The antitumor immunity of ipilimumab: (T-cell) memories to last a lifetime?

Downregulation of Nitric Oxide Collaborated with Radiotherapy to Promote Anti-Tumor Immune Response via Inducing CD8+ T Cell Infiltration

The production of nitric oxide (NO) is a key feature of immunosuppressive myeloid cells, which impair T cell activation and proliferation via reversibly blocking interleukin-2 receptor signaling. NO is mainly produced from L-arginine by inducible NO synthase (iNOS). Moreover, L-arginine is an essential element for T cell proliferation and behaviors. Impaired T cell function further inhibits anti-tumor immunity and promotes tumor progression. Previous studies indicated that radiotherapy activated anti-tumor immune responses in multiple tumors. However, myeloid-derived cells in the tumor microenvironment may neutralize these responses. We hypothesized that iNOS, as an important regulator of the immunosuppressive effects in myeloid-derived cells, mediated radiation resistance of cancer cells. In this study, we used 1400W dihydrochloride, a potent small-molecule inhibitor of iNOS, to explore the regulatory roles of NO in anti-tumor immunity. Radiotherapy and iNOS inhibition by 1400W collaboratively suppressed tumor growth and increased survival time, as well as increased tumor-infiltrating CD8+ T cells and specific inflammatory cytokine levels, in both lung and breast cancer cells in vivo. Our results also suggested that myeloid cell-mediated inhibition of T cell proliferation was effectively counteracted by radiation and 1400W-mediated NO blockade in vitro. Thus, these results demonstrated that iNOS was an important regulator of radiotherapy-induced antitumor immune responses. The combination of radiotherapy with iNOS blockade might be an effective therapy to improve the response of tumors to clinical radiation.

Population Pharmacokinetics of Nivolumab in Combination With Ipilimumab in Patients With Advanced Malignancies

Nivolumab is a fully human monoclonal antibody that inhibits programmed cell death‐1 activation. To assess covariate effects on nivolumab clearance (CL), a population pharmacokinetics model was developed using data from 6,468 patients with colorectal cancer, hepatocellular carcinoma, melanoma, non‐small cell lung cancer, renal cell carcinoma, or small cell lung cancer who received nivolumab as monotherapy or in combination with ipilimumab or chemotherapy across 25 clinical studies. Nivolumab CL was similar across the tumor types examined; CL was higher for ipilimumab 1 mg/kg every 6 weeks (by 17%) and 3 mg/kg every 3 weeks (by 29%) vs. nivolumab monotherapy. Nivolumab CL over time was partially explained by time‐varying covariates. A greater decrease in nivolumab time‐varying CL was associated with increased albumin and body weight and a responder status. Our findings support the observed association between nivolumab CL and disease severity.

Recent Successes and Future Directions in Immunotherapy of Cutaneous Melanoma

The global health burden associated with melanoma continues to increase while treatment options for metastatic melanoma are limited. Nevertheless, in the past decade, the field of cancer immunotherapy has witnessed remarkable advances for the treatment of a number of malignancies including metastatic melanoma. Although the earliest observations of an immunological antitumor response were made nearly a century ago, it was only in the past 30 years, that immunotherapy emerged as a viable therapeutic option, in particular for cutaneous melanoma. As such, melanoma remains the focus of various preclinical and clinical studies to understand the immunobiology of cancer and to test various tumor immunotherapies. Here, we review key recent developments in the field of immune-mediated therapy of melanoma. Our primary focus is on therapies that have received regulatory approval. Thus, a brief overview of the pathophysiology of melanoma is provided. The purported functions of various tumor-infiltrating immune cell subsets are described, in particular the recently described roles of intratumoral dendritic cells. The section on immunotherapies focuses on strategies that have proved to be the most clinically successful such as immune checkpoint blockade. Prospects for novel therapeutics and the potential for combinatorial approaches are delineated. Finally, we briefly discuss nanotechnology-based platforms which can in theory, activate multiple arms of immune system to fight cancer. The promising advances in the field of immunotherapy signal the dawn of a new era in cancer treatment and warrant further investigation to understand the opportunities and barriers for future progress.

