Advances in the development of cancer immunotherapies

Circulating T cells: a promising biomarker of anti-PD-(L)1 therapy

Anti-PD-(L)1 therapy has shown great efficacy in some patients with cancer. However, a significant proportion of patients with cancer do not respond to it. Another unmet clinical need for anti-PD-(L)1 therapy is the dynamic monitoring of treatment effects. Therefore, identifying biomarkers that can stratify potential responders before PD-(L)1 treatment and timely monitoring of the efficacy of PD-(L)1 treatment are crucial in the clinical setting. The identification of biomarkers by liquid biopsy has attracted considerable attention. Among the identified biomarkers, circulating T cells are one of the most promising because of their indispensable contribution to anti-PD-(L)1 therapy. The present review aimed to thoroughly explore the potential of circulating T cells as biomarkers of anti-PD-(L)1 therapy and its advantages and limitations.

Optimization of the Administration Strategy for the Armed Oncolytic Adenovirus ZD55-IL-24 in Both Immunocompromised and Immunocompetent Mouse Models

ZD55-IL-24 is an armed oncolytic adenovirus similar but superior to ONYX-015. Virotherapeutic strategies using ZD55-IL-24 have been demonstrated to be effective against several cancer types. However, it is unclear whether the traditional administration strategy is able to exert the maximal antitumor efficacy of ZD55-IL-24. In this study, we sought to optimize the administration strategy of ZD55-IL-24 in both A375-bearing immunocompromised mouse model and B16-bearing immunocompetent mouse model. Although the underlying antitumor mechanisms are quite different, the obtained results are similar in these two mouse tumor models. We find that the antitumor efficacy of ZD55-IL-24 increases as injection times increase in both of these two models. However, no obvious increase of efficacy is observed as the dose of each injection increases. Our further investigation reveals that the administration strategy of sustained ZD55-IL-24 therapy can achieve a better therapeutic effect than the traditional administration strategy of short-term ZD55-IL-24 therapy. Furthermore, there is no need to inject every day; every 2 or 3 days of injection achieves an equivalent therapeutic efficacy. Finally, we find that the sustained rather than the traditional short-term ZD55-IL-24 therapy can synergize with anti-PD-1 therapy to reject tumors in B16-bearing immunocompetent mouse model. These findings suggest that the past administration strategy of ZD55-IL-24 is in fact suboptimal and the antitumor efficacy can be further enhanced through administration strategy optimization. This study might shed some light on the development of clinically applicable administration regimens for ZD55-IL-24 therapy.

A Phase 1 Study of KHK4083: A Single-Blind, Randomized, Placebo-Controlled Single-Ascending-Dose Study in Healthy Adults and an Open-Label Multiple-Dose Study in Patients With Ulcerative Colitis

OX40 plays an essential role in maintaining late T‐cell proliferation and survival by suppressing apoptosis and by inducing T‐cell memory formation. Here, we report the results of the phase 1 study of KHK4083, a fully human antimonoclonal antibody specific for OX40. In this study, we aimed to assess the safety and tolerability of a single intravenous or subcutaneous administration of KHK4083 compared with placebo in healthy Japanese and Caucasian subjects and determined the pharmacokinetics (PK) and immunogenicity. Also, we assessed the preliminary efficacy and pharmacodynamics of multiple intravenous doses in Japanese patients with moderate to severe ulcerative colitis (UC). Drug‐related treatment emergent adverse events occurred in 21 healthy subjects (58.3%) and 5 patients with UC (62.5%) after administration of KHK4083. There were no serious adverse events. The PK profile of a single intravenous dose of 10 mg/kg KHK4083 was similar in healthy Japanese and Caucasian subjects. Of 8 UC patients, a clinical response was observed in 3 patients (37.5%) and clinical remission in 2 patients (25.0%) in week 6. Our study demonstrated the safety and tolerability of single and multiple administrations of KHK4083 in healthy Japanese and Caucasian subjects and Japanese patients with moderate to severe UC. It also indicated favorable pharmacological properties of the drug.

Tumor Cell-Derived TGFβ1 Attenuates Antitumor Immune Activity of T Cells via Regulation of PD-1 mRNA

