In vitro activity: PD318088 is a small-molecule inhibitor of MEK1/2, which is an analog of PD184352, suggesting it might have substantial anti-proliferative activity against cancer cells, although no functional study of PD318088 is currently available. PD318088 binds simultaneously with ATP in a region of the MEK1 active site that is adjacent to the ATP-binding site. Formation of the ternary complexes with PD318088 and MgATP results in moderate increases (to 140 nM) for the Kd monomer-dimer for both MEK1 and MEK2. The binding of PD318088 and MgATP to MEK1 also abolishes the formation of tetramers and higher-order aggregates. PD318088 and MgATP together increase the dimerization disassociation constant for MEK1 and MEK2 slightly from ~75 nM to ~140 nM, suggesting that the mechanism of inhibition for PD318088 is probably a result of localized conformational changes in the active site and not a global change in the overall structure.

Kinase Assay: PD318088 and MgATP results in moderate increases (to 140 nM) for the Kd monomer-dimer for both MEK1 and MEK2. PD318088 and MgATP together increase the dimerization disassociation constant for MEK1 and MEK2 slightly from ~75 nM to ~140 nM.