RESUMO
PURPOSE: 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. EXPERIMENTAL DESIGN: 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). RESULTS: 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. CONCLUSIONS: 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.
Assuntos
Neoplasias da Mama , Quinase 4 Dependente de Ciclina , Quinase 6 Dependente de Ciclina , Transdução de Sinais , Serina-Treonina Quinases TOR , Ensaios Antitumorais Modelo de Xenoenxerto , Humanos , Feminino , Animais , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/patologia , Neoplasias da Mama/metabolismo , Quinase 6 Dependente de Ciclina/antagonistas & inibidores , Quinase 4 Dependente de Ciclina/antagonistas & inibidores , Camundongos , Serina-Treonina Quinases TOR/metabolismo , Serina-Treonina Quinases TOR/antagonistas & inibidores , Linhagem Celular Tumoral , Transdução de Sinais/efeitos dos fármacos , Receptor alfa de Estrogênio/metabolismo , Receptor alfa de Estrogênio/genética , Receptor alfa de Estrogênio/antagonistas & inibidores , Piperazinas/farmacologia , Piperazinas/administração & dosagem , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Inibidores de Fosfoinositídeo-3 Quinase/farmacologia , Inibidores de Fosfoinositídeo-3 Quinase/administração & dosagem , Receptores de Estrogênio/metabolismo , Piridinas/administração & dosagem , Piridinas/farmacologia , Inibidores de Proteínas Quinases/farmacologia , Proliferação de Células/efeitos dos fármacosRESUMO
The identification of VHL-binding proteolysis targeting chimeras (PROTACs) that potently degrade the BRM protein (also known as SMARCA2) in SW1573 cell-based experiments is described. These molecules exhibit between 10- and 100-fold degradation selectivity for BRM over the closely related paralog protein BRG1 (SMARCA4). They also selectively impair the proliferation of the H1944 "BRG1-mutant" NSCLC cell line, which lacks functional BRG1 protein and is thus highly dependent on BRM for growth, relative to the wild-type Calu6 line. In vivo experiments performed with a subset of compounds identified PROTACs that potently and selectively degraded BRM in the Calu6 and/or the HCC2302 BRG1 mutant NSCLC xenograft models and also afforded antitumor efficacy in the latter system. Subsequent PK/PD analysis established a need to achieve strong BRM degradation (>95%) in order to trigger meaningful antitumor activity in vivo. Intratumor quantitation of mRNA associated with two genes whose transcription was controlled by BRM (PLAU and KRT80) also supported this conclusion.