Trametinib is a reversible and specific inhibitor of mitogen-activated protein kinase kinases MEK1 and MEK2 which are involved in a RAS/RAF/MEK/ERK signaling pathway and control cell growth, survival, and differentiation. By inhibiting MEK1 and MEK2 trametinib blocks dual phosphorylation of ERK1/2 and stops cell cycling. In addition, trametinib blocks BRAF pathway in the cells with BRAF V600E mutations. Trametinib (as a single agent and in combination with dabrafenib) is approved for the treatment of unresectable or metastatic melanoma with BRAF V600E or V600K mutations.