Kinase experiment:

MEK1 kinase activity is determined using mERK2 K52A T183A as the substrate. Recombinant MEK1 enzyme (5 nM) is first activated by 0.02 unit or 1.5 nM of RAF1 in the presence of 25 mM HEPES (pH 7.8), 1 mM MgCl2, 50 mM NaCl, 0.2 mM EDTA, and 50 μM ATP for 30 min at 25℃. The reactions are initiated by adding 2 μM of mERK2 K52A T183A and 2.5 μCi [γ-33P]ATP in a total volume of 20 μL. The MEK2 kinase activity is determined similarly except that activation by RAF1 is not needed and 11 nM of MEK2 enzyme (active) are used in the assays. Kinase profiling is performed. The Z'-LYTE biochemical assay is used. Refametinib is assayed in quadruplicate at 10 μM against 205 kinases[1].

Cell experiment:

For anchorage-dependent growth inhibition experiments, A375, SK-Mel-28, A431, Colo205, HT-29, MDA-MB-231, and BxPC3 cell lines are plated in white 384-well plates at 1,000/20 μL/well or white 96-well microplates at 4,000/100 μL/well. After 24-h incubation at 37℃, 5% CO2, and 100% humidity, Refametinib is incubated for 48 h at 37℃ and assayed using CellTiter-Glo. For the 96-well anchorage-independent growth assay, wells of an “ultralow binding” plate are filled with 60 μL of a 0.15% agarose solution in complete RPMI 1640. Then, 60 μL of complete RPMI 1640 containing 9,000 cells in 0.15% agarose are added per well. After 24 h, 60 μL of a 3× drug solution in agarose-free complete RPMI 1640 are added. After 7 d, 36 μL of 6× MTS reagent are added per well. After 2 h at 37℃, absorbance at 490 nm is determined on the M5 plate reader. Nonlinear curve fitting is performed using GraphPad Prism 4[1].

Animal experiment:

Mice[1]Female athymic nude mice are used for all the efficacy studies except for the Colo205 study 2, which used male mice. Mice are injected s.c. in the flank with 1×106 tumor cells (Colo205 and A431) or ~1 mm3 tumor fragments (A375 and HT-29). Tumor volumes are monitored by caliper measurements. For efficacy analysis, treatment is initiated when tumors are 80 to 185 mm3. Refametinib (25 and 50 mg/kg/d) is administered by oral gavage once daily or twice daily for 14 d or once every 2 d for 14 doses[1].

Refametinib is a selective and orally available allosteric inhibitor of MEK 1 and MEK 2 with IC50 values of 19nM and 47nM, respectively [1].

Refametinib is a non–ATP-competitive inhibitor of MEK1/2. It inhibits MEK activity in an in vitro assay with IC50 values of 19nM and 47nM for MEK1 and MEK2, respectively. X-ray shows refametinib binds to an allosteric site of MEK. It does not affect ATP binding but precludes binding to the substrate ERK, thus preventing ERK phosphorylation. Refametinib inhibits MEK with EC50 values ranging from 2.5nM to 15.8nM in a variety of human cancer cells including A375, Colo205, HT-29 and MDA-MB-231. In addition, in the cancer cell lines harboring V600E BRAF mutant, refametinib suppresses cell growth with GI50 values ranging from 67nM to 89nM. Furthermore, in the human melanoma A375 tumor xenograft model, treatment of refametinib causes obvious tumor growth delay and regression. Refametinib also shows tumor growth inhibition in the xenograft model of human Colo205 tumor [1].

References:
[1] Iverson C, Larson G, Lai C, et al. RDEA119/BAY 869766: a potent, selective, allosteric inhibitor of MEK1/2 for the treatment of cancer. Cancer research, 2009, 69(17): 6839-6847.