ABSTRACT
BRAF is an important component of MAPK cascade. Mutation of BRAF, in particular V600E, leads to hyperactivation of the MAPK pathway and uncontrolled cellular growth. Resistance to selective inhibitors of mutated BRAF is a major obstacle against treatment of many cancer types. In this work, a series of new (imidazo[2,1-b]thiazol-5-yl)pyrimidine derivatives possessing a terminal sulfonamide moiety were synthesized. Pan-RAF inhibitory effect of the new series was investigated, and structure-activity relationship is discussed. Antiproliferative activity of the target compounds was tested against the NCI-60 cell line panel. The most active compounds were further tested to obtain their IC50 values against cancer cells. Compound 27c with terminal open chain sulfonamide and 38a with a cyclic sulfamide moiety showed the highest activity in enzymatic and cellular assay, and both compounds were able to inhibit phosphorylation of MEK and ERK. Compound 38a was selected for testing its in vivo activity against melanoma. Cellular and animal activities are reported.
Subject(s)
Imidazoles/chemistry , Protein Kinase Inhibitors/chemistry , Proto-Oncogene Proteins B-raf/antagonists & inhibitors , Thiazoles/chemistry , Animals , Binding Sites , Cell Line, Tumor , Cell Proliferation/drug effects , Drug Evaluation, Preclinical , Drug Screening Assays, Antitumor , Drug Stability , Half-Life , Humans , Imidazoles/metabolism , Melanoma/drug therapy , Melanoma/pathology , Mice , Mitogen-Activated Protein Kinase Kinases/metabolism , Molecular Docking Simulation , Phosphorylation/drug effects , Protein Kinase Inhibitors/metabolism , Protein Kinase Inhibitors/therapeutic use , Proto-Oncogene Proteins B-raf/metabolism , Structure-Activity Relationship , Sulfonamides/chemistry , Thiazoles/metabolism , Transplantation, HeterologousABSTRACT
A series of imidazothiazole derivatives possessing potential activity against melanoma cells were investigated for molecular mechanism of action. The target compounds were tested against V600E-B-RAF and RAF1 kinases. Compound 1zb is the most potent against both kinases with IC50 values 0.978 and 8.2 nM, respectively. It showed relative selectivity against V600E mutant B-RAF kinase. Compound 1zb was also tested against four melanoma cell lines and exerted superior potency (IC50 0.18-0.59 µM) compared to the reference standard drug, sorafenib (IC50 1.95-5.45 µM). Compound 1zb demonstrated also prominent selectivity towards melanoma cells than normal skin cells. It was further tested in whole-cell kinase assay and showed in-cell V600E-B-RAF kinase inhibition with IC50 of 0.19 µM. Compound 1zb induces apoptosis not necrosis in the most sensitive melanoma cell line, UACC-62. Furthermore, molecular dynamic and 3D-QSAR studies were done to investigate the binding mode and understand the pharmacophoric features of this series of compounds.
