The amountof ILDR2 peptides in kidney and testis samples derived fromhuman, monkey and mouse.

Antitumor efficacy of BAY1905254 and antiâ€"PD-L1 in monotherapy or in combination in a panel of syngeneic mouse models shown as T/C values.

Immune checkpoint inhibitors (ICIs) have emerged as promising therapies for the treatment of cancer. However, existing ICIs, namely PD-(L)1 and CTLA-4 inhibitors, generate durable responses only in a subset of patients. TIGIT is a co-inhibitory receptor and member of the DNAM-1 family of immune modulating proteins. We evaluated the prevalence of TIGIT and its cognate ligand, PVR (CD155), in human cancers by assessing their expression in a large set of solid tumors. TIGIT is expressed on CD4+ and CD8+ TILs and is upregulated in tumors compared to normal tissues. PVR is expressed on tumor cells and tumor-associated macrophages from multiple solid tumors. We explored the therapeutic potential of targeting TIGIT by generating COM902, a fully human anti-TIGIT hinge-stabilized IgG4 monoclonal antibody that binds specifically to human, cynomolgus monkey, and mouse TIGIT, and disrupts the binding of TIGIT with PVR. COM902, either alone or in combination with a PVRIG (COM701) or PD-1 inhibitor, enhances antigen-specific human T cell responses in-vitro. In-vivo, a mouse chimeric version of COM902 in combination with an anti-PVRIG or anti-PD-L1 antibody inhibited tumor growth and increased survival in two syngeneic mouse tumor models. In summary, COM902 enhances anti-tumor immune responses and is a promising candidate for the treatment of advanced malignancies.

This study explored the novel immune checkpoint poliovirus receptor-related immunoglobulin domain-containing (PVRIG) in acute myeloid leukemia (AML). We showed that AML patient blasts consistently expressed the PVRIG ligand (poliovirus receptor-related 2, PVRL2). Furthermore, PVRIG blockade significantly enhanced naural killer (NK)-cell killing of PVRL2(+), poliovirus receptor (PVR)(lo) AML cell lines, and significantly increased NK-cell activation and degranulation in the context of patient primary AML blasts. However, in AML patient bone marrow, NK-cell PVRIG expression levels were not increased. In order to understand how PVRIG blockade might potentially be exploited therapeutically, we investigated the biology of PVRIG and revealed that NK-cell activation resulted in reduced PVRIG expression on the cell surface. This occurred whether NK cells were activated by tumor cell recognition, cytokines (interleukin 2 [IL-2] and IL-12) or activating receptor stimulation (CD16 and NKp46). PVRIG was present at higher levels in the cytoplasm than on the cell surface, particularly on CD56(bright) NK cells, which further increased cytoplasmic PVRIG levels following IL-2 and IL-12 activation. PVRIG was continually transported to the cell surface via the endoplasmic reticulum and Golgi in both unstimulated and activated NK cells. Taken together, our findings suggest that anti-PVRIG blocking antibody functions by binding to surface-bound PVRIG, which undergoes rapid turnover in both unstimulated and activated NK cells. We conclude that the PVRIG-PVRL2 immune checkpoint axis can feasibly be targeted with PVRIG blocking antibody for NK-mediated immunotherapy of PVRL2(+) AML.

Therapeutic antibodies targeting the CTLA-4/ PD-1 pathways have revolutionized cancer immunotherapy by eliciting durable remission in cancer patients. However, relapse following early response, attributable to primary and adaptive resistance, is frequently observed. Additional immunomodulatory pathways are being studied in patients with primary or acquired resistance to CTLA-4 or PD-1 blockade. The DNAM-1 axis is a potent co-regulator of innate and adaptive immunity whose other components include the immunoglobulin receptors TIGIT, PVRIG and CD96, and their nectin and nectin-like ligands. We review the basic biology and therapeutic relevance of this family, which has begun to show promise in cancer clinical trials.

