In vitro activity: RO4987655 (also known as CH-4987655) is a novel, orally bioavailable and specific small molecule inhibitor of MEK kinase with an IC50 of 5.2 nM for MEK1/MEK2. It targets the mitogen-activated protein kinase kinase 1 (MAP2K1/MEK1) with potential antineoplastic activity. It potently inhibits mitogen-activated protein kinase signaling pathway activation and tumor cell growth with an in vitro IC50 of 5.2 nmol/L for inhibition of MEK1/2. Single-agent oral administration of CH4987655 resulted in complete tumor regressions in xenograft models. In clinical trials, doses of 0.5, 1, 2, 3, and 4 mg were safe and well tolerated. No clinically significant safety event was observed.

Kinase Assay: RO4987655 (also known as CH-4987655) is a novel, orally bioavailable and specific small molecule inhibitor of MEK kinase with an IC50 of 5.2 nM for MEK1/MEK2. It targets the mitogen-activated protein kinase kinase 1 (MAP2K1/MEK1) with potential antineoplastic activity. It potently inhibits mitogen-activated protein kinase signaling pathway activation and tumor cell growth with an in vitro IC50 of 5.2 nmol/L for inhibition of MEK1/2.

Cell Assay: The human lung adenocarcinoma cell line NCI-H2122 are maintained in the designated media and indicated concentrations of heat-inactivated fetal bovine serum and L-glutamine. Cells are grown at 37°C in an atmosphere of 5%CO2. Cells are treated with various concentrations of RO4987655 (0.00001, 0.001, 0.1, and 10 μM) for 72 h in 96-well plates and viable cells were quantified with Cell Counting Kit-8