A new phase II clinical trial has demonstrated that treatment with MEK162, a small-molecule MEK inhibitor, resulted in a partial response in patients with advanced melanoma whose tumours harboured NRAS mutations. The study split patients according to their mutation status: those with NRAS mutations (n = 30) versus those with Val600 BRAF mutations (n = 41). Of the NRAS-mutated group, 20% had a partial response, which is promising as this is the first targeted therapy to demonstrate activity in this patient population. Adverse events led to 15 patients discontinuing treatment in both patient groups, most commonly because of peripheral oedema and skin-related toxicity. Other adverse events reported included diarrhoea, dehydration, malaise and small intestinal perforation.