Dysfunction in T-cell antitumor activity contributes to the tumorigenesis, progression, and poor outcome of clear cell renal cell carcinoma (ccRCC), with this dysfunction resulting from high expression of programmed cell death-1 (PD-1) in T cells. However, the molecular mechanisms maintaining high PD-1 expression in T cells have not been fully investigated in ccRCC. Here, we describe a mechanism underlying the regulation of PD-1 at the mRNA level and demonstrated its impact on T-cell dysfunction. Transcriptomic analysis identified a correlation between TGFβ1 and PD-1 mRNA levels in ccRCC samples. The mechanism underlying the regulation of PD-1 mRNA was then investigated in vitro and in vivo using syngeneic tumor models. We also observed that TGFβ1 had prognostic significance in patients with ccRCC, and its expression was associated with PD-1 mRNA expression. CcRCC-derived TGFβ1 activated P38 and induced the phosphorylation of Ser¹⁰ on H3, which recruited p65 to increase SRSF3 and SRSF5 expression in T cells. As a result, the half-life of PD-1 mRNA in T cells was prolonged. SRSF3 coordinated with NXF1 to induce PD-1 mRNA extranuclear transport in T cells. We then demonstrated that TGFβ1 could induce SRSF3 expression to restrict the antitumor activity of T cells, which influenced immunotherapy outcomes in ccRCC mouse models. Our findings highlight that tumor-derived TGFβ1 mediates immune evasion and has potential as a prognostic biomarker and therapeutic target in ccRCC.See related Spotlight on p. 1464.

Safety, Tolerability, and Potential Clinical Activity of a Glucocorticoid-Induced TNF Receptor-Related Protein Agonist Alone or in Combination With Nivolumab for Patients With Advanced Solid Tumors: A Phase 1/2a Dose-Escalation and Cohort-Expansion Clinical Trial

Importance

Multiple immunostimulatory agonist antibodies have been clinically tested in solid tumors to evaluate the role of targeting glucocorticoid-induced tumor necrosis factor (TNF) receptor-related protein in anticancer treatments.

Objective

To evaluate the safety and activity of the fully human glucocorticoid-induced TNF receptor-related protein agonist IgG1 monoclonal antibody BMS-986156 with or without nivolumab in patients with advanced solid tumors.

Design, Setting, and Participants

This global, open-label, phase 1/2a study of BMS-986156 with or without nivolumab enrolled 292 patients 18 years or older with advanced solid tumors and an Eastern Cooperative Oncology Group performance status of 1 or less. Prior checkpoint inhibitor therapy was allowed. Monotherapy and combination dose-escalation cohorts ran concurrently to guide expansion doses beginning October 16, 2015; the study is ongoing.

Interventions

The protein agonist BMS-986156 was administered intravenously at a dose of 10, 30, 100, 240, or 800 mg every 2 weeks as monotherapy, and in the combination group 30, 100, 240, or 800 mg plus 240 mg of nivolumab every 2 weeks; same-dose cohorts were pooled for analysis. One cohort also received 480 mg of BMS-986156 plus 480 mg of nivolumab every 4 weeks.

Main Outcomes and Measures

The primary end points were safety, tolerability, and dose-limiting toxic effects. Additional end points included antitumor activity per Response Evaluation Criteria in Solid Tumors, version 1.1, and exploratory biomarker analyses.

Results

With a follow-up range of 1.4 to 101.7 weeks (follow-up ongoing), 34 patients (16 women and 18 men; median age, 56.6 years [range, 28-75 years]) received monotherapy (4 patients completed initial treatment), and 258 patients (140 women and 118 men; median age, 60 years [range, 21-87 years]) received combination therapy (65 patients completed initial treatment). No grade 3 to 5 treatment-related adverse events occurred with BMS-986156 monotherapy; grade 3 to 4 treatment-related adverse events occurred in 24 patients (9.3%) receiving BMS-986156 plus nivolumab, with no grade 5 treatment-related adverse events. One dose-limiting toxic effect (grade 4 elevated creatine phosphokinase levels) occurred in a patient receiving 800 mg of BMS-986156 plus 240 mg of nivolumab every 2 weeks; BMS-986156 with or without nivolumab exhibited linear pharmacokinetics with dose-related increase after a single dose. Peripheral T-cell and natural killer-cell proliferation increased after administration of BMS-986156 with or without nivolumab. No consistent and significant modulation of intratumoral CD8+ T cells and FoxP3+ regulatory T cells was observed. No responses were seen with BMS-986156 alone; objective response rates ranged from 0% to 11.1% (1 of 9) across combination therapy cohorts, with a few responses observed in patients previously treated with anti-programmed death receptor (ligand) 1 therapy.

Conclusions and Relevance

Based on this cohort, BMS-986156 appears to have had a manageable safety profile, and BMS-986156 plus nivolumab demonstrated safety and efficacy comparable to historical data reported for nivolumab monotherapy.

Trial Registration

ClinicalTrials.gov identifier: NCT02598960.

Tailoring early-phase clinical trial design to address multiple research objectives

INTRODUCTION

In contemporary oncology drug development, implementation of novel early-phase designs with the ability to address multiple research objectives is needed to better refine regimens. This paper describes an adaptive design strategy for identifying a range of optimal regimens based on two endpoints within multiple cohorts. The proposed design was developed to address objectives in an early-phase trial of cancer vaccines in combination with agonistic antibodies to CD40 and CD27.

MATERIALS AND METHODS

We describe a model-based design strategy that was developed for a trial evaluating the safety and immunogenicity of vaccination with (1) peptides plus CD40 antibody and TLR3 ligand, (2) systemic administration of an agonistic CD27 antibody, and (3) to assess immune response from (1) and (2) compared to optimal controls in participants with stage IIB-IV melanoma.

