NCIt definition : An agent that inhibits both mitogen-activated protein kinase kinases 1 and 2 (MEK1
and MEK2), substrates of Raf and phosphorylates extracellular signal-regulated kinases
1 and 2 (ERK1 and ERK2), preventing phosphorylation and activation of the Mitogen-Activated
Protein Kinase (MAPK) pathways, involved with signal transduction pathways and tumor
proliferation.;