T-Cell–Depleted Allogeneic Bone Marrow Transplantation as Postremission Therapy for Acute Myelogenous Leukemia: Freedom From Relapse in the Absence of Graft-Versus-Host Disease

Application of the CIBMTR One Year Survival Outcomes Calculator as a tool for retrospective analysis

The Web-based One Year Survival Outcomes Calculator developed by the Center for International Blood and Marrow Transplant Research (CIBMTR) applies large-scale registry data to generate individualized estimates of overall survival (OS) probability 1 year after first allogeneic hematopoietic cell transplant (HCT) and can therefore provide a data-driven foundation for personalized patient counseling. We assessed the calibration of the CIBMTR One Year Survival Outcomes Calculator when applied to retrospective data among adult recipients of first allogeneic HCT for acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), or myelodysplastic syndrome (MDS) with peripheral blood stem cell transplant (PBSCT) from a 7/8- or 8/8-matched donor from 2000 through 2015 at a single center. Predicted 1 year OS was estimated for each patient using the CIBMTR Calculator. Corresponding observed 1 year OS was estimated for each group by the Kaplan-Meier method. A weighted Kaplan-Meier estimator was used to visually display the average of observed 1 year survival estimates over the continuous range of predicted OS. In the first analysis of its kind, we demonstrated that the CIBMTR One Year Survival Outcomes Calculator could be applied to larger patient cohorts and predicted 1 year prognosis with general agreement between predicted and observed survival.

How I prevent GVHD in high-risk patients: posttransplant cyclophosphamide and beyond

Advances in conditioning, graft-versus-host disease (GVHD) prophylaxis and antimicrobial prophylaxis have improved the safety of allogeneic hematopoietic cell transplantation (HCT), leading to a substantial increase in the number of patients transplanted each year. This influx of patients along with progress in remission-inducing and posttransplant maintenance strategies for hematologic malignancies has led to new GVHD risk factors and high-risk groups: HLA-mismatched related (haplo) and unrelated (MMUD) donors; older recipient age; posttransplant maintenance; prior checkpoint inhibitor and autologous HCT exposure; and patients with benign hematologic disorders. Along with the changing transplant population, the field of HCT has dramatically shifted in the past decade because of the widespread adoption of posttransplantation cyclophosphamide (PTCy), which has increased the use of HLA-mismatched related donors to levels comparable to HLA-matched related donors. Its success has led investigators to explore PTCy's utility for HLA-matched HCT, where we predict it will be embraced as well. Additionally, combinations of promising new agents for GVHD prophylaxis such as abatacept and JAK inhibitors with PTCy inspire hope for an even safer transplant platform. Using 3 illustrative cases, we review our current approach to transplantation of patients at high risk of GVHD using our modern armamentarium.

Impact of total marrow/lymphoid irradiation dose to the intestine on graft-versus-host disease in allogeneic hematopoietic stem cell transplantation for hematologic malignancies

Background and purpose

Graft-versus-host disease (GvHD) is a leading cause of non-relapse mortality in patients undergoing allogeneic hematopoietic stem cell transplantation. The Perugia Bone Marrow Transplantation Unit designed a new conditioning regimen with total marrow/lymphoid irradiation (TMLI) and adaptive immunotherapy. The present study investigated the impact of radiotherapy (RT) doses on the intestine on the incidence of acute GvHD (aGvHD) in transplant recipients, analyzing the main dosimetric parameters.

Materials and methods

Between August 2015 and April 2021, 50 patients with hematologic malignancies were enrolled. All patients underwent conditioning with TMLI. Dosimetric parameters (for the whole intestine and its segments) were assessed as risk factors for aGvHD. The RT dose that was received by each intestinal area with aGvHD was extrapolated from the treatment plan for each patient. Doses were compared with those of the whole intestine minus the affected area.

Results

Eighteen patients (36%) developed grade ≥2 aGvHD (G2 in 5, G3 in 11, and G4 in 2). Median time to onset was 41 days (range 23-69 days). The skin was involved in 11 patients, the intestine in 16, and the liver in 5. In all 50 TMLI patients, the mean dose to the whole intestine was 7.1 Gy (range 5.07-10.92 Gy). No patient developed chronic GvHD (cGvHD). No dosimetric variable emerged as a significant risk factor for aGvHD. No dosimetric parameter of the intestinal areas with aGvHD was associated with the disease.

Conclusion

In our clinical setting and data sample, we have found no clear evidence that current TMLI dosages to the intestine were linked to the development of aGvHD. However, due to some study limitations, this investigation should be considered as a preliminary assessment. Findings need to be confirmed in a larger cohort and in preclinical models.

Randomized Phase III BMT CTN Trial of Calcineurin Inhibitor-Free Chronic Graft-Versus-Host Disease Interventions in Myeloablative Hematopoietic Cell Transplantation for Hematologic Malignancies

PURPOSE

Calcineurin inhibitors (CNI) are standard components of graft-versus-host disease (GVHD) prophylaxis after hematopoietic cell transplantation (HCT). Prior data suggested that CNI-free approaches using donor T-cell depletion, either by ex vivo CD34 selection or in vivo post-transplant cyclophosphamide (PTCy) as a single agent, are associated with lower rates of chronic GVHD (cGVHD).

METHODS

This multicenter phase III trial randomly assigned patients with acute leukemia or myelodysplasia and an HLA-matched donor to receive CD34-selected peripheral blood stem cell, PTCy after a bone marrow (BM) graft, or tacrolimus and methotrexate after BM graft (control). The primary end point was cGVHD (moderate or severe) or relapse-free survival (CRFS).

RESULTS

Among 346 patients enrolled, 327 received HCT, 300 per protocol. Intent-to-treat rates of 2-year CRFS were 50.6% for CD34 selection (hazard ratio [HR] compared with control, 0.80; 95% CI, 0.56 to 1.15; P = .24), 48.1% for PTCy (HR, 0.86; 0.61 to 1.23; P = .41), and 41.0% for control. Corresponding rates of overall survival were 60.1% (HR, 1.74; 1.09 to 2.80; P = .02), 76.2% (HR, 1.02; 0.60 to 1.72; P = .95), and 76.1%. CD34 selection was associated with lower moderate to severe cGVHD (HR, 0.25; 0.12 to 0.52; P = .02) but higher transplant-related mortality (HR, 2.76; 1.26 to 6.06; P = .01). PTCy was associated with comparable cGVHD and survival outcomes to control, and a trend toward lower disease relapse (HR, 0.52; 0.28 to 0.96; P = .037).

CONCLUSION

CNI-free interventions as performed herein did not result in superior CRFS compared with tacrolimus and methotrexate with BM. Lower rates of moderate and severe cGVHD did not translate into improved survival.

Chimerism analysis for clinicians: a review of the literature and worldwide practices

This review highlights literature pertinent to chimerism analysis in the context of hematopoietic cell transplantation (HCT). We also conducted a survey of testing practices of program members of CIBMTR worldwide. Questions included testing methods, time points, specimen type, cell lineage tested and testing indications. Recent literature suggests that detection of low level mixed chimerism has a clinical utility in predicting relapse. There is also increasing recognition of HLA loss relapse to potentially guide rescue decisions in cases of relapse. These developments coincide with wider access to high sensitivity next generation sequencing (NGS) in clinical laboratories. Our survey revealed a heterogeneity in practices as well as in findings and conclusions of published studies. Although the most commonly used method is STR, studies support more sensitive methods such as NGS, especially for predicting relapse. There is no conclusive evidence to support testing chimerism in BM over PB, particularly when using a high sensitivity testing method. Periodic monitoring of chimerism especially in diagnoses with a high risk of relapse is advantageous. Lineage specific chimerism is more sensitive than whole blood in predicting impending relapse. Further studies that critically assess how to utilize chimerism testing results will inform evidence based clinical management decisions.

The Simplified Comorbidity Index (SCI) - a new tool for prediction of non-relapse mortality in allogeneic HCT

Cardiac, pulmonary, hepatic, and renal dysfunction were predictive of allo-HCT mortality and combined to form the SCI.

The new index stratified patients into distinct NRM risk groups and was valid in 2 cohorts.

Individual comorbidities have distinct contributions to nonrelapse mortality (NRM) following allogeneic hematopoietic cell transplantation (allo-HCT). We studied the impact of comorbidities individually and in combination in a single-center cohort of 573 adult patients who underwent CD34-selected allo-HCT following myeloablative conditioning. Pulmonary disease, moderate to severe hepatic comorbidity, cardiac disease of any type, and renal dysfunction were associated with increased NRM in multivariable Cox regression models. A Simplified Comorbidity Index (SCI) composed of the 4 comorbidities predictive of NRM, as well as age >60 years, stratified patients into 5 groups with a stepwise increase in NRM. NRM rates ranged from 11.4% to 49.9% by stratum, with adjusted hazard ratios of 1.84, 2.59, 3.57, and 5.38. The SCI was also applicable in an external cohort of 230 patients who underwent allo-HCT with unmanipulated grafts following intermediate-intensity conditioning. The area under the receiver operating characteristic curve (AUC) of the SCI for 1-year NRM was 70.3 and 72.0 over the development and external-validation cohorts, respectively; corresponding AUCs of the Hematopoietic Cell Transplantation–specific Comorbidity Index (HCT-CI) were 61.7 and 65.7. In summary, a small set of comorbidities, aggregated into the SCI, is highly predictive of NRM. The new index stratifies patients into distinct risk groups, was validated in an external cohort, and provides higher discrimination than does the HCT-CI.

