Tunlametinib (HL-085) is a highly selective and oral inhibitor of MEK1/2 with an IC50 of 1.9 nM for MEK1, with the potential to treat RAS/RAF mutant cancers. It also induces cell cycle arrest at the G0/G1 phase and promotes apoptosis in a dose-dependent manner. It also exhibits antitumor activity in patients with advanced NRAS-mutant melanoma.