Abstract 4487: Association of the tumor-immune microenvironment with response to niraparib and pembrolizumab in relapsed, platinum-resistant ovarian cancer

Introduction: TOPACIO/Keynote-162 is a multi-center, open-label, single-arm phase 1/2 trial of Poly-ADP Ribose Polymerase (PARP) inhibitor niraparib combined with an anti-PD-1 antibody pembrolizumab. One cohort enrolled patients with recurrent ovarian cancer (OC). As tumor BRCA1/2 mutation (tBRCA), Homologous Recombination Deficiency (HRD) test (Myriad), or PD-L1 testing by immunohistochemistry were unable to predict clinical responses, we set out to examine additional DNA repair and immune biomarkers for response. Methods: We analyzed pre-trial Formalin Fixed Paraffin Embedded (FFPE) tumor samples from 49 patients with recurrent OC. The samples were collected either at diagnosis, or a median of 4.3 months (range 1.5 - 91.1) after the diagnosis. The median time from diagnosis to trial entry was 35.8 months (range 11.4 - 136.5). To further assess HRD we performed BROCA sequencing of 69 DNA repair genes as previously reported. NanoString gene expression analysis was performed using an IO360 panel complemented with 30 DNA repair genes and analyzed with the NSolver software. Findings were correlated with clinical response evaluated based on RECIST v1.1. Results: Overall, the confirmed objective response (OR) rate was 18% with a clinical benefit (complete response + partial response + stable disease; CB) rate of 65%. HRD as assessed by BROCA sequencing did not associate with OR or CB. In the Nanostring mRNA expression analyses, the samples taken at the time of diagnosis (n=23) had significantly lower abundance score for several immune cell lineages, including cytotoxic cells, macrophages, dendritic cells, and NK-cells compared to samples collected after the diagnosis. In addition, in the at-diagnosis samples, lower abundance scores for overall immune cells (CD45), tumor-infiltrating lymphocytes, CD8+T-cells, and macrophages were associated with clinical benefit. Pathway analysis demonstrated that increased scores for Cytosolic DNA sensing- and interferon pathways significantly correlated with OR, particularly in the platinum-resistant patients. In contrast, the samples collected after diagnosis (n=21), had increased mRNA expression levels of PD-L1, PD-L2 and PD-1, and a higher score for exhausted CD8+ T-cells than the samples collected at diagnosis. In these samples, a low exhausted CD8+T cell/T-regulatory cell score ratio was associated with OR. Conclusions: Increased interferon signaling, and exhausted T/regulatory T-cell ratio are associated with response to the combination of niraparib and pembrolizumab. We are in the process of performing further profiling of the tumor microenviroment with a highly multiplexed tissue immunofluorescence (tCycIF) providing a comprehensive analysis of cell types, functional states, and spatial interactions at single-cell resolution. Citation Format: Anniina Farkkila, Jia R. Lin, Julia Casado, Huy Nguyen, Yinghui Zhou, Julie R. Graham, Bruce J. Dezube, Steven Waggoner, Pamela Munster, Gini F. Fleming, Sandro Santagata, Ursula A. Matulonis, Peter K. Sorger, Elizabeth M. Swisher, Alan D. D’Andrea, Panagiotis Konstantinopoulos. Association of the tumor-immune microenvironment with response to niraparib and pembrolizumab in relapsed, platinum-resistant ovarian cancer [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 4487.