Antithymocyte globulin in reduced-intensity conditioning regimen allows a high disease-free survival exempt of long-term chronic graft-versus-host disease

Allogeneic hematopoietic cell transplantation for patients with AML aged 70 years or older in first remission. A study from the Acute Leukemia Working Party of the European Society for Blood and Marrow Transplantation (EBMT)

Accessibility to allogeneic hematopoietic cell transplantation (HCT) programs for older patients is growing constantly. We report on the clinical outcomes of a group of 701 adults aged ≥70 years, with acute myeloid leukemia (AML) in first complete remission (CR1), who received a first HCT, from HLA-matched sibling donors (MSD), 10/10 HLA-matched unrelated donors (UD), 9/10 HLA-mismatched unrelated donors (mUD) or haploidentical (Haplo) donors. The 2-year overall survival (OS) was 48.1%, leukemia-free survival (LFS) 45.3%, relapse incidence (RI) 25.2%, non-relapse mortality (NRM) 29.5% and GVHD-free, relapse-free survival (GRFS), 33.4%. Compared to MSD, patients transplanted from Haplo and UD presented lower RI (HR 0.46, 95% CI 0.25-0.8, p = 0.02 and HR 0.44, 95% CI: 0.28-0.69, p = 0.001, respectively); this translated into prolonged LFS for Haplo (HR 0.62, 95% CI: 0.39-0.99, p = 0.04). Patients transplanted from mUD exhibited the highest NRM incidence (HR 2.33, 95% CI: 1.26-4.31, p = 0.007). HCT in selected adult CR1 AML patients >70 years is feasible and could be associated with good clinical outcomes. Prospective clinical trials are warranted.

Comparison of Benefits and Risks Associated with Anti-T-Lymphocyte Globulin (ATLG) Serotherapy in Methotrexate (MTX)- versus Mycophenolate Mofetil (MMF)-Based Hematopoietic Stem Cell Transplantation

Background: Serotherapy with anti-T lymphocyte globulin (ATLG, Grafalon, formerly ATG-Fresenius) is established for the prevention of severe graft-versus-host disease (GVHD) after hematopoietic stem cell transplantation (HSCT). The evidence from prospective studies is predominantly derived from a setting where methotrexate (MTX) and a calcineurin inhibitor (CNI) are used as the backbone of GVHD prophylaxis. The efficacy of ATLG in combination with CNI and mycophenolate mofetil (MMF) has not been investigated as much, particularly in terms of a direct comparison with its effects when combined with CNI/MTX. A total of 401 HSCTs from two Austrian transplant centers were retrospectively evaluated. We included peripheral blood transplants from early- or intermediate-stage (excluding advanced/refractory) hematological diseases from matched siblings or 10/10 or 9/10 matched unrelated donors with CNI/MTX or CNI/MMF prophylaxis, either without (n = 219) or with ATLG (n = 182). Overall, ATLG significantly reduced the risk for all-cause mortality by multivariate Cox analysis (HR 0.53; p = 0.002). Stratification by postgrafting prophylaxis type revealed a significant survival advantage for ATLG in the CNI/MMF cohort (HR 0.49; p = 0.001; n = 193), while its effect on survival in the CNI/MTX cohort was not significant (HR 0.87; p = 0.56; n = 208). In unrelated HSCT with CNI/MMF prophylaxis, ATLG exhibited its greatest survival benefit (HR 0.34; p = 0.001; n = 104). In the context of CNI/MMF, ATLG may provide even greater benefits than in the setting of CNI/MTX for post-grafting immunosuppression. Future prospective studies on ATLG should therefore focus on CNI/MMF-based transplants, which are widely performed in elderly or comorbid patients not expected to tolerate a standard course of MTX.

Itacitinib Population Pharmacokinetics and Exposure-Response in Patients With Acute Graft-Versus-Host Disease

This article presents the population pharmacokinetic (PopPK) analysis and exposure-response analyses for the primary efficacy end point-acute graft-versus-host disease (aGVHD) day 28 response-and select safety measures (incidence of thrombocytopenia, hypertriglyceridemia, and cytomegalovirus infection) from a phase 3 randomized, double-blind study comparing itacitinib plus corticosteroids versus placebo plus corticosteroids for the treatment of aGVHD. The PopPK data set contained sparse data from patients with aGVHD and select enriched data from healthy volunteers. The structural model was a 2-compartment model with first-order elimination and dose-dependent nonlinear absorption with dual first-order absorption pathways with lag times. Strong cytochrome P450 (CYP) 3A inhibitor coadministration, moderate renal impairment, and participant population (healthy volunteers vs patients with aGVHD) were covariates on apparent clearance. Participant population was also a covariate on apparent intercompartmental clearance and lag time of the secondary absorption compartment. Apparent clearance decreased 42% with coadministration of strong CYP3A inhibitors. Simulations supported the following dose reductions with concomitant use of a strong CYP3A inhibitor: 300 mg once daily to 200 mg once daily, 400 mg once daily to 300 mg once daily, and 600 mg once daily to 400 mg once daily. No dose adjustment is recommended for any other covariate based on the magnitude of impact when they were retained in the model. The exposure-response relationship was characterized between itacitinib exposure and probability of aGVHD day 28 response using a linear logistic regression model. Both itacitinib exposure and aGVHD risk status were significant predictors of response. There was no relationship between itacitinib exposure and thrombocytopenia, hypertriglyceridemia, or cytomegalovirus infection.

The impact of different doses of antithymocyte globulin conditioning on immune reconstitution upon hematopoietic stem cell transplantation

INTRODUCTION

Anti-thymocyte globulin (ATG) is used prior to allogeneic hematopoietic stem cell transplantation (allo-HSCT) for graft-versus-host disease (GVHD) prophylaxis. Two different ATG doses (7.5 or 10 mg/kg) were evaluated in comparison with a group without ATG therapy.

METHODS

We retrospectively analyzed 132 patients who were transplanted with HSCT without ATG (non-ATG), or who received 7.5 mg/kg ATG (ATG-7.5) or 10 mg/kg ATG (ATG-10) prior to transplantation. The immune cells (CD3⁺CD4⁺ T cells, CD3⁺CD8⁺ T cells, CD19⁺ B cells and CD16⁺CD56⁺ NK cells) were examined in peripheral blood every three months post-HSCT for 12 months.

