Agonists of Co-stimulation in Cancer Immunotherapy Directed Against CD137, OX40, GITR, CD27, CD28, and ICOS

Combinatorial immunotherapeutic approaches to restore the function of anergic tumor-reactive cytotoxic CD8+ T cells

Numerous preclinical studies have demonstrated that combination immunotherapy can significantly reduce tumor growth and improve overall survival as compared to monotherapy. Furthermore, dual CTLA-4/PD-1 checkpoint blockade recently received FDA-approval for patients with metastatic melanoma, becoming the first combination immunotherapy to garner this designation in a rapidly evolving field. Despite this progress, the majority of patients do not respond to treatment, underscoring the critical need for more effective therapies. We have been investigating the mechanisms by which combination immunotherapy with an OX40 agonist plus CTLA-4 checkpoint blockade augments effector T cell responses to elicit anti-tumor immunity. Surprisingly, this approach failed to eradicate well-established tumors, in part due to the induction of anergy in cytotoxic CD8⁺ T cells. Further work revealed that anergic CD8⁺ T cells could be rescued by combining a dendritic cell-targeted vaccine with combination immunotherapy. Taken together, these data suggest that novel combinatorial immunotherapeutic strategies incorporating a vaccination strategy may be needed to generate effective anti-tumor responses in the majority of patients with metastatic disease.

Checkpoint inhibitors and other novel immunotherapies for advanced renal cell carcinoma

The management of advanced renal cell carcinoma (RCC) has dramatically changed over the past decade. Therapies that target the vascular endothelial growth factor (VEGF) and mammalian target of rapamycin (mTOR) pathways have considerably expanded treatment options; however, most patients with advanced RCC still have limited overall survival. Increased understanding of the mechanisms of T cell-antigen recognition and function has led to the development of novel immunotherapies to treat cancer, chief among them inhibitors of checkpoint receptors - molecules whose function is to restrain the host immune response. In 2015, the FDA approved the first checkpoint inhibitor nivolumab for patients with advanced RCC following treatment with antiangiogenic therapy based on improved overall survival compared with the standard of care. Ongoing phase III trials are comparing checkpoint-inhibitor-based combination regimens with antiangiogenesis agents in the first-line setting. The field is evolving rapidly, with many clinical trials already testing several checkpoint inhibitors alone, in combination, or with other targeted therapies. In addition, different novel immune therapies are being investigated including vaccines, T-cell agonists, and chimeric antigen receptor T cells. Determining which patients will benefit from these therapies and which combination approaches will result in better response will be important as this field evolves.

Anti-CD137 enhances anti-CD20 therapy of systemic B-cell lymphoma with altered immune homeostasis but negligible toxicity

Studies of sequential anti-CD137/anti-CD20 therapy have previously shown that the efficacy of anti-CD20 was heavily reliant upon anti-CD137; however, the exact mechanism of the anti-B-cell lymphoma efficacy, and whether this correlates with enhanced adverse effects or toxicity, had not been elucidated. Here, we observed that sequential anti-CD137 administration with anti-CD20 resulted in a synergistic therapy, largely dependent upon Fc receptors (FcR), to prolong survival in an experimental B-cell lymphoma therapy model. Tumor suppression was accompanied by B cell depletion, which was not dependent on one activating FcR. Surprisingly, the B-cell activating factor (BAFF) was elevated in the plasma of mice receiving anti-CD137 alone or in combination with anti-CD20, while a selective increase in some plasma cytokines was also noted and triggered by anti-CD137. These effects were independent of activating FcR. Sustained treatment of advanced lymphoma revealed increased lymphocyte infiltrates into the liver and a significant decrease in the metabolic capability of the liver in mice receiving anti-CD137. Importantly, these effects were not exacerbated in mice receiving the anti-CD20/CD137 combination, and elevations in classical liver damage markers such as alanine aminotransferase (ALT) were less than that caused by the lymphoma itself. Thus, combined anti-CD20/anti-CD137 treatment increases the therapeutic index of anti-CD20 or anti-CD137 alone. These mouse data were corroborated by ongoing clinical development studies to assess safety, tolerability and pharmacodynamic activity of human patients treated by this approach. Together, these data support the use of this sequential antibody therapeutic strategy to improve the efficacy of rituximab in B-cell lymphoma patients.

