Failure to define window of time for autologous tumor vaccination in patients with newly diagnosed or relapsed acute lymphoblastic leukemia

Current challenges in the manufacture of clinical-grade autologous whole cell vaccines for hematological malignancies

Autologous whole cell vaccines use a patient's own tumor cells as a source of antigen to elicit an anti-tumor immune response in vivo. Recently, the authors conducted a systematic review of clinical trials employing these products in hematological cancers that showed a favorable safety profile and trend toward efficacy. However, it was noted that manufacturing challenges limit both the efficacy and clinical implementation of these vaccine products. In the current literature review, the authors sought to define the issues surrounding the manufacture of autologous whole cell products for hematological cancers. The authors describe key factors, including the acquisition, culture, cryopreservation and transduction of malignant cells, that require optimization for further advancement of the field. Furthermore, the authors provide a summary of pre-clinical work that informs how the identified challenges may be overcome. The authors also highlight areas in which future basic research would be of benefit to the field. The goal of this review is to provide a roadmap for investigators seeking to advance the field of autologous cell vaccines as it applies to hematological malignancies.

Safety and efficacy of autologous whole cell vaccines in hematologic malignancies: A systematic review and meta-analysis

Autologous cell vaccines use a patient's tumor cells to stimulate a broad antitumor response in vivo. This approach shows promise for treating hematologic cancers in early phase clinical trials, but overall safety and efficacy remain poorly described. We conducted a systematic review assessing the use of autologous cell vaccination in treating hematologic cancers. Primary outcomes of interest were safety and clinical response, with secondary outcomes including survival, relapse rate, correlative immune assays and health-quality related metrics. We performed a search of MEDLINE, Embase and the Cochrane Register of Controlled Trials including any interventional trial employing an autologous, whole cell product in any hematologic malignancy. Risk of bias was assessed using a modified Institute of Health Economics tool. Across 20 single arm studies, only 341 of 592 enrolled participants received one or more vaccinations. Primary reasons for not receiving vaccination included rapid disease progression/death and manufacturing challenges. Overall, few high-grade adverse events were observed. One death was reported and attributed to a GM-CSF producing allogeneic cell line co-administered with the autologous vaccine. Of 58 evaluable patients, the complete response rate was 21.0% [95% CI, 10.4%-37.8%)] and overall response rate was 35.8% (95% CI, 24.4%-49.0%). Of 97 evaluable patients for survival, the 5-years overall survival rate was 64.9% (95% CI, 52.6%-77.2%) and disease-free survival was 59.7% (95% CI, 47.7%-71.7%). We conclude that, in hematologic malignancies, based on limited available data, autologous cell vaccines are safe and display a trend towards efficacy but that challenges exist in vaccine manufacture and administration.

Dendritic Cell-Based and Other Vaccination Strategies for Pediatric Cancer

Dendritic cell-based and other vaccination strategies that use the patient’s own immune system for the treatment of cancer are gaining momentum. Most studies of therapeutic cancer vaccination have been performed in adults. However, since cancer is one of the leading causes of death among children past infancy in the Western world, the hope is that this form of active specific immunotherapy can play an important role in the pediatric population as well. Since children have more vigorous and adaptable immune systems than adults, therapeutic cancer vaccines are expected to have a better chance of creating protective immunity and preventing cancer recurrence in pediatric patients. Moreover, in contrast to conventional cancer treatments such as chemotherapy, therapeutic cancer vaccines are designed to specifically target tumor cells and not healthy cells or tissues. This reduces the likelihood of side effects, which is an important asset in this vulnerable patient population. In this review, we present an overview of the different therapeutic cancer vaccines that have been studied in the pediatric population, with a main focus on dendritic cell-based strategies. In addition, new approaches that are currently being investigated in clinical trials are discussed to provide guidance for further improvement and optimization of pediatric cancer vaccines.