RESULTS

Compared with non-ATG group, combined ATG-7.5/ATG-10 groups had significantly lower CD3⁺CD4⁺ T cells and higher CD3⁺CD8⁺ T cells at 3, 6, 9, 12 months post-HSCT; thus, displaying a lower CD4/CD8 ratio in the ATG groups compared to non-ATG group. The ratio of CD19⁺ B cells was statistically lower (at 3rd month, p = .014; at 6th month, p = .025) in combined ATG-7.5/ATG-10 groups at 3 and 6 months post-HSCT, but not at 9 and 12 months after HSCT. The ratios of CD3⁺CD4⁺ T cells, CD3⁺CD8⁺ T cells, CD19⁺ B cells and CD16⁺CD56⁺ NK cells were similar between the ATG-7.5 and ATG-10 groups at all examined time points. The overall survival (OS), progression-free survival (PFS), relapse and acute GVHD (aGVHD) were comparable among recipients without ATG therapy and with ATG-7.5 or/and ATG-10 therapies. Multivariate analysis revealed that immune cells ratios were not independent factors affecting prognosis.

CONCLUSION

The ATG therapy at higher and lower doses led to a delayed reconstitution of T cells and the inversion of CD4/CD8 ratio for at least one year after HSCT.

Post-transplant Cyclophosphamide Versus Thymoglobulin in HLA-Mismatched Unrelated Donor Transplant for Acute Myelogenous Leukemia and Myelodysplastic Syndrome

Limited information is available on the efficacy of post-transplantation cyclophosphamide (PTcy) or thymoglobulin for graft-versus-host disease (GVHD) prophylaxis in mismatched unrelated donor (MMUD) transplants. We retrospectively compared outcomes of 76 adult patients with acute myelogenous leukemia (AML) or myelodysplastic syndrome (MDS) who underwent 7/8 HLA-MMUD transplantation and received either PTcy (50 mg/kg on day 3 and 4) or thymoglobulin (total dose 4.5 mg/kg) for GVHD prophylaxis. In addition, tacrolimus and mycophenolate were used in both groups. Propensity score-based multivariable analyses (PSCA) were performed to adjust confounding effects of patient characteristics between both groups. Between January 2006 and June 2019, 25 patients received PTcy, and 51 received thymoglobulin. Median age of the population was 57 years, 78% of patients had AML, most common graft source was peripheral blood (96%), and 46% received myeloablative conditioning regimens. Median time to neutrophil (15 versus 11 days, P < .001) and platelet engraftment (21 versus 15 days, P = .002) was prolonged in the PTcy group. The cumulative incidence of grade III-IV acute GVHD at day 100 was similar (12% versus 19.6%, P = .38), whereas chronic GVHD at 1 year was lower with PTcy compared to thymoglobulin (16% versus 49%, P = .006). Using PSCA, no difference in survival, relapse, relapse-free survival, and GVHD-free relapse-free survival was seen between groups. However, thymoglobulin was associated with higher incidence of acute (hazard ratio [HR] = 2.63, P = .01) and chronic GVHD (HR = 4.43, P = .03), and non-relapse mortality (HR 3.38, P = .04) compared to PTcy. Our study demonstrated that PTcy resulted in significantly lower rates of acute and chronic GVHD and non-relapse mortality compared to thymoglobulin in 7/8 HLA-MMUD transplants for AML and MDS.

Phase I Trial of Prophylactic Donor-Derived IL-2-Activated NK Cell Infusion after Allogeneic Hematopoietic Stem Cell Transplantation from a Matched Sibling Donor

Simple Summary

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative option for high-risk hematologic malignancies. However, disease recurrence after allo-HSCT remains a critical issue, underlining the need to develop maintenance therapy. In this context, NK cell-based immunotherapies could enhance graft-versus-tumor effect without triggering graft-versus-host disease. In this prospective phase I clinical trial, we demonstrated the safety of donor-derived NK cell infusion as a prophylactic treatment after allo-HSCT for patients with hematological malignancies. This opens perspectives for future developments of NK cell based therapeutic strategies after allo-HSCT with low incidence of GVHD, representing an advantage over post-transplant T cell modulations that are commonly used in clinical routine.

Abstract

Background: NK cell-based immunotherapy to prevent relapse after allogeneic transplantation is an appealing strategy because NK cells can provide strong antitumor effect without inducing graft-versus-host disease (GVHD). Thus, we designed a phase-I clinical trial evaluating the safety of a prophylactic donor-derived ex vivo IL-2 activated NK cell (IL-2 NK) infusion after allo-HSCT for patients with hematologic malignancies. Methods: Donor NK cells were purified and cultured ex vivo with IL-2 before infusion, at three dose levels. To identify the maximum tolerated dose was the main objective. In addition, we performed phenotypical and functional characterization of the NK cell therapy product, and longitudinal immune monitoring of NK cell phenotype in patients. Results: Compared to unstimulated NK cells, IL-2 NK cells expressed higher levels of activating receptors and exhibited increased degranulation and cytokine production in vitro. We treated 16 patients without observing any dose-limiting toxicity. At the last follow up, 11 out of 16 treated patients were alive in complete remission of hematologic malignancies without GVHD features and immunosuppressive treatment. Conclusions: Prophylactic donor-derived IL-2 NK cells after allo-HSCT is safe with low incidence of GVHD. Promising survivals and IL-2 NK cell activated phenotype may support a potential clinical efficacy of this strategy.

Comparison of myeloablative and reduced intensity conditioning unrelated donor allogeneic peripheral blood stem cell transplant outcomes for AML using thymoglobulin for GVHD prophylaxis

A head-to-head comparison of outcomes of unrelated donor allogeneic peripheral blood stem cell transplantation for AML between reduced intensity conditioning (RIC) and myeloablative conditioning (MAC) regimens using thymoglobulin for GVHD prophylaxis is limited. We evaluated outcomes of 122 AML patients who received either busulfan (Bu)/fludarabine (Flu)/low-dose total body irradiation (TBI) as RIC (n = 64, 52%) or Bu/Flu as MAC (n = 58, 48%), and thymoglobulin 4.5 mg/kg total dose between day - 3 to - 1 for GVHD prophylaxis. Grades III-IV acute GVHD (aGVHD) was lower with Bu/Flu/TBI compared with Bu/Flu (6.2% vs 26.1%, p = 0.009). At 1 year, Bu/Flu/TBI was associated with similar chronic GVHD (41.2% vs 44.8%, p = 0.75), OS (61.9% vs 56.9%, p = 0.69), relapse rate (29.9% vs 20.7%, p = 0.24), relapse-free survival (52.8% vs 50%, p = 0.80), non-relapse mortality (17.4% vs 29.3%, p = 0.41), and GVHD-free relapse-free survival (24.2% vs 27.5%, p = 0.80) compared with Bu/Flu. Multivariable analysis did not reveal any difference in outcomes between both regimens. In summary, thymoglobulin at 4.5 mg/kg did not have any adverse impact on survival when used with RIC regimen. Both Bu/Flu/TBI and Bu/Flu conditioning regimens yielded similar survival.

