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Combining Mobilizing Agents with Busulfan to Reduce Chemotherapy-Based Conditioning for Hematopoietic Stem Cell Transplantation.

ABSTRACT: In the context of hematopoietic stem cell (HSC) transplantation, conditioning with myelo- and immune-ablative agents is used to eradicate the patient's diseased cells, generate space in the marrow and suppress immune reactions prior to the infusion of donor HSCs. While conditioning is required for effective and long-lasting HSC engraftment, currently used regimens are also associated with short and long-term side effects on extramedullary tissues and even mortality. Particularly in patients with severe combined immunodeficiency (SCID), who are generally less than 1-year old at the time of transplantation and often suffer from existing comorbidities. There is a pressing need for development of alternative, less toxic conditioning regimens. Hence, we here aimed to improve efficacy of currently used myeloablative protocols by combining busulfan with stem-cell niche-directed therapeutic agents (G-CSF or plerixafor) that are approved for clinical use in stem cell mobilization. T, B and myeloid cell recovery was analyzed in humanized NSG mice after different conditioning regimens. Increasing levels of human leukocyte chimerism were observed in a busulfan dose-dependent manner, showing comparable immune recovery as with total body irradiation in CD34-transplanted NSG mice. Notably, a better T cell reconstitution compared to TBI was observed after busulfan conditioning not only in NSG mice but also in SCID mouse models. Direct effects of reducing the stem cell compartment in the bone marrow were observed after G-CSF and plerixafor administration, as well as in combination with low doses of busulfan. Unfortunately, these direct effects on the stem population in the bone marrow were not reflected in increased human chimerism or immune recovery after CD34 transplantation in NSG mice. These results indicate moderate potential of reduced conditioning regimens for clinical use relevant for all allogeneic transplants.

SUBMITTER: Garcia-Perez L

PROVIDER: S-EPMC8147230 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundAllogeneic stem cell transplantation (allo-HSCT) is the ultimate cure for acute lymphoblastic leukemia (ALL).AimThis study was performed to compare the outcomes of ALL patients receiving busulfan (Bu) with cyclophosphamide (Cy)-based or total body irradiation (TBI)-based regimen in a Chinese population.MethodsWe enrolled 224 adult patients with ALL who received allo-HSCT at National Taiwan University Hospital between 1997 and 2016.ResultsThe median age at transplantation was 33 years. Before allo-HSCT, 75.9% of patients attained first or late complete remission. A total of 141 patients (62.9%) received Bu/Cy-based conditioning, either myeloablative (MA) or reduced-intensity stem cell transplantation (RIST), and 83 patients received a TBI-based regimen (MA-TBI). Patients receiving the MA-Bu regimen had longer relapse-free survival (RFS) than those receiving the MA-TBI regimen (median, 24.1 vs. 6.7 months, p = .044). There was no difference in overall survival (OS, MA-Bu vs. MA-TBI vs. RIST-Bu: 39.4 vs. 28.2 vs. 13.1 months, p = .276), treatment-related mortality (TRM), or incidences of grade 3-4 acute graft-versus-host disease (GvHD). Among patients receiving identical GvHD prophylactic regimens, there was no difference between MA-Bu and MA-TBI groups regarding the incidence of grade 3-4 acute GvHD, grade 2-4, and all-grade chronic GvHD. In subgroup analysis, patients receiving oral busulfan had comparable RFS and OS to the intravenous busulfan group (p = .436 and p = .236, respectively), but a higher TRM (25% vs. 9.8%, p = .016). In the multivariable analysis, disease status before allo-HSCT was the only risk factor impacting RFS and OS.ConclusionIn summary, patients receiving Bu/Cy-based or TBI-based regimens as conditioning had similar results in terms of OS, TRM, and acute GvHD, whereas the use of myeloablative Bu/Cy resulted in a better RFS. A Bu-based regimen could be an alternative conditioning choice for patients who are ineligible to receive TBI. Prospective and randomized controlled trials are warranted to validate the long-term outcomes.

Project description:Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative therapeutic option for many patients with hematological malignancies and nonmalignant hematopoietic disorders. To achieve stable engraftment of donor hematopoietic stem cells (HSCs), recipient HSC deletion is needed to create space for incoming donor HSCs and donor HSCs must escape immune rejection by the recipient. Conventional allo-HSCT requires high dose of irradiation and/or chemotherapy to produce sufficient host stem cell and immune system ablation to permit donor HSC engraftment. However, these procedures also result in nonspecific tissue injury that can cause short- and long-term adverse effects as well as incite and amplify graft-versus-host-disease (GVHD). The delivery of targeted radiotherapy to hematopoietic tissues with the use of a radioimmunoconjugate (ROIC) as a part of transplant preparative regimen has shown clinical benefits. ROIC clinical data provide evidence for decreased relapse without increased transplant-related mortality by delivering higher targeted radiation to sites of malignancy than when given in a nontargeted fashion. An alternative approach to allo-HSCT has been developed and tested in preclinical mouse models in which nonmyeloablative preconditioning with low dose of the alkylating agent (busulfan) or lower systemic dose of irradiation combined with co-stimulatory pathway blockade (CTLA4-Ig, anti-CD40L monoclonal antibody) and/or immunosuppressive drugs have been used. Under these conditions, mixed chimerism and transplantation tolerance to fully MHC mismatched donor marrow was observed. Recently, several novel proof-of-concept antibody-mediated preconditioning methods have been developed that can selectively target hematopoietic stem and immune cells with minimal overall toxicity. Antibody-drug-conjugate (ADC) combined with reduced intensity conditioning or high dose ADC as single dose monotherapy have shown promise for allo-HSCT in preclinical models. The purpose of the current review is to discuss the literature exploring antibody-based conditioning that includes native antibody, radiolabeled antibody conjugates, and ADC for allo-HSCT.

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Combining Mobilizing Agents with Busulfan to Reduce Chemotherapy-Based Conditioning for Hematopoietic Stem Cell Transplantation.

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