Abstract 7551: Combined epigenetic therapy and immune checkpoint blockade drive reshaping of the tumor microenvironment of platinum resistant ovarian cancer

Abstract Introduction: Immunotherapy has demonstrated modest effectiveness for patients with platinum-resistant ovarian cancer, which is in part related to the immunosuppressive tumor microenvironment (TME) of ovarian cancers. Epigenetic modulators in combination with immune checkpoint inhibitors (ICIs) may represent a potential way to sensitize ovarian cancer to immunotherapy by TME reprogramming. Methods: We evaluated the effect of epigenetic modulation in combination with ICI by comprehensive transcriptomic analyses of serially biopsied platinum-resistant/refractory ovarian cancer. Leveraging serial tumor samples from 30 patients that received oral azacitidine and pembrolizumab in the TRIO026 phase II clinical trial (NCT02900560), we performed bulk RNA sequencing and direct digital counting of 770 target genes using molecular barcodes (nCounter, NanoString) for 72 serial tumor samples, prior to treatment initiation and 6 weeks on-therapy. RNA sequencing of ~200 million reads for each sample was used for differential gene expression and gene set enrichment analysis (GSEA) and cell type deconvolution. Target gene expression data was normalized and analyzed for differential gene and pathway expression. Results: Differential gene expression analyses revealed an upregulation of inflammatory and cytolytic genes (IFNG, GZMA and GZMH; FDR-adjusted p=0.0184) as well as the co-inhibitory molecule CTLA-4 (FDR-adjusted p=0.0184). GSEA revealed an enrichment of IFNG response, natural killer cell mediated cytotoxicity, neutrophil degranulation, inflammatory response, and antigen processing/presentation related gene sets on-therapy (FDR-adjusted p < 0.001). Target gene expression analyses orthogonally confirmed these findings, which were also concordant with pathway scoring analyses showing an increased score for immune inflammatory pathways such as INFG signaling (Wilcoxon rank sum test p=0.01). Immune cell subset deconvolution suggested TME reshaping driven by a greater density of intra-tumoral T cells on-therapy (Wilcoxon rank sum test p=0.012). Higher IFNG, CXCL13, CXCR5 expression, CD8 T cell and NK cell density were associated with longer time on treatment, both at baseline and at the on-therapy timepoint. GSEA revealed an upregulation of interferon gamma, adaptive immunity, antigen presentation as well as conserved immune response gene sets on-therapy, for the patients attaining longer time on-treatment. Conclusion: Combination epigenetic and immunotherapy induces an inflammatory response and reshaping of the tumor microenvironment that may enhance their clinical efficacy, highlighting the therapeutic potential of utilizing epigenetic modulators as a way to sensitize platinum-resistant ovarian cancer to immune checkpoint inhibition. Citation Format: Blair V. Landon, Guneet Kaleka, Archana Balan, Julia L. Boland, Christopher Cherry, Gavin Pereira, Cynthia Zahnow, Boris Winterhoff, Stephen Baylin, Victor E. Velculescu, Gottfried E. Konecny, John A. Glaspy, Valsamo Anagnostou. Combined epigenetic therapy and immune checkpoint blockade drive reshaping of the tumor microenvironment of platinum resistant ovarian cancer [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(6_Suppl):Abstract nr 7551.