Haploidentical transplantation for hematologic malignancies: where do we stand?

A comparison of haploidentical versus HLA-identical sibling outpatient hematopoietic cell transplantation using reduced intensity conditioning in patients with acute leukemia

Background

Hematopoietic cell transplantation (HCT) increases survival for acute leukemia. Outpatient allogeneic HCT reduces costs and increases transplant rates in developing countries. We report outcomes of outpatient HLA-identical and haploidentical HCT in acute leukemia.

Methods

This single-center retrospective cohort study analyzed 121 adult patients with acute myeloblastic (AML) and acute lymphoblastic leukemia (ALL) receiving an outpatient allogeneic HCT with peripheral blood allografts after reduced-intensity conditioning (RIC) from 2012-2022.

Results

There were 81 (67%) haploidentical and 40 (33%) HLA-identical transplants. Complete chimerism (CC) at day +100 was not different in HLA-identical compared to haploidentical HCT (32.5% and 38.2%, P=0.054). Post-HCT complications, including neutropenic fever (59.3% vs. 40%), acute graft-versus-host-disease (aGVHD) (46.9% vs. 25%), cytokine release syndrome (CRS) (18.5% vs. 2.5%), and hospitalization (71.6% vs 42.5%) were significantly more frequent in haploidentical HCT. Two-year overall survival (OS) was 60.6% vs. 46.9%, (P=0.464) for HLA-identical and haplo-HCT, respectively. There was no difference in the 2-year disease-free-survival (DFS) (33.3% vs. 35%, P=0.924) between transplant types. In multivariate analysis, positive measurable residual disease (MRD) at 30 days (HR 8.8, P=0.018) and 100 days (HR 28.5, P=0.022) was associated with lower OS, but not with non-relapse mortality (NRM) (P=0.252 and P=0.123, univariate). In univariate analysis, both 30-day and 100-day MRD were associated with lower DFS rates (P=0.026 and P=0.006), but only day 30 MRD was significant in multivariate analysis (P=0.050). In the case of relapse, only MRD at day 100 was associated with increased risk in the univariate and multivariate analyses (HR 4.48, P=0.003 and HR 4.67, P=0.008). Chronic graft-versus-host-disease (cGVHD) was protective for NRM (HR 0.38, P=0.015). There was no difference in cumulative incidence of relapse (CIR) between transplant types (P=0.126). Forty-four (36.4%) patients died, with no difference between HCT type (P=0.307). Septic shock was the most frequent cause of death with 17 cases, with no difference between transplant types.

Conclusions

Outpatient peripheral blood allogenic HCT after RIC is a valid and effective alternative for adult patients suffering acute myeloblastic or lymphoblastic leukemia in low-income populations.

Haploidentical Stem Cell Transplantation Using Post-Transplant Cyclophosphamide for T-Cell Prolymphocytic Leukemia after Alemtuzumab Induction Therapy: A Case Report

T-cell prolymphocytic leukemia (T-PLL) is a rare aggressive disease with a poor prognosis. Allogeneic stem cell transplantation (allo-SCT) followed by alemtuzumab administration is the most promising treatment for T-PLL but is associated with a high risk of infections as alemtuzumab strongly suppresses cellular immunity, leading to high transplant-related mortality and unsatisfactory survival rates. In addition, for patients without human leukocyte antigen-matched donors, haploidentical stem cell transplantation (haplo-SCT) using post-transplant cyclophosphamide (PTCy) has been used because of the ready availability of donors and achievement of results comparable to those of transplantation with human leukocyte antigen-matched donors. However, there are no reports on the efficacy and safety, including infectious complications, of haplo-SCT with PTCy after alemtuzumab therapy in patients with. Here, we describe a 66-year-old Japanese male patient with T-PLL treated successfully with haplo-SCT after induction therapy of alemtuzumab for T-PLL. Approximately 3 months after the achievement of complete remission with alemtuzumab for T-PLL, haplo-SCT with reduced-intensity conditioning and PTCy was performed. Infectious complications were improved by early therapeutic interventions, and peripheral T cell counts gradually recovered. The patient was alive for more than 16 months after allo-SCT with no signs of relapse. Thus, haplo-SCT using PTCy should be considered as an option after alemtuzumab treatment for T-PLL.

Comparison of NK alloreactivity prediction models based on KIR-MHC interactions in haematopoeitic stem cell transplantation

The biological processes underlying NK cell alloreactivity in haematopoietic stem cell transplantation (HSCT) remain unclear. Many different models to predict NK alloreactivity through KIR and MHC genotyping exist, raising ambiguities in its utility and application for clinicians. We assessed 27 predictive models, broadly divided into six categories of alloreactivity prediction: ligand-ligand, receptor-ligand, educational, KIR haplotype-based, KIR matching and KIR allelic polymorphism. The models were applied to 78 NGS-typed donor/recipient pairs undergoing allogeneic HSCT in genoidentical (n=43) or haploidentical (n=35) matchings. Correlations between different predictive models differed widely, suggesting that the choice of the model in predicting NK alloreactivity matters. For example, two broadly used models, educational and receptor-ligand, led to opposing predictions especially in the genoidentical cohort. Correlations also depended on the matching fashion, suggesting that this parameter should also be taken into account in the choice of the scoring strategy. The number of centromeric B-motifs was the only model strongly correlated with the incidence of acute graft-versus-host disease in our set of patients in both the genoidentical and the haploidentical cohorts, suggesting that KIR-based alloreactivity, not MHC mismatches, are responsible for it. To our best knowledge, this paper is the first to experimentally compare NK alloreactivity prediction models within a cohort of genoidentical and haploidentical donor-recipient pairs. This study helps to resolve current discrepancies in KIR-based alloreactivity predictions and highlights the need for deeper consideration of the models used in clinical studies as well as in medical practice.

