Immune characterization in platinum resistant ovarian cancer patients treated with pembrolizumab and guadecitabine

Abstract

Abstract Immune checkpoint inhibitors (ICI) have limited activity in ovarian cancer (OC). Accumulating preclinical and early clinical results support that interventions targeting the epigenome could elicit an inflamed tumor milieu to augment ICI. Here we explore the clinical and biological activity of guadecitabine, a second generation Hypomethylating agents (HMA), given in low dose as a priming strategy before pembrolizumab, a humanized anti-PD1 antibody in a clinical trial for patients with recurrent, platinum-resistant OC. Among 35 evaluable patients, there were 3 partial responses (8.6%) and 8 (22.9%) patients with stable disease, resulting in clinical benefit rate (CBR) of 31.4%. Median duration of clinical benefit was 6.8 months. High dimensional immune profiling of PBMCs showed higher frequency of naive and/or central memory CD4+ T cells and of classical monocytes in patients with durable CBR. Higher baseline density of CD8+ T and CD20+ B cells and presence of tertiary lymphoid structures in tumors were associated with durable CBR. The molecular features such as expression levels of PD-L1 or A2AR linked to therapeutic benefit for resistant OC. Our study provides an in-depth view of the immune milieu of platinum resistant OC and of the effects of the combination of HMAs and pembrolizumab on the interactions between immune cell populations and tumor cells. Supported by USAMRMC/CDMRP (W81XWH170141)