A practical guide to chimerism analysis: Review of the literature and testing practices worldwide

BACKGROUND AND PURPOSE

Currently there are no widely accepted guidelines for chimerism analysis testing in hematopoietic cell transplantation (HCT) patients. The objective of this review is to provide a practical guide to address key aspects of performing and utilizing chimerism testing results. In developing this guide, we conducted a survey of testing practices among laboratories that are accredited for performing engraftment monitoring/chimerism analysis by either the American Society for Histocompatibility & Immunogenetics (ASHI) and/or the European Federation of Immunogenetics (EFI). We interpreted the survey results in the light of pertinent literature as well as the experience in the laboratories of the authors.

RECENT DEVELOPMENTS

In recent years there has been significant advances in high throughput molecular methods such as next generation sequencing (NGS) as well as growing access to these technologies in histocompatibility and immunogenetics laboratories. These methods have the potential to improve the performance of chimerism testing in terms of sensitivity, availability of informative genetic markers that distinguish donors from recipients as well as cost.

SUMMARY

The results of the survey revealed a great deal of heterogeneity in chimerism testing practices among participating laboratories. The most consistent response indicated monitoring of engraftment within the first 30 days. These responses are reflective of published literature. Additional clinical indications included early detection of impending relapse as well as identification of cases of HLA-loss relapse.

The post-transplant scoring system (PTSS) is associated with outcomes in patients with MDS after CD34+selected allogeneic stem cell transplant

The post-transplant scoring system (PTSS), developed by the Francophone Society of Bone Marrow Transplantation and Cellular Therapy, is based on three independent post-transplant risk factors: grade of acute graft-versus-host disease, lack of platelet recovery before day 100, and relapse before day 100; discriminating low- (0), intermediate- (1–3), and high-risk (4–8) patients. We investigated the prognostic value of the PTSS in a cohort of patients with MDS who underwent myeloablative CD34-selected TCD transplants. From 2008 to 2018, 109 patients underwent a first TCD-HCT for MDS at our center. We used Cox proportional hazards models and different landmark analyses to evaluate the association of categorized PTSS score risk groups with overall survival (OS). Patients with an intermediate/ high risk PTSS score had decreased OS at day 180 (univariate HR 3.25 [95% CI 1.60, 6.60], p = 0.001) and at day 365 (univariate HR 5.42 [95% CI 2.21, 13.3], p < 0.001) compared to low risk PTSS scores. This association remained significant after adjusting for HCT-CI. PTSS score calculated at day 100 was not associated with OS, even after adjusting for HCT-CI subgroups. In summary, the PTSS predicted survival at day 180 and day 365 in recipients of T-cell-depleted allografts for myelodysplastic syndrome.

Universal Engraftment after Allogeneic Hematopoietic Cell Transplantation Using Cryopreserved CD34-Selected Grafts

As a result of the COVID-19 pandemic, most centers performing allogeneic hematopoietic cell transplantation (allo-HCT) have switched to the use of cryopreserved grafts. Previous investigators have suggested that cryopreserved allografts may heighten risk of nonengraftment. To date, no study has investigated the effect of cryopreservation of CD34-selected hematopoietic progenitor cells (CD34⁺ HPCs) used as the sole graft source. In this study, we sought to evaluate outcomes after unrelated donor or matched sibling allo-HCT with cryopreserved CD34⁺ HPCs. This was a single-center analysis of adult patients with hematologic malignancies who underwent allo-HCT with cryopreserved CD34-selected allo-HCT grafts between January 2010 and June 2017. All patients received ablative conditioning and antirejection prophylaxis with rabbit antithymocyte globulin. G-CSF-mobilized leukapheresis products underwent CD34 selection using the CliniMACS Reagent System. Cells were then cryopreserved in DMSO (final concentration 7.5%) to -90 °C using a controlled-rate freezing system before being transferred to vapor-phase liquid nitrogen storage. In internal validation, this method has shown 92% mean CD34⁺ cell viability and 99.7% mean CD34⁺ cell recovery. Engraftment was defined as the first of 3 consecutive days of an absolute neutrophil count of ≥0.5. Platelet recovery was recorded as the first of 7 consecutive days with a platelet count ≥20 K/μL without transfusion. Kaplan-Meier methodology was used to estimate overall survival (OS) and relapse-free survival (RFS), and cumulative incidence functions were used to estimate rates of relapse, nonrelapse mortality (NRM), and acute graft-versus-host disease (GVHD). A total of 64 patients received a cryopreserved CD34-selected graft. The median CD34⁺ cell count before cryopreservation was 6.6 × 10⁶/kg (range, 1.4 to 16.1 × 10⁶/kg), and the median CD3⁺ cell count was 2.0 × 10³/kg (range, 0 to 21.1 × 10⁶/kg). All patients were engrafted, at a median of 11 days post-HCT (range, 8 to 14 days). One patient had poor graft function in the setting of cytomegalovirus viremia, necessitating a CD34-selected boost on day +57. The median time to platelet recovery was 16 days (range, 13 to 99 days). The estimated 2-year OS was 70% (95% confidence interval [CI], 58% to 83%) with cryopreserved grafts versus 62% (95% CI, 57% to 67%) with fresh grafts (hazard ratio [HR], 0.86; 95% CI, 0.54 to 1.35; P = .5). The estimated 2-year RFS in the 2 groups was 59% (95% CI, 48% to 74%) versus 56% (95% CI, 51% to 61%; HR, 1.01; 95% CI, 0.68 to 1.51; P > .9). The cumulative incidence of relapse at 2 years was 29% (95% CI, 17% to 41%) versus 23% (95% CI, 19% to 27%; P = .16), and the cumulative incidence of NRM at 2 years was 17% (95% CI, 9% to 28%) versus 23% (95% CI, 19% to 28%; P = .24). The cumulative incidence of grade II-IV acute GVHD by day +100 was 16% with cryopreserved grafts (95% CI, 8% to 26%) and 16% (95% CI, 13% to 20%; P = .97) with fresh grafts. Moderate to severe chronic GVHD by day +365 occurred in only 1 recipient of a cryopreserved graft (2%). Our data show that in patients with hematologic malignancies who received cryopreserved allogeneic CD34⁺ HPCs, engraftment, GVHD, and survival outcomes were consistent with those seen in recipients of fresh allogeneic CD34⁺ HPC grafts at our center. Our laboratory validation and clinical experience demonstrate the safety of our cryopreservation procedure for CD34-selected allografts.

Combining the Disease Risk Index and Hematopoietic Cell Transplant Co-Morbidity Index provides a comprehensive prognostic model for CD34+-selected allogeneic transplantation

T cell depletion by CD34⁺ cell selection of hematopoietic stem cell allografts ex vivo reduces the incidence and severity of GvHD, without increased risk of relapse in patients with acute leukemia in remission or MDS. The optimal candidate for CD34⁺-selected HCT remains unknown, however.

OBJECTIVE

To determine outcomes based on both disease- and patient-specific factors, we evaluated a prognostic model combining the Disease Risk Index (DRI) and Hematopoietic Cell Transplantation Comorbidity Index (HCT-CI), an approach recently shown to predicted overall survival in a broad population of allograft recipients (1).

METHODS

This was a retrospective analysis of 506 adult recipients of first allogeneic HCT with CD34+ selected PBSCs from 7/8- or 8/8-matched donors for AML (n = 290), ALL (n = 72), or MDS (n = 144). The Kaplan-Meier method estimated OS and RFS. The cumulative incidence method for competing risks estimated relapse and non-relapse mortality (NRM). We evaluated the univariate association between variables of interest and OS and RFS using the log-rank test. Cox regression models assessed the adjusted effect of covariates on OS/RFS.

RESULTS

Stratification of patients based on a composite of DRI (low/intermediate vs. high/very high) and HCT-CI (0-2 vs. ≥ 3) revealed differences in OS and RFS between the 4 groups. Compared with reference groups of patients with low/intermediate DRI and low or high HCT-CI, those with high DRI had a greater risk of death (HR 2.30; 95% CI 1.39, 3.81) and relapse or death (HR 2.50; 95% CI 1.55, 4.05) than patients with any HCT-CI but low/intermediate DRI (HR death 1.80; 95% CI 1.34, 2.43; HR relapse/death 1.68; 95% CI 1.26, 2.24).

CONCLUSIONS AND CLINICAL IMPLICATIONS

A model combining DRI and HCT-CI predicted survival after CD34⁺ cell-selected HCT. Application of this combined model to other cohorts, both in retrospective analyses and prospective trials, will enhance clinical decision making and patient selection for different transplant approaches.

DATA AVAILABILITY STATEMENT

The data that support the findings of this study are available on request from the corresponding author, C Cho. In order to protect the privacy of research participants, the data are not publicly available.

Checkpoint inhibitors in AML: are we there yet?