Lower dose of ATG combined with basiliximab for haploidentical hematopoietic stem cell transplantation is associated with effective control of GVHD and less CMV viremia

Currently, the graft-versus-host disease (GVHD) prophylaxis consists of an immunosuppressive therapy mainly based on antithymocyte globulin (ATG) or post-transplant cyclophosphamide (PTCy). GVHD remains a major complication and limitation to successful allogeneic haploidentical hematopoietic stem cell transplantation (haplo-HSCT). We modified the ATG-based GVHD prophylaxis with the addition of basiliximab in the setting of haplo-HSCT and attempted to explore the appropriate dosages. We conducted a retrospective analysis of 239 patients with intermediate- or high-risk hematologic malignancies who received haplo-HSCT with unmanipulated peripheral blood stem cells combined or not with bone marrow. All patients received the same GVHD prophylaxis consisting of the combination of methotrexate, cyclosporine or tacrolimus, mycofenolate-mofetil, and basiliximab with different doses of ATG (5-9mg/kg). With a median time of 11 days (range, 7-40 days), the rate of neutrophil engraftment was 96.65%. The 100-day cumulative incidences (CIs) of grade II-IV and III-IV aGVHD were 15.8 ± 2.5% and 5.0 ± 1.5%, while the 2-year CIs of total cGVHD and extensive cGVHD were 9.8 ± 2.2% and 4.1 ± 1.5%, respectively. The 3-year CIs of treatment-related mortality (TRM), relapse, overall survival (OS), and disease-free survival (DFS) were 14.6 ± 2.6%, 28.1 ± 3.4%, 60.9 ± 3.4%, 57.3 ± 3.4%, respectively. Furthermore, the impact of the reduction of the ATG dose to 6 mg/kg or less in combination with basiliximab on GVHD prevention and transplant outcomes among patients was analyzed. Compared to higher dose of ATG(>6mg/kg), lower dose of ATG (≤6mg/kg) was associated with a significant reduced risk of CMV viremia (52.38% vs 79.35%, P<0.001), while the incidences of aGVHD and cGVHD were similar between the two dose levels. No significant effect was found with regard to the risk of relapse, TRM, and OS. ATG combined with basiliximab could prevent GVHD efficiently and safely. The optimal scheme of using this combined regimen of ATG and basiliximab is that administration of lower dose ATG (≤6mg/kg), which seems to be more appropriate for balancing infection control and GVHD prophylaxis.

Risk factors for adverse outcomes following haploidentical hematopoietic cell transplantation with posttransplant cyclophosphamide: a two-center analysis

Allogeneic hematopoietic cell transplantation (HCT) is a potentially curative therapy for several malignant hematologic diseases and alternative donors, including haploidentical, play a significant role in HCT. Despite the increasing use of haplo-HCT with PTCy, some questions remain open. The objective of the present study was to investigate risk factors for adverse outcomes after haplo-HCT with PTCy. This is a retrospective study conducted at two Brazilian centers. A total of 103 patients with hematologic malignancies who underwent first allogeneic, haploidentical HCT with PTCy were included. Risk factors for death were age at transplant (HR = 1.03 for each year; p = 0.002) and high/very high disease risk index (DRI; HR = 2.77; p = 0.0007) and mother as the donor compared with other donors (HR = 3.53; p = 0.005). In multivariate analysis, PFS was significantly poorer for older patients (HR = 1.02; p = 0.006), high/very high DRI (HR = 2.39; p = 0.003), and mother as the donor compared with other donors (HR = 3.18; p = 0.006). Relapse rate was higher for high/very high DRI (HR = 4.01; p = 0.002) and mother as the donor compared with other donors (HR = 2.52; p = 0.05). NRM was higher for older patients (HR = 1.03 for each year; p = 0.03). Tacrolimus was a protective factor for grades II-IV aGVHD (HR = 0.46; p = 0.04) compared with cyclosporine. Peripheral blood (PBSC) was a risk factor for cGVHD (HR = 3.48; p = 0.006), while tacrolimus was protective (HR = 0.30; p = 0.009). Mother as the donor compared with other donors was also a risk factor for poorer OS, PFS, and relapse, suggesting that this combination should be avoided. Tacrolimus was protective for both grades II-IV aGVHD and cGVHD, suggesting that tacrolimus may be more effective than cyclosporine in preventing GVHD. PBSC was a risk factor for cGVHD without any impact on relapse. Prospective studies comparing tacrolimus with cyclosporine are awaited.

KIR in Allogeneic Hematopoietic Stem Cell Transplantation: Need for a Unified Paradigm for Donor Selection

Allogeneic hematopoietic stem cell transplantation (aHSCT) is a lifesaving therapy for hematological malignancies. For years, a fully matched HLA donor was a requisite for the procedure. However, new immunosuppressive strategies have enabled the recruitment of viable alternative donors, particularly haploidentical donors. Over 95% of patients have at least two potential haploidentical donors available to them. To identify the best haploidentical donor, the assessment of new immunogenetic criteria could help. To this end, the clinical benefit of KIR genotyping in aHSCT has been widely studied but remains contentious. This review aims to evaluate the importance of KIR-driven NK cell alloreactivity in the context of aHSCT and explain potential reasons for the discrepancies in the literature. Here, through a non-systematic review, we highlight how the studies in this field and their respective predictive models or scoring strategies could be conceptually opposed, explaining why the role of NK cells remains unclear in aHCST outcomes. We evaluate the limitations of each published prediction model and describe how every scoring strategy to date only partly delivers the requirements for optimally effective NK cells in aHSCT. Finally, we propose approaches toward finding the optimal use of KIR genotyping in aHSCT for a unified criterion for donor selection.

