Autologous and allogeneic stem cell transplantations for poor-risk chronic lymphocytic leukemia

T-cell dysfunction in CLL is mediated through expression of Siglec-10 ligands CD24 and CD52 on CLL cells

ABSTRACT

Autologous T-cell-based therapies, such as chimeric antigen receptor (CAR) T-cell therapy, exhibit low success rates in chronic lymphocytic leukemia (CLL) and correlate with a dysfunctional T-cell phenotype observed in patients. Despite various proposed mechanisms of T-cell dysfunction in CLL, the specific CLL-derived factors responsible remain unidentified. This study aimed to investigate the mechanisms through which CLL cells suppress CAR T-cell activation and function. We found that CLL-derived T cells get activated, albeit in a delayed fashion, and specifically that restimulation of CAR T cells in the presence of CLL cells causes impaired cytokine production and reduced proliferation. Notably, coculture of T cells with CD40-activated CLL cells did not lead to T-cell dysfunction, and this required direct cell contact between the CD40-stimulated CLL cells and T cells. Inhibition of kinases involved in the CD40 signaling cascade revealed that the Spare Respiratory Capacity (SRC) kinase inhibitor dasatinib prevented rescue of T-cell function independent of CD40-mediated increased levels of costimulatory and adhesion ligands on CLL cells. Transcriptome profiling of CD40-stimulated CLL cells with or without dasatinib identified widespread differential gene expression. Selecting for surface receptor genes revealed CD40-mediated downregulation of the Sialic acid-binding Ig-like lectin 10 (Siglec-10) ligands CD24 and CD52, which was prevented by dasatinib, suggesting a role for these ligands in functional T-cell suppression in CLL. Indeed, blocking CD24 and/or CD52 markedly reduced CAR T-cell dysfunction upon coculture with resting CLL cells. These results demonstrated that T cells derived from CLL patients can be reinvigorated by manipulating CLL-T-cell interactions. Targeting CD24- and CD52-mediated CLL-T-cell interaction could be a promising therapeutic strategy to enhance T-cell function in CLL.

iVAC-XS15-CLL01: personalized multi-peptide vaccination in combination with the TLR1/2 ligand XS15 in CLL patients undergoing BTK-inhibitor-based regimens

Chronic lymphocytic leukemia (CLL) is the most common form of leukemia among adults in Western countries. Despite the introduction of targeted therapies, including first-line Bruton's tyrosine kinase inhibitor (BTKi) treatment, CLL remains largely incurable. Frequent disease relapses occur due to remaining treatment-resistant CLL cells, calling for novel therapies to eliminate minimal residual disease (MRD). Peptide-based vaccination targeting human leucocyte antigen (HLA)-presented CLL-associated antigens represents a promising, low-side-effect therapeutic option to optimize treatment responses and eliminate residual tumor cells by inducing an anti-leukemic immune response. The iVAC-XS15-CLL01 trial is an open-label, first-in-human (FIH) Phase I trial, evaluating the CLL-VAC-XS15 vaccine in CLL patients undergoing BTKi-based therapy. The vaccine was developed from HLA-presented CLL-associated antigen peptides, identified through comparative mass-spectrometry-based immunopeptidome analyses of CLL versus healthy samples in a previous study. To facilitate rapid and cost-effective deployment, vaccine peptides are selected for each patient from a pre-manufactured "peptide warehouse" based on the patient's individual HLA allotype and CLL immunopeptidome. The trial enrolls 20 CLL patients, who receive up to three doses of the vaccine, adjuvanted with the toll-like-receptor (TLR) 1/2 ligand XS15 and emulsified in Montanide ISA 51 VG. The primary objective of the iVAC-XS15-CLL01 trial is to assess the safety and immunogenicity of the CLL-VAC-XS15 vaccine. Secondary objectives are to evaluate the vaccine impact on MRD, progression-free survival, and overall survival, as well as comprehensive immunophenotyping to characterize vaccine-induced T-cell responses. This Phase I trial aims to advance CLL treatment by enhancing immune-mediated disease clearance and guiding the design of subsequent Phase II/III trials to implement a new therapeutic strategy for CLL patients.

Holding the therapy in CLLp53: mechanisms to achieve durable responses

Chronic lymphocytic leukemia (CLL) is a common leukemia, mainly affecting the elderly. Originating in the bone marrow, CLL involves the accumulation of B lymphocytes and progresses slowly, though 50-60% of patients will require therapy. At diagnosis, the presence of p53 protein aberrations, such as 17p deletion and TP53 mutation, arises in approximately one out of 10 patients. Even in the era of targeted therapies, these aberrations remain the most important prognostic factors. Current guidelines favor continuous BTK inhibitor therapy in patients with CLLp53, though adverse events and drug resistance may lead to discontinuation. Herein, we discuss the effects of B-cell receptor and BCL-2 inhibition, as well as the role of the immune system, in two elderly CLLp53 patients with prolonged responses to different therapies.

The maintenance mechanism of hematopoietic stem cell dormancy: role for a subset of macrophages

Hematopoiesis is regulated by crosstalk between long-term repopulating hematopoietic stem cells (LT-HSCs) and supporting niche cells in the bone marrow (BM). Here, we describe the role of KAI1, which is mainly expressed on LT-HSCs and rarely on other hematopoietic stem-progenitor cells (HSPCs), in nichemediated LT-HSC maintenance. KAI1 activates TGF-β1/Smad3 signal in LT-HSCs, leading to the induction of CDK inhibitors and inhibition of the cell cycle. The KAI1-binding partner DARC is expressed on macrophages and stabilizes KAI1 on LT-HSCs, promoting their quiescence. Conversely, when DARC+ BM macrophages were absent, the level of surface KAI1 on LT-HSCs decreases, leading to cell-cycle entry, proliferation, and differentiation. Thus, KAI1 acts as a functional surface marker of LTHSCs that regulates dormancy through interaction with DARCexpressing macrophages in the BM stem cell niche. Recently, we showed very special and rare macrophages expressing α-SMA+ COX2+ & DARC+ induce not only dormancy of LTHSC through interaction of KAI1-DARC but also protect HSCs by down-regulating ROS through COX2 signaling. In the near future, the strategy to combine KAI1-positive LT-HSCs and α-SMA/Cox2/DARC triple-positive macrophages will improve the efficacy of stem cell transplantation after the ablative chemo-therapy for hematological disorders including leukemia. [BMB Reports 2023; 56(9): 482-487].

