Curing glioblastoma: oncolytic HSV-IL12 and checkpoint blockade.
Okt. 2017 | Saha, Dipongkor; Martuza, Robert L; Rabkin, Samuel D
Curing glioblastoma: oncolytic HSV-IL12 and checkpoint blockade.
Prospect of Immunotherapy for Glioblastoma: Tumor Vaccine, Immune Checkpoint Inhibitors and Combination Therapy.
Mai 2017 | Ishikawa, Eiichi; Yamamoto, Tetsuya; Matsumura, Akira
To date, clinical trials of various vaccine therapies using autologous tumor antigens or tumor-associated/specific antigen peptide with adjuvants have been performed to treat patients with high-grade gliomas (HGG). Furthermore, immune checkpoint pathway-targeted therapies including anti- programmed cell death 1 (PD-1) antibody have been remarkably effective in other neoplasms, and various clinical trials with anti-PD-1 antibody in patients with HGG have started to date. It is possible that up-regulation of immune checkpoint molecules in tumor tissues after vaccine therapy may be one of the mechanisms of vaccine failure. Multiple preclinical studies indicate that combination therapy with vaccination and immune checkpoint blockade is effective for the treatment of malignant tumors including HGG. Thus, immunotherapy, especially combination therapy with vaccine and immune checkpoint inhibitors, may be a promising strategy for treatment of patients with HGG. PMID 28539528
Targeting the PD-1 pathway in pediatric solid tumors and brain tumors.
Apr. 2017 | Wagner, Lars M; Adams, Val R
While remarkable advances have been made in the treatment of pediatric leukemia over the past decades, new therapies are needed for children with advanced solid tumors and high-grade brain tumors who fail standard chemotherapy regimens. Immunotherapy with immune checkpoint inhibitors acting through the programmed cell death-1 (PD-1) pathway has shown efficacy in some chemotherapy-resistant adult cancers, generating interest that these agents may also be helpful to treat certain refractory pediatric malignancies. In this manuscript we review current strategies for targeting the PD-1 pathway, highlighting putative biomarkers and the rationale for investigation of these drugs to treat common pediatric tumors such as sarcoma, neuroblastoma, and high-grade glioma. We summarize the completed and ongoing clinical trial data available, and suggest potential applications for further study. PMID 28442918
Assessing Response of High-Grade Gliomas to Immune Checkpoint Inhibitors.
Apr. 2017 | Sahebjam, Solmaz; Stallworth, Dexter G; Mokhtari, Sepideh; Tran, Nam D; Arrington, John A
Immunotherapeutic agents, especially checkpoint inhibitors, have emerged as the mainstay of therapy for several solid and hematological malignancies. These therapies are under investigation for the treatment of high-grade gliomas and brain metastases. PMID 28441372
Targeting the immune niche within the bone marrow microenvironment: The rise of immunotherapy in Multiple Myeloma.
Feb. 2017 | Podar, Klaus; Jäger, D
Multiple Myeloma (MM) cells inhibit the development of an effective anti-MM immune response via defects in T cell function, ineffective antigen presentation; reduced phagocytic capacity; natural killer and dendritic cell dysfunction; decreased responsiveness to IL-2 and defects in B cell immunity; upregulation of inhibitory pathways; and production of excessive pro-inflammatory cytokines. Moreover, immune cells including plasmacytoid dendritic cells and macrophages trigger tumor cell proliferation, survival, and drug resistance. The usefulness of immunotherapies in MM patients has first been supported by the identification of the graft-versus-myeloma effect in the context of allogeneic bone marrow (BM) transplantation. Subsequently, the inclusion of thalidomide and its derivatives, the Immunomodulatory Drugs (IMiDs) as well as of (immuno) proteasome inhibitors into MM regimens dramatically improved MM patients' outcome during the last 15 years. Despite these unprecedented therapeutic advances MM remains an incurable disease. Novel immunotherapeutic approaches aim to restore the balance within the immunologic niche of the MM BM microenvironment. Indeed, the inclusion of monoclonal antibodies, immune checkpoint inhibitors, chimeric antigen receptor-engineered (CAR) T cells, genetically engineered T cells, and vaccination, dendritic cell- based cancer vaccines in particular, into existing regimens is likely to significantly improve MM patient outcome in the near future. PMID 28201977
Immunosuppressive tumor-infiltrating myeloid cells mediate adaptive immune resistance via a PD-1/PD-L1 mechanism in glioblastoma.