Immunotherapy is distinct from traditional chemotherapy in that it acts on immune cells rather than cancer cells themselves. Monoclonal antibodies targeting immune checkpoints on T cells - CTLA-4 and PD-1 - and PD-L1 on the cells of immune microenvironment are now approved for clinical use in several solid tumors and hematological malignancies. This article provides a general overview of the use of checkpoint inhibitors in hematologic malignancies with a special focus in acute myeloid leukemia.

Ex Vivo T Cell-Depleted Hematopoietic Stem Cell Transplantation for Adult Patients with Acute Myelogenous Leukemia in First and Second Remission: Long-Term Disease-Free Survival with a Significantly Reduced Risk of Graft-versus-Host Disease

Large series of patients with acute myelogenous leukemia (AML) after ex vivo T cell-depleted (TCD) allogeneic hematopoietic stem cell transplantation (allo-HSCT) have not been reported previously. We retrospectively analyzed the outcomes of 266 patients (median age, 54 years) with AML who received CD34-selected TCD allo-HSCTs while in first (75%) or second (25%) complete remission (CR1/CR2) at a single institution. The conditioning regimens were all myeloablative, and no additional graft-versus-host disease (GVHD) prophylaxis was given. The cumulative incidences of grade II-IV and grade III-IV acute GVHD at 180 days were 14% (95% confidence interval [CI], 10% to 18%) and 3% (95% CI, 1% to 5%), respectively. The cumulative incidence of chronic GVHD at 3 years was 3% (95% CI, 1% to 6%). The 3-year cumulative incidence of nonrelapse mortality was 21% (95% CI, 16% to 26%) and that of relapse was 21% (95% CI, 17% to 27%). Overall survival (OS) and disease-free survival (DFS) at 1, 3, and 5 years were 75%, 61%, and 56% and 68%, 57%, and 53%, respectively. There were no significant differences in OS, DFS, and relapse rates for patients who underwent transplantation in CR1 and those who did so in CR2. However, patients with high-risk cytogenetics at diagnosis had significantly poorer outcomes. The OS and DFS rates compare favorably with those for unmodified allo-HSCT, but with considerably lower rates of GVHD.

Expanding Therapeutic Opportunities for Hematopoietic Stem Cell Transplantation: T Cell Depletion as a Model for the Targeted Allograft

Allogeneic hematopoietic cell transplantation is a fundamental part of the treatment of hematologic malignancies and marrow failure syndromes, but complications including graft-versus-host disease, prolonged immune deficiency and infection, and organ toxicities, as well as relapse, remain obstacles to improved overall survival. As the cellular characteristics of the allograft can exert significant impact on outcomes, the development of more strategically designed grafts represents a rich area for therapeutic intervention. We describe the use of ex vivo T cell–depleted grafts as a model for the targeted graft and review evolving knowledge and approaches for further refinement of allografts to improve patient outcomes.

Immune Cytopenias after Ex Vivo CD34+-Selected Allogeneic Hematopoietic Cell Transplantation

Immune-mediated cytopenias (ICs), such as immune thrombocytopenia and immune hemolytic anemia, are among the adverse events after allogeneic hematopoietic cell transplantation (allo-HCT). Previous reports suggest that in vivo T cell depletion may increase the incidence of IC after allo-HCT. We evaluated whether a strategy that reduces functional donor T cells via ex vivo CD34⁺-selection associates with the development of IC in a cohort of 408 patients who underwent allo-HCT for hematologic malignancy. The cumulative incidence of IC at 6, 12, and 36 months after the 30-day landmark post-HCT was 3.4%, 4.9%, and 5.8%, respectively. Among 23 patients who developed IC, 7 died of relapse-related mortality and 4 of nonrelapse mortality. A median 2 types of treatment (range, 1 to 5) was required to resolve IC, and there was considerable heterogeneity in the therapies used. In univariable analyses, a hematologic malignancy Disease Risk Index (DRI) score of 3 was significantly associated with an increased risk of IC compared with a DRI of 1 or 2 (hazard ratio [HR], 4.12; P = .003), and IC (HR, 2.4; P = .03) was associated with increased risk of relapse. In a multivariable analysis that included DRI, IC remained significantly associated with increased risk of relapse (HR, 2.4; P = .03). Our findings show that IC events occur with relatively similar frequency in patients after ex vivo CD34⁺-selected allo-HCT compared with unmodified allo-HCT, suggesting that reduced donor T cell immunity is not causative of IC. Moreover, we noted a possible link between its development and/or treatment and increased risk of relapse.

Advances in Ex Vivo T Cell Depletion - Where Do We Stand?

Graft-versus-host (GVHD) is an important cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). As donor T cells are recognized as key drivers of GVHD, some approaches to prevent GVHD have focused on T cell depletion of the allograft. In this review we summarize methods and outcomes of ex vivo T cell depleted (TCD) HCT with a focus on CD34+ selection. This platform is efficacious in preventing acute and chronic GVHD across a wide range of hematologic malignancies, and with the exception of chronic myeloid leukemia, is not associated with adverse relapse or survival outcomes compared to conventional GVHD prophylaxis platforms. In retrospective comparisons recipients of CD34+ selected HCT have higher rates of GVHD-free relapse-free survival (GRFS) than conventional HCT counterparts. Although CD34+ selected allografts require myeloablative and antithymocyte-globulin based conditioning to support engraftment, abrogation of calcineurin inhibitors and methotrexate in this approach reduces its toxicity such that it can be considered in select older and more comorbid patients who could benefit from ablative HCT. A trial comparing GVHD prophylaxis regimens (BMT CTN 1301, NCT02345850) has completed accrual and will be the first to compare CD34+ selected HCT with conventional HCT in a randomized prospective setting. Its findings have potential to establish CD34+ selected HCT as a new standard-of-care platform for GVHD prevention.

Ex vivo and in vivo T cell-depleted allogeneic stem cell transplantation in patients with acute myeloid leukemia in first complete remission resulted in similar overall survival: on behalf of the ALWP of the EBMT and the MSKCC

Background

Graft-versus-host disease (GVHD) is one of the leading causes of non-relapse mortality and morbidity after allogeneic hematopoietic stem cell transplantation (allo-HCT).

Methods

We evaluated the outcomes of two well-established strategies used for GVHD prevention: in vivo T cell depletion using antithymocyte globulin (ATG) and ex vivo T cell depletion using a CD34-selected (CD34+) graft. A total of 525 adult patients (363 ATG, 162 CD34+) with intermediate or high-risk cytogenetics acute myeloid leukemia (AML) in first complete remission (CR1) were included. Patients underwent myeloablative allo-HCT using matched related or unrelated donors.

Results

Two-year overall survival estimate was 69.9% (95% CI, 58.5–69.4) in the ATG group and 67.6% (95% CI, 60.3–74.9) in the CD34+ group (p = 0.31). The cumulative incidence of grade II–IV acute GVHD and chronic GVHD was higher in the ATG cohort [HR 2.0 (95% CI 1.1–3.7), p = 0.02; HR 15.1 (95% CI 5.3–42.2), p < 0.0001]. Parameters associated with a lower GVHD-free relapse-free survival (GRFS) were ATG [HR 1.6 (95% CI 1.1–2.2), p = 0.006], adverse cytogenetic [HR 1.7 (95% CI 1.3–2.2), p = 0.0004], and the use of an unrelated donor [HR 1.4 (95% CI 1.0–1.9), p = 0.02]. There were no statistical differences between ATG and CD34+ in terms of relapse [HR 1.52 (95% CI 0.96–2.42), p = 0.07], non-relapse mortality [HR 0.96 (95% CI 0.54–1.74), p = 0.90], overall survival [HR 1.43 (95% CI 0.97–2.11), p = 0.07], and leukemia-free survival [HR 1.25 (95% CI 0.88–1.78), p = 0.21]. Significantly, more deaths related to infection occurred in the CD34+ group (16/52 vs. 19/112, p = 0.04).

Conclusions

These data suggest that both ex vivo CD34-selected and in vivo ATG T cell depletion are associated with a rather high OS and should be compared in a prospective randomized trial.

Electronic supplementary material

The online version of this article (10.1186/s13045-018-0668-3) contains supplementary material, which is available to authorized users.

