Discovery of a novel dual-target inhibitor of CDK12 and PARP1 that induces synthetic lethality for treatment of triple-negative breast cancer

Triple negative breast cancer (TNBC) is one of the most aggressive breast tumors, with a high rate of recurrence and metastasis as well as a poor prognosis. Consequently, it is urgent to find new targeted therapeutic strategies and development of corresponding drugs. Previous studies have shown that CDK12 inhibitors in combination with PARP1 inhibitors is able to induce synthetic lethality in TNBC cells. Here, we reported simultaneously inhibition of CDK12 and PARP1 by genetic or pharmacological approaches synergistically inhibited the proliferation of TNBC cells. Then, a series of small molecule inhibitors targeting both CDK12 and PARP1 were designed and synthesized. The new dual-target inhibitor (12e) showed potent inhibitory activity against CDK12 (IC50 = 285 nM) and PARP1 (IC50 = 34 nM), as well as good anti-proliferative effects in TNBC cell lines. Meanwhile, compound 12e showed favorable synergistic anti-tumor efficacy in cells and xenografts by inhibiting DNA damage repair, promoting cell cycle arrest and apoptosis. Taken together, we successfully synthesized the first effective CDK12-PARP1 dual inhibitor, which is expected to be an attractive therapeutic strategy for TNBC.