Fc-mOX40L fusion protein produces complete remission and enhanced survival in 2 murine tumor models

OX40/OX40 ligand and its role in precision immune oncology

Immune checkpoint inhibitors have changed the treatment landscape for various malignancies; however, their benefit is limited to a subset of patients. The immune machinery includes both mediators of suppression/immune evasion, such as PD-1, PD-L1, CTLA-4, and LAG-3, all of which can be inhibited by specific antibodies, and immune-stimulatory molecules, such as T-cell co-stimulatory receptors that belong to the tumor necrosis factor receptor superfamily (TNFRSF), including OX40 receptor (CD134; TNFRSF4), 4-1BB (CD137; TNFRSF9), and glucocorticoid-induced TNFR-related (GITR) protein (CD357; TNFRSF18). In particular, OX40 and its binding ligand OX40L (CD134L; TNFSF4; CD252) are critical for immunoregulation. When OX40 on activated T cells binds OX40L on antigen-presenting cells, T-cell activation and immune stimulation are initiated via enhanced T-cell survival, proliferation and cytotoxicity, memory T-cell formation, and abrogation of regulatory T cell (Treg) immunosuppressive functions. OX40 agonists are in clinical trials both as monotherapy and in combination with other immunotherapy agents, in particular specific checkpoint inhibitors, for cancer treatment. To date, however, only a minority of patients respond. Transcriptomic profiling reveals that OX40 and OX40L expression vary between and within tumor types, and that only ~ 17% of cancer patients have high OX40 and low OX40L, one of the expression patterns that might be theoretically amenable to OX40 agonist enhancement. Taken together, the data suggest that the OX40/OX40L machinery is a critical part of the immune stimulatory system and that understanding endogenous expression patterns of these molecules and co-existing checkpoints merits further investigation in the context of a precision immunotherapy strategy for cancer therapy.

Engineered immunomodulatory extracellular vesicles derived from epithelial cells acquire capacity for positive and negative T cell co-stimulation in cancer and autoimmunity

Extracellular vesicles (EVs) are generated by all cells and systemic administration of allogenic EVs derived from epithelial and mesenchymal cells have been shown to be safe, despite carrying an array of functional molecules, including thousands of proteins. To address whether epithelial cells derived EVs can be modified to acquire the capacity to induce immune response, we engineered 293T EVs to harbor the immunomodulatory CD80, OX40L and PD-L1 molecules. We demonstrated abundant levels of these proteins on the engineered cells and EVs. Functionally, the engineered EVs efficiently elicit positive and negative co-stimulation in human and murine T cells. In the setting of cancer and auto-immune hepatitis, the engineered EVs modulate T cell functions and alter disease progression. Moreover, OX40L EVs provide additional benefit to anti-CTLA-4 treatment in melanoma-bearing mice. Our work provides evidence that epithelial cell derived EVs can be engineered to induce immune responses with translational potential to modulate T cell functions in distinct pathological settings.

Restoration of Follicular T Regulatory/Helper Cell Balance by OX40L-JAG1 Cotreatment Suppresses Lupus Nephritis in NZBWF1/j Mice

Class-switched antinuclear autoantibodies produced by T follicular helper (TFH) cell-dependent germinal center (GC) B cell response play an essential pathogenic role in lupus nephritis (LN). The role of T follicular regulatory (TFR) cells, an effector subset of CD4⁺Foxp3⁺ T regulatory cells (Tregs), which are specialized in suppressing TFH-GC response and Ab production, remains elusive in LN. Contrasting reports have shown increased/reduced circulating TFR cells in human lupus that might not accurately reflect their presence in the GCs of relevant lymphoid organs. In this study, we report a progressive reduction in TFR cells and decreased TFR/TFH ratio despite increased Tregs in the renal lymph nodes of NZBWF1/j mice, which correlated with increased GC-B cells and proteinuria onset. Cotreatment with soluble OX40L and Jagged-1 (JAG1) proteins increased Tregs, TFR cells, and TFR/TFH ratio, with a concomitant reduction in TFH cells, GC B cells, and anti-dsDNA IgG Ab levels, and suppressed LN onset. Mechanistic studies showed attenuated TFH functions and diminished GC events such as somatic hypermutation and isotype class-switching in OX40L-JAG1-treated mice. RNA sequencing studies revealed inhibition of hypoxia-inducible factor 1-α (HIF-1a) and STAT3 signaling in T conventional cells from OX40L-JAG1-treated mice, which are critical for the glycolytic flux and differentiation into TFH cell lineage. Therefore, the increased TFR/TFH ratio seen in OX40L-JAG1-treated mice could involve both impaired differentiation of TFH cells from T conventional cells and expansion of TFR cells. We show a key role for GC-TFR/TFH imbalance in LN pathogenesis and how restoring homeostatic balance can suppress LN.

