AMG-900

AMG 900 is a novel class of ATP-competitive phthalazinamine small molecule inhibitors of aurora kinases. In HeLa cells, AMG 900 inhibits autophosphorylation of aurora-A and -B as well as phosphorylation of histone H3 on Ser, a proximal substrate of aurora-B. The predominant cellular response of tumor cells to AMG 900 treatment is aborted cell division without a prolonged mitotic arrest, which ultimately results in cell death. AMG 900 inhibits the proliferation of 26 tumor cell lines, including cell lines resistant and to other aurora kinase inhibitors (AZD1152, MK-0457, and PHA-739358), at low nanomolar concentrations (about 2- 3 nM). Furthermore, AMG 900 is active in an AZD1152-resistant HCT116 variant cell line that harbors an aurora-B mutation (W221L). ^[1]

Tumor cells are treated with AMG 900 for 48 hours, washed twice with complete media, and cells are replated at a density of 5000 cells per well in drug-free complete media. Cells are grown until the DMSO control wells are confluent. Cells are stained with crystal violet dye, washed with distilled water, and imaged using a digital scanner.

Oral administration of AMG 900 blocks the phosphorylation of histone H3 in a dose-dependent manner and significantly inhibited the growth of HCT116 tumor xenografts. AMG 900 is broadly active in multiple xenograft models, including 3 multidrugresistant xenograft models, representing 5 tumor types. ^[1] AMG 900 exhibits a low-to-moderate clearance and a small volume of distribution. Its terminal elimination half-life ranged from 0.6 to 2.4 hours. AMG 900 is well-absorbed in fasted animals with an oral bioavailability of 31% to 107%. Food intake has an effect on rate (rats) or extent (dogs) of AMG 900 oral absorption. The clearance and volume of distribution at steady state in humans are predicted to be 27.3 mL/h/kg and 93.9 mL/kg, respectively. AMG 900 exhibits acceptable PK properties in preclinical species and is predicted to have low clearance in humans. ^[2]