematopoietic regeneration and the homing of hematopoietic stem cells (HSCs) after myeloablative injury and/or HSC transplantation. They line the sinusoidal cavities, maintain the trabeculae formation, and provide the space for HSC homing and retention. However, the LepR+ cell subset is heterogeneous; some subsets have higher adipogenic potential, while others express osteollineage-biased genes. Different transcription factors like Early B cell factor 3 (EBF3) or RunX2 help maintain this balance between the self-renewing and committed states, whether osteogenic or adipogenic. The study of LepR+ MSCs holds immense promise for advancing our understanding of HSC biology, tissue regeneration, metabolic disorders, and immune responses. In this review, we will discuss the origin of the BM resident LepR+ cells, different subtypes, and the role of LepR+ cells in maintaining hematopoiesis, osteogenesis, and BM adipogenesis following their multifaceted impact.

Total body irradiation versus thiotepa/busulfan-based conditioning regimens for myeloablative allogeneic stem cell transplantation in adults with acute lymphoblastic leukemia.

Total body irradiation (TBI)-based conditioning regimens are generally recommended for allogeneic HSCT (allo-HSCT) in patients with acute lymphoblastic leukemia (ALL). Recent evidence suggests that modern chemotherapy-based regimens may be as effective. This multicenter retrospective study compared the clinical outcomes of myeloablative allo-HSCT with thiotepa, busulfan, and cyclophosphamide/fludarabine (TTB) to TBI-based conditioning. Between 2002 to 2018, 63 and 114 patients received TTB- and TBI-based conditioning regimens, respectively. The 5-year cumulative incidence of relapse was lower in the TBI cohort compared to the TTB cohort (30% [95% CI, 22-38] versus 47% [95% CI, 36-59]; P = 0.03). Multivariate analysis identified T-ALL, Ph-negative B-ALL, and measurable residual disease associated with a higher relapse risk. The 5-year cumulative incidence of non-relapsed mortality (NRM) was significantly lower with TTB (12% [95% CI, 5-20]) compared to TBI (25% [95% CI, 18-33]) (P = 0.001). Multivariate analysis found TBI conditioning, older age, and advanced stages of ALL at transplantation associated with a higher NRM. No statistical difference was seen in overall survival (49% [95% CI, 40-58] and 46% [95% CI, 35-60]) in the TBI and TTB groups, respectively; P = 0.9). The study suggests that TTB-based conditioning may be a promising option for ALL patients undergoing allo-HSCT, as it resulted in similar OS and lower NRM than TBI-based conditioning.

42 Severe Combined Immunodeficiency Due To A Monoallelic ITPR3 Variant Presenting With Lymphohistiocytosis And Bone Marrow Failure Treated With Myeloablative Hematopoietic Cell Transplantation

42 Severe Combined Immunodeficiency Due To A Monoallelic ITPR3 Variant Presenting With Lymphohistiocytosis And Bone Marrow Failure Treated With Myeloablative Hematopoietic Cell Transplantation

Durable engraftment after pharmacological pre-transplant immune suppression followed by reduced-toxicity myeloablative haploidentical stem cell transplantation in highly HLA-immunized adults with sickle cell disease.

Allogeneic stem cell transplantation (Allo-SCT) is the only rapidly available curative treatment modality in patients with severe sickle cell disease (SCD). The development of reduced-toxicity myeloablative conditioning (RT-MAC) regimen and the use of partially matched family donors with post-transplantation cyclophosphamide (PT-Cy) have widened the access to Allo-SCT. Antibodies against donor-specific HLA (DSA) increase the risk of engraftment failure in HLA mismatched Allo-SCT. We report the results of five patients with SCD, whereas three with DSA, who underwent an unmanipulated haploidentical stem cell transplantation (Haplo-SCT) after a busulfan-based RT-MAC regimen with PT-Cy. To reduce the risk of engraftment failure, a sequential two courses pharmacological pre-transplant immune suppression (PTIS) phase was added prior to the conditioning regimen. All patients engrafted successfully. The procedure was well tolerated. None of the patients developed acute GVHD, whereas one developed moderate chronic GVHD. After a median follow-up of 5 years (range, 2.2-9), all patients are free of pain with excellent quality of life. Our report shows that Haplo-SCT after a RT-MAC regimen is feasible and safe with stable long-term engraftment and excellent disease control. The risk of graft failure can be abrogated by adding a PTIS phase prior to initiating the conditioning regimen.

Immune reconstitution, vaccine responses, and rituximab use after ex-vivo CD34-selected myeloablative allogenic hematopoietic cell transplantation.