Toward Precision Radiotherapy for Use with Immune Checkpoint Blockers

The first evidence that radiotherapy enhances the efficacy of immune checkpoint blockers (ICB) was obtained a dozen years ago in a mouse model of metastatic carcinoma refractory to anti-CTLA-4 treatment. At the time, ICBs had just entered clinical testing, an endeavor that culminated in 2011 with the approval of the first anti-CTLA-4 antibody for use in metastatic melanoma patients (ipilimumab). Thereafter, some patients progressing on ipilimumab showed systemic responses only upon receiving radiation to one lesion, confirming clinically the proimmunogenic effects of radiation. Preclinical data demonstrate that multiple immunomodulators synergize with radiotherapy to cause the regression of irradiated tumors and, less often, nonirradiated metastases. However, the impact of dose and fractionation on the immunostimulatory potential of radiotherapy has not been thoroughly investigated. This issue is extremely relevant given the growing number of clinical trials testing the ability of radiotherapy to increase the efficacy of ICBs. Recent data demonstrate that the recruitment of dendritic cells to neoplastic lesions (and hence the priming of tumor-specific CD8⁺ T cells) is highly dependent on radiotherapy dose and fractionation through a mechanism that involves the accumulation of double-stranded DNA in the cytoplasm of cancer cells and consequent type I IFN release. The molecular links between the cellular response to radiotherapy and type I IFN secretion are just being uncovered. Here, we discuss the rationale for an optimized use of radiotherapy as well as candidate biomarkers that may predict clinical responses to radiotherapy combined with ICBs. Clin Cancer Res; 24(2); 259-65. ©2017 AACR.

Experimental animal modeling for immuno-oncology

Immuno-oncology (I/O) research has intensified significantly in recent years due to the breakthrough development and the regulatory approval of several immune checkpoint inhibitors, leading to the rapid expansion of the new discovery of novel I/O therapies, new checkpoint inhibitors and beyond. However, many I/O questions remain unanswered, including why only certain subsets of patients respond to these treatments, who the responders would be, and how to expand patient response (the conversion of non-responders or maximizing response in partial responders). All of these require relevant I/O experimental systems, particularly relevant preclinical animal models. Compared to other oncology drug discovery, e.g. cytotoxic and targeted drugs, a lack of relevant animal models is a major obstacle in I/O drug discovery, and an urgent and unmet need. Despite the obvious importance, and the fact that much I/O research has been performed using many different animal models, there are few comprehensive and introductory reviews on this topic. This article attempts to review the efforts in development of a variety of such models, as well as their applications and limitations for readers new to the field, particularly those in the pharmaceutical industry.

In situ vaccination by radiotherapy to improve responses to anti-CTLA-4 treatment

Targeting immune checkpoint receptors has emerged as an effective strategy to induce immune-mediated cancer regression in the subset of patients who have significant pre-existing anti-tumor immunity. For the remainder, effective anti tumor responses may require vaccination. Radiotherapy, traditionally used to achieve local tumor control, has acquired a new role, that of a partner for immunotherapy. Ionizing radiation has pro-inflammatory effects that facilitate tumor rejection. Radiation alters the tumor to enhance the concentration of effector T cells via induction of chemokines, cytokines and adhesion molecules. In parallel, radiation can induce an immunogenic death of cancer cells, promoting cross-presentation of tumor-derived antigens by dendritic cells to T cells. Newly generated anti-tumor immune responses have been demonstrated post-radiation in both murine models and occasional patients, supporting the hypothesis that the irradiated tumor can become an in situ vaccine. It is in this role, that radiation can be applied to induce anti-tumor T cells in lymphocyte-poor tumors, and possibly benefit patients who would otherwise fail to respond to immune checkpoint inhibitors. This review summarizes preclinical and clinical data demonstrating that radiation acts in concert with antibodies targeting the immune checkpoint cytotoxic T-lymphocyte antigen-4 (CTLA-4), to induce therapeutically effective anti-tumor T cell responses in tumors otherwise non responsive to anti-CTLA-4 therapy.

Predictors of clinical response to immunotherapy with or without radiotherapy

Success with recent immunotherapies has resulted in previously unattainable response rates, as well as durable responses in diseases with historically poor prognoses. The combination of radiation therapy and immunotherapy has been a recent area of active investigation, with exciting results in a subset of patients. However, patient characteristics predictive of probable benefit from therapy and clinically meaningful biomarkers indicative of the early development of an antitumor immune response have yet to be identified. What is needed is a better way to predict which patients are likely to benefit from therapy, which would allow those patients unlikely to benefit from immunotherapy to be spared potentially futile therapies, thereby avoiding unnecessary risks of toxicity and costly treatment. Here, we summarize the early data on predictors of clinical response to immunotherapy, and to immunotherapy in combination with radiation.

Combination of radiotherapy and immune checkpoint inhibitors

The ability of ionizing radiation to cause cell death and inflammatory reactions has been known since the beginning of its therapeutic use in oncology. However, only recently this property of radiation has attracted the attention of immunologists seeking to induce or improve antitumor immunity. As immune checkpoint inhibitors are becoming mainstream cancer treatments, radiation oncologists have begun to observe unexpected out-of-the-field (abscopal) responses in patients receiving radiation therapy during immunotherapy. These unexpected responses were predicted by experimental work in preclinical tumor models and have clear biological bases. Accumulating experimental evidence that radiation induces an immunogenic cell death and promotes recruitment and function of T cells within the tumor microenvironment supports the hypothesis that radiation can convert the tumor into an in situ individualized vaccine. This property of radiation is key to its synergy with immune checkpoint inhibitors, antibodies targeting inhibitory receptors on T cells such as cytotoxic T lymphocyte antigen-4 and programmed death-1. By removing the obstacles hindering the activation and function of antitumor T cells, these agents benefit patients with pre-existing antitumor immunity but are ineffective in patients lacking these spontaneous responses. Radiation induces antitumor T cells complementing the activity of immune checkpoint inhibitors.