Current state of NK cell-mediated immunotherapy in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) has become one of the most common hematological diseases in western countries, with an annual incidence of 42/100,000. Conventional chemotherapy and targeted therapeutic drugs showed limitations in prognosis or in efficiency in high-risk patients. Immunotherapy represented is one of the most effective therapeutic approaches with the potential of better effect and prognosis. Natural killer (NK) cells are good options for immunotherapy as they can effectively mediate anti-tumor activity of immune system by expressing activating and inhibiting receptors and recognizing specific ligands on various tumor cells. NK cells are critical in the immunotherapy of CLL by enhancing self-mediated antibody-dependent cytotoxicity (ADCC), allogeneic NK cell therapy and chimeric antigen receptor-natural killer (CAR-NK) cell therapy. In this article, we reviewed the features, working mechanisms, and receptors of NK cells, and the available evidence of the advantages and disadvantages of NK cell-based immunotherapies, and put forward future study directions in this field.

Immunopeptidome Diversity in Chronic Lymphocytic Leukemia Identifies Patients with Favorable Disease Outcome

Simple Summary

Immunosurveillance of cancer is mediated by T cell-based recognition of tumor-associated antigens, i.e., short peptides that are presented on the surface of cells on human leukocyte antigen (HLA) molecules. This encourages the analysis of the entirety of HLA-presented peptides, the so-called immunopeptidome, of malignant and benign cells, in order to identify novel therapeutic targets presented exclusively on malignant cells. In the present study, we aim to investigate the role of previously described immunopeptidome-defined antigen presentation in chronic lymphocytic leukemia (CLL) patients for clinical characteristics and disease outcome. We observed that higher yields of presented total and CLL-exclusive peptides were associated with a more favorable disease course, suggesting efficient immunosurveillance in a subgroup of patients and the possibility of further investigating T cell-based therapeutic approaches for CLL.

Abstract

Chronic lymphocytic leukemia (CLL) is characterized by recurrent relapses and resistance to treatment, even with novel therapeutic approaches. Despite being considered as a disease with low mutational burden and thus poor immunogenic, CLL seems to retain the ability of eliciting specific T cell activation. Accordingly, we recently found non-mutated tumor-associated antigens to play a central role in CLL immunosurveillance. Here, we investigated the association of total and CLL-exclusive HLA class I and HLA class II peptide presentation in the mass spectrometry-defined immunopeptidome of leukemic cells with clinical features and disease outcome of 57 CLL patients. Patients whose CLL cells present a more diverse immunopeptidome experienced fewer relapses. During the follow-up phase of up to 10 years, patients with an HLA class I-restricted presentation of high numbers of total and CLL-exclusive peptides on their malignant cells showed a more favorable disease course with a prolonged progression-free survival (PFS). Overall, our results suggest the existence of an efficient T cell-based immunosurveillance mediated by CLL-associated tumor antigens, supporting ongoing efforts in developing T cell-based immunotherapeutic strategies for CLL.

Immunotherapeutic Strategies in Chronic Lymphocytic Leukemia: Advances and Challenges

Immune-based therapeutic strategies have drastically changed the landscape of hematological disorders, as they have introduced the concept of boosting immune responses against tumor cells. Anti-CD20 monoclonal antibodies have been the first form of immunotherapy successfully applied in the treatment of CLL, in the context of chemoimmunotherapy regimens. Since then, several immunotherapeutic approaches have been studied in CLL settings, with the aim of exploiting or eliciting anti-tumor immune responses against leukemia cells. Unfortunately, despite initial promising data, results from pilot clinical studies have not shown optimal results in terms of disease control - especially when immunotherapy was used individually - largely due to CLL-related immune dysfunctions hampering the achievement of effective anti-tumor responses. The growing understanding of the complex interactions between immune cells and the tumor cells has paved the way for the development of new combined approaches that rely on the synergism between novel agents and immunotherapy. In this review, we provide an overview of the most successful and promising immunotherapeutic modalities in CLL, including both antibody-based therapy (i.e. monoclonal antibodies, bispecific antibodies, bi- or tri- specific killer engagers) and adoptive cellular therapy (i.e. CAR T cells and NK cells). We also provide examples of successful new combination strategies and some insights on future perspectives.

Immunopeptidomics-Guided Warehouse Design for Peptide-Based Immunotherapy in Chronic Lymphocytic Leukemia

Antigen-specific immunotherapies, in particular peptide vaccines, depend on the recognition of naturally presented antigens derived from mutated and unmutated gene products on human leukocyte antigens, and represent a promising low-side-effect concept for cancer treatment. So far, the broad application of peptide vaccines in cancer patients is hampered by challenges of time- and cost-intensive personalized vaccine design, and the lack of neoepitopes from tumor-specific mutations, especially in low-mutational burden malignancies. In this study, we developed an immunopeptidome-guided workflow for the design of tumor-associated off-the-shelf peptide warehouses for broadly applicable personalized therapeutics. Comparative mass spectrometry-based immunopeptidome analyses of primary chronic lymphocytic leukemia (CLL) samples, as representative example of low-mutational burden tumor entities, and a dataset of benign tissue samples enabled the identification of high-frequent non-mutated CLL-associated antigens. These antigens were further shown to be recognized by pre-existing and de novo induced T cells in CLL patients and healthy volunteers, and were evaluated as pre-manufactured warehouse for the construction of personalized multi-peptide vaccines in a first clinical trial for CLL (NCT04688385). This workflow for the design of peptide warehouses is easily transferable to other tumor entities and can provide the foundation for the development of broad personalized T cell-based immunotherapy approaches.

NK Cells in Chronic Lymphocytic Leukemia and Their Therapeutic Implications

Key features of chronic lymphocytic leukemia (CLL) are defects in the immune system and the ability of leukemic cells to evade immune defenses and induce immunosuppression, resulting in increased susceptibility to infections and disease progression. Several immune effectors are impaired in CLL, including T and natural killer (NK) cells. The role of T cells in defense against CLL and in CLL progression and immunotherapy has been extensively studied. Less is known about the role of NK cells in this leukemia, and data on NK cell alterations in CLL are contrasting. Besides studies showing that NK cells have intrinsic defects in CLL, there is a large body of evidence indicating that NK cell dysfunctions in CLL mainly depend on the escape mechanisms employed by leukemic cells. In keeping, it has been shown that NK cell functions, including antibody-dependent cellular cytotoxicity (ADCC), can be retained and/or restored after adequate stimulation. Therefore, due to their preserved ADCC function and the reversibility of CLL-related dysfunctions, NK cells are an attractive source for novel immunotherapeutic strategies in this disease, including chimeric antigen receptor (CAR) therapy. Recently, satisfying clinical responses have been obtained in CLL patients using cord blood-derived CAR-NK cells, opening new possibilities for further exploring NK cells in the immunotherapy of CLL. However, notwithstanding the promising results of this clinical trial, more evidence is needed to fully understand whether and in which CLL cases NK cell-based immunotherapy may represent a valid, alternative/additional therapeutic option for this leukemia. In this review, we provide an overview of the current knowledge about phenotypic and functional alterations of NK cells in CLL and the mechanisms by which CLL cells circumvent NK cell-mediated immunosurveillance. Additionally, we discuss the potential relevance of using NK cells in CLL immunotherapy.