Jan. 2017 | Antonios, Joseph P; Soto, Horacio; Everson, Richard G; Moughon, Diana; Orpilla, Joey R; Shin, Namjo P; Sedighim, Shaina; Treger, Janet; Odesa, Sylvia; Tucker, Alexander; Yong, William H; Li, Gang; Cloughesy, Timothy F; Liau, Linda M; Prins, Robert M
Adaptive immune resistance in the tumor microenvironment appears to attenuate the immunotherapeutic targeting of glioblastoma (GBM). In this study, we identified a tumor-infiltrating myeloid cell (TIM) population that expands in response to dendritic cell (DC) vaccine treatment. The aim of this study was to understand how this programmed death ligand 1 (PD-L1)-expressing population restricts activation and tumor-cytolytic function of vaccine-induced tumor-infiltrating lymphocytes (TILs). PMID 28115578
Prostate cancer immunotherapy, particularly in combination with androgen deprivation or radiation treatment. Customized pharmacogenomic approaches to overcome immunotherapy cancer resistance.
Jan. 2017 | Alberti, C
Conventional therapeutic approaches for advanced prostate cancer - such as androgen deprivation, chemotherapy, radiation - come up often against lack of effectiveness because of possible arising of correlative cancer cell resistance and/or inadequate anti-tumor immune conditions. Whence the timeliness of resorting to immune-based treatment strategies including either therapeutic vaccination-based active immunotherapy or anti-tumor monoclonal antibody-mediated passive immunotherapy. Particularly attractive, as for research studies and clinical applications, results to be the cytotoxic T-lymphocyte check point blockade by the use of anti-CTLA-4 and PD-1 monoclonal antibodies, particularly when combined with androgen deprivation therapy or radiation. Unlike afore said immune check point inhibitors, both cell-based (by the use of prostate specific antigen carriers autologous dendritic cells or even whole cancer cells) and recombinant viral vector vaccines are able to induce immune-mediated focused killing of specific antigen-presenting prostate cancer cells. Such vaccines, either used alone or concurrently/sequentially combined with above-mentioned conventional therapies, led to generally reach, in the field of various clinical trials, reasonable results particularly as regards the patient's overall survival. Adoptive trasferred T-cells, as adoptive T-cell passive immunotherapy, and monoclonal antibodies against specific antigen-endowed prostate cancer cells can improve immune micro-environmental conditions. On the basis of a preliminary survey about various immunotherapy strategies, are here also outlined their effects when combined with androgen deprivation therapy or radiation. What's more, as regard the immune-based treatment effectiveness, it has to be pointed out that suitable personalized epigenetic/gene profile-achieved pharmacogenomic approaches to target identified gene aberrations, may lead to overcome - as well as for conventional therapies - possible prostate cancer resistance to immunotherapy. PMID 28098061
PD-1 blockade enhances the vaccination-induced immune response in glioma.
Juli 2016 | Antonios, Joseph P; Soto, Horacio; Everson, Richard G; Orpilla, Joey; Moughon, Diana; Shin, Namjo; Sedighim, Shaina; Yong, William H; Li, Gang; Cloughesy, Timothy F; Liau, Linda M; Prins, Robert M
DC vaccination with autologous tumor lysate has demonstrated promising results for the treatment of glioblastoma (GBM) in preclinical and clinical studies. While the vaccine appears capable of inducing T cell infiltration into tumors, the effectiveness of active vaccination in progressively growing tumors is less profound. In parallel, a number of studies have identified negative costimulatory pathways, such as programmed death 1/programmed death ligand 1 (PD-1/PD-L1), as relevant mediators of the intratumoral immune responses. Clinical responses to PD-1 pathway inhibition, however, have also been varied. To evaluate the relevance to established glioma, the effects of PD-1 blockade following DC vaccination were tested in intracranial (i.c.) glioma tumor- bearing mice. Treatment with both DC vaccination and PD-1 mAb blockade resulted in long-term survival, while neither agent alone induced a survival benefit in animals with larger, established tumors. This survival benefit was completely dependent on CD8(+) T cells. Additionally, DC vaccine plus PD-1 mAb blockade resulted in the upregulation of integrin homing and immunologic memory markers on tumor-infiltrating lymphocytes (TILs). In clinical samples, DC vaccination in GBM patients was associated with upregulation of PD-1 expression in vivo, while ex vivo blockade of PD-1 on freshly isolated TILs dramatically enhanced autologous tumor cell cytolysis. These findings strongly suggest that the PD-1/PD-L1 pathway plays an important role in the adaptive immune resistance of established GBM in response to antitumor active vaccination and provide us with a rationale for the clinical translation of this combination therapy. PMID 27453950
Overcoming Barriers in Oncolytic Virotherapy with HDAC Inhibitors and Immune Checkpoint Blockade.
