journal contribution
posted on 2023-03-30, 23:48 authored by Hazel M. Weir, Robert H. Bradbury, Mandy Lawson, Alfred A. Rabow, David Buttar, Rowena J. Callis, Jon O. Curwen, Camila de Almeida, Peter Ballard, Michael Hulse, Craig S. Donald, Lyman J.L. Feron, Galith Karoutchi, Philip MacFaul, Thomas Moss, Richard A. Norman, Stuart E. Pearson, Michael Tonge, Gareth Davies, Graeme E. Walker, Zena Wilson, Rachel Rowlinson, Steve Powell, Claire Sadler, Graham Richmond, Brendon Ladd, Ermira Pazolli, Anne Marie Mazzola, Celina D'Cruz, Chris De Savi <p>Methods are given for: the use of SILAC assays to measure the rate of estrogen receptor α peptide degradation over time, the measurement of compound binding affinity of estrogen receptor α ligand binding domain using BIAcore, immunoblotting of estrogen and progesterone receptor proteins, RNA extraction and transcript analysis of estrogen receptor regulated genes, rat uterine model and human breast xenograft model studies, analysis of proteins from tumour fragments and measurement of compound concentration in animal models.</p>
History
ARTICLE ABSTRACT
Fulvestrant is an estrogen receptor (ER) antagonist administered to breast cancer patients by monthly intramuscular injection. Given its present limitations of dosing and route of administration, a more flexible orally available compound has been sought to pursue the potential benefits of this drug in patients with advanced metastatic disease. Here we report the identification and characterization of AZD9496, a nonsteroidal small-molecule inhibitor of ERα, which is a potent and selective antagonist and downregulator of ERα in vitro and in vivo in ER-positive models of breast cancer. Significant tumor growth inhibition was observed as low as 0.5 mg/kg dose in the estrogen-dependent MCF-7 xenograft model, where this effect was accompanied by a dose-dependent decrease in PR protein levels, demonstrating potent antagonist activity. Combining AZD9496 with PI3K pathway and CDK4/6 inhibitors led to further growth-inhibitory effects compared with monotherapy alone. Tumor regressions were also seen in a long-term estrogen-deprived breast model, where significant downregulation of ERα protein was observed. AZD9496 bound and downregulated clinically relevant ESR1 mutants in vitro and inhibited tumor growth in an ESR1-mutant patient-derived xenograft model that included a D538G mutation. Collectively, the pharmacologic evidence showed that AZD9496 is an oral, nonsteroidal, selective estrogen receptor antagonist and downregulator in ER+ breast cells that could provide meaningful benefit to ER+ breast cancer patients. AZD9496 is currently being evaluated in a phase I clinical trial. Cancer Res; 76(11); 3307–18. ©2016 AACR.
