MK-5108

MK-5108 inhibits Aurora-A activity in an ATP-competitive manner. This compound shows robust selectivity against the other family kinases Aurora-B (220-fold) and Aurora-C (190-fold) in the biochemical assay. It also reveals high selectivity for Aurora-A over other protein kinases. The compound inhibits only one kinase (TrkA) with <100-fold selectivity. It may be more Aurora-A selective than MLN8054. Consistent with the induction of pHH3-positive cells, this chemical induces accumulation of cells in the G2-M phase. It inhibits the proliferation of tumor cells including HCC1143, AU565, MCF-7, HCC1806 and CAL85-1 with an IC50 of 0.42 μM, 0.45 μM, 0.52 μM, 0.56μM and 0.74 μM, respectively. ^[1] This compound decreases cell viability in a dose-dependent fashion in all three cell lines including LEIO285, LEIO505 and SK-LSM1 cells with an IC50 of approximately 100 nM. Incubation with it in LEIO285 increases the proportion of cells in G2/M at 48 and 72 hours post-treatment. The compound significant increases in Caspase 3/7 activity when compared to DMSO-treated control cultures at both time points. In LEIO505 cells, it leads to more cells accumulating at G2/M phases at 24 hours but not 48 hours or 72 hours.  ^[2]

HeLa-S3 cells are synchronized at the G1-S phase boundary by double thymidine block with 2 mM thymidine. Cells are washed and seeded to 96-well cell culture plates. After 4 hours, an equal volume of medium containing MK-5108 is added to each well. Nocodazole (300 nM) is used as a 100% control. The cells are fixed overnight with cold methanol 12 hours after seeding. Then, the cells are stained with rabbit anti-phospho-histone H3 Ser28 antibody and then with anti-rabbit IgG-Cy5. Total nuclei are stained with 10 mg/mL 4^′,6-diamidino-2-phenylindole. Immunostained images are acquired using the IN Cell Analyzer1000 with ×10 objective lens. After acquisition of images, data are analyzed. The %pHH3-positive index is determined by measuring the %pHH3-positive cell counts per total nuclei counts for each sample, then by normalizing with respect to nocodazole-treated cells.

MK-5108 induces pHH3-positive cells at doses of 16 mg/kg and 32 mg/kg. Plasma concentration of this compound at 8 mg/kg and 16 mg/kg are 1.7 μM and 4.4 μM, respectively. This compound treatment results in the induction of pHH3 in tumor and skin tissues, which starts at 2 hours and reachs a maximum at 4 hours. This chemical treatments at 15 mg/kg and 30 mg/kg results in significant tumor growth inhibition with the change in mean tumor volume for the treatment group as a percentage of the mean change in the control group (%T/C) of 10% and −6% at day 11, and 17% and 5% at day 18, respectively. It is well tolerated at both doses, with minimal reduction in body weight. This compound also exhibits significant antitumor activity through intermittent dosing in nude rats bearing SW48 tumors, it at 15 mg/kg and 45 mg/kg causes dose-dependent tumor growth inhibition with a %T/C of 35% and 7% at day 10, and 58% and 32% at day 27, respectively. ^[1]