U0126 is a selective MAPK and ERK inhibitor, displaying a preference for MEK1 and MEK2. The IC50 value for MEK1 is 72nM and MEK2 is 58nM. It is known that U-0126 binds to MAPK noncompetitive manner compared to ATP. Studies suggest that U-0126 antagonizes the transcription of AP-1, via the inhibition of MEK. In addition, U-0126 has been observed to inhibit promoters containing an AP-1 response element. Conversely, U-0126 has no effect on promoters that lack an AP-1 response group. U-0126 is also useful in neuronal studies in mice since it displays inhibitory effects against oxidative stress.