Detailed analysis of immunologic effects of the cytotoxic T lymphocyte-associated antigen 4-blocking monoclonal antibody tremelimumab in peripheral blood of patients with melanoma

Immune checkpoint inhibitors and cancer immunotherapy by aptamers: an overview

Efforts in cancer immunotherapy aim to counteract evasion mechanisms and stimulate the immune system to recognise and attack cancer cells effectively. Combination therapies that target multiple aspects of immune evasion are being investigated to enhance the overall efficacy of cancer immunotherapy. PD-1 (Programmed Cell Death Protein 1), CTLA-4 (Cytotoxic T-Lymphocyte Antigen 4), LAG-3 (Lymphocyte-Activation Gene 3), and TIM-3 (T Cell Immunoglobulin and Mucin Domain-Containing Protein3) are all immune checkpoint receptors that play crucial roles in regulating the immune response and maintaining self-tolerance often exploited by cancer cells to evade immune surveillance. Antibodies targeted against immune checkpoint inhibitors such as anti-PD-1 antibodies (e.g., pembrolizumab, nivolumab), anti-CTLA-4 antibodies (e.g., Ipilimumab), and experimental drugs targeting LAG-3 and TIM-3, aim to block these interactions and unleash the immune system's ability to recognise and destroy cancer cells. The US FDA has approved different categories of immune checkpoint inhibitors that have been utilised successfully in some patients with metastatic melanoma, renal cell carcinoma, head and neck cancers, and non-small lung cancer. Although several immune checkpoint inhibitor antibodies have been developed, they exhibited immune-related adverse effects, resulting in hypophysitis, diabetes, and neurological issues. These adverse effects of antibodies can be reduced by developing aptamer against the target. Aptamers offer several advantages over traditional antibodies, such as improved specificity, reduced immunogenicity, and flexible design for reduced adverse effects that specifically target and block protein-protein or receptor-ligand interactions involved in immune checkpoint pathways. The current study aims to review the function of particular immune checkpoint inhibitors along with developed aptamer-mediated antitumor cytotoxicity in cancer treatment.

Local delivery of low-dose anti–CTLA-4 to the melanoma lymphatic basin leads to systemic T reg reduction and effector T cell activation

Preclinical studies show that locoregional CTLA-4 blockade is equally effective in inducing tumor eradication as systemic delivery, without the added risk of immune-related side effects. This efficacy is related to access of the CTLA-4 blocking antibodies to tumor-draining lymph nodes (TDLNs). Local delivery of anti–CTLA-4 after surgical removal of primary melanoma, before sentinel lymph node biopsy (SLNB), provides a unique setting to clinically assess the role of TDLN in the biological efficacy of locoregional CTLA-4 blockade. Here, we have evaluated the safety, tolerability, and immunomodulatory effects in the SLN and peripheral blood of a single dose of tremelimumab [a fully human immunoglobulin gamma-2 (IgG2) mAb directed against CTLA-4] in a dose range of 2 to 20 mg, injected intradermally at the tumor excision site 1 week before SLNB in 13 patients with early-stage melanoma (phase 1 trial; NCT04274816). Intradermal delivery was safe and well tolerated and induced activation of migratory dendritic cell (DC) subsets in the SLN. It also induced profound and durable decreases in regulatory T cell (T reg ) frequencies and activation of effector T cells in both SLN and peripheral blood. Moreover, systemic T cell responses against NY-ESO-1 or MART-1 were primed or boosted ( N = 7), in association with T cell activation and central memory T cell differentiation. These findings indicate that local administration of anti–CTLA-4 may offer a safe and promising adjuvant treatment strategy for patients with early-stage melanoma. Moreover, our data demonstrate a central role for TDLN in the biological efficacy of CTLA-4 blockade and support TDLN-targeted delivery methods.

Research Trends in Immune Checkpoint Blockade for Melanoma: Visualization and Bibliometric Analysis

Background

Melanoma is one of the most life-threatening skin cancers; immune checkpoint blockade is widely used in the treatment of melanoma because of its remarkable efficacy.

Objective

This study aimed to conduct a comprehensive bibliometric analysis of research conducted in recent decades on immune checkpoint blockade for melanoma, while exploring research trends and public interest in this topic.

Methods

We summarized the articles in the Web of Science Core Collection on immune checkpoint blockade for melanoma in each year from 1999 to 2020. The R package bibliometrix was used for data extraction and visualization of the distribution of publication year and the top 10 core authors. Keyword citation burst analysis and cocitation networks were calculated with CiteSpace. A Gunn online world map was used to evaluate distribution by country and region. Ranking was performed using the Standard Competition Ranking method. Coauthorship analysis and co-occurrence were analyzed and visualized with VOSviewer.

Results

After removing duplicates, a total of 9169 publications were included. The distribution of publications by year showed that the number of publications rose sharply from 2015 onwards and either reached a peak in 2020 or has yet to reach a peak. The geographical distribution indicated that there was a large gap between the number of publications in the United States and other countries. The coauthorship analysis showed that the 149 top institutions were grouped into 8 clusters, each covering approximately a single country, suggesting that international cooperation among institutions should be strengthened. The core author extraction revealed changes in the most prolific authors. The keyword analysis revealed clustering and top citation bursts. The cocitation analysis of references from 2010 to 2020 revealed the number of citations and the centrality of the top articles.

Conclusions

This study revealed trends in research and public interest in immune checkpoint blockade for melanoma. Our findings suggest that the field is growing rapidly, has several core authors, and that the United States is taking the lead position. Moreover, cooperation between countries should be strengthened, and future research hot spots might focus on deeper exploration of drug mechanisms, prediction of treatment efficacy, prediction of adverse events, and new modes of administration, such as combination therapy, which may pave the way for further research.

Expression of CTLA-4 and CD86 Antigens and Epstein-Barr Virus Reactivation in Chronic Lymphocytic Leukemia-Any Link with Known Prognostic Factors?

Simple Summary

Chronic lymphocytic leukemia (CLL) accounts for one-third of all leukemias. The Epstein-Barr virus (EBV) has the ability to transform B-cells into cancer cells. A history of EBV infection increases the chances of acquiring CLL and it worsens the prognosis in CLL. We tried to assess whether EBV affects the course of CLL by deregulating the CTLA-4/CD86 pathway. The expression of CTLA-4 and CD86 on immune cells in patients with CLL has been evaluated and linked to indicators of EBV infection and clinical outcomes. Our studies have shown that anergy, which is expressed by inhibition through the interaction of CTLA-4 and CD86, is an important mechanism leading to the inhibition of the antitumor response and CLL progression.

Abstract

Infection with Epstein-Barr virus (EBV) worsens the prognosis in chronic lymphocytic leukemia (CLL), but the underlying mechanisms are not yet established. We intended to assess whether EBV affects the course of CLL by the deregulation of the CTLA-4/CD86 signaling pathway. We used polymerase chain reaction to measure the load of EBV DNA in the blood of 110 newly diagnosed patients with CLL. The expression of CTLA-4 and CD86 antigen on lymphocytes was assessed with flow cytometry. Additionally, CTLA-4 and CD86 serum concentrations were measured through enzyme-linked immunosorbent assays. Fifty-four percent of the patients had detectable EBV DNA [EBV(+)]. In EBV(+) patients the CTLA-4 and CD86 serum concentrations and their expressions on investigated cell populations were significantly higher than in EBV(−) patients. EBV load correlated positively with unfavorable prognostic markers of CLL and the expression of CTLA-4 on CD3+ lymphocytes (r = 0.5339; p = 0.027) and CD86 on CD19+ cells (r = 0.6950; p < 0.001). During a median follow-up period of 32 months EBV(+) patients were more likely to require treatment or have lymphocyte doubling (p < 0.001). Among EBV(+) but not EBV(−) patients, increased expressions of CTLA-4 lymphocytes were associated with elevated risks of progression. We propose that EBV coinfection may worsen prognosis in CLL patients, partly due to EBV-induced up-regulation of CTLA-4 expression.