TPS23 Background: COM701 is a novel 1st-in-class monoclonal antibody that binds with high affinity to poliovirus receptor related immunoglobulin domain containing (PVRIG) blocking its interaction with its ligand, PVRL2. In preclinical experiments inhibition of PVRIG alone and in combination with a PD-1 inhibitor leads to activation of T cells in the tumor microenvironment generating an anti-tumor immune response leading to tumor growth inhibition. Novel checkpoint therapies are needed for the treatment of patients with advanced malignancies. We hypothesized that COM701 monotherapy and in combination with nivolumab will be safe and tolerable and demonstrate preliminary antitumor activity in pts with advanced solid malignancies. Methods: This ongoing phase 1 study (NCT03667716) is evaluating the safety and tolerability of escalating doses of COM701 monotherapy IV Q3 or Q4 weekly and in combination with nivolumab 360 mg IV Q3 weekly or 480 mg IV Q4 weekly. Key Inclusion Criteria: Age ≥18 yrs, histologically or cytologically confirmed advanced solid malignancy and has exhausted all available standard therapy, ECOG performance status 0-1, prior ICI permissible. Key Exclusion Criteria: Symptomatic interstitial lung disease or inflammatory pneumonitis, untreated or symptomatic central nervous system metastases. Primary outcome measures are the incidence of adverse events and dose-limiting toxicities (21-day or 28-day DLT window), pharmacokinetics of COM701 and to identify the maximum tolerated dose and/or the recommended dose for expansion. Key secondary outcome measures are to characterize the immunogenicity and preliminary antitumor activity of COM701 as monotherapy and in combination with nivolumab. Study Design: Hybrid accelerated titration and 3+3 study design. Statistical Considerations: Adverse events graded as per CTCAE v4.03, responses as per RECIST v1.1. Analyses of all study objectives are descriptive and hypothesis generating. As of the date of this submission dose level 8 of COM701 monotherapy and dose level 3 of the combination arm are open to enrollment. Updated data will be presented at the conference. Clinical trial information: NCT03667716.

AbstractThe immunoglobulin-like domain containing receptor 2 (ILDR2), a type I transmembrane protein belonging to the B7 family of immunomodulatory receptors, has been described to induce an immunosuppressive effect on T-cell responses. Besides its expression in several nonlymphoid tissue types, we found that ILDR2 was also expressed in fibroblastic reticular cells (FRC) in the stromal part of the lymph node. These immunoregulatory cells were located in the T-cell zone and were essential for the recruitment of naïve T cells and activated dendritic cells to the lymph nodes. Previously, it has been shown that an ILDR2-Fc fusion protein exhibits immunomodulatory effects in several models of autoimmune diseases, such as multiple sclerosis, rheumatoid arthritis, and type I diabetes. Herein, we report the generation and characterization of a human/mouse/monkey cross-reactive anti-ILDR2 hIgG2 antibody, BAY 1905254, developed to block the immunosuppressive activity of ILDR2 for cancer immunotherapy. BAY 1905254 was shown to promote T-cell activation in vitro and enhance antigen-specific T-cell proliferation and cytotoxicity in vivo in mice. BAY 1905254 also showed potent efficacy in various syngeneic mouse cancer models, and the efficacy was found to correlate with increasing mutational load in the cancer models used. Additive or even synergistic antitumor effects were observed when BAY 1905254 was administered in combination with anti–PD-L1, an immunogenic cell death–inducing chemotherapeutic, or with tumor antigen immunization. Taken together, our data showed that BAY 1905254 is a potential drug candidate for cancer immunotherapy, supporting its further evaluation.

TPS40 Background: Novel checkpoint therapies are needed for the treatment of patients who relapse/refractory to treatment with checkpoint inhibitors. COM701 is a novel first-in-class humanized IgG4 monoclonal antibody that binds with high affinity to poliovirus receptor related immunoglobulin domain containing (PVRIG) blocking its interaction with it's ligand, PVRL2. We have demonstrated in preclinical experiments that inhibition of PVRIG leads to activation of T cells in the tumor microenvironment generating an anti-tumor immune response leading to tumor growth inhibition. We hypothesize that COM701 will be safe and tolerable and demonstrate antitumor activity in pts with R/R solid tumors. Methods: NCT03667716 is an ongoing open-label first-in-human phase 1 study in pts with R/R solid tumors. The initial part of this study will evaluate the safety and tolerability of escalating doses of COM701 monotherapy IV Q3 weekly. Key Inclusion Criteria: Age ≥18 yrs, histologically or cytologically confirmed, locally advanced or metastatic solid malignancy and has exhausted all the available standard therapy or is not a candidate for the available standard therapy, ECOG performance status 0-1, prior anti-PD-1, anti-PD-L1, anti-CTLA-4, OX-40, CD137. Key Exclusion Criteria: Active autoimmune disease requiring systemic therapy in the last 2 years prior to the first dose of COM701, symptomatic interstitial lung disease or inflammatory pneumonitis, untreated or symptomatic central nervous system metastases. Primary outcome measures are the incidence of adverse events and dose-limiting toxicities (21-day DLT window), pharmacokinetics of COM701 and to identify the maximum tolerated dose and/or the recommended dose for expansion. Secondary outcome measures are to characterize the immunogenicity and preliminary antitumor activity of COM701. Study Design: Accelerated titration design consisting of single subject cohorts has been implemented for the initial cohorts. Statistical Considerations: Adverse events graded as per CTCAE v4.03, responses as per RECIST v1.1. The analyses of all study objectives will be descriptive and hypothesis generating. As of the date of this submission a third single subject dose cohort has been filled.