Effect of Hepatic Impairment on the Pharmacokinetics of Itacitinib

Itacitinib is a potent, selective JAK-1 inhibitor currently in development for the treatment of chronic graft-vs-host-disease in combination with corticosteroids. Itacitinib is primarily eliminated via cytochrome P450 3A metabolism with minimal renal elimination. The purpose of this open-label study was to investigate the effect of hepatic impairment, as determined by Child-Pugh grade, on itacitinib pharmacokinetics. All participants received a single 300-mg dose of itacitinib orally in the fasted state. Blood samples were collected serially through 96 hours after dosing; 4 hours after dosing, an additional sample was collected for protein binding determination. Participants with moderate hepatic impairment (N = 8) had an approximate 2.5-fold increase in total exposure (area under the plasma concentration-time curve from time 0 to infinity [AUC_0-∞ ]) and an approximate 2-fold increase in maximal exposure (C_max ) compared to those with normal hepatic function (N = 8) (geometric mean ratio, 2.51 [90% confidence interval (CI), 1.54-4.08] for AUC_0-∞ and 1.95 [90%CI, 1.14-3.35] for C_max ). Participants with severe hepatic impairment (N = 6) had an approximate 4-fold increase in total exposure (AUC_0-∞ ) and an approximate 3.5-fold increase in maximal exposure compared to participants with normal hepatic function (geometric mean ratio, 4.08 [90%CI, 2.41-6.89] for AUC_0-∞ and 3.48 [90%CI, 1.94-6.23] for C_max ). Protein binding was similar between participants with moderate or severe hepatic impairment and participants with normal hepatic function, with average unbound fractions (percent free) of 25.7%, 31.5%, and 25.6%, respectively. There were no serious or fatal treatment-related adverse events. The results of this study combined with exposure, efficacy, and safety data from the pivotal study in the relevant patient population will inform final dosing recommendations.

Rabbit ATG/ATLG in preventing graft-versus-host disease after allogeneic stem cell transplantation: consensus-based recommendations by an international expert panel

This collaborative initiative aimed to provide recommendations on the use of polyclonal antithymocyte globulin (ATG) or anti-T lymphocyte globulin (ATLG) for the prevention of graft-versus-host disease (GvHD) after allogeneic hematopoietic stem cell transplantation (HSCT). A comprehensive review of articles released up to October, 2018 was performed as a source of scientific evidence. Fourteen clinically relevant key questions to the domains indication, administration, and post-transplant management were developed and recommendations were produced using the Delphi technique involving a Panel of 14 experts. ATG/ATLG was strongly recommended as part of myeloablative conditioning regimen prior to matched or mismatched unrelated bone marrow or peripheral blood allogeneic HSCT in malignant diseases to prevent severe acute and chronic GvHD. ATG/ATLG was also recommended prior to HLA-identical sibling peripheral HSCT with good but lesser bulk of evidence. In reduced intensity or nonmyeloablative conditioning regimens, ATG/ATLG was deemed appropriate to reduce the incidence of acute and chronic GvHD, but a higher risk of relapse should be taken into account. Recommendations regarding dose, application, and premedication were also provided as well as post-transplant infectious prophylaxis and vaccination. Overall, these recommendations can be used for a proper and safe application of polyclonal ATG/ATLG to prevent GvHD after allogeneic HSCT.

Role of pretransplant anti-thymocyte globulin in matched sibling donor stem cell transplantation after reduced intensity conditioning for myelodysplastic syndrome

OBJECTIVE

We investigated the role of anti-thymocyte globulin (ATG; Thymoglobulin) in matched sibling donor hematopoietic stem cell transplantation (MSD-HSCT) after reduced intensity conditioning (RIC) in myelodysplastic syndrome (MDS).

METHODS

Forty-seven patients with 10 mg/kg ATG (ATG group; median age 53 years) and 33 without ATG (no-ATG group; median age 43, P < .0001) were compared.

RESULTS

Median time to engraftment was similar. Two-year cumulative incidence of moderate-to-severe chronic graft-versus-host disease (GVHD) was significantly lower in the ATG group (15% vs 55%, P < .0001), while that of acute GVHD was similar compared with the no-ATG group. After a median follow-up of 60 months (range, 14-184), the 3-year cumulative incidences of non-relapse mortality and relapse were 9% and 21% for ATG group and 15% and 19% for no-ATG group (P = .408 and P = .717), respectively, leading to a significantly better 3-year GVHD-free and relapse-free survival (GRFS) in the ATG group (55% vs 19%, P = .006): The 3-year overall and disease-free survival were similar. Infectious complication occurred with similar frequencies in both groups.

CONCLUSION

These findings suggest that ATG can be safely used to decrease moderate-to-severe chronic GVHD with improved GRFS for patients with MDS receiving MSD-HSCT in RIC setting.

Successful outcome with reduced-intensity condition regimen followed by allogeneic hematopoietic stem cell transplantation for relapsed or refractory anaplastic large-cell lymphoma

We report a retrospective analysis of 38 patients (age ≤ 30 years) who underwent allogeneic hematopoietic stem cell transplantation (allo-SCT) for relapsed or refractory anaplastic large-cell lymphoma (ALCL). Median follow-up for survivors after undergoing allo-SCT was 72 months (range, 35-96 months). Eight patients received reduced-intensity conditioning (RIC) regimens, including three patients with fludarabine plus melphalan-based regimens and five patients with fludarabine plus busulfan-based regimens. The remaining 30 patients received myeloablative conditioning (MAC) regimens. Median ages in the RIC and MAC groups were 24 and 15 years, respectively. The 5-year overall survival rates in the RIC and MAC groups were 100% and 49%, respectively (P = 0.018). The 5-year event-free survival rates in the RIC and MAC groups were 88% and 43%, respectively (P = 0.039). In the RIC group, four of the eight patients showed residual disease at allo-SCT, but all eight patients survived with complete remission (CR), including one patient with relapse. This result suggests that allo-SCT using the RIC regimen may be effective for relapsed or refractory ALCL in children, adolescents, and young adults, even in non-CR cases.