Early Fluid Overload Is Associated with an Increased Risk of Nonrelapse Mortality after Ex Vivo CD34-Selected Allogeneic Hematopoietic Cell Transplantation

In a recently published and validated definition of fluid overload (FO), grade ≥ 2 FO was significantly associated with an increased risk of nonrelapse mortality (NRM) after unmodified and haploidentical allogeneic hematopoietic cell transplantation (allo-HCT) using calcineurin inhibitor (CNI)-based graft-versus-host disease (GVHD) prophylaxis. We evaluated the effect of FO on outcomes in 169 patients undergoing myeloablative-conditioned ex vivo CD34⁺ selected allo-HCT using the same grading scale. Thirty patients (17.8%) had grade ≥ 2 FO within the 30 days after ex vivo CD34⁺ selected allo-HCT with a median onset at day 11 (range, -8 to 28). Age ≥ 55 years (odds ratio, 3.43; P = .005) and chemotherapy-based conditioning (odds ratio, 3.89; P = .007) were associated with an increased risk of grade ≥ 2 FO. Patients with early grade ≥ 2 FO had a significantly higher NRM when compared with patients with grade < 2 FO (24.1% versus 3.6% at day 100, P = .01). The HCT-specific comorbidity index (HCT-CI) ≥ 3, FEV₁ < 80, adjusted DL_co < 80, and HLA mismatch were associated with an increased risk of NRM, whereas total body irradiation-based conditioning was associated with a reduced risk of NRM. In a multivariate analysis grade ≥ 2 FO was associated with increased NRM after adjusting for HCT-CI and HLA match (hazard ratio, 2.3; P = .014). There was a trend toward inferior relapse-free survival in patients with grade ≥ 2 FO compared with patients with grade < 2 FO, 62% versus 72% at 1 year (P = .07), and a trend toward inferior overall survival, 69% versus 79% at 1 year (P = 0.06), respectively. Our findings show that FO should be routinely assessed to identify patients at risk for NRM. Despite a CNI-free allo-HCT platform, regimen-related tissue and endothelial injury leads to FO in susceptible patients. FO is a highly relevant post-HCT toxicity that requires further inquiry.

Defining success with cellular therapeutics: the current landscape for clinical end point and toxicity analysis

Cellular therapies play a major and expanding role in the treatment of hematologic diseases. For each of these therapies, a narrow therapeutic window exists, where efficacy is maximized and toxicities minimized. This review focuses on one of the most established cellular therapies, hematopoietic stem cell transplant, and one of the newest cellular therapies, chimeric antigen receptor-T cells. In this review, I will discuss the current state of the field for clinical end point analysis with each of these therapeutics, including their critical toxicities, and focus on the major elements of success for each of these complex treatments for hematologic disease.

Selected biological issues affecting relapse after stem cell transplantation: role of T-cell impairment, NK cells and intrinsic tumor resistance

The graft vs. leukemia (GvL) effect as a method of preventing relapse is well described after allogeneic hematopoietic cell transplantation (HCT), but the mechanisms to this effect and how tumor sometimes develops resistance to GvL are just beginning to be understood. This article reviews and expands upon data presented at the Third International Workshop on Biology, Prevention and Treatment of Relapse after Stem Cell Transplantation held in Hamburg, Germany, in November 2016. We first discuss in detail the role that T-cell impairment early after HCT plays in relapse by looking at data from T cell-depleted approaches as well as the clear role that early T-cell recovery has shown in improving outcomes. We then review key findings regarding the role of specific KIR donor/recipient pairings that contribute to relapse prevention after HCT for several tumor types. Finally, we discuss a unique mouse model following the development of tumor resistance to GvL. Detailed molecular characterization of events marking the development of tumor resistance to the immunotherapy of GvL may help in developing future strategies to overcome immune escape.

Allogeneic Stem Cell Transplantation for Advanced Myelodysplastic Syndrome: Comparison of Outcomes between CD34+ Selected and Unmodified Hematopoietic Stem Cell Transplantation

In this study, we compared transplantation outcomes of allogeneic hematopoietic stem cell transplantation (HSCT) in patients with advanced myelodysplastic syndrome (MDS) who received a CD34⁺ cell-selected and those who received an unmodified allograft. This analysis initially included 181 patients, 60 who received a CD34⁺ cell-selected transplant and 121 who received an unmodified transplant. Owing to significant differences in disease characteristics, the analysis was limited to patients with <10% blasts before HSCT (n = 145). Two groups were defined: low risk, with low- and intermediate-risk cytogenetics (CD34⁺, n = 39; unmodified, n = 46), and high risk: poor and very poor risk cytogenetics (CD34⁺, n = 19; unmodified, n = 41). In the low-risk group, the incidence of grade II-IV acute graft-versus-host disease (aGVHD) at 1 year post-transplantation was 18% in the CD34⁺ subgroup versus 41.3% in the unmodified subgroup (P = .015). There were no differences between the subgroups in the incidence of grade III-IV aGVHD. The incidence of chronic graft-versus-host disease (cGVHD) at 3 years in the 2 subgroups was 5.3% and 56%, respectively (P < .001). At 3 years post-transplantation, relapse, overall survival (OS), and relapse-free survival (RFS) were similar in the CD34⁺ and unmodified subgroups: 8.1% versus 19.4% (P = .187), 58.5% versus 53.7% (P = .51), and 59.5% versus 52.4% (P = .448). However, the composite outcome combining extensive cGVHD-free status and relapse-free status (CRFS) at 3 years was 59.5% in the CD34⁺ group versus 19.2% in the unmodified group (P < .001). In the high-risk group, grade II-IV aGVHD at 1 year was 31.6% in the CD34⁺ subgroup versus 24.4% in the unmodified subgroup (P = .752). There were no differences between the subgroups in the incidence of grade III-IV aGVHD. The incidence of cGVHD at 3 years in the 2 subgroups was 0% versus 27.6% (P = .013). At 3 years post-transplantation, relapse, OS, RFS, and CRFS in the 2 subgroups were 31.6% versus 69.3% (P = .007), 35.5% versus 14.5% (P = .068), 31.6% versus 10.7% (P = .045), and 31.6% versus 6.1% (P = .001), respectively. Cytogenetic abnormalities at diagnosis and transplant type had significant univariate associations with RFS in the high-risk cohort. Only cytogenetics (P = .03) remained associated with this outcome in a multivariate model. OS was similar in the 2 transplant groups; however, CRFS was superior in the CD34⁺ cell-selected transplant group.

CD34+ Cell Selection versus Reduced-Intensity Conditioning and Unmodified Grafts for Allogeneic Hematopoietic Cell Transplantation in Patients Age >50 Years with Acute Myelogenous Leukemia and Myelodysplastic Syndrome

Reduced-intensity conditioning (RIC) and T cell depletion (TCD) through CD34⁺ cell selection without the use of post-transplantation immunosuppression are 2 strategies used to reduce nonrelapse mortality (NRM) in older patients after allogeneic hematopoietic cell transplantation (allo-HCT). To compare the efficacy of the RIC and TCD approaches, we evaluated the outcomes of patients age >50 years with acute myelogenous leukemia (AML) and myelodysplastic syndrome (MDS) who underwent allo-HCT from an HLA-matched donor with one of these strategies. Baseline characteristics were comparable in the patients receiving TCD (n = 204) and those receiving RIC (n = 151), except for a higher proportion of unrelated donors (68% versus 40%; P < .001) and a higher comorbidity burden (Hematopoietic Cell Transplantation Comorbidity Index [HCT-CI] ≥3: 51% versus 38%; P < .001) in the TCD cohort. Analysis of outcomes at 3 years showed a higher chronic graft-versus-host disease (GVHD)/relapse-free survival (CRFS) (51% versus 7%; P < .001), lower incidences of grade II-IV acute GVHD (18% versus 46% at day +180) and chronic GVHD (6% versus 55% at 3 years; P < .001), and a lower incidence of relapse (19% versus 33% at 3 years; P = .001) in the TCD group compared with the RIC group. Relapse-free survival (RFS), overall survival (OS), and NRM were similar in the 2 groups. Combining transplantation approach (RIC versus TCD) and comorbidity burden (HCT-CI 0-2 versus ≥3), patients with an HCT-CI score of 0-2 seemed to benefit from the TCD approach. In conclusion, in this retrospective study, the use of a CD34⁺ cell-selected graft and a myeloablative conditioning regimen was associated with higher CRFS and similar RFS and OS compared with unmodified allo-RIC in patients age >50 years with AML and MDS.

Long-term prognosis for 1-year relapse-free survivors of CD34+ cell-selected allogeneic hematopoietic stem cell transplantation: a landmark analysis

CD34 selection significantly improves GVHD-free survival in allogeneic hematopoietic cell transplantation (allo-HSCT). Specific information regarding long-term prognosis and risk factors for late mortality after CD34-selected allo-HSCT is lacking, however. We conducted a single-center landmark analysis in 276 patients alive without relapse 1 year after CD34-selected allo-HSCT for AML (n=164), ALL (n=33), or MDS (n=79). At 5 years' follow-up after the 1-year landmark (range 0.03-13 years), estimated RFS was 73% and OS 76%. The 5-year cumulative incidence of relapse and NRM were 11% and 16%, respectively. In multivariate analysis, HCT-CI score ≥ 3 correlated with marginally worse RFS (HR 1.78, 95% CI 0.97-3.28, p=0.06) and significantly worse OS (HR 2.53, 95% CI 1.26-5.08, p=0.004). Despite only 24% of patients with acute GVHD within 1 year, this also significantly correlated with worse RFS and OS, with increasing grades of acute GVHD associating with increasingly poorer survival on multivariate analysis (p<0.0001). Of 63 deaths after the landmark, GVHD accounted for 27% of deaths and was the most common cause of late mortality, followed by relapse and infection. While prognosis is excellent for patients alive without relapse 1 year after CD34-selected allo-HSCT, risks of late relapse and NRM persist, particularly due to GVHD.