Clinical Significance of OX40 and OX40 Ligand in the Peripheral Blood of Patients with Myasthenia Gravis

Background

A previous study on thymomas in myasthenia gravis (MG) patients indicated that OX40 expression may be upregulated in thymic tissues adjacent to germinal centers (GCs) and thymomas, and OX40 may interact with OX40L in GCs to enhance anti-acetylcholine receptor antibody production. However, little is known about the clinical significance of the expression of OX40 and OX40L in the peripheral blood of patients with MG. We aimed to characterize the expression of membrane-bound and soluble OX40 and OX40L in the peripheral blood of patients with MG and to identify their clinical significance.

Methods

For membrane molecules, we collected peripheral blood (PB) from 39 MG patients at baseline, 22 patients in relapse, and 42 patients in remission, as well as from 36 healthy participants as controls. For soluble molecules, plasma from 37 MG patients at baseline, 34 patients in relapse, and 30 patients in remission, as well as plasma from 36 healthy controls (HC), was retrospectively collected from the sample bank of the First Hospital of Soochow University. The expression of membrane-bound OX40 and OX40L (mOX40 and mOX40L) by immune cells was measured using flow cytometry. Plasma levels of soluble OX40 and OX40L (sOX40 and sOX40L) were measured by ELISA.

Results

(1) The expression of OX40 on CD4+ T cells and that of OX40L on B cells and monocytes were significantly increased, and the levels of sOX40 were significantly decreased in MG patients at baseline compared with HC, while the expression of sOX40L was not significantly different between the two groups. (2) Dynamic observation of the molecules showed significantly higher expression of OX40 on CD4⁺ T cells and higher levels of sOX40 in MG patients in relapse than in MG patients at baseline and MG patients in remission. Furthermore, the expression levels of sOX40 were significantly elevated in MG patients in remission compared with MG patients at baseline, and the expression of sOX40L was significantly lower in MG patients in remission than in MG patients at baseline and MG patients in relapse. (3) Plasma levels of sOX40 and sOX40L were significantly decreased in 13 patients with relapsed MG after immunosuppressive treatment compared with those before treatment. (4) Correlation analysis showed that the expression of OX40 on CD4⁺ T cells in patients with relapsed MG was positively correlated with the concentration of acetylcholine receptor antibodies (AchR-Ab), whereas the expression of OX40L on CD19⁺ B cells and CD14⁺ monocytes was negatively correlated with disease duration. (5) Binary regression analysis showed that patients with high CD4⁺ OX40 expression and high sOX40L levels had an increased risk of relapse.

Conclusions

OX40 and OX40L are abnormally expressed in the peripheral blood of patients with MG and may be closely associated with disease status and treatment. The OX40/OX40L pathway may be involved in the immunopathological process of MG and may play a role mainly in the later stage of MG.

Novel immune targets for the treatment of triple-negative breast cancer

INTRODUCTION

To overcome mechanisms of primary and secondary resistance to the anti-tumor immune response, novel targets such as ICOS, LAG3, and TIM3 are currently being explored at preclinical and early-phase clinical levels.

AREAS COVERED

This article examines the landscape of the immune therapeutics investigated in early-phase clinical trials for TNBC. Preclinical rationale is provided for each immune target, predominant expression, and function. Clinical implications and preliminary available trial results are discussed and finally, we reflect on aspects of future expectations and challenges in this field.

EXPERT OPINION

Several immune strategies have been investigated in TNBC, including co-inhibitory molecules beyond PD1-PD-L1 axis, co-stimulatory checkpoints, cancer vaccines, adoptive cell transfer, combination therapies, as well as different routes of administration. Most of approaches showed signs of anti-cancer activity and a good safety profile in early-phase clinical trials. Since IO provided benefit only to a small subgroup of TNBC patients so far, identifying predictive biomarkers is a priority to refine patient-selection. Data from ongoing clinical trials, with the gradually improving interpretation of the breast tumor immune environment, will hopefully refine the role of new immune targets for the treatment of TNBC.

Combined OX40 Agonist and PD-1 Inhibitor Immunotherapy Improves the Efficacy of Vascular Targeted Photodynamic Therapy in a Urothelial Tumor Model

PURPOSE

Vascular targeted photodynamic therapy (VTP) is a nonsurgical tumor ablation approach used to treat early-stage prostate cancer and may also be effective for upper tract urothelial cancer (UTUC) based on preclinical data. Toward increasing response rates to VTP, we evaluated its efficacy in combination with concurrent PD-1 inhibitor/OX40 agonist immunotherapy in a urothelial tumor-bearing model.

EXPERIMENTAL DESIGN

In mice allografted with MB-49 UTUC cells, we compared the effects of combined VTP with PD-1 inhibitor/OX40 agonist with those of the component treatments on tumor growth, survival, lung metastasis, and antitumor immune responses.

RESULTS

The combination of VTP with both PD-1 inhibitor and OX40 agonist inhibited tumor growth and prolonged survival to a greater degree than VTP with either immunotherapeutic individually. These effects result from increased tumor infiltration and intratumoral proliferation of cytotoxic and helper T cells, depletion of Treg cells, and suppression of myeloid-derived suppressor cells.

CONCLUSIONS

Our findings suggest that VTP synergizes with PD-1 blockade and OX40 agonist to promote strong antitumor immune responses, yielding therapeutic efficacy in an animal model of urothelial cancer.