Survival and Functional Immune Reconstitution After Haploidentical Stem Cell Transplantation in Atm-Deficient Mice

Hematopoietic stem cell transplantation (HSCT) has been proposed as a promising therapeutic opportunity to improve immunity and prevent hematologic malignancies in Ataxia-telangiectasia (A-T). However, experience in the transplantation strategy for A-T patients is still scarce. The aim of this study was to investigate whether different approaches of HSCT are feasible in regard to graft versus host response and sufficient concerning functional immune reconstitution. Atm-deficient mice were treated with a clinically relevant non-myeloablative host-conditioning regimen and transplanted with CD90.2-depleted, green fluorescent protein (GFP)-expressing, and ataxia telangiectasia mutated (ATM)-competent bone marrow donor cells in a syngeneic, haploidentical or allogeneic setting. Like syngeneic HSCT, haploidentical HSCT, but not allogeneic HSCT extended the lifespan of Atm-deficient mice through the reduction of thymic tumors and normalized T-cell numbers. Donor-derived splenocytes isolated from transplanted Atm-deficient mice filled the gap of cell loss in the naïve T-cell population and raised CD4 cell functionality up to wild-type level. Interestingly, HSCT using heterozygous donor cells let to a significantly improved survival of Atm-deficient mice and increased CD4 cell numbers as well as CD4 cell functionality equivalent to HSCT using with wild-type donor cells. Our data provided evidence that haploidentical HSCT could be a feasible strategy for A-T, possibly even if the donor is heterozygous for ATM. However, this basic research cannot substitute any research in humans.

Comparing transplant outcomes in ALL patients after haploidentical with PTCy or matched unrelated donor transplantation

We compared outcomes of 1461 adult patients with acute lymphoblastic leukemia (ALL) receiving hematopoietic cell transplantation (HCT) from a haploidentical (n = 487) or matched unrelated donor (MUD; n = 974) between January 2005 and June 2018. Graft-versus-host disease (GVHD) prophylaxis was posttransplant cyclophosphamide (PTCy), calcineurin inhibitor (CNI), and mycophenolate mofetil (MMF) for haploidentical, and CNI with MMF or methotrexate with/without antithymoglobulin for MUDs. Haploidentical recipients were matched (1:2 ratio) with MUD controls for sex, conditioning intensity, disease stage, Philadelphia-chromosome status, and cytogenetic risk. In the myeloablative setting, day +28 neutrophil recovery was similar between haploidentical (87%) and MUD (88%) (P = .11). Corresponding rates after reduced-intensity conditioning (RIC) were 84% and 88% (P = .47). The 3-month incidence of grade II-IV acute GVHD (aGVHD) and 3-year chronic GVHD (cGVHD) was similar after haploidentical compared with MUD: myeloablative conditioning, 33% vs 34% (P = .46) for aGVHD and 29% vs 31% for cGVHD (P = .58); RIC, 31% vs 30% (P = .06) for aGVHD and 24% vs 29% for cGVHD (P = .86). Among patients receiving myeloablative regimens, 3-year probabilities of overall survival were 44% and 51% with haploidentical and MUD (P = .56). Corresponding rates after RIC were 43% and 42% (P = .6). In this large multicenter case-matched retrospective analysis, despite the limitations of a registry-based study (ie, unavailability of key elements such as minimal residual disease testing), our analysis indicated that outcomes of patients with ALL undergoing HCT from a haploidentical donor were comparable with 8 of 8 MUD transplantations.

Immunomodulatory Effects of Bendamustine in Hematopoietic Cell Transplantation

Bendamustine (BEN) is a unique alkylating agent with efficacy against a broad range of hematological malignancies, although investigations have only recently started to delve into its immunomodulatory effects. These immunomodulatory properties of BEN in the context of hematopoietic cell transplantation (HCT) are reviewed here. Pre- and post-transplant use of BEN in multiple murine models have consistently resulted in reduced GvHD and enhanced GvL, with significant changes to key immunological cell populations, including T-cells, myeloid derived suppressor cells (MDSCs), and dendritic cells (DCs). Further, in vitro studies find that BEN enhances the suppressive function of MDSCs, skews DCs toward cDC1s, enhances Flt3 expression on DCs, increases B-cell production of IL-10, inhibits STAT3 activation, and suppresses proliferation of T- and B-cells. Overall, BEN has a broad range of immunomodulatory effects that, as they are further elucidated, may be exploited to improve clinical outcomes. As such, clinical trials are currently underway investigating new potential applications of BEN in the setting of allogeneic HCT.