RESULTS AND CONCLUSIONS

The proposed design is a practical adaptive method for use with combined immunotherapy regimens with multiple objectives within multiple cohorts of interest. Further advances in the effectiveness of cancer immunotherapies will require new approaches that include redefining optimal strategies to take multiple regimens forward into later phases, incorporating additional endpoints in the dose selection process and testing drug combination therapies to improve efficacy and reduce toxicity. Our goal is to facilitate the acceptance and application of more novel designs in contemporary early development trials.

Updates to the antitumor mechanism of oncolytic virus

Oncolytic viruses (OVs) are promising new therapeutic agents in the field of malignant tumor treatment. OVs can achieve the goal of targeted therapy by selectively killing tumor cells and inducing specific antitumor immunity. The key roles of OVs are tumor targeting and tumor killing mechanisms. Recently, molecular biotechnology has been used to optimize the transformation of wild virus strains in order to ensure a stronger oncolytic effect and lower adverse reactions, to enable testing in clinical trials as an antitumor drug. The main purpose of this review is to provide a description of oncolytic mechanisms, clinical studies, combination therapies, current challenges, and future prospects of OVs.

Activation of upper respiratory tract mucosal innate immune responses in cats by liposomal toll-like receptor ligand complexes delivered topically

BACKGROUND

Nonspecific induction of local innate immune responses by mucosally administered immunotherapy is a new approach to protection from upper respiratory tract infections. Therefore, a new liposome-toll-like receptor complex (LTC) immune stimulant was developed and investigated for its ability to activate innate immune responses in cats, both in vitro and in vivo, as part of an initial evaluation of LTC for use as an immunotherapeutic agent in cats.

OBJECTIVES

We hypothesized that LTC could activate innate immune responses in cats after topical application to nasal and oropharyngeal mucosal surfaces.

ANIMALS

Mucosal immune responses to topical administration of LTC were assessed in 7 healthy, purpose-bred cats, and in vitro responses were assessed using blood samples from healthy cats.

METHODS

Cytokine and cellular immune responses to LTC were evaluated in blood samples, nasal lavage specimens, and pharyngeal swabs from cats, using reverse transcriptase polymerase chain reaction assays, ELISA assays, and flow cytometry.

RESULTS

Liposome-TLR complexes rapidly activated leukocytes in vitro, including upregulation of costimulatory molecule expression and cytokine production. Topical administration of LTC in healthy cats triggered rapid recruitment of monocytes to the nasal and oropharyngeal mucosa.

CONCLUSIONS AND CLINICAL IMPORTANCE

Liposome-TLR complexes were found to effectively activate innate immune responses in cats after mucosal administration. These findings suggest that LTC have potential for use as a new mucosally administered immunotherapy for nonspecific protection from viral and bacterial respiratory tract infections.

Chemotherapy combined with dendritic cell vaccine and cytokine-induced killer cells in the treatment of colorectal carcinoma: a meta-analysis

Aim

To investigate the efficacy and safety of dendritic cell (DC) vaccine combined with cytokine-induced killer (CIK) cell therapy in colorectal carcinoma (CRC).

Patients and methods

PubMed, Embase, and Cochrane Library databases were searched systematically for clinical trials of DC vaccine and CIK cell therapy combined with chemotherapy for CRC. The primary and secondary endpoints were overall survival (OS) and disease-free survival (DFS), respectively. Pooled risk ratios were used to assess the treatment efficacy. Both random and fixed effects models were used for statistical analysis. The study population consisted of 871 CRC patients enrolled in four trials.

Results

OS and DFS were significantly improved in patients who received chemotherapy combined with DC vaccine and CIK cells, and no severe adverse events were shown.

Conclusions

The study demonstrated that the addition of DC vaccine and CIK cell therapy to chemotherapy is feasible and effective in patients with CRC.

Folate receptor 1 (FOLR1) targeted chimeric antigen receptor (CAR) T cells for the treatment of gastric cancer

Gastric cancer is a malignancy that has a high mortality rate. Although progress has been made in the treatment of gastric cancer, many patients experience cancer recurrence and metastasis. Folate receptor 1 (FOLR1) is overexpressed on the cell surface in over one-third of gastric cancer patients, but rarely is expressed in normal tissue. This makes FOLR1 a potential target for chimeric antigen receptor (CAR) T cell immunotherapy, although the function of FOLR1 has not been elucidated. CAR are engineered fusion receptor composed of an antigen recognition region and signaling domains. T cells expressing CAR have specific activation and cytotoxic effects against cancer cells containing the target antigen. In this study, we generated a CAR that targets FOLR1 composed of a single-chain variable fragment (scFv) of FOLR1 antibody and signaling domains consisting of CD28 and CD3ζ. Both FOLR1-CAR KHYG-1, a natural killer cell line, and FOLR1-CAR T cells recognized FOLR1-positive gastric cancer cells in a MHC-independent manner and induced secretion of various cytokines and caused cell death. Conclusively, this is the first study to demonstrate that CAR KHYG-1/T cells targeting FOLR1 are effective against FOLR1-positive gastric cancer cells.

