MEK and the inhibitors: from bench to bedside

Abstract

Four distinct MAP kinase signaling pathways involving 7 MEK enzymes have been identified. MEK1 and MEK2 are the prototype members of MEK family proteins. Several MEK inhibitors are in clinical trials. Trametinib is being evaluated by FDA for the treatment of metastatic melanoma with BRAF V600 mutation. Selumetinib has been studied in combination with docetaxel in phase II randomized trial in previously treated patients with advanced lung cancer. Selumetinib group had better response rate and progression-free survival. This review also summarized new MEK inhibitors in clinical development, including pimasertib, refametinib, PD-0325901, TAK733, MEK162 (ARRY 438162), RO5126766, WX-554, RO4987655 (CH4987655), GDC-0973 (XL518), and AZD8330.

Figure 1

MEK proteins and their signaling pathways. In human, four distinct MAP kinase signaling pathways involving 7 MEK enzymes have been identified. The corresponding MEK enyzmes and their associated signaling pathways are shown in the diagram.

Figure 2

The structures of 7 MEK proteins. All 7 MEK proteins display a similar structural organization consisting of an amino-terminal domain, a kinase domain, and the carboxyl-terminal domain. MEKs share extensive homology in their kinase domain while the amino- and carboxy-termini are more diverse.

Figure 3

The chemical structures of 9 MEK inhibitors in clinical development. Nine MEK inhibitors are shown in the diagram. Among them, trametinib is being evaluated by FDA for treatment of advanced metastatic melanoma.