TriMix and tumor antigen mRNA electroporated dendritic cell vaccination plus ipilimumab: link between T-cell activation and clinical responses in advanced melanoma

Background

We previously reported that dendritic cell-based mRNA vaccination plus ipilimumab (TriMixDC-MEL IPI) results in an encouraging rate of tumor responses in patients with pretreated advanced melanoma. Here, we report the TriMixDC-MEL IPI-induced T-cell responses detected in the peripheral blood.

Methods

Monocyte-derived dendritic cells electroporated with mRNA encoding CD70, CD40 ligand, and constitutively active TLR4 (TriMix) as well as the tumor-associated antigens tyrosinase, gp100, MAGE-A3, or MAGE-C2 were administered together with IPI for four cycles. For 18/39 patients, an additional vaccine was administered before the first IPI administration. We evaluated tumor-associated antigen specific T-cell responses in previously collected peripheral blood mononuclear cells, available from 15 patients.

Results

Vaccine-induced enzyme-linked immunospot assay responses detected after in vitro T-cell stimulation were shown in 12/15 patients. Immune responses detected in patients with a complete or partial response were significantly stronger and broader, and exhibited a higher degree of multifunctionality compared with responses in patients with stable or progressive disease. CD8+ T-cell responses from patients with an ongoing clinical response, either elicited by TriMixDC-MEL IPI or on subsequent pembrolizumab treatment, exhibited the highest degree of multifunctionality.

Conclusions

TriMixDC-MEL IPI treatment results in robust CD8+ T-cell responses in a meaningful portion of stage III or IV melanoma patients, and obviously in patients with a clinical response. The levels of polyfunctional and multiantigen T-cell responses measured in patients with a complete response, particularly in patients evidently cured after 5+ years of follow-up, may provide a benchmark for the level of immune stimulation needed to achieve a durable clinical remission.

Trial registration number

NCT01302496.

Biomarkers, measured during therapy, for response of melanoma patients to immune checkpoint inhibitors: a systematic review

Immune checkpoint inhibitors (ICIs), which target CTLA-4 or PD-(L)1 molecules, have shown impressive therapeutic results. Durable responses, however, are only observed in a segment of the patient population and must be offset against severe off-target immune toxicity and high costs. This calls for biomarkers that predict response during ICI treatment. Although many candidate biomarkers exist, as yet, there has been no systematic overview of biomarkers predictive during. Here, we provide a systematic review of the current literature of ICI treatment to establish an overview of candidate predictive biomarkers during ICI treatment in melanoma patients. We performed a systematic Medline search (2000-2018, 1 January) on biomarkers for survival or response to ICI treatment in melanoma patients. We retrieved 735 publications, of which 79 were finally included in this systematic review. Blood markers were largely studied for CTLA-4 ICI, whereas tumor tissue markers were analyzed for PD-(L)1 ICI. Blood cytology and soluble factors were more frequently correlated to overall survival (OS) than response, indicating their prognostic rather than predictive nature. An increase in tumor-infiltrating CD8 + T-cells and a decrease in regulatory T-cells were correlated to response, in addition to mutational load, neoantigen load, and immune-related gene expression. Immune-related adverse events were also associated frequently with a favorable response and OS. This review shows the great variety of potential biomarkers published to date, in an attempt to better understand response to ICI therapy; it also highlights the candidate markers for future research. The most promising biomarkers for response to ICI treatment are the occurrence of immune-related adverse events (especially vitiligo), lowering of lactate dehydrogenase, and increase in activated CD8 + and decrease in regulatory T-cells.

Dose dependence of treatment-related adverse events for immune checkpoint inhibitor therapies: a model-based meta-analysis

Programmed cell death-1 (PD-1) and/or cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) immune checkpoint inhibitor (ICI) treatments are associated with adverse events (AEs), which may be dependent on ICI dose. Applying a model-based meta-analysis to evaluate safety data from published clinical trials from 2005 to 2018, we analyzed the dose/exposure dependence of ICI treatment-related AE (trAE) and immune-mediated AE (imAE) rates. Unlike with PD-1 inhibitor monotherapy, CTLA-4 inhibitor monotherapy exhibited a dose/exposure dependence on most AE types evaluated. Furthermore, combination therapy with PD-1 inhibitor significantly strengthened the dependence of trAE and imAE rates on CTLA-4 inhibitor dose/exposure.

Shuffling the deck with CTLA-4 therapy: Deep sequencing of rearranged TCRB genes demonstrates T cell repertoire remodeling in cancer patients

CTLA-4 inhibition produces durable T cell-driven antitumor responses, but understanding which patients achieve a long-term benefit remains unclear. Deep sequencing of rearranged T cell receptor β (TCRβ) genes can monitor the effects of CTLA-4 inhibition and potentially identify patients with long-term survival.

CTLA-4: a moving target in immunotherapy

CD28 and CTLA-4 are members of a family of immunoglobulin-related receptors that are responsible for various aspects of T-cell immune regulation. The family includes CD28, CTLA-4, and ICOS as well as other proteins, including PD-1, BTLA, and TIGIT. These receptors have both stimulatory (CD28, ICOS) and inhibitory roles (CTLA-4, PD-1, BTLA, and TIGIT) in T-cell function. Increasingly, these pathways are targeted as part of immune modulatory strategies to treat cancers, referred to generically as immune checkpoint blockade, and conversely to treat autoimmunity and CTLA-4 deficiency. Here, we focus on the biology of the CD28/CTLA-4 pathway as a framework for understanding the impacts of therapeutic manipulation of this pathway.

Trial watch: Immune checkpoint blockers for cancer therapy

Immune checkpoint blockers (ICBs) are literally revolutionizing the clinical management of an ever more diversified panel of oncological indications. Although considerable attention persists around the inhibition of cytotoxic T lymphocyte-associated protein 4 (CTLA4) and programmed cell death 1 (PDCD1, best known as PD-1) signaling, several other co-inhibitory T-cell receptors are being evaluated as potential targets for the development of novel ICBs. Moreover, substantial efforts are being devoted to the identification of biomarkers that reliably predict the likelihood of each patient to obtain clinical benefits from ICBs in the absence of severe toxicity. Tailoring the delivery of specific ICBs or combinations thereof to selected patient populations in the context of precision medicine programs constitutes indeed a major objective of the future of ICB-based immunotherapy. Here, we discuss recent preclinical and clinical advances on the development of ICBs for oncological indications.