TGFβ Is a Master Regulator of Radiation Therapy-Induced Antitumor Immunity

T cells directed to endogenous tumor antigens are powerful mediators of tumor regression. Recent immunotherapy advances have identified effective interventions to unleash tumor-specific T-cell activity in patients who naturally develop them. Eliciting T-cell responses to a patient's individual tumor remains a major challenge. Radiation therapy can induce immune responses to model antigens expressed by tumors, but it remains unclear whether it can effectively prime T cells specific for endogenous antigens expressed by poorly immunogenic tumors. We hypothesized that TGFβ activity is a major obstacle hindering the ability of radiation to generate an in situ tumor vaccine. Here, we show that antibody-mediated TGFβ neutralization during radiation therapy effectively generates CD8(+) T-cell responses to multiple endogenous tumor antigens in poorly immunogenic mouse carcinomas. Generated T cells were effective at causing regression of irradiated tumors and nonirradiated lung metastases or synchronous tumors (abscopal effect). Gene signatures associated with IFNγ and immune-mediated rejection were detected in tumors treated with radiation therapy and TGFβ blockade in combination but not as single agents. Upregulation of programmed death (PD) ligand-1 and -2 in neoplastic and myeloid cells and PD-1 on intratumoral T cells limited tumor rejection, resulting in rapid recurrence. Addition of anti-PD-1 antibodies extended survival achieved with radiation and TGFβ blockade. Thus, TGFβ is a fundamental regulator of radiation therapy's ability to generate an in situ tumor vaccine. The combination of local radiation therapy with TGFβ neutralization offers a novel individualized strategy for vaccinating patients against their tumors.

The optimal partnership of radiation and immunotherapy: from preclinical studies to clinical translation

The main role of the immune system is to restore tissue homeostasis when altered by pathogenic processes, including neoplastic transformation. Immune-mediated tumor rejection has been recognized as an extrinsic tumor suppressor mechanism that tumors need to overcome to progress. By the time a tumor becomes clinically apparent it has successfully escaped immune control by establishing an immunosuppressive microenvironment. Ionizing radiation applied locally to a tumor alters these tumor-host interactions. Accumulating evidence indicates that standard therapeutic doses of radiation have the potential to recover tumor immunogenicity and convert the tumor into an in situ personalized vaccine. Radiotherapy induces an immunogenic tumor cell death promoting cross-presentation of tumor-derived antigens by dendritic cells to T cells. In addition, radiotherapy stimulates chemokine-mediated recruitment of effector T cells to the tumor, and cellular recognition and killing by T cells that is facilitated by upregulation of major histocompatibility antigens, NKG2D ligands, adhesion molecules and death receptors. Despite these effects, radiotherapy alone is only rarely capable of generating enough proinflammatory signals to sufficiently overcome suppression, as it can also activate immunosuppressive factors. However, our group and others have shown that when combined with targeted immunotherapy agents radiotherapy significantly contributes to a therapeutically effective anti-tumor immune response. To illustrate this partnership between radiation and immunotherapy we will discuss as an example our experience in preclinical models and the molecular mechanisms identified. Additionally, the clinical translation of these combinations will be discussed.

Antibody therapies for melanoma: new and emerging opportunities to activate immunity (Review)

The interface between malignant melanoma and patient immunity has long been recognised and efforts to treat this most lethal form of skin cancer by activating immune responses with cytokine, vaccine and also antibody immunotherapies have demonstrated promise in limited subsets of patients. In the present study, we discuss different antibody immunotherapy approaches evaluated in the context of melanoma, each designed to act on distinct targets and to employ different mechanisms to restrict tumour growth and spread. Monoclonal antibodies recognising melanoma-associated antigens such as CSPG4/MCSP and targeting elements of tumour-associated vasculature (VEGF) have constituted long-standing translational approaches aimed at reducing melanoma growth and metastasis. Recent insights into mechanisms of immune regulation and tumour-immune cell interactions have helped to identify checkpoint molecules on immune (CTLA4, PD-1) and tumour (PD-L1) cells as promising therapeutic targets. Checkpoint blockade with antibodies to activate immune responses and perhaps to counteract melanoma-associated immunomodulatory mechanisms led to the first clinical breakthrough in the form of an anti-CTLA4 monoclonal antibody. Novel modalities to target key mechanisms of immune suppression and to redirect potent effector cell subsets against tumours are expected to improve clinical outcomes and to provide previously unexplored avenues for therapeutic interventions.

