More than 75% of breast cancers are estrogen receptor alpha (ERα) positive (ER+), and resistance to current hormone therapies occurs in one-third of ER+ patients. Tumor resistance is still ERα-dependent, but mutations usually confer constitutive activation to the hormone receptor, rendering ERα modulator drugs such as tamoxifen and aromatase inhibitors ineffective. Fulvestrant is a potent selective estrogen receptor degrader (SERD), which degrades the ERα receptor in drug-resistant tumors and has been approved for the treatment of hormone-receptor-positive metastatic breast cancer following antiestrogen therapy. However, fulvestrant shows poor pharmacokinetic properties in human, low solubility, weak permeation, and high metabolism, limiting its administration to inconvenient intramuscular injections. This Drug Annotation describes the identification and optimization of a new series of potent orally available SERDs, which led to the discovery of 6-(2,4-dichlorophenyl)-5-[4-[(3S)-1-(3-fluoropropyl)pyrrolidin-3-yl]oxyphenyl]-8,9-dihydro-7H-benzo[7]annulene-2-carboxylic acid (43d), showing promising antitumor activity in breast cancer mice xenograft models and whose properties warranted clinical evaluation.

中文翻译：

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发现6-（2,4-二氯苯基）-5- [4-[（3S）-1-（3-氟丙基）吡咯烷-3-基]氧基苯基] -8,9-二氢-7H-苯并[7]环戊二酸（SAR439859），一种有效的选择性雌激素受体降解剂（SERD），用于治疗雌激素受体阳性乳腺癌。

超过75％的乳腺癌是雌激素受体α（ERα）阳性（ER +），并且对当前激素疗法的耐药性发生在三分之一的ER +患者中。肿瘤抵抗力仍然是ERα依赖性的，但是突变通常会赋予激素受体组成性激活作用，从而使ERα调节剂药物如他莫昔芬和芳香化酶抑制剂失效。Fulvestrant是一种有效的选择性雌激素受体降解剂（SERD），可在耐药性肿瘤中降解ERα受体，并已被批准用于抗雌激素治疗后治疗激素受体阳性的转移性乳腺癌。然而，氟维司群在人体内显示出较差的药代动力学性质，低溶解度，弱渗透性和高新陈代谢，从而限制了其对不方便的肌内注射的给药。