Immunotherapy for pancreatic cancer: present and future

Despite the identification of some efficient drugs for the treatment of metastatic pancreatic cancer, this tumor remains one of the most lethal cancers and is characterized by a strong resistance to therapies. Pancreatic cancer has some unique features including the presence of a microenvironment filled with immunosuppressive mediators and a dense stroma, which is both a physical barrier to drug penetration and a dynamic entity involved in immune system control. Therefore, the immune system has been hypothesized to play an important role in pancreatic cancer. Thus, therapies acting on innate or adaptive immunity are being investigated. Here, we review the literature, report the most interesting results and hypothesize future treatment directions.

T Cell Exhaustion in Glioblastoma: Intricacies of Immune Checkpoints

Glioblastoma is an aggressive and incurable primary brain tumor. While the blockade of immune checkpoints leads to reversal of T cell exhaustion in many cancers, the efficacy of this therapy in glioblastoma requires further consideration of the brain microenvironment beyond T cell activity. Neural cells are crucially dependent on glucose for survival, and tumor cells rabidly consume glucose; the glucose-deprived microenvironment further elevates immune checkpoint molecules to benefit tumor growth and exacerbate T cell exhaustion. We review here how immune checkpoints drive exhaustion in T cells while favoring tumor metabolism, and discuss how glucose competition in the unique CNS milieu is an important consideration to improve the outcomes of immune checkpoint blockade in glioblastoma.

Current Status of Immunotherapy Treatments for Pancreatic Cancer

Pancreatic cancer (PC) is a lethal disease representing the seventh most frequent cause of death from cancer worldwide. Resistance of pancreatic tumors to current treatments leads to disappointing survival rates, and more specific and effective therapies are urgently needed. In recent years, immunotherapy has been proposed as a promising approach to the treatment of PC, and encouraging results have been published by various preclinical and clinical studies. This review provides an overview of the latest developments in the immunotherapeutic treatment of PC and summarizes the most recent and important clinical trials.

Novel algorithmic approach predicts tumor mutation load and correlates with immunotherapy clinical outcomes using a defined gene mutation set

BACKGROUND

While clinical outcomes following immunotherapy have shown an association with tumor mutation load using whole exome sequencing (WES), its clinical applicability is currently limited by cost and bioinformatics requirements.

METHODS

We developed a method to accurately derive the predicted total mutation load (PTML) within individual tumors from a small set of genes that can be used in clinical next generation sequencing (NGS) panels. PTML was derived from the actual total mutation load (ATML) of 575 distinct melanoma and lung cancer samples and validated using independent melanoma (n = 312) and lung cancer (n = 217) cohorts. The correlation of PTML status with clinical outcome, following distinct immunotherapies, was assessed using the Kaplan-Meier method.

RESULTS

PTML (derived from 170 genes) was highly correlated with ATML in cutaneous melanoma and lung adenocarcinoma validation cohorts (R2 = 0.73 and R2 = 0.82, respectively). PTML was strongly associated with clinical outcome to ipilimumab (anti-CTLA-4, three cohorts) and adoptive T-cell therapy (1 cohort) clinical outcome in melanoma. Clinical benefit from pembrolizumab (anti-PD-1) in lung cancer was also shown to significantly correlate with PTML status (log rank P value < 0.05 in all cohorts).

CONCLUSIONS

The approach of using small NGS gene panels, already applied to guide employment of targeted therapies, may have utility in the personalized use of immunotherapy in cancer.

Biodistribution and PET Imaging of Labeled Bispecific T Cell-Engaging Antibody Targeting EpCAM

AMG 110, a bispecific T cell engager (BiTE) antibody construct, induces T cell-mediated cancer cell death by cross-linking epithelial cell adhesion molecule (EpCAM) on tumor cells with a cluster of differentiation 3 ε (CD3ε) on T cells. We labeled AMG 110 with (89)Zr or near-infrared fluorescent dye (IRDye) 800CW to study its tumor targeting and tissue distribution.

METHODS

Biodistribution and tumor uptake of (89)Zr-AMG 110 was studied up to 6 d after intravenous administration to nude BALB/c mice bearing high EpCAM-expressing HT-29 colorectal cancer xenografts. Tumor uptake of (89)Zr-AMG 110 was compared with uptake in head and neck squamous cell cancer FaDu (intermediate EpCAM) and promyelocytic leukemia HL60 (EpCAM-negative) xenografts. Intratumoral distribution in HT-29 tumors was studied using 800CW-AMG 110.