Neurological adverse events associated with immune checkpoint inhibitors: Review of the literature

Immune checkpoint inhibitors (ICIs) targeting CTLA4 and PD1 constitute a promising class of cancer treatment but are associated with several immune-related disorders. We here review the literature reporting neurological adverse events (nAEs) associated with ICIs. A systematic search of literature, up to February 2016, mentioning nAEs in patients treated with ICIs was conducted. Eligible studies included case reports and prospective trials. One case seen in our ward was also added. Within the 59 clinical trials (totalling 9208 patients) analysed, the overall incidence of nAEs was 3.8% with anti-CTLA4 antibodies, 6.1% with anti-PD1 antibodies, and 12.0% with the combination of both. The clinical spectrum of neurological disorders was highly heterogeneous. Most of these nAEs were grade 1-2 and consisted of non-specific symptoms such as headache (55%). The incidence of high grade nAEs was below 1% for all types of treatment. Headaches, encephalopathies and meningitis were the most commonly reported (21%, 19% and 15%, respectively). Among the 27 case reports, the most common nAEs were encephalopathies, meningoradiculoneuritis, Guillain-Barré like syndromes and myasthenic syndromes. The median time of nAEs onset was 6 weeks. In most cases, drug interruption and steroids led to neurological recovery, even in conditions where steroids are not usually recommended such as Guillain-Barré syndrome.

Quantifying in vivo murine antigen-specific T cell responses without requirement for prior knowledge of antigen identity

Extracorporeal Photochemotherapy (ECP) is a widely applied anti-cancer immunotherapy for patients with cutaneous T cell lymphoma (CTCL). By using apoptotic malignant cells as a source of patient-specific tumor antigen, it enables clinically relevant and curative anti-CTCL immunity, with potential efficacy in other tumors. Currentmethods to track patient-specific responses are tedious, and new methods are needed to assess putative global immunity. We developed a clinically practical method to assess antigen-specific T cell activation that does not rely on knowledge of the particular antigen, thereby eliminating the requirement for patient-specific reagents. In the OT-I transgenic murine system, we quantified calcium flux to reveal early T cell engagement by antigen presenting cells constitutively displaying a model antigenic peptide, ovalbumin (OVA)-derived SIINFEKL. We detected calcium flux in OVA-specific T cells, triggered by specific T cell receptor engagement by SIINFEKL peptide-loaded DC. This approach led to sensitive detection of antigen-specific calcium flux (ACF) down to a peptide-loading concentration of ∼10^-3uM and at a frequency of ∼0.1% OT-I cells among wild-type (WT), non-responding cells. Antigen-specific T cells were detected in spleen, lymph nodes, and peripheral blood after adoptive transfer into control recipient mice. Methods like this for assessing therapeutic response are lacking in patients currently on immune-based therapies, such as ECP, where assessment of clinical response is made by delayed measurement of the size of the malignant clone. These findings suggest an early, practical way to measure therapeutically-induced anti-tumor responses in ECP-treated patients that have been immunized against their malignant cells.

Tremelimumab: research and clinical development

The immune checkpoint therapy is a relatively recent strategy that aims to tweak the immune system to effectively attack cancer cells. The understanding of the immune responses and their regulation at the intracellular level and the development of fully humanized monoclonal antibodies are the pillars of an approach that could elicit durable clinical responses and even remission in some patients with cancer. Most of the immune checkpoints that regulate the T-cell responses (activation and inhibition) operate through proteins present on the cytoplasmic membrane of the immune cells. Therefore, specific antibodies capable of blocking the inhibitory signals should lead to unrestrained immune responses that supersede the inhibitory mechanisms, which are naturally present in the tumor microenviroment. The best-known and most successful targets for immune checkpoint therapy are the cytotoxic T-lymphocyte antigen-4 and programmed cell death-1 coreceptors. Tremelimumab (CP-675,206) is a fully humanized monoclonal antibody specific for cytotoxic T-lymphocyte antigen-4, which has been successfully used to treat patients with metastatic melanoma and some other cancers. Although still a work in progress, the use of tremelimumab as an immune checkpoint therapeutic agent is a promising approach alone or in combination with other anticancer drugs. Here, we review the use of this antibody in a number of clinical trials against solid tumors.

Ipilimumab reshapes T cell memory subsets in melanoma patients with clinical response

PURPOSE

Therapy targeting CTLA-4 immune checkpoint provides increased survival in patients with advanced melanoma. However, immunotherapy is frequently associated with delayed and heterogeneous clinical responses and it is important to identify prognostic immunological correlates of clinical endpoints.

EXPERIMENTAL DESIGN

77 patients with stage III/IV melanoma were treated with ipilimumab alone every 3 weeks, during 9 weeks. Blood samples were collected at the baseline and before each dose for in depth immune monitoring.

RESULTS

The median follow-up was 28 mo with a median survival of 7 mo. Survival and clinical benefit were significantly improved when absolute lymphocyte count at the baseline was above 1 × 10(9)/L. Notably, ipilimumab had a global effect on memory T cells, with an early increase of central and effector subsets in patients with disease control. By contrast, percentages of stem cell memory T cells (TSCM) gradually decreased despite stable absolute counts and sustained proliferation, suggesting a process of differentiation. Higher proportions of eomes(+) and Ki-67(+) T cells were observed, with enhanced skin homing potential and induction of cytotoxic markers.

CONCLUSION

These results suggest that CTLA-4 blockade is able to reshape the memory subset with the potential involvement of Eomes and memory subsets including TSCM.

PD-1 Blockade Expands Intratumoral Memory T Cells

Tumor responses to programmed cell death protein 1 (PD-1) blockade therapy are mediated by T cells, which we characterized in 102 tumor biopsies obtained from 53 patients treated with pembrolizumab, an antibody to PD-1. Biopsies were dissociated, and single-cell infiltrates were analyzed by multicolor flow cytometry using two computational approaches to resolve the leukocyte phenotypes at the single-cell level. There was a statistically significant increase in the frequency of T cells in patients who responded to therapy. The frequency of intratumoral B cells and monocytic myeloid-derived suppressor cells significantly increased in patients' biopsies taken on treatment. The percentage of cells with a regulatory T-cell phenotype, monocytes, and natural killer cells did not change while on PD-1 blockade therapy. CD8(+) memory T cells were the most prominent phenotype that expanded intratumorally on therapy. However, the frequency of CD4(+) effector memory T cells significantly decreased on treatment, whereas CD4(+) effector T cells significantly increased in nonresponding tumors on therapy. In peripheral blood, an unusual population of blood cells expressing CD56 was detected in two patients with regressing melanoma. In conclusion, PD-1 blockade increases the frequency of T cells, B cells, and myeloid-derived suppressor cells in tumors, with the CD8(+) effector memory T-cell subset being the major T-cell phenotype expanded in patients with a response to therapy.

PD-1 Blockade Expands Intratumoral Memory T Cells

Tumor responses to programmed cell death protein 1 (PD-1) blockade therapy are mediated by T cells, which we characterized in 102 tumor biopsies obtained from 53 patients treated with pembrolizumab, an antibody to PD-1. Biopsies were dissociated, and single-cell infiltrates were analyzed by multicolor flow cytometry using two computational approaches to resolve the leukocyte phenotypes at the single-cell level. There was a statistically significant increase in the frequency of T cells in patients who responded to therapy. The frequency of intratumoral B cells and monocytic myeloid-derived suppressor cells significantly increased in patients' biopsies taken on treatment. The percentage of cells with a regulatory T-cell phenotype, monocytes, and natural killer cells did not change while on PD-1 blockade therapy. CD8(+) memory T cells were the most prominent phenotype that expanded intratumorally on therapy. However, the frequency of CD4(+) effector memory T cells significantly decreased on treatment, whereas CD4(+) effector T cells significantly increased in nonresponding tumors on therapy. In peripheral blood, an unusual population of blood cells expressing CD56 was detected in two patients with regressing melanoma. In conclusion, PD-1 blockade increases the frequency of T cells, B cells, and myeloid-derived suppressor cells in tumors, with the CD8(+) effector memory T-cell subset being the major T-cell phenotype expanded in patients with a response to therapy.

