The estrogen receptor (ER) is a validated target for the treatment of estrogen receptor-positive (ER+) breast cancer. Here, we describe the design, synthesis, and extensive structure-activity relationship (SAR) studies of small-molecule ERα degraders based on the proteolysis targeting chimeras (PROTAC) concept. Our efforts have resulted in the discovery of highly potent and effective PROTAC ER degraders, as exemplified by ERD-308 (32). ERD-308 achieves DC50 (concentration causing 50% of protein degradation) values of 0.17 and 0.43 nM in MCF-7 and T47D ER+ breast cancer cell lines, respectively, and induces >95% of ER degradation at concentrations as low as 5 nM in both cell lines. Significantly, ERD-308 induces more complete ER degradation than fulvestrant, the only approved selective ER degrader (SERD), and is more effective in inhibition of cell proliferation than fulvestrant in MCF-7 cells. Further optimization of ERD-308 may lead to a new therapy for advanced ER+ breast cancer.

中文翻译：

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发现 ERD-308 作为雌激素受体 (ER) 的高效蛋白水解靶向嵌合体 (PROTAC) 降解剂。

雌激素受体（ER）是治疗雌激素受体阳性（ER+）乳腺癌的有效靶点。在这里，我们描述了基于蛋白水解靶向嵌合体 (PROTAC) 概念的小分子 ERα 降解剂的设计、合成和广泛的构效关系 (SAR) 研究。我们的努力导致发现了高效和有效的 PROTAC ER 降解剂，例如 ERD-308 (32)。ERD-308 在 MCF-7 和 T47D ER+ 乳腺癌细胞系中分别达到 0.17 和 0.43 nM 的 DC50（导致 50% 蛋白质降解的浓度）值，并在低至 5 nM 的浓度下诱导 >95% 的 ER 降解两种细胞系。值得注意的是，ERD-308 比氟维司群诱导更完全的 ER 降解，氟维司群是唯一批准的选择性 ER 降解剂 (SERD)，并且在 MCF-7 细胞中比氟维司群更有效地抑制细胞增殖。ERD-308的进一步优化可能会导致晚期ER+乳腺癌的新疗法。