Influence of Donor Type (Sibling versus Matched Unrelated Donor versus Haploidentical Donor) on Outcomes after Clofarabine-Based Reduced-Intensity Conditioning Allograft for Myeloid Malignancies

Clofarabine-based reduced-intensity conditioning (RIC) regimens are well-established schedules for allograft in patients with myeloid malignancies. A retrospective study was conducted including all adults allografted in our department with such a regimen and disease with the aim to assess whether or not the donor type (matched sibling [MSD], matched unrelated [MUD], or haploidentical [haplo]) impacted outcomes. Between October 2009 and February 2018, 118 patients met the inclusion criteria. Thirty-six, 55, and 27 patients received a graft from an MSD, MUD, or haplo donor, respectively. Peripheral blood stem cells (PBSCs) were the source of graft for all patients. The median age of the entire cohort was 62 years (range, 20 to 73), and the median follow-up was 31 months (range, 4.5 to 106). All patients engrafted except 1 haplo recipient. Neutrophils (>.5 × 10⁹/L) and platelets (50 × 10⁹/L) recoveries were significantly delayed in the haplo group (P = .0003 and P < .0001) compared with MSD and MUD. Acute grades II to IV or III to IV graft-versus-host disease (GVHD) incidences were similar between the 3 groups as well as the incidence of moderate or severe chronic GVHD. Also, similar 2-year overall survival (OS; 64.7% versus 73.9% versus 60.2%, P = .39), disease-free survival (DFS; 57.7% versus 70.9% versus and 53.6%, P = .1), and GVHD relapse-free survival (37.9% versus 54.3% versus 38.9%, P = .23) were observed between MSD versus MUD versus haplo groups. The same was true when considering only acute myeloid leukemia (AML) cases. In multivariate analysis the type of donor remained independent of outcomes in this series, whereas myelodysplastic syndrome (versus AML), high disease risk index, and older donor (≥50 years) were associated with lower OS and DFS. These data suggest that haplo donors are an acceptable alternative for patients receiving a clofarabine-based RIC PBSC allograft for myeloid malignancies who lack an MSD or a MUD.

Antithymocyte globulin for graft-versus-host disease prophylaxis: an updated systematic review and meta-analysis

Graft-versus-host disease (GVHD) remains a limiting factor for successful allogeneic hematopoietic cell transplantation (allo-HCT). Conflicting data exist on the benefit of ATG on post-transplant survival. We performed a systematic review of randomized controlled trials (RCTs) to assess benefits and harms of thymoglobulin and Fresenius (re-branded as Grafalon) ATG formulations in patients undergoing allo-HCT for a variety of hematologic malignancies and bone marrow failure syndromes. A comprehensive search of MEDLINE, EMBASE, and Cochrane Library was performed. Data on methodological quality, benefits, and harms were extracted for each trial and pooled under a random-effects model. Eight RCTs (1134 patients) met the inclusion criteria. Methodological quality ranged from moderate to very low. Pooled results showed no difference in overall survival (OS) with the use of ATG (hazard ratio (HR) = 0.97; 95% confidence interval (CI) = 0.74-1.28; P = 0.83). ATG reduced grade II/III acute GVHD (risk ratio (RR) = 0.61; 95% CI = 0.48-0.77; P < 0.0001), grade III/IV acute GVHD (RR = 0.52; 95% CI = 0.34-0.81; P = 0.004), and chronic GVHD (RR = 0.52; 95% CI = 0.40-0.69; P < 0.00001) without an increase in non-relapse mortality (NRM) (RR = 0.91; 95% CI = 0.74-1.13; P = 0.40). Future studies with better methodological quality are needed to provide conclusive answers related to optimal dosing and timing of ATG for prevention of GVHD.

Reduced intensity conditioning increases risk of severe cGVHD: identification of risk factors for cGVHD in a multicenter setting

Chronic graft-versus-host disease (cGVHD) remains a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). Aim is to identify risk factors for the development of cGVHD in a multicenter setting. Patients transplanted between 2000 and 2006 were analyzed (n = 820). Donors were HLA-identical siblings (57%), matched unrelated donors (30%), and HLA-A, B or DR antigen mismatched (13%). Reduced intensity conditioning (RIC) was given to 65% of patients. Overall incidence of cGVHD was 46% for patients surviving more than 100 days after HSCT (n = 747). Older patient age [HR 1.15, p < 0.001], prior acute GVHD [1.30, p = 0.024], and RIC [1.36, p = 0.028] increased overall cGVHD. In addition, RIC [4.85, p < 0.001], prior aGVHD [2.14, p = 0.001] and female donor to male recipient [1.80, p = 0.008] increased the risk of severe cGVHD. ATG had a protective effect for both overall [0.41, p < 0.001] and severe cGVHD [0.20, p < 0.001]. Relapse-free survival (RFS) was impaired in patients with severe cGVHD. RIC, prior aGVHD, and female-to-male donation increase the risk of severe cGVHD. ATG reduces the risk of all grades of cGVHD without hampering RFS. GVHD prophylaxis may be tailored according to the risk profile of patients.

Role of thymoglobulin in matched sibling allogeneic hematopoietic stem cell transplantation with busulfan and fludarabine conditioning in myeloid malignanicies

In vivo T-cell depletion using anti-thymocyte globulin (ATG) is widely used in allogeneic hematopoietic stem cell transplantation (HSCT) for prophylaxis of GvHD. We investigated the influence of thymoglobulin dose (an ATG) on GvHD following matched sibling donor (MSD) HSCT with a busulfan and fludarabine preparative regimen. Medical records of 180 patients who received MSD HSCT with a conditioning regimen of busulfan, fludarabine, and ATG (BuFluATG) were reviewed retrospectively. The median age was 53 years (range 18-68). Initial diagnoses were acute myeloid leukemia (73.3%) and myelodysplastic syndrome (26.7%). Forty-four and 68 patients (24.4 and 37.7%) experienced acute and chronic GvHD of any grade, respectively. High-dose (⩾4.5 mg/kg) ATG was independently associated with decreased risk of acute GvHD (hazard ratio=0.36, 95% confidence interval (CI): 0.15-0.84, P=0.019) compared to low-dose ATG (<4.5 mg/kg). Although ATG dose was associated with the risk of acute GvHD, it was not associated with the risk of chronic GvHD in our study. A higher dose (⩾4.5 mg/kg) of ATG decreases the risk of acute GvHD but had no significant impact on disease-free survival in MSD HSCT patients conditioned with BuFluATG. The optimal dose of ATG should be further investigated in a large prospective study context.

