Design, synthesis and biological evaluation of novel 1,3,5-triazine derivatives containing benzo[d]imidazole scaffold as PI3K inhibitors.

Twenty-seven novel 1,3,5-triazine derivatives containing benzo[d]imidazole scaffold were designed, synthesized, and evaluated for anti-tumor activity as PI3Kα inhibitors. Assessment of PI3Kα inhibitory effects revealed that some compounds were highly potent in vitro, with seventeen compounds (LNP1, LNP2, LNP4, LNP7-LNP10, LNP12-LNP18, LNP20, LNP23, and LNP24) showing IC₅₀ values less than 100 nM. Notably, LNP23 and LNP24 showed remarkable potency against PI3Kα with IC₅₀ values of 5.15 nM and 8.88 nM, respectively, and thus they were more potent than positive control drug ZSTK474 (PI3Kα, IC₅₀ = 9.89 nM). Compared with ZSTK474, LNP23 and LNP24 also exhibited increased selectivity for PI3Kα over other class I PI3K isoforms. Evaluation of some compounds on MDA-MB-231, MCF-7, and H1975 cell lines revealed that most of them possessed moderate to outstanding antiproliferative activities. LNP23 demonstrated marked inhibitory activity on cell proliferation, with IC₅₀ values of 6.85 μM (MDA-MB-231), 1.29 μM (MCF-7), and 2.13 μM (H1975). Antitumor mechanism of action of compound LNP23 on MCF-7 cells was investigated, including protein expression of p-PI3K and p-AKT by Western blot assay, AO/EB staining assay, hoechst33342 assay, cell apoptosis assays by flow cytometry, cell cycle analysis by flow cytometry, clone formation assay and transwell migration assay. Additionally, the preliminary SARs of these compounds were also discussed.