T Cell Depletion as an Alternative Approach for Patients 55 Years or Older Undergoing Allogeneic Stem Cell Transplantation as Curative Therapy for Hematologic Malignancies

T cell-depleted (TCD) allogeneic hematopoietic stem cell transplantation (HSCT) is curative treatment for hematologic malignancies in adults, shown to reduce graft-versus-host disease (GVHD) without increased relapse. We retrospectively reviewed a single-center, 11-year experience of 214 patients aged ≥ 55 years to determine tolerability and efficacy in the older adult. Most patients (70%) had myeloid diseases, and most acute leukemias were in remission. Median age was 61 years, with related and unrelated donors ≥8/10 HLA matched. Hematopoietic cell transplantation-specific comorbidity index scores were intermediate and high for 84%. Conditioning regimens were all myeloablative. Grafts were peripheral blood stem cells (97%) containing CD3 dose ≤103-4/kg body weight, without pharmacologic GVHD prophylaxis. With median follow-up of 70 months among survivors, Kaplan-Meier estimates of overall and relapse-free survival were 44% and 41%, respectively (4 years). Cumulative incidence of nonrelapse mortality at day +100 was only 10%. Incidence of GVHD for acute (grades II to IV) was 9% at day +100 and for chronic was 7% at 2 and 4 years (8 extensive, 1 overlap). Median Karnofsky performance status for patients > 2 years post-transplant was 90%. As 1 of the largest reports for patients ≥2 aged ≥55 years receiving TCD HSCTs, it demonstrates curative therapy with minimal GVHD, similar to that observed in a younger population.

Impact of Toxicity on Survival for Older Adult Patients after CD34+ Selected Allogeneic Hematopoietic Stem Cell Transplantation

Ex vivo CD34⁺ selection before allogeneic hematopoietic stem cell transplantation (allo-HCT) reduces graft-versus-host disease without increasing relapse but usually requires myeloablative conditioning. We aimed to identify toxicity patterns in older patients and the association with overall survival (OS) and nonrelapse mortality (NRM). We conducted a retrospective analysis of 200 patients who underwent CD34⁺ selection allo-HCT using the ClinicMACS® system between 2006 and 2012. All grade 3 to 5 toxicities by CTCAE v4.0 were collected. Eighty patients aged ≥ 60 years with a median age of 64 (range, 60 to 73) were compared with 120 patients aged < 60 years. Median follow-up in survivors was 48.2 months. OS and NRM were similar between ages ≥ 60 and <60, with 1-year OS 70% versus 78% (P = .07) and 1-year NRM 23% versus 13% (P = .38), respectively. In patients aged ≥ 60 the most common toxicities by day 100 were metabolic, with a cumulative incidence of 88% (95% CI, 78% to 93%), infectious 84% (95% CI, 73% to 90%), hematologic 80% (95% CI, 69% to 87%), oral/gastrointestinal (GI) 48% (95% CI, 36% to 58%), cardiovascular (CV) 35% (95% CI, 25% to 46%), and hepatic 25% (95% CI, 16% to 35%). Patients aged ≥ 60 had a higher risk of neurologic (HR, 2.63 [95% CI, 1.45 to 4.78]; P = .001) and CV (HR, 1.65 [95% CI, 1.04 to 2.63]; P = .03) toxicities but a lower risk of oral/GI (HR, .58 [95% CI, .41 to .83]; P = .003) compared with those aged < 60. CV, hepatic, neurologic, pulmonary, and renal toxicities remained independent risk factors for the risk of death and NRM in separate multivariate models adjusting for age and hematopoietic cell transplantation-specific comorbidity index. Overall, the toxicity of a more intense regimen is potentially balanced by the absence of toxicity related to methotrexate and calcineurin inhibitors in older patients. Prospective study of toxicities after allo-HCT in older patients is essential.

Effects of Late Toxicities on Outcomes in Long-Term Survivors of Ex-Vivo CD34+-Selected Allogeneic Hematopoietic Cell Transplantation

The late adverse events in long-term survivors after myeloablative-conditioned allogeneic hematopoietic cell transplantation (HCT) with ex vivo CD34⁺ cell selection are not well characterized. Using the National Cancer Institute's Common Terminology Criteria for Adverse Events, version 4.0, we assessed all grade ≥3 toxicities from the start of conditioning to the date of death, relapse, or last contact in 131 patients who survived >1 year post-HCT, identifying 285 individual toxicities among 17 organ-based toxicity groups. Pretransplantation absolute lymphocyte count >.5 K/µL and serum albumin >4.0 g/dL were associated with a reduced risk of toxicities, death, and nonrelapse mortality (NRM), whereas serum ferritin >1000 ng/mL was associated with an increased risk of toxicities and NRM after 1 year. An HCT Comorbidity Index (HCT-CI) score ≥3 was associated with an increased risk of all-cause death and NRM, but was not associated with a specific increased toxicity risk after 1 year. Patients who incurred more than the median number of toxicities (n = 7) among all patients within the first year subsequently had an increased risk of hematologic, infectious, and metabolic toxicities, as well as an increased risk of NRM and inferior 4-year overall survival (OS) (67% versus 86%; P = .003) after the 1-year landmark. The development of grade II-IV acute graft-versus-host disease (GVHD) within the first year was associated with incurring >7 toxicities within the first year (P = .016), and also with an increased risk of all-cause death and NRM after 1 year. In multivariate models, cardiovascular, hematologic, hepatic, infectious, metabolic, neurologic, and pulmonary toxicities incurred after 1 year were independently associated with increased risk of death and NRM when adjusting for both HCT-CI and grade II-IV acute GVHD within the first year. One-year survivors of ex vivo CD34⁺ selection had a favorable 4-year OS of 77%, although the development of grade ≥3 toxicities after the first year was associated with poorer outcomes, emphasizing the fundamental importance of improving survivorship efforts that may improve long-term toxicity burden and outcome.

In-vivo or ex-vivo T cell depletion or both to prevent graft-versus-host disease after hematopoietic stem cell transplantation

INTRODUCTION

Hematopoietic stem cell transplantation (HSCT) represents a widely accepted therapeutic strategy for the treatment of hematologic disorders which are otherwise considered incurable. Alloreactive T cells infused with the stem cell inoculum may generate graft-versus-host disease (GVHD) representing one the most relevant obstacles to the successful outcome of patients receiving allogeneic HSCT. Areas covered: In this review, the authors provide an overview of the most recent approaches of T-cell depletion (TCD) including ex-vivo αβ+ TCD and in-vivo TCD with anti-thymocyte globulin (ATG). Expert opinion: Ex vivo depletion of donor T-cells prevents both acute and chronic GVHD without the need for any additional posttransplant immunological prophylaxis either in haploidentical HSCT and HLA matched transplants. Three prospective trials evaluating the efficacy of ATG in matched unrelated donor transplant recipients demonstrated that ATG reduces the incidence of both acute and chronic GVHD without a significant increase of relapse rate, and similar results have been reported in the setting of blood stem cell grafts from matched sibling donors.

The Impact of Toxicities on First-Year Outcomes after Ex Vivo CD34+-Selected Allogeneic Hematopoietic Cell Transplantation in Adults with Hematologic Malignancies

Factors that impact first-year morbidity and mortality in adults undergoing myeloablative allogeneic hematopoietic cell transplantation with ex vivo CD34⁺ selection have not been previously reported. We assessed all toxicities ≥ grade 3 from the start of conditioning to date of death, relapse, or last contact in 200 patients during the first year after transplantation, identifying 1885 individual toxicities among 17 organ-based toxicity groups. The most prevalent toxicities in the first year were of infectious, metabolic, hematologic, oral/gastrointestinal, hepatic, cardiac, and pulmonary etiologies. Renal complications were minimal. Grades II to IV and III and IV acute GVHD at day 100 were 11.5% and 3%, respectively. In separate multivariate models, cardiovascular, hematologic, hepatic, neurologic, pulmonary, and renal toxicities negatively impacted nonrelapse mortality (NRM) and overall survival during the first year. A higher-than-targeted busulfan level, patient cytomegalovirus seropositivity, and an Hematopoietic Cell Transplantation-Specific Comorbidity Index of ≥3 were associated with increased risk of NRM and all-cause death. Ex vivo CD34⁺ selection had a favorable 1-year OS of 75% and NRM of 17% and a low incidence of sinusoidal obstruction syndrome. These data establish a benchmark to focus efforts in reducing toxicity burden while improving patient outcomes.