Ligand-Blocking and Membrane-Proximal Domain Targeting Anti-OX40 Antibodies Mediate Potent T Cell-Stimulatory and Anti-Tumor Activity

Agonistic antibodies targeting the tumor necrosis factor (TNF) superfamily of co-stimulatory receptors (TNFRSF) are progressing through various stages of clinical development for cancer treatment, but the desired and defining features of these agents for optimal biological activity remain controversial. One idea, based on recent studies with CD40, is that non-ligand-blocking antibodies targeting membrane-distal cysteine-rich domain 1 (CRD1) have superior agonistic activities compared with ligand-blocking antibodies targeting more membrane-proximal CRDs. Here, we determined the binding and functional characteristics of a panel of antibodies targeting CRDs 1-4 of OX40 (also known as TNFRSF4 or CD134). In striking contrast to CD40, we found that ligand-blocking CRD2-binding and membrane-proximal CRD4-binding anti-OX40 antibodies have the strongest agonistic and anti-tumor activities. These findings have important translational implications and further highlight that the relationship between epitope specificity and agonistic activity will be an important issue to resolve on a case-by-case basis when optimizing antibodies targeting different co-stimulatory tumor necrosis factor receptors (TNFRs).

Therapeutic strategies for the costimulatory molecule OX40 in T-cell-mediated immunity

The T cell co-stimulatory molecule OX40 and its cognate ligand OX40L have attracted broad research interest as a therapeutic target in T cell-mediated diseases. Accumulating preclinical evidence highlights the therapeutic efficacy of both agonist and blockade of the OX40-OX40L interaction. Despite this progress, many questions about the immuno-modulator roles of OX40 on T cell function remain unanswered. In this review we summarize the impact of the OX40-OX40L interaction on T cell subsets, including Th1, Th2, Th9, Th17, Th22, Treg, Tfh, and CD8+ T cells, to gain a comprehensive understanding of anti-OX40 mAb-based therapies. The potential therapeutic application of the OX40-OX40L interaction in autoimmunity diseases and cancer immunotherapy are further discussed; OX40-OX40L blockade may ameliorate autoantigen-specific T cell responses and reduce immune activity in autoimmunity diseases. We also explore the rationale of targeting OX40-OX40L interactions in cancer immunotherapy. Ligation of OX40 with targeted agonist anti-OX40 mAbs conveys activating signals to T cells. When combined with other therapeutic treatments, such as anti-PD-1 or anti-CTLA-4 blockade, cytokines, chemotherapy, or radiotherapy, the anti-tumor activity of agonist anti-OX40 treatment will be further enhanced. These data collectively suggest great potential for OX40-mediated therapies.

Expression of the luteinizing hormone receptor (LHR) in ovarian cancer

We investigated the association of LHR expression in epithelial ovarian cancer (OC) with clinical and pathologic characteristics of patients. LHR expression was examined immunohistochemically using tissue microarrays (TMAs) of specimens from 232 OC patients. Each sample was scored quantitatively evaluating LHR staining intensity (LHR-I) and percentage of LHR (LHR-P) staining cells in tumor cells examined. LHR-I was assessed as no staining (negative), weak (+ 1), moderate (+ 2), and strong positive (+ 3). LHR-P was measured as 1 to 5, 6 to 50% and >  50% of the tumor cells examined. Positive LHR staining was found in 202 (87%) patients' tumor specimens and 66% patients had strong intensity LHR expression. In 197 (85%) of patients, LHR-P was measured in > 50% of tumor cells. LHR-I was significantly associated with pathologic stage (p = 0.007). We found that 72% of stage III or IV patients expressed strong LHR-I in tumor cells. There were 87% of Silberberg's grade 2 or 3 patients compared to 70% of grade 1 patients with LHR expression observed in > 50% of tumor cells, p = 0.037. Tumor stage was significantly associated with overall survival and recurrence free survival, p < 0.001 for both analyses, even after adjustment for age, tumor grade and whether patient had persistent disease after therapy or not. Our study demonstrates that LHR is highly expressed in the majority of OC patients. Both LHR-I and LHR-P are significantly associated with either the pathologic stage or tumor grade.

Expression of costimulatory and inhibitory receptors in FoxP3+ regulatory T cells within the tumor microenvironment: Implications for combination immunotherapy approaches

The unprecedented success of immune checkpoint inhibitors has given rise to a rapidly growing number of immuno-oncology agents undergoing preclinical and clinical development and an exponential increase in possible combinations. Defining a clear rationale for combinations by identifying synergies between immunomodulatory pathways has therefore become a high priority. Immunosuppressive regulatory T cells (Tregs) within the tumor microenvironment (TME) represent a major roadblock to endogenous and therapeutic tumor immunity. However, Tregs are also essential for the maintenance of immunological self-tolerance, and share many molecular pathways with conventional T cells including cytotoxic T cells, the primary mediators of tumor immunity. Hence the inability to specifically target and neutralize Tregs within the TME of cancer patients without globally compromising self-tolerance poses a significant challenge. Here we review recent advances in the characterization of tumor-infiltrating Tregs with a focus on costimulatory and inhibitory receptors. We discuss receptor expression patterns, their functional role in Treg biology and mechanistic insights gained from targeting these receptors in preclinical models to evaluate their potential as clinical targets. We further outline a framework of parameters that could be used to refine the assessment of Tregs in cancer patients and increase their value as predictive biomarkers. Finally, we propose modalities to integrate our increasing knowledge on Treg phenotype and function for the rational design of checkpoint inhibitor-based combination therapies. Such combinations have great potential for synergy, as they could concomitantly enhance cytotoxic T cells and inhibit Tregs within the TME, thereby increasing the efficacy of current cancer immunotherapies.

