Revealing 5-(3,5-difluorobenzyl)-1H-indazole as the active pharmacophore of ALK/ROS1 dual inhibitors through theoretical calculations and biological activity evaluations

Anaplastic lymphoma kinase (ALK) and tyrosine protein kinase (ROS1) are recognized as driver genes in lung cancer, with dual inhibition of both targets offering a promising approach to enhance therapeutic outcomes in non-small cell lung cancer (NSCLC). Although numerous ALK/ROS1 inhibitors have received FDA approval, detailed research into the essential active structural motifs within these inhibitors remains limited. Addressing this gap, the current study employed computer-aided drug design (CADD) methodologies, incorporating bioisosteric and conformational similarity principles to design and synthesize 31 dual-target 2-morpholinobenzamide derivatives. These derivatives each include the 5-(3,5-difluorobenzyl)-1H-indazole, 4-benzylmorpholine, and thiophene moieties. Based on docking binding energies, we proposed that 5-(3,5-difluorobenzyl)-1H-indazole may represent a key pharmacophore for ALK/ROS1 activity. Subsequent kinase and cellular assays validated this hypothesis, with compound X4 exhibiting optimal inhibitory activity against both ALK and ROS1 kinases and lung cancer cell lines, achieving IC values of 0.512 µM (ALK), 0.766 µM (ROS1) and 0.034 ± 0.002 µM (H2228). In vitro antitumor assays demonstrated dose-dependent induction of apoptosis in H2228 cells by X4. Western blot (WB) analysis further confirmed that X4 effectively suppresses the expression of p-ALK and p-ERK. Importantly, X4 exhibited high specificity in targeting ALK and ROS1 across a range of kinases. In an H2228 xenograft model, X4 achieved a tumor inhibition rate of 54.71 %, underscoring its considerable potential in ALK/ROS1 inhibition.