CD3xCD19 DART molecule treatment induces non-apoptotic killing and is efficient against high-risk chemotherapy and venetoclax-resistant chronic lymphocytic leukemia cells

BACKGROUND

Bispecific antibodies are promising new therapeutics in B cell malignancies. Whether they lead to potent T cell activation despite described T cell dysfunction in chronic lymphocytic leukemia (CLL), and are able to effectively target high-risk or venetoclax-resistant samples, is currently unknown.

METHODS

CD19⁺ cell lines or primary (high-risk) CLL were cocultured in vitro with healthy donor (HD) or CLL-derived T cells in the presence of a CD3xCD19 dual affinity retargeting molecule (CD3xCD19 DART). Cell cytotoxicity, T cell activation, proliferation and effector molecule production were analyzed using flow cytometry.

RESULTS

Here, we report that a bispecific CD3xCD19 DART mediates efficient killing by HD T cells of CD19⁺ cell-lines and primary CLL cells, regardless of immunoglobulin heavy chain variable region (IGHV) mutational status TP53 status or chemotherapy, ibrutinib or venetoclax sensitivity. Whereas TCR stimulation of CLL-derived T cells resulted in dysfunctional T cell activation and proliferation, treatment with CD3xCD19 DART led to a similar activation profile in CLL-derived and HD-derived T cells. Consistently, co-culture of CLL derived T cells with JeKo-1 or CLL cells in the presence of CD3xCD19 DART resulted in significant cytotoxicity by both CD4⁺ and CD8⁺ T cells. On stimulation of CLL cells with CD40L, CLL cells become resistant to the specific inhibitor of anti-apoptotic Bcl-2 protein venetoclax, due to upregulation of Bcl-2 family members such as Bcl-XL. Nevertheless, CD40L stimulated CLL cells were as efficiently lysed on CD3xCD19 DART treatment as unstimulated CLL cells. Further examination of the mechanism of CD3xCD19 DART mediated killing showed that lysis was dependent on granules, but was independent of BAX/BAK or caspase activity, indicating non-apoptotic cell death.

CONCLUSIONS

These data show that CD3xCD19 DART in CLL leads to robust T cell activation and lysis of high-risk venetoclax resistant CLL cells through a non-apoptotic mechanism.

Chronic lymphocytic leukemia cells impair mitochondrial fitness in CD8+ T cells and impede CAR T-cell efficacy

In chronic lymphocytic leukemia (CLL), acquired T-cell dysfunction impedes development of effective immunotherapeutic strategies, through as-yet unresolved mechanisms. We have previously shown that CD8+ T cells in CLL exhibit impaired activation and reduced glucose uptake after stimulation. CD8+ T cells in CLL patients are chronically exposed to leukemic B cells, which potentially impacts metabolic homeostasis resulting in aberrant metabolic reprogramming upon stimulation. Here, we report that resting CD8+ T cells in CLL have reduced intracellular glucose transporter 1 (GLUT1) reserves, and have an altered mitochondrial metabolic profile as displayed by increased mitochondrial respiration, membrane potential, and levels of reactive oxygen species. This coincided with decreased levels of peroxisome proliferator-activated receptor γ coactivator 1-α, and in line with that, CLL-derived CD8+ T cells showed impaired mitochondrial biogenesis upon stimulation. In search of a therapeutic correlate of these findings, we analyzed mitochondrial biogenesis in CD19-directed chimeric antigen receptor (CAR) CD8+ T cells prior to infusion in CLL patients (who were enrolled in NCT01747486 and NCT01029366 [https://clinicaltrials.gov]). Interestingly, in cases with a subsequent complete response, the infused CD8+ CAR T cells had increased mitochondrial mass compared with nonresponders, which positively correlated with the expansion and persistence of CAR T cells. Our findings demonstrate that GLUT1 reserves and mitochondrial fitness of CD8+ T cells are impaired in CLL. Therefore, boosting mitochondrial biogenesis in CAR T cells might improve the efficacy of CAR T-cell therapy and other emerging cellular immunotherapies.

How and when I do allogeneic transplant in CLL

Allogenic stem cell transplantation (allo-SCT) has been considered the treatment of choice for high-risk patients with chronic lymphocytic leukemia (CLL) and the only approach offered with curative intent in this disease. The availability novel agents, including the B-cell receptor inhibitors ibrutinib, acalabrutinib, and idelalisib, as well as venetoclax, which targets the BCL2 pathway, and the success of these agents in treating high-risk disease patients have made it more difficult to assess who should be considered for allo-SCT and when in the treatment course. In this review, I will discuss the different treatment options available for the treatment of high-risk CLL and how allo-SCT fits into the treatment algorithm in the era of novel agents.

HLA ligandome analysis of primary chronic lymphocytic leukemia (CLL) cells under lenalidomide treatment confirms the suitability of lenalidomide for combination with T-cell-based immunotherapy

Recent studies suggest that CLL is an immunogenic disease, which might be effectively targeted by antigen-specific T-cell-based immunotherapy. However, CLL is associated with a profound immune defect, which might represent a critical limitation for mounting clinically effective antitumor immune responses. As several studies have demonstrated that lenalidomide can reinforce effector T-cell responses in CLL, the combination of T-cell-based immunotherapy with the immunomodulatory drug lenalidomide represents a promising approach to overcome the immunosuppressive state in CLL. Antigen-specific immunotherapy also requires the robust presentation of tumor-associated HLA-presented antigens on target cells. We thus performed a longitudinal study of the effect of lenalidomide on the HLA ligandome of primary CLL cells in vitro. We showed that lenalidomide exposure does not affect absolute HLA class I and II surface expression levels on primary CLL cells. Importantly, semi-quantitative mass spectrometric analyses of the HLA peptidome of three CLL patient samples found only minor qualitative and quantitative effects of lenalidomide on HLA class I- and II-restricted peptide presentation. Furthermore, we confirmed stable presentation of previously described CLL-associated antigens under lenalidomide treatment. Strikingly, among the few HLA ligands showing significant modulation under lenalidomide treatment, we identified upregulated IKZF-derived peptides, which may represent a direct reflection of the cereblon-mediated effect of lenalidomide on CLL cells. Since we could not observe any relevant influence of lenalidomide on the established CLL-associated antigen targets of anticancer T-cell responses, this study validates the suitability of lenalidomide for the combination with antigen-specific T-cell-based immunotherapies.