Combining immunotherapies to treat non-small cell lung cancer

Introduction: In recent years, immunotherapy has become an integral part of the treatment of many cancers, including non-small cell lung cancer (NSCLC). Precious therapeutic weapons impacting survival are monoclonal antibodies directed against the programmed death protein-1 (PD-1)/programmed death ligand-1 (PD-L1) immune checkpoint. Areas covered: Unfortunately, not all patients treated with checkpoint inhibitors have durable clinical responses. However, a better understanding of the complexity of interactions between the immune system and cancer, the latter capable of adopting evasion mechanisms, indicates different opportunities to enhance anti-tumor immunity. Expert opinion: In this paper, we review multiple strategies of combining immunotherapies that exploit not only additional immune checkpoint receptors and ligands but also other synergistic approaches such as vaccines or indoleamine 2,3-dioxygenase (IDO) inhibitors with the potential to extend the number of NSCLC patients achieving successful outcomes.

New strategies in immunotherapy for lung cancer: beyond PD-1/PD-L1

Immunotherapy has significantly altered the treatment landscape for many cancers, including non-small cell lung cancer (NSCLC). Currently approved immuno-oncology agents for lung cancer are aimed at the reversal of immune checkpoints, programmed death protein-1 (PD-1) and programmed death ligand-1 (PD-L1). Although responses to checkpoint inhibitors are encouraging, and in some cases durable, these successes are not universal among all treated patients. In order to optimize our treatment approach utilizing immunotherapy, we must better understand the interaction between cancer and the immune system and evasion mechanisms. In this review, we will provide an overview of the immune system and cancer, and review novel therapies that promote tumor antigen release for immune system detection, activate the effector T-cell response, and reverse inhibitory antitumor signals.

Advancing targeted co-stimulation with antibody-fusion proteins by introducing TNF superfamily members in a single-chain format

Co-stimulation via receptors of the tumor necrosis factor superfamily (TNFSF) emerges as promising strategy to support antitumor immune responses. Targeted strategies with antibody-fusion proteins composed of a tumor-directed antibody part and the extracellular domain of a co-stimulatory ligand of the TNFSF constitute an attractive option to focus the co-stimulatory activity to the tumor site. Since TNFSF members intrinsically form functional units of non-covalently linked homotrimers, the protein engineering of suitable antibody-fusion proteins is challenging. Aiming for molecules of simple and stable configuration, we used TNFSF ligands in a single-chain format (scTNFSF), i.e., three units of the ectodomain connected by polypeptide linkers, folding into an intramolecular trimer. By fusing tumor-directed scFv antibody fragments directed against EpCAM or FAP to co-stimulatory scTNFSF molecules (sc4-1BBL, scOX40L, scGITRL or scLIGHT), a set of monomeric scFv-scTNFSF fusion proteins was generated. In comparison to the scFv-TNFSF format, defined by intermolecular homotrimerization via the TNFSF part, scFv-scTNFSF showed equal or enhanced co-stimulatory activity despite reduced avidity in antibody binding. In addition, enhanced serum stability and improved bioavailability in mice were observed. We show that the scFv-scTNFSF format can be applied to various members of the TNFSF, presenting targeting-dependent co-stimulatory activity. Hence, this format exhibits favorable properties that make it a promising choice for further therapeutic fusion protein development.

Age-dependent divergent effects of OX40L treatment on the development of diabetes in NOD mice

Earlier, we have shown that GM-CSF derived bone marrow (BM) dendritic cells (G-BMDCs) can expand Foxp3(+) regulatory T-cells (Tregs) through a TCR-independent, but IL-2 dependent mechanism that required OX40L/OX40 interaction. While some reports have shown suppression of autoimmunity upon treatment with an OX40 agonist, others have shown exacerbation of autoimmune disease instead. To better understand the basis for these differing outcomes, we compared the effects of OX40L treatment in 6-week-old pre-diabetic and 12-week-old near diabetic NOD mice. Upon treatment with OX40L, 6-week-old NOD mice remained normoglycemic and showed a significant increase in Tregs in their spleen and lymph nodes, while 12-week-old NOD mice very rapidly developed hyperglycemia and failed to show Treg increase in spleen or LN. Interestingly, OX40L treatment increased Tregs in the thymus of both age groups. However, it induced Foxp3(+)CD103(+)CD38(-) stable-phenotype Tregs in the thymus and reduced the frequency of autoreactive Teff cells in 6-week-old mice; while it induced Foxp3(+)CD103(-)CD38(+) labile-phenotype Tregs in the thymus and increased autoreactive CD4(+) T cells in the periphery of 12-week-old mice. This increase in autoreactive CD4(+) T cells was likely due to either a poor suppressive function or conversion of labile Tregs into Teff cells. Using ex vivo cultures, we found that the reduction in Treg numbers in 12-week-old mice was likely due to IL-2 deficit, and their numbers could be increased upon addition of exogenous IL-2. The observed divergent effects of OX40L treatment were likely due to differences in the ability of 6- and 12-week-old NOD mice to produce IL-2.

