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V-domain Immunoglobulin Suppressor of T cell Activation (VISTA/PD-1H) is a B7 family member highly expressed on circulating and intra-tumoral myeloid cells. It is a negative checkpoint inhibitor that inhibits anti-tumor T cell response. In patients, VISTA is associated with poor overall survival in multiple tumor indications and is also a potential mediator of resistance to anti-CTLA-4 and anti-PD1 therapies. Therefore, VISTA is a unique target for cancer immunotherapy. Kineta has developed a fully human monoclonal antibody targeting VISTA, KVA12123, that is currently being evaluated in a Phase 1/2 clinical trial in cancer patients with advanced solid tumors. This trial also includes a combination arm with pembrolizumab. In order to inform which patients may be susceptible to respond to our anti-VISTA antibody, we hypothesized that the best responders should be associated with a high expression of the target in the tumor microenvironment (TME). Therefore, after assay validation of VISTA labelling by immuno-histochemistry, we analyzed a large set of tumor samples and showed that VISTA was highly expressed on tumor infiltrating immune cells. This was particularly true for patients with non-small cell lung cancers, colorectal cancers, head and neck squamous cell carcinomas, hepatocellular carcinomas, melanomas and squamous cell carcinoma of the skin, and cervical cancers as well as ovarian cancers. VISTA expression was detected mostly on CD163 positive macrophages infiltrating the tumor. These macrophages potentially promote immunosuppression present in the TME and contribute to treatment failure with current immune checkpoint inhibitors like anti-PD1/PD-L1 and CTLA-4. While previous studies reported VISTA expression on cancer cells, we were not able to confirm these results. In all tumor tissues tested, only infiltrating immune cells were labelled for VISTA. We have investigated in parallel the expression level of soluble VISTA in the serum collected from cancer patients independent of this clinical trial. Sera were screened for patients with multiple tumor types. Patients of diverse sex and age were compared to healthy donors. After validation of the ELISA assay, we showed that sera derived from cancer patients exhibit high levels of soluble VISTA, and these levels tend to correlate with age. More data are needed to confirm that high levels of soluble VISTA are associated with advanced disease. In the ongoing Phase 1/2 clinical trial, tumor tissues and serum samples will be collected from cancer patients prior to treatment with KVA12123 to inform the possible significance of these biomarkers. This work could help to better understand the response to KVA12123 in relation to the expression level of VISTA in cancer tissues as well as in the blood. Citation Format: Neda Kabi, Chen Katz, Remington Lance, Jessica Cross, Nathan Eyde, Emily Frazier, Kurt Lustig, Yulia Ovechkina, David Peckham, Shaarwari Sridhar, Carla Talbaux, Isabelle Tihista, Mei Xu, Shawn Iadonato, Thierry Guillaudeux. VISTA expression in patients with advanced solid tumors: A potential biomarker in VISTA-101 clinical trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 972.

CD27 is a member of the TNF-receptor superfamily, highly expressed on CD4+ and CD8+ T cells as well as on NK and NKT cells. It plays a key role on T cell proliferation and differentiation after stimulation with its ligand CD70. The co-stimulatory signal of CD27 on T cell is mediated via the NFκB pathway but also via the phosphatidylinositol 3 kinase and the protein kinase B. CD27/CD70 co-stimulation has the potential to boost immunity by T-cell activation, clonal expansion and enhanced differentiation into antigen specific cytotoxic and memory T cells. CD27/CD70 also influences the innate immune response via a direct activation of the NK cells and a subsequent secretion of interferon-gamma (IFN-γ). Therefore, CD27 signaling promotes cytotoxic T cell based anti-tumor immunity. With its central role in an immunological response, CD27 is a promising target for antitumor therapy. Previous works have demonstrated the efficacy of an agonistic CD27 antibody in controlling tumor growth and metastasis in different mice models including melanoma, renal cell carcinoma, breast cancer and lymphomas. This anti-tumor effect is mediated in part by an effective recruitment of IFN-γ producing CD8+ T cells within the tumor. Moreover, CD27 stimulation of Tumor Infiltrating Lymphocytes (TILs) can lower their threshold of activation and provide a broader