Abstract Background: While blockade of the CTLA4 and PD1 pathways has emerged as an effective treatment of cancer, the majority of patients do not derive long term benefit. This provides a rationale for identifying and targeting additional checkpoints. Employing our unique computational algorithms, we identified PVRIG, a new member of the B7/CD28 family. We report here the expression pattern, functional characterization, and anti-tumor activity of blocking antibodies targeting PVRIG as well as characterization of PVRIG KO mice. Materials and Methods: PVRIG is expressed by T and NK cells within the tumor microenvironment. We identified PVRL2 as its counterpart and characterized the PVRIG-PVRL2 interaction. Antibody discovery was carried out with phage display and hybridoma platforms and antibodies against the human protein were screened for their ability to enhance T-cell activity in vitro, while surrogate antibodies targeting the mouse protein were assessed in syngeneic models for effects on tumor growth. PVRIG -/- KO mice were generated and characterized including phenotyping and anti-tumor immune response. Results: PVRIG is expressed on different T cell subsets and on NK, NKT and γδ T-cells. Within T cells, memory subsets possess the highest level of PVRIG and its expression is induced upon long term activation with different stimuli. Within tumor microenvironment, PVRIG was found to be expressed on NK and CD8+ T cells in multiple cancers. A high affinity lead Ab was selected, COM701, for further clinical development and demonstrated blockade of the interaction of PVRIG with PVRL2 as well as enhancement of activation of both primary and tumor-derived effector immune cells through a PVRL2-dependent mechanism. Moreover, COM-701 showed notable enhancement of T cell function in-vitro when combined with PD1 or TIGIT Ab blockade. The lead antibody, COM-701, is currently in preclinical development. A surrogate antibody, that blocks PVRIG-PVRL2 interaction, was shown to inhibit growth of colon carcinoma and melanoma in syngeneic models upon combined treatment with anti-PDL1 antibody. Comparative analysis of PVRIG KO versus WT derived T cells revealed enhanced reactivity of PVRIG null T cells upon polyclonal activation in presence of PVRL2-Ig. Accordingly, MC38 tumors grew slower in PVRIG KO than in WT mice and ex vivo analysis pointed to the quantitative and functional differences in anticancer immunity developed in these mice. Conclusion: We describe the identification of PVRIG as a novel T cell immune checkpoint. We further demonstrate that antibody blockade of the PVRIG-PVRL2 interaction has the potential to be efficiently combined with PD1 or TIGIT blockade for enhancing anti-tumor immunity. COM-701 is a high affinity antagonistic antibody that is currently in preclinical development. Taken together, these data demonstrate the utility of targeting PVRIG in addition to other B7 family checkpoints for the treatment of cancer. Citation Format: Ofer Levy, Chris Chan, Gady Cojocaru, Spencer Liang, Eran Ophir, Sudipto Ganguly, Maya Kotturi, Tal Friedman, Benjamin Murter, Liat Dassa, Ling Leung, Shirley Greenwald, Meir Azulay, Sandeep Kumar, Zoya Alteber, Xiaoyu Pan, Andy Drake, Ran Salomon, Arthur Machlenkin, John Hunter, Zurit Levine, Drew Pardoll, Mark White. Discovery and development of COM701, a therapeutic antibody targeting the novel immune checkpoint PVRIG [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 581. doi:10.1158/1538-7445.AM2017-581

Meeting abstracts Members of the B7/CD28 family of immune checkpoints, such as CTLA4, PD1 and PDL-1, play critical roles in T cell regulation and have emerged as promising drug targets for cancer immunotherapy. We hypothesize that additional novel members of the B7/CD28 family play a role as

Objective: Atherosclerosis is a condition that is increasingly contributing to worldwide mortality through complications such as stroke and myocardial infarction. IL-1 beta plays multiple direct, local roles in the formation and stability of the atheroma by eliciting the production of additional cytokines and proteolytic enzymes from macrophages, endothelial cells (EC) and smooth muscle cells (SMC). We therefore tested whether an anti-IL-1 beta antibody, XOMA052, might inhibit the secretion of pro-atherogenic cytokines from macrophages in vitro and affect a positive outcome in the Apolipoprotein E-deficient mouse (ApoE(-/-)) model of atherosclerosis in vivo.Methods and results: In an in vitro co-culture model, XOMA 052 inhibited macrophage-induced secretion of key atherogenic cytokines from EC and SMC, including IL-6, IL-8, MCP-1 and TNF alpha. The release of degradative enzymes, such as the matrix metalloproteinases MMP-3 and MMP-9, was also decreased by XOMA 052. In addition, XOMA 052 inhibited the secretion of IL-7 from EC and IL-4 from SMC, cytokines not previously reported to be driven by IL-1 beta in this context. In vivo, XMA052 MG1K, a chimeric murine version of XOMA 052, inhibited the formation of atherosclerotic lesions in the ApoE(-/-) model at all three doses tested. This effect was comparable to that reported for complete genetic ablation of IL-1 beta or IL-1R1 on an ApoE(-/-) background and was associated with decreases in plasma non-HDL/HDL cholesterol ratio and plaque lipid content and macrophage infiltration.Conclusions: These results demonstrate for the first time that an antibody targeting IL-1 beta can inhibit the progression of atherosclerosis in vivo, highlighting the importance of this key cytokine in cardiovascular disease. (C) 2011 Elsevier Ireland Ltd. All rights reserved.

