Discovery of a novel pan-RAF inhibitor with potent anti-tumor activity in preclinical models of BRAFV600E mutant cancer

AimsBRAF mutations, especially BRAF V600E, are a frequent occurrence in malignant melanomas. The BRAF inhibitors are used as the care standard for BRAF-mutant metastatic melanomas. However, melanomas rapidly develop resistance to BRAF inhibitors after a median response duration of 6 months, and the subsequent rapid development of cutaneous toxicity is enhanced by the paradoxical activation of CRAF. In this study, we discovered a potent and selective pan-RAF inhibitor: INU-152. The goal of this study was to investigate whether the inhibition of pan-RAF with INU-152 completely disrupts the MAPK pathway in cancer cells bearing BRAF or RAS mutations.Main methodsUsing a structure-based molecular modeling, we discovered INU-152, which is a potent and selective pan-RAF inhibitor. In kinase assays against RAF proteins, INU-152 exhibited a potent effect against RAF isoforms. INU-152 was tested for its inhibitory effect on the growth of human cancer cells bearing BRAFV600E. To study in vivo effects, INU-152 was administered using human melanoma and colorectal cancer xenograft models. To explore INU-152′s potential as a prospective drug candidate, pharmacokinetic studies and toxicity tests were performed using mice.Key findingsTo inhibit and suppress paradoxical activation in mutant RAS cancer cells completely, it is important for RAF inhibitors to exhibit potent inhibitory activities against RAF isoforms.SignificanceINU-152 inhibits all RAF isoforms and inhibits MAPK pathways in mutant BRAF cells. More importantly, INU-152 exhibits minimal paradoxical pathway activation in melanoma cells with mutant RAS. INU-152 exhibits anti-tumor activities in xenograft models carrying BRAF mutations.