Identification of Novel Dual-Target Estrogen Receptor α Degraders with Tubulin Inhibitory Activity for the Treatment of Endocrine-Resistant Breast Cancer.

Endocrine resistance remains a significant problem in the clinical treatment of estrogen receptor α-positive (ERα+) breast cancer (BC). In this study, we developed a series of novel dual-functional ERα degraders based on a bridged bicyclic scaffold with selenocyano (SeCN) side chains. These compounds displayed potent ERα degradation and tubulin depolymerization activity. Among them, compounds 35s and 35t exhibited the most promising antiproliferative and ERα degradation activity in multiple ERα+ BC cell lines bearing either wild-type or mutant ERα. Meanwhile, compounds 35s and 35t disrupted the microtubule network by restraining tubulin polymerization, evidenced by 35t inducing cell cycle arrest in the G2/M phase. In MCF-7 and LCC2 xenograft models, compounds 35s and 35t remarkably suppressed tumor growth without noticeable poisonousness. Finally, this study provided guidance for developing new dual-target antitumor drug candidates for the ERα+ BC therapy, especially for the resistant variant.

Novel hybrid conjugates with dual estrogen receptor α degradation and histone deacetylase inhibitory activities for breast cancer therapy.

Hormone therapy targeting estrogen receptors is widely used clinically for the treatment of breast cancer, such as tamoxifen, but most of them are partial agonists, which can cause serious side effects after long-term use. The use of selective estrogen receptor down-regulators (SERDs) may be an effective alternative to breast cancer therapy by directly degrading ERα protein to shut down ERα signaling. However, the solely clinically used SERD fulvestrant, is low orally bioavailable and requires intravenous injection, which severely limits its clinical application. On the other hand, double- or multi-target conjugates, which are able to synergize antitumor activity by different pathways, thus may enhance therapeutic effect in comparison with single targeted therapy. In this study, we designed and synthesized a series of novel dual-functional conjugates targeting both ERα degradation and histone deacetylase inhibiton by combining a privileged SERD skeleton 7-oxabicyclo[2.2.1]heptane sulfonamide (OBHSA) with a histone deacetylase inhibitor side chain. We found that substituents on both the sulfonamide nitrogen and phenyl group of OBHSA unit had significant effect on biological activities. Among them, conjugate 16i with N-methyl and naphthyl groups exhibited potent antiproliferative activity against MCF-7 cells, and excellent ERα degradation activity and HDACs inhibitory ability. A further molecular docking study indicated the interaction patterns of these conjugates with ERα, which may provide guidance to design novel SERDs or PROTAC-like SERDs for breast cancer therapy.

Design, synthesis and biological evaluation of novel dual-acting modulators targeting both estrogen receptor α (ERα) and lysine-specific demethylase 1 (LSD1) for treatment of breast cancer.

Breast cancer is a multi-factor disease, thus more and more drug combination therapies are applied in the treatment. However, there are undeniable disadvantages in drug combination therapy. Therefore, the development of new dual-targeting drugs has become a new strategy. In this study, we have developed a series of dual-acting agents targeting both estrogen receptor α (ERα) and histone demethylase based on a privileged OBHS pharmacophore scaffold developed previously by our laboratory. These novel OBHS-LSD1i conjugates showed excellent ERα binding affinity and selectivity, and exhibited potent inhibitory activity against lysine specific demethylase 1 (LSD1). Several conjugates showed higher antiproliferative efficacy in MCF-7 breast cancer cell line compared to 4-hydroxytamoxifen in vitro. Among them, the best compound 11g displayed potent inhibitory activity against LSD1 and MCF-7 cells with IC50 values of 1.55 µM and 8.79 µM, respectively. Flow cytometry analysis of apoptosis of 11g suggested that the effect of this type compounds on MCF-7 cells is partly caused by inducing apoptosis. Moreover, the molecular docking of 11g with ERα and the active site of LSD1/CoREST complex provides practical way for understanding the dual mechanism actions of this kind of compounds with the targets. As such, these compounds have shown potential to become promising leads for the development of highly efficient dual-acting modulators for breast cancer therapies.

Construction of benzofuranone library via a metal-free, one-pot intermolecular condensation, and their application as efficient estrogen receptor ß modulators.

