PD 0325901 is a potent and selective MEK1 and MEK2 inhibitor. It is reported to inhibit cell proliferation and arrest cell cycle at the G0/G1 phase of thyroid cancer cells. PD 0325901 can be used with CHIR99021 to reprogram somatic cells into iPS cells and promote cell self-renewal. Studies have shown that in comparison to the CI-1040 MEK inhibitor that PD 0325901 has a greater potency of inhibition, longer duration, greater solubility, improved bioavailability, and increased metabolic stability.