Mirdametinib (PD-0325901) is a novel, potent, selective, orally bioavailable and non ATP-competitive inhibitor of the mitogen-activated protein kinase MEK with IC50 of 0.33 nM in cell-free assays, roughly 500-fold more potent than CI-1040 on phosphorylation of ERK1 and ERK2.

Cobimetinib racemate is the racemic mixture of Cobimetinib (GDC-0973, RG7420; XL-518; Cotellic), which is a novel, orally bioavailable, highly potent and selective small-molecule MEK1 inhibitor with antitumor activity.