We carried out a retrospective analysis of efficacy and safety in four patients with BRAF K601E and one patient with L597Q mutation-positive metastatic melanoma treated with the MEK inhibitor trametinib. Three patients achieved a RECIST partial response, including the patient with an L597Q mutation...Trametinib has antitumour activity in patients with BRAF K601E and L597Q mutation-positive metastatic melanoma.