Abstract 1453: Development of a novel PD-1 vaccine and in combination with two Chimeric HER-2 peptide vaccine provides synergistic inhibition of tumor growth in a syngeneic Balb/c model challenged with CT26/HER-2 carcinoma cell line

Background: Therapeutic blockade of the signaling axis between PD-1 and its ligand programmed cell death ligand-1 (PD-L1) with monoclonal antibodies has shown remarkable clinical success in the treatment of cancer and demonstrated impressive activity across a broad set of cancer subtypes, even at advanced and metastatic stages of disease. Contrary to treatment with monoclonal antibodies, chimeric B-cell cancer vaccines have the advantage of producing a specific immune response that can potentially induce memory B & T cell responses, while reducing immune evasion and suppression. Methods: We have translated two HER-2 combination peptide vaccines (B-Vaxx) to the clinic in a Phase 1/2b trial to safely deliver curative and transformative cancer immunotherapies to advanced cancer patients. We have created and established the development of a novel B-cell peptide vaccine (Key-Vaxx) with high immunogenicity that binds to human PD-1 and produces tumor inhibition in vivo in an animal model of colon cancer. Here, we describe the transferable CT-26-HER2 neu tumor model in Balb/c was used to test for synergistic effects of anti-PD1 immunization therapy in combination with anti-HER2 immunization therapy to determine whether this combination could increase immunogenicity, enhance anti-tumor responses and provide synergistic benefit in inhibiting tumor growth. Results: We show robust HER-2 and PD-1 antibody responses in all vaccinated mice indicating that the combined vaccination is effective in reducing tumor growth in a Balb/c syngeneic model of colon carcinoma versus either the PD-1 vaccine or more importantly the positive control gold standard that is anti-mouse PD-1 monoclonal antibody. The vaccine combination was found to be safe and did not appear to exhibit toxicity or autoimmunity. Conclusion: Development of a novel PD-1 vaccine in combination with two Chimeric HER-2 peptide vaccine provides synergistic inhibition of tumor growth with no evidence of toxicity or autoimmunity. A clinical trial with the combination is under planning. Citation Format: Tanios Bekaii-Saab, Jay Overholser, Yuhong Yang, Manuel Penichet, Pravin Kaumaya. Development of a novel PD-1 vaccine and in combination with two Chimeric HER-2 peptide vaccine provides synergistic inhibition of tumor growth in a syngeneic Balb/c model challenged with CT26/HER-2 carcinoma cell line [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 1453.