Haploidentical Hematopoietic Stem Cell Transplantation in Leukemia's: Experience from a Cancer Center in India

There has been a surge in haploidentical hematopoietic stem cell transplantation (HSCT) in India recently. However, there is a paucity of data on haploidentical HSCT from India. The report is an analysis of data of haploidentical HSCT performed at our center. Analysis of patients with acute leukemia or chronic myeloid leukemia who underwent haploidentical HSCT during 2014-2019 was performed. The graft versus host disease (GVHD) prophylaxis was post-transplant Cyclophosphamide with Mycophenolate-mofetil and Cyclosporine. All patients were transfused peripheral blood stem cells from donors. Overall survival (OS) was calculated using the Kaplan-Meier method. Twenty-one patients underwent haploidentical HSCT. Fourteen-patients were males. The median age of patients was 15 years. Fludarabine with total body irradiation was the most common conditioning regimen (n = 15, 71.4%). The median duration for neutrophil and platelet engraftment was 14 days. Cumulative incidence of acute and chronic GVHD was 19%, and 38% respectively. The median follow-up was 26 months and the two-year OS was 38%. Twelve (57%) patients died during the study period, 8 patients (38%) died from transplant-related mortality (TRM), and 4 from disease relapse. Sepsis was the cause of death in six of the eight TRM. Nine out of 21 patients (42.8%) are leukemia-free on follow-up. Haploidentical HSCT is a promising modality of treatment in patients who have no suitable matched donors. Though the TRM remains high, good disease control was achieved in 42.8% of patients. Multi-drug resistant bacterial infection remains a challenge in performing haploidentical HSCT in developing countries.

Allogeneic bone marrow transplantation with post-transplant cyclophosphamide for patients with HIV and haematological malignancies: a feasibility study

BACKGROUND

Allogeneic blood or marrow transplantation (alloBMT) is a potentially life-saving treatment for individuals with HIV and haematological malignancies; challenges include identifying donors and maintaining antiretroviral therapy (ART). The objectives of our study were to investigate interventions to expand donor options and to prevent ART interruptions for patients with HIV in need of alloBMT.

METHODS

This single-arm, interventional trial took place at the Johns Hopkins Sidney Kimmel Comprehensive Cancer Center (Baltimore, MD, USA). Individuals with HIV who were at least 18 years of age and referred for alloBMT for a standard clinical indication were eligible. The only exclusion criterion was a history of documented resistance to enfuvirtide. We used post-transplant cyclophosphamide as graft-versus-host disease (GVHD) prophylaxis to expand donor options and an optimised ART strategy of avoiding pharmacoenhancers and adding subcutaneous enfuvirtide during post-transplant cyclophosphamide and during oral medication intolerance. Our primary outcome was the proportion of participants who maintained ART through day 60 after alloBMT. We measured the HIV latent reservoir using a quantitative viral outgrowth assay. This study is registered on ClinicalTrials.gov, NCT01836068.

FINDINGS

Between June 1, 2013, and August 27, 2015, nine patients who were referred for transplant provided consent. Two patients had relapsed malignancy before donor searches were initiated. Seven patients had suitable donors identified (two matched sibling, two matched unrelated, two haploidentical, and one single-antigen mismatched unrelated) and proceeded to alloBMT. All patients maintained ART through day 60 and required ART changes (median 1, range 1-3) in the first 90 days. One patient stopped ART and developed HIV rebound with grade 4 meningoencephalitis at day 146. Among six patients who underwent alloBMT and had longitudinal measurements available, the HIV latent reservoir was not detected post-alloBMT in four patients with more than 95% donor chimerism, consistent with a 2·06-2·54 log10 reduction in the HIV latent reservoir. In the two patients with less than 95% donor chimerism, the HIV latent reservoir remained stable.

INTERPRETATION

By using post-transplant cyclophosphamide as GVHD prophylaxis, we successfully expanded alloBMT donor options for patients with HIV. Continuing ART with a regimen that includes enfuvirtide post-alloBMT was safe, but life-threatening viral rebound can occur with ART interruption.

FUNDING

amfAR (the Foundation for AIDS Research), Johns Hopkins University Center for AIDS Research, and National Cancer Institute.

Key Aspects of the Immunobiology of Haploidentical Hematopoietic Cell Transplantation

Hematopoietic stem cell transplantation from a haploidentical donor is increasingly used and has become a standard donor option for patients lacking an appropriately matched sibling or unrelated donor. Historically, prohibitive immunological barriers resulting from the high degree of HLA-mismatch included graft-vs.-host disease (GVHD) and graft failure. These were overcome with increasingly sophisticated strategies to manipulate the sensitive balance between donor and recipient immune cells. Three different approaches are currently in clinical use: (a) ex vivo T-cell depletion resulting in grafts with defined immune cell content (b) extensive immunosuppression with a T-cell replete graft consisting of G-CSF primed bone marrow and PBSC (GIAC) (c) T-cell replete grafts with post-transplant cyclophosphamide (PTCy). Intriguing studies have recently elucidated the immunologic mechanisms by which PTCy prevents GVHD. Each approach uniquely affects post-transplant immune reconstitution which is critical for the control of post-transplant infections and relapse. NK-cells play a key role in haplo-HCT since they do not mediate GVHD but can successfully mediate a graft-vs.-leukemia effect. This effect is in part regulated by KIR receptors that inhibit NK cell cytotoxic function when binding to the appropriate HLA-class I ligands. In the context of an HLA-class I mismatch in haplo-HCT, lack of inhibition can contribute to NK-cell alloreactivity leading to enhanced anti-leukemic effect. Emerging work reveals immune evasion phenomena such as copy-neutral loss of heterozygosity of the incompatible HLA alleles as one of the major mechanisms of relapse. Relapse and infectious complications remain the leading causes impacting overall survival and are central to scientific advances seeking to improve haplo-HCT. Given that haploidentical donors can typically be readily approached to collect additional stem- or immune cells for the recipient, haplo-HCT represents a unique platform for cell- and immune-based therapies aimed at further reducing relapse and infections. The rapid advancements in our understanding of the immunobiology of haplo-HCT are therefore poised to lead to iterative innovations resulting in further improvement of outcomes with this compelling transplant modality.

