MK-5108

MK-5108 inhibits Aurora-A activity in an ATP-competitive manner. MK-5108 shows robust selectivity against the other family kinases Aurora-B (220-fold) and Aurora-C (190-fold) in the biochemical assay. MK-5108 also reveals high selectivity for Aurora-A over other protein kinases. MK-5108 inhibits only one kinase (TrkA) with <100-fold selectivity. MK-5108 may be more Aurora-A selective than MLN8054. Consistent with the induction of pHH3-positive cells, MK-5108 induces accumulation of cells in the G2-M phase. MK-5108 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] MK-5108 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 MK-5108 in LEIO285 increases the proportion of cells in G2/M at 48 and 72 hours post-treatment. MK-5108 significant increases in Caspase 3/7 activity when compared to DMSO-treated control cultures at both time points. In LEIO505 cells, MK-5108 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 MK-5108 at 8 mg/kg and 16 mg/kg are 1.7 μM and 4.4 μM, respectively. MK-5108 treatment results in the induction of pHH3 in tumor and skin tissues, which starts at 2 hours and reachs a maximum at 4 hours. MK-5108 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. MK-5108 is well tolerated at both doses, with minimal reduction in body weight. MK-5108 also exhibits significant antitumor activity through intermittent dosing in nude rats bearing SW48 tumors, MK-5108 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]