Abstract 1148: SynOV1.1: A synthetic gene circuit controlled oncolytic adenovirus demonstrating high tumor specificity, potent antitumor efficacy and high synergy with an anti-PD-L1 monoclonal antibody in preclinical hepatocellular carcinoma models

Abstract

Hepatocellular carcinoma (HCC) is yet the fourth most common cause of cancer-related death although its treatment has been significantly advanced in recent years. Oncolytic viruses are among a novel class of immunotherapies that have shown promise to HCC patients with convincing abilities to selectively replicate in and kill cancer cells as well as to boost tumor immunogenicity. In order to further enhance the safety and efficacy of oncolytic viruses, SynOV1.1, a recombinant replication-competent serotype 5-based adenovirus, was constructed by deleting E1B and partial E3 genes, and incorporating a synthetic sensory switch circuit. The gene circuit was designed to enhance tumor-specific expression of E1A gene and an immune effector, human granulocyte-macrophage colony-stimulating factor (hGM-CSF) by sensing cancer-specific alpha-fetoprotein (AFP) promoter and two microRNA inputs. The specificity of SynOV1.1 to selectively kill target tumor cells and the ability to specifically express hGM-CSF in the target cells were confirmed in numerous human and mouse HCC cell lines with an IC50 approximately 3 to 35-fold less than that of normal cell lines. In vivo, intratumoral injections of SynOV1.1 in immune-deficient mice bearing human HCC cells resulted in a significant reduction of tumor volume (approximately 80%) as compared with the controls (approximately 30% for sorafenib). To further evaluate the effects of antitumor and immune stimulation, SynOV1.1m (SynOV1.1 murine surrogate) was intratumorally injected to the immune-competent mice bearing mouse HCC cells (ie., mHepa1-6), which showed SynOV1.1m induced a greater antitumor effect as well as a more robust tumor-specific immune response as compared to the controls. In addition, SynOV1.1m could significantly inhibit the growth of non-injected distal tumors after it was injected into a mHepa1-6 tumor on the other side of the mouse body, indicating that a systemic immune response was induced by SynOV1.1m. The combination of SynOV1.1m and an anti-mPD-L1 monoclonal antibody (mAb) was further explored and showed a synergistic anti-tumor effect as compared to SynOV1.1m or anti-mPD-L1 mAb alone. Preclinical safety of SynOV1.1 was examined in various toxicology species including golden hamsters, tumor-bearing mice and cynomolgus monkey, in all of which SynOV1.1 was found safe. Overall, preclinical pharmacology and toxicology data support clinical investigation of SynOV1.1 alone or in combination with atezolizumab in advanced HCC patients with positive serum AFP levels. Citation Format: Qiang Liu, Yubing Cao, Man Zhang, Shuguang Peng, Yiqi Liu, Huiya Huang, Bin Chen. SynOV1.1: A synthetic gene circuit controlled oncolytic adenovirus demonstrating high tumor specificity, potent antitumor efficacy and high synergy with an anti-PD-L1 monoclonal antibody in preclinical hepatocellular carcinoma models [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 1148.