RESULTS

Tumor uptake of (89)Zr-AMG 110 can be clearly visualized using small-animal PET imaging up to 72 h after injection. The highest tumor uptake of (89)Zr-AMG 110 at the 40-μg dose level was observed at 6 and 24 h (respectively, 5.35 ± 0.22 and 5.30 ± 0.20 percentage injected dose per gram; n = 3 and 4). Tumor uptake of (89)Zr-AMG 110 was EpCAM-specific and correlated with EpCAM expression. 800CW-AMG 110 accumulated at the tumor cell surface in viable EpCAM-expressing tumor tissue.

CONCLUSION

PET and fluorescent imaging provided real-time information about AMG 110 distribution and tumor uptake in vivo. Our data support using (89)Zr and IRDye 800CW to evaluate tumor and tissue uptake kinetics of bispecific T cell engager antibody constructs in preclinical and clinical settings.

Peptide-Based Cancer Vaccine Strategies and Clinical Results

Active cancer immunotherapy is an exciting and developing field in oncology research. Peptide vaccines, the use of isolated immunogenic tumor-associated antigen (TAA) epitopes to generate an anticancer immune response, are an attractive option as they are easily produced and administered with minimal toxicity. Multiple TAA-derived peptides have been identified and evaluated with various vaccine strategies currently in clinical testing. Research suggests that utilizing vaccines in patients with minimal-residual disease may be a more effective strategy compared to targeting patients with widely metastatic disease as it avoids the immune suppression and tolerance associated with higher volumes of more established disease. Clinical trials also suggest that vaccines may need to be tailored and administered to specific cancer subtypes to achieve maximum efficacy. Additionally, numerous immunomodulators now in research and development show potential synergy with peptide vaccines. Our group has focused on a simpler, single-peptide strategy largely from the HER2/neu protein. We will discuss our experience thus far as well as review other peptide vaccine strategies that have shown clinical efficacy.

A high-throughput RNAi screen for detection of immune-checkpoint molecules that mediate tumor resistance to cytotoxic T lymphocytes

The success of T cell-based cancer immunotherapy is limited by tumor's resistance against killing by cytotoxic T lymphocytes (CTLs). Tumor-immune resistance is mediated by cell surface ligands that engage immune-inhibitory receptors on T cells. These ligands represent potent targets for therapeutic inhibition. So far, only few immune-suppressive ligands have been identified. We here describe a rapid high-throughput siRNA-based screening approach that allows a comprehensive identification of ligands on human cancer cells that inhibit CTL-mediated tumor cell killing. We exemplarily demonstrate that CCR9, which is expressed in many cancers, exerts strong immune-regulatory effects on T cell responses in multiple tumors. Unlike PDL1, which inhibits TCR signaling, CCR9 regulates STAT signaling in T cells, resulting in reduced T-helper-1 cytokine secretion and reduced cytotoxic capacity. Moreover, inhibition of CCR9 expression on tumor cells facilitated immunotherapy of human tumors by tumor-specific T cells in vivo. Taken together, this method allows a rapid and comprehensive determination of immune-modulatory genes in human tumors which, as an entity, represent the ‘immune modulatome’ of cancer.

Cell Surface CD74-MIF Interactions Drive Melanoma Survival in Response to Interferon-γ

Melanoma is believed to be a highly immunogenic tumor and recent developments in immunotherapies are promising. IFN-γ produced by immune cells has a crucial role in tumor immune surveillance; however, it has also been reported to be pro-tumorigenic. In the current study, we found that IFN-γ enhances the expression of CD74, which interacts with its ligand, macrophage migration inhibitory factor (MIF), and thereby activates the PI3K/AKT pathway in melanoma, promoting tumor survival. IFN-γ increased phosphorylation of AKT Ser473 and upregulated total cell surface expression of CD74 in human melanoma cell lines tested. CD74 was highly expressed in melanoma tissues. Moreover, the expression of CD74 on tumor cells correlated with plasma IFN-γ levels in melanoma patient samples. In our analysis of melanoma cell lines, all produced MIF constitutively. Blockade of CD74-MIF interaction reduced AKT phosphorylation and expression of pro-tumorigenic molecules, including IL-6, IL-8, and BCL-2. Inhibition of CD74-MIF interaction significantly suppressed tumor growth in the presence of IFN-γ in our xenograft mouse model. Thus, we conclude that IFN-γ promotes melanoma cell survival by regulating CD74-MIF signaling, suggesting that targeting the CD74-MIF interaction under IFN-γ-stimulatory conditions would be an effective therapeutic approach for melanoma.