Metastatic melanoma treatment: Combining old and new therapies

Metastatic melanoma is an aggressive form of cancer characterised by poor prognosis and a complex etiology. Until 2010, the treatment options for metastatic melanoma were very limited. Largely ineffective dacarbazine, temozolamide or fotemustine were the only agents in use for 35 years. In recent years, the development of molecularly targeted inhibitors in parallel with the development of checkpoint inhibition immunotherapies has rapidly improved the outcomes for metastatic melanoma patients. Despite these new therapies showing initial promise; resistance and poor duration of response have limited their effectiveness as monotherapies. Here we provide an overview of the history of melanoma treatment, as well as the current treatments in development. We also discuss the future of melanoma treatment as we go beyond monotherapies to a combinatorial approach. Combining older therapies with the new molecular and immunotherapies will be the most promising way forward for treatment of metastatic melanoma.

Diverse Functions of Plasma PAF-AH in Tumorigenesis

This chapter is focused on the role of the plasma form of platelet-activating factor-acetylhydrolase (PAF-AH), heretofore referred to as PAF-AH, in tumorigenic responses. Biochemical and other properties of this enzyme were discussed in detail in chapter "Plasma PAF-AH (PLA2G7): Biochemical Properties, Association with LDLs and HDLs, and Regulation of Expression" by Stafforini and in other chapters. Although phospholipases tend not to be drivers of tumorigenesis themselves, these enzymes and the lipid mediators whose levels they regulate interact with a variety of oncogenes and tumor suppressors [1]. Like other phospholipases, the functions of PAF-AH in cancer likely are related to its ability to regulate the levels of lipid mediators that participate in cellular processes related to initial tumorigenic events (e.g., proliferation, growth, inflammation) and/or spreading of the disease (e.g., matrix metalloproteinase secretion, actin cytoskeleton reorganization, migration, and angiogenesis) [1]. The importance of substrates and products of PAF-AH on key cellular functions has been evaluated in cell-based analyses which revealed that these metabolites can have pro- and antitumorigenic functions. Studies in genetically engineered mice lacking PAF-AH expression and genetic manipulation of PAF-AH levels in cancer cells demonstrated diverse functions of the protein in models of melanoma, prostate cancer, colon cancer, and others. The following sections highlight lessons learned from studies in cell lines and in mouse models regarding the diversity of functions of PAF-AH in cancer, and the potential of PAFAH transcripts, protein, and/or activity levels to become cancer biomarkers and therapeutic targets.

Co-Stimulatory Blockade of the CD28/CD80-86/CTLA-4 Balance in Transplantation: Impact on Memory T Cells?

CD28 and CTLA-4 are prototypal co-stimulatory and co-inhibitory cell surface signaling molecules interacting with CD80/86, known to be critical for immune response initiation and regulation, respectively. Initial “bench-to-beside” translation, two decades ago, resulted in the development of CTLA4-Ig, a biologic that targets CD80/86 and prevents T-cell costimulation. In spite of its proven effectiveness in inhibiting allo-immune responses, particularly in murine models, clinical experience in kidney transplantation with belatacept (high-affinity CTLA4-Ig molecule) reveals a high incidence of acute, cell-mediated rejection. Originally, the etiology of belatacept-resistant graft rejection was thought to be heterologous immunity, i.e., the cross-reactivity of the pool of memory T cells from pathogen-specific immune responses with alloantigens. Recently, the standard view that memory T cells arise from effector cells after clonal contraction has been challenged by a “developmental” model, in which less differentiated memory T cells generate effector cells. This review delineates how this shift in paradigm, given the differences in co-stimulatory and co-inhibitory signal depending on the maturation stage, could profoundly affect our understanding of the CD28/CD80-86/CTLA-4 blockade and highlights the potential advantages of selectively targeting CD28, instead of CD80/86, to control post-transplant immune responses.

Out-of-Sequence Signal 3 Paralyzes Primary CD4(+) T-Cell-Dependent Immunity

Primary T cell activation involves the integration of three distinct signals delivered in sequence: (1) antigen recognition, (2) costimulation, and (3) cytokine-mediated differentiation and expansion. Strong immunostimulatory events such as immunotherapy or infection induce profound cytokine release causing "bystander" T cell activation, thereby increasing the potential for autoreactivity and need for control. We show that during strong stimulation, a profound suppression of primary CD4(+) T-cell-mediated immune responses ensued and was observed across preclinical models and patients undergoing high-dose interleukin-2 (IL-2) therapy. This suppression targeted naive CD4(+) but not CD8(+) T cells and was mediated through transient suppressor of cytokine signaling-3 (SOCS3) inhibition of the STAT5b transcription factor signaling pathway. These events resulted in complete paralysis of primary CD4(+) T cell activation, affecting memory generation and induction of autoimmunity as well as impaired viral clearance. These data highlight the critical regulation of naive CD4(+) T cells during inflammatory conditions.

The past, present and future of immunotherapy against tumor

Tumor is one of the most common lethal diseases in the world. Current progress of therapy remains insufficient survival benefit. Tumor immunotherapies have been proposed for more than a century. With the improvement in the understanding of the role of the immune system in the tumorigenesis and immune response to tumor, immunotherapy has obtained a rapid development and plays the significant role in tumor therapy nowadays. This review designs to provide a general overview of immunotherapy in tumors. We will introduce the landmark events in the past research of immunotherapy and elaborate a range of strategies using different immune response mechanism, which have been demonstrated successfully and even some of them have been approved by US Food and Drug Administration (FDA) to certain tumor therapy. Finally, we will discuss the future direction of immunotherapy so that we can predict the possible and valuable strategies for future tumor therapy.

Immune-related strategies driving immunotherapy in breast cancer treatment: a real clinical opportunity

Because its original use as a treatment for hematologic disease, more recently immunotherapy has emerged as a novel effective therapeutic strategy for solid malignancies, such as melanoma and prostate carcinoma. For breast carcinoma, an immunologic therapeutic approach has not been well evaluated, even though there is evidence to suggest it would be a successful novel strategy, especially taking into account the high mortality rate of the most aggressive variants of this heterogeneous disease. Here, we briefly describe the most recently awarded immune-based therapies with a consolidated or potential implication for the treatment of solid malignancies. We focus on immune checkpoints and on the clinical potential of their abrogation, with a further overview of novel vaccine-based approaches and the most relevant immunotherapeutic techniques. We aim to provide an exhaustive review of the most promising immune-therapeutic agents that may have implications for breast cancer treatment.

Improved survival with T cell clonotype stability after anti-CTLA-4 treatment in cancer patients

Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) blockade can promote antitumor T cell immunity and clinical responses. The mechanism by which anti-CTLA-4 antibodies induces antitumor responses is controversial. To determine the effects of CTLA-4 blockade on the T cell repertoire, we used next-generation deep sequencing to measure the frequency of individual rearranged T cell receptor β (TCRβ) genes, thereby characterizing the diversity of rearrangements, known as T cell clonotypes. CTLA-4 blockade in patients with metastatic castration-resistant prostate cancer and metastatic melanoma resulted in both expansion and loss of T cell clonotypes, consistent with a global turnover of the T cell repertoire. Overall, this treatment increased TCR diversity as reflected in the number of unique TCR clonotypes. The repertoire of clonotypes continued to evolve over subsequent months of treatment. Whereas the number of clonotypes that increased with treatment was not associated with clinical outcome, improved overall survival was associated with maintenance of high-frequency clones at baseline. In contrast, the highest-frequency clonotypes fell with treatment in patients with short overall survival. Stably maintained clonotypes included T cells having high-avidity TCR such as virus-reactive T cells. Together, these results suggest that CTLA-4 blockade induces T cell repertoire evolution and diversification. Moreover, improved clinical outcomes are associated with less clonotype loss, consistent with the maintenance of high-frequency TCR clonotypes during treatment. These clones may represent the presence of preexisting high-avidity T cells that may be relevant in the antitumor response.

