Selective, allosteric inhibitor of mitogen-activated extracellular signal regulated kinase 1 (MEK1) and MEK2 activation and kinase activity. This extracellular signal related kinase (ERK) pathway is often activated by mutated forms of BRAF in melanoma and other cancers. Blocks mitogen-activated protein kinase pathway reducing proliferation of melanoma cells carrying mutation. The gene discussed is MAP2K1; the disease is cancer.