6-(5-bromo-2-hydroxybenzoyl)-2-((3-methoxyphenyl)amino)pyrazolo[1,5-a]pyrimidine-3‑carbonitrile promotes apoptosis by blocking the ERK MAP K-MCL1 signaling pathway in H1975 non-small cell lung cancer cells.

Aberrant activation of the ERK mitogen-activated protein kinase (MAPK) pathway contributes to the progression and therapeutic resistance of non-small cell lung cancer (NSCLC) by promoting the expression of pro-survival proteins, including myeloid cell leukemia-1 (MCL-1). In the present study, we synthesized a series of 17 6-(2-hydroxybenzoyl)-2-(phenylamino)pyrazolo[1,5-a]pyrimidine-3‑carbonitrile derivatives (PPCs) and evaluated their anti-proliferative activity in H1975 NSCLC cells. Among derivatives, PPC-15, 6-(5-bromo-2-hydroxybenzoyl)-2-((3-methoxyphenyl)amino)pyrazolo[1,5-a]pyrimidine-3‑carbonitrile, exhibited the most potent inhibitory effect on clonogenic growth and significantly induced apoptotic cell death. Mechanistically, PPC-15 reduced ERK MAPK phosphorylation and decreased MCL-1 expression, along with the active forms of caspase-7, caspase-3, and poly(ADP-ribose) polymerase (PARP) cleavage. Furthermore, density functional theory (DFT) calculations were performed to characterize the chemical reactivity of PPC-15, and molecular docking analysis predicted a favorable binding interaction between PPC-15 and ERK1. Collectively, these findings suggest that PPC-15 represents a promising pyrazolo[1,5-a]pyrimidine-based scaffold that targets the ERK MAPK-MCL-1 survival axis and may provide a potential therapeutic strategy for NSCLC treatment.