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Supplementary Data 1 from Oral Estrogen Receptor PROTAC Vepdegestrant (ARV-471) Is Highly Efficacious as Monotherapy and in Combination with CDK4/6 or PI3K/mTOR Pathway Inhibitors in Preclinical ER+ Breast Cancer Models

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posted on 2024-08-15, 07:30 authored by Sheryl M. Gough, John J. Flanagan, Jessica Teh, Monica Andreoli, Emma Rousseau, Melissa Pannone, Mark Bookbinder, Ryan Willard, Kim Davenport, Elizabeth Bortolon, Gregory Cadelina, Debbie Gordon, Jennifer Pizzano, Jennifer Macaluso, Leofal Soto, John Corradi, Katherine Digianantonio, Ieva Drulyte, Alicia Morgan, Connor Quinn, Miklós Békés, Caterina Ferraro, Xin Chen, Gan Wang, Hanqing Dong, Jing Wang, David R. Langley, John Houston, Richard Gedrich, Ian C. Taylor

Extended Methods

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Arvinas Estrogen Receptor, Inc

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ARTICLE ABSTRACT

Estrogen receptor (ER) alpha signaling is a known driver of ER-positive (ER+)/human epidermal growth factor receptor 2 negative (HER2−) breast cancer. Combining endocrine therapy (ET) such as fulvestrant with CDK4/6, mTOR, or PI3K inhibitors has become a central strategy in the treatment of ER+ advanced breast cancer. However, suboptimal ER inhibition and resistance resulting from the ESR1 mutation dictates that new therapies are needed. A medicinal chemistry campaign identified vepdegestrant (ARV-471), a selective, orally bioavailable, and potent small molecule PROteolysis-TArgeting Chimera (PROTAC) degrader of ER. We used biochemical and intracellular target engagement assays to demonstrate the mechanism of action of vepdegestrant, and ESR1 wild-type (WT) and mutant ER+ preclinical breast cancer models to demonstrate ER degradation-mediated tumor growth inhibition (TGI). Vepdegestrant induced ≥90% degradation of wild-type and mutant ER, inhibited ER-dependent breast cancer cell line proliferation in vitro, and achieved substantial TGI (87%–123%) in MCF7 orthotopic xenograft models, better than those of the ET agent fulvestrant (31%–80% TGI). In the hormone independent (HI) mutant ER Y537S patient-derived xenograft (PDX) breast cancer model ST941/HI, vepdegestrant achieved tumor regression and was similarly efficacious in the ST941/HI/PBR palbociclib-resistant model (102% TGI). Vepdegestrant-induced robust tumor regressions in combination with each of the CDK4/6 inhibitors palbociclib, abemaciclib, and ribociclib; the mTOR inhibitor everolimus; and the PI3K inhibitors alpelisib and inavolisib. Vepdegestrant achieved greater ER degradation in vivo compared with fulvestrant, which correlated with improved TGI, suggesting vepdegestrant could be a more effective backbone ET for patients with ER+/HER2− breast cancer.

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