Many therapeutic antibodies act as antagonists to competitively block cellular signaling pathways. We describe here an approach for the therapeutic use of monoclonal antibodies based on context-dependent attenuation to reduce pathologically high activity while allowing homeostatic signaling in biologically important pathways. Such attenuation is achieved by modulating the kinetics of a ligand binding to its various receptors and regulatory proteins rather than by complete blockade of signaling pathways. The anti-interleukin-1beta (IL-1beta) antibody XOMA 052 is a potent inhibitor of IL-1beta activity that reduces the affinity of IL-1beta for its signaling receptor and co-receptor but not for its decoy and soluble inhibitory receptors. This mechanism shifts the effective dose response of the cytokine so that the potency of IL-1beta bound by XOMA 052 is 20-100-fold lower than that of IL-1beta in the absence of antibody in a variety of in vitro cell-based assays. We propose that by decreasing potency of IL-1beta while allowing binding to its clearance and inhibitory receptors, XOMA 052 treatment will attenuate IL-1beta activity in concert with endogenous regulatory mechanisms. Furthermore, the ability to bind the decoy receptor may reduce the potential for accumulation of antibody.target complexes. Regulatory antibodies like XOMA 052, which selectively modulate signaling pathways, may represent a new mechanistic class of therapeutic antibodies.

Aurora A is a serine/threonine protein kinase essential for normal mitotic progression. Aberrant increased expression of Aurora A, which occurs frequently in human cancers, results in abnormal mitoses leading to chromosome instability and possibly tumorigenesis. Consequently, Aurora A has received considerable attention as a potential target for anticancer therapeutic intervention. Aurora A coordinates several essential mitotic activities through phosphorylation of a variety of proteins, including TACC3, which modulates microtubule stabilization of the mitotic spindle. Recent studies identified a conserved serine in Xenopus (Ser(626)) and Drosophila (Ser(863)) TACC3 orthologues that is phosphorylated by Aurora A. We show that this conserved serine on human TACC3 (Ser(558)) is also phosphorylated by Aurora A. Moreover, phosphorylation of TACC3 by Aurora A in human cells is essential for its proper localization to centrosomes and proximal mitotic spindles. Inhibition of Aurora A with the selective small molecule inhibitor MLN8054 in cultured human tumor cells resulted in mislocalization of TACC3 away from mitotic spindles in a concentration-dependent manner. Furthermore, oral administration of MLN8054 to nude mice bearing HCT-116 human tumor xenografts caused a dose-dependent mislocalization of TACC3 away from spindle poles that correlated with tumor growth inhibition. As TACC3 localization to mitotic spindles depends on Aurora A-mediated phosphorylation, quantifying TACC3 mislocalization represents a novel pharmacodynamic approach for measuring Aurora A activity in cancer patients treated with inhibitors of Aurora A kinase.

Several transgenic mouse models of prostate cancer have been developed recently that are able to recapitulate many key biological features of the human condition. It would, therefore, be desirable to employ these models to test the efficacy of new therapeutics before clinical trial; however, the variable onset and non-visible nature of prostate tumor development limit their use for such applications. We now report the generation of a transgenic reporter mouse that should obviate these limitations by enabling noninvasive in vivo bioluminescence imaging of normal and spontaneously transformed prostate tissue in the mouse. We used an 11-kb fragment of the human prostate-specific antigen (PSA) promoter to achieve specific and robust expression of firefly luciferase in the prostate glands of transgenic mice. Ex vivo bioluminescence imaging and in situ hybridization analysis confirmed that luciferase expression was restricted to the epithelium in all four lobes of the prostate. We also show that PSA-Luc mice exhibit decreased but readily detectable levels of in vivo bioluminescence over extended time periods following androgen ablation. These results suggest that this reporter should enable in vivo imaging of both androgen-dependent and androgen-independent prostate tumor models. As proof-of-principle, we show that we could noninvasively image SV40 T antigen-induced prostate tumorigenesis in mice with PSA-Luc. Furthermore, we show that our noninvasive imaging strategy can be successfully used to image tumor response to androgen ablation in transgenic mice and, as a result, that we can rapidly identify individual animals capable of sustaining tumor growth in the absence of androgen.