ERK5-IN-4 (compound 34b) is a powerful and specific inhibitor of extracellular signal-related kinase 5 (ERK5) activity. It effectively inhibits both the full-length ERK5 and the truncated ERK5 (ERK5 ΔTAD) kinase activity in HEK293 cells with IC50 values of 77 nM and 300 nM, respectively [1].

ERK5-IN-4 (compound 34b) is selective against MAP3K, p38 (IC 50 >30 μM) and BRD4 (IC 50 >20 μM), in contrast to many reported ERK5 inhibitors [1]. ERK5-IN-4 (0-100 μM; 72 h) suppresses ERK5 kinase activity in HEK293 cells and (0-1 μM; 72 h) induces paradoxical activation of ERK5 transcriptional activity, thus resulting in C-terminal transcriptional activation domain (TAD) separated from the nuclear localization sequence (NLS) and results ERK5 nuclear translocation [1]. ERK5-IN-4 inhibits cancer cells with GI 50 of 19.6 μM (HEK293), 22.3 μM (A498), 25 μM (SJSA-1), 26.6 μM (MDA-MB-231) following a 72 h incubation [1]. ERK5-IN-4 exhibits kinome selectivity K d of 1.2 μM, 0.29 μM, 0.046 μM, 0.061 μM, 0.18 μM, 0.38 μM, 1.3 μM, 0.42 μM, 0.22 μM, 2.8 μM against ABL1-nonphosphorylated, AURKA, CSF1R, DCAMKL1 (DCLK1), ERK5 (MAPK7), FGFR1, JAK3 (JH1domain-catalytic), KIT, LRRK2, MEK5 (MAP2K5) [1]. Western Blot Analysis [1] Cell Line: HeLa cells Concentration: 0.01, 0.03, 0.1, 0.3, 1, 3 μM Incubation Time: 1 h Result: Resulted upper phospho-ERK5 band with EGF stimulation and inhibition.

ERK5-IN-4 (compound 34b) (p.o.; 10 mg/kg) has low clearance and an oral bioavailability of 42% in the mouse [1]. Animal Model: Pharmacokinetic Parameters for ERK5-IN-4 [1] Dosage: Administration: Result: Route Dose (mg/kg) Cl (mL/min/kg) V d (L/kg) t 1/2 (min) BA (%) i.v. or p.o. 10 14 0.6 80 42