Selumetinib (AZD6244, ARRY-142886) is a potent, highly selective MEK inhibitor with IC50 of 14 nM for MEK1 and Kd value of 530 nM for MEK2. It also inhibits ERK1/2 phosphorylation with IC50 of 10 nM, no inhibition to p38α, MKK6, EGFR, ErbB2, ERK2, B-Raf, etc. Selumetinib suppresses cell proliferation, migration and trigger apoptosis. Phase 3.