Wee1 is a tyrosine kinase that phosphorylates cyclin-dependent kinase 1 (CDK1/CDC2) to inactive the CDC2/cyclinB complex. Wee1 is therefore a key regulator of the cell cycle, maintaining the G2 checkpoint arrest to allow for premitotic repair in case of DNA damage. Unlike normal cells, most p53-deficient tumors lack a functional G1 checkpoint and instead rely on the G2 checkpoint for DNA repair. Abrogation of the G2 checkpoint by a Wee1 inhibitor may therefore sensitize p53-deficient tumors to DNA-damaging anticancer agents and enhance their cytotoxic effect. Strong evidence for chemo-sensitization has been demonstrated from multiple pre-clinical models and also from clinical trials. In particular, treatment in combination with carboplatin recently showed encouraging antitumor activity in patients with p53-mutated ovarian cancer refractory or resistant to standard first-line therapy. These clinical observations combined with recent reports demonstrating single agent efficacy in specific contexts make Wee1 a promising target for anticancer therapy. With only one inhibitor in clinical development (AZD1775) and very limited reports at the preclinical stage, the development of alternative, novel Wee1 inhibitors may have significant therapeutic value.

In this study, we describe the development and characterization of ADC730, a potent and highly selective small molecule Wee1 inhibitor. ADC730 inhibits Wee1 kinase activity with an IC50 of <5 nM and demonstrates excellent selectivity when profiled against a diverse panel of kinases. In cellular assays, ADC730 potently inhibited CDC2-dependent Wee1 phosphorylation. Further studies in a panel of cancer cell lines demonstrated strong anti-proliferative activity of ADC730 both in combination with gemcitabine or in monotherapy modalities. Single agent activity was observed in multiple cancer types including lung and kidney. gH2AX foci formation followed by apoptosis induction were typically observed in a dose-dependent manner for the most sensitive cell lines.

In vivo, oral administration of ADC730 (10, 30 mg/kg/day) in combination with gemcitabine caused a significant dose-dependent growth reduction of HT29 tumors and the combination was synergistic. ADC730 was well tolerated in all cases with no signs of adverse effects. Dosed orally as a single agent (10, 30 mg/kg/day), ADC730 also demonstrated robust dose-dependent anti-tumor efficacy in the A427 lung carcinoma model with inhibition of tumor growth consistent with the pharmacodynamic modulation of Wee1 signaling. In comparison and under similar experimental conditions, AZD1775 demonstrated similar efficacy profiles at significantly higher doses.

To conclude, we describe the development and profiling towards candidate nomination of ADC730, a novel potent highly selective Wee1 inhibitor with robust efficacy in cancer xenograft models both in combination and single agent modalities. Subsequent analogs and examples with potentially enhanced profiles will also be described.

Citation Format: Gerald Gavory, Colin O’Dowd, Frank Burkamp, Shane Rountree, Ewelina Rozycka, Caroline Boyd, Beronia Gorges, Stephanie Burton, Andy Wilkinson, Steven Shepherd, Dominic Janssen, Mary McFarland, Shane Rountree, Tim Harrison. A novel, potent and selective inhibitor of Wee1 with robust antitumor activity in various cancer xenograph models. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-159.