 The RASRAFMEKERK pathway is a critical proliferation pathway in many human cancers. This pathway can be constitutively activated by alterations in specific proteins, including BRAF, which phosphorylates MEK1 and MEK2 on two regulatory serine residues. Approximately 90 of all identified BRAF mutations that occur in human result in a V600 EDKamino acid substitution. This mutation appears to mimic regulatory phophorylation and increases BRAF activity approximately 10-fold compared to wild type. BRAF mutations have been identified at a high frequency in specific cancers, including approximately 40-60 of melanoma. The frequency of this activating mutation and the pathway addiction to which it leads makes mutated BRAF an extremely attractive target. 