Reduced intensity is preferred over myeloablative conditioning allogeneic HCT in chronic lymphocytic leukemia whenever indicated: A systematic review/meta-analysis

Despite availability of new and more effective therapies for chronic lymphocytic leukemia, presently this disease remains incurable unless eligible patients are offered an allogeneic hematopoietic cell transplant. Recent published clinical practice recommendations on behalf of the American Society for Blood and Marrow Transplantation relegated the role of for allogeneic hematopoietic cell transplantation to later stages of the disease. To our knowledge, no randomized controlled trial has been performed to date comparing myeloablative versus reduced intensity conditioning regimens in chronic lymphocytic leukemia patients eligible for the procedure. We performed a systematic review/meta-analysis to assess the efficacy of allogeneic hematopoietic cell transplantation when using myeloablative or reduced intensity conditioning regimens. We report the results in accordance to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Based on lower non-relapse mortality and slightly better overall survival rates, reduced intensity conditioning regimens appear to be the most desirable choice whenever the procedure is indicated for this disease. It appears highly unlikely that a RCT will be ever performed comparing reduced intensity vs. myeloablative allogeneic hematopoietic cell transplantation in chronic lymphocytic leukemia. In the absence of such a study, results of this systematic review/meta-analysis represent the best available evidence supporting this recommendation whenever indicated in patients with chronic lymphocytic leukemia.

[Allogeneic haematopoietic cell transplantation for indolent lymphomas: Guidelines from the Francophone Society Bone Marrow Transplantation and Cellular Therapy (SFGM-TC)]

Despite great improvements in the outcome of patients with lymphoma, some may still relapse or present with primary refractory disease. In these situations, allogeneic hematopoietic cell transplantation is a potentially curative option, this is true particularly the case of relapse after autologous stem cell transplantation. Recently, novel agents such as anti-PD1 and BTK inhibitors have started to challenge the use of allogeneic hematopoietic cell transplantation for relapsed or refractory lymphoma. During the 2016 annual workshop of the Francophone Society of Bone Marrow Transplantation and Cellular Therapy (SFGM-TC), we performed a comprehensive review of the literature published in the last 10 years and established guidelines to clarify the indications and transplant modalities in this setting. This paper specifically reports on our conclusions regarding indolent lymphomas, mainly follicular lymphoma and chronic lymphocytic leukemia.

Chimeric Antigen Receptor T-Cell Therapy for Chronic Lymphocytic Leukemia: A Narrative Review

The treatment landscape for chronic lymphocytic leukemia (CLL) is changing rapidly. Novel targeted agents such as ibrutinib, venetoclax, and idelalisib have had a significant effect on first-line, relapsed/refractory, and high-risk disease. Despite these advances, there are continuous needs for new treatment options, especially for patients in whom these novel therapies fail or those who cannot tolerate these novel therapies. In 2011, Porter et al reported the first successful use of autologous chimeric antigen receptor T cells (CARTs) directed against cluster of differentiation (CD)19 in 3 refractory CLL patients. Several groups have since shown success with similar approaches in various settings of CLL, including failure of ibrutinib treatment and in patients who relapse after allogeneic stem cell transplantation. Although CD19-directed CART therapy holds great promise in CLL and other diseases, many challenges and questions remain including: optimization of the lymphodepletion regimen before CART infusion, optimal dosing of CART, a determination of the most effective CART product (T-cell subset[s]) as well as the optimal combinations and therapeutic sequences, and managing treatment-associated adverse events. Clinical trials addressing these challenges are in process. In this timely review, we analyze current state of CART therapy in CLL and attempt answering remaining questions.

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.

Trends in survival of chronic lymphocytic leukemia patients in Germany and the USA in the first decade of the twenty-first century

Background

Recent population-based studies in the United States of America (USA) and other countries have shown improvements in survival for patients with chronic lymphocytic leukemia (CLL) diagnosed in the early twenty-first century. Here, we examine the survival for patients diagnosed with CLL in Germany in 1997–2011.

Methods

Data were extracted from 12 cancer registries in Germany and compared to the data from the USA. Period analysis was used to estimate 5- and 10-year relative survival (RS).

Results

Five- and 10-year RS estimates in 2009–2011 of 80.2 and 59.5 %, respectively, in Germany and 82.4 and 64.7 %, respectively, in the USA were observed. Overall, 5-year RS increased significantly in Germany and the difference compared to the survival in the USA which slightly decreased between 2003–2005 and 2009–2011. However, age-specific analyses showed persistently higher survival for all ages except for 15–44 in the USA. In general, survival decreased with age, but the age-related disparity was small for patients younger than 75. In both countries, 5-year RS was >80 % for patients less than 75 years of age but <70 % for those age 75+.

Conclusions

Overall, 5-year survival for patients with CLL is good, but 10-year survival is significantly lower, and survival was much lower for those age 75+. Major differences in survival between countries were not observed. Further research into ways to increase survival for older CLL patients are needed to reduce the persistent large age-related survival disparity.

Management of chronic lymphocytic leukemia

Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL) is usually diagnosed in asymptomatic patients with early-stage disease. The standard management approach is careful observation, irrespective of risk factors unless patients meet the International Workshop on CLL (IWCLL) criteria for "active disease," which requires treatment. The initial standard therapy for most patients combines an anti-CD20 antibody (such as rituximab, ofatumumab, or obinutuzumab) with chemotherapy (fludarabine/cyclophosphamide [FC], bendamustine, or chlorambucil) depending on multiple factors including the physical fitness of the patient. However, patients with very high-risk CLL because of a 17p13 deletion (17p-) with or without mutation of TP53 (17p-/TP53mut) have poor responses to chemoimmunotherapy and require alternative treatment regimens containing B-cell receptor (BCR) signaling pathway inhibitors. The BCR signaling pathway inhibitors (ibrutinib targeting Bruton's tyrosine kinase [BTK] and idelalisib targeting phosphatidyl-inositol 3-kinase delta [PI3K-delta], respectively) are currently approved for the treatment of relapsed/refractory CLL and all patients with 17p- (ibrutinib), and in combination with rituximab for relapsed/refractory patients (idelalisib). These agents offer great efficacy, even in chemotherapy refractory CLL, with increased tolerability, safety, and survival. Ongoing studies aim to determine the best therapy combinations with the goal of achieving long-term disease control and the possibility of developing a curative regimen for some patients. CLL is associated with a wide range of infectious, autoimmune, and malignant complications. These complications result in considerable morbidity and mortality that can be minimized by early detection and aggressive management. This active monitoring requires ongoing patient education, provider vigilance, and a team approach to patient care.

Immunotherapy in Chronic Lymphocytic Leukaemia (CLL)

Chronic lymphocytic leukaemia (CLL) is well known to generate impaired immune responses in the host, with the malignant clone residing in well-vascularized tissues and circulating in peripheral blood but also in close proximity to effector cells that are capable, if activated appropriately, of eliciting a cytotoxic response. These, combined with the fact that this is frequently a condition affecting older patients with co-morbidities often unfit for many "traditional" cytotoxic agents with their significant associated toxicities, make CLL an ideal candidate for the development of immunotherapy. The impressive results seen with the addition of a monoclonal antibody, rituximab, to a chemotherapy backbone, for example, is testament to how effective harnessing an immune-mediated response in CLL can be. This review serves to outline the available arsenal of immunotherapies-past and present-demonstrated to have potential in CLL with some perspectives on how the landscape in this disease may evolve in the future.