Developing biomarker-specific end points in lung cancer clinical trials

In cancer-drug development, a number of different end points have been used to establish efficacy and support regulatory approval, such as overall survival, progression-free survival (PFS), and radiographic response rate. However, these traditional end points have important limitations. For example, in lung cancer clinical trials, evaluating overall survival end points is a protracted process and these end points are most reliable when crossover to the investigational therapy is not permitted. Furthermore, although radiographic surrogate end points, such as PFS and response rate, generally correlate with clinical benefit in the setting of cytotoxic chemotherapy and molecular targeted therapies, novel immunotherapies might have atypical response kinetics, which confounds radiographic interpretation. In this Review, we discuss the need to develop alternative or surrogate end points for lung cancer clinical trials, and focus on several new biomarkers that could serve as surrogate end points, including functional imaging biomarkers, circulating factors (tumour proteins, DNA, and cells), and pharmacodynamic tumour markers. By enabling the size, duration, and complexity of cancer trials to be reduced, biomarker end points hold the promise to accelerate drug development and improve patient outcomes.

Anti-CTLA-4 therapy broadens the melanoma-reactive CD8+ T cell response

Anti-CTLA-4 treatment improves the survival of patients with advanced-stage melanoma. However, although the anti-CTLA-4 antibody ipilimumab is now an approved treatment for patients with metastatic disease, it remains unknown by which mechanism it boosts tumor-specific T cell activity. In particular, it is unclear whether treatment amplifies previously induced T cell responses or whether it induces new tumor-specific T cell reactivities. Using a combination ultraviolet (UV)-induced peptide exchange and peptide-major histocompatibility complex (pMHC) combinatorial coding, we monitored immune reactivity against a panel of 145 melanoma-associated epitopes in a cohort of patients receiving anti-CTLA-4 treatment. Comparison of pre- and posttreatment T cell reactivities in peripheral blood mononuclear cell samples of 40 melanoma patients demonstrated that anti-CTLA-4 treatment induces a significant increase in the number of detectable melanoma-specific CD8 T cell responses (P = 0.0009). In striking contrast, the magnitude of both virus-specific and melanoma-specific T cell responses that were already detected before start of therapy remained unaltered by treatment (P = 0.74). The observation that anti-CTLA-4 treatment induces a significant number of newly detected T cell responses-but only infrequently boosts preexisting immune responses-provides strong evidence for anti-CTLA-4 therapy-enhanced T cell priming as a component of the clinical mode of action.

Distinct immunological mechanisms of CTLA-4 and PD-1 blockade revealed by analyzing TCR usage in blood lymphocytes

Targeting immune inhibitory receptors has brought excitement, innovation and hope to cancer patients. Our recent work revealed the immunological effects of blocking the CTLA4 and PD-1 immune checkpoints on T cell receptor usage among peripheral blood cells, and further uncovers how the expansion of the T cell repertoire matches the immunotoxicity profile of the therapy.

CTLA4 blockade broadens the peripheral T-cell receptor repertoire

PURPOSE

To evaluate the immunomodulatory effects of cytotoxic T-lymphocyte-associated protein 4 (CTLA4) blockade with tremelimumab in peripheral blood mononuclear cells (PBMC).

EXPERIMENTAL DESIGN

We used next-generation sequencing to study the complementarity-determining region 3 (CDR3) from the rearranged T-cell receptor (TCR) variable beta (V-beta) in PBMCs of 21 patients, at baseline and 30 to 60 days after receiving tremelimumab.

RESULTS

After receiving tremelimumab, there was a median of 30% increase in unique productive sequences of TCR V-beta CDR3 in 19 out of 21 patients, and a median decrease of 30% in only 2 out of 21 patients. These changes were significant for richness (P = 0.01) and for Shannon index diversity (P = 0.04). In comparison, serially collected PBMCs from four healthy donors did not show a significant change in TCR V-beta CDR3 diversity over 1 year. There was a significant difference in the total unique productive TCR V-beta CDR3 sequences between patients experiencing toxicity with tremelimumab compared with patients without toxicity (P = 0.05). No relevant differences were noted between clinical responders and nonresponders.

CONCLUSIONS

CTLA4 blockade with tremelimumab diversifies the peripheral T-cell pool, representing a pharmacodynamic effect of how this class of antibodies modulates the human immune system.

Blood mRNA expression profiling predicts survival in patients treated with tremelimumab

PURPOSE

Tremelimumab (ticilimumab, Pfizer), is a monoclonal antibody (mAb) targeting cytotoxic T lymphocyte-associated antigen-4 (CTLA-4). Ipilimumab (Yervoy, BMS), another anti-CTLA-4 antibody, is approved by the U.S. Federal Drug Administration (FDA). Biomarkers are needed to identify the subset of patients who will achieve tumor control with CTLA-4 blockade.

EXPERIMENTAL DESIGN

Pretreatment peripheral blood samples from 218 patients with melanoma who were refractory to prior therapy and receiving tremelimumab in a multicenter phase II study were measured for 169 mRNA transcripts using reverse transcription polymerase chain reaction (RT-PCR). A two-class latent model yielded a risk score based on four genes that were highly predictive of survival (P < 0.001). This signature was validated in an independent population of 260 treatment-naïve patients with melanoma enrolled in a multicenter phase III study of tremelimumab.

RESULTS

Median follow-up was 297 days for the training population and 386 days for the test population. Expression levels of the 169 genes were closely correlated across the two populations (r = 0.9939). A four-gene model, including cathepsin D (CTSD), phopholipase A2 group VII (PLA2G7), thioredoxin reductase 1 (TXNRD1), and interleukin 1 receptor-associated kinase 3 (IRAK3), predicted survival in the test population (P = 0.001 by log-rank test). This four-gene model added to the predictive value of clinical predictors (P < 0.0001).

CONCLUSIONS

Expression levels of CTSD, PLA2G7, TXNRD1, and IRAK3 in peripheral blood are predictive of survival in patients with melanoma treated with tremelimumab. Blood mRNA signatures should be further explored to define patient subsets likely to benefit from immunotherapy.

Adoptive transfer of MART-1 T-cell receptor transgenic lymphocytes and dendritic cell vaccination in patients with metastatic melanoma

PURPOSE

It has been demonstrated that large numbers of tumor-specific T cells for adoptive cell transfer (ACT) can be manufactured by retroviral genetic engineering of autologous peripheral blood lymphocytes and expanding them over several weeks. In mouse models, this therapy is optimized when administered with dendritic cell (DC) vaccination. We developed a short 1-week manufacture protocol to determine the feasibility, safety, and antitumor efficacy of this double cell therapy.

