NF1 and neoplasm: This pathway is hyperactivated in NF1-related tumours, and inhibition of MAPK kinase (MEK) was effective at controlling tumour size in a mouse model of NF1.51,52 Unlike other therapeutic strategies tested so far, MEK inhibition (using selumetinib) has yielded unprecedented results in the clinic for pNF.53 In fact, almost all selumetinib-treated patients showed no tumour progression while being treated with the drug, with 72% showing a partial response and 24% showing stable disease in the SPRINT trial (NCT01362803).