Myeloablative T cell depleted (CD34-selected) hematopoietic cell transplantation (HCT) is associated with less acute and chronic graft versus host disease (GVHD). We aimed to examine vaccine responses in relation to immune reconstitution and post HCT rituximab administration in this population. This single center retrospective study included 251 patients with hematological malignancies who received a first CD34-selected HCT between 2012 and 2015. Of 251 patients, 190 were alive 1 year after HCT. Among the entire population, 77 (30.7%) patients were vaccinated. After vaccine administration, 35/44 (80%), 30/75 (40%), 27/36 (75%), 33/65 (51%), 34/51 (51%), 22/28 (79%) and 20/34 (59%) of evaluable patients had protective antibody titers for haemophilus influenzae type B (Hib), Pneumococcus, Tetanus, Diphtheria, Pertussis, hepatitis A (HAV), and hepatitis B (HBV) respectively. Responders to the pneumococcal vaccine had a higher CD45RA T cell count than non responders, with 12/18 patients (66.7%) vs 11/32 (34.4%) p = 0.04. For pneumococcal vaccine, there was also a trend to higher total lymphocyte B cell count in responders vs non responders p = 0.06. Rituximab post HCT was given to 59/251 (23.5%) patients. No difference was found in immune reconstitution patterns for rituximab use between vaccine responders and not. Recipients of CD34-selected HCT may respond to vaccination, and T and B cell subsets could be useful to predict vaccine response.

Graft CD8 T-cell-based risk system predicts survival in antithymocyte globulin-based myeloablative haploidentical peripheral blood stem cell transplantation.

This study investigated the cellular composition of peripheral blood grafts for anti-thymocyte globulin (ATG)-based myeloablative haploidentical haematopoietic stem cell transplantation (haplo-HSCT). Clinical characteristics were retrospectively evaluated in a training cohort with ATG-based myeloablative haplo-HSCT between January 2016 and February 2020 and confirmed in a validation cohort between March 2020 and June 2021. A higher dose of graft CD8+ T cells (≥ 0.85 × 108 kg-1) was significantly improved overall survival (OS;hazard ratio [HR], 1.750; P = 0.002) and disease-free survival (DFS; HR, 1.751; P < 0.001) in the training cohort, according to multivariate Cox regression analysis. Higher doses of mononuclear cells (MNCs) demonstrated better OS (HR, 1.517; P = 0.038) and DFS (HR, 1.532; P = 0.027). Older patient age (> 46 years), older donor age (≥ 50 years) and a higher refined disease risk index (rDRI) were also related to OS. A graft CD8+ T-cell risk system based on graft CD8+ T-cell dose, donor age and rDRI was constructed using a nomogram model after LASSO Cox regression analysis. It showed acceptable discrimination, with a C-index of 0.62 and 0.63, respectively. Graft CD8+ T-cell dose was negatively correlated with donor age (P < 0.001) and positively correlated with a higher lymphocyte percentage in the peripheral blood before mobilisation (P < 0.001). A higher CD8+ T-cell dose in peripheral blood-derived grafts improves patients' survival with ATG-based myeloablative haplo-HSCT. Younger donors with higher lymphocyte percentages improved patients' survival with an intermediate rDRI risk.

Similar Survival But Less Chronic GVHD in Antithymocyte Globulin-Based Myeloablative Haploidentical Transplant Compared With Matched Sibling Transplant for Adult T-cell Acute Lymphoblastic Leukemia/Lymphoma.

The annual number of human leukocyte antigen (HLA)-haploidentical allogeneic hematopoietic stem cell transplantation (haplo-HCT) is increasing steadily. Comparative studies about haplo-HCT versus HCT with HLA-matched sibling donors (MSD-HCT) have been tried in acute myeloid leukemia and B-cell acute lymphoblastic leukemia/lymphoma (ALL). Few studies were reported in adult T-cell ALL (T-ALL). In this retrospective study, a total of 88 consecutive patients with T-ALL were enrolled who underwent MSD-HCT (n = 24) and haplo-HCT (n = 64) with antithymocyte globulin (ATG)-based graft versus host disease (GVHD) prophylaxis between 2010 and 2022. Median follow-up for survivors was similar (43.5 [range: 7-88] months for MSD-HCT versus 43.5 (range: 6-144) months in the Haplo-HCT group). The 100-day cumulative incidence of grade II to IV acute GVHD (aGVHD) was similar, 33% (95% confidence interval [CI], 16%-52%) after MSD-HCT versus 44% (95% CI, 31%-55%) after haplo-HCT, P = 0.52. The cumulative incidences of grade III-IV aGVHD were 8% (95% CI, 1%-23%) in the MSD-HCT group and 5% (95% CI, 1%-12%) in the haplo-HCT group (P = 0.50). The 2-year cumulative incidence of chronic GVHD (limited and extensive) in the haplo-HCT, 11% (95% CI, 5%-20%) was significantly lower than that in the MSD-HCT group (42% [95% CI, 21%-62%], P = 0.002). The cumulative incidence of 4-year relapse rates (44% versus 37%, P = 0.56) and non-relapse mortality (7% versus 21%, P = 0.08) did not differ between these two groups. There were also no differences in 4-year overall survival (46% versus 47%, P = 0.44) and progression-free survival (49% versus 42%, P = 0.45) between these two groups. On multivariate analysis, using busulfan/fludarabine (BU/Flu) conditioning regimen was found to be associated with worse clinical outcome. Our results suggested that ATG-based haplo-HCT platform could work as an alternative to MSD-HCT for adult patients with T-ALL. Compared with MSD-HCT, haplo-HCT might carry a low risk for cGVHD.