The Graft-Versus-Leukemia Effect in AML

Allogeneic hematopoietic stem cell transplantation (allo-SCT) is the most established and commonly used cellular immunotherapy in cancer care. It is the most potent anti-leukemic therapy in patients with acute myeloid leukemia (AML) and is routinely used with curative intent in patients with intermediate and poor risk disease. Donor T cells, and possibly other immune cells, eliminate residual leukemia cells after prior (radio)chemotherapy. This immune-mediated response is known as graft-versus-leukemia (GvL). Donor alloimmune responses can also be directed against healthy tissues, which is known as graft-versus-host disease (GvHD). GvHD and GvL often co-occur and, therefore, a major barrier to exploiting the full immunotherapeutic benefit of donor immune cells against patient leukemia is the immunosuppression required to treat GvHD. However, curative responses to allo-SCT and GvHD do not always occur together, suggesting that these two immune responses could be de-coupled in some patients. To make further progress in successfully promoting GvL without GvHD, we must transform our limited understanding of the cellular and molecular basis of GvL and GvHD. Specifically, in most patients we do not understand the antigenic basis of immune responses in GvL and GvHD. Identification of antigens important for GvL but not GvHD, and vice versa, could impact on donor selection, allow us to track GvL immune responses and begin to specifically harness and strengthen anti-leukemic immune responses against patient AML cells, whilst minimizing the toxicity of GvHD.

Review of Haploidentical Hematopoietic Cell Transplantation

Use of haploidentical (haplo) donors for hematopoietic cell transplantation (HCT) has significantly increased in the last decade. The major advantage with this strategy is universal availability and faster acquisition of the donor, along with affordability and provision of immunotherapy in post-transplantation period. Historically, haplo-HCT was associated with compromised outcomes because of high rates of graft-versus-host disease and graft failure, but after the development of a post-transplantation high-dose cyclophosphamide strategy, which results in selective T-cell depletion, these issues have been addressed to a large extent. Nevertheless, graft failure, high treatment-related mortality due to graft-versus-host disease, infections, delayed immune reconstitution, and disease relapse remain significant concerns. As the experience with haplo-HCTs grows, the clinical outcomes are becoming more at par with those seen with fully matched unrelated donor allogeneic HCTs.

B-Cell-Based and Soluble Biomarkers in Body Liquids for Predicting Acute/Chronic Graft-versus-Host Disease after Allogeneic Hematopoietic Stem Cell Transplantation

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the main curative therapy for hematological malignancy such as leukemias, lymphomas, or multiple myelomas and some other hematological disorders. In this therapy, cure of hematological diseases relies on graft-versus-malignancy effects by allogenic immune cells. However, severe posttransplant treatment-associated complications such as acute graft-versus-host disease (aGvHD) and chronic graft-versus-host disease (cGvHD) limit this approach. Most research into GvHD has concentrated on the aGvHD, while the more complex and multifaceted chronic form has been largely poorly investigated. cGvHD is a multi-organ autoimmune disorder and is the major cause of non-relapse morbidity and mortality following allo-HSCT, occurring in about 50% of patients, or 13,000–15,000 patients per year worldwide. Therefore, there is a high medical need for an early prediction of these therapy-associated toxicities. Biomarkers have gained importance over the last decade in diagnosis, in prognosis, and in prediction of pending diseases or side effects. Biomarkers can be cells, factors isolated from target tissues, or soluble factors that can be detected in body fluids. In this review, we aim to summarize some of the recent developments of biomarkers in the field of allo-HSCT. We will focus on cell-based biomarkers (B-cell subsets) for cGvHD and soluble factors including microRNA (miRNA), which are excreted into serum/plasma and urine. We also discuss the potential role of cytosolic and extracellular 70 kDa heat shock proteins (HSP70) as potential biomarkers for aGvHD and their role in preclinical models. Proteomic biomarkers in the blood have been used as predictors of treatment responses in patients with aGvHD for many years. More recently, miRNAs have been found to serve as a biomarker to diagnose aGvHD in the plasma. Another development relates to urine-based biomarkers that are usually detected by capillary electrophoresis and mass spectrometry. These biomarkers have the potential to predict the development of severe aGvHD (grades III–IV), overall mortality, and the pending development of cGvHD in patients posttransplant.

Primary Immune Deficiency Treatment Consortium (PIDTC) update

The Primary Immune Deficiency Treatment Consortium (PIDTC) is a collaboration of 41 North American centers studying therapy for rare primary immune deficiency diseases (PIDs), including severe combined immune deficiency (SCID), Wiskott-Aldrich syndrome (WAS), and chronic granulomatous disease (CGD). An additional 3 European centers have partnered with the PIDTC to study CGD. Natural history protocols of the PIDTC analyze outcomes of treatment for rare PIDs in multicenter longitudinal retrospective, prospective, and cross-sectional studies. Since 2009, participating centers have enrolled more than 800 subjects on PIDTC protocols for SCID, and enrollment in the studies on WAS and CGD is underway. Four pilot projects have been funded, and 12 junior investigators have received fellowship awards. Important publications of the consortium describe the outcomes of hematopoietic cell transplantation for SCID during 2000-2009, diagnostic criteria for SCID, and the pilot project of newborn screening for SCID in the Navajo Nation. The PIDTC Annual Scientific Workshops provide an opportunity to strengthen collaborations with junior investigators, patient advocacy groups, and international colleagues. Funded by the National Institute of Allergy and Infectious Diseases and the Office of Rare Diseases Research, National Center for Advancing Translational Sciences, the PIDTC has recently received renewal for another 5 years. Here we review accomplishments of the group, projects underway, highlights of recent workshops, and challenges for the future.