Jan. 2016 | Marchini, Antonio; Scott, Eleanor M; Rommelaere, Jean
Oncolytic viruses (OVs) target and destroy cancer cells while sparing their normal counterparts. These viruses have been evaluated in numerous studies at both pre-clinical and clinical levels and the recent Food and Drug Administration (FDA) approval of an oncolytic herpesvirus-based treatment raises optimism that OVs will become a therapeutic option for cancer patients. However, to improve clinical outcome, there is a need to increase OV efficacy. In addition to killing cancer cells directly through lysis, OVs can stimulate the induction of anti-tumour immune responses. The host immune system thus represents a "double-edged sword" for oncolytic virotherapy: on the one hand, a robust anti-viral response will limit OV replication and spread; on the other hand, the immune-mediated component of OV therapy may be its most important anti-cancer mechanism. Although the relative contribution of direct viral oncolysis and indirect, immune-mediated oncosuppression to overall OV efficacy is unclear, it is likely that an initial period of vigorous OV multiplication and lytic activity will most optimally set the stage for subsequent adaptive anti-tumour immunity. In this review, we consider the use of histone deacetylase (HDAC) inhibitors as a means of boosting virus replication and lessening the negative impact of innate immunity on the direct oncolytic effect. We also discuss an alternative approach, aimed at potentiating OV-elicited anti-tumour immunity through the blockade of immune checkpoints. We conclude by proposing a two-phase combinatorial strategy in which initial OV replication and spread is maximised through transient HDAC inhibition, with anti-tumour immune responses subsequently enhanced by immune checkpoint blockade. PMID 26751469
Fueling the engine and releasing the break: combinational therapy of cancer vaccines and immune checkpoint inhibitors.
Okt. 2015 | Kleponis, Jennifer; Skelton, Richard; Zheng, Lei
Immune checkpoint inhibitors are increasingly drawing much attention in the therapeutic development for cancer treatment. However, many cancer patients do not respond to treatments with immune checkpoint inhibitors, partly because of the lack of tumor-infiltrating effector T cells. Cancer vaccines may prime patients for treatments with immune checkpoint inhibitors by inducing effector T-cell infiltration into the tumors and immune checkpoint signals. The combination of cancer vaccine and an immune checkpoint inhibitor may function synergistically to induce more effective antitumor immune responses, and clinical trials to test the combination are currently ongoing. PMID 26487965
Rationale for a Multimodality Strategy to Enhance the Efficacy of Dendritic Cell-Based Cancer Immunotherapy.
Juni 2015 | Datta, Jashodeep; Berk, Erik; Cintolo, Jessica A; Xu, Shuwen; Roses, Robert E; Czerniecki, Brian J
Dendritic cells (DC), master antigen-presenting cells that orchestrate interactions between the adaptive and innate immune arms, are increasingly utilized in cancer immunotherapy. Despite remarkable progress in our understanding of DC immunobiology, as well as several encouraging clinical applications - such as DC-based sipuleucel-T for metastatic castration-resistant prostate cancer - clinically effective DC-based immunotherapy as monotherapy for a majority of tumors remains a distant goal. The complex interplay between diverse molecular and immune processes that govern resistance to DC-based vaccination compels a multimodality approach, encompassing a growing arsenal of antitumor agents which target these distinct processes and synergistically enhance DC function. These include antibody-based targeted molecular therapies, immune checkpoint inhibitors, therapies that inhibit immunosuppressive cellular elements, conventional cytotoxic modalities, and immune potentiating adjuvants. It is likely that in the emerging era of "precision" cancer therapeutics, tangible clinical benefits will only be realized with a multifaceted - and personalized - approach combining DC-based vaccination with adjunctive strategies. PMID 26082780
Immune checkpoint targeting in cancer therapy: toward combination strategies with curative potential.
