Wee1 inhibition has received great attention in the past decade as a promising therapy for cancer treatment. Therefore, a potent and selective Wee1 inhibitor is highly desirable. Our efforts to make safer and more efficacious Wee1 inhibitors led to the discovery of compound 16, a highly selective Wee1 inhibitor with balanced potency, ADME, and pharmacokinetic properties. The chiral ethyl moiety of compound 16 provided an unexpected improvement of Wee1 potency. Compound 16, known as ZN-c3, showed excellent in vivo efficacy and is currently being evaluated in phase 2 clinical trials.

Introducing a uniquely substituted phenyl sulfone into a series of biphenyl imidazole liver X receptor (LXR) agonists afforded a dramatic potency improvement for induction of ATP binding cassette transporters, ABCA1 and ABCG1, in human whole blood. The agonist series demonstrated robust LXRβ activity (>70%) with low partial LXRα agonist activity (<25%) in cell assays, providing a window between desired blood cell ABCG1 gene induction in cynomolgus monkeys and modest elevation of plasma triglycerides for agonist . The addition of polarity to the phenyl sulfone also reduced binding to the plasma protein, human α-1-acid glycoprotein. Agonist was selected for clinical development based on the favorable combination of properties, excellent pharmacokinetic parameters, and a favorable lipid profile.

Genome instability initiated by DNA damage or DNA replication stress is a driver of tumor development. To ensure the accuracy of DNA replication, DNA damage response (DDR) mediated by various cell cycle checkpoints activate the DNA repair system. One such checkpoint system is the G2-M checkpoint which is involved in the repair and prevention of excessive DNA damage. A key regulator of the G2-M checkpoint is the Wee1 kinase which causes cell cycle arrest to prevent damaged cells from entering mitosis. Thus, inhibition of Wee1 should prevent G2-M checkpoint activation which would lead to unscheduled mitotic entry and induction of apoptosis. Small-molecule inhibitors of Wee1 are currently being tested in several tumor types. Preliminary results show promising clinical activity of AZD-1775, a potent inhibitor of Wee1, however, achieving an optimal dose and a schedule that is well-tolerated has been a challenge. Here, we describe the characterization of ZN-c3, a potent, selective and orally bioavailable small-molecule inhibitor of Wee1. ZN-c3 exhibits potent anti-proliferative activity across multiple tumor cell lines. Compared to AZD-1775, ZN-c3 has superior selectivity profile against a panel of kinases. In vivo, ZN-c3 induced tumor regression as a single agent in several tumor models including non-small cell lung cancer, ovarian cancer, and uterine sarcoma. In combination studies, ZN-c3 potentiates the antitumor efficacies of carboplatin and gemcitabine. The pharmacokinetic and efficacy profiles of ZN-c3 and AZD-1775 were compared in tumor xenograft models. ZN-c3 showed higher plasma and tumor exposure than AZD-1775, which correlated with more potent tumor growth inhibition than AZD-1775. In summary, ZN-c3, with its key differentiated pharmacologic and kinase selectivity profile, is a promising new generation of DDR inhibitor. ZN-c3 is currently in clinical development for the treatment of advanced solid cancers. Citation Format: Jiali Li, Brant Boren, Peter Q. Huang, Kevin D. Bunker, Fernando Doñate, Ahmed A. Samatar. Discovery of ZN-c3, a potent Wee-1 inhibitor with a differentiated pharmacologic and kinase selectivity profile [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1965.