Haploidentical Stem Cell Transplantation in Adult Haematological Malignancies

Haematopoietic stem cell transplantation is a well-established treatment option for both hematological malignancies and nonmalignant conditions such as aplastic anemia and haemoglobinopathies. For those patients lacking a suitable matched sibling or matched unrelated donor, haploidentical donors are an alternative expedient donor pool. Historically, haploidentical transplantation led to high rates of graft rejection and GVHD. Strategies to circumvent these issues include T cell depletion and management of complications thereof or T replete transplants with GVHD prophylaxis. This review is an overview of these strategies and contemporaneous outcomes for hematological malignancies in adult haploidentical stem cell transplant recipients.

The indications for allogeneic stem cell transplantation in myeloid malignancies

BACKGROUND

The overall incidence of myeloid malignancies is 8.6 per 100 000 persons. Allogeneic stem-cell transplantation (SCT) is a major therapeutic option despite its risks, which include graft-versus-host disease (GvHD) and infection. In Germany, about 1600 patients with myeloid malignancies undergo SCT each year. The indications for SCT have changed since the introduction of tyrosine kinase inhibitors (TKI) and improved methods of SCT.

METHODS

This article is based on relevant guidelines from Germany and abroad and on a selective review of the literature from 2010 onward.

RESULTS

The individual indication for SCT is based on the risk of disease progression, accompanying illnesses, the probability that SCT will result in cure, and the risk of complications. There is good evidence favoring allogeneic SCT in the following situations affecting 20% to 50% of patients with the respective disease: advanced chronic myeloid leukemia (CML) or CML that does not respond to TKI, Philadelphia chromosome-negative myeloproliferative neoplasm (Ph- MPN) or myelodysplastic syndrome (MDS) with a high risk of progression, and acute myeloid leukemia (AML) that has high-risk cytogenetic features or is recurrent. Good evidence is accumulating in favor of allogeneic SCT in older patients as well.

CONCLUSION

The prognosis of patients with myeloid neoplasm can now be assessed more accurately than before. This facilitates well-founded clinical decision-making about SCT, which is the only potentially curative treatment for most patients with myeloid neoplasm. Patients up to about age 75 should be referred to a transplantation center for consultation at an early stage of their disease so that the treatment options can be evaluated. A major goal of current research is to reduce toxicity with innovative forms of treatment.

Minimal Residual Disease Evaluation in Childhood Acute Lymphoblastic Leukemia: An Economic Analysis

BACKGROUND

Minimal residual disease (MRD) testing by higher performance techniques such as flow cytometry and polymerase chain reaction (PCR) can be used to detect the proportion of remaining leukemic cells in bone marrow or peripheral blood during and after the first phases of chemotherapy in children with acute lymphoblastic leukemia (ALL). The results of MRD testing are used to reclassify these patients and guide changes in treatment according to their future risk of relapse. We conducted a systematic review of the economic literature, cost-effectiveness analysis, and budget-impact analysis to ascertain the cost-effectiveness and economic impact of MRD testing by flow cytometry for management of childhood precursor B-cell ALL in Ontario.

METHODS

A systematic literature search (1998-2014) identified studies that examined the incremental cost-effectiveness of MRD testing by either flow cytometry or PCR. We developed a lifetime state-transition (Markov) microsimulation model to quantify the cost-effectiveness of MRD testing followed by risk-directed therapy to no MRD testing and to estimate its marginal effect on health outcomes and on costs. Model input parameters were based on the literature, expert opinion, and data from the Pediatric Oncology Group of Ontario Networked Information System. Using predictions from our Markov model, we estimated the 1-year cost burden of MRD testing versus no testing and forecasted its economic impact over 3 and 5 years.

RESULTS

In a base-case cost-effectiveness analysis, compared with no testing, MRD testing by flow cytometry at the end of induction and consolidation was associated with an increased discounted survival of 0.0958 quality-adjusted life-years (QALYs) and increased discounted costs of $4,180, yielding an incremental cost-effectiveness ratio (ICER) of $43,613/QALY gained. After accounting for parameter uncertainty, incremental cost-effectiveness of MRD testing was associated with an ICER of $50,249/QALY gained. In the budget-impact analysis, the 1-year cost expenditure for MRD testing by flow cytometry in newly diagnosed patients with precursor B-cell ALL was estimated at $340,760. We forecasted that the province would have to pay approximately $1.3 million over 3 years and $2.4 million over 5 years for MRD testing by flow cytometry in this population.

CONCLUSIONS

Compared with no testing, MRD testing by flow cytometry in newly diagnosed patients with precursor B-cell ALL represents good value for money at commonly used willingness-to-pay thresholds of $50,000/QALY and $100,000/QALY.

Haploidentical Hematopoietic Cell Transplantation with Post-Transplant Cyclophosphamide in a Patient with Chronic Granulomatous Disease and Active Infection: A First Report

PURPOSE

We describe haploidentical hematopoietic cell transplantation (HCT) with high-dose post-transplant cyclophosphamide (PTCy) in a boy with x-linked chronic granulomatous disease (CGD).