Murine pre-B-cell ALL induces T-cell dysfunction not fully reversed by introduction of a chimeric antigen receptor

Adoptive transfer of patient-derived T cells modified to express chimeric antigen receptors (CARTs) has demonstrated dramatic success in relapsed/refractory pre-B-cell acute lymphoblastic leukemia (ALL), but response and durability of remission requires exponential CART expansion and persistence. Tumors are known to affect T-cell function, but this has not been well studied in ALL and in the context of chimeric antigen receptor (CAR) expression. Using TCF3/PBX1 and MLL-AF4-driven murine ALL models, we assessed the impact of progressive ALL on T-cell function in vivo. Vaccines protect against TCF3/PBX1.3 but were ineffective when administered after leukemia injection, suggesting immunosuppression induced early during ALL progression. T cells from leukemia-bearing mice exhibited increased expression of inhibitory receptors, including PD1, Tim3, and LAG3, and were dysfunctional following adoptive transfer in a model of T-cell receptor (TCR)-dependent leukemia clearance. Although expression of inhibitory receptors has been linked to TCR signaling, pre-B-cell ALL induced inhibitory receptor expression, at least in part, in a TCR-independent manner. Finally, introduction of a CAR into T cells generated from leukemia-bearing mice failed to fully reverse poor in vivo function.

Antibody Based Therapies in Acute Leukemia

Despite great progress in the curative treatment of acute leukemia, outcomes for those with relapsed and/or chemotherapy-refractory disease remain poor. Current intensive cytotoxic therapies can be associated with significant morbidity and novel therapies are needed to improve outcomes. Immunotherapy based approaches provide an alternative mechanism of action in the treatment of acute leukemia. Due to cell surface antigen expression, leukemia in particular is amenable to targeted therapies, such as antibody-based therapy. Based on the potential for non-overlapping toxicity, the possibility of synergistic action with standard chemotherapy, and by providing a novel method to overcome chemotherapy resistance, antibody-based therapies have shown potential for benefit. Modifications to standard monoclonal antibodies, including drug conjugation and linkage to T-cells, may further enhance efficacy of antibody-based therapies. Identifying the ideal timing for incorporation of antibody-based therapies, within standard regimens, may lead to improvement in overall outcomes. This article will provide an overview of antibody-based therapies in clinical development for the treatment of acute leukemia in children and adults, with a particular focus on the current strategies and future developments.

Cytotoxicity of CD56-positive lymphocytes against autologous B-cell precursor acute lymphoblastic leukemia cells

Precursor B-lineage acute lymphoblastic leukemia (pre-B ALL) affects hematopoietic development and therefore is associated with immune deficiencies that can be further exacerbated by chemotherapy. It is unclear if and when monoclonal antibodies (mAbs) that stimulate antibody-mediated cellular cytotoxicity (ADCC) can be used for treatment because this depends on the presence of functional effector cells. Here, we used flow cytometry to determine that patient samples at diagnosis, post-induction and relapse contain detectable numbers of CD56+ cells. We were able to selectively expand CD56+ immune effector cells from bone marrow and peripheral blood samples at diagnosis and at various stages of treatment by co-culture with artificial antigen-presenting K562 clone 9.mbIL-21 cells. Amplified CD56+CD3- cells had spontaneous and anti-BAFF-R mAb-stimulated ADCC activity against autologous ALL cells, which could be further enhanced by IL15. Importantly, matched CD56+ effector cells also killed autologous ALL cells grown out from leukemia samples of the same patient, through both spontaneous as well as antibody-dependent cellular cytotoxicity. Since autologous cell therapy will not be complicated by graft-versus-host disease, our results show that expanded CD56+ cells could be applied for treatment of pre-B-ALL without transplantation, or for purging of bone marrow in the setting of autologous bone marrow transplants.

Current progress in the development of a cell-based vaccine for the immunotherapy of acute myeloid leukemia

Evidence that immunological control contributes to the elimination of residual leukemia has emerged from allogeneic hematopoietic stem cell transplantation. This review assesses the current understanding of immunobiology of acute myeloid leukemia and how dendritic cells and T cells may be harnessed using in vitro and in vivo priming techniques. Preclinical and clinical dendritic cell vaccine trials reported to date are considered and the prospects for immunotherapy with dendritic cell-based vaccine constructs evaluated.

