An orally available small molecule inhibitor of mitogen-activated protein kinase kinase (MAP2K; MAPK/ERK kinase; MEK), with potential antineoplastic activity. Upon administration, MEK inhibitor SHR 7390 selectively binds to and inhibits the activity of MEK. This prevents the activation of MEK-dependent effector proteins, which results in the inhibition of growth factor-mediated cell signaling and tumor cell proliferation. MEK, a dual-specificity threonine/tyrosine kinase family that plays a key role in the activation of the RAS/RAF/MEK/ERK signaling pathway, is frequently upregulated in a variety of tumor cell types.