The allosteric MEK inhibitor PD 0325901 also exhibited promising selective pre-clinical anti-cancer efficacy in vivo as a single agent, doses of 10–25 mg/kg causing significant tumour growth inhibition and in many cases regression, in a range of murine and human tumour xenograft models, including those which were BRAF or KRAS wild type or mutant [6], [10], [11], [12], [13], [14]. Here, KRAS is linked to neoplasm.