A Chemotherapy-Only Regimen of Busulfan, Melphalan, and Fludarabine, and Rabbit Antithymocyte Globulin Followed by Allogeneic T-Cell Depleted Hematopoietic Stem Cell Transplantations for the Treatment of Myeloid Malignancies

We sought to develop a myeloablative chemotherapeutic regimen to secure consistent engraftment of T-cell depleted (TCD) hematopoietic stem cell transplantations (HSCT) without the need for total body irradiation, thereby reducing toxicity while maintaining low rates of graft-versus-host disease (GVHD) and without increasing relapse. We investigated the myeloablative combination of busulfan (Bu) and melphalan (Mel), with the immunosuppressive agents fludarabine (Flu) and rabbit antithymocyte globulin (r-ATG) as cytoreduction before a TCD HSCT. No post-transplantation immunosuppression was administered. Between April 2001 and May 2008, 102 patients (median age, 55 years) with a diagnosis of primary or secondary myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML) underwent cytoreduction with Bu/Mel/Flu, followed by TCD grafts. TCD was accomplished by CD34⁺-selection followed by E-rosette depletion for peripheral blood stem cell grafts and, for bone marrow grafts, by soybean agglutination followed by E-rosette depletion. Donors included matched and mismatched, related and unrelated donors. Risk stratification was by American Society for Blood and Marrow Transplantation risk categorization for patients with primary disease. For patients with secondary/treatment-related MDS/AML, those in complete remission (CR) 1 or with refractory anemia were classified as intermediate risk, and all other patients were considered high risk. Neutrophil engraftment occurred at a median of 11 days in 100 of 101 evaluable patients. The cumulative incidences of grades II to IV acute and chronic GVHD at 1 year were 8.8% and 5.9%, respectively. Overall- and disease-free survival (DFS) rates at 5 years were 50.0% and 46.1%, respectively, and the cumulative incidences of relapse and treatment-related mortality were 23.5% and 28.4%, respectively. Stratification by risk group demonstrated superior DFS for low-risk patients (61.5% at 5 years) compared with intermediate- or high-risk (34.2% and 40.0%, respectively, P = .021). For patients with AML, those in CR1 had superior 5-year DFS compared with those in ≥CR2 (60% and 30.6%, respectively, P = .01), without a significant difference in incidence of relapse (17.1% and 30.6%, respectively, P = .209). There were no differences in DFS for other patient, donor, or disease characteristics. In summary, cytoreduction with Bu/Mel/Flu and r-ATG secured consistent engraftment of TCD transplantations. The incidences of acute/chronic GVHD and disease relapse were low, with favorable outcomes in this patient population with high-risk myeloid malignancies.

Ex vivo T-cell-depleted allogeneic stem cell transplantation for hematologic malignancies: The search for an optimum transplant T-cell dose and T-cell add-back strategy

BACKGROUND

T-cell depletion (TCD) of allogeneic stem cell transplants (SCT) can reduce graft-versus-host disease but may negatively affect transplant outcome by delaying immune recovery. To optimize TCD in HLA-matched siblings with hematologic malignancies, we explored varying the transplant CD3+ T-cell dose between 2 and 50 × 10⁴/kg (corresponding to 3-4 log depletion) and studied the impact of 0-6 × 10⁷/kg CD3+ donor lymphocyte infusion (DLI) "add-back" on immune recovery post-SCT.

METHODS

Two hundred seventeen consecutive patients (age range, 10-75 years) with hematologic malignancy (excluding chronic leukemias) underwent ex vivo TCD SCT from HLA-identical sibling donors from 1994-2015. Ninety-four patients had standard-risk disease (first remission acute leukemia [AL] and early stage myelodysplastic syndromes [MDS]) and 123 had high-risk disease (AL beyond first complete remission, advanced MDS or refractory B-cell malignancy).

RESULTS

Median follow-up was 8.5 years. At 20 years post-SCT, overall survival (OS) was 40%, nonrelapse mortality (NRM) was 27% and relapse incidence was 39%. Factors affecting outcome in multivariate analysis were transplantation era, with OS increasing from 38% in the period 1994-2000 to 58% in 2011-2015, disease risk (hazard ratio [HR], 1.68 for high risk) and increasing age (HR, 1.19 per decade). Neither the T-cell dose or the add back of T cells in the first 100 days had any effect on OS, NRM and relapse.

CONCLUSIONS

Outcomes for TCD SCT have greatly improved. However, our data do not support the need to precisely manipulate transplant CD3+ T-cell dose provided at least 3-log depletion is achieved or the use of T-cell add-back. Future improvements for TCD SCT await better strategies to prevent relapse, especially in high-risk recipients.

Ex vivo T-cell depletion in allogeneic hematopoietic stem cell transplant: past, present and future

The most common cause of post-transplant mortality in patients with hematological malignancy is relapse, followed by GvHD, infections, organ toxicity and second malignancy. Immune-mediated complications such as GvHD continue to be challenging, yet amenable to control through manipulation of the T-cell compartment of the donor graft with subsequent immunomodulation after transplant. However, risk of both relapse and infection increase concomitantly with T-cell depletion (TCD) strategies that impair immune recovery. In this review, we discuss the clinical outcome of current and emerging strategies of TCD in allogeneic hematopoietic stem cell transplant that have developed during the modern transplantation era, focusing specifically on ex vivo strategies that target selected T-cell subsets.

Early recovery of T-cell function predicts improved survival after T-cell depleted allogeneic transplant

Infection, relapse, and GVHD can complicate allogeneic hematopoietic stem cell transplantation (allo-HSCT). Although the effect of poor immune recovery on infection risk is well-established, there are limited data on the effect of immune reconstitution on relapse and survival, especially following T-cell depletion (TCD). To characterize the pattern of immune reconstitution in the first year after transplant and its effects on survival and relapse, we performed a retrospective study in 375 recipients of a myeloablative TCD allo-HSCT for hematologic malignancies. We noted that different subsets recover sequentially, CD8 + T cells first, followed by total CD4 + and naïve CD4 + T cells, indicating thymic recovery during the first year after HSCT. In the multivariate model, a fully HLA-matched donor and recovery of T-cell function, assessed by PHA response at 6 months, were the only factors independently associated with OS and EFS. In conclusion, T-cell recovery is an important predictor of outcome after TCD allo-HSCT.

Hematopoietic Cell Transplantation Comorbidity Index Predicts Outcomes in Patients with Acute Myeloid Leukemia and Myelodysplastic Syndromes Receiving CD34+ Selected Grafts for Allogeneic Hematopoietic Cell Transplantation

To evaluate the association between the hematopoietic cell transplantation-comorbidity index (HCT-CI) and the recently developed age-adjusted HCT-CI (HCT-CI/age) and transplant outcomes in the setting of CD34-selected allogeneic HCT, we analyzed a homogeneous population of patients undergoing allogeneic HCT with CD34-selected grafts for acute myeloid leukemia and myelodysplastic syndrome (n = 346). Median HCT-CI and HCT-CI/age scores were 2 (percentile 25 to 75, 1 to 4) and 3 (percentile 25 to 75, 1 to 5), respectively. Higher HCT-CI and HCT-CI/age scores were associated with higher nonrelapse mortality (NRM) and lower overall survival (OS). The HCT-CI distinguished 2 risk groups (0 to 2 versus ≥3), whereas, with the HCT-CI/age, there was a progressive increase in NRM and decrease in OS with increasing scores in all 4 groups (0 versus 1 to 2 versus 3 to 4 versus ≥5). Higher scores in both models were associated with lower chronic graft-versus-host disease relapse-free survival but not with higher relapse. Both models showed a promising predictive accuracy for NRM (c- = .616 for HCT-CI and c- = .647 for HCT-CI/age). In conclusion, the HCT-CI and HCT-CI/age predict transplant outcomes in CD34-selected allo-HCT, including NRM, OS, and chronic graft-versus-host disease relapse-free survival and may be used to select appropriate patients for this approach.

The Total Body Irradiation Schedule Affects Acute Leukemia Relapse After Matched T Cell-Depleted Hematopoietic Stem Cell Transplantation

PURPOSE

We sought to determine whether the total body irradiation (TBI) schedule affected outcome in patients with acute leukemia in complete remission who received T cell-depleted allogeneic hematopoietic stem cell transplantation from HLA identical siblings.

METHODS AND MATERIALS

The study recruited 55 patients (median age, 48 years; age range, 20-66 years; 30 men and 25 women; 34 with acute myeloid leukemia and 21 with acute lymphoid leukemia). Hyperfractionated TBI (HTBI) (1.2 Gy thrice daily for 4 days [for a total dose of 14.4 Gy] from day -12 to day -9) was administered to 29 patients. Single-dose TBI (STBI) (8 Gy, at a median dose rate of 10.7 cGy/min on day -9) was given to 26 patients.

RESULTS

All patients achieved primary, sustained engraftment with full donor-type chimerism. At 10 years, the overall cumulative incidence of transplant-related mortality was 11% (SE, ±0.1%). It was 7% (SE, ±0.2%) after HTBI and 15% (SE, ±0.5%) after STBI (P=.3). The overall cumulative incidence of relapse was 33% (SE, ±0.5). It was 13% (SE, ±0.5%) after HTBI and 46% (SE, ±1%) after STBI (P=.02). The overall probability of disease-free survival (DFS) was 59% (SE, ±7%). It was 67% (SE, ±0.84%) after HTBI and 37% (SE, ±1.4%) after STBI (P=.01). Multivariate analyses showed the TBI schedule was the only risk factor that significantly affected relapse and DFS (P=.01 and P=.03, respectively).

CONCLUSIONS

In patients with acute leukemia, HTBI is more efficacious than STBI in eradicating minimal residual disease after HLA-matched T cell-depleted hematopoietic stem cell transplantation, thus affecting DFS.