Exploiting natural anti-tumor immunity for metastatic renal cell carcinoma

Clinical observations of spontaneous disease regression in some renal cell carcinoma (RCC) patients implicate a role for tumor immunity in controlling this disease. Puzzling, however, are findings that high levels of tumor infiltrating lymphocytes (TIL) are common to RCC. Despite expression of activation markers by TILs, functional impairment of innate and adaptive immune cells has been consistently demonstrated contributing to the failure of the immune system to control RCC. Immunotherapy can overcome the immunosuppressive effects of the tumor and provide an opportunity for long-term disease free survival. Unfortunately, complete response rates remain sub-optimal indicating the effectiveness of immunotherapy remains limited by tumor-specific factors and/or cell types that inhibit antitumor immune responses. Here we discuss immunotherapies and the function of multiple immune system components to achieve an effective response. Understanding these complex interactions is essential to rationally develop novel therapies capable of renewing the immune system's ability to respond to these tumors.

Characterization of tumor infiltrating lymphocytes in paired primary and metastatic renal cell carcinoma specimens

Renal cell carcinoma (RCC) is one of the most chemo- and radio-resistant malignancies, with poor associated patient survival if the disease metastasizes. With recent advances in immunotherapy, particularly with PD-1/PD-L1 blockade, outcomes are improving, but a substantial subset of patients does not respond to the new agents. Identifying such patients and improving the therapeutic ratio has been a challenge, although much effort has been made to study PD-1/PD-L1 status in pre-treatment tumor. However, tumor infiltrating lymphocyte (TIL) content might also be predictive of response, and our goal was to characterize TIL content and PD-L1 expression in RCC tumors from various anatomic sites. Utilizing a quantitative immunofluorescence technique, TIL subsets were examined in matched primary and metastatic specimens. In metastatic specimens, we found an association between low CD8+ to Foxp3+ T-cell ratios and high levels of PD-L1. High PD-L1-expressing metastases were also found to be associated with tumors that were high in both CD4+ and Foxp3+ T-cell content. Taken together these results provide the basis for combining agents that target the PD-1/PD-L1 pathway with agonist of immune activation, particularly in treating RCC metastases with unfavorable tumor characteristics and microenvironment. In addition, CD8+ TIL density and CD8:Foxp3 T-cell ratio were higher in primary than metastatic specimens, supporting the need to assess distant sites for predictive biomarkers when treating disseminated disease.

Antibody fusions with immunomodulatory proteins for cancer therapy

The potential of immunomodulatory proteins, in particular cytokines, for cancer therapy is well recognized, but hampered by the toxicity associated with their systemic application. In order to address this problem, targeted delivery by antibody fusion proteins has been early proposed and their development intensively pursued over the last decade. Here, factors influencing the selection and modification of cytokines and antibody formats for this approach are being discussed, indicating current developments and translational advances in the field.

OX40 Agonists and Combination Immunotherapy: Putting the Pedal to the Metal

Recent studies have highlighted the therapeutic efficacy of immunotherapy, a class of cancer treatments that utilize the patient’s own immune system to destroy cancerous cells. Within a tumor the presence of a family of negative regulatory molecules, collectively known as “checkpoint inhibitors,” can inhibit T cell function to suppress anti-tumor immunity. Checkpoint inhibitors, such as CTLA-4 and PD-1, attenuate T cell proliferation and cytokine production. Targeted blockade of CTLA-4 or PD-1 with antagonist monoclonal antibodies (mAbs) releases the “brakes” on T cells to boost anti-tumor immunity. Generating optimal “killer” CD8 T cell responses also requires T cell receptor activation plus co-stimulation, which can be provided through ligation of tumor necrosis factor receptor family members, including OX40 (CD134) and 4-1BB (CD137). OX40 is of particular interest as treatment with an activating (agonist) anti-OX40 mAb augments T cell differentiation and cytolytic function leading to enhanced anti-tumor immunity against a variety of tumors. When used as single agents, these drugs can induce potent clinical and immunologic responses in patients with metastatic disease. However, each of these agents only benefits a subset of patients, highlighting the critical need for more effective combinatorial therapeutic strategies. In this review, we will discuss our current understanding of the cellular and molecular mechanisms by which OX40 agonists synergize with checkpoint inhibitor blockade to augment T cell-mediated anti-tumor immunity and the potential opportunities for clinical translation of combinatorial immunotherapeutic strategies.