Rapana thomasiana hemocyanin modified with ionic liquids with enhanced anti breast cancer activity

This is the first study on the surface modification of a hemocyanin from marine snail Rapana thomasiana (RtH) with series of imidazolium-based amino acid ionic liquids [emim][AA]. We monitored the induced by [emim][AA] conformational changes in RtH molecule and evaluated the effect of these ionic liquids (ILs) on the protein thermal stability. The cytotoxicity of all obtained RtH-[emim][AA] complexes was assessed toward breast cancer cells (MCF-7) and murine fibroblasts (3T3). As a whole, even small amounts of the tested ILs altered the secondary structure of RtH. The thermal denaturation of RtH in presence of [emim][AA] displayed multi-component transitions, which were shifted toward lower temperatures in comparison to those estimated for the native RtH. The profiles of the RtH-IL calorimetric curves show a clear dependence on the structure of the added salts. In addition, all RtH-[emim][AA] complexes exhibited an enhanced antiprofilerative activity of toward MCF-7 cells in comparison to that of the native RtH. The best results are observed for RtH-[emim][Leu], RtH-[emim][Trp] or RtH-[emim][Ile], which applied in concentration of 700 μg/mL inhibited the MCF-7 cell viability (for 24h) by 66, 63 and 53%, respectively. In addition, these IL-RtH complexes were less cytotoxic to 3T3 cells, i.e. they exhibited some cell specificity.

Immune Checkpoint inhibitors: An introduction to the next-generation cancer immunotherapy

Activating the immune system to eliminate cancer cells and produce clinically relevant responses has been a long-standing goal of cancer research. Most promising therapeutic approaches to activating antitumor immunity include immune checkpoint inhibitors. Immune checkpoints are numerous inhibitory pathways hardwired in the immune system. They are critical for maintaining self-tolerance and modulating the duration and amplitude of physiological immune responses in peripheral tissues to minimize collateral tissue damage. Tumors regulate certain immune checkpoint pathways as a major mechanism of immune resistance. Because immune checkpoints are initiated by ligand-receptor interactions, blockade by antibodies provides a rational therapeutic approach. Although targeted therapies are clinically successful, they are often short-lived due to rapid development of resistance. Immunotherapies offer one notable advantage. Enhancing the cell-mediated immune response against tumor cells leads to generation of a long-term memory lymphocyte population patrolling the body to attack growth of any new tumor cells, thereby sustaining the therapeutic effects. Furthermore, early clinical results suggest that combination immunotherapies offer even more potent antitumor activity. This review is intended to provide an introduction to immune checkpoint inhibitors and discusses the scientific overview of cancer immunotherapy, mechanisms of the inhibitors, clinical pharmacology considerations, advances in combination therapies, and challenges in drug development.

The potential of radiotherapy to enhance the efficacy of renal cell carcinoma therapy

Renal cell carcinoma (RCC) is an immunogenic tumor, but uses several immune-suppressive mechanisms to shift the balance from tumor immune response toward tumor growth. Although RCC has traditionally been considered to be radiation resistant, recent evidence suggests that hypofractionated radiotherapy contributes to systemic antitumor immunity. Because the efficacy of antitumor immune responses depends on the complex balance between diverse immune cells and progressing tumor cells, radiotherapy alone is unlikely to induce persistent antitumor immunity. Therefore, the combination of radiotherapy with drugs having synergistic immunomodulatory properties holds great promise with the optimal timing and sequence of modalities depending on the agent used. We highlight the immunomodulatory properties of targeted therapies, such as tyrosine kinase inhibitors, mammalian target of rapamycin (mTOR) inhibitors and vascular endothelial growth factor (VEGF) neutralizing antibodies, and will suggest a combination schedule with radiotherapy based on the available literature. We also address the combination of radiotherapy with innovative treatments in the field of immunotherapy.

Phase I/II study of adjuvant immunotherapy with sentinel lymph node T lymphocytes in patients with colorectal cancer

Although the development of multi-disciplinary management has improved the survival of colorectal cancer (CRC), the prognosis of metastatic CRC patients remains poor. Accumulating evidence has demonstrated that immunotherapy with cancer vaccines and adoptive T cell transfusions may improve outcomes as an adjuvant to current standard CRC treatment. In this phase I/II study, 71 CRC patients who underwent radical surgery (stage I-III, n = 46) or palliative surgery (stage IV with non-resectable synchronous metastases, n = 25) were included. In the first part of this study, sentinel lymph nodes (SLNs) were intraoperatively identified in 55 patients (46 with stage I-III CRC and 9 with stage IV CRC). SLN-T lymphocytes were expanded ex vivo for a median of 28.5 days (range 23-33 days). Thereafter, a median of 153 × 10(6) cells (range 20.7-639.0 × 10(6)) were transfused. No treatment-related toxicity was observed. In the second part of this study, the stage IV patients were routinely followed. The 24-month survival rate of the SLN-T lymphocyte group was significantly higher than that of the control group: 55.6 versus 17.5% (p = 0.02). The median overall survival of the SLN-T lymphocyte and control groups was 28 and 14 months, respectively. Our study showed that adjuvant SLN-T lymphocyte immunotherapy is feasible and safe for postoperative CRC patients. Additionally, this therapy may improve the long-term survival of metastatic CRC. Further investigation of the clinical efficacy and anti-tumor immunity is warranted.