Prognostic markers and standard management of chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is usually diagnosed in early stage, asymptomatic patients, and, although a wealth of prognostic parameters have been identified, the standard approach is a “watch and wait” strategy irrespective of risk factors. Therapy is only indicated if “active disease” criteria (International Workshop on Chronic Lymphocytic Leukemia guidelines) are met, and the routine upfront treatment is a combination of CD20 antibody (rituximab, ofatumumab or obinutuzumab) and chemotherapy (fludarabine /cyclophosphamide, bendamustine, chlorambucil), with the choice mainly determined by physical fitness of the patient. The major subgroup in which this approach does not result into satisfactory efficacy is in CLL with 17p deletion (17p−) or TP53 mutation (TP53mut). Likewise, patients with a short initial response duration (i.e., <24-26 months) have a dismal outcome with chemoimmunotherapy salvage. Therefore, these patients have been referred to as “ultra high risk,” and, in these subgroups, novel agents such as signaling kinase inhibitors (also termed B-cell receptor signaling inhibitors; e.g., ibrutinib targeting Bruton tryosine kinase, idelalisib targeting phosphoinositide 3-kinase) and BCL2 antagonists (venetoclax, formerly ABT-199/GDC-0199) have shown dramatic efficacy. Ibrutinib and idelalisib are currently approved for the treatment of relapsed or refractory CLL or frontline treatment of 17p−/TP53mut CLL regardless of fitness. Therefore, these agents are challenging the concept of adjusting treatment to fitness and TP53 status, because they offer remarkable efficacy combined with exceptional tolerability. Nevertheless, it appears that 17p−/TP53mut retains an adverse prognostic impact, making additional improvement a primary research goal aimed at the development of the best combinations and/or sequences of these new agents, as well as prognostic and predictive markers guiding their use.

The evolving role of hematopoietic cell transplantation in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) patients with high-risk markers such as del(17p) or those who have relapsed after multiple lines of therapy have a poor prognosis and allogeneic hematopoietic cell transplantation (alloHCT) has historically been the best opportunity for achieving long-term disease control. Recently, several new highly efficacious and well-tolerated small molecules targeting the B cell receptor (BCR) pathway and Bcl-2 have been approved or are in the late stages of development. These new agents are altering therapeutic paradigms in CLL, but unlike with alloHCT, information on long-term disease control is lacking. Here, we provide an overview of the data supporting the use of HCT in CLL and the promising results with the novel agents. We discuss the evolving role of alloHCT for CLL in the novel agent era, including identifying the patients most likely to benefit from transplantation and optimal transplantation timing, as well the use of novel agents in the post-transplantation setting.

Outcomes for patients with chronic lymphocytic leukemia and acute leukemia or myelodysplastic syndrome

Acute leukemia (AL) and myelodysplastic syndrome (MDS) are uncommon in chronic lymphocytic leukemia (CLL). We retrospectively identified 95 patients with CLL, also diagnosed with AL (n=38) or MDS (n=57), either concurrently (n=5) or subsequent (n=90) to CLL diagnosis and report their outcomes. Median number of CLL treatments prior to AL and MDS was 2 (0-9) and 1 (0-8), respectively; the most common regimen was purine analog combined with alkylating agent±CD20 monoclonal antibody. Twelve cases had no prior CLL treatment. Among 38 cases with AL, 33 had acute myelogenous leukemia (AML), 3 had acute lymphoid leukemia (ALL; 1 Philadelphia chromosome positive), 1 had biphenotypic and 1 had extramedullary (bladder) AML. Unfavorable AML karyotype was noted in 26, and intermediate risk in 7 patients. There was no association between survival from AL and number of prior CLL regimens or karyotype. Expression of CD7 on blasts was associated with shorter survival. Among MDS cases, all International Prognostic Scoring System (IPSS) were represented; karyotype was unfavorable in 36, intermediate in 6 and favorable in 12 patients; 10 experienced transformation to AML. Shorter survival from MDS correlated with higher risk IPSS, poor-risk karyotype and increased number of prior CLL treatments. Overall, outcomes for patients with CLL subsequently diagnosed with AL or MDS were very poor; AL/MDS occurred without prior CLL treatment. Effective therapies for these patients are desperately needed.

Nonmyeloablative allogeneic stem cell transplantation for chronic lymphocytic leukaemia offers the possibility of disease control with minimal morbidity and mortality--a single institution experience

Allogeneic stem cell transplantation is a treatment option for patients with poor risk CLL. We conducted a retrospective analysis of all CLL patients allografted at our institution, the University Hospital of Cologne, Germany. Data was collected on 40 patients from 2004 to 2012. The mean age was 54, and the majority were male (75 %). On average, the patients were diagnosed 6 years (range 2-12) prior to transplant with an average of 4 years (range 1-8) from time of first-line therapy to transplant. The remission states at the time of transplant were complete remission (CR) (n = 4), stable disease (n = 10), partial remission (n = 20) and progressive disease (n = 6). Only reduced intensity conditioning regimens were employed. The average CD34(+) cell dose was 4.16 × 10(6)/kg. Neutrophil engraftment was seen by day +17 (range 10-23) post-transplant, and 88 % achieved 95-100 % donor chimerism by day 100. Overall survival, progression-free survival and non-relapse mortality at 2 years post-transplant were 65, 52.5 and 27.5 %, respectively. A total of 51 % of patients were found to be minimal residual disease (MRD)-negative at 1 year post-transplant. Our single-centre experience confirms the valuable role of allogeneic stem cell transplantation (allo-SCT) in the treatment of poor risk CLL patients with promising long-term survival and acceptable transplant-related mortality. The advent of newer therapeutic agents should not hinder the consideration of allo-SCT for this patient cohort as it remains the only curative option for these patients.

Outcomes of Patients With Chronic Lymphocytic Leukemia and Richter's Transformation After Transplantation Failure

PURPOSE

Allogeneic stem-cell transplantation (SCT) induces long-term remission in a fraction of patients with high-risk chronic lymphocytic leukemia (CLL) or Richter's transformation (RT). Our purpose was to determine the outcomes of patients whose disease progressed after allogeneic SCT.

PATIENTS AND METHODS

We retrospectively analyzed the outcomes of 72 patients (52 with CLL and 20 with RT) who underwent allogeneic SCT between 1998 and 2011 and had documented progression after transplantation. Twenty-two (31%) never had a response, and 50 (69%) had a response but experienced relapse after a median of 7 months (range, 2 to 85 months). Forty-eight patients who were receiving or were candidates to receive post-SCT cell-based therapies were not included in this analysis.