Dissecting the mechanisms involved in anti-human T-lymphocyte immunoglobulin (ATG)-induced tolerance in the setting of allogeneic stem cell transplantation - potential implications for graft versus host disease

Polyclonal anti-human thymocyte globulins (ATG) have been recently shown to significantly reduce the incidence of graft versus host disease (GVHD) post allogeneic stem cell transplantation (HSCT) from both sibling and unrelated donors. Induction of regulatory T cells has been suggested as one of the possible mechanisms. The aim of current study was to further characterize the T cell populations induced by ATG treatment and to delineate the mechanisms involved in ATG-induced tolerance. Phenotypic characterization revealed a significant increase in the expression of FoxP3, GITR, CD95, PD-1 and ICOS as well as the complement inhibitory molecules CD55, CD58 and CD59 on CD4+CD25+ T cells upon ATG treatment. Addition of ATG-treated cells to autologous and allogeneic peripheral blood mononuclear cells (PBMCs) stimulated with anti-CD3/anti-CD28 antibodies resulted in significant inhibition of proliferation. Moreover, T-cell activation and IFNγ secretion were reduced in the presence of ATG-induced Treg cells. The CD4+CD25+CD127-low Treg fraction sorted from ATG-treated culture demonstrated greater suppressive potency than negative fraction. Conditioned medium produced by ATG-treated but not IgG-treated cells contained TGFβ and suppressed T cell proliferation and activation in a TGFβ receptor-dependent manner. TGFβ receptor kinase inhibitor SB431542 interfered with the suppressive activity of ATG-primed cells, enabling partial rescue of proliferation and IFNγ secretion. Moreover, SB431542 prevented Treg phenotype induction upon ATG treatment. Altogether, our data reveal the role of TGFβ signaling in ATG-mediated immunosuppression and further support the use of ATG, a potent inducer of regulatory T cells, for prevention of GVHD post HSCT and potentially other therapeutic applications.

Extracorporeal photopheresis for GVHD prophylaxis after reduced intensity conditioning allogeneic hematopoietic stem cell transplantation: a prospective multicenter phase 2 study

We performed a prospective multicenter phase 2 study to evaluate the safety and efficacy of prophylactic Extracorporeal Photopheresis (ECP) in adult patients with hematological malignancies early after RIC allo-HSCT on day 21 twice per week during the first two weeks and then once per week for the next four weeks for a total of eight ECP courses. A total of 20 patients were included; 10 were males, median age was 60 years. All patients engrafted, 17 (85%) received the total eight ECP courses. There were no adverse effects related to ECP. Seven patients developed acute graft-versus-host disease (GVHD), with 15% grade ≥ II cumulative incidence at day 100. The cumulative incidence of chronic GVHD at 2 years was 22%. The 2 years probability of overall survival (OS) and progression-free survival (PFS) were 84 and 74%, respectively. This study shows encouraging results with low acute and chronic GVHD incidence and no interference with graft-versus-leukemia (GVL) effect.

Reduced-Intensity Conditioning with Busulfan, Fludarabine, and Antithymocyte Globulin for Hematopoietic Cell Transplantation from Unrelated or Haploidentical Family Donors in Patients with Acute Myeloid Leukemia in Remission

To investigate the role of antithymocyte globulin (ATG)-containing reduced-intensity conditioning (RIC) in hematopoietic cell transplantation (HCT) from unrelated (UD) or haploidentical family donors (HFD), we conducted a phase 2 trial of 237 patients (age range, 16 to 69 years) with acute myeloid leukemia (AML) in remission. Patients undergoing UD-HCT (n = 93) or HFD-HCT (n = 59) received RIC comprising busulfan, fludarabine, and ATG, 9 mg/kg, whereas those undergoing HCT from matched sibling donors (MSD, n = 85) received myeloablative busulfan and cyclophosphamide conditioning or aforementioned RIC with ATG, 4.5 mg/kg. For graft-versus-host disease (GVHD) prophylaxis, cyclosporine and methotrexate were administered. The median follow-up period was 44.7 months after HCT for 161 survivors. For UD-HCT versus HFD-HCT, there were no significant differences in leukemia recurrence, nonrelapse mortality, relapse-free survival, grades 2 to 4 acute GVHD, and moderate-to-severe chronic GVHD. Furthermore, when the outcomes of UD-HCT and HFD-HCT were combined and compared with those of MSD-HCT, there were no significant differences in leukemia recurrence (3-year cumulative incidence, 30% versus 29%), nonrelapse mortality (3-year cumulative incidence, 7% versus 8%), relapse-free survival (3-year estimate, 63% versus 63%), and grades 2 to 4 acute GVHD (120-day cumulative incidence, 16% versus 13%). Moderate-to-severe chronic GVHD, however, occurred less frequently in UD/HFD-HCT (2-year cumulative incidence, 22% versus 40%; P = .006). The addition of ATG to conditioning regimen was a significant predictor for less chronic GVHD (subdistribution hazard ratio, .59). In AML in remission, UD/HFD-HCT after ATG-containing RIC achieved leukemia control equivalent to that of MSD-HCT. Despite HLA disparity in UD/HFD-HCT, chronic GVHD occurred less frequently after ATG-containing RIC, suggesting a strong GVHD-modulating effect of ATG.

Reduced-intensity and non-myeloablative allogeneic stem cell transplantation from alternative HLA-mismatched donors for Hodgkin lymphoma: a study by the French Society of Bone Marrow Transplantation and Cellular Therapy

Allogeneic stem cell transplantation (allo-SCT) following a non-myeloablative (NMA) or reduced-intensity conditioning (RIC) is considered a valid approach to treat patients with refractory/relapsed Hodgkin lymphoma (HL). When an HLA-matched donor is lacking a graft from a familial haploidentical (HAPLO) donor, a mismatched unrelated donor (MMUD) or cord blood (CB) might be considered. In this retrospective study, we compared the outcome of patients with HL undergoing a RIC or NMA allo-SCT from HAPLO, MMUD or CB. Ninety-eight patients were included. Median follow-up was 31 months for the whole cohort. All patients in the HAPLO group (N=34) received a T-cell replete allo-SCT after a NMA (FLU-CY-TBI, N=31, 91%) or a RIC (N=3, 9%) followed by post-transplant cyclophosphamide. After adjustment for significant covariates, MMUD and CB were associated with significantly lower GvHD-free relapse-free survival (GRFS; hazard ratio (HR)=2.02, P=0.03 and HR=2.43, P=0.009, respectively) compared with HAPLO donors. In conclusion, higher GRFS was observed in Hodgkin lymphoma patients receiving a RIC or NMA allo-SCT with post-transplant cyclophosphamide from HAPLO donors. Our findings suggest they should be favoured over MMUD and CB in this setting.