repertoire of Ag-reactive T cells within the tumor. We have selected a lead therapeutic antibody from our library of 147 fully human anti-CD27 monoclonal antibodies generated in the Trianni mice. After confirming its binding potency and selectivity as well as its cross-reactivity with Non-Human Primate (NHP)-CD27 but not with the mouse-CD27, this lead candidate demonstrated strong agonistic proprieties. This was shown by its ability to induce a strong NFκB signal as well as to induce T cell proliferation and activation with secretion of pro-inflammatory cytokines. This antibody demonstrated agonistic proprieties without cross-linking confirming its potency. T cell activation observed after treatment with our anti-CD27 antibody only occurs in the presence of TCR engagement, preventing the risk of spontaneous activation of naïve T cells in vivo. The ability of our CD27 monoclonal antibody to increase an immune response was confirmed in a Mixed Lymphocyte Reaction assay with multiple donors. The role played by the NK cells and their activation via CD27 antibody was also demonstrated. To evaluate the anti-tumor functions of our lead antibody as a single agent or in combination with other immuno-therapies in vivo we have used human CD27 transgenic mice. We have demonstrated in the MB49 bladder tumor model as well as the EG7 thymoma model that our lead antibody induces a strong single agent anti-tumor activity and these tumors were totally controlled in combination with an anti-PD1 antibody. We are now analyzing the pharmacokinetic and pharmacodynamic of our antibody as well as its safety in a NHP model Citation Format: Thierry Guillaudeux, Yulia Ovechkina, Shaarwari Sridhar, David Peckham, Jessica Cross, Nathan Eyde, Emily Frazier, Neda Kabi, Remington Lance, Kurt Lustig, Mei Xu, Tarcha Eric, Shawn Iadonato. CD27 a new immuno-oncology target shaping innate and adaptive anti-tumor immune responses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4261.

Background V-domain Immunoglobulin Suppressor of T cell Activation (VISTA/PD-1H) is a B7 family ligand expressed on circulating and intratumoural myeloid cells as well as Treg and NK cells. It has been shown to inhibit T cell responses in vitro and in preclinical models. In patients, VISTA is also a potential mediator of resistance to anti-CTLA-4 and anti-PD1 therapies and therefore is a valuable new target for cancer immunotherapy. Methods Kineta has analyzed 107 fully human ScFv antibodies directed against VISTA. Results Our lead candidates exhibit high potencies in the subnanomolar range and are also characterized by a long kDis. They specifically target human and cynomolgus monkey VISTA on a singular unique epitope. In a Staphylococcus Enterotoxin B T-cell activation assay, Kineta’s anti-VISTA antibodies efficiently induce IFNg secretion. They also promote strong maturation of Antigen Presenting Cells with an increase of CD80 and HLA-DR surface expression as well as CXCL10 secretion. The mechanism of action is mediated in part by NK cells. We demonstrated that myeloid cells acquire a high level of VISTA expression during MDSC or M2 differentiation in vitro and that Kineta’s anti-VISTA antibodies prevent the differentiation of MDSC as well as their immunosuppressive activity against T cells. Anti-VISTA antibodies mediate single-agent antitumor effects in syngeneic tumor models in wild-type mice and show enhanced activity in combination with anti-PD1 and anti-CTLA-4 treatment. Candidate anti-VISTA antibodies have also been evaluated in exploratory tolerability and PK studies in cynomolgus monkey. These studies demonstrated that multiple weekly doses of antibodies are well-tolerated with appropriate PK for lead selection and optimization. Conclusions Our results strongly favor further characterization and continued development of selected lead antibodies for the potential treatment of colder, less immunogenic tumors. Ethics Approval Study approved by the Institutional Animal Care and Use Committee PHS Assurance # D16-00885 and D16-00114

