Discovery of novel quinazoline analogs as tubulin inhibitors targeting the colchicine binding site for potent antitumor therapy in combination with PD-L1 inhibitors.

A new class of quinazoline analogues were rationally designed and synthesized as colchicine binding site inhibitors, demonstrating powerful anticancer activities. Compound 4a stood out as the most effective across four cancer cell, affording a mean IC value of 52 nM marginally superior to that of colchicine (IC = 59 nM), possessing the capacity to circumvent paclitaxel-associated drug resistance. Moreover, treatment with 4a led to a pronounced impairment of clonogenic survival in HepG-2 cells. Mechanistic investigations demonstrated that tubulin polymerization was robustly suppressed by 4ain vitro, concomitant with a marked perturbation of microtubule dynamics. Molecular docking analyses suggested a high affinity binding mode between 4a and the colchicine site on tubulin. Additionally, exposure to 4a evoked a pronounced G2/M arrest and was accompanied by robust activation of apoptosis. Moreover, 4a exposure curbed cancer-cell motility in a concentration-dependent fashion. In vivo, 4a (10 mg/kg) showed significant tumor suppression, achieving a TGI value of 69.25 %. Co-administration of 4a and NP19 (a PD-L1 blockade) led to a pronounced synergistic antitumor effect (TGI 85.20 %). In summary, 4a represents a candidate CBSIs for deeper study.