new substituted 6,7-dimethoxy-n-phenyl-2-(piperazin-1-yl)quinazolin-4-amine derivatives: synthesis, characterization, cytotoxicity against skbr3 and trastuzumab resistance skbr3 cell lines, and egfr/her2 dual kinase inhibition assay

In this study, we synthesized, characterized, and evaluated the cytotoxicity and dual kinase inhibition of novel substituted quinazoline derivatives in her2-positive skbr3 and trastuzumab-resistant skbr3 (tzb_skbr3) breast cancer cell lines. a series of 6,7-dimethoxy-n-phenyl-2-(piperazin-1-yl)quinazolin-4-amine derivatives (compounds 10–18) were synthesized and structurally characterized using standard spectroscopic techniques. cytotoxicity assays revealed that compounds 12 and 14 exhibited the most potent anti-proliferative effects, with ic50 values of 6.75 ± 0.36 and 8.92 ± 0.61 µg/ml against skbr3 cells, and 7.61 ± 0.44 and 9.53 ± 0.49 µg/ml, respectively, against tzb_skbr3 cells. these values were comparable to or lower than that of tzb, which showed reduced potency against tzb_skbr3 (ic50 = 25.89 ± 1.34 µg/ml) compared to skbr3 (ic50 =7.58 ± 0.42 µg/ml), indicating acquired resistance. at 25 µg/ml, compound 12 reduced skbr3 and tzb_skbr3 cell viability to 4.89% and 6.39%, respectively, whereas compound 14 reduced viability to 5.74% and 7.81%, outperforming tzb in tzb_skbr3 cells (55.63% viability at the same concentration). morphological assessment revealed hallmark apoptotic changes, including cell shrinkage and membrane blabbing in both skbr3 and tzb_skbr3 cells treated with 12 and 14. egfr/her2 kinase inhibition assays showed that compounds 12 and 14 significantly inhibited both the kinases in a dose-dependent manner. compound 12 exhibited superior her2 inhibition, reaching nearly complete inhibition at 500 nm, which is comparable to or exceeding that of lapatinib, a standard dual inhibitor. dna fragmentation analysis confirmed apoptotic cell death, and western blot analysis showed decreased phosphorylation of egfr and her2, along with the upregulation of apoptotic markers in both cell lines following treatment with compounds 12 and 14. these results highlight compounds 12 and 14 as promising dual egfr/her2 inhibitors with potent cytotoxic activity against both tzb-sensitive and tzb-resistant her2-positive breast cancer cells.