RESULTS

The median age at time of transplantation was 58 years (range, 30 to 72 years). Sixty-two patients (86%) received more than two treatment regimens and 37 (51%) received more than three treatment regimens before SCT. Sixty-six patients (92%) had active disease at the time of transplantation. The 2- and 5-year survival rates were 67% and 38% (patients with CLL) and 36% and 0% (patients with RT). The patients who developed acute or chronic graft-versus-host disease had a longer overall survival (OS; P = .05). In a multivariable analysis, RT or low hemoglobin at the time of SCT predicted shorter OS. Chronic graft-versus-host disease and an initial response to SCT predicted longer OS.

CONCLUSION

Patients with CLL in whom allogeneic SCT fails may have a response to and benefit from salvage therapies, and their prognosis is relatively good.

Chronic lymphocytic leukemia/small lymphocytic lymphoma, version 1.2015

Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) are different manifestations of the same disease, which are managed in the same way. The advent of novel monoclonal antibodies (ofatumumab and obinutuzumab) led to the development of effective chemoimmunotherapy regimens. The recently approved small molecule kinase inhibitors (ibrutinib and idelalisib) are effective treatment options for CLL in elderly patients with decreased tolerance for aggressive regimens and in patients with poor prognostic features who do not benefit from conventional chemoimmunotherapy regimens. This portion of the NCCN Guidelines for Non-Hodgkin's Lymphomas describes the recent specific to the incorporation of recently approved targeted therapies for the management of patients with newly diagnosed and relapsed or refractory CLL/SLL.

HLA ligandome analysis identifies the underlying specificities of spontaneous antileukemia immune responses in chronic lymphocytic leukemia (CLL)

The breakthrough development of clinically effective immune checkpoint inhibitors illustrates the potential of T-cell-based immunotherapy to effectively treat malignancies. A remaining challenge is to increase and guide the specificities of anticancer immune responses, e.g., by therapeutic vaccination or by adoptive T-cell transfer. By analyzing the landscape of naturally presented HLA class I and II ligands of primary chronic lymphocytic leukemia (CLL), we delineated a novel category of tumor-associated T-cell antigens based on their exclusive and frequent representation in the HLA ligandome of leukemic cells. These antigens were validated across different stages and mutational subtypes of CLL and found to be robustly represented in HLA ligandomes of patients undergoing standard chemo-/immunotherapy. We demonstrate specific immune recognition of these antigens exclusively in CLL patients, with the frequencies of representation in CLL ligandomes correlating with the frequencies of immune recognition by patient T cells. Moreover, retrospective survival analysis revealed survival benefits for patients displaying immune responses to these antigens. These results directly imply these nonmutant self-peptides as pathophysiologically relevant tumor antigens and encourages their implementation for cancer immunotherapy.

Managing high-risk CLL during transition to a new treatment era: stem cell transplantation or novel agents?

Allogeneic hematopoietic stem cell transplantation (HSCT) has been considered as the treatment of choice for patients with high-risk chronic lymphocytic leukemia (HR-CLL; ie, refractory to purine analogs, short response [<24 months] to chemoimmunotherapy, and/or presence of del[17p]/TP53 mutations). Currently, treatment algorithms for HR-CLL are being challenged by the introduction of novel classes of drugs. Among them, BCR signal inhibitors (BCRi) and B-cell lymphoma 2 antagonists (BCL2a) appear particularly promising. As a result of the growing body of favorable outcome data reported for BCRi/BCL2a, uncertainty is emerging on how to advise patients with HR-CLL about indication for and timing of HSCT. This article provides an overview of currently available evidence and theoretical considerations to guide this difficult decision process. Until the risks and benefits of different treatment strategies are settled, all patients with HR-CLL should be considered for treatment with BCRi/BCL2a. For patients who respond to these agents, there are 2 treatment possibilities: (1) performing an HSCT or (2) continuing treatment with the novel drug. Individual disease-specific and transplant-related risk factors, along with patient's preferences, should be taken into account when recommending one of these treatments over the other.

Paradigm shifts in the management of poor-risk chronic lymphocytic leukemia

With the growing complexity of treatment options for chronic lymphocytic leukemia (CLL) and variables that influence the underlying biology of this disease, providing allogeneic stem cell transplant (alloSCT) to appropriate candidates poses a challenge for transplant physicians. Novel small molecule inhibitors hold unprecedented promise for poor-risk subgroups, which will likely alter decision-making and referral patterns for transplant. In this review, we analyze what is known and may still remain true about indications for transplant based on outcomes reported in the literature recently and over the last decade.

Role of allogeneic transplantation in patients with chronic lymphocytic leukemia in the era of novel therapies: a review

Chronic lymphocytic leukemia (CLL) is the most common form of adult leukemia and is characterized by a highly variable clinical course. In the past decade, several prognostic risk factors have been identified facilitating the classification of CLL into various risk groups. Patients with poor risk disease, such as poor cytogenetics or relapsing after purine-based analogues, had limited therapeutic options, with allogeneic hematopoietic cell transplantation (allo-SCT) the only known therapy with curative potential. More recently, the introduction of novel agents inhibiting the B-cell receptor pathway, and the early success with chimeric antigen receptor T cells offers an effective and relatively safe option for this poor prognostic group which holds promise in the future. Alternatively, the use of reduced intensity conditioning regimens in the allo-SCT setting has led to a significant decrease in nonrelapse mortality to 16-23%, making it an attractive therapeutic option. No recent guidelines have been developed since these novel therapies became available regarding the optimal time to allo-SCT in this patient population. The advent of these novel and highly active therapeutic agents, therefore, warrants a reappraisal of the role and timing of allo-SCT in patients with CLL. In this article, we summarize the literature regarding the novel therapeutic agents available today as well as focus on the efficacy and safety of allo-SCT.

Transplantation in chronic lymphocytic leukemia: does it still matter in the era of novel targeted therapies?

Allogeneic stem cell transplantation (HSCT) offers the only potentially curative approach in chronic lymphocytic leukemia (CLL). However, this applies only to a minority of patients, and is associated with significant treatment-related mortality and morbidity. HSCT must therefore always be considered in view of other, potentially less toxic therapies. Several new agents demonstrate impressive and durable responses in high-risk patients who might be candidates for HSCT. Therefore the choice of HSCT versus a novel agent is one that must be gauged on a patient-by-patient basis; this will change as data mature on the use of these novel agents in CLL.

Genomic aberrations deletion 11q and deletion 17p independently predict for worse progression-free and overall survival after allogeneic hematopoietic cell transplantation for chronic lymphocytic leukemia

Chronic lymphocytic leukemia remains incurable despite availability of potent chemoimmunotherapy regimens. Allogeneic hematopoietic cell transplantation (HCT) is the only modality that offers the possibility of cure. To identify predictors of progression-free and overall survival, we evaluated outcomes of 43 consecutive patients who received an allograft for advanced CLL. The majority received a reduced intensity conditioning regimen (n=37). Donors were HLA matched-related (n=18), matched-unrelated (n=15), mismatched-unrelated (n=7), or umbilical cord blood (n=3). The median progression-free (PFS) and overall survival (OS) were 31.4 months and 46.4 months respectively. Twenty (46.5%) patients were alive and in complete remission at a median follow-up of 31.4 months. NRM was higher than previously published series for CLL, likely due to a high burden of comorbidity (22 patients with HCT-CI ≥ 2) and a high proportion receiving HLA mismatched-unrelated donor or umbilical cord blood cells. Presence of del (11q), del(17p), or progressive disease at HCT are independent predictors of worse PFS and OS. New strategies are needed to improve survival outcomes in CLL associated with poor risk cytogenetics.

Low tumor burden is associated with early B-cell reconstitution and is a predictor of favorable outcome after non-myeloablative stem cell transplant for chronic lymphocytic leukemia

Abstract Reconstitution, engraftment kinetics and tumor cell clearance were analyzed after reduced intensity conditioning hematopoietic cell transplant (RIC-HCT) in patients with chronic lymphocytic leukemia (CLL). Patients were transplanted from unrelated (n = 40) or related (n = 10) donors after fludarabine and 2 Gy total body irradiation followed by cyclosporine and mycophenolate mofetil. The vast majority of patients (96%) engrafted with absolute neutrophil count (ANC) > 0.5 × 10(9)/L at day + 22. CLL cells decreased (median 2%, range 0-69%) within 28 days, but disappeared by day + 180 after HCT. Donor T-cell chimerism increased to > 95% at day 56 and donor B-cell chimerism to 94% at day + 360. Overall survival was 51 ± 8%, incidence of progression 37 ± 7% and non-relapse related mortality (NRM) 30 ± 7% at 4 years. The most common causes of NRM were graft-versus-host disease (GvHD) (14%) and sepsis (6%). Disease status at HCT was significantly associated with early B-cell reconstitution (p = 0.04) and with increased risk of relapse/progression in univariate and multivariate analysis (p = 0.022). Tumor cells were undetectable by day + 180, although B-cell reconstitution did not occur until 1.5 years after RIC-HCT. The best predictors for progression-free survival (PFS) and overall survival (OS) were complete response (CR) or first partial response (PR1) and the absence of bulky disease at transplant, respectively.

17p deletion in chronic lymphocytic leukemia: risk stratification and therapeutic approach

Treatment of chronic lymphocytic leukemia has greatly advanced in the past few years since introduction of the fludarabine/cyclosphosphamide/rituximab regimen as first-line therapy. Nevertheless, 17p deletion represents a challenge because conventional treatment does not provide satisfactory results. 17p deletion and TP53 mutation are the major factors accounting for rapid disease progression, poor response to therapy, early relapse, and short survival. Allogeneic stem cell transplantation harbors curative potential but also considerable morbidity and mortality. Novel agents acting independently of the p53 signaling pathway, with favorable side-effect profiles, are promising. This review summarizes up-to-date knowledge about 17p deletion and the spectrum of treatment options.

Unrelated donor allogeneic hematopoietic cell transplantation is underused as a curative therapy in eligible patients from the United States

Allogeneic hematopoietic cell transplantation (alloHCT) is a curative therapy for hematologic disorders including acute lymphoblastic and myeloid leukemia, chronic lymphocytic and myeloid leukemia, Hodgkin's and non-Hodgkin lymphoma, multiple myeloma, and myelodysplastic syndrome. To determine the utilization of alloHCT from unrelated donors (URDs) in the United States, we calculated the number of patients diagnosed with hematologic disorders age 20 to 74 years based on 2004 to 2008 Surveillance, Epidemiology and End Results and 2007 US Census data, estimated the percentage of patients who would be eligible for URD alloHCT after discounting the mortality rate during induction therapy and the rate of severe comorbidities, and compared these with the actual 2007 alloHCTs facilitated by the National Marrow Donor Program. We found that the number of URD alloHCT as a percentage of the estimated potential transplantations ranged from 11% for multiple myeloma to 54% for chronic myeloid leukemia, with an average percentage of 26% for all the disorders considered. In an analysis stratified by age groups (20 to 44, 45 to 64, and 65 to 74 years), the utilization of URD alloHCT was higher in younger patients than in older patients for all disorders. Of acute lymphoblastic and myeloid leukemia patients, approximately 66% underwent URD alloHCT later in the course of their disease (in second or greater complete remission). URD alloHCT is likely underused for potentially curable hematologic disorders, particularly in older patients. Understanding the reasons for low use of alloHCT may lead to strategies to expand the use of this curative therapy for more patients with hematologic disorders.

Demographics, treatment patterns, safety, and real-world effectiveness in patients aged 70 years and over with chronic lymphocytic leukemia receiving bendamustine with or without rituximab: a retrospective study

OBJECTIVES

Bendamustine is a unique cytotoxic agent active against various human malignancies, including chronic lymphocytic leukemia (CLL). In vitro studies suggest that cytotoxic activity of bendamustine on CLL-derived cells is synergized by rituximab. A retrospective chart review was conducted to characterize treatment-naïve outpatients and those with relapsed disease aged 70 years and over with CLL receiving bendamustine (with or without rituximab) and to evaluate real-world patterns of care, safety, and effectiveness.

METHODS

Using McKesson Specialty Care/US Oncology Network iKnowMed databases, 91 outpatients with at least two recorded visits and at least two cycles of bendamustine monotherapy or bendamustine-rituximab combination therapy were identified and included. Mean age at diagnosis and start of first therapy was 70.3 and 77.4 years respectively, and 63.7% of patients were men.

RESULTS

Observed overall response rate was 56.3% in pooled treatment-naïve patients [n = 9; complete response (CR) 18.8%; partial response (PR) 37.5%; nodular partial response (nPR) 0%] and 58.7% in pooled patients with relapsed disease (n = 44; CR 13.3%; PR 44.0%; nPR 1.3%). Median time to progressive disease has not been reached for the 16 treatment-naïve patients (median follow up 15.1 months), and was 18.4 months for those with relapsed disease (n = 73). No unexpected toxicities were observed. Overall rate of blood/bone marrow toxicities (all grades) was 40.7%; grade 3/4 rates were 18.8% in treatment-naïve patients and 25.3% in those with relapsed disease. Most frequent nonhematologic adverse events were fatigue and rash.

CONCLUSION

In this retrospective chart review of 91 outpatients with CLL aged 70 years and over, bendamustine (with or without rituximab) was an effective therapeutic option with manageable toxicity.

Efficacy of adoptive immunotherapy with donor lymphocyte infusion in relapsed lymphoid malignancies

Aims: There is a perceived benefit associated with the administration of donor lymphocyte infusion (DLI) in patients with lymphoid malignancies relapsing after allogeneic hematopoietic cell transplantation. However, it is unclear if and how this benefit varies according to specific diseases. Because administration of DLI is not universally effective and could be associated with significant toxicities resulting in morbidity and mortality, it is imperative to identify cases where benefits outweigh harms of the procedure. Materials & methods: We conducted a systematic review of the published literature and extracted and pooled data independently for each disease cohort: acute lymphoblastic leukemia (ALL), chronic lymphocytic leukemia (CLL), multiple myeloma (MM), non-Hodgkin’s lymphoma (NHL) and Hodgkin’s lymphoma (HL). Results: In summary, 39 studies met inclusion criteria. The pooled proportion (95% CI) for complete response was 27% (16–40) in ALL, 55% (15–92) in CLL, 26% (19–33) in MM, 52% (33–71) in NHL and 37% (20–56) in HL. Conclusion: Complete response rates appear higher when DLI is used for relapsed CLL and lymphomas (NHL and HL), and less pronounced in ALL or MM. Absence of data pertaining to disease-specific prognostic determinants, such as adverse genetic or molecular abnormalities, or quantitative disease burden when applicable, limit our ability to identify cases in whom benefits from DLI outweigh risks associated with the procedure within a particular disease.

Indications and outcomes of reduced-toxicity hematopoietic stem cell transplantation in adult patients with hematological malignancies

Hematopoietic stem cell transplantation (HCT) utilizing non-myeloablative (NMA) and reduced-intensity conditioning (RIC) regimens (collectively referred to as reduced-toxicity HCT, RT-HCT) has become a viable therapeutic option for patients with hematological malignancies who are ineligible for standard myeloablative conditioning transplantation (MA-HCT). RT-HCT has been shown to induce stable engraftment with low toxicity, and to produce similar overall and progression-free survival (PFS) when compared to MA-HCT in acute myeloid leukemia and myelodysplastic syndrome. The best results for RT-HCT have been reported for patients with disease that is in remission, indolent and chemosensitive, and with a strong graft-versus-malignancy effect. Chronic graft-versus-host disease seems to correlate with a lower relapse rate and better PFS. RT-HCT is inferior when performed in poor risk or advanced disease, due to high relapse rates. A search for novel strategies that includes the most appropriate conditioning regimens and post-transplant immunomodulation protocols with more intensive anti-malignancy activity but limited toxicity is in progress. This review provides an update on the results of clinical studies of RT-HCT, and discusses possible indications and investigative strategies for improving the clinical outcomes of RT-HCT for the major hematological malignancies.

Immunotherapies in CLL

Chronic lymphocytic leukemia (CLL) is the most frequently diagnosed leukemia in the Western world, yet remains essentially incurable. Although initial chemotherapy response rates are high, patients invariably relapse and subsequently develop resistance to chemotherapy. For the moment, allogeneic hematopoietic stem cell transplant (allo-HSCT) remains the only potentially curative treatment for patients with CLL, but it is associated with high rates of treatment-related mortality. Immune-based treatment strategies to augment the cytotoxic potential of T cells offer exciting new treatment options for patients with CLL, and provide a unique and powerful spectrum of tools distinct from traditional chemotherapy. Among the most novel and promising of these approaches are chimeric antigen receptor (CAR)-based cell therapies that combine advances in genetic engineering and adoptive immunotherapy.

Generation of functional CLL-specific cord blood CTL using CD40-ligated CLL APC

Though remissions have been observed following allo-HSCT for the treatment of CLL, many CLL patients are ineligible for transplant due to the lack of HLA-compatible donors. The use of umbilical cord blood (UCB) permits transplantation of many patients who lack HLA-compatible donors due to reduced requirements for stringent HLA matching between graft and recipient; however, disease relapse remains a concern with this modality. The generation of CLL-specific CTL from UCB T-cells, primed and expanded against the leukemic clone, might enhance the GVL effect and improve outcomes with UCB transplantation. Here we report the generation of functional, CLL-specific CTL using CD40-ligated CLL cells to prime partially-HLA matched UCB T-cells. Functionality and specificity were demonstrated by immune synapse assay, IFN-γ ELISpot, multi-parametric intracellular cytokine flow cytometry, and ⁵¹Cr release assay. The use of patient-specific, non-CLL controls demonstrated the generation of both alloantigen and CLL-specific responses. Subsequently, we developed a clinically-applicable procedure permitting separation of alloreactive CTL from leukemia-specific CTL. Leukemia-specific CTL were able to mediate in vivo killing of CLL in humanized mice without concurrent or subsequent development of xenoGVHD. Our results demonstrate that generation of CLL-specific effectors from UCB is feasible and practical, and the results support further exploration of this strategy as a treatment modality for CLL.

Autologous Stem Cell Transplantation for Chronic Lymphocytic Leukemia - Still a Valid Treatment Option, or is the Game Over?

Chemoimmunotherapy with fludarabine, cyclophosphamide, and rituximab (FCR) has been established as the current standard of care for young and fit patients with chronic lymphocytic leukemia (CLL). In the early nineties of the last century, long before the advent of fludarabine or antibody-based strategies, there was realistic hope that myeloablative therapy followed by autologous stem cell transplantation (autoSCT) might be an effective and potentially curative front-line treatment option for suitable patients with CLL. Since then, several prospective trials have disenthralled this hope: although autoSCT can prolong event and progression-free survival if used as part of early front-line treatment, it does not improve overall survival, while it is associated with an increased risk of late adverse events such as secondary malignancies. In addition, autoSCT lacks the potential to overcome the negative impact of biomarkers that confer resistance to chemotherapy or early relapse. The role of autoSCT has also been explored in the context of FCR, and it was demonstrated that its effect is inferior to the currently established optimal treatment regimen. In view of ongoing attempts to improve on FCR, promising clinical activity of new substances even in relapsed/ refractory CLL patients, exciting novel cell therapy approaches and advantages in the understanding of the disease and detection of Minimal Residual Disease (MRD), autoSCT has lost its place as a standard treatment option for CLL.

Reduced-intensity hematopoietic stem cell transplants for malignancies: harnessing the graft-versus-tumor effect

Allogeneic hematopoietic cell transplantation combines the power of cytotoxic chemo/radiotherapy with the ability of the new immune system to seek out and destroy tumor cells. However, administration of such myeloablative transplants is fraught with risks, some of which are related to the intensive conditioning regimens. Reductions in the intensity of the administered cytotoxic therapy have demonstrated that under some circumstances, the burden of fighting tumor and enhancing stem cell engraftment can be shouldered mostly by the transplanted immune system. Reduced intensity has allowed a potentially curative therapy for hematologic malignancies to be offered to an expanded patient population. Ongoing research seeks to enhance the safety and power of this form of allogeneic immunotherapy.