As a key member of the Ras/Raf/MEK/ERK mitogen-activated protein kinase signaling pathway(ERK pathway),which play critical roles in regulation of diverse cellular events,MEK has been regarded as one of the most promising targets for antitumor,anti-inflammatory or antiviral agents1.Twelve MEK inhibitors are currently at some stage of clinical evaluation for the treatment of cancer.The most advanced MEK inhibitor GSK1120212(Trametinib)has been approved by FDA for the treatment of melanoma in May 2013.