PD0325901 is a selective, cell permeable inhibitor of the MEK/ERK pathway that inhibits the activation and downstream signaling of MEK. It is an extremely potent inhibitor, suppressing the phosphorylation of ERK in C26 cells at very low concentrations (IC₅₀ = 0.33 nM) (Bain et al., Barrett et al.).

MAINTENANCE AND SELF-RENEWAL
· Maintains undifferentiated mouse embryonic stem (ES) cells, in combination with CHIR99021, in the absence of LIF (Ying et al.).
· Allows derivation and maintenance of rat ES cells (Buehr et al., Li P et al.).

REPROGRAMMING
· Add at the later stages of reprogramming to select for and expand fully reprogrammed mouse induced pluripotent (iPS) cells (Shi et al., Silva et al.).
· Increases the efficiency of reprogramming human somatic cells to iPS cells, in combination with SB431542 and Thiazovivin (Lin et al.).
· Promotes reprogramming of human somatic cells to iPS cells using only a single factor, OCT4 (Zhu et al.).
· Generates mouse-like or “ground state” iPS cells from human and rat somatic cells, in combination with CHIR99021 and A83-01 (Li W et al.).