EXPERIMENTAL DESIGN

A clinical trial (NCT00910650) adoptively transferring MART-1 T-cell receptor (TCR) transgenic lymphocytes together with MART-1 peptide-pulsed DC vaccination in HLA-A2.1 patients with metastatic melanoma. Autologous TCR transgenic cells were manufactured in 6 to 7 days using retroviral vector gene transfer, and reinfused with (n = 10) or without (n = 3) prior cryopreservation.

RESULTS

A total of 14 patients with metastatic melanoma were enrolled and 9 of 13 treated patients (69%) showed evidence of tumor regression. Peripheral blood reconstitution with MART-1-specific T cells peaked within 2 weeks of ACT, indicating rapid in vivo expansion. Administration of freshly manufactured TCR transgenic T cells resulted in a higher persistence of MART-1-specific T cells in the blood as compared with cryopreserved. Evidence that DC vaccination could cause further in vivo expansion was only observed with ACT using noncryopreserved T cells.

CONCLUSION

Double cell therapy with ACT of TCR-engineered T cells with a very short ex vivo manipulation and DC vaccines is feasible and results in antitumor activity, but improvements are needed to maintain tumor responses.

Markers for anti-cytotoxic T-lymphocyte antigen 4 (CTLA-4) therapy in melanoma

Therapeutic strategies that block Cytotoxic T lymphocyte antigen-4 (CTLA-4) enhance antitumor immunity and prolong the lives of patients with metastatic melanoma. However, only a subset of patients benefit, and responses are often delayed due to heterogeneous response kinetics. Ongoing monitoring of the immunologic effects of therapy and correlating these immunologic changes with patient outcomes continue to be important goals to better identify possible mechanisms of clinical activity of these agents. This chapter introduces the major areas of investigation in monitoring patients treated with CTLA-4 blockade and provides specific details of our experience performing selected assays.

Natural killer T cells in advanced melanoma patients treated with tremelimumab

A significant barrier to effective immune clearance of cancer is loss of antitumor cytotoxic T cell activity. Antibodies to block pro-apoptotic/downmodulatory signals to T cells are currently being tested. Because invariant natural killer T cells (iNKT) can regulate the balance of Th1/Th2 cellular immune responses, we characterized the frequencies of circulating iNKT cell subsets in 21 patients with melanoma who received the anti-CTLA4 monoclonal antibody tremelimumab alone and 8 patients who received the antibody in combination with MART-1_26–35 peptide-pulsed dendritic cells (MART-1/DC). Blood T cell phenotypes and functionality were characterized by flow cytometry before and after treatment. iNKT cells exhibited the central memory phenotype and showed polyfunctional cytokine production. In the combination treatment group, high frequencies of pro-inflammatory Th1 iNKT CD8⁺ cells correlated with positive clinical responses. These results indicate that iNKT cells play a critical role in regulating effective antitumor T cell activity.

Evolution of clinical trial design in early drug development: systematic review of expansion cohort use in single-agent phase I cancer trials

PURPOSE

To evaluate the use and objectives of expansion cohorts in phase I cancer trials and to explore trial characteristics associated with their use.

METHODS

We performed a systematic review of MEDLINE and EMBASE, limiting studies to single-agent phase I trials recruiting adults and published after 2006. Eligibility assessment and data extraction were performed by two reviewers. Data were assessed descriptively, and associations were tested by univariable and multivariable logistic regression.

RESULTS

We identified 611 unique phase I cancer trials, of which 149 (24%) included an expansion cohort. The trials were significantly more likely to use an expansion cohort if they were published more recently, were multicenter, or evaluated a noncytotoxic agent. Objectives of the expansion cohort were reported in 74% of trials. In these trials, safety (80%), efficacy (45%), pharmacokinetics (28%), pharmacodynamics (23%), and patient enrichment (14%) were cited as objectives. Among expansion cohorts with safety objectives, the recommended phase II dose was modified in 13% and new toxicities were described in 54% of trials. Among trials aimed at assessing efficacy, only 11% demonstrated antitumor activity assessed by response criteria that was not previously observed during dose escalation.

CONCLUSION

The utilization of expansion cohorts has increased with time. Safety and efficacy are common objectives, but 26% fail to report explicit aims. Expansion cohorts may provide useful supplementary data for phase I trials, particularly with regard to toxicity and definition of recommended dose for phase II studies.

Tremelimumab: a review of development to date in solid tumors

Tremelimumab is an investigational, fully human IgG monoclonal antibody directed against CTLA-4, a coinhibitory receptor that represses effector T-cell activity in cancer. Tremelimumab has produced promising anticancer responses in early clinical trials. However, a phase III trial of tremelimumab monotherapy versus chemotherapy in advanced melanoma was stopped early when no statistically significant difference in overall survival was observed between the two interventions. This article describes tremelimumab's putative mechanism of action, its preclinical pharmacology and clinical results to date across a range of cancer settings as monotherapy, as well as in combination with other therapies. The failure of the Phase III trial in melanoma is examined and factors affecting the possible future clinical development of tremelimumab are also explored.

Multifunctional T-cell analyses to study response and progression in adoptive cell transfer immunotherapy

Adoptive cell transfer (ACT) of genetically engineered T cells expressing cancer-specific T-cell receptors (TCR) is a promising cancer treatment. Here, we investigate the in vivo functional activity and dynamics of the transferred cells by analyzing samples from 3 representative patients with melanoma enrolled in a clinical trial of ACT with TCR transgenic T cells targeted against the melanosomal antigen MART-1. The analyses included evaluating 19 secreted proteins from individual cells from phenotypically defined T-cell subpopulations, as well as the enumeration of T cells with TCR antigen specificity for 36 melanoma antigens. These analyses revealed the coordinated functional dynamics of the adoptively transferred, as well as endogenous, T cells, and the importance of highly functional T cells in dominating the antitumor immune response. This study highlights the need to develop approaches to maintaining antitumor T-cell functionality with the aim of increasing the long-term efficacy of TCR-engineered ACT immunotherapy.

SIGNIFICANCE

A longitudinal functional study of adoptively transferred TCR–engineered lymphocytes yielded revealing snapshots for understanding the changes of antitumor responses over time in ACT immunotherapy of patients with advanced melanoma.

CTLA-4 blockade in tumor models: an overview of preclinical and translational research

Cytotoxic T lymphocyte antigen-4 (CTLA-4) is a key negative regulator of T cell activation. A complex integration of positive and negative co-stimulatory signals in the well-defined B7:CD28/CTLA-4 pathway modulates the generation and maintenance of immune responses. Inhibiting negative regulation through binding of CTLA-4 has been shown to promote stimulation of adaptive immunity and potentiation of T cell activation. CTLA-4-blocking antibodies have demonstrated efficacy in various murine malignancy models when administered as monotherapy; additionally, they have shown synergistic anti-tumor activity when utilized with other agents, such as vaccines, chemotherapy, and radiation. Preclinical studies have supported the rationale for current clinical development of anti-CTLA-4 antibodies, including ipilimumab and tremelimumab, as novel therapeutic strategies to augment anti-tumor immunity in cancer. Both ipilimumab and tremelimumab have been evaluated extensively in melanoma; notably, ipilimumab was recently approved as monotherapy for the treatment of advanced melanoma. Tremelimumab is currently undergoing evaluation in phase II trials as monotherapy in melanoma and malignant mesothelioma, while ipilimumab is under clinical investigation in phase II and III trials in various tumor types, including in melanoma, prostate, and lung cancers as monotherapy and with other therapeutic modalities, such as chemotherapy and radiation. In this review, we will provide a detailed overview of preclinical advances that have delineated many features of CTLA-4 and have helped define its role in T cell response. We will also highlight clinical application of anti-CTLA-4 therapy in cancer and describe knowledge gaps that future studies may address.

