In vitro activity: GW5074 is a potent and specific inhibitor of c-Raf with IC50 of 9 nM and has no effect of MKK6, MKK7, p38 MAP kinase and cdks in vitro. However, treatment of neuronal cultures with GW5074 permits accumulation of activating modifications on c-Raf and also B-Raf. The inhibition of LK-induced apoptosis by GW5074 in cerebellar granule neurons is not MEK-ERK-dependent. GW5074 delays down-regulation of Akt activity but inhibits apoptosis by an Akt-independent mechanism. GW5074 affects Ras, nuclear factor-kappa B and c-jun. GW5074 inhibits cell death caused by neurotoxins in granule cells and other neuronal types.

Kinase Assay: In general, in vitro kinase assays are performed using purified kinase and synthetic substrates under standard conditions using the Kinase Profiling service of Upstate Biotechnology. Briefly, for each assay 5–10 mU of purified kinase is used. For GSK3β, cdk1, cdk2, cdk3, cdk5, the kinase is incubated with 1 μM GW5074 in a buffer containing 8 mM MOPS, pH 7.2, 0.2 mM EDTA, 10 mM magnesium acetate and [c- 33P-ATP] for 40 min at room temperature. Kinase activity is quantified by measuring 33P incorporation by spotting an aliquot on P30 filters, washing in 50 mM phosphoric acid and scintillation counting. The buffer composition for c-Raf, JNK1, JNK2, JNK3, MEK1, MKK6, MKK7 is 50 mM Tris pH 7.5, 0.1 mM EGTA, 10 mM magnesium acetate and [c- 33P-ATP]. The peptide substrates used are as follows: For c-Raf, 0.66 mg/mL MBP; for cdks, 0.1 mg/mL histone H1; for JNKs, 3 μM ATF2; for MEK1, 1 μM MAPK2; for MKK6, 1 μM of SAPK2a and for MKK7, 2 μM JNK1α.

Cell Assay: HCA is diluted from 100-fold concentrated solutions that are adjusted to pH 7.5. To evaluate the effects of GW5074 on HCA-induced cytotoxicity, GW5074 is added at the time cortical neurons are exposed to HCA. Viability is assessed 24 h later.

[1] Chin PC, et al. J Neurochem, 2004, 90(3), 595-608.; [2] Yue X, et al. Eur J Pharmacol, 2006, 540(1-3), 57-59.