PD0325901 is a small molecule targeting mitogen-activated protein kinase (MaPK/ERK kinase or MEK) with potential antineoplastic activity. PD0325901, a derivative of MEK inhibitor CI-1040, selectively binds to and inhibits MEK, which may result in the inhibition of the phosphorylation and activation of MaPK/ERK and the inhibition of tumor cell proliferation1,2. along with the aLK5 inhibitor SB431542, PD0325901 has also been shown to increase the efficiency of reprogramming human primary fibroblasts into induced pluripotent stem (iPS) cells3. 2mg.