Allogeneic bone marrow transplantation for patients with treatment-refractory Crohn's Disease

Background & aimsDurable remissions of Crohn's Disease (CD) have followed myeloablative conditioning therapy and allogeneic marrow transplantation. For patients with treatment-refractory disease, we used reduced-intensity conditioning to minimize toxicity, marrow from donors with low Polygenic Risk Scores for CD as cell sources, and protracted immune suppression to lower the risk of graft-versus-host disease (GVHD). Our aim was to achieve durable CD remissions while minimizing transplant-related complications. MethodsDNA from patients and their HLA-matched unrelated donors was genotyped and Polygenic Risk Scores calculated. Donor marrow was infused following non-myeloablative conditioning. Patient symptoms and endoscopic findings were documented at intervals after transplant. ResultsWe screened 807 patients, 143 of whom met eligibility criteria; 2 patients received allografts. Patient 1 had multiple complications and died at day 332 from respiratory failure. Patient 2 had resolution of CD symptoms until day 178 when CD recurred, associated with persistent host chimerism in both peripheral blood and intestinal mucosa. Withdrawal of immune suppression was followed by dominant donor immune chimerism in peripheral blood and resolution of CD findings. Over time, mucosal T-cells became donor-dominant. At 5 years after allografting, Patient 2 remained off all medications but had mild symptoms related to a jejunal stricture that required stricturoplasty at 6 years. At 8 years, she remains stable off medications. ConclusionsThe kinetics of immunologic chimerism after allogeneic marrow transplantation for CD patients depends on the intensity of the conditioning regimen and the magnitude of immune suppression. One patient achieved durable improvement of her previously refractory CD only after establishing donor immunologic chimerism in intestinal mucosa. Her course provides proof-of-principal for allografting as a potential treatment for refractory CD, but an immunoablative conditioning regimen should be considered for future studies.(ClinicalTrials.gov, NCT01570348)

Aurora Kinase a Inhibition for Gvhd and Relapse Prevention after Allogeneic HCT: Phase I Trial in Combination with Ptcy/Sirolimus

Introduction: With the wider use of post-transplant cyclophosphamide (PTCy) graft-versus-host disease (GVHD) prophylaxis, there is interest in replacing tacrolimus (TAC) with sirolimus (SIR, mTOR inhibitor) to avoid calcineurin inhibitor toxicity, maintain excellent GVHD control, and potentially allow for a greater graft-versus-tumor effect. mTOR and Aurora kinase A (AURKA) mediate CD28 costimulation in alloreactive T cells. SIR can only partially block CD28 costimulation. Adding selective AURKA inhibition to SIR following PTCy fully suppresses CD28 signal transduction, with synergistic GVHD prevention in mice (see ASH 2023 abstract ID 173376). AURKA inhibitors also have direct anti-leukemia activity. Here, we present the phase 1 dose escalation portion of a first-in-human clinical trial of PTCy plus SIR and VIC-1911 (VIC), a selective oral AURKA inhibitor, for GVHD and relapse prophylaxis after myeloablative allogeneic hematopoietic cell transplantation (alloHCT). Methods: This single-arm phase I dose escalation trial (NCT05120570) is designed to evaluate the pharmacodynamic potency of AURKA pathway suppression and the safety of PTCy/SIR/VIC. The primary endpoint of phase I is to identify the lowest biologically active dose of VIC, defined as &amp;lt;54% pH3ser10+ CD4+ T cells at day +21 (the lower confidence interval of the normal, pre-transplant frequency of pH3ser10+ CD4+ T cells - a marker of AURKA activity), that is safe with PTCy/SIR. Patients aged 18-60 years receive myeloablative conditioning of TBI alone at a dose of 1320 cGy. PTCy is given as 50 mg/kg on days +3 and +4, SIR on day +5 with levels targeting 8-12 ng/ml and tapered after day +100, and VIC given on days +5 to +45 at doses of 25, 50, or 75 mg BID. Patients undergoing myeloablative TBI-based alloHCT with PTCy/SIR plus mycophenolate mofetil (MMF), without VIC on a separate protocol, served as a control. Results: Proof-of-concept experiments with PTCy/SIR/alisertib (AURKA inhibitor) demonstrate synergistic protection against xenogeneic GVHD and tumor (Raji cells) in mice, compared to PTCy/TAC (median survival: 45 days v undefined, 9 mice/group, 2 experiments, P&amp;lt;0.0001). Unlike alisertib, VIC-1911 is not myelosuppressive, providing rationale for this trial. In vitro studies show killing of multiple leukemia cells lines at physiologically achievable VIC-1911 concentrations. VIC 75 mg BID is the lowest biologically active dose suppressing AURKA activity below the primary endpoint target of &amp;lt;54%, with reduced mean frequency of day +21 pH3ser10+ CD4+ T cells at 23.7% compared to 58.5% with PTCy/SIR/MMF (Figure 1A, P=0.0091). PTCy/SIR/VIC also suppresses mTOR activity in donor T cells (3.9% v 16.6% pS6+ CD4+ T cells, P=NS; pS6 frequency in healthy donor T cells is ~30-40%), concurrently ablating CD28 signal transduction. Data trends show greater Tregs at day +21 with PTCy/SIR/VIC, compared to PTCy/SIR/MMF controls (40.2% v 10.5%, P=NS). Patient characteristics are detailed in Figure 1B. Neutrophil engraftment occurred in 9/9 evaluable patients at a median of 18 days. Platelet engraftment occurred in 8/9 evaluable patients at a median of 21 days; one patient is awaiting platelet engraftment. No dose-limiting toxicities have been observed during dose escalation. Patient 1 died of non-COVID coronavirus during initial hospitalization; he received high-dose methylprednisolone for ARDS beginning on day +17, which made him unevaluable for the primary pharmacodynamic endpoint. Conclusions: A VIC-1911 dose of 75 mg BID from day +5 to day +45 effectively suppresses AURKA activity as determined by a low frequency of pH3ser10+ CD4+ T cells, ablating CD28 T cell costimulation when combined with sirolimus, resulting in no dose-limiting toxicities. VIC 75 mg BID will be studied further in an expanded phase I cohort to obtain estimates of efficacy in preventing both GVHD and relapse in PTCy-based myeloablative alloHCT.

