Design and synthesis of novel 2-S-alkylated Quinazolinones as dual BRAFV600E and EGFR inhibitors in melanoma: Mechanistic insights from apoptosis and cell cycle modulation

Melanoma, an aggressive and highly metastatic form of skin cancer, remains challenging to treat due to its resistance to conventional therapies and frequent mutations in the BRAF signaling pathway. In this study, we report the design and synthesis of a novel series of thirteen quinazolinone derivatives, featuring a phenyl thiazole moiety linked via a triazole acetamide spacer. These compounds were developed as potential dual inhibitors of BRAF^V600E and EGFR, which should offer a promising therapeutic strategy for melanoma treatment. The antiproliferative activity of these compounds was evaluated against the NCI-60 cell line panel, with six compounds advancing to a five-dose screening. Three compounds, 7k, 7l, and 7m, exhibited broad-spectrum anticancer activity, with mean growth inhibition (GI%) exceeding 100 %. Compound 7l demonstrated exceptional efficacy against melanoma subpanels (GI% = 152 %) and potent dual kinase inhibition, with IC₅₀ values of 0.048 μM against B-RAF^V600E and 0.037 μM against EGFR. In vitro studies of compound 7l revealed significant cytotoxicity against MALME-3 M (IC₅₀ = 3.16 μM) and LOX-IMVI (IC₅₀ = 2.50 μM) melanoma cell lines, with minimal toxicity towards normal Vero cells. Cell cycle analysis showed G1-phase arrest and disrupted DNA synthesis in melanoma cells, while apoptosis assays demonstrated a dramatic increase in early apoptotic cells from 7.28 % to 40.69 %. Compound 7l modulated key apoptotic markers, increasing the BAX/Bcl-2 ratio by 14.42-fold and elevating caspase 3 and 9 levels, indicating its potential to overcome drug resistance and enhance therapeutic efficacy in melanoma treatment.