Background: Ovarian, peritoneal, and fallopian tube cancer are deadly diseases with similar pathological and clinical features. Despite initial therapy with cytoreductive surgery and platinum-based therapy, many patients experience disease relapse either during (refractory) or within 6 months after (resistant) first-line platinum-based therapy. In these patients, various chemotherapies offer clinical activity but none is universally preferred. WEE1 tyrosine kinase is a critical component of G2/M cell cycle checkpoint control and mediates cell cycle arrest by regulating the phosphorylation of cyclin-dependent kinase 1 (CDK1). Inhibition of WEE1 leads to premature mitotic entry, DNA damage and apoptosis induction, and cell death. ZN-c3 is a novel, selective, and orally bioavailable WEE1 inhibitor that has demonstrated significant antitumor activity in nonclinical in vitro and in vivo models. A first-in-human study identified the maximum tolerated dose (MTD) of ZN-c3 when given as monotherapy.Combining ZN-c3 with chemotherapy may inhibit repair of chemotherapy-induced DNA damage and provide therapeutic benefit in this population.Trial design: This phase 1b, open-label, multicenter study is evaluating the safety, pharmacokinetics, pharmacodynamics, and anti-tumor activity of ZN-c3 in combination with pegylated liposomal doxorubicin, carboplatin, paclitaxel, or gemcitabine. The primary objectives are to determine MTDs and recommended phase 2 doses for each combination by a modified Bayesian continual reassessment method. Subjects are adult women with high-grade serous epithelial ovarian, peritoneal, or fallopian tube carcinoma who have received 1 or 2 prior chemotherapy regimens including platinum-based therapy and are refractory or resistant to platinum-based therapy. Study drug therapy is given in repeated 21-or 28-day cycles until disease progression or unacceptable toxicity. ZN-c3 is taken orally once daily. Chemotherapy is administered per protocol. Pharmacodynamic effects of therapy in tumor tissue and hair follicle samples will be explored. Subject recruitment is ongoing.