V-domain Immunoglobulin Suppressor of T cell Activation (VISTA/PD-1H) is an immune checkpoint regulator of the B7 family. VISTA can be found on the cell surface of some tumor types, however for the majority of cancers, VISTA is highly expressed in the immunological myeloid cell compartment in the tumor microenvironment (TME). VISTA has been shown, in vitro and in vivo, to inhibit T cell activation and prevent T cell recruitment into tumors. In patients, high VISTA expression is associated with poor prognosis and is also a potential mediator of resistance to anti-CTLA-4 and anti-PD-(L)1 therapies. Therefore, VISTA is a very attractive new target for cancer immunotherapy. Kineta has selected a lead candidate anti-VISTA monoclonal antibody after a deep screen of 107 fully human and highly diverse antibodies directed against the VISTA extracellular domain. The candidate exhibits high potency in the subnanomolar range and is characterized by a long constant of dissociation evaluated by ELISA and Octet binding. It targets human and cynomolgus monkey VISTA on a unique epitope. Cross reactivity against other B7 family members has also been evaluated, and the lead candidate demonstrates high specificity against VISTA. The candidate antibody also efficiently induces T cell activation, proliferation and IFNg secretion on a Staphylococcal EnterotoxinB assay, as well as in a coculture experiment with a cell line overexpressing VISTA. The candidate promotes maturation of Antigen Presenting Cells with an increase of CD80 and HLA-DR surface expression as well as CXCL10 secretion in a monocyte activation assay. The mechanism of action is mediated in part by NK cells. This anti-VISTA antibody also prevents the immunosuppressive function of differentiated MDSCs in vitro against T cells. In Knock-In-human VISTA mice, anti-VISTA antibody treatment mediates single-agent antitumor activity in vivo in multiple syngeneic tumor models and shows enhanced efficacy in combination with either anti-PD-(L)1 or anti-CTLA-4 treatment. Finally, anti-VISTA antibody treatment was well-tolerated in exploratory toxicology studies in cynomolgus monkey and has a half-life consistent with other monoclonal antibodies. Our results strongly support the continued development of our anti-VISTA antibody for the treatment of colder, less immunogenic tumors. Citation Format: Thierry Guillaudeux, Eric Tarcha, Robert Bader, Benjamin Dutzar, Nathan Eyde, Emily Frazier, David Jurchen, Remington Lance, Cristina Loomis, Kurt Lustig, Yulia Ovechkina, David Peckham, Jeff Posakony, Shaarwari Sridhar, Mei Xu, Shawn Iadonato. A fully human anti-vista antibody as a promising therapy against poorly immunogenic tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1637.

V-domain Immunoglobulin Suppressor of T cell Activation (VISTA/PD-1H) is a B7 family ligand expressed on circulating and intratumoural myeloid cells as well as Treg and NK cells. It has been shown to inhibit T cell responses in vitro and in preclinical models. In patients, VISTA is also a potential mediator of resistance to anti-CTLA-4 and anti-PD1 therapies and therefore is a valuable new target for cancer immunotherapy. Kineta has analyzed 107 fully human ScFv antibodies directed against VISTA. Our lead candidates exhibit high potencies in the subnanomolar range and are also characterized by a long kDis. They specifically target human and cynomolgus monkey VISTA on a singular unique epitope. In a Staphylococcus Enterotoxin B T-cell activation assay, Kineta’s anti-VISTA antibodies efficiently induce IFNg secretion. They also promote strong maturation of Antigen Presenting Cells with an increase of CD80 and HLA-DR surface expression as well as CXCL10 secretion. The mechanism of action is mediated in part by NK cells. We demonstrated that myeloid cells acquire a high level of VISTA expression during MDSC or M2 differentiation in vitro and that Kineta’s anti-VISTA antibodies prevent the differentiation of MDSC as well as their immunosuppressive activity against T cells. Anti-VISTA antibodies mediate single-agent antitumor effects in syngeneic tumor models in wild-type mice and show enhanced activity in combination with anti-PD1 and anti-CTLA-4 treatment. Candidate anti-VISTA antibodies have also been evaluated in exploratory tolerability and PK studies in cynomolgus monkey. These studies demonstrated that multiple weekly doses of antibodies are well-tolerated with appropriate PK for lead selection and optimization. Our results strongly favor further characterization and continued development of selected lead antibodies for the potential treatment of colder, less immunogenic tumors. This abstract is also being presented as PO035. Citation Format: Thierry Guillaudeux, Eric Tarcha, Robert Bader, Benjamin Dutzar, Nathan Eyde, Emily Frazier, David Jurchen, Remington Lance, Cristina Loomis, Kurt Lustig, Yulia Ovechkina, David Peckham, Jeff Posakony, Shaarwari Sridhar, Mei Xu, Shawn Iadonato. Highly potent fully human anti-VISTA antibodies – A new target checkpoint inhibitor against immunosuppressive myeloid cells [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PR005.