METHODS

A persistent and life-threatening fungal infection was the indication for HSCT. Non-myeloablative conditioning with PTCy (50 mg/kg days 3 and 4) was used in the absence of fully matched donors.

RESULTS

Engraftment occurred on day 24. The patient experienced Grade 2 graft-versus-host disease of the skin and gastrointestinal tract and CMV infection, both of which were controlled. Chimerism was 100 % at days 30 and 6 months. Cessation of antifungal therapy was consistent with cure of the infection.

CONCLUSIONS

Haploidentical HCT with high-dose PTCy for CGD is feasible and succeeded even in the context of active infection.

Improving the safety of cell therapy with the TK-suicide gene

While opening new frontiers for the cure of malignant and non-malignant diseases, the increasing use of cell therapy poses also several new challenges related to the safety of a living drug. The most effective and consolidated cell therapy approach is allogeneic hematopoietic stem cell transplantation (HSCT), the only cure for several patients with high-risk hematological malignancies. The potential of allogeneic HSCT is strictly dependent on the donor immune system, particularly on alloreactive T lymphocytes, that promote the beneficial graft-versus-tumor effect (GvT), but may also trigger the detrimental graft-versus-host-disease (GvHD). Gene transfer technologies allow to manipulate donor T-cells to enforce GvT and foster immune reconstitution, while avoiding or controlling GvHD. The suicide gene approach is based on the transfer of a suicide gene into donor lymphocytes, for a safe infusion of a wide T-cell repertoire, that might be selectively controlled in vivo in case of GvHD. The herpes simplex virus thymidine kinase (HSV-TK) is the suicide gene most extensively tested in humans. Expression of HSV-TK in donor lymphocytes confers lethal sensitivity to the anti-herpes drug, ganciclovir. Progressive improvements in suicide genes, vector technology and transduction protocols have allowed to overcome the toxicity of GvHD while preserving the antitumor efficacy of allogeneic HSCT. Several phase I-II clinical trials in the last 20 years document the safety and the efficacy of HSV-TK approach, able to maintain its clear value over the last decades, in the rapidly progressing horizon of cancer cellular therapy.

Allogeneic hematopoietic SCT in multiple myeloma: long-term results from a single institution

The role of allogeneic hematopoietic SCT (allo-HCT) in multiple myeloma (MM) remains controversial. A total of 58 patients received an allo-HCT (25 of them with myeloablative conditioning-allo-MAC-and 33 with reduced-intensity conditioning-allo-RIC) at our institution over a 28-year period. The CR rate for allo-MAC was 36%. The incidence of grade III-IV acute GVHD (aGVHD) and chronic GVHD (cGVHD) was 28% and 39%, respectively The TRM at any time was 60% and the main causes of death were aGVHD or infectious complications not directly related to GVHD. The estimated PFS and OS at 15 years were 8% and 15%, respectively. The CR rate with allo-RIC was 45%. The incidence of grade III-IV aGVHD and cGVHD were 24% and 41%, respectively. The TRM at any time was 33% and was mainly related to aGVHD. The estimated PFS and OS at 5 years were 22% and 38%, respectively. Despite its high TRM, a proportion of patients with high-risk myeloma (early relapse and newly diagnosed ultrahigh risk) may obtain long-term disease control with allo-HCT. New approaches aimed at decreasing the incidence of aGVHD, and consequently to decrease the TRM, are needed.

In silico Derivation of HLA-Specific Alloreactivity Potential from Whole Exome Sequencing of Stem-Cell Transplant Donors and Recipients: Understanding the Quantitative Immunobiology of Allogeneic Transplantation

Donor T-cell mediated graft versus host (GVH) effects may result from the aggregate alloreactivity to minor histocompatibility antigens (mHA) presented by the human leukocyte antigen (HLA) molecules in each donor–recipient pair undergoing stem-cell transplantation (SCT). Whole exome sequencing has previously demonstrated a large number of non-synonymous single nucleotide polymorphisms (SNP) present in HLA-matched recipients of SCT donors (GVH direction). The nucleotide sequence flanking each of these SNPs was obtained and the amino acid sequence determined. All the possible nonameric peptides incorporating the variant amino acid resulting from these SNPs were interrogated in silico for their likelihood to be presented by the HLA class I molecules using the Immune Epitope Database stabilized matrix method (SMM) and NetMHCpan algorithms. The SMM algorithm predicted that a median of 18,396 peptides weakly bound HLA class I molecules in individual SCT recipients, and 2,254 peptides displayed strong binding. A similar library of presented peptides was identified when the data were interrogated using the NetMHCpan algorithm. The bioinformatic algorithm presented here demonstrates that there may be a high level of mHA variation in HLA-matched individuals, constituting a HLA-specific alloreactivity potential.