Impact of ATG Dose on the Outcome of Patients Undergoing Reduced Intensity Conditioning Followed by Allogeneic Hematopoietic Stem Cell Transplantation for Hematological Malignancies

Reduced intensity conditioning for allogeneic hematopoietic stem cell transplantation (allo-HSCT) is often proposed for patients with comorbidities. To enhance engraftment and limit graft-versus-host disease (GVHD), antithymoglobulin (ATG) is usually used. However, the dose needed remains unclear unlike myeloablative conditioning. In order to clarify this point, we conducted a retrospective study on patients who received a reduced intensity conditioning allo-HSCT based on a 2-day fludarabine and busulfan treatment with either 1 or 2 days of ATG treatment. One hundred and eight patients received 2.5 mg/kg (ATG2.5) and another 60 patients 5 mg/kg (ATG5). The median follow-up was 36 months. The median overall survival was 39 months and the median disease-free survival 45 months. In multivariate analysis, overall nonrelapse mortality (NRM) was independently influenced by the acute GVHD grade III-IV (p < 0.001) and ATG dose (30 vs. 21% for ATG5; p = 0.008). Despite heterogeneity of populations, using proportional-hazard assumptions, we have been able to observe in multivariate analysis a lower NRM in the ATG5 group. This leads to a statistically higher overall survival for the ATG5 group. In conclusion, 2 days of ATG decrease NRM independently without increasing the risk of relapse or infectious disease.

Impact of low-dose rabbit anti-thymocyte globulin in unrelated hematopoietic stem cell transplantation

We retrospectively evaluated the outcome of administering low-dose rabbit anti-thymocyte globulin (thymoglobulin: ATG-T) to 219 patients (ATG-T group, n = 30; no-ATG-T group, n = 189) who received an initial unrelated hematopoietic stem cell transplantation (uHSCT). The median total dose of ATG-T was 1.5 mg/kg. There was no significant difference in the cumulative incidences of grade II-IV (42 vs. 38 %, P = 0.87) and grade III-IV (5 vs. 7 %, P = 0.52) acute GVHD. In patients who received uHSCT from a donor with at least one HLA allele mismatch, the cumulative incidence of extensive chronic GVHD was significantly lower in the ATG-T group than that in the no-ATG-T group (13 vs. 44 %, P = 0.02). No patient in the ATG-T group developed chronic lung dysfunction. The probabilities of 1-year, GVHD-free/relapse-free survival (GRFS) were 61 % in the ATG-T group and 35 % in the no-ATG-T group (P = 0.02). Patients in the ATG-T group discontinued immunosuppressive drugs significantly earlier than those in the no-ATG-T group (P < 0.01). The use of low-dose ATG-T did not increase the incidence of severe infectious disease. The use of low-dose ATG-T in patients who received uHSCT was associated with a superior GRFS, reflecting the reduced incidence of severe/persistent GVHD without compromising overall survival.

Hematopoietic stem cell transplantation for patients with AML in first complete remission

Postremission therapy in patients with acute myeloid leukemia (AML) may consist of continuing chemotherapy or transplantation using either autologous or allogeneic stem cells. Patients with favorable subtypes of AML generally receive chemotherapeutic consolidation, although recent studies have also suggested favorable outcome after hematopoietic stem cell transplantation (HSCT). Although allogeneic HSCT (alloHSCT) is considered the preferred type of postremission therapy in poor- and very-poor-risk AML, the place of alloHSCT in intermediate-risk AML is being debated, and autologous HSCT is considered a valuable alternative that may be preferred in patients without minimal residual disease after induction chemotherapy. Here, we review postremission transplantation strategies using either autologous or allogeneic stem cells. Recent developments in the field of alternative donors, including cord blood and haploidentical donors, are highlighted, and we discuss reduced-intensity alloHSCT in older AML recipients who represent the predominant category of patients with AML who have a high risk of relapse in first remission.

Differential impact of two doses of antithymocyte globulin conditioning on lymphocyte recovery upon haploidentical hematopoietic stem cell transplantation

Background

In vivo depletion of host T cells with antithymocyte globulin (ATG) is a common strategy for preventing graft-versus-host disease in allogeneic hematopoietic stem cell transplantation (HSCT). The total dose of ATG in conditioning regimens appears to be an important factor that influences the outcome in recipients of transplants. However, the optimal ATG dosage has not been established to date. It remains unclear whether, in the setting of haploidentical HSCT (haploHSCT), different doses of ATG might exert differential influences on the recovery of lymphocyte subpopulations.

Methods

This retrospective study analyzed lymphocyte recovery and its correlation to viral infection in two groups of patients that received different doses of ATG before haploHSCT. We performed flowcytometry to determine immunophenotypes of CD19⁺ B cells and CD3⁺, CD4⁺, CD8⁺, CD4⁺CD45RA⁺, CD4⁺CD45RO⁺, CD4⁺CD28⁺, CD8⁺CD28⁺, and CD4⁻CD8⁻ T cells.

Results

We found that, compared to 6 mg/kg, 10 mg/kg ATG significantly hampered the recoveries of CD4⁺, CD4⁺CD45RA⁺, and CD4⁺CD45RO⁺ T cells in the first 2 months following haploHSCT. Similarly, compared to 6 mg/kg, the 10 mg/kg dose of ATG negatively influenced the recoveries of CD4⁻CD8⁻ and CD8⁺CD28⁺ T cells; recovery was delayed for 6 and 12 months after transplantation, respectively. Moreover, we showed that an increase in Epstein-Barr virus (EBV) infections, associated with the higher dose of ATG, was correlated with the delayed recovery of CD4⁻CD8⁻ double negative T cells.

Conclusions

The present study revealed a differential impact of different ATG conditioning doses on the recoveries of T cell subpopulations post-haploHSCT. This study was the first to connect the recovery of CD4⁻CD8⁻ T cells to the risk of EBV infection after HSCT. These findings will facilitate optimization of the ATG conditioning dosage and improve the outcome of patients with leukemia that receive haploHSCT.

