Abstract 5278: Immunological control by PARP inhibitors for successful immunotherapy in metastatic ovarian carcinoma

Abstract Epithelial ovarian carcinoma (EOC) is among the top five causes of cancer-related death in women. Most women with EOC achieve indeed complete remission after primary or interval cytoreductive surgery combined with chemotherapy based on a platinum-taxane doublet. Homologous recombination (HR) defects imposed by germline or somatic BRCA1 DNA repair-associated (BRCA1) or BRCA2 mutations are not only key determinants of platinum sensitivity in EOC patients but also provide a strong rationale for maintenance therapy based on poly (ADP-ribose) polymerase (PARP) inhibitors, which is generally associated with improved progression-free survival (PFS). Besides direct cytotoxic and cytostatic properties, PARPi have been shown to mediate multipronged immunostimulatory effects, largely reflecting their ability to inhibit DNA repair in malignant cells and indicating the possibility to synergy with immune-check point inhibitors (ICIs). Here, using multiparametric flow cytometry, multiplex immunostaining, single cells transcriptomics and functional studies in experimental syngeneic BR5Brca1-/- mouse model and EOC tumor samples, we discuss PARPi immunomodulatory activity, with a specific focus on molecular and cellular pathways that can be harnessed to develop superior combinatorial regimens for clinical management. Thus, PARPi might enhance the mutational load of EOCs as consequence of unrepaired DNA damage and DAMPs exposure, favoring T cell infiltration, but also appear to drive robust type I IFN secretion downstream of cyclic GMP-AMP synthase and stimulator of IFN response cGAMP interactor 1 activation. In addition, the combination of PARPi with ICIs positively regulate the balance between adaptive anti-tumor immunity and innate myeloid components and significantly improve the cytotoxic T cell profile as shown in both experimental mice model and HGSOC tumor samples. We surmise that rationally designed combinations of PARPi and immunotherapeutic agents might be critical to unlock immunosuppression in the EOC microenvironment in support of clinical efficacy. Citation Format: Peter Holicek, Sarka Vosahlikova, Irena Moserova, Sandra Orsulic, Romana Mikyskova, Michal Hensler, Lenka Kasikova, Tereza Lanickova, Ondrej Novotny, Milan Reinis, Jana Drozenova, Ales Ryska, Jan Laco, Lukas Rob, Michael Halaska, David Cibula, Radek Spisek, Jitka Fucikova. Immunological control by PARP inhibitors for successful immunotherapy in metastatic ovarian carcinoma abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 5278.