Immunotherapy in the treatment of non-small cell lung cancer

Advances in the understanding of the role of the immune system in tumor immunosurveillance have resulted in the recognition that tumors can evade immune destruction via the dysregulation of co-inhibitory or checkpoint signals. This has led to the development of a generation immunotherapeutic agents targeting the immune checkpoint pathway. Recent early phase studies of immune checkpoint modulators, such as CTLA-4, PD-1 and PD-L1 inhibitors in NSCLC have reported promising results with prolonged clinical responses and tolerable toxicity. This article provides an overview of co-stimulatory and inhibitory molecules that regulate the immune response to tumors, recent therapies that have been developed to exploit these interactions and the role of predictive biomarkers in treatment selection.

OX40 engagement depletes intratumoral Tregs via activating FcγRs, leading to antitumor efficacy

Antibodies targeting checkpoint inhibitors or co-stimulatory receptors on T cells have shown significant antitumor efficacy in preclinical and clinical studies. In mouse tumor models, engagement of activating Fcγ receptor (FcγR)-expressing immune cells was recently shown to be required for the tumoricidal activity of antibodies recognizing the tumor necrosis factor superfamily receptor (TNFR) GITR (CD357) and CTLA-4 (CD152). In particular, activating FcγRs facilitated the selective elimination of intratumoral T-cell populations. However, it remains unclear whether FcγRs contribute to the antitumor efficacy of other immunomodulatory antibodies. Here, we explored the mechanism of antitumor activity mediated by an agonistic antibody (clone OX86) to the co-stimulatory TNFR OX40 (CD134). OX40 was highly expressed by intratumoral T cells, particularly those of the FoxP3(+) regulatory T-cell (Treg) lineage. OX86 administration resulted in the depletion of intratumoral regulatory T cells in an activating FcγR-dependent manner, which correlated with tumor regression. Together with previous data from our group and others, these findings support a mechanism whereby antibodies targeting antigens highly expressed by intratumoral T cells can mediate their elimination by FcγR-expressing immune cells, and facilitate subsequent antitumor immunity.

Victory and defeat in the induction of a therapeutic response through vaccine therapy for human and canine brain tumors: a review of the state of the art

Anti-tumor immunotherapy using tumor lysate-based vaccines has made great advances over recent decades. Cancer vaccines aim to elicit adaptive immune responses through various pathways by providing tumor and tumor-associated antigens with an immune stimulant or adjuvant. These anti-tumor vaccines are therefore developed as personalized treatments. Utilizing tumors as a source of vaccine antigens in immunotherapy has demonstrated promising results with minimal toxicity. However, to date, researchers have failed to overcome the overpowering immune suppressive effects within the tumor microenvironment. Immune suppression occurs naturally via multiple mechanisms. These mechanisms serve an important homeostatic role restoring a normal tissue microenvironment following an inflammatory response. Due to these suppressive mechanisms and the inherent heterogeneity of tumors, it is imperative to then elicit and maintain a specific tumoricidal response if vaccine therapy or some other combination of reagents is chosen. In this review, we focus on the historical use of tumors as a source of antigens to elicit a tumoricidal response and the limitations encountered that prevent greater success in immunotherapy. We describe the advantages and disadvantages of various vaccines and their ineffectiveness due to tumor-induced immune suppression.

CD8+ T cell-independent tumor regression induced by Fc-OX40L and therapeutic vaccination in a mouse model of glioma

Despite the growing number of preclinical and clinical trials focused on immunotherapy for the treatment of malignant gliomas, the prognosis for this disease remains grim. Although some promising advances have been made, the immune response stimulated as a result of immunotherapeutic protocols has been inefficient at complete tumor elimination, primarily due to our lack of understanding of the necessary effector functions of the immune system. We previously demonstrated that a tumor lysate vaccine/Fc-OX40L therapy is capable of inducing enhanced survival and tumor elimination in the GL261 mouse glioma model. The following experiments were performed to determine the mechanism(s) of action of this therapy that elicits a potent antitumor immune response. The evidence subsequently outlined indicates a CD8(+) T cell-independent and CD4(+) T cell-, NK cell-, and B cell-dependent means of prolonged survival. CD8(+) T cell-independent tumor clearance is surprising considering the current focus of many cancer immunotherapy protocols. These results provide evidence for CD8(+) T cell-independent means of antitumor response and should lead to additional examination of the potential manipulation of this mechanism for future treatment strategies.

An in vivo immunotherapy screen of costimulatory molecules identifies Fc-OX40L as a potent reagent for the treatment of established murine gliomas

PURPOSE

We tested the combination of a tumor lysate vaccine with a panel of costimulatory molecules to identify an immunotherapeutic approach capable of curing established murine gliomas.

EXPERIMENTAL DESIGN

Glioma-bearing mice were primed with a tumor lysate vaccine, followed by systemic administration of the following costimulatory ligands: OX40L, CD80, 4-1BBL, and GITRL, which were fused to the Fc portion of human immunoglobulin. Lymphocytes and mRNA were purified from the brain tumor site for immune monitoring studies. Numerous variations of the vaccine and Fc-OX40L regimen were tested alone or in combination with temozolomide.