Impact of the source of hematopoietic stem cell in unrelated transplants: comparison between 10/10, 9/10-HLA matched donors and cord blood

In absence of available matched-related or unrelated donor (MUD), mismatched unrelated donors (MMUD) and unrelated cord blood (UCB) are both considered to be suitable donors, with similar post-transplant overall survival. In most of these retrospective comparisons, HLA typing of adult donors was performed at eight loci. The aim of this study was to compare the outcome of patients transplanted from UCB (N = 64) with those transplanted from 9/10-HLA MMUD (N = 84) or 10/10-HLA MUD (N = 196). In multivariate analysis, UCB was associated with less Grade II-IV acute GVHD in comparison with MUD (aHR 1.97, 95% CI 1.19-3.27, P = 0.009) and MMUD transplants (aHR 1.79, 95% CI 1.02-3.15, P = 0.042), while the cumulative incidence of chronic GVHD was not significantly different between the three groups. Overall survival (OS), non-relapse mortality, and relapse were not different between MMUD and UCB transplantation, whereas OS was impaired after UCB in comparison with MUD (aHR 0.65, 95% CI 0.43-0.99, P = 0.043). Factors also impacting OS were the donor/recipient CMV serostatus (Donor-/Recipient+ aHR 1.76, 95% CI 1.23-2.52, P = 0.002 compared with D-/R-), the donor/recipient gender combination (Female/Male versus other combinations aHR 1.57, 95% CI 1.11-2.22, P = 0.012) and disease risk (aHR 1.58, 95% CI 1.05-2.38, P = 0.027 for high vs. low risk disease). Our data confirm that UCB and 9/10-HLA MMUD are both relevant alternative options when no 10/10-HLA donor is available. Donor/recipient gender combination and CMV serostatus had a significant impact on survival and may be taken into account, along with donor type, in the setting of MMUD and UCB transplants.

Reduced-intensity conditioning with fludarabine and busulfan for allogeneic hematopoietic cell transplantation in elderly or infirm patients with advanced myeloid malignancies

We report a retrospective single-center analysis of 112 consecutive patients that underwent allogeneic hematopoietic cell transplantation (HCT) after reduced-intensity conditioning (RIC) with fludarabine (FLU) and busulfan (BU) for the treatment of acute myeloid leukemia (AML), myelodysplastic syndrome (MDS) and myeloproliferative syndrome (MPS) from 2005 to 2014. Three-year event-free survival (EFS) and overall survival (OS) were 46 and 58 %, respectively. Patients ≥60 years of age showed a similar outcome compared to younger patients (3-year OS 55 vs. 61 %, p = 0.96; 3-year EFS 46 vs. 46 %, p = 0.82). Cumulative incidence of non-relapse mortality (NRM) at 3 years adjusted for relapse as competing risk was 25 % for patients aged <60 years and 15 % for older patients (p = 0.15). Infusions of higher CD34(+) blood stem cell doses were associated with a significantly better outcome in the elderly subgroup (3-year OS 82 vs. 39 %, p = 0.007). Moreover, complete donor chimerism at day +100 was associated with a significantly improved survival (3-year OS 69 vs. 23 %, p = 0.003). In conclusion, our data suggest that RIC with FLU/BU enables long-term disease-free survival even in an elderly patient population. Age has no negative impact on the outcome of allogeneic HCT, and decision for transplant should be based on disease risk and performance status rather than age alone.

Pushing the envelope-nonmyeloablative and reduced intensity preparative regimens for allogeneic hematopoietic transplantation

Allogeneic hematopoietic cell transplantation (HCT) was originally developed to allow delivery of myeloablative doses of chemotherapy and radiotherapy. With better understanding of disease pathophysiology, the graft vs malignancy (GVM) effect of allogeneic hematopoietic transplantation and toxicities associated with myeloablative conditioning (MAC) regimens, the focus shifted to developing less toxic conditioning regimens to reduce treatment-related morbidity without compromising survival. Although HCT with MAC is preferred to reduced intensity conditioning (RIC) for most patients ⩽60 years with AML/myelodysplastic syndrome and ALL, RIC and nonmyeloablative (NMA) regimens allow HCT for many otherwise ineligible patients. Reduced intensity preparative regimens have produced high rates of PFS for diagnoses, which are highly sensitive to GVM. Relapse of the malignancy is the major cause of treatment failure with RIC/NMA HCT. Incorporation of novel agents like bortezomib or lenalidomide, addition of cellular immunotherapy and use of targeted radiation therapies could further improve outcome. In this review, we discuss commonly used RIC/NMA regimens and promising novel regimens.

Impact of Pre-Transplant Anti-T Cell Globulin (ATG) on Immune Recovery after Myeloablative Allogeneic Peripheral Blood Stem Cell Transplantation

Background

Pre-transplant infusion of rabbit anti-T cell globulin (ATG) is increasingly used as prevention of graft-versus-host disease (GVHD) after allogeneic peripheral blood stem cell transplantation (PBSCT). However, the precise impact of pre-transplant ATG on immune recovery after PBSCT is still poorly documented.

Methods

In the current study, we compared immune recovery after myeloablative PBSCT in 65 patients who either received (n = 37) or did not (n = 28) pre-transplant ATG-Fresenius (ATG-F). Detailed phenotypes of circulating T, B, natural killer (NK) and invariant NKT (iNKT) cells were analyzed by multicolor flow cytometry at serial time-points from day 40 to day 365 after transplantation. Thymic function was also assessed by sjTREC quantification. Serious infectious events were collected up to 2 years post-transplantation.

Results

Pre-transplant ATG-F had a prolonged (for at least up to 1-year) and selective negative impact on the T-cell pool, while it did not impair the recovery of B, NK nor iNKT cells. Among T cells, ATG-F selectively compromised the recovery of naïve CD4⁺, central memory CD4⁺ and naïve CD8⁺ cells, while it spared effector memory T and regulatory T cells. Levels of sjTRECs were similar in both cohorts at 1-year after PBSCT, suggesting that ATG-F unlikely impaired thymopoiesis at long-term after PBSCT. Finally, the incidence and rate of serious infections were similar in both groups, while ATG-F patients had a lower incidence of grade II-IV acute graft-versus-host disease.

Conclusions

Pre-transplant ATG-F induces long-lasting modulation of the circulating T-cell pool after myeloablative PBSCT, that may participate in preventing graft-versus-host disease without deeply compromising anti-pathogen defenses.

Dynamical System Modeling of Immune Reconstitution after Allogeneic Stem Cell Transplantation Identifies Patients at Risk for Adverse Outcomes

Systems that evolve over time and follow mathematical laws as they evolve are called dynamical systems. Lymphocyte recovery and clinical outcomes in 41 allograft recipients conditioned using antithymocyte globulin (ATG) and 4.5-Gy total body irradiation were studied to determine if immune reconstitution could be described as a dynamical system. Survival, relapse, and graft-versus-host disease (GVHD) were not significantly different in 2 cohorts of patients receiving different doses of ATG. However, donor-derived CD3(+) cell reconstitution was superior in the lower ATG dose cohort, and there were fewer instances of donor lymphocyte infusion (DLI). Lymphoid recovery was plotted in each individual over time and demonstrated 1 of 3 sigmoid growth patterns: Pattern A (n = 15) had rapid growth with high lymphocyte counts, pattern B (n = 14) had slower growth with intermediate recovery, and pattern C (n = 10) had poor lymphocyte reconstitution. There was a significant association between lymphocyte recovery patterns and both the rate of change of donor-derived CD3(+) at day 30 after stem cell transplantation (SCT) and clinical outcomes. GVHD was observed more frequently with pattern A, relapse and DLI more so with pattern C, with a consequent survival advantage in patients with patterns A and B. We conclude that evaluating immune reconstitution after SCT as a dynamical system may differentiate patients at risk of adverse outcomes and allow early intervention to modulate that risk.