A Phase I/II adaptive design to determine the optimal treatment regimen from a set of combination immunotherapies in high-risk melanoma

In oncology, vaccine-based immunotherapy often investigates regimens that demonstrate minimal toxicity overall and higher doses may not correlate with greater immune response. Rather than determining the maximum tolerated dose, the goal of the study becomes locating the optimal biological dose, which is defined as a safe dose demonstrating the greatest immunogenicity, based on some predefined measure of immune response. Incorporation of adjuvants, new or optimized peptide vaccines, and combining vaccines with immune modulators may enhance immune response, with the aim of improving clinical response. Innovative dose escalation strategies are needed to establish the safety and immunogenicity of new immunologic combinations. We describe the implementation of an adaptive design for identifying the optimal treatment strategy in a multi-site, FDA-approved, phase I/II trial of a novel vaccination approach using long-peptides plus TLR agonists for resected stage IIB-IV melanoma. Operating characteristics of the design are demonstrated under various possible true scenarios via simulation studies. Overall performance indicates that the design is a practical Phase I/II adaptive method for use with combined immunotherapy agents. The simulation results demonstrate the method's ability to effectively recommend optimal regimens in a high percentage of trials with manageable sample sizes. The numerical results presented in this work include the type of simulation information that aid review boards in understanding design performance, such as average sample size and frequency of early trial termination, which we hope will augment early-phase trial design in cancer immunotherapy.

Characterization of bispecific T-cell Engager (BiTE) antibodies with a high-capacity T-cell dependent cellular cytotoxicity (TDCC) assay

The Bispecific T-cell Engager (BiTE) antibody modality is a clinically validated immunotherapeutic approach for targeting tumors. Using T-cell dependent cellular cytotoxicity (TDCC) assays, we measure the percentage of specific cytotoxicity induced when a BiTE molecule engages T-cells, redirects T-cell mediated cytolysis, and ultimately kills target cells. We establish a novel luminescence-based TDCC assay quantified by measuring cell viability via constitutive expression of luciferase. The luciferase-based TDCC assay performance is valid and comparable to an adenosine triphosphate (ATP)-based detection method. We demonstrate that the luciferase-based TDCC assay is an efficient homogeneous assay format that is amenable to both suspension and adherent target cells. The luciferase-based TDCC assay eliminates the need for plate-washing protocols, allowing for higher-throughput screening of BiTE antibodies and better data quality. Assay capacity is also improved by performing serial dilutions of BiTE antibodies in 384-well format with an automated liquid handler. We describe here a robust, homogeneous TDCC assay platform with capacity for in vitro assessment of BiTE antibody potency and efficacy using multiple tumor cell lines and T-cell donors.

Myeloid expression of adenosine A2A receptor suppresses T and NK cell responses in the solid tumor microenvironment

High concentrations of adenosine in tumor microenvironments inhibit antitumor cytotoxic lymphocyte responses. Although T cells express inhibitory adenosine A2A receptors (A2AR) that suppress their activation and inhibit immune killing of tumors, a role for myeloid cell A2ARs in suppressing the immune response to tumors has yet to be investigated. In this study, we show that the growth of transplanted syngeneic B16F10 melanoma or Lewis lung carcinoma cells is slowed in Adora2a(f/f)-LysMCre(+/-) mice, which selectively lack myeloid A2ARs. Reduced melanoma growth is associated with significant increases in MHCII and IL12 expression in tumor-associated macrophages and with >90% reductions in IL10 expression in tumor-associated macrophages, dendritic cells (DC), and Ly6C(+) or Ly6G(+) myeloid-derived suppressor cells (MDSC). Myeloid deletion of A2ARs significantly increases CD44 expression on tumor-associated T cells and natural killer (NK) cells. Depletion of CD8(+) T cells or NK cells in tumor-bearing mice indicates that both cell types initially contribute to slowing melanoma growth in mice lacking myeloid A2A receptors, but tumor suppression mediated by CD8(+) T cells is more persistent. Myeloid-selective A2AR deletion significantly reduces lung metastasis of melanomas that express luciferase (for in vivo tracking) and ovalbumin (as a model antigen). Reduced metastasis is associated with increased numbers and activation of NK cells and antigen-specific CD8(+) T cells in lung infiltrates. Overall, the findings indicate that myeloid cell A2ARs have direct myelosuppressive effects that indirectly contribute to the suppression of T cells and NK cells in primary and metastatic tumor microenvironments. The results indicate that tumor-associated myeloid cells, including macrophages, DCs, and MDSCs all express immunosuppressive A2ARs that are potential targets of adenosine receptor blockers to enhance immune killing of tumors.

Viruses for tumor therapy

Oncolytic virotherapy exploits live viruses with selective tropism for cancerous cells and tissues to treat cancer. As discussed here, the field has progressed considerably as a result of both the successes and failures of previous and on-going clinical trials for various cancers. These studies indicate that oncolytic viruses are remarkably safe and more efficacious when virus replication stimulates sustained antitumor immune responses. In the future, virotherapy should be combined with immunomodulatory reagents that target immune tolerance to established cancers.

