Cyclin-dependent kinase 12 (CDK12) is an emerging therapeutic target due to its role in regulating transcription of DNA-damage response (DDR) genes. However, development of selective small molecules targeting CDK12 has been challenging due to the high degree of homology between kinase domains of CDK12 and other transcriptional CDKs, most notably CDK13. In the present study, we report the rational design and characterization of a CDK12-specific degrader, BSJ-4-116. BSJ-4-116 selectively degraded CDK12 as assessed through quantitative proteomics. Selective degradation of CDK12 resulted in premature cleavage and poly(adenylation) of DDR genes. Moreover, BSJ-4-116 exhibited potent antiproliferative effects, alone and in combination with the poly(ADP-ribose) polymerase inhibitor olaparib, as well as when used as a single agent against cell lines resistant to covalent CDK12 inhibitors. Two point mutations in CDK12 were identified that confer resistance to BSJ-4-116, demonstrating a potential mechanism that tumor cells can use to evade bivalent degrader molecules.

细胞周期蛋白依赖性激酶 12 (CDK12) 是一个新兴的治疗靶点，因为它在调节 DNA 损伤反应 (DDR) 基因的转录中发挥作用。然而，由于 CDK12 的激酶结构域与其他转录 CDK（尤其是 CDK13）之间的高度同源性，靶向 CDK12 的选择性小分子的开发一直具有挑战性。在本研究中，我们报告了 CDK12 特异性降解剂 BSJ-4-116 的合理设计和表征。通过定量蛋白质组学评估，BSJ-4-116 选择性降解 CDK12。CDK12 的选择性降解导致 DDR 基因的过早切割和聚（腺苷酸化）。此外，BSJ-4-116 单独或与聚（ADP-核糖）聚合酶抑制剂奥拉帕尼联合使用时表现出有效的抗增殖作用，以及用作对共价 CDK12 抑制剂耐药的细胞系的单一药物时。鉴定出 CDK12 中的两个点突变赋予对 BSJ-4-116 的抗性，证明了肿瘤细胞可以用来逃避二价降解分子的潜在机制。