Definition

The hydrochloride salt form of pimasertib, an orally bioavailable small-molecule inhibitor of mitogen activated protein kinase kinases 1 (MEK1) and 2 (MEK2), with potential antineoplastic activity. Upon oral administration, pimasertib selectively binds to and inhibits the activity of MEK1 and 2, thereby preventing the activation of MEK1/2-dependent effector proteins and transcription factors. This results in the inhibition of growth factor-mediated cell signaling and tumor cell proliferation. MEK1/2 (MAP2K1/K2) are dual-specificity threonine/tyrosine kinases that play key roles in the activation of the RAS/RAF/MEK/ERK pathway and are often upregulated in a variety of tumor cell types.