Insights from basic science dissecting carcinogenesis in the fallopian tube and ovary have led to a deeper understanding of the origin, molecular characteristics, and types of ovarian cancers. This logically then has led to the development of novel approaches to treat ovarian cancer. Increasingly, novel agents are being developed to target the different growth pathways. The identification of molecular markers associated with different histopathologies has resulted in newer clinical trial designs to capture both clinical and translational endpoints. Unique molecular characteristics in DNA damage and repair pathways and unique cell surface markers have driven new drug development, yielding promise for both patients with platinum-sensitive and platinum-resistant ovarian cancers. Specific examples described include the histology-selective mutations, such as ARID1A in clear cell and endometrioid ovarian cancers; the rationale for using cell cycle checkpoint inhibitors when there already is a p53-mediated loss of cell cycle checkpoint regulation or combinations of agents that will both induce neoantigen formation and unleash immune modulators; and techniques to enhance the therapeutic delivery of known agents. A systematic and thoughtful approach to combining agents in clinical trials is needed so that irrespective of the trial outcomes, the results inform both clinical and translational endpoints.

Background Inhibitors of Apoptosis Proteins (IAPs) are key regulators of apoptosis, and are frequently dysregulated in ovarian cancer. We hypothesized that blocking IAPs with birinapant would increase tumor cell death resulting in objective response for women with platinum-refractory and resistant ovarian cancer. Methods In this phase II CTEP-sponsored study, patients received birinapant 47mg/m2 on days 1, 8, 15 of 28-day cycles. Pharmacokinetics were obtained in cycle 1. Plasma, peripheral blood mononuclear cells (PBMC) and percutaneous tumor biopsies were collected prior to cycle 1, and after 6 weeks. The primary endpoint was objective response or progression-free survival lasting greater than 6 months in a mini-max design. Results Eleven patients received birinapant, after which accrual was terminated for lack of clinical benefit. Birinapant was well-tolerated, with predominantly grade 2 adverse events (AE) and one grade 3 lymphopenia. Pre-treatment biopsies and PBMCs were collected; paired post-treatment biopsies and PBMC were collected from 7 and 10 patients, respectively. There was consistent downregulation of cIAP1 in tumor (P=0.016) and PBMC (P<0.01). Pro-caspase3 also decreased in tumors (P=0.031) and PBMC (P<0.01); cleaved caspase3 co-localized with gamma-H2AX in tumors after birinapant exposure. Peripheral T- and B-cells decreased significantly post-treatment, but NK-cells did not (P=0.04, P=0.05, P=0.43 respectively). Conclusion Birinapant shows consistent target suppression in vivo, without single agent anti-tumor activity in this small population. Single agent pharmacodynamics were necessary to understand drug mechanism of action and set the stage for rational combination therapy. Preclinical studies are ongoing to identify optimal synergistic combinations for future clinical trials.

• Monotherapy with prexasertib demonstrated modest activity in BRCA wild-type, recurrent triple-negative breast cancer, highlighting the unmet need for combination treatment strategies. • Neutropenia, anemia, and thrombocytopenia are common with the use of prexasertib but are manageable with supportive care measures. Prophylactic use of granulocyte colony stimulating factor should be considered to avoid dose reductions or treatment delays. • Pharmacodynamic studies showed prexasertib treatment induced DNA damage in peripheral immune cells.