Facile synthesis of benzofuranone was achieved through a metal-free, one-pot intermolecular condensation between α-hydroxy aryl ketones and resorcinol derivatives. A library of 20 compounds with moderate to good overall yields was prepared. These compounds showed strong binding toward estrogen receptors along with good selectivity for ERß (>190-fold over ERα). Anti-proliferative activity on DU-145, U-87, and MCF-7 cells gave inhibition IC50 values in the low µM range, which suggested the promising potential therapeutic applications of these new classes of benzofuranones.

Novel class of 7-Oxabicyclo[2.2.1]heptene sulfonamides with long alkyl chains displaying improved estrogen receptor α degradation activity.

Hormone therapy is widely used in clinic for breast cancer treatment, such as tamoxifen, but long-term use can cause drug resistance. In this regard, a strategy based on small molecule-induced protein degradation, i.e. selective estrogen receptor downregulator (SERD), might be an effective alternative to hormone therapy for breast cancer. However, most of the SERD candidates involve very limited scaffolds and are still in clinical trials, and none of them has been approved for marketing. In this study, a series of novel 7-oxabicyclo[2.2.1]heptene sulfonamide (OBHSA) derivatives with long alkyl chains were identified as novel SERDs. We found that the position and the length of alkyl side chain have significant effect on the biological activity of the SERD compounds and with the six-carbon side chain was the best. Among them, compounds 23a and 36 displayed potent inhibitory activity against MCF-7 breast cancer cell line with IC50 values of 0.84 µM and 0.77 µM, respectively, as well as excellent ERα degradation activity. Primary mechanism study indicated that the degradation of ERα is mediated through proteasome-mediated process. Flow cytometry analysis of apoptosis of 36 suggested that the effect of this type compounds on MCF-7 cells is associated with apoptosis. As such, these compounds have shown potential to become promising leads for the development of highly efficient SERDs for drug-resistance breast cancer therapies.

Novel Hybrid Conjugates with Dual Suppression of Estrogenic and Inflammatory Activities Display Significantly Improved Potency against Breast Cancer.

In this work, we developed a small library of novel OBHS-RES hybrid compounds with dual inhibition activities targeting both the estrogen receptor α (ERα) and NF-κB by incorporating resveratrol (RES), a known inhibitor of NF-κB, into a privileged indirect antagonism structural motif (OBHS, oxabicycloheptene sulfonate) of estrogen receptor (ER). The OBHS-RES conjugates could bind well to ER and showed remarkable ERα antagonistic activity, and they also exhibited excellent NO inhibition in macrophage RAW 264.7 cells. Compared with 4-hydroxytamoxifen, some of them showed better antiproliferative efficacy in MCF-7 cell lines with IC50 up to 3.7 µM. In vivo experiments in a MCF-7 breast cancer model in Balb/c nude mice indicated that compound 26a was more potent than tamoxifen. Exploration of the compliancy of the structure against ER specificity utilizing these types of isomeric three-dimensional ligands indicated that one enantiomer had much better biological activity than the other.

A high-affinity subtype-selective fluorescent probe for estrogen receptor ß imaging in living cells.

Estrogen receptor ß (ERß) has recently been identified as a pharmaceutical target in hormone replacement therapy for breast cancers. However, the biological function of ERß in disease progression remains unclear. A highly ERß-selective fluorescent probe (FPNM) was discovered exhibiting nanomolar affinity for ERß with an ERß/ERα selectivity as high as 80, which allowed specific labeling of intracellular ERß. Moreover, distinct ERß dynamics in various cellular bio-settings such as prostate cancer (DU-145) or triple-negative breast cancer (MDA-MB-231) cells were directly observed for the first time viaFPNM staining.

Dual functional small molecule fluorescent probes for image-guided estrogen receptor-specific targeting coupled potent antiproliferative potency for breast cancer therapy.

A strategy by integrating biological imaging into early stages of the drug discovery process can improve our understanding of drug activity during preclinical and clinical study. In this article, we designed and synthesized coumarin-based nonsteroidal type fluorescence ligands for drug-target binding imaging. Among these synthesized compounds, 3e, 3f and 3h showed potent ER binding affinity and 3e (IC50=0.012µM) exhibited excellent ERα antagonistic activity, its antiproliferative potency in breast cancer MCF-7 cells is equipotent to the approved drug tamoxifen. The fluorescence of compounds 3e and 3f depended on the solvent properties and showed significant changes when mixed with ERα or ERß in vitro. Furthermore, target molecule 3e could cross the cell membrane, localize and image drug-target interaction in real time without cell washing. Thus, the coumarin-based platform represents a promising new ER-targeted delivery vehicle with potential imaging and therapeutic properties.