Hematopoietic stem cell transplantation-50 years of evolution and future perspectives

Hematopoietic stem cell transplantation is a highly specialized and unique medical procedure. Autologous transplantation allows the administration of high-dose chemotherapy without prolonged bone marrow aplasia. In allogeneic transplantation, donor-derived stem cells provide alloimmunity that enables a graft-versus-tumor effect to eradicate residual disease and prevent relapse. The first allogeneic transplantation was performed by E. Donnall Thomas in 1957. Since then the field has evolved and expanded worldwide. New indications beside acute leukemia and aplastic anemia have been constantly explored and now include congenital disorders of the hematopoietic system, metabolic disorders, and autoimmune disease. The use of matched unrelated donors, umbilical cord blood units, and partially matched related donors has dramatically extended the availability of allogeneic transplantation. Transplant-related mortality has decreased due to improved supportive care, including better strategies to prevent severe infections and with the incorporation of reduced-intensity conditioning protocols that lowered the toxicity and allowed for transplantation in older patients. However, disease relapse and graft-versus-host disease remain the two major causes of mortality with unsatisfactory progress. Intense research aiming to improve adoptive immunotherapy and increase graft-versus-leukemia response while decreasing graft-versus-host response might bring the next breakthrough in allogeneic transplantation. Strategies of graft manipulation, tumor-associated antigen vaccinations, monoclonal antibodies, and adoptive cellular immunotherapy have already proved clinically efficient. In the following years, allogeneic transplantation is likely to become more complex, more individualized, and more efficient.

Long-term outcome after haploidentical stem cell transplant and infusion of T cells expressing the inducible caspase 9 safety transgene

Adoptive transfer of donor-derived T lymphocytes expressing a safety switch may promote immune reconstitution in patients undergoing haploidentical hematopoietic stem cell transplant (haplo-HSCT) without the risk for uncontrolled graft versus host disease (GvHD). Thus, patients who develop GvHD after infusion of allodepleted donor-derived T cells expressing an inducible human caspase 9 (iC9) had their disease effectively controlled by a single administration of a small-molecule drug (AP1903) that dimerizes and activates the iC9 transgene. We now report the long-term follow-up of 10 patients infused with such safety switch-modified T cells. We find long-term persistence of iC9-modified (iC9-T) T cells in vivo in the absence of emerging oligoclonality and a robust immunologic benefit, mediated initially by the infused cells themselves and subsequently by an apparently accelerated reconstitution of endogenous naive T lymphocytes. As a consequence, these patients have immediate and sustained protection from major pathogens, including cytomegalovirus, adenovirus, BK virus, and Epstein-Barr virus in the absence of acute or chronic GvHD, supporting the beneficial effects of this approach to immune reconstitution after haplo-HSCT. This study was registered at www.clinicaltrials.gov as #NCT00710892.

Risk assessment before allogeneic hematopoietic cell transplantation for older adults with acute myeloid leukemia

Acute myeloid leukemia (AML) most commonly affects patients older than 60 years. Outcomes of treatment of older AML patients have been poor. The advent of reduced-intensity conditioning (RIC) regimens made allogeneic hematopoietic cell transplantation (HCT) an available treatment option with curative intent for older AML patients. Because older patients are often excluded from clinical trials, little is known about the stratification of their risks before allogeneic HCT. While recent studies of RIC and allogeneic HCT have shown little impact of age on outcomes, other variables such as the recipient health status and the AML disease status and chromosomal aberrations have proven to be of prognostic significance. Here, the authors review recent studies of allogeneic HCT for older patients with AML with detailed evaluation of risk factors for relapse as well as non-relapse mortality. The authors have integrated the currently available information on transplant risks into a five-category risk-benefit system that could aid in the decision-making in this patient population.

Haploidentical stem cell transplantation in two children with mucopolysaccharidosis VI: clinical and biochemical outcome

BACKGROUND

Mucopolysaccharidosis VI (MPS VI) is an autosomal recessive progressive multiorgan disorder due to mutation in the gene encoding the enzyme Arylsulfatase B (ARSB). Dysfunctional ARSB causes lysosomal accumulation of glycosaminoglycans (GAG). Currently, enzyme replacement therapy (ERT) is preferred to hematopoietic stem cell transplantation (SCT) due to the treatment-related risks of the latter. However, ERT constitutes an expensive life-long treatment. Increased experience and safety of SCT-procedures in recent years suggest that SCT should be further explored as a treatment option.This is the first report on haploidentical SCT in patients with MPS VI. The primary objective was to assess the treatment safety and clinical and biochemical outcome.

PATIENTS AND METHODS

Two siblings diagnosed with MPS VI at 10 months of age and at birth with genotype p.C192R, reported as mild to intermediate phenotype, underwent unrelated umbilical cord blood transplantation pre-symptomatic. Due to graft failure, both patients were urgently re-transplantated with haploidentical SCT with the father as donor. Continuous clinical and biochemical status was monitored and concluded 3.8 and 4.6 years after the haploidentical SCT.

RESULTS

Haploidentical SCT resulted in prompt and sustained engraftment. Complete donor chimerism was achieved in both patients, apart from mixed B cells chimerism in patient 2. ARSB activity in leukocytes post transplant increased from 0.0 to 19.0 μkat/kg protein (patient 1) and from 3.6 to 17.9 μkat/kg protein (patient 2) (ref. 17-40). Total urinary GAG normalized in both patients, although patient 2's values slightly exceed normal range since 6 months. However, dermatan sulfaturia was substantially normalized since 16 months and 12 months post-SCT, respectively. Height was -1.85 SD and -1.27 SD at follow-up. Patient 1 had impaired visual acuity and discrete hepatomegaly. Patient 2 had elevated intraocular pressure and X-ray revealed steep acetabular angles and slightly flattened lumbar vertebrae.

CONCLUSION

This study demonstrates that young children with MPS VI tolerate haploidentical SCT. Normalization of enzyme production and dermatan sulfaturia indicates correction of the inborn error of metabolism and coincide with no obvious symptoms of progressive MPS VI up to 4.6 years post-SCT.