Targeting T Cell Bioenergetics by Modulating P-Glycoprotein Selectively Depletes Alloreactive T Cells To Prevent Graft-versus-Host Disease

T lymphocytes play a central role in many human immunologic disorders, including autoimmune and alloimmune diseases. In hematopoietic stem cell transplantation, acute graft-versus-host-disease (GVHD) is caused by an attack on the recipient's tissues from donor allogeneic T cells. Selectively depleting GVHD-causing cells prior to transplant may prevent GVHD. In this study, we evaluated 24 chalcogenorhodamine photosensitizers for their ability to selectively deplete reactive T lymphocytes and identified the photosensitizer 2-Se-Cl, which accumulates in stimulated T cells in proportion to oxidative phosphorylation. The photosensitizer is also a potent stimulator of P-glycoprotein (P-gp). Enhanced P-gp activity promotes the efficient removal of photosensitizer not sequestered in mitochondria and protects resting lymphocytes that are essential for antipathogen and antitumor responses. To evaluate the selective depletion of alloimmune responses, donor C57BL/6 splenocytes were cocultured for 5 d with irradiated BALB/c splenocytes and then photodepleted (PD). PD-treated splenocytes were infused into lethally irradiated BALB/c (same-party) or C3H/HeJ (third-party) mice. Same-party mice that received PD-treated splenocytes at the time of transplant lived 100 d without evidence of GVHD. In contrast, all mice that received untreated primed splenocytes and third-party mice that received PD-treated splenocytes died of lethal GVHD. To evaluate the preservation of antiviral immune responses, acute lymphocytic choriomeningitis virus infection was used. After photodepletion, expansion of Ag-specific naive CD8(+) T cells and viral clearance remained fully intact. The high selectivity of this novel photosensitizer may have broad applications and provide alternative treatment options for patients with T lymphocyte-mediated diseases.

Immunoselection techniques in hematopoietic stem cell transplantation

Hematopoietic Stem Cells Transplantation (HSCT) is an effective treatment for hematological and non-hematological diseases. The main challenge in autologous HSCT is purging of malignant cells to prevent relapse. In allogeneic HSCT graft-versus-host disease (GvHD) and opportunistic infections are frequent complications. Two types of graft manipulation have been introduced: the first one in the autologous context aimed at separating malignant cells from hematopoietic stem cells (HSC), and the second one in allogeneic HSCT aimed at reducing the incidence of GvHD and at accelerating immune reconstitution. Here we describe the manipulations used for cell purging in autologous HSCT or for T Cell Depletion (TCD) and T cell selection in allogeneic HSCT. More complex manipulations, requiring a Good Manufacturing Practice (GMP) facility, are briefly mentioned.

CD34-Selected Hematopoietic Stem Cell Transplants Conditioned with Myeloablative Regimens and Antithymocyte Globulin for Advanced Myelodysplastic Syndrome: Limited Graft-versus-Host Disease without Increased Relapse

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the only curative therapy for patients with myelodysplastic syndrome (MDS). Donor T cells are critical for the graft-versus-tumor effect but carry the risk of graft-versus-host disease (GVHD). CD34 selection with immunomagnetic beads has been an effective method of depleting alloreactive donor T cells from the peripheral blood graft and has been shown to result in significant reduction in acute and chronic GVHD. We analyzed the outcomes of 102 adults (median age, 57.6 years) with advanced MDS who received a CD34-selected allo-HSCT between January 1997 and April 2012 at Memorial Sloan Kettering Cancer Center. The cumulative incidences of grades II to IV acute GVHD were 9.8% at day 100 (95% confidence interval [CI], 5.0% to 16.5%) and 15.7% at day 180 (95% CI, 9.4% to 23.4%). The cumulative incidence of chronic GVHD at 1 year was 3.9% (95% CI, 1.3% to 9.0%). The cumulative incidences of relapse were 11.8% at 1 year (95% CI, 6.4% to 18.9%) and 15.7% at 2 years (95% CI, 9.4% to 23.4%). Forty-eight patients were alive with a median follow-up of 71.7 months. Rates of overall survival (OS) were 56.9% at 2 years (95% CI, 48% to 67.3%) and 49.3% at 5 years (95% CI, 40.4% to 60.2%). Rates of relapse-free survival (RFS) were 52.0% at 2 years (95% CI, 41.9% to 61.1%) and 47.6% at 5 years (95% CI, 37.5% to 56.9%). The cumulative incidences of nonrelapse mortality were 7.8% at day 100 (95% CI, 3.7% to 14.1%), 22.5% at 1 year (95% CI, 15.0% to 31.1%), and 33.4% at 5 years (95% CI, 24.2% to 42.6%) post-transplant. The incidence of chronic GVHD/RFS overlapped with RFS. These findings demonstrate that ex vivo T cell-depleted allo-HSCT by CD34 selection offers long-term OS and RFS with low incidences of acute and chronic GVHD and without an increased risk of relapse.

High Disease-Free Survival with Enhanced Protection against Relapse after Double-Unit Cord Blood Transplantation When Compared with T Cell-Depleted Unrelated Donor Transplantation in Patients with Acute Leukemia and Chronic Myelogenous Leukemia

Double-unit cord blood (DCB) grafts are a rapidly available stem cell source for adults with high-risk leukemias. However, how disease-free survival (DFS) after DCB transplantation (DCBT) compares to that of unrelated donor transplantation (URDT) is not fully established. We analyzed 166 allograft recipients (66 8/8 HLA-matched URDT, 45 7/8 HLA-matched URDT, and 55 DCBT) ages 16 to 60 years with high-risk acute leukemia or chronic myelogenous leukemia (CML). URDT and DCBT recipients were similar except DCBT recipients were more likely to have lower weight and non-European ancestry and to receive intermediate-intensity conditioning. All URDT recipients received a CD34(+) cell-selected (T cell-depleted) graft. Overall, differences between the 3-year transplantation-related mortality were not significant (8/8 URDT, 18%; 7/8 URDT, 39%; and DCBT, 24%; P = .108), whereas the 3-year relapse risk was decreased after DCBT (8/8 URDT, 23%; 7/8 URDT, 20%; and DCBT 9%, P = .037). Three-year DFS was 57% in 8/8 URDT, 41% in 7/8 URDT, and 68% in DCBT recipients (P = .068), and the 3-year DFS in DCBT recipients was higher than that of 7/8 URDT recipients (P = .021). In multivariate analysis in acute leukemia patients, factors adversely associated with DFS were female gender (hazard ratio [HR], 1.68; P = .031), diagnosis of acute lymphoblastic leukemia (HR, 2.09; P = .004), and 7/8 T cell-depleted URDT (HR, 1.91; P = .037). High DFS can be achieved in adults with acute leukemia and CML with low relapse rates after DCBT. Our findings support performing DCBT in adults in preference to HLA-mismatched T cell-depleted URDT and suggest DCBT is a readily available alternative to T cell-depleted 8/8 URDT, especially in patients requiring urgent transplantation.

The hematopoietic system in the context of regenerative medicine

Hematopoietic stem cells (HSC) represent the prototype stem cell within the body. Since their discovery, HSC have been the focus of intensive research, and have proven invaluable clinically to restore hematopoiesis following inadvertent radiation exposure and following radio/chemotherapy to eliminate hematologic tumors. While they were originally discovered in the bone marrow, HSC can also be isolated from umbilical cord blood and can be "mobilized" peripheral blood, making them readily available in relatively large quantities. While their ability to repopulate the entire hematopoietic system would already guarantee HSC a valuable place in regenerative medicine, the finding that hematopoietic chimerism can induce immunological tolerance to solid organs and correct autoimmune diseases has dramatically broadened their clinical utility. The demonstration that these cells, through a variety of mechanisms, can also promote repair/regeneration of non-hematopoietic tissues as diverse as liver, heart, and brain has further increased their clinical value. The goal of this review is to provide the reader with a brief glimpse into the remarkable potential HSC possess, and to highlight their tremendous value as therapeutics in regenerative medicine.

T-cell depleted allogeneic hematopoietic cell transplants as a platform for adoptive therapy with leukemia selective or virus-specific T-cells

Allogeneic hematopoietic cell transplants adequately depleted of T-cells can reduce or prevent acute and chronic GVHD in both HLA-matched and haplotype-disparate hosts, without post-transplant prophylaxis with immunosuppressive drugs. Recent trials indicate that high doses of CD34+ progenitors from G-CSF mobilized peripheral blood leukocytes isolated and T-cell depleted by immunoadsorption to paramagnetic beads, when administered after myeloablative conditioning with TBI and chemotherapy or chemotherapy alone can secure consistent engraftment and abrogate GVHD in patients with acute leukemia without incurring an increased risk of a recurrent leukemia. Early clinical trials also indicate that high doses of in vitro generated leukemia-reactive donor T-cells can be adoptively transferred and can induce remissions of leukemia relapse without GVHD. Similarly, virus-specific T-cells generated from the transplant donor or an HLA partially matched third party, have induced remissions of Rituxan-refractory EBV lymphomas and can clear CMV disease or viremia persisting despite antiviral therapy in a high proportion of cases. Analyses of treatment responses and failures illustrate both the advantages and limitations of donor or banked, third party-derived T-cells, but underscore the potential of adoptive T-cell therapy in the absence of ongoing immunosuppression.