Outcomes after Bone Marrow Versus Peripheral Blood Haploidentical Hematopoietic Stem Cell Transplantation Using Post-Transplant Cyclophosphamide-Based Gvhd Prophylaxis

Background: Patients who do not have a human leukocyte antigen (HLA)-matched donor can undergo hematopoietic stem cell transplantation (HSCT) by utilizing haploidentical (haplo) family donors and post-transplant cyclophosphamide (PTCy) for Graft-versus-host disease (GVHD) prophylaxis. Originally, Haplo transplants utilized a bone marrow (BM) source because of concern of higher incidence of GVHD with peripheral blood stem cells (PBSC) graft. Recent years have seen an increase in PBSC graft utilization. Some published studies have reported comparable survival between the two graft sources. These studies also reported lower rate of chronic GVHD and higher quality of life with BM and a lower relapse rate and faster engraftment with PBSCs. We aimed to investigate the outcomes following BM versus PBSC haplo HSCT using (PT-Cy)-based GVHD prophylaxis. Methods: In this single-center retrospective study, we included all (n=176) adult patients who underwent haplo HSCT from August 2016 to July 2021 and had at least one year of follow-up. Bivariate analyses, using the chi-square and t-test, were performed. Kaplan-Meier and regression analyses were conducted. Data were analyzed using SPSS version 28. Statistical significance was considered at p&amp;lt;0.05. Results: The study included 176 haplo transplants including 65% peripheral blood and 35% bone marrow grafts. The median age was 54 (18-74) years and 68% of recipients were males. Ethnic minorities comprised 30% of recipients. Hematologic diagnoses included myeloid disease (65%), lymphoid disease (29%), and others (6%). 31 % of the patients underwent a Myeloablative transplant. Hematopoietic cell transplantation comorbidity index of 3 or higher was noted in 53% of patients. With a Median follow-up 21 (0-73) months, Overall survival (OS) and disease-free survival (DFS) was not reached in either BM or PBSC haplo HSCT group. 1-year OS of 75% and 74% (p-0.898) and 1-year DFS of 63% and 63% (p-0.994) were noted in BM and PBSC group respectively. In PBSC versus BM haplo recipients, an earlier neutrophil engraftment (17 days vs 18 days, p=0.022) was seen. Similar incidences of grade II-IV acute GVHD (50% vs 51%, p=0.875), relapse (22% vs 26%, p=0.579), non-relapse mortality (NRM, 17% vs 20%, p=0.682), platelet engraftment (28 vs 31 days, p&amp;lt;0.092) and 1- year chronic GVHD (35% vs 38%, p=0.410) were noted. Conclusions: In this study, Haploidentical allogeneic hematopoietic stem cell transplant recipients demonstrated similar rates of overall and disease-free survival, relapse, non-relapse mortality, acute and chronic GVHD, and platelet engraftment regardless of graft source. Neutrophil engraftment was observed one day earlier in peripheral stem cell recipients. This supports the use of either PBSC or Bone marrow as the preferred source of Haploidentical transplants.

TMI-Based Dose-Escalated Bone Marrow Transplantation Can Help Preserve the Bone Marrow Microenvironment and Reduce Cellular Senescence in Old Mice