RESULTS

Lysate vaccinations combined with Fc-OX40L led to the best overall survival, yielding cure rates of 50% to 100% depending on the timing, regimen, and combination with temozolomide. Cured mice that were rechallenged with glioma cells rejected the challenge, showing immunologic memory. Lymphocytes isolated from the draining lymph nodes of vaccine/Fc-OX40L-treated mice had superior tumoricidal function relative to all other groups. Vaccine/Fc-OX40L-treated mice exhibited a significant increase in proliferation of brain-infiltrating CD4 and CD8 T cells, as indicated by Ki67 staining. Fc-OX40L had single-agent activity in transplanted and spontaneous glioma models, and the pattern of inflammatory gene expression in the tumor predicted the degree of therapeutic response.

CONCLUSIONS

These data show that Fc-OX40L has unique and potent activity against experimental gliomas and warrants further testing.

Chemokines, costimulatory molecules and fusion proteins for the immunotherapy of solid tumors

In this article, the role of chemokines and costimulatory molecules in the immunotherapy of experimental murine solid tumors and immunotherapy used in ongoing clinical trials are presented. Chemokine networks regulate physiologic cell migration that may be disrupted to inhibit antitumor immune responses or co-opted to promote tumor growth and metastasis in cancer. Recent studies highlight the potential use of chemokines in cancer immunotherapy to improve innate and adaptive cell interactions and to recruit immune effector cells into the tumor microenvironment. Another critical component of antitumor immune responses is antigen priming and activation of effector cells. Reciprocal expression and binding of costimulatory molecules and their ligands by antigen-presenting cells and naive lymphocytes ensures robust expansion, activity and survival of tumor-specific effector cells in vivo. Immunotherapy approaches using agonist antibodies or fusion proteins of immunomodulatory molecules significantly inhibit tumor growth and boost cell-mediated immunity. To localize immune stimulation to the tumor site, a series of fusion proteins consisting of a tumor-targeting monoclonal antibody directed against tumor necrosis and chemokines or costimulatory molecules were generated and tested in tumor-bearing mice. While several of these reagents were initially shown to have therapeutic value, combination therapies with methods to delete suppressor cells had the greatest effect on tumor growth. In conclusion, a key conclusion that has emerged from these studies is that successful immunotherapy will require both advanced methods of immunostimulation and the removal of immunosuppression in the host.

Autoimmune therapies targeting costimulation and emerging trends in multivalent therapeutics

Proteins participating in immunological signaling have emerged as important targets for controlling the immune response. A multitude of receptor-ligand pairs that regulate signaling pathways of the immune response have been identified. In the complex milieu of immune signaling, therapeutic agents targeting mediators of cellular signaling often either activate an inflammatory immune response or induce tolerance. This review is primarily focused on therapeutics that inhibit the inflammatory immune response by targeting membrane-bound proteins regulating costimulation or mediating immune-cell adhesion. Many of these signals participate in larger, organized structures such as the immunological synapse. Receptor clustering and arrangement into organized structures is also reviewed and emerging trends implicating a potential role for multivalent therapeutics is posited.

Signaling through OX40 enhances antitumor immunity

The existence of tumor-specific T cells, as well as their ability to be primed in cancer patients, confirms that the immune response can be deployed to combat cancer. However, there are obstacles that must be overcome to convert the ineffective immune response commonly found in the tumor environment to one that leads to sustained destruction of tumor. Members of the tumor necrosis factor (TNF) superfamily direct diverse immune functions. OX40 and its ligand, OX40L, are key TNF members that augment T-cell expansion, cytokine production, and survival. OX40 signaling also controls regulatory T-cell differentiation and suppressive function. Studies over the past decade have demonstrated that OX40 agonists enhance antitumor immunity in preclinical models using immunogenic tumors; however, treatment of poorly immunogenic tumors has been less successful. Combining strategies that prime tumor-specific T cells together with OX40 signaling could generate and maintain a therapeutic antitumor immune response.

Integrating costimulatory agonists to optimize immune-based cancer therapies

While immunotherapy for cancer has become increasingly popular, clinical benefits for such approaches remain limited. This is likely due to tumor-associated immune suppression, particularly in the advanced-disease setting. Thus, a major goal of novel immunotherapeutic design has become the coordinate reversal of existing immune dysfunction and promotion of specific tumoricidal T-cell function. Costimulatory members of the TNF-receptor family are important regulators of T-cell-mediated immunity. Notably, agonist ligation of these receptors restores potent antitumor immunity in the tumor-bearing host. Current Phase I/II evaluation of TNF-receptor agonists as single-modality therapies will illuminate their safety, mechanism(s) of action, and best use in prospective combinational immunotherapy approaches capable of yielding superior benefits to cancer patients.