Apr. 2015 | Sharma, Padmanee; Allison, James P
Research in two fronts has enabled the development of therapies that provide significant benefit to cancer patients. One area stems from a detailed knowledge of mutations that activate or inactivate signaling pathways that drive cancer development. This work triggered the development of targeted therapies that lead to clinical responses in the majority of patients bearing the targeted mutation, although responses are often of limited duration. In the second front are the advances in molecular immunology that unveiled the complexity of the mechanisms regulating cellular immune responses. These developments led to the successful targeting of immune checkpoints to unleash anti-tumor T cell responses, resulting in durable long-lasting responses but only in a fraction of patients. In this Review, we discuss the evolution of research in these two areas and propose that intercrossing them and increasing funding to guide research of combination of agents represent a path forward for the development of curative therapies for the majority of cancer patients. PMID 25860605
Clinical use of dendritic cells for cancer therapy.
Mai 2014 | Anguille, Sébastien; Smits, Evelien L; Lion, Eva; van Tendeloo, Viggo F; Berneman, Zwi N
Since the mid-1990s, dendritic cells have been used in clinical trials as cellular mediators for therapeutic vaccination of patients with cancer. Dendritic cell-based immunotherapy is safe and can induce antitumour immunity, even in patients with advanced disease. However, clinical responses have been disappointing, with classic objective tumour response rates rarely exceeding 15%. Paradoxically, findings from emerging research indicate that dendritic cell-based vaccination might improve survival, advocating implementation of alternative endpoints to assess the true clinical potency of dendritic cell-based vaccination. We review the clinical effectiveness of dendritic cell-based vaccine therapy in melanoma, prostate cancer, malignant glioma, and renal cell carcinoma, and summarise the most important lessons from almost two decades of clinical studies of dendritic cell-based immunotherapy in these malignant disorders. We also address how the specialty is evolving, and which new therapeutic concepts are being translated into clinical trials to leverage the clinical effectiveness of dendritic cell-based cancer immunotherapy. Specifically, we discuss two main trends: the implementation of the next-generation dendritic cell vaccines that have improved immunogenicity, and the emerging paradigm of combination of dendritic cell vaccination with other cancer therapies. PMID 24872109
Localized oncolytic virotherapy overcomes systemic tumor resistance to immune checkpoint blockade immunotherapy.
März 2014 | Zamarin, Dmitriy; Holmgaard, Rikke B; Subudhi, Sumit K; Park, Joon Seok; Mansour, Mena; Palese, Peter; Merghoub, Taha; Wolchok, Jedd D; Allison, James P
Preexisting lymphocytic infiltration of tumors is associated with superior prognostic outcomes in a variety of cancers. Recent studies also suggest that lymphocytic responses may identify patients more likely to benefit from therapies targeting immune checkpoints, suggesting that therapeutic efficacy of immune checkpoint blockade can be enhanced through strategies that induce tumor inflammation. To achieve this effect, we explored the immunotherapeutic potential of oncolytic Newcastle disease virus (NDV). We find that localized intratumoral therapy of B16 melanoma with NDV induces inflammatory responses, leading to lymphocytic infiltrates and antitumor effect in distant (nonvirally injected) tumors without distant virus spread. The inflammatory effect coincided with distant tumor infiltration with tumor-specific CD4(+) and CD8(+) T cells, which was dependent on the identity of the virus-injected tumor. Combination therapy with localized NDV and systemic CTLA-4 blockade led to rejection of preestablished distant tumors and protection from tumor rechallenge in poorly immunogenic tumor models, irrespective of tumor cell line sensitivity to NDV-mediated lysis. Therapeutic effect was associated with marked distant tumor infiltration with activated CD8(+) and CD4(+) effector but not regulatory T cells, and was dependent on CD8(+) cells, natural killer cells, and type I interferon. Our findings demonstrate that localized therapy with oncolytic NDV induces inflammatory immune infiltrates in distant tumors, making them susceptible to systemic therapy with immunomodulatory antibodies, which provides a strong rationale for investigation of such combination therapies in the clinic. PMID 24598590
Clinical Implications of Co-Inhibitory Molecule Expression in the Tumor Microenvironment for DC Vaccination: A Game of Stop and Go.