Low non-relapse mortality and long-term preserved quality of life in older patients undergoing matched related donor allogeneic stem cell transplantation: a prospective multicenter phase II trial

Allogeneic transplantation is a challenge in patients of advanced age because of a high risk of non-relapse mortality and potential long-lasting impairment of health-related quality of life. The development of reduced-intensity conditioning regimens has allowed the use of allogeneic transplantation in this population, but the optimal regimen remains undefined. We conducted a multicenter phase II trial evaluating the safety and efficacy of a reduced-intensity conditioning regimen combining fludarabine, intravenous busulfan, and rabbit antithymocyte globulins in patients older than 55 years of age transplanted from matched-related donor. In addition, health-related quality of life was prospectively measured. Seventy-five patients with a median age of 60 years (range 55-70) were analyzed. Grade III-IV acute and extensive chronic graft-versus-host diseases were found in 3% and 27% of patients, respectively. The day 100 and 1-year non-relapse mortality incidences were 1% and 9%, respectively. The cumulative incidences of relapse, progression-free survival and overall survival at two years were 36%, 51% and 67%, respectively, with a median follow up of 49 months. Global health-related quality of life, physical functioning, emotional functioning, and social functioning were not impaired compared to baseline for more than 75% of the patients (75%, 81.4%, 82.3%, and 75%, respectively). Thirty-four of the 46 (74%) progression-free patients at one year were living without persistent extensive chronic graft-versus-host disease. We conclude that the reduced-intensity conditioning regimen combining fludarabine, intravenous busulfan, and rabbit antithymocyte globulins is well tolerated in patients older than 55 years with low non-relapse mortality and long-term preserved quality of life.

Low-dose antithymocyte globulin enhanced the efficacy of tacrolimus and mycophenolate for GVHD prophylaxis in recipients of unrelated SCT

We performed a retrospective analysis of the outcome of 197 consecutive unrelated donor transplant recipients who received GVHD prophylaxis either TM regimen (tacrolimus and mycophenolate) (121 patients) or TM/ATG-G regimen (TM with low-dose antithymocyte globulin (ATG) of 4.5 mg/kg, ATG-G, Genzyme) (76 patients). Cumulative incidences of grade II-IV acute GVHD for the TM and TM/ATG-G cohorts were 49% and 61% (P=0.11) and grade III-IV acute GVHD for the TM and TM/ATG-G cohorts were 27% and 14% (P=0.02), respectively. There was no difference in the incidence of relapse or disease progression between TM and TM/ATG-G-16% and 23% (P=0.64). TM/ATG-G cohort had lower incidence of non-relapse mortality (NRM; 37% vs 20%, P=0.01), chronic GVHD (56% vs 43%, P<0.001) and more favorable global chronic GVHD severity (P<0.001). Univariate analyses showed improved OS and PFS of patients who received TM/ATG-G. Multivariate analysis confirmed TM/ATG-G had a favorable influence on OS (P=0.05) but not on PFS (P=0.07). We concluded that low-dose ATG of 4.5 mg/kg given in conjunction with TM improved GVHD prophylaxis without increased risk of relapse. Lower NRM, lower incidence and severity of chronic GVHD could potentially improve survival.

Poor outcome with nonmyeloablative conditioning regimen before cord blood transplantation for patients with high-risk acute myeloid leukemia compared with matched related or unrelated donor transplantation

Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) is recommended for patients with high-risk acute myeloid leukemia (AML). In many situations, a matched related (MRD) or matched unrelated donor (MUD) is lacking, in which case unrelated cord blood units (UCB) provide an alternative. We analyzed the outcome of consecutive high-risk AML patients prepared with reduced-intensity conditioning (RIC) regimens and allografted with UCB (n = 32) and compared their outcome with high-risk AML patients who underwent transplantation with MRD/MUD (n = 49) in the same period of time. Grade III to IV acute graft-versus-host disease (GVHD) occurred slightly more frequently in the UCB group (25%) than in the MRD/MUD group (8%) (P = .069). Conversely, we found a lower incidence of extensive chronic GVHD in the UCB group (6%) than in the MRD/MUD group (20%, P = .085). Nonrelapse mortality at 4 years was 16% and 22% in the UCB and MRD/MUD groups, respectively (P = .529). The cumulative incidence of relapse at 4 years was significantly higher in the UCB group (60%) than in the MRD/MUD group (27%, P = .006). Leukemia-free survival (LFS) and overall survival (OS) at 4 years were 25% and 34%, respectively, in the UCB group and 50% and 56%, respectively, in the MRD/MUD group (LFS, P = .029; OS, P = .072). Multivariate analyses adjusted by cytogenetics and disease status at the time of Allo-HSCT revealed that use of UCB remained an independent predictive factor of shorter LFS (hazard ratio, 2.0; 95% confidence interval, 1.1 to 3.6; P = .018), and was associated with a trend for shorter OS (hazard ratio, 1.7; 95% confidence interval, .9 to 3.2; P = .093). Whereas UCB provides an alternative for patients with high-risk AML lacking an MRD/MUD, the high incidence of relapse after RIC-based UCB Allo-HSCT is a concern. Attempts to improve leukemic control with UCB Allo-HSCT are warranted, as well as the evaluation of other alternative donors in this context.

Conditioning regimens for hematopoietic cell transplantation: one size does not fit all

An essential component of allogeneic and autologous hematopoietic cell transplantation (HCT) is the conditioning regimen administered before the hematopoietic cell infusion. Early regimens relied on dose intensity, assuming that high-dose chemoradiotherapy would eliminate malignant disease and reinfusion of the graft would then restore hematopoiesis. However, as the contribution of graft-versus-tumor effects to the success of allogeneic HCT was recognized over time, in an effort to exploit these, many investigators lowered the dose of radiation and chemotherapeutic agents in the preparative regimen. This resulted in a major paradigm shift, and consequently, the pool of eligible patients underwent a remarkable expansion. In this article, we provide a review of the definition of high-dose, reduced-intensity, and nonmyeloablative conditioning regimens, the most commonly used agents and combinations, and the evolution of some early regimens. We also provide a brief review of the toxicities associated with these regimens.