Introduction:Senescence is one of the hallmarks of aging and age-related conditions, including but not limited to, inflammaging, frailty, and various age-related diseases. It has been well-established that radiation and chemotherapy can accelerate senescence. While myeloablative conditioning-based allogeneic hematopoietic cell transplant (HCT) is a curative treatment for patients with leukemia. The dose of total body irradiation (TBI) conditioning has to be reduced in older patients to reduce potential high treatment-related mortality, which may still cause accelerated senescence in aged individuals, resulting in poor survival outcomes. We initiated the testing of a novel total marrow irradiation (TMI) based myeloablative conditioning in older patients to enhance the anti-leukemia effect and overall survival. We hypothesize that this new radiation preconditioning strategy may also reduce radiation-induced senescence in aged individuals compared to TBI to reduce treatment-associated side effects and improve the outcomes of allogeneic HCT. We tested this hypothesis in the present study and further investigated the mechanisms of the effects of TMI-based myeloablative and dose-escalated bone marrow transplantation (BMT) on old mice by examining the changes in expression of various senescence markers and senescence-associated secretory phenotype (SASP) in the bone marrow (BM) and selected organs. Method: The radiation treatment regimens were: TMI (12:4), TMI (16:4) and TBI (12:12), and TBI (16:16), were developed as described (Zuro et al., 2021); i.e. (12:4) means the radiation dose to the BM was 12 Gy and the dose to the organs was 4 Gy. The young (8 weeks old) and aged mice (90 weeks old) of host C57BL/6j (JAX000664, CD45.2) were irradiated in 2 fractions 24h apart, and 25 million whole BM cells from donor (JAX002014, CD45.1) were transplanted by i.v. at 24 h after irradiation. For the hematopoietic stem and progenitor cell (HSPC) population study, more mature hematopoietic progenitors (Lin − Sca-1 −c-Kit + or LK cells) and HSPCs (Lin − Sca-1 + c-Kit + or LSK cells) were examined in BM by flow analysis. Cultured bone marrow mesenchymal stem cells (MSCs) were analyzed for the gene expression of the senescence marker CDNK1a (or p21) and SASP factors MMP13 and CXCL12 by qPCR. For senescence study in organs such as the liver, gut, and spleen, senescence-associated beta-galactosidase (SA-β-gal) staining was performed and expression of the CDNK2a (or p16) was analyzed by qPCR. Results: TMI or TBI treatment with young donor BMT repopulated the BM HSPC population without significant bone damage in aged mice (data not shown). While the BM LK and LSK populations significantly reduced in aged mice after TMI or TBI with young donor BMT compared to aged control mice ( Fig 1A), these populations were not different from young mice groups ( Fig 1B). In addition, TMI or TBI treatment with young donor BMT reduced MSC senescence. Cultured MSCs analysis showed the reduction of p21, MMP13, and CXCL12 expression ( Fig 1C-E) after TMI or TBI with young donor BMT in aged compared to aged control without radiation and BMT. However, while TMI treatment and BMT reduced senescence in the organs, mice receiving TBI treatment and BMT showed a higher senescence burden. In the liver, the aged control mice showed a significant increase in SA-β-gal staining, which was decreased in TMI (12:4) and TMI (16:4) mice ( Fig 1F). In contrast, this effect was not observed in aged mice after TBI (12:12) or (16:16) ( Fig 1G). Moreover, the senescence marker p16 expression in the liver and gut was reduced only in TMI (12:4) and TMI (16:4), not in TBI (12:12) or (16:16) ( Fig 1H, I), whereas the p16 expression in the hematopoietic tissue, spleen was decreased in all treatment groups TMI vs. TBI ( Fig 1J). Conclusion: TMI-based dose escalates with young donor BMT in aged mice preserved BM microenvironment and reduced senescence of organs while TBI treatment causes senescence of the organs. Young donor BMT, which combined with TMI or TBI treatment, preserved bone structure and reduced senescence of HSPC and MSC. However, TMI treatment decreased the SA-β-gal staining and p16 expression significantly in organs such as the liver and gut, but not by TBI treatment. This study showed the senescence reduction in both bone marrow and organs after young donor BMT and TMI treatment. For further study, we have a plan to study the mechanism and signaling pathway of senescence reduction.

MSCs-IL33-ILC2s-AREG-Tecs Axis Promotes the Remodeling of Thymic Function in Acute Gvhd

Background: Previous studies suggested that mesenchymal stromal cells (MSCs) administrated at the acute graft versus host disease (aGVHD) phase effectively decreased the incidence and severity of chronic GVHD (cGVHD) by boosting thymic regeneration. Our research has found that MSCs expressing interleukin 33 (IL33) may participate in thymus regeneration from aGVHD damage through type 2 innate lymphoid cells (ILC2s)-mediated tissue recovery. However, the mechanism for ILC2s repairing the damaged thymus caused by aGVHD is unclear. Here, we further explored the mechanisms on how ILC2s promote thymus recovery post-BMT. Methods: We carried out studies in a aGVHD mice model of fully MHC-mismatched myeloablative bone marrow transplantation (C57BL/6 to BALB/c). IL33 knocked-down (MSC/IL33 -) and empty-load MSCs (MSC/Control) were generated by lentivirus transfection, and then administrated intravenously at day 7 post-BMT to intervene in aGVHD and assess the effect of IL33 from MSCs on ILC2s (Lin-CD45+iCD3-CD127+GATA3+) in the thymus by flow cytometery at day 14 post-BMT. Clinical scores and survival were recorded once every days. Furthermore, we isolated, purified and amplified ILC2s from C57BL/6 mouse thymus by immunomagnetic bead sorting and flow cytometry for aGVHD intervention and studied whether ILC2s can home to thymus by fluorescence tracing and the effects of ILC2s on TECs by immunofluorescence. To study the potential mechanism of ILC2s affecting TECs by using transcriptome sequencing (RNA-seq) and related molecular biology experiments. Finally, the potential target amphiregulin (AREG) was found from RNA-seq analyses and the murine recombinant AREG was used as an intervention to evaluate its effect on aGVHD mouse. Results: In this study, we found that knocking down the expression of IL33 in MSCs partially blocked the repair effect of MSCs on thymus and decreased the expansion of thymic ILC2s in aGVHD mice compared with the MSC/Control group. Then, we found that exogenous infusion of thymic ILC2s is very effective in treating thymic tissue injury, and can home to the recipient thymus and further migrate to the thymic medulla region. Furthermore, we found that ILC2s may home to the thymus and migrate to the thymic medulla region through CCR7 and MSCs promote the high expression of AREG in ILC2s through RNA-seq. Importantly, we found that the expression level of intrathymic AREG in No-GVHD, MSCs-GVHD and ILC2s-GVHD group was significantly increased than aGVHD group on day 14 post-BMT and exogenous administration of AREG after transplantation can significantly increase the proliferation of thymic epithelial cells, especially the regeneration of thymic medulla and the generation of new thymus-derived CD4/CD8 double-positive T cells. Conclusion: In conclusion, we demonstrate that MSCs infusion may rely on the MSCs-IL33-ILC2s-AREG-TECs axis mediated by ILC2s to remodeling the thymic microenvironment homeostasis, thus promoting the reconstruction of T cell immune homeostasis. Importantly, the results presented in this report identify a previously unrecognized role for the epidermal growth factor family member AREG in promoting the remodeling of thymus tissue. and providing new insights for the mechanism of MSCs treatment for GVHD.