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.

Immunotherapy in Melanoma: Recent Advances and Promising New Therapies

The incidence and mortality of melanoma are on the rise. Historically, patients diagnosed with metastatic melanoma were faced with a grim prognosis, with survival rates of 15% at 5 years. Prior to 2011, no drug or therapeutic regimen had been shown to improve overall survival (OS) in metastatic melanoma. Chemotherapeutic agents, such as dacarbazine or temozolomide, are often given to patients for palliative purposes; high-dose interleukin 2 and biochemotherapy are immunotherapeutic options that could be offered to patients with a good performance status at specialized centers. Neither has been shown to impact OS, but durable complete responses are seen in a minority of patients. Since 2011, 4 new drugs have been approved by the US Food and Drug Administration for the treatment of metastatic melanoma, all of which improve survival. Three of these agents (vemurafenib, dabrafenib, and trametinib) are targeted therapies, with ipilimumab being the only new immunotherapy. With a focus on immunotherapeutic agents, this review seeks to summarize the treatment options currently available for metastatic melanoma and to examine those on the near horizon.

Checkpoint modulation in melanoma: an update on ipilimumab and future directions

Ipilimumab, an anti-cytotoxic T-lymphocyte antigen 4 antibody, was the first therapy demonstrated to improve overall survival in melanoma. Since ipilimumab's approval by the FDA in 2011, a wealth of data has amassed, helping clinicians to optimize its use. We have learned how to mitigate the adverse effects of ipilimumab, identified its effects in melanoma subpopulations such as those with brain metastases, uveal melanoma, and mucosal melanoma, discovered potential biomarkers of activity, and investigated its use in combination with other therapeutic modalities. These discoveries have paved the way for rapid development of second-generation immunomodulatory antibodies such as inhibitors of the programmed cell death 1 receptor axis. These new agents hold promise as monotherapy, but perhaps the greatest allure lies in the possibility of combining these agents in synergistic multidrug regimens.

Immunomodulatory therapy for melanoma: ipilimumab and beyond

In 2011, the U.S. Food and Drug Administration approved the first new therapy for melanoma in more than a decade, ipilimumab (Yervoy). Ipilimumab is a novel antibody that blocks cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), a regulatory molecule expressed on activated T cells. Blockade of this important immune checkpoint can lead to durable tumor regression, and phase III studies show an overall survival benefit for patients with advanced melanoma. During the clinical development of ipilimumab, several unique features of this immunotherapy were identified, including the remarkable durability of responses and a distinct side-effects profile. We review the preclinical and clinical development of CTLA-4-blocking antibodies and describe current practices using ipilimumab for the treatment of advanced melanoma. Unique clinical issues related to ipilimumab will be summarized. Lastly, we will briefly preview combination therapies that incorporate ipilimumab and new checkpoint-targeting antibodies currently in clinical development.

Immunomodulatory therapy for melanoma: ipilimumab and beyond

In 2011, the U.S. Food and Drug Administration approved the first new therapy for melanoma in more than a decade, ipilimumab (Yervoy). Ipilimumab is a novel antibody that blocks cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), a regulatory molecule expressed on activated T cells. Blockade of this important immune checkpoint can lead to durable tumor regression, and phase III studies show an overall survival benefit for patients with advanced melanoma. During the clinical development of ipilimumab, several unique features of this immunotherapy were identified, including the remarkable durability of responses and a distinct side-effects profile. We review the preclinical and clinical development of CTLA-4-blocking antibodies and describe current practices using ipilimumab for the treatment of advanced melanoma. Unique clinical issues related to ipilimumab will be summarized. Lastly, we will briefly preview combination therapies that incorporate ipilimumab and new checkpoint-targeting antibodies currently in clinical development.

At the bedside: CTLA-4- and PD-1-blocking antibodies in cancer immunotherapy

It is increasingly appreciated that cancers are recognized by the immune system, and under some circumstances, the immune system may control or even eliminate tumors. The modulation of signaling via coinhibitory or costimulatory receptors expressed on T cells has proven to be a potent way to amplify antitumor immune responses. This approach has been exploited successfully for the generation of a new class of anticancer therapies, "checkpoint-blocking" antibodies, exemplified by the recently FDA-approved agent, ipilimumab, an antibody that blocks the coinhibitory receptor CTLA-4. Capitalizing on the success of ipilimumab, agents that target a second coinhibitory receptor, PD-1, or its ligand, PD-L1, are in clinical development. Lessons learned from treating patients with CTLA-4 and PD-1 pathway-blocking antibodies will be reviewed, with a focus on concepts likely to inform the clinical development and application of agents in earlier stages of development. See related review At the bench: Preclinical rationale for CTLA-4 and PD-1 blockade as cancer immunotherapy.