MAP2K1 and neoplasm: Similar pharmacodynamic effects of target pathway inhibition, i.e. a decrease in pERK levels in peripheral blood mononuclear cells, malignant cells, and/or paired tumor biopsies, have been reported with other MEK1/2 inhibitors, including trametinib [37], selumetinib (79 % geometric mean pERK reduction in paired tumor biopsies [19, 22]), ARRY-424704 [47], and RO4987655 [39], and with the dual Raf/MEK inhibitor RO5126766 [48], although no correlations with response have been reported.