Outcomes after Bone Marrow Versus Peripheral Blood Stem Cell Matched Unrelated Donor Hematopoietic Stem Cell Transplantation

Background: Matched unrelated donors (MUD) have become an acceptable alternative donor for patients requiring potentially curative hematopoietic stem cell transplantation (HSCT) and lacking a matched sibling donor. Patients may undergo a bone marrow (BM) or peripheral blood stem cell (PBSC) graft, with previous studies showing similar survival outcomes. However, BM grafts have shown a lower incidence of chronic graft-versus-host disease (GVHD) but a higher relapse rate and slower engraftment. We aimed to compare the outcomes of BM versus PBSC in patients undergoing MUD HSCT. Methods: For this retrospective single-center study, we included all (n=276) adult MUD HSCT recipients at the University of Kansas Medical Center who had at least one year of follow-up (August 2016 to July 2021). We conducted a bivariate analysis using chi-squared and ANOVA tests. The Kaplan-Meier and regression analyses were also performed. Data analyses were conducted using SPSS version 28. Statistical significance was considered at p&amp;lt;0.05. Results: Our study included 276 MUD patients including 110 PBSC (40%) and 166 BM (60%) grafts. The median age was 55 (range 21-77) years, and 158 patients (57%) were males. Eighteen patients (6%) were ethnic minorities, and 89 (32%) patients had a Karnofsky performance status of ≥90%. 118 (43%) patients had a hematopoietic cell transplantation-specific comorbidity index of 3 or higher. Hematologic diseases included acute myeloid leukemia (n=119, 43%), myeloid disorders (n=77, 28%), acute lymphoblastic leukemia (ALL) (n=35, 13%), Lymphoma (n=15, 5%), and others (n=30, 11%). Sixty-two percent of patients were in complete remission at the time of transplantation, and patients not in remission included myelodysplastic syndrome, myelofibrosis, and lymphoma patients. Reduced-intensity conditioning (RIC, n=162, 58%) and myeloablative conditioning (MAC) (n=114, 41%) were used. The median follow-up was 55 (21-73) months. Overall survival (OS) was not reached in either BM or PBSC MUD HSCT group, while a median disease-free survival of 45 and 49 months was noted in PBSC and BM groups respectively (p=0.915). We observed similar rates of relapse (25% vs 27%, p=0.413), one-year overall survival (75% vs 72%, p=0.679), one-year disease-free survival (63% vs 62%, p=1.00), and one-year non-relapsed morality (NRM, 23% vs 21%, p=0.779) after PBSC or BM graft. Bone marrow graft recipients had delayed engraftment of neutrophils (20 days vs 16 days, p&amp;lt;0.001) and platelets (&amp;gt;20 K/uL: 24 days vs 16 days, p&amp;lt;0.001; &amp;gt;50 K/uL: 28 days vs 18 days, p=0.006) compared to PBSC recipients. Bone marrow graft recipients had similar rates of grade II-IV acute GVHD (50% vs 52%, p=0.714) and grade III-IV GVHD (12% vs 11%, p=0.847), but lower rates of 1-year chronic GVHD (39 % vs 55%, p=0.014) compared to PBSC recipients. In the subgroup analysis stratified by conditioning intensity, faster engraftment of neutrophils (median 16 vs 21 days, p&amp;lt;0.001) and platelets (&amp;gt;20 K/uL: 18 days vs 27 days, p&amp;lt;0.001; &amp;gt;50 K/uL: 18 days vs 33 days, p&amp;lt;0.001) was observed with PBSC as compared to BM graft in myeloablative transplant recipients, while there was no statistically significant association with the rates of acute or chronic GVHD, NRM, Relapse, DFS, and OS after a PBSC or BM graft. Among the RIC transplant recipients, faster neutrophil engraftment (mean 17 vs 20 days, p&amp;lt;0.001) and higher 1-year extensive chronic GVHD (52% vs 32%, p=0.015) were observed with PBSC compared to BM graft whereas no statistically significant difference was noted in platelet engraftment, acute GVHD, NRM, Relapse, DFS, and OS after a BM or PBSC graft. Conclusions: Allogeneic matched unrelated donor hematopoietic stem cell transplant recipients had similar rates of overall and disease-free survival, relapse, non-relapse mortality, and acute GVHD after a bone marrow or peripheral blood stem cell graft; however, delayed neutrophil and platelet engraftment with a lower incidence of chronic GVHD was noted after a bone marrow graft compared to peripheral blood stem cell graft.