Effects of T-Cell Depletion on Allogeneic Hematopoietic Stem Cell Transplantation Outcomes in AML Patients

Graft versus host disease (GVHD) remains one of the leading causes of morbidity and mortality associated with conventional allogeneic hematopoietic stem cell transplantation (HCT). The use of T-cell depletion significantly reduces this complication. Recent prospective and retrospective data suggest that, in patients with AML in first complete remission, CD34+ selected grafts afford overall and relapse-free survival comparable to those observed in recipients of conventional grafts, while significantly decreasing GVHD. In addition, CD34+ selected grafts allow older patients, and those with medical comorbidities or with only HLA-mismatched donors to successfully undergo transplantation. Prospective data are needed to further define which groups of patients with AML are most likely to benefit from CD34+ selected grafts. Here we review the history of T-cell depletion in AML, and techniques used. We then summarize the contemporary literature using CD34+ selection in recipients of matched or partially mismatched donors (7/8 or 8/8 HLA-matched), and provide a summary of the risks and benefits of using T-cell depletion.

Comparison of outcomes at two institutions of patients with ALL receiving ex vivo T-cell-depleted or unmodified allografts

We compared outcomes of adult patients receiving T-cell-depleted (TCD) hematopoietic SCT (HCT) without additional GVHD prophylaxis at Memorial Sloan Kettering Cancer Center (MSKCC, N=52), with those of patients receiving conventional grafts at MD Anderson Cancer Center (MDACC, N=115) for ALL in CR1 or CR2. Patients received myeloablative conditioning. Thirty-nine patients received anti-thymocyte globulin at MSKCC and 29 at MDACC. Cumulative incidence of grades 2-4 acute (P=0.001, 17.3% vs 42.6% at 100 days) and chronic GVHD (P=0.006, 13.5% vs 33.4% at 3 years) were significantly lower in the TCD group. The non-relapse mortality at day 100, 1 and 3 years was 15.4, 25.0 and 35.9% in the TCD group and 9.6, 23.6 and 28.6% in the unmodified group (P=0.368). There was no difference in relapse (P=0.107, 21.3% vs 35.5% at 3 years), OS (P=0.854, 42.6% vs 43.0% at 3 years) or RFS (P=0.653, 42.8% vs 35.9% at 3 years). In an adjusted model, age >50, cytogenetics and CR status were associated with inferior RFS (hazard ratio (HR)=2.16, P=0.003, HR=1.77, P=0.022, HR=2.47, P<0.001), whereas graft type was NS (HR=0.90, P=0.635). OS and RFS rates are similar in patients undergoing TCD or conventional HCT, but TCD effectively reduces the rate of GVHD.

Transplant for MDS: challenges and emerging strategies

Allogeneic hematopoietic stem cell transplantation is the only curative treatment for myelodysplastic syndrome. Major improvements in the field of allogeneic stem cell transplantation have made it a better tolerated treatment that can be offered to older patients and patients with co-morbidities. However, treatment related toxicities, graft versus host disease, infectious complications and relapse remain major problems post transplant. With better understanding of disease biology and prognosis and with different types of conditioning regimens as well as different graft sources, a transplant strategy should be tailored to the individual host to maximize the benefits of this procedure.

Impact of peri-transplant vancomycin and fluoroquinolone administration on rates of bacteremia in allogeneic hematopoietic stem cell transplant (HSCT) recipients: a 12-year single institution study

BACKGROUND

We analyzed the effect of peri-transplant prophylaxis on the epidemiology of bacteremia in a 12-year contemporary cohort of allogeneic HSCT recipients at our center.

METHODS

This was an observational study of 1052 consecutive adult HSCT from 2000 to 2011. Formal prophylaxis with vancomycin only, fluoroquinolone (FQ) only, or vancomycin + FQ was implemented in 2006. The cumulative incidence of day 100 bacteremia was compared between the Early Period (2000-2005) and the Recent Period (2006-2011). Predictors for pre-engraftment bacteremia were analyzed with Cox-proportional hazard models in a subcohort of 821 HSCT who received myeloablative or reduced intensity conditioning (MA/RIC).

RESULTS

The incidence of bacteremia decreased in the Recent Period (32% vs 27%; P = 0.002), whereas the rates of resistance in gram-negative rods (GNR) and vancomycin-resistant enterococci (VRE) were similar between the two Periods (P values are not statistically significant.) In multivariate analyses, prophylaxis with vancomycin only or vancomycin + FQ was protective (HR = 0.5; CI = 0.30-0.72) and (HR = 0.3; CI = 0.12-0.52, P < 0.01). Vancomycin or vancomycin + FQ eliminated viridans streptococcal bacteremia (VSB); vancomycin + FQ decreased GNR bacteremia (HR = 0.35; CI = 0.15-0.85).

CONCLUSIONS

Vancomycin-based prophylaxis peri-transplant in MA/RIC HSCT was associated with elimination of VSB and may be considered at centers with high incidence of this infection.

Advances in the treatment of acute graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation (HSCT) has been widely used for the treatment of hematologic malignant and non-malignant hematologic diseases and other diseases. However, acute graft-versus-host disease (GVHD) is a life-threatening complication of allogeneic transplantation. Acute GVHD may occur in 30% of transplant recipients, which is a syndrome of erythematous skin eruption, cholestatic liver disease and intestinal dysfunction, resulting from the activation of donor T lymphocytes by host antigen-presenting cells, resulting in an immune-mediated inflammatory response. Recent scientific advances in the understanding of the pathogenesis involved in the development of acute GVHD and clinical investigation have provided more effective therapeutic strategies for acute GVHD. This review focuses on major scientific and clinical advances in the treatment of acute GVHD.

Ex vivo T cell-depleted versus unmodified allografts in patients with acute myeloid leukemia in first complete remission

This study was conducted to retrospectively compare the clinical outcomes after transplantation of T cell-depleted (TCD) and unmodified allografts in patients with acute myeloid leukemia (AML) in first complete remission (CR1). Patients received TCD grafts at Memorial Sloan-Kettering Cancer Center (MSKCC, N = 115) between 2001 and 2010 using the following preparative regimens: hyperfractionated total body irradiation (HFTBI)+thiotepa+fludarabine; HFTBI+thiotepa+cyclophosphamide; or i.v. busulfan+melphalan+fludarabine. TCD was performed by 1 of 2 immunomagnetic CD34(+) cell selection methods for peripheral blood grafts or by soybean lectin agglutination followed by sheep red blood cell-rosette depletion for bone marrow grafts. No additional graft-versus-host disease (GVHD) prophylaxis was administered. Patients received unmodified grafts at M.D. Anderson Cancer Center (MDACC, N = 181) after conditioning with busulfan+fludarabine and GVHD prophylaxis with tacrolimus+mini-methotrexate. Patients with unrelated or human leukocyte antigen-mismatched donors received anti-thymocyte globulin (ATG) at both centers, with some recipients of matched related donor TCD transplants also receiving ATG, depending upon the preparative regimen. TCD graft recipients were more likely to be older, receive a mismatched transplant, and have peripheral blood used as the graft source. The incidences rates of grades 2 to 4 acute GVHD and chronic GVHD were significantly lower in the TCD graft group (5% versus 18%, and 13% versus 53%). Three-year relapse-free and overall survival rates were 58% and 57%, respectively, in recipients of TCD grafts, and 60% and 66% in recipients of unmodified grafts (P = not significant). Survival and relapse-free survival are similar after TCD and conventional transplants from related/unrelated donors in patients with AML in CR1, but TCD significantly reduces GVHD.

T cell-depleted stem cell transplantation for adults with high-risk acute lymphoblastic leukemia: long-term survival for patients in first complete remission with a decreased risk of graft-versus-host disease

Consolidation with allogeneic hematopoietic stem cell transplantation (allo-HSCT) provides a survival benefit to patients with acute lymphoblastic leukemia (ALL). We have previously reported comparable survival and relapse rates after T cell-depleted (TCD) allo-HSCT compared with unmodified transplantations for acute myelogenous leukemia, myelodysplastic syndrome, and non-Hodgkin lymphoma with significantly decreased graft-versus-host disease (GVHD). We performed a 56-patient retrospective study to evaluate TCD allo-HSCT for the treatment of ALL after myeloablative total body irradiation-based therapy. The 2-year and 5-year overall survival rates for patients with ALL after TCD allo-HSCT were 0.39 (95% confidence interval [CI], 0.26-0.52) and 0.32 (95% CI, 0.19-0.44), respectively, and the 2-year and 5-year disease-free survival rates were 0.38 (95% CI, 0.25-0.50) and 0.32 (95% CI, 0.20-0.44). There was a trend toward improved survival of patients who underwent TCD allo-HSCT in first complete remission compared with those who did so in other remission states. The cumulative incidence of grade II-IV acute GVHD at 1 year was 0.20 (95% CI, 0.10-0.31), and no patients developed grade IV acute GVHD. The cumulative incidence of chronic GVHD in 41 evaluable patients at 2 and 5 years was 0.15 (95% CI, 0.04-0.26), and that of extensive chronic GVHD at 2 and 5 years was 0.05 (95% CI, 0-11.6). We demonstrate OS and DFS rates that compare favorably to unmodified allo-HSCT with lower rates of GVHD.