Unmasking the immune recognition of prostate cancer with CTLA4 blockade

Although cancer cells can be immunogenic, tumour progression is associated with the evasion of immunosurveillance, the promotion of tumour tolerance and even the production of pro-tumorigenic factors by immune cells. Cytotoxic T lymphocyte-associated antigen 4 (CTLA4) represents a crucial immune checkpoint, the blockade of which can potentiate anti-tumour immunity. CTLA4-blocking antibodies are now an established therapeutic approach for malignant melanoma, and clinical trials with CTLA4-specific antibodies in prostate cancer have also shown clinical activity. This treatment may provide insights into the targets that the immune system recognizes to drive tumour regression, and could potentially improve both outcome and toxicity for patients with prostate cancer.

Immunomodulation by imiquimod in patients with high-risk primary melanoma

Imiquimod is a synthetic Toll-like receptor 7 (TLR7) agonist approved for the topical treatment of actinic keratoses, superficial basal cell carcinoma, and genital warts. Imiquimod leads to an 80–100% cure rate of lentigo maligna, but studies of invasive melanoma are lacking. We conducted a pilot study to characterize the local, regional, and systemic immune responses induced by imiquimod in patients with high-risk melanoma. After treatment of the primary melanoma biopsy site with placebo or imiquimod cream, we measured immune responses in the treated skin, sentinel lymph nodes (SLN), and peripheral blood. Treatment of primary melanomas with 5% imiquimod cream was associated with an increase in both CD4+ and CD8+ T cells in the skin, and CD4+ T cells in the SLN. Most of the CD8+ T cells in the skin were CD25 negative. We could not detect any increases in CD8+ T cells specifically recognizing HLA-A*0201-restricted melanoma epitopes in the peripheral blood. The findings from this small pilot study demonstrate that topical imiquimod treatment results in enhanced local and regional T cell numbers in both the skin and SLN. Further research into TLR7 immunomodulating pathways as a basis for effective immunotherapy against melanoma in conjunction with surgery is warranted.

A clinical microchip for evaluation of single immune cells reveals high functional heterogeneity in phenotypically similar T cells

Cellular immunity has an inherent high level of functional heterogeneity. Capturing the full spectrum of these functions requires analysis of large numbers of effector molecules from single cells. We report a microfluidic platform designed for highly multiplexed (more than ten proteins), reliable, sample-efficient (∼1 × 10(4) cells) and quantitative measurements of secreted proteins from single cells. We validated the platform by assessment of multiple inflammatory cytokines from lipopolysaccharide (LPS)-stimulated human macrophages and comparison to standard immunotechnologies. We applied the platform toward the ex vivo quantification of T cell polyfunctional diversity via the simultaneous measurement of a dozen effector molecules secreted from tumor antigen-specific cytotoxic T lymphocytes (CTLs) that were actively responding to tumor and compared against a cohort of healthy donor controls. We observed profound, yet focused, functional heterogeneity in active tumor antigen-specific CTLs, with the major functional phenotypes quantitatively identified. The platform represents a new and informative tool for immune monitoring and clinical assessment.

The impact of ex vivo clinical grade activation protocols on human T-cell phenotype and function for the generation of genetically modified cells for adoptive cell transfer therapy

Optimized conditions for the ex vivo activation, genetic manipulation, and expansion of human lymphocytes for adoptive cell therapy may lead to protocols that maximize their in vivo function. We analyzed the effects of 4 clinical grade activation and expansion protocols over 3 weeks on cell proliferative rate, immunophenotype, cell metabolism, and transduction efficiency of human peripheral blood mononuclear cells (PBMCs). Peak lentiviral transduction efficiency was early (days 2 to 4), at a time when cells showed a larger size, maximal uptake of metabolic substrates, and the highest level of proximal T-cell receptor signaling engagement. Anti-CD2/3/28 activation beads induced greater proliferation rate and skewed PBMCs early on to a CD4 phenotype when compared with the cells cultured in OKT3. Multicolor surface phenotyping demonstrated that changes in T-cell surface markers that define T-cell functional phenotypes were dependent on the time spent in culture as opposed to the particular activation protocol. In conclusion, ex vivo activation of human PBMCs for adoptive cell therapy demonstrate defined immunophenotypic and functional signatures over time, with cells early on showing larger sizes, higher transduction efficiency, maximal metabolic activity, and zeta-chain-associated protein-70 activation.

CTLA4 blockade induces frequent tumor infiltration by activated lymphocytes regardless of clinical responses in humans

BACKGROUND

CTLA4 blocking monoclonal antibodies provide durable clinical benefit in a subset of patients with advanced melanoma mediated by intratumoral lymphocytic infiltrates. A key question is defining whether the intratumoral infiltration (ITI) is a differentiating factor between patients with and without tumor responses.

METHODS

Paired baseline and postdosing tumor biopsy specimens were prospectively collected from 19 patients with metastatic melanoma, including 3 patients with an objective tumor response, receiving the anti-CTLA4 antibody tremelimumab within a clinical trial with primary endpoint of quantitating CD8(+) cytotoxic T-lymphocyte (CTL) infiltration in tumors. Samples were analyzed for cell density by automated imaging capture and further characterized for functional lymphocyte properties by assessing the cell activation markers HLA-DR and CD45RO, the cell proliferation marker Ki67, and the regulatory T-cell marker FOXP3.

RESULTS

There was a highly significant increase in ITI by CD8(+) cells in biopsy samples taken after tremelimumab treatment. This included increases between 1-fold and 100-fold changes in 14 of 18 evaluable cases regardless of clinical tumor response or progression. There was no difference between the absolute number, location, or cell density of infiltrating cells between clinical responders and patients with nonresponding lesions that showed acquired intratumoral infiltrates. There were similar levels of expression of T-cell activation markers (CD45RO, HLA-DR) in both groups and no difference in markers for cell replication (Ki67) or the suppressor cell marker FOXP3.

CONCLUSION

CTLA4 blockade induces frequent increases in ITI by T cells despite which only a minority of patients have objective tumor responses.

Current experience with CTLA4-blocking monoclonal antibodies for the treatment of solid tumors

Monoclonal antibodies (mAbs) specific for cytotoxic T lymphocyte-associated antigen 4 (CTLA4) are a novel form of immunotherapy for treatment of patients with advanced cancers. These anti-CTLA4 mAbs prevent normal downregulation of the immune system, thus prolonging and enhancing T-cell activation and potentially promoting an antitumor immune response. Clinical studies in patients with advanced cancers have indicated that CTLA4 blockade with mAbs is associated with antitumor activity in a small percentage of patients and has a manageable toxicity profile. The key limitations for broader applicability of this mode of therapy are better definition of the mechanism that leads to tumor rejection and the validation of favorable observations in single-arm studies into prospectively randomized clinical trials.

Clinical development of the anti-CTLA-4 antibody tremelimumab

Tremelimumab (formerly CP-675,206) is a fully human IgG2 monoclonal antibody tested in patients with cancer, of whom the majority have had metastatic melanoma. Clinical trials using tremelimumab demonstrate that this antibody can induce durable tumor regressions (up to 8 years at this time) in 7% to 10% of patients with metastatic melanoma. These tumor responses are mediated by the intratumoral infiltration of cytotoxic T lymphocytes (CTLs) as demonstrated in patient-derived tumor biopsies. Grade 3 or 4 toxicities in the range of 20% to 25% are mainly inflammatory or autoimmune in nature, which are on-target effects after inhibiting CTLA-4-mediated self-tolerance. The lack of survival advantage in the early analysis of a phase III clinical trial comparing tremelimumab with standard chemotherapy for metastatic melanoma highlights the importance of gaining a better understanding of how this antibody modulates the human immune system and how to better select patients for this mode of therapy.

