Abstract A76: Immunologic changes following intraperitoneal administration of a formulated IL-12 plasmid in combination with standard neoadjuvant chemo in newly diagnosed advanced stage ovarian cancer patients

Background: This abstract describes the translational component of a phase I study of weekly intraperitoneal (IP) GEN-1, an IL-12 plasmid formulated with polyethyleneglycol-polyethyleneimine cholesterol lipopolymer, in combination with standard intravenous (IV) weekly taxane (T) and carboplatinum (C) every 3 weeks in epithelial ovarian, fallopian tube, or primary peritoneal cancer (EOC) patients undergoing neoadjuvant chemotherapy (NAC). Local administration of GEN-1 could provide persistent IL-12 secretion to induce type-1 immune responses in the immunosuppressive tumor microenvironment. Our hypothesis is that the GEN-1 plus NAC treatment will reprogram the tumor immune microenvironment towards a potent antitumor immune response. We have previously reported the clinical finding that GEN-1 is safe up to 79 mg/m2 IP weekly up to eight treatments. The most common related toxicities were Grade 1 nausea, vomiting, abdominal pain, and fatigue. Patients continue to be followed for progression and any drug-related safety events. Methods: Newly diagnosed advanced-stage EOC patients being treated with NAC were eligible. The trial utilized a 3+3 design with GEN-1 IP dose levels ranging from 36 mg/m 2 to 79 mg/m 2 weekly for 8 treatments with concurrent IV T/C. Tumor samples were collected at time of diagnostic laparoscopy and interval debulking (IDB). Blood and peritoneal ascites were collected before and after treatment. The immunologic analysis included frequency of immune cell populations and cytokine levels in tumor, blood, or peritoneal ascites. The levels of cytokines IL-12, IFN-γ, TNF-α, TGF-β, IL-10, and VEGF were quantified in blood plasma and ascites samples with commercially available cytokine-specific ELISA kits. The tumor tissue specimens were paraffin embedded and serial sections were stained with specific antibodies for various T-cell markers using immunohistochemistry. The density of various T-cells, dendritic cells, and myeloid-derived suppressor cells in blood or ascites was determined by flow cytometry. Results: The interim results obtained from Cohorts 1–4 (stage 1) show post-treatment changes in immune cell populations, including an increase in cytotoxic CD8+ T-cells and decrease in several immunosuppressive markers including FoxP3+, PD-1, PDL-1, and IDO-1. The cell ratio of CD8+ to all immunosuppressive markers appeared to be skewing beneficially towards more cytotoxic T lymphocyte and away from suppressive cells in most patients. There were no significant changes in the frequency of circulating T cells (or cytokine response). Analysis of ascites before and 24 hours after IP administration of GEN-1+NAC showed evidence of IL-12 gene transfer and activation of downstream signaling pathways, including increases in IFN-γ levels and inhibition of peritoneal VEGF levels. The cytokine response was predominantly in ascites while comparatively little changes were observed in blood plasma. Thus, the immunomodulatory and therapeutic effect of GEN-1 treatment is primarily localized within the tumor microenvironment and does not appear to have any untoward effect on systemic immune responses. The changes in cytokine levels appeared to be GEN-1 dose dependent. Additional analyses from this study are in progress. Conclusions : Adding GEN-1 to neoadjuvant T/C is safe and biologically active in EOC patients. Based on preliminary analyses of Cohorts 1–4 (stage 1), the treatment of EOC patients with GEN-1 and NAC has resulted in favorable immunologic responses. Final translational results will be presented at the meeting. Clinical trial information: NCT02480374. Citation Format: Khursheed Anwer, Junko Matsuzaki, Wiam Bshara, Amit Lugade, Angela Omilian, Premal H. Thaker, William H. Bradley, Rebecca Arend, Camille Gunderson, Jason Fewell, Nicholas Borys, Lauren Musso, Adekunle Odunsi. Immunologic changes following intraperitoneal administration of a formulated IL-12 plasmid in combination with standard neoadjuvant chemo in newly diagnosed advanced stage ovarian cancer patients. [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr A76.