Impaired B-cell reconstitution in children after chemotherapy for standard or medium risk acute precursor B-lymphoblastic leukemia

Chemotherapy for childhood acute lymphoblastic leukemia (ALL) is a highly effective treatment, but at the same time causes significant suppression of the patient's immunity. Immune reconstitution was studied in a homogeneous cohort of 48 children with standard or medium risk ALL treated according to the ALL-Berlin-Frankfurt-Münster (BFM) protocol. Whereas the T-cell compartment was only moderately affected and recovered to normal levels quickly after treatment cessation, B-cells were significantly reduced during and after therapy. In particular, the naive B-cell compartment declined. Even 5 years after the end of therapy, B-cell distribution was disturbed and patients showed an ongoing reconstitution. Thus, even standard regimens for chemotherapy cause severe B-cell depletion that resolves only gradually.

Immunotherapy for pediatric leukemia

Substantial progress has been made in the treatment of leukemia in childhood. Despite this, leukemia remains a leading cause of pediatric cancer-related mortality and the prognosis is guarded for individuals with relapsed or refractory disease. Standard therapies are associated with a wide array of acute and long-term toxicities and further treatment intensification may not be tolerable or beneficial. The curative potential of allogeneic stem cell transplantation is due in part to the graft-versus-leukemia effect, which provides evidence for the therapeutic capacity of immune-based therapies. In recent years there have been significant advances in the development and application of immunotherapy in the treatment of leukemias, including the demonstration of activity in chemotherapy-resistant cases. This review summarizes immunotherapeutic approaches in the treatment of pediatric leukemia including current results and future directions.

NCI First International Workshop on the Biology, Prevention, and Treatment of Relapse after Allogeneic Hematopoietic Stem Cell Transplantation: Report from the Committee on Treatment of Relapse after Allogeneic Hematopoietic Stem Cell Transplantation

Relapse is a major cause of treatment failure after allogeneic hematopoietic stem cell transplantation (alloHSCT). Treatment options for relapse have been inadequate, and the majority of patients ultimately die of their disease. There is no standard approach to treating relapse after alloHSCT. Withdrawal of immune suppression and donor lymphocyte infusions are commonly used for all diseases; although these interventions are remarkably effective for relapsed chronic myelogenous leukemia, they have limited efficacy in other hematologic malignancies. Conventional and novel chemotherapy, monoclonal antibody therapy, targeted therapies, and second transplants have been utilized in a variety of relapsed diseases, but reports on these therapies are generally anecdotal and retrospective. As such, there is an immediate need for well-designed, disease-specific trials for treatment of relapse after alloHSCT. This report summarizes current treatment options under investigation for relapse after alloHSCT in a disease-specific manner. In addition, recommendations are provided for specific areas of research necessary in the treatment of relapse after alloHSCT.

Application of immunotherapy in pediatric leukemia

Despite great progress in the curative treatment of leukemia in pediatrics, current therapies are associated with multiple toxicities and the prognosis after relapse is guarded. Novel approaches are needed to overcome resistance to standard therapy and decrease adverse effects. The efficacy of allogeneic stem cell transplantation and the demonstration of a graft-versus-leukemia effect suggest that immune-based therapies can be effective in the treatment of childhood leukemia. Efforts to apply new immunotherapy approaches to the treatment of leukemia in pediatrics have recently begun. The optimal reagents, methods, and regimens have yet to be fully defined. Ongoing clinical trials offer promise in that regard.

Anti-CD22 immunotoxin RFB4(dsFv)-PE38 (BL22) for CD22-positive hematologic malignancies of childhood: preclinical studies and phase I clinical trial

PURPOSE

Although most children with B-lineage acute lymphoblastic leukemia (ALL) and non-Hodgkin lymphoma are cured, new agents are needed to overcome drug resistance and reduce toxicities of chemotherapy. We hypothesized that the novel anti-CD22 immunotoxin, RFB4(dsFv)-PE38 (BL22, CAT-3888), would be active and have limited nonspecific side effects in children with CD22-expressing hematologic malignancies. We conducted the first preclinical and phase I clinical studies of BL22 in that setting.