Immuno-oncology combinations: raising the tail of the survival curve

There have been exponential gains in immuno-oncology in recent times through the development of immune checkpoint inhibitors. Already approved by the U.S. Food and Drug Administration for advanced melanoma and non-small cell lung cancer, immune checkpoint inhibitors also appear to have significant antitumor activity in multiple other tumor types. An exciting component of immunotherapy is the durability of antitumor responses observed, with some patients achieving disease control for many years. Nevertheless, not all patients benefit, and efforts should thus now focus on improving the efficacy of immunotherapy through the use of combination approaches and predictive biomarkers of response and resistance. There are multiple potential rational combinations using an immunotherapy backbone, including existing treatments such as radiotherapy, chemotherapy or molecularly targeted agents, as well as other immunotherapeutics. The aim of such antitumor strategies will be to raise the tail on the survival curve by increasing the number of long term survivors, while managing any additive or synergistic toxicities that may arise with immunotherapy combinations. Rational trial designs based on a clear understanding of tumor biology and drug pharmacology remain paramount. This article reviews the biology underpinning immuno-oncology, discusses existing and novel immunotherapeutic combinations currently in development, the challenges of predictive biomarkers of response and resistance and the impact of immuno-oncology on early phase clinical trial design.

Immunotherapy of Melanoma

Arising from melanocytes in skin, mucosal membranes, eye, and meninges, melanoma is a tumor that has been associated with poor prognosis in advanced disease stages. Given the poor response to chemotherapy and radiation therapy, new treatment approaches with targeted therapy, immunotherapy, and adoptive T-cell therapy have revolutionized the standard of care for patients with advanced melanoma. This review provides a short overview of past, present, and future immunotherapeutic approaches and their limitations, with a focus on new combination agents in early clinical trials.

Checkpoint Inhibitors and Their Application in Breast Cancer

Immune checkpoints are crucial for the maintenance of self-tolerance and for the modulation of immune responses in order to minimize tissue damage. Tumor cells take advantage of these mechanisms to evade immune recognition. A significant proportion of tumors, including breast cancers, can express co-inhibitory molecules that are important formediating the escape from T cell-mediated immune surveillance. The interaction of inhibitory receptors with their ligands can be blocked by specific molecules. Monoclonal antibodies (mAbs) directed against the cytotoxic T lymphocyte-associated antigen-4 (CTLA4) and, more recently, against the programmed cell death protein 1 (PD1), have been approved for the therapy of melanoma (anti-CTLA4 and anti-PD1 mAbs) and non-small cell lung cancer (anti-PD1 mAbs). Moreover, inhibition of PD1 signaling has shown extremely promising signs of activity in breast cancer. An increasing number of molecules directed against other immune checkpoints are currently under clinical development. In this review, we summarize the evidence supporting the implementation of checkpoint inhibition in breast cancer by reviewing in detail data on PD-L1 expression and its regulation. In addition, opportunities to boost anti-tumor immunity in breast cancer with checkpoint inhibitor-based immunotherapies alone and in combination with other treatment options will be discussed.

Tumor-targeted costimulation by using bi-specific aptamers

Aptamers are chemically synthesized oligonucleotides that can be easily engineered for cancer immunotherapy use. So far, most of the therapeutic aptamers described are antagonistic and block the function of a receptor or its soluble ligand. Recently, aptamers have been modified to act as agonists by multimerization, with a direct application in cancer immunotherapy. Several agonistic aptamers against costimulatory receptors have been described. However, systemic costimulation, though potentially a very potent antitumor immune strategy, is not devoid of auto-inflammatory side effects. In a quest to reduce toxicity and improve efficacy – reducing the therapeutic index – the first bi-specific aptamers to target the costimulatory ligand to the tumor have been described, showing very promising results in different preclinical tumor models.

High-content molecular profiling of T-cell therapy in oncology

Recent clinical data have revealed the remarkable potential for T-cell-modulating agents to induce potent and durable responses in a subset of cancer patients. In this review, we discuss molecular approaches, platforms, and strategies that enable a broader interrogation of the activity of agents that modulate the activity of tumor-specific T cells, to more comprehensively understand how and why the agents succeed and fail, as well as examples of data sets generated in clinical trials that have provided important insights into the biological activity of T-cell therapies and that support further rational development of this exciting treatment modality.

The immune mechanisms of abscopal effect in radiation therapy

Radiation therapy (RT) is a cornerstone in oncologic management and is employed in various curative and palliative scenarios for local-regional control. RT is thought to locally control tumor cells by direct physical DNA damage or indirect insults from reactive oxygen species. Therapeutic effects apart from those observed at the treatment target, that is, abscopal effect, have been observed for several decades, though the underlying mechanisms regulating this phenomenon have been unclear. Accumulating evidence now suggests that the immune system is a major determinant in regulating the abscopal effect. It is now evident that RT may also enhance immunologic responses to tumors by creating an in situ vaccine by eliciting antigen release from dying tumor cells. Harnessing the specificity and dynamic nature of the immune system to target tumors in conjunction with RT is an emerging field with much promise. To optimize this approach, it is important to systematically evaluate the intricacies of the host immune system, the new generation of immunotherapeutics and the RT approach. Here we will discuss the current biologic mechanisms thought to regulate the RT-induced abscopal effect and how these may be translated to the clinical setting.