Signal transducer and activator of transcription 3 (STAT3) is a transcription factor and an attractive therapeutic target for cancer and other human diseases. Despite 20 years of persistent research efforts, targeting STAT3 has been very challenging. We report herein the structure-based discovery of potent small-molecule STAT3 degraders based upon the proteolysis targeting chimera (PROTAC) concept. We first designed SI-109 as a potent, small-molecule inhibitor of the STAT3 SH2 domain. Employing ligands for cereblon/cullin 4A E3 ligase and SI-109, we obtained a series of potent PROTAC STAT3 degraders, exemplified by SD-36. SD-36 induces rapid STAT3 degradation at low nanomolar concentrations in cells and fails to degrade other STAT proteins. SD-36 achieves nanomolar cell growth inhibitory activity in leukemia and lymphoma cell lines with high levels of phosphorylated STAT3. A single dose of SD-36 results in complete STAT3 protein degradation in xenograft tumor tissue and normal mouse tissues. SD-36 achieves complete and long-lasting tumor regression in the Molm-16 xenograft tumor model at well-tolerated dose-schedules. SD-36 is a potent, selective, and efficacious STAT3 degrader.

中文翻译：

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基于结构的 SD-36 作为 STAT3 蛋白的有效、选择性和有效的 PROTAC 降解剂的发现。

信号转导和转录激活因子 3 (STAT3) 是一种转录因子，是癌症和其他人类疾病的有吸引力的治疗靶点。尽管进行了 20 年的持续研究努力，但针对 STAT3 的目标一直非常具有挑战性。我们在此报告了基于蛋白水解靶向嵌合体 (PROTAC) 概念的有效小分子 STAT3 降解剂的基于结构的发现。我们首先将 SI-109 设计为 STAT3 SH2 结构域的有效小分子抑制剂。使用 cereblon/cullin 4A E3 连接酶和 SI-109 的配体，我们获得了一系列有效的 PROTAC STAT3 降解剂，以 SD-36 为例。SD-36 在细胞中以低纳摩尔浓度诱导 STAT3 快速降解，并且不能降解其他 STAT 蛋白。SD-36 在具有高水平磷酸化 STAT3 的白血病和淋巴瘤细胞系中实现纳摩尔细胞生长抑制活性。单剂量的 SD-36 会导致异种移植肿瘤组织和正常小鼠组织中的 STAT3 蛋白完全降解。SD-36 以耐受良好的剂量方案在 Molm-16 异种移植肿瘤模型中实现了完全和持久的肿瘤消退。SD-36 是一种强效、选择性和有效的 STAT3 降解剂。