P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) is a principal obstacle for successful cancer chemotherapy. A novel P-gp inhibitor with a quinazoline scaffold, 12k, was considered to be the most promising for in-depth study. 12k possessed high potency (EC₅₀ = 57.9 ± 3.5 nM), low cytotoxicity, and long duration of activity in reversing doxorubicin (DOX) resistance in K562/A02 cells. 12k also boosted the potency of other MDR-related cytotoxic agents with different structures, increased accumulation of DOX, blocked P-gp-mediated Rh123 efflux, and suppressed P-gp ATPase activity in K562/A02 MDR cells. However, 12k did not have any effects on CYP3A4 activity or P-gp expression. In particular, 12k had a good half-life and oral bioavailability and displayed no influence on DOX metabolism to obviate the side effects closely related to increased plasma concentrations of cytotoxic agents in vivo.

中文翻译：

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N-（4-（2（6,7-二甲氧基-3,4-二氢异喹啉-2（1 H）基）乙基）苯基）喹唑啉-4-胺衍生物的设计，合成及药理学表征：新型可逆P抑制剂-糖蛋白介导的多药耐药性

P-糖蛋白（P-gp）介导的多药耐药性（MDR）是成功进行癌症化疗的主要障碍。具有喹唑啉骨架的新型P-gp抑制剂12k被认为是最有希望进行深入研究的。12k具有高效力（EC ₅₀ = 57.9±3.5 nM），低细胞毒性，并且在逆转K562 / A02细胞对阿霉素（DOX）的耐药性方面具有很长的活性。12k还增强了具有不同结构的其他MDR相关细胞毒性剂的效力，增加了DOX的积累，阻断了K562 / A02 MDR细胞中P-gp介导的Rh123外排，并抑制了P-gp ATPase活性。但是，12k对CYP3A4活性或P-gp表达没有任何影响。尤其是，12k具有良好的半衰期和口服生物利用度，并且对DOX代谢无影响，从而消除了与体内细胞毒剂血浆浓度升高密切相关的副作用。