An inhibitor of ERK dimerization (IC50 = ~0.5 μM for disruption of EGF-induced co-immunoprecipitation of ERK); has no effect on ERK phosphorylation or kinase activity (IC50s = >10 μM); inhibits cell growth in a panel of melanoma and colorectal cancer cell lines (IC50s = 150-400 nM); inhibits ERK dimerization in liver extract and tumor tissue and inhibits tumor progression in an A375 mouse xenograft model at 15 mg/kg; reduces tumor growth in a BRAF mutant colorectal cancer PDX mouse model