Dez. 2013 | Vasaturo, Angela; Di Blasio, Stefania; Peeters, Deborah G A; de Koning, Coco C H; de Vries, Jolanda M; Figdor, Carl G; Hato, Stanleyson V
The aim of therapeutic dendritic cell (DC) vaccines in cancer immunotherapy is to activate cytotoxic T cells to recognize and attack the tumor. T cell activation requires the interaction of the T cell receptor with a cognate major-histocompatibility complex-peptide complex. Although initiated by antigen engagement, it is the complex balance between co-stimulatory and co-inhibitory signals on DCs that results in T cell activation or tolerance. Even when already activated, tumor-specific T cells can be neutralized by the expression of co-inhibitory molecules on tumor cells. These and other immunosuppressive cues in the tumor microenvironment are major factors currently hampering the application of DC vaccination. In this review, we discuss recent data regarding the essential and complex role of co-inhibitory molecules in regulating the immune response within the tumor microenvironment. In particular, possible therapeutic intervention strategies aimed at reversing or neutralizing suppressive networks within the tumor microenvironment will be emphasized. Importantly, blocking co-inhibitory molecule signaling, often referred to as immune checkpoint blockade, does not necessarily lead to an effective activation of tumor-specific T cells. Therefore, combination of checkpoint blockade with other immune potentiating therapeutic strategies, such as DC vaccination, might serve as a synergistic combination, capable of reversing effector T cells immunosuppression while at the same time increasing the efficacy of T cell-mediated immunotherapies. This will ultimately result in long-term anti-tumor immunity. PMID 24348481
Blockade of PD-1/PD-L1 immune checkpoint during DC vaccination induces potent protective immunity against breast cancer in hu-SCID mice.
Juli 2013 | Ge, Yan; Xi, Hong; Ju, Songguang; Zhang, Xueguang
Immune checkpoints, such as the PD-1/PD-L1 pathway, negatively interfere in the efficiency of dendritic cell (DC) vaccination in cancer immunotherapy. In this study, we demonstrated that the blockade of PD-L1 signaling could promote DC maturation, proliferation, and IL-12 secretion, augment DC primed T cell response and reverse tumor cell dampened T cell impairment. Blockade of PD-L1 signaling during DC vaccination showed better therapeutic effects than classic DC vaccination by preventing tumor growth and prolonging survival times in a breast tumor-bearing hu-SCID model. Taken together, suppressing immune checkpoints during DC vaccination might be a more efficient strategy for cancer therapy. PMID 23523609
PD-1 blockade by CT-011, anti-PD-1 antibody, enhances ex vivo T-cell responses to autologous dendritic cell/myeloma fusion vaccine.
Mai 2011 | Rosenblatt, Jacalyn; Glotzbecker, Brett; Mills, Heidi; Vasir, Baldev; Tzachanis, Dimitrios; Levine, James D; Joyce, Robin M; Wellenstein, Kerry; Keefe, Whitney; Schickler, Michael; Rotem-Yehudar, Rinat; Kufe, Donald; Avigan, David
We have developed a cancer vaccine in which autologous tumor is fused with dendritic cells (DCs) resulting in the presentation of tumor antigens in the context of DC-mediated costimulation. In clinical trials, immunologic responses have been observed, however responses may be muted by inhibitory pathways. The PD1/PDL1 pathway is an important element contributing to tumor-mediated immune suppression. In this study, we demonstrate that myeloma cells and DC/tumor fusions strongly express PD-L1. Compared with a control population of normal volunteers, increased PD-1 expression was observed on T cells isolated from patients with myeloma. It is interesting to note that after autologous transplantation, T-cell expression of PD-1 returned to levels seen in normal controls. We examined the effect of PD-1 blockade on T-cell response to DC/tumor fusions ex vivo. Presence of CT-011, an anti-PD1 antibody, promoted the vaccine-induced T-cell polarization towards an activated phenotype expressing Th1 compared with Th2 cytokines. A concomitant decrease in regulatory T cells and enhanced killing in a cytotoxicity assay was observed. In summary, we demonstrate that PD-1 expression is increased in T cells of patients with active myeloma, and that CT-011 enhances activated T-cell responses after DC/tumor fusion stimulation. PMID 21577144
Dendritic cell vaccination combined with CTLA4 blockade in patients with metastatic melanoma.
Okt. 2009 | Ribas, Antoni; Comin-Anduix, Begoña; Chmielowski, Bartosz; Jalil, Jason; de la Rocha, Pilar; McCannel, Tara A; Ochoa, Maria Teresa; Seja, Elizabeth; Villanueva, Arturo; Oseguera, Denise K; Straatsma, Bradley R; Cochran, Alistair J; Glaspy, John A; Hui, Liu; Marincola, Francesco M; Wang, Ena; Economou, James S; Gomez-Navarro, Jesus
Tumor antigen-loaded dendritic cells (DC) are believed to activate antitumor immunity by stimulating T cells, and CTL-associated antigen 4 (CTLA4)-blocking antibodies should release a key negative regulatory pathway on T cells. The combination was tested in a phase I clinical trial in patients with advanced melanoma. PMID 19789309
Resistance Mechanisms to Immune-Checkpoint Blockade in Cancer: Tumor-Intrinsic and -Extrinsic Factors.