A therapeutic OX40 agonist dynamically alters dendritic, endothelial, and T cell subsets within the established tumor microenvironment

Little preclinical modeling currently exists to support the use of OX40 agonists as therapeutic agents in the setting of advanced cancers, as well as the mechanisms through which therapeutic efficacy is achieved. We show that treatment of mice bearing well-established day 17 sarcomas with a novel OX40 ligand-Fc fusion protein (OX40L-Fc) resulted in tumor regression or dormancy in the majority of treated animals. Unexpectedly, dendritic cells (DC) in the progressive tumor microenvironment (TME) acquire OX40 expression and bind fluorescently labeled OX40L-Fc. Furthermore, longitudinal analyses revealed that DCs become enriched in the tumor-draining lymph node (TDLN) of both wild-type and Rag-/- mice within 3 days after OX40L-Fc treatment. By day 7 after treatment, a significant expansion of CXCR3+ T effector cells was noted in the TDLN, and by day 10 after treatment, type 1 polarized T cells exhibiting a reactivated memory phenotype had accumulated in the tumors. High levels of CXCL9 (a CXCR3 ligand) and enhanced expression of VCAM-1 by vascular endothelial cells (VEC) were observed in the TME early after treatment with OX40L-Fc. Notably, these vascular alterations were maintained in Rag-/- mice, indicating that the OX40L-Fc-mediated activation of both DC and VEC occurs in a T-cell-independent manner. Collectively, these findings support a paradigm in which the stimulation of DC, T cells, and the tumor vasculature by an OX40 agonist dynamically orchestrates the activation, expansion, and recruitment of therapeutic T cells into established tumors.

The role of OX40 (CD134) in T-cell memory generation

Memory T-cell generation is limited by activation-induced cell death during the effector T-cell stage. Cell surface proteins are known to transmit signals that either accentuate or limit T-cell death after activation. This chapter will focus on the TNF-receptor family member OX40, which is expressed on effector T cells and when engaged greatly enhances survival of T cells leading to increased memory T-cell generation. Targeting OX40 in vivo can alter the fate ofT-cell survival. Enhancing OX40 signaling during Ag priming through agonists increases memory T-cell development, while blocking OX40 signaling decreases the memory T-cell pool. These two opposing outcomes provide therapeutic tools for blocking inflammation in autoimmune conditions and enhancing immunity in hosts harboring cancer or chronic pathogens. OX40 agonists and antagonists are in the first stages of human clinical trials and their therapeutic potential will soon be realized.

The significance of OX40 and OX40L to T-cell biology and immune disease

SUMMARY

OX40 (CD134) and its binding partner, OX40L (CD252), are members of the tumor necrosis factor receptor/tumor necrosis factor superfamily and are expressed on activated CD4(+) and CD8(+) T cells as well as on a number of other lymphoid and non-lymphoid cells. Costimulatory signals from OX40 to a conventional T cell promote division and survival, augmenting the clonal expansion of effector and memory populations as they are being generated to antigen. OX40 additionally suppresses the differentiation and activity of T-regulatory cells, further amplifying this process. OX40 and OX40L also regulate cytokine production from T cells, antigen-presenting cells, natural killer cells, and natural killer T cells, and modulate cytokine receptor signaling. In line with these important modulatory functions, OX40-OX40L interactions have been found to play a central role in the development of multiple inflammatory and autoimmune diseases, making them attractive candidates for intervention in the clinic. Conversely, stimulating OX40 has shown it to be a candidate for therapeutic immunization strategies for cancer and infectious disease. This review provides a broad overview of the biology of OX40 including the intracellular signals from OX40 that impact many aspects of immune function and have promoted OX40 as one of the most prominent costimulatory molecules known to control T cells.

OX40 engagement and chemotherapy combination provides potent antitumor immunity with concomitant regulatory T cell apoptosis

Expansion and recruitment of CD4⁺ Foxp3⁺ regulatory T (T reg) cells are mechanisms used by growing tumors to evade immune elimination. In addition to expansion of effector T cells, successful therapeutic interventions may require reduction of T reg cells within the tumor microenvironment. We report that the combined use of the alkylating agent cyclophosphamide (CTX) and an agonist antibody targeting the co-stimulatory receptor OX40 (OX86) provides potent antitumor immunity capable of regressing established, poorly immunogenic B16 melanoma tumors. CTX administration resulted in tumor antigen release, which after OX86 treatment significantly enhanced the antitumor T cell response. We demonstrated that T reg cells are an important cellular target of the combination therapy. Paradoxically, the combination therapy led to an expansion of T reg cells in the periphery. In the tumor, however, the combination therapy induced a profound T reg cell depletion that was accompanied by an influx of effector CD8⁺ T cells leading to a favorable T effector/T reg cell ratio. Closer examination revealed that diminished intratumoral T reg cell levels resulted from hyperactivation and T reg cell–specific apoptosis. Thus, we propose that CTX and OX40 engagement represents a novel and rational chemoimmunotherapy.

The role of TNF superfamily members in T-cell function and diseases

Interactions that occur between several tumour necrosis factor (TNF)-TNF receptors that are expressed by T cells and various other immune and non-immune cell types are central to T-cell function. In this Review, I discuss the biology of four different ligand-receptor interactions - OX40 ligand and OX40, 4-1BB ligand and 4-1BB, CD70 and CD27, and TL1A and death receptor 3 - and their potential to be exploited for therapeutic benefit. Manipulating these interactions can be effective for treating diseases in which T cells have an important role, including inflammatory conditions, autoimmunity and cancer. Here, I explore how blocking or inducing the signalling pathways that are triggered by these different interactions can be an effective way to modulate immune responses.