One versus two sets of busulfan therapeutic drug monitoring in myeloablative allogeneic hematopoietic cell transplant.

Busulfan is a common component of allogeneic hematopoietic cell transplant (alloHCT) conditioning, however interpatient pharmacokinetic variability can result in enhanced toxicity or increased relapse risk. Therapeutic drug monitoring (TDM) can minimize variability, yet the optimal frequency of TDM is unknown. We compared outcomes for patients with one versus two sets of busulfan TDM during myeloablative conditioning (MAC) prior to alloHCT. We analyzed the impact of busulfan TDM frequency and dose adjustments, with the primary outcome being relapse-free survival (RFS). Other outcomes included the incidence of acute and chronic graft versus host disease (GVHD), oral mucositis, pulmonary toxicity, sinusoidal obstruction syndrome (SOS), the cumulative incidence of relapse (CIR), and overall survival (OS). Twenty-two patients underwent one set of sampling while 53 patients underwent two sets. Similar baseline characteristics were observed between the groups. There were no significant differences observed in RFS by day +180 (77.3% vs. 79.2%, p = 1.0), CIR by day +180 (18.2% vs. 17.8%, p = 0.74), or OS (p = 0.73). The incidences of acute GVHD, chronic GVHD, SOS, and severe mucositis were also similar. In each group, 63% received busulfan dose adjustments after one set, with 52.8% receiving further dose adjustments following the second set. We observed no significant difference in alloHCT outcomes between patients who underwent one versus two sets of busulfan TDM sampling, suggesting that a single-time TDM and dose adjustment may be adequate to maximize outcomes after MAC alloHCT.

COVID-19 omicron variant outbreak in a hematopoietic stem cell transplant unit.

Recommendations and guidelines for management of SARS-COV-2 infection in hematologic patients were developed in the very difficult context of dealing with novel viral variants from one pandemic wave to another, with different susceptibility to available drugs and vaccines. Moreover, the largest SARS-COV-2 case series in patients treated for hematologic malignancies, including stem cell transplant recipients, was published before the Omicron surge, and refers mainly to Alpha and Delta viral variants. These infections had very high mortality, in a period when antivirals and monoclonal antibodies were mostly unavailable. Here, we report for the first time a SARS-COV-2 Omicron variant outbreak inside a Bone Marrow Transplant (BMT) Unit, describing the characteristics, clinical course, and infection outcomes shortly before and shortly after myeloablative transplantation. We detail how infections were treated off-label and managed inside the BMT ward, to guarantee the best possible outcomes while avoiding risks for non-infected inpatients. The positive outcomes observed suggest that it may not be absolutely necessary to obtain SARS-CoV-2 PCR negativity before BMT in hematologic patients after treated infection, in cases with long-term PCR positivity and high-risk hematologic disease.

Outcomes of hematological malignancy patients who underwent myeloablative haploidentical transplant with PTCy and ATG.

e19057 Background: Haplo-HCT is a potentially curative intervention for hematological malignancies. A number of transplant platforms are used by different groups. We adopted a myeloablative conditioning (MAC) protocol, BM graft with post-transplant cyclophosphamide (PTCy) for GvHD prophylaxis as our program cares for young patients with hematologic malignancies. High grades GvHD were noticed, antithymocyte globulin (ATG) 2mg/kg was added to the platform. During COVID19 outbreak PBSCT was used as a graft source. Methods: Retrospective review of patients who underwent myeloablative Haplo-HCT for malignant hematologic disorders using ATG and PTCy for GvHD prophylaxis. Patient characteristics were summarized using frequencies for categorical variables and medians with ranges for continuous variables. Probabilities of overall survival (OS), relapsed-free survival (RFS) were summarized using Kaplan-Meier estimator with variance estimated using Greenwood’s formula. Survival curves were compared using the log-rank test. Probabilities of aGvHD, cGvHD, and extensive cGvHD were calculated using cumulative incidence function (CIF) taking into consideration DLI and death without GvHD. Probabilities of and relapse and non-relapsed mortality (NRM) were calculated using CIF taking into consideration death without GvHD and NRM and relapse as competing risks, respectively. Results: 60 patients were reviewed, 32 (53%) were males and 28 (47%) females. 57% had AML and 23% had ALL. Other diagnoses included CML, MDS, APL and BPDCN. 73% received BM graft and 27% PBSCT graft. The conditioning was myeloablative in the form of Thio/Bu/Flu (68%) for myeloid malignancies and Flu/TBI 1000 cGy (27%) for lymphoid malignancies. Most donors were males (57%) siblings (60%), with more than 50% HLA matching (58%), and no ABO mismatch (70%). Disease risk index (DRI) was intermediate in most cases (38%) followed by high (32%). At 5 years, the OS was 59% (95% CI: 46%-73%), RFS was 49% (95% CI: 34%-63%). 42% patients developed grade 2-4 aGvHD and 15% of patients developed extensive cGvHD. OS of patients &gt; 50 years old was 21% (95% CI: 0%-56%). There were no cases of primary GF but 1 patient developed secondary GF. 17 patients developed HCYST (28%) and 17 (28%) needed ICU admission. Most patients (88%) developed CMV reactivation, and 2 patients developed VOD. We analyzed DRI, donor age, TBI vs. non-TBI, BM vs. PBSCT, donor relation, level of HLA matching, ABO mismatch, female vs. male donor, effects on OS, RFS and GvHD. None of these variables had significant association with OS. Higher DRI was associated with higher relapse (P0.04). Donor recipient sex mismatch and donor age were associated with cGvHD. Conclusions: Myeloablative Haplo-HCT for hematological malignancies with PTCy and ATG is safe and associated with acceptable OS, RFS and low rate of extensive cGvHD. Older patients require adjustment due to risk of higher NRM.