Anti-CTLA-4 antibody therapy: immune monitoring during clinical development of a novel immunotherapy

Cytotoxic T-lymphocyte-associated antigen (CTLA-4), also known as CD152, is a co-inhibitory molecule that functions to regulate T-cell activation. Antibodies that block the interaction of CTLA-4 with its ligands B7.1 and B7.2 can enhance immune responses, including antitumor immunity. Two CTLA-4-blocking antibodies are presently under clinical investigation: ipilimumab and tremelimumab. CTLA-4 blockade has shown promise in treatment of patients with metastatic melanoma, with a recently completed randomized, double-blind phase III trial demonstrating a benefit in overall survival (OS) in the treated population. However, this approach appears to benefit only a subset of patients. Understanding the mechanism(s) of action of CTLA-4 blockade and identifying prognostic immunologic correlates of clinical endpoints to monitor are presently areas of intense investigation. Several immunologic endpoints have been proposed to correlate with clinical activity. This review will focus on the endpoints of immune monitoring described in studies to date and discuss future areas of additional work needed.

Modulation of cell signaling networks after CTLA4 blockade in patients with metastatic melanoma

Background

The effects on cell signalling networks upon blockade of cytotoxic T lymphocyte-associated antigen-4 (CTLA4) using the monoclonal antibody tremelimumab were studied in peripheral blood mononuclear cell (PBMC) samples from patients with metastatic melanoma.

Methodology/Principal

Findings Intracellular flow cytometry was used to detect phosphorylated (p) signaling molecules downstream of the T cell receptor (TCR) and cytokine receptors. PBMC from tremelimumab-treated patients were characterized by increase in pp38, pSTAT1 and pSTAT3, and decrease in pLck, pERK1/2 and pSTAT5 levels. These changes were noted in CD4 and CD8 T lymphocytes but also in CD14 monocytes. A divergent pattern of phosphorylation of Zap70, LAT, Akt and STAT6 was noted in patients with or without an objective tumor response.

Conclusions/Significance

The administration of the CTLA4-blocking antibody tremelimumab to patients with metastatic melanoma influences signaling networks downstream of the TCR and cytokine receptors both in T cells and monocytes. The strong modulation of signaling networks in monocytes suggests that this cell subset may be involved in clinical responses to CTLA4 blockade.

Clinical Trial Registration

clinicaltrials.gov; Registration numbers NCT00090896 and NCT00471887

[What is new in oncodermatology?]

News in the oncodermatology field this year were dominated by publications treating of melanoma and concerning in particular our increased knowledge of the various biological pathways involved in the distinct subtypes of melanoma. This molecular diversity is probably one of the reasons explaining the poor results of most of the clinical trials recently published because we don't know yet how to identify and select the right population of patients who could beneficiate from such or such therapy. However, some very encouraging results obtained with new protocols for adoptive immunotherapy have been published and we also hope that further results will confirm that the subset of KIT-mutated melanomas will beneficiate from an efficient targeted anti-Kit therapy. Besides melanoma, the scoop of the year was the discovery of a defective oncogenic polyomavirus which is very likely to be responsible for Merkel cell carcinoma.

Kinetic phases of distribution and tumor targeting by T cell receptor engineered lymphocytes inducing robust antitumor responses

A key issue in advancing the use of adoptive cell transfer (ACT) of T cell receptor (TCR) engineered lymphocytes for cancer therapy is demonstrating how TCR transgenic cells repopulate lymphopenic hosts and target tumors in an antigen-specific fashion. ACT of splenocytes from fully immunocompetent HLA-A2.1/K(b) mice transduced with a chimeric murine/human TCR specific for tyrosinase, together with lymphodepletion conditioning, dendritic cell (DC)-based vaccination, and high-dose interleukin-2 (IL-2), had profound antitumor activity against large established MHC- and antigen-matched tumors. Genetic labeling with bioluminescence imaging (BLI) and positron emitting tomography (PET) reporter genes allowed visualization of the distribution and antigen-specific tumor homing of TCR transgenic T cells, with trafficking correlated with antitumor efficacy. After an initial brief stage of systemic distribution, TCR-redirected and genetically labeled T cells demonstrated an early pattern of specific distribution to antigen-matched tumors and locoregional lymph nodes, followed by a more promiscuous distribution 1 wk later with additional accumulation in antigen-mismatched tumors. This approach of TCR engineering and molecular imaging reporter gene labeling is directly translatable to humans and provides useful information on how to clinically develop this mode of therapy.

Immunotherapy for melanoma: current status and perspectives

Immunotherapy is an important modality in the therapy of patients with malignant melanoma. As our knowledge about this disease continues to expand, so does the immunotherapeutic armamentarium. Nevertheless, successful preclinical models do not always translate into clinically meaningful results. The authors give a comprehensive analysis of most recent advances in the immune anti-melanoma therapy, including interleukins, interferons, other cytokines, adoptive immunotherapy, biochemotherapy, as well as the use of different vaccines. We also present the fundamental concepts behind various immune enhancement strategies, passive immunotherapy, as well as the use of immune adjuvants. This review brings into discussion the results of newer and older clinical trials, as well as potential limitations and drawbacks seen with the utilization of various immune therapies in malignant melanoma. Development of novel therapeutic approaches, along with optimization of existing therapies, continues to hold a great promise in the field of melanoma therapy research. Use of anti-CTLA4 and anti-PD1 antibodies, realization of the importance of co-stimulatory signals, which translated into the use of agonist CD40 monoclonal antibodies, as well as activation of innate immunity through enhanced expression of co-stimulatory molecules on the surface of dendritic cells by TLR agonists are only a few items on the list of recent advances in the treatment of melanoma. The need to engineer better immune interactions and to boost positive feedback loops appear crucial for the future of melanoma therapy, which ultimately resides in our understanding of the complexity of immune responses in this disease.

CTLA-4 blockade: therapeutic potential in cancer treatments

Enhancing or prolonging T-cell activation by monoclonal antibodies (mAbs) blocking negative signaling receptors such as CTLA4 is one approach to overcoming tumor-induced immune tolerance. Ipilimumab and tremelimumab inhibit CTLA4, prolonging antitumor immune responses and leading to durable anti-tumor effects. Treatment with these mAbs has demonstrated clinically important and durable tumor responses and disease control rates in patients with unresectable advanced melanoma. Durable objective responses have been reported across a spectrum of doses and schedules, with relative safety in this patient population. Although the phase III tremelimumab melanoma study was closed for "futility", the 1-year survival rate of >50% for tremelimumab and the median survival of 11.7 months (compared with 10.7 months for chemotherapy) are notable. Results of the phase III studies testing CTLA4-blockade with ipilimumab are eagerly anticipated. The further development of these agents includes testing in the neoadjuvant melanoma setting (ipilimumab) as well the adjuvant high-risk melanoma setting (ipilimumab). Future progress with CTLA-4 blockade therapy will also likely come from the use of combinations of agents that target several critical regulatory pathways of the immune system and modulate the immune response in the host in a synergistic and controlled fashion.