Nov. 00-1 | Pitt, Jonathan M; Vétizou, Marie; Daillère, Romain; Roberti, María Paula; Yamazaki, Takahiro; Routy, Bertrand; Lepage, Patricia; Boneca, Ivo Gomperts; Chamaillard, Mathias; Kroemer, Guido; Zitvogel, Laurence
Inhibition of immune regulatory checkpoints, such as CTLA-4 and the PD-1-PD-L1 axis, is at the forefront of immunotherapy for cancers of various histological types. However, such immunotherapies fail to control neoplasia in a significant proportion of patients. Here, we review how a range of cancer-cell-autonomous cues, tumor-microenvironmental factors, and host-related influences might account for the heterogeneous responses and failures often encountered during therapies using immune-checkpoint blockade. Furthermore, we describe the emerging evidence of how the strong interrelationship between the immune system and the host microbiota can determine responses to cancer therapies, and we introduce a concept by which prior or concomitant modulation of the gut microbiome could optimize therapeutic outcomes upon immune-checkpoint blockade. PMID 27332730
Classifying Cancers Based on T-cell Infiltration and PD-L1.
Nov. 00-1 | Teng, Michele W L; Ngiow, Shin Foong; Ribas, Antoni; Smyth, Mark J
Cancer immunotherapy may become a major treatment backbone in many cancers over the next decade. There are numerous immune cell types found in cancers and many components of an immune reaction to cancer. Thus, the tumor has many strategies to evade an immune response. It has been proposed that four different types of tumor microenvironment exist based on the presence or absence of tumor-infiltrating lymphocytes and programmed death-ligand 1 (PD-L1) expression. We review this stratification and the latest in a series of results that shed light on new approaches for rationally designing ideal combination cancer therapies based on tumor immunology. PMID 25977340
The blockade of immune checkpoints in cancer immunotherapy.
Nov. 00-1 | Pardoll, Drew M
Among the most promising approaches to activating therapeutic antitumour immunity is the blockade of immune checkpoints. Immune checkpoints refer to a plethora of inhibitory pathways hardwired into the immune system that are crucial for maintaining self-tolerance and modulating the duration and amplitude of physiological immune responses in peripheral tissues in order to minimize collateral tissue damage. It is now clear that tumours co-opt certain immune-checkpoint pathways as a major mechanism of immune resistance, particularly against T cells that are specific for tumour antigens. Because many of the immune checkpoints are initiated by ligand-receptor interactions, they can be readily blocked by antibodies or modulated by recombinant forms of ligands or receptors. Cytotoxic T-lymphocyte-associated antigen 4 (CTLA4) antibodies were the first of this class of immunotherapeutics to achieve US Food and Drug Administration (FDA) approval. Preliminary clinical findings with blockers of additional immune-checkpoint proteins, such as programmed cell death protein 1 (PD1), indicate broad and diverse opportunities to enhance antitumour immunity with the potential to produce durable clinical responses. PMID 22437870
Targeting immune checkpoints in malignant glioma.
Nov. 00-1 | Zhang, Xuhao; Zhu, Shan; Li, Tete; Liu, Yong-Jun; Chen, Wei; Chen, Jingtao
Malignant glioma is the most common and a highly aggressive cancer in the central nervous system (CNS). Cancer immunotherapy, strategies to boost the body's anti-cancer immune responses instead of directly targeting tumor cells, recently achieved great success in treating several human solid tumors. Although once considered "immune privileged" and devoid of normal immunological functions, CNS is now considered a promising target for cancer immunotherapy, featuring the recent progresses in neurobiology and neuroimmunology and a highly immunosuppressive state in malignant glioma. In this review, we focus on immune checkpoint inhibitors, specifically, antagonizing monoclonal antibodies for programmed cell death protein-1 (PD-1), cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), and indoleamine 2,3-dioxygenase (IDO). We discuss advances in the working mechanisms of these immune checkpoint molecules, their status in malignant glioma, and current preclinical and clinical trials targeting these molecules in malignant glioma. PMID 27756892