In vitro activity: SCH772984 is a novel, selective and ATP competitive inhibitor of ERK1/2. SCH772984 inhibits phosphorylation of the ERK substrate p90 ribosomal S6 kinase (T359/S363 phospho-RSK) in a dose-dependent manner. SCH772984 also inhibits phosphorylation of residues in the activation loop of ERK itself. SCH772984 demonstrates EC50 values<500 nM in approximately 88% and 49% of BRAF-mutant or RAS-mutant tumor lines, respectively. Importantly, SCH772984 effectively inhibited MAPK signaling and cell proliferation in tumor cells resistant to concurrent treatment with BRAF and MEK inhibitors.

Kinase Assay: SCH772984 is tested in 8 point dilution curves in duplicate against purified ERK2 or ERK1. The enzyme is added to the reaction plate. and incubated with the compound before adding a solution of substrate peptide and ATP. 14μl of diluted enzyme (0.3ng active ERK2 per reaction) is added to each well of a 384-well plate. The plates are gently shaken to mix the reagents and incubated for 45 minutes at room temperature. The reaction is stopped with 60μl of IMAP Binding Solution (1:2200 dilutions of IMAP beads in 1X Binding Buffer). The plates are incubated at room temperature for an additional 0.5 hours to allow complete binding of phosphopeptides to the IMAP beads. Plates are read on the LJL Analyst.

Cell Assay: Cell proliferation experiments are performed in a 96-well format (six replicates), and cells (BRAF-mutant or RAS-mutant tumor lines) are plated at 4,000/well density. At 24 h after cell seeding, cells are treated with DMSO or 9 point IC50 dilution (0.001-10 μM) at 1% DMSO final for all concentrations. Viability is assayed on 5 days after dosing using ViaLight luminescence kit following the manufacturer’s recommendations. For cell line panel viability assay, cells are treated with SCH772984 for 4 days and assayed by CellTiterGlo luminescent cell viability assay.