Absolute lymphocyte counts (ALC) recovery and risk of viral reactivation in the setting of haploidentical hematopoietic stem cell transplant.

e19065 Background: The impact of early absolute lymphocyte repopulation after allogeneic hematopoietic stem cell transplant has historically been shown to predict the risk of post-transplant infection, and subsequently, non-relapse mortality (NRM). Previous studies have shown that ALC recovery after allogeneic stem cell transplant is associated with risk of viral reactivation and survival. In this study we aim to investigate the role of ALC recovery in the contemporary era with myeloablative haploidentical hematopoietic stem cell transplant (HI-HSCT). Methods: We retrospectively analyzed adult patients at University of Southern California (USC) Norris Cancer Hospital who received myeloablative conditioning haplo-HSCT (Fludarabine with 12 Gy of radiation) from 2014 to 2020. The primary endpoint was correlation between ALC recovery day 21 and risk of viral reactivation including cytomegalovirus (CMV), Epstein-Barr Virus (EBV) and BK virus. ALC recovery cut off was chosen to be 175/uL on day +21 and 500/uL on day +60 based on prior reports. Results: 58 patients were identified as recipients of MAC haploidentical-HSCT. 17 had ALC recovery at day +21. Mean age was 49 years, 31 (53.4%) were males and 27 (46.6%) were females. 41 (70%) patients were Hispanic, 12 (20%) were non-Hispanic White, and the majority had AML (51%). 76% received &gt; 5*106/kg CD34+ cell dose and 78% received CD3 + cell dose &lt; 3*108/kg. Serum CMV, EBV and urine BK virus were detected in 38 (65.5%), 8 (15.7%) and 11 (32.4%) respectively. Clinically significant CMV reactivation (required treatment with antiviral therapy) was detected in 26 (44.8%) patients. Lack of ALC recovery on day +21 did not show correlation with CMV, EBV and BK virus reactivation. Also, the risk of CMV reactivation was not related to day +60 ALC recovery (p-value = 0.469). On univariate analysis, ALC recovery day +21, day +60, and CMV reactivation did not show correlation with overall survival. In multivariate analysis when adjusted for age and pre-transplant CMV status, higher CD 3+ cell dose of &gt; 3*108/kg was associated with reduced risk of CMV reactivation HR = 0.35 (0.15-0.85) p-value = 0.02. Conclusions: Previous studies have established ALC recovery as a predictor of better outcome. This has not been established in patients undertaking myeloablative HI-HSCT. Our study shows that lack of ALC recovery on day +21 does not affect CMV, EBV and BK virus reactivation and risk of CMV reactivation does not correlate with day +60 ALC recovery. Also, ALC recovery and CMV reactivation does not impact overall survival. The use of Letermovir, effective CMV therapies and close viral surveillance in contemporary practice is likely responsible for mitigating poor outcomes with CMV reactivation. Graft composition needs to be studied prospectively, as higher CD3+ cell dose may present an opportunity to reduce CMV reactivation in HI-HSCT.

Treatment With the Combination of Rituximab and Intravenous γ Globulin Is Effective in Promoting Engraftment in Donor-Specific Antibody Positive Patients Receiving Myeloablative Conditioning Haploidentical Stem Cell Transplantation

Donor-specific anti-HLA antibodies (DSAs) are a major cause of engraftment failure in patients receiving haploidentical stem cell transplantation (HaploSCT). Effective procedures are needed for those who demand urgent transplantation and have no other donor options. We here retrospectively analyzed 13 patients with DSAs successfully treated with desensitization of rituximab and intravenous γ globulin (IVIg) before HaploSCT from March 2017 to July 2022. All 13 patients had DSA mean fluorescence intensity >4000 of at least 1 loci before desensitization. Of the 13 patients, 10 patients were with the initial diagnosis of malignant hematological diseases, and 3 were diagnosed with aplastic anemia. Patients were treated with 1 (n = 3) or 2 (n = 10) doses of rituximab (375 mg/m2 for 1 dose). All patients receive the same total dose of 0.4 g/kg of IVIg within 72 hours before haploidentical stem cell administration to neutralize the remaining DSA. All patients achieved neutrophil engraftment, and 12 patients achieved primary platelet engraftment. The patient with primary platelet engraftment failure received purified CD34-positive stem cell infusion nearly 1 year after transplantation and achieved platelet engraftment thereafter. The estimated 3-year overall survival is 73.4%. Although further studies on larger numbers of patients are needed, it is clear that the combination of IVIg and rituximab is an effective way to clear DSA and has a strong effect on promoting engraftment and survival for patients with DSA. It is a practical and adaptable combination of treatment options.