Adenosine A2A receptors intrinsically regulate CD8+ T cells in the tumor microenvironment

Adenosine A(2A) receptor (A(2A)R) blockade enhances innate and adaptive immune responses. However, mouse genetic studies have shown that A(2A)R deletion does not inhibit the growth of all tumor types. In the current study, we showed that growth rates for ectopic melanoma and bladder tumors are increased in Adora2a(-/-) mice within 2 weeks of tumor inoculation. A(2A)R deletion in the host reduced numbers of CD8(+) T cells and effector-memory differentiation of all T cells. To examine intrinsic functions in T cells, we generated mice harboring a T-cell-specific deletion of A(2A)R. In this host strain, tumor-bearing mice displayed increased growth of ectopic melanomas, decreased numbers of tumor-associated T cells, reduced effector-memory differentiation, and reduced antiapoptotic IL7Rα (CD127) expression on antigen-experienced cells. Intratumoral pharmacologic blockade similarly reduced CD8(+) T-cell density within tumors in wild-type hosts. We found that A(2A)R-proficient CD8(+) T cells specific for melanoma cells displayed a relative survival advantage in tumors. Thus, abrogating A(2A)R signaling appeared to reduce IL7R expression, survival, and differentiation of T cells in the tumor microenvironment. One implication of these results is that the antitumor effects of A(2A)R blockade that can be mediated by activation of cytotoxic T cells may be overcome in some tumor microenvironments as a result of impaired T-cell maintenance and effector-memory differentiation. Thus, our findings imply that the efficacious application of A(2A)R inhibitors for cancer immunotherapy may require careful dose optimization to prevent activation-induced T-cell death in tumors.

Oncolytic Poxviruses

Current standard treatments of cancer can prolong survival of many cancer patients but usually do not effectively cure the disease. Oncolytic virotherapy is an emerging therapeutic for the treatment of cancer that exploits replication-competent viruses to selectively infect and destroy cancerous cells while sparing normal cells and tissues. Clinical and/or preclinical studies on oncolytic viruses have revealed that the candidate viruses being tested in trials are remarkably safe and offer potential for treating many classes of currently incurable cancers. Among these candidates are vaccinia and myxoma viruses, which belong to the family Poxviridae and possess promising oncolytic features. This article describes poxviruses that are being developed for oncolytic virotherapy and summarizes the outcomes of both clinical and preclinical studies. Additionally, studies demonstrating superior efficacy when poxvirus oncolytic virotherapy is combined with conventional therapies are described.

The vigor of defense against non-self: potential superiority of allorestricted T cells in immunotherapy of cancer?

Men and sharks are both jawed vertebrates at the top of the food chain. Sharks are the first extant to develop adaptive immunity preserved to man throughout jawed vertebrates. We hypothesize here, that T cell receptor/major histocompatibility complex (TCR/MHC) interactions developed as the defense mechanism of carnivors against takeover by their victims’ cells derived pathogens. Germline encoded TCR segments have been conserved in evolution, providing the MHC bias of TCR. Ancestor genes of MHC polymorphisms may have first developed as a mating preference system, that later in evolution provided host immune responses destroying infectious non-self, yet maintaining tolerance to self. Pathogens may thus have simultaneously selected for alloimmunity. Allorejection has been observed in sharks and men. Cannibalism is a common ecological interaction in the animal kingdom, especially prevalent in aquatic communities; it favors selection of intraspecies allo responses for defense of self integrity. Alloreactive T cells do not undergo negative selection of strong TCR/MHC interactions; thus, they react stronger than self-MHC recognizing T cells. High levels of genetic diversity at MHC genes play a critical role in protecting populations of vertebrate species from contagious cells displaying stemness and homing features, including cancer cells. Recognition of self-MHC fails especially in diseases, which predominantly arise with age and after the peak of reproduction, e.g., cancer. So far, the treatment of malignant disease with autologous T cells has widely failed. Allorecognition constitutes an extremely powerful mechanism in evolution, which may be employed in immunotherapy of cancer by MHC-disparate, e.g., haploidentical transplantation and consecutive treatment with T cells from the donor parents recognizing tumor selective peptides presented by the non-inherited haplotype on the tumor.

Cancer testis antigen and immunotherapy

The identification of cancer testis (CT) antigens has been an important advance in determining potential targets for cancer immunotherapy. Multiple previous studies have shown that CT antigen vaccines, using both peptides and dendritic cell vaccines, can elicit clinical and immunologic responses in several different tumors. This review details the expression of melanoma antigen family A, 1 (MAGE-A1), melanoma antigen family A, 3 (MAGE-A3), and New York esophageal squamous cell carcinoma-1 (NY-ESO-1) in various malignancies, and presents our current understanding of CT antigen based immunotherapy.