Abstract 5003: Vaccibody DNA vaccine platform VB10.NEO induces strong neo-antigen specific CD8+ T cell responses critical to cure established tumors in pre-clinical models

BACKGROUND: Recent advances in the field of cancer immunotherapy have identified CD8+ T cell responses against tumor-specific neoantigens as a key driver of tumor regression and prolonged survival. VB10.NEO is a highly potent DNA plasmid vaccine with intrinsic adjuvant effect designed for efficient delivery of personalized tumor-specific neoantigens. VB10.NEO plasmid is translated in vivo and the secreted protein will covalently bind to endocytic receptors on APC by a targeting unit expressing CCL3 (MIP-1α) allowing efficient uptake and presentation of the neoantigens. In addition, CCL3 will attract immune cells by chemotaxis and induce maturation of APC locally. The objective of this study is to demonstrate the potential of VB10.NEO to induce tumor-specific T cell responses and control tumor growth.

METHODS: VB10.NEO was delivered i.m to study CD8+ and CD4+ neoantigen-specific T cell responses in four different pre-clinical mouse models. Immunogenicity was compared with delivery of neoantigen as traditional peptide-adjuvant immunization. The tumor protective effect of VB10.NEO in the presence or absence of anti-PD-1 therapy was investigated in the CT26 colon carcinoma model.

RESULTS: Vaccibody DNA Vaccine Platform VB10.NEO is flexible and can hold up to at least 40 neoepitopes. VB10.NEO vaccination induced strong neoantigen-specific T cell responses. Homologous boost vaccinations further augmented the response. T cell responses against predicted CD8+ T cell epitopes previously reported as non-immunogenic or activating only weak T cell responses using a conventional peptide-adjuvant or RNA immunization showed strong CD8+ T cell responses when delivered in the Vaccibody format, demonstrating a unique and strong priming of CD8+ T cells using VB10.NEO. The response was also accompanied by CD4+ T cell responses. In a therapeutic tumor setting VB10.NEO vaccinated mice (monotherapy) induced tumor protective responses. The effect was augmented when combining VB10.NEO with anti-PD-1 where complete regression of large established tumors was observed. All tumour-free mice rechallenged with a lethal tumor dose were protected indicating induction of long-lasting memory responses. Furthermore, the critical role of CD8+ T cells for the observed tumour protection was confirmed when depleting CD8+ T cells.

CONCLUSION: VB10.NEO immunotherapy induce strong CD8+ T cell responses critical for anti-tumor effect which demonstrate the unique characteristic of the Vaccibody platform to potentiate activation of CD8+ T cells. VB10.NEO in combination with anti-PD-1 further synergize the potent immune responses resulting in durable complete tumor regression in pre-clinical models supporting the scientific rational for the current ongoing clinical trial investigating VB10.NEO in combination with CPI in patients with advanced solid tumors.

Citation Format: Elisabeth Stubsrud, Stine Granum, Helene Zell-Flagstad, Audun Bersaas, Lise Madelene Skullerud, Monika Sekelja, Karoline Schjetne, Agnete Fredriksen. Vaccibody DNA vaccine platform VB10.NEO induces strong neo-antigen specific CD8+ T cell responses critical to cure established tumors in pre-clinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5003.

Abstract 2256: Combination of neoantigen DNA plasmid vaccine VB10.NEO and NKTR-214, a CD122-biased immunostimulatory cytokine, induces strong neoantigen-specific T cell responses and sustained tumor regression in pre-clinical models

BACKGROUND: VB10.NEO is a highly potent DNA plasmid vaccine with intrinsic adjuvant effect designed for efficient delivery of personalized neoepitopes and is currently being tested in combination with CPI in patients with advanced solid tumors. NKTR-214, a CD122-biased agonist that targets the IL-2 pathway, provides sustained signaling through the heterodimeric IL-2 receptor pathway (IL-2Rβγ) to preferentially activate and expand NK and effector CD8+ T cells over T-regulatory cells, and is currently in multiple phase I, II and III clinical trials in combination with nivolumab. Here we explored the combination of VB10.NEO with NKTR-214 in the presence or absence of anti-PD-1 therapy in different pre-clinical syngeneic tumor models.

METHODS: Mice were vaccinated with VB10.NEO (i.m.), NKTR-214 (i.v) and anti-PD-1 (i.p.) at different intervals to study efficacy and optimal dosing schedule before spleens were harvested to analyze CD8+ and CD4+ neoantigen-specific T cell responses in IFN-γ ELISpot in two different tumor models (B16 and CT26). The tumor protective effect of the combination therapy of VB10.NEO with NKTR-214 in the presence or absence of anti-PD-1 therapy was investigated in CT26 colon carcinoma model.

RESULTS: Combination of VB10.NEO and NKTR-214 greatly synergizes, resulting in 5-fold increase in the number of neoantigen-specific T cell responses compared to VB10.NEO alone. Dosing of VB10.NEO vaccination relative to NKTR-214 administration was found to impact the extent of the synergetic activity. Mice treated with VB10.NEO containing 10 neoepitopes from B16 in combination with NKTR-214 showed both a stronger response to each neoantigen, but also to increased numbers of neoantigens, showing that both the breadth and depth of the immune response were elevated. The VB10.NEO and NKTR-214 combination showed an even more evident effect on CD8+ T cell responses as the combination elicited a neoantigen-specific CD8+ T cell response against 10 neoantigens compared to 5 neoantigens with VB10.NEO alone, further strengthening the combination’s ability to induce strong neoantigen-specific CD8+ T cell responses. In the therapeutic tumor model, increased number of complete responders was observed in mice treated with the triple combination of vaccine, NKTR-214 and CPI demonstrating the strong rational for bringing together these unique and non-overlapping mechanisms that create an effective treatment of established tumors.

CONCLUSION: VB10.NEO in combination with NKTR-214 with or without anti-PD-1 therapy synergizes to elicit greater breadth and depth of neoantigen-specific T cell responses and provide durable complete tumor regression in pre-clinical models supporting the rationale for examining the combination clinically.

Citation Format: Stine Granum, Helene Zell-Flagstad, Audun Bersaas, Lise Skullerud, Elisabeth Müller, Mads Axelsen, Karoline Schjetne, Jonathan Zalevsky, Agnete Fredriksen. Combination of neoantigen DNA plasmid vaccine VB10.NEO and NKTR-214, a CD122-biased immunostimulatory cytokine, induces strong neoantigen-specific T cell responses and sustained tumor regression in pre-clinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2256.