Cyclin-dependent kinase 12 (CDK12) plays a crucial role in DNA-damage response gene transcription and has recently been validated as a promising target in cancer therapy. However, existing CDK12 inhibitors potently inhibit its closest isoform CDK13, which could cause potential toxicity. Therefore, the development of CDK12 inhibitors with isoform-selectivity against CDK13 continues to be a challenge. By taking advantage of the emerging PROteolysis-TArgeting Chimeras (PROTACs) approach, we have synthesized a potent PROTAC degrader PP-C8 based on the noncovalent dual inhibitors of CDK12/13 and demonstrated its specificity for CDK12 over CDK13. Notably, PP-C8 induces profound degradation of cyclin K simultaneously and downregulates the mRNA level of DNA-damage response genes. Global proteomics profiling revealed PP-C8 is highly selective toward CDK12-cyclin K complex. Importantly, PP-C8 demonstrates profound synergistic antiproliferative effects with PARP inhibitor in triple-negative breast cancer (TNBC). The potent and selective CDK12 PROTAC degrader developed in this study could potentially be used to treat CDK12-dependent cancers as combination therapy.

细胞周期蛋白依赖性激酶 12 (CDK12) 在 DNA 损伤反应基因转录中起着至关重要的作用，最近已被证实是癌症治疗中的一个有希望的靶点。然而，现有的 CDK12 抑制剂会有效抑制其最接近的同种型 CDK13，这可能会导致潜在的毒性。因此，开发对 CDK13 具有同种型选择性的 CDK12 抑制剂仍然是一个挑战。通过利用新兴的 PROteolysis-TArgeting Chimeras (PROTACs) 方法，我们合成了一种基于 CDK12/13 的非共价双重抑制剂的强效 PROTAC 降解剂PP-C8 ，并证明其对 CDK12 的特异性优于 CDK13。值得注意的是，PP-C8同时诱导细胞周期蛋白 K 的深度降解并下调 DNA 损伤反应基因的 mRNA 水平。全球蛋白质组学分析显示PP-C8对 CDK12-cyclin K 复合物具有高度选择性。重要的是，PP-C8与 PARP 抑制剂在三阴性乳腺癌 (TNBC) 中表现出深刻的协同抗增殖作用。本研究中开发的强效和选择性 CDK12 PROTAC 降解剂可能用于治疗 CDK12 依赖性癌症作为联合疗法。