EXPERIMENTAL DESIGN

Lymphoblasts from children with B-lineage ALL were assessed for CD22 expression by flow cytometry and for BL22 sensitivity by in vitro cytotoxicity assay. BL22 was evaluated in a human ALL murine xenograft model. A phase I clinical trial was conducted for pediatric subjects with CD22+ ALL and non-Hodgkin lymphoma.

RESULTS

All samples screened were CD22+. BL22 was cytotoxic to blasts in vitro (median IC(50), 9.8 ng/mL) and prolonged the leukemia-free survival of murine xenografts. Phase I trial cohorts were treated at escalating doses and schedules ranging from 10 to 40 microg/kg every other day for three or six doses repeated every 21 or 28 days. Treatment was associated with an acceptable safety profile, adverse events were rapidly reversible, and no maximum tolerated dose was defined. Pharmacokinetics were influenced by disease burden consistent with rapid drug binding by CD22+ blasts. Although no responses were observed, transient clinical activity was seen in most subjects.

CONCLUSIONS

CD22 represents an excellent target and anti-CD22 immunotoxins offer therapeutic promise in B-lineage hematologic malignancies of childhood.

Immunotherapy of childhood cancer: from biologic understanding to clinical application

PURPOSE OF REVIEW

Most children with cancer can be cured with combination regimens of chemotherapy, radiation, surgery, or all. However, standard therapies are toxic to normal tissues, cancer cells commonly develop resistance to chemotherapy, and relapsed malignancy is a leading cause of mortality in pediatrics. Elucidation of the principles of the normal immune response and tumor biology, coupled with technological developments, have led to important advances in the field of cancer immunotherapy. This review summarizes the biologic basis of cancer immunotherapy and highlights recent examples of progress in the application of novel humoral and cellular immunotherapies to children and adolescents with malignancy.

RECENT FINDINGS

Clinical trials of immunotherapy for pediatric cancer have recently been initiated. To date, most immune-based therapies have been well tolerated and some have shown clinically significant activity against specific refractory high-risk malignancies.

SUMMARY

Recent clinical trial results provide proof-of-principle that cancer immunotherapy has the capacity to overcome chemotherapy resistance without the usual toxicities associated with cytotoxic regimens. Immunotherapy holds promise in the treatment of children and adolescents with cancer and has the potential to improve both survival and quality of life.

Long-term protection from syngeneic acute lymphoblastic leukemia by CpG ODN-mediated stimulation of innate and adaptive immune responses

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer and remains a major cause of mortality in children with recurrent disease and in adults. Despite observed graft-versus-leukemia effects after stem cell transplantation, successful immune therapies for ALL have proven elusive. We previously reported immunostimulatory oligodeoxynucleotides containing CpG motifs (CpG ODN) enhance allogeneic T(h)1 responses and reduce leukemic burden of primary human ALL xenografts. To further the development of CpG ODN as a novel ALL therapy, we investigated the antileukemia activity induced by CpG ODN in a transplantable syngeneic pre-B ALL model. CpG ODN induced early killing of leukemia by innate immune effectors both in vitro and in vivo. Mice were treated with CpG ODN starting 7 days after injection with leukemia to mimic a minimal residual disease state and achieved T cell-dependent remissions of more than 6 months. In addition, mice in remission after CpG ODN treatment were protected from leukemia rechallenge, and adoptive transfer of T cells from mice in remission conferred protection against leukemia growth. To our knowledge, this is the first demonstration that CpG ODN induce a durable remission and ongoing immune-mediated protection in ALL, suggesting this treatment may have clinical utility in patients with minimal residual disease.

