Design, Synthesis, and Biological Activity Evaluation of Quinazoline-Based PLK4 Inhibitors

Background: As a key regulator of centrosome duplication, polo-like kinase 4 (PLK4) is abnormally overexpressed in various tumors and has emerged as an important target for the development of antitumor drugs. Methods: In this study, based on the lead compound ZSL-M001 (PLK4 IC50 = 3.0 μM) previously obtained by our research group, we designed and synthesized 28 novel quinazoline-based PLK4 inhibitors to enhance kinase inhibitory activity using side-chain extension strategies. Results: Among them, compound H24 (PLK4 IC50 < 0.1 nM) exhibited favorable in vitro antiproliferative activity against TRIM37-amplified MCF-7 breast cancer cells (MCF-7 IC50 = 2.37 ± 0.26 μM) and TRIM37-amplified neuroblastoma IMR-32 cells (IMR-32 IC50 = 1.28 ± 0.04 μM). Its activity was superior to that of the positive control LCR-263. Further in vitro biological evaluation demonstrated that H24 inhibited the colony formation of MCF-7 cells in a concentration-dependent manner, induced S/G2-phase cell-cycle arrest, and promoted apoptosis. H24 also showed favorable metabolic stability in human liver microsomes, with a half-life of 61.3 min. However, no obvious TRIM37 amplification-dependent cellular selectivity was observed in TRIM37 non-highly amplified A549 cells or normal human embryonic kidney HEK-293T cells. Given the suboptimal selectivity of the in vitro antiproliferative activity, Aurora kinase A, which shares high homology with PLK4, was selected for further evaluation of its selectivity. The IC50 for Aurora A inhibition was determined to be 151.2 nM, indicating that its broader kinase selectivity remains to be established. Conclusions: In summary, H24 is a highly potent biochemical PLK4 inhibitor and provides a useful lead scaffold for further optimization rather than a fully selective cellular candidate at the current stage.