Generation of functional dendritic cells (DC) in adult acute lymphoblastic leukemia: rationale for a DC-based vaccination program for patients in complete hematological remission

The capacity to generate effective dendritic cells (DC) from adult acute lymphoblastic leukemia (ALL) patients in complete remission (CR) and off-therapy was investigated. Monocyte-derived DC cultured in the presence of granulocyte-macrophage colony-stimulating factor, interleukin (IL)-4 and tumor necrosis factor (TNF)-alpha expressed maturation markers, produced IL-12 and loaded apoptotic bodies to a similar extent to normal DC. Patients' circulating T and NK lymphocytes were normally represented and, after stimulation, were capable of producing TNF-alpha and interferon-gamma to a similar extent to control lymphocytes. DC loaded with leukemia-derived apoptotic bodies increased their ability to stimulate both allogeneic and autologous lymphocytes, and to generate specific anti-leukemic CD3 + cells. These findings offer a rationale for the design of DC-based vaccine programs for adult ALL patients in CR with the aim of controlling/eradicating the disease.

Acute lymphoblastic leukaemia cells express CCR7 but not higher amounts of IL-10 after CD40 ligation

OBJECTIVE

Production of cytokines that support T-cell activation and proliferation and migration to lymph nodes is one of the most important terms of cancer vaccine development. In previous studies we and others used CD40 ligation to obtain higher expression of co-stimulatory and adhesion molecules on leukaemic cells from children with acute lymphoblastic leukaemia (ALL). This time we assess the cytokine and chemokine gene expression profile in CD40-stimulated ALL cells.

MATERIAL AND METHODS

Malignant cells from 25 children with BCP-ALL were stimulated (or not) with huCD40LT and rIL-4 for 96 h. Eleven different molecule, cytokine and chemokine mRNAs levels (CCR7, IL-23, TGF-beta-IP, IFN-gamma, IL-10, CD1a, CD40, CD54, CD80, CD83, CD86) were determined using the real-time PCR technique with TaqMan chemistry using ready-to-use low-density arrays for gene expression by Applied Biosystems.

RESULTS

1) Increases in mRNA levels for CD40, CD54 and CD80 after CD40L and IL-4 stimulation were observed, 2) CCR7 mRNA expression was higher after CD40 ligation than before the culture (p = 0.002), 3) IL-10 mRNA expression was higher after the culture with medium than before the culture (p = 0.01).

CONCLUSIONS

The results show that leukaemia-derived dendritic cells obtained with CD40 ligation express CCR7 - chemokine is involved in migration to lymph nodes and does not produce higher amounts of IL-10, a potent immunosuppressive cytokine. Our preclinical findings could be used in the design of immunotherapy trials for the treatment of children with ALL.

T cells stimulated by CD40L positive leukemic blasts-pulsed dendritic cells meet optimal functional requirements for adoptive T-cell therapy

Adoptive T-cell immunotherapy may provide complementary therapy for childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL). In this study, we have analyzed the functional characteristics of anti-BCP-ALL effector T cells generated by co-culturing T lymphocytes and dendritic cells (DC) from allogeneic human stem cell transplantation (HSCT) donors. After 21-day co-culture with DC pulsed with CD40L+ apoptotic BCP-ALL blasts, T cells presented with both effector and central memory phenotype, and showed high and specific cytotoxic activity against leukemic cells (average lysis = 77%), mostly mediated by CD8+ T cells. Noticeably, growth of CD4 T cells was maintained (45% of total cells), which actively produced Th1 cytokines (IFN-gamma, TNF-alpha, IL-2), but not IL-4, IL-5 and IL-10. Anti-BCP-ALL T cells expressed CD49d and CXCR4 (implicated in the recruitment to bone marrow), and CD62L and CCR7 (involved in the migration to lymphoid organs). In accordance with this profile, T cells significantly migrated in response to the chemokines CXCL12 and CCL19. In conclusion, stimulation of T cells with CD40L+BCP-ALL cells-loaded DC not only elicited the generation of potent and specific anti-leukemic cytotoxic effectors, but also the differentiation of specific and functional Th-1 CD4 lymphocytes. These effectors are fully equipped to reach leukemia-infiltrated tissues and have characteristics to support and orchestrate the anti-tumor immune-response.

Gene expression profiling identifies BAX-delta as a novel tumor antigen in acute lymphoblastic leukemia

The identification of new tumor-associated antigens (TAA) is critical for the development of effective immunotherapeutic strategies, particularly in diseases like B-cell acute lymphoblastic leukemia (B-ALL), where few target epitopes are known. To accelerate the identification of novel TAA in B-ALL, we used a combination of expression profiling and reverse immunology. We compared gene expression profiles of primary B-ALL cells with their normal counterparts, B-cell precursors. Genes differentially expressed by B-ALL cells included many previously identified as TAA in other malignancies. Within this set of overexpressed genes, we focused on those that may be functionally important to the cancer cell. The apoptosis-related molecule, BAX, was highly correlated with the ALL class distinction. Therefore, we evaluated BAX and its isoforms as potential TAA. Peptides from the isoform BAX-delta bound with high affinity to HLA-A*0201 and HLA-DR1. CD8+ CTLs specific for BAX-delta epitopes or their heteroclitic peptides could be expanded from normal donors. BAX-delta-specific T cells lysed peptide-pulsed targets and BAX-delta-expressing leukemia cells in a MHC-restricted fashion. Moreover, primary B-ALL cells were recognized by BAX-delta-specific CTL, indicating that this antigen is naturally processed and presented by tumor cells. This study suggests that (a) BAX-delta may serve as a widely expressed TAA in B-ALL and (b) gene expression profiling can be a generalizable tool to identify immunologic targets for cancer immunotherapy.

Immunotherapy of high-risk acute leukemia with a recipient (autologous) vaccine expressing transgenic human CD40L and IL-2 after chemotherapy and allogeneic stem cell transplantation

CD40L generates immune responses in leukemia-bearing mice, an effect that is potentiated by IL-2. We studied the feasibility, safety, and immunologic efficacy of an IL-2- and CD40L-expressing recipient-derived tumor vaccine consisting of leukemic blasts admixed with skin fibroblasts transduced with adenoviral vectors encoding human IL-2 (hIL-2) and hCD40L. Ten patients (including 7 children) with high-risk acute myeloid (n = 4) or lymphoblastic (n = 6) leukemia in cytologic remission (after allogeneic stem cell transplantation [n = 9] or chemotherapy alone [n = 1]) received up to 6 subcutaneous injections of the IL-2/CD40L vaccine. None of the patients were receiving immunosuppressive drugs. No severe adverse reactions were noted. Immunization produced a 10- to 890-fold increase in the frequencies of major histocompatibility complex (MHC)-restricted T cells reactive against recipient-derived blasts. These leukemia-reactive T cells included both T-cytotoxic/T-helper 1 (Th1) and Th2 subclasses, as determined from their production of granzyme B, interferon-gamma, and interleukin-5. Two patients produced systemic IgG antibodies that bound to their blasts. Eight patients remained disease free for 27 to 62 months after treatment (5-year overall survival, 90%). Thus, even in heavily treated patients, including recipients of allogeneic stem cell transplants, recipient-derived antileukemia vaccines can induce immune responses reactive against leukemic blasts. This approach may be worthy of further study, particularly in patients with a high risk of relapse.

Antigen-specific T-cell memory is preserved in children treated for acute lymphoblastic leukemia

Despite profound T-cell immunodeficiency, most patients treated with chemotherapy do not succumb to infection. The basis for residual protective immunity in lymphopenic patients is not known. We prospectively measured T-cell numbers, thymopoiesis, and T-cell memory in 73 children undergoing a 2-year chemotherapy regimen for acute lymphoblastic leukemia (ALL) and compared them to an age-matched cohort of 805 healthy children. Most patients had profound defects in CD4 and CD8 T-cell numbers at diagnosis that did not recover during the 2 years of therapy. Thymic output and the fraction of naive T cells were significantly lower than in healthy controls. However, the remaining T-cell compartment was enriched for antigen-experienced, memory T cells defined both by phenotype and by function. This relative sparing of T-cell memory may, in part, account for the maintenance of protective immunity in lymphopenic patients treated for ALL. Moreover, because the memory T-cell compartment is least affected by ALL and its treatment, strategies to induce immunity to pathogens or